Research & Scholarship
Current Research and Scholarly Interests
Each cell of our bodies and of all multicellular organisms contains several members of the tetraspanin family. Tetraspanins provide a network that facilitates membranal interactions, hence their involvement in multiple physiological interactions. Our studies focus on CD81, which is required for cell fusion and cell-cell interactions, functions that have been subverted by major human pathogens, including hepatitis C virus and Plasmodium. Current research is aimed at understanding the role of CD81 in metastasis.
Clinical and Pathologic Studies in Non-Hodgkin's Lymphoma and Hodgkin's Disease
The purpose of this study is to characterize the molecular and cell biology of the tumor cells in lymphoma.
Independent Studies (13)
- Directed Reading in Cancer Biology
CBIO 299 (Aut, Win, Spr)
- Directed Reading in Immunology
IMMUNOL 299 (Aut, Win, Spr, Sum)
- Directed Reading in Medicine
MED 299 (Aut, Win, Spr, Sum)
- Early Clinical Experience in Immunology
IMMUNOL 280 (Aut, Win, Spr, Sum)
- Early Clinical Experience in Medicine
MED 280 (Aut, Win, Spr, Sum)
- Graduate Research
CBIO 399 (Aut, Win, Spr)
- Graduate Research
IMMUNOL 399 (Aut, Win, Spr, Sum)
- Graduate Research
MED 399 (Aut, Win, Spr, Sum)
- Medical Scholars Research
MED 370 (Aut, Win, Spr, Sum)
- Out-of-Department Advanced Research Laboratory in Experimental Biology
BIO 199X (Aut, Win, Spr, Sum)
- Teaching in Immunology
IMMUNOL 290 (Aut, Win, Spr, Sum)
- Undergraduate Research
IMMUNOL 199 (Aut, Win, Spr, Sum)
- Undergraduate Research
MED 199 (Aut, Win, Spr, Sum)
- Directed Reading in Cancer Biology
CD81 and hepatitis C virus (HCV) infection.
2014; 6 (2): 535-572
Hepatitis C Virus (HCV) infection is a global public health problem affecting over 160 million individuals worldwide. Its symptoms include chronic hepatitis, liver cirrhosis and hepatocellular carcinoma. HCV is an enveloped RNA virus mainly targeting liver cells and for which the initiation of infection occurs through a complex multistep process involving a series of specific cellular entry factors. This process is likely mediated through the formation of a tightly orchestrated complex of HCV entry factors at the plasma membrane. Among HCV entry factors, the tetraspanin CD81 is one of the best characterized and it is undoubtedly a key player in the HCV lifecycle. In this review, we detail the current knowledge on the involvement of CD81 in the HCV lifecycle, as well as in the immune response to HCV infection.
View details for DOI 10.3390/v6020535
View details for PubMedID 24509809
Self-antigen recognition by follicular lymphoma B-cell receptors
2012; 120 (20): 4182-4190
Follicular lymphoma is a monoclonal B-cell malignancy with each patient's tumor expressing a unique cell surface immunoglobulin (Ig), or B-cell receptor (BCR), that can potentially recognize antigens and/or transduce signals into the tumor cell. Here we evaluated the reactivity of tumor derived Igs for human tissue antigens. Self-reactivity was observed in 26% of tumor Igs (25 of 98). For one follicular lymphoma patient, the recognized self-antigen was identified as myoferlin. This patient's tumor cells bound recombinant myoferlin in proportion to their level of BCR expression, and the binding to myoferlin was preserved despite ongoing somatic hypermutation of Ig variable regions. Furthermore, BCR-mediated signaling was induced after culture of tumor cells with myoferlin. These results suggest that antigen stimulation may provide survival signals to tumor cells and that there is a selective pressure to preserve antigen recognition as the tumor evolves.
View details for DOI 10.1182/blood-2012-05-427534
View details for Web of Science ID 000311637400013
View details for PubMedID 23024238
A vaccine directed to B cells and produced by cell-free protein synthesis generates potent antilymphoma immunity
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2012; 109 (36): 14526-14531
Clinical studies of idiotype (Id) vaccination in patients with lymphoma have established a correlation between the induced anti-Id antibody responses and favorable clinical outcomes. To streamline the production of an Id vaccine, we engineered a small diabody (Db) molecule containing both a B-cell-targeting moiety (anti-CD19) and a lymphoma Id. This molecule (?CD19-Id) was designed to penetrate lymph nodes and bind to noncognate B cells to form an antigen presentation array. Indeed, the ?CD19-Id molecule accumulated on B cells in vivo after s.c. administration. These noncognate B cells, decorated with the diabody, could then stimulate the more rare Id-specific B cells. Peptide epitopes present in the diabody linker augmented the response by activating CD4(+) helper T cells. Consequently, the ?CD19-Id molecule induced a robust Id-specific antibody response and protected animals from tumor challenge. Such diabodies are produced in a cell-free protein expression system within hours of amplification of the specific Ig genes from the B-cell tumor. This customized product can now be available to vaccinate patients before they receive other, potentially immunosuppressive, therapies.
View details for DOI 10.1073/pnas.1211018109
View details for Web of Science ID 000308912600051
View details for PubMedID 22875703
The CD19/CD81 complex physically interacts with CD38 but is not required to induce proliferation in mouse B lymphocytes
2012; 137 (1): 48-55
In B lymphocytes, the cell surface receptor CD38 is involved in apoptosis of immature B cells, proliferation and differentiation of mature B cells. Although CD38 has been establish as a receptor, its signaling has been only partially characterized. As a result of the lack of signaling motifs in the cytoplasmic domain, CD38 must use a co-receptor to induce signaling within the cell. Accordingly, CD38 has been associated with different receptors such as the T-cell receptor/CD3 complex on T cells, CD16 on natural killer cells and MHC class II molecules on monocytes. The CD19/CD81 complex has been proposed as a co-receptor for CD38 in human B lymphocytes, but little or no characterization has been performed in mice. In this study the contribution of the CD19/CD81 complex in murine CD38 signaling was evaluated. Proliferation assays were performed using CD19(-/-) or CD81(-/-) deficient mice; CFSE-labeled B lymphocytes from wild-type mice and CD19(-/-) , CD81(-/-) and CD38(-/-) deficient mice were stimulated with agonistic antibodies against CD38. Immunoprecipitation and immunofluorescence were also performed to detect protein-protein interactions. Our results indicate that the CD19/CD81 complex interacts with CD38 but this interaction is not required to induce proliferation in mouse B lymphocytes, suggesting that other receptors may contribute to the proliferation induced by CD38 in B lymphocytes.
View details for DOI 10.1111/j.1365-2567.2012.03602.x
View details for Web of Science ID 000307074200005
View details for PubMedID 22564057
Complementary costimulation of human T-cell subpopulations by cluster of differentiation 28 (CD28) and CD81
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2012; 109 (5): 1613-1618
Cluster of differentiation 81 (CD81) is a widely expressed tetraspanin molecule that physically associates with CD4 and CD8 on the surface of human T cells. Coengagement of CD81 and CD3 results in the activation and proliferation of T cells. CD81 also costimulated mouse T cells that lack CD28, suggesting either a redundant or a different mechanism of action. Here we show that CD81 and CD28 have a preference for different subsets of T cells: Primary human naïve T cells are better costimulated by CD81, whereas the memory T-cell subsets and Tregs are better costimulated by CD28. The more efficient activation of naïve T cells by CD81 was due to prolonged signal transduction compared with that by CD28. We found that IL-6 played a role in the activation of the naïve T-cell subset by CD81. Combined costimulation through both CD28 and CD81 resulted in an additive effect on T-cell activation. Thus, these two costimulatory molecules complement each other both in the strength of signal transduction and in T-cell subset inclusions. Costimulation via CD81 might be useful for expansion of T cells for adoptive immunotherapy to allow the inclusion of naïve T cells with their broad repertoire.
View details for DOI 10.1073/pnas.1121307109
View details for Web of Science ID 000299731400056
View details for PubMedID 22307619
Escherichia coli-based production of a tumor idiotype antibody fragment - tetanus toxin fragment C fusion protein vaccine for B cell lymphoma
PROTEIN EXPRESSION AND PURIFICATION
2011; 75 (1): 15-20
The unique immunoglobulin idiotype expressed on the surface of B lymphoma cells can be used as an effective antigen in tumor-specific vaccines when fused to immunostimulatory proteins and cytokines. A DNA vaccine encoding for an idiotype antibody single chain Fv (scFv) fragment fused to the Tetanus Toxin Fragment C (TTFrC) has been shown to induce protective anti-tumor responses. Protein-based strategies may be more desirable since they provide greater control over dosage, duration of exposure, and in vivo distribution of the vaccine. However, production of fusion protein vaccines containing complex disulfide bonded idiotype antibodies and antibody-derived fragments is challenging. We use an Escherichia coli-based cell-free protein synthesis platform as well as high-level expression of E. coli inclusion bodies followed by refolding for the rapid generation of an antibody fragment - TTFrC fusion protein vaccine. Vaccine proteins produced using both methods were shown to elicit anti-tumor humoral responses as well as protect from tumor challenge in an established B cell lymphoma mouse model. The development of technologies for the rapid production of effective patient-specific tumor idiotype-based fusion protein vaccines provides opportunities for clinical application.
View details for DOI 10.1016/j.pep.2010.09.005
View details for Web of Science ID 000284452600002
View details for PubMedID 20851769
CD81 protein is expressed at high levels in normal germinal center B cells and in subtypes of human lymphomas
2010; 41 (2): 271-280
CD81 is a tetraspanin cell surface protein that regulates CD19 expression in B lymphocytes and enables hepatitis C virus infection of human cells. Immunohistologic analysis in normal hematopoietic tissue showed strong staining for CD81 in normal germinal center B cells, a cell type in which its increased expression has not been previously recognized. High-dimensional flow cytometry analysis of normal hematopoietic tissue confirmed that among B- and T-cell subsets, germinal center B cells showed the highest level of CD81 expression. In more than 800 neoplastic tissue samples, its expression was also found in most non-Hodgkin lymphomas. Staining for CD81 was rarely seen in multiple myeloma, Hodgkin lymphoma, or myeloid leukemia. In hierarchical cluster analysis of diffuse large B-cell lymphoma, staining for CD81 was most similar to other germinal center B cell-associated markers, particularly LMO2. By flow cytometry, CD81 was expressed in diffuse large B-cell lymphoma cells independent of the presence or absence of CD10, another germinal center B-cell marker. The detection of CD81 in routine biopsy samples and its differential expression in lymphoma subtypes, particularly diffuse large B-cell lymphoma, warrant further study to assess CD81 expression and its role in the risk stratification of patients with diffuse large B-cell lymphoma.
View details for DOI 10.1016/j.humpath.2009.07.022
View details for Web of Science ID 000276493600015
View details for PubMedID 20004001
Cell-free production of Gaussia princeps luciferase - antibody fragment bioconjugates for ex vivo detection of tumor cells
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
2009; 390 (3): 971-976
Antibody fragments (scFvs) fused to luciferase reporter proteins have been used as highly sensitive optical imaging probes. Gaussia princeps luciferase (GLuc) is an attractive choice for a reporter protein because it is small and bright and does not require ATP to stimulate bioluminescence-producing reactions. Both GLuc and scFv proteins contain multiple disulfide bonds, and consequently the production of active and properly folded GLuc-scFv fusions is challenging. We therefore produced both proteins individually in active form, followed by covalent coupling to produce the intended conjugate. We used an Escherichia coli-based cell-free protein synthesis (CFPS) platform to produce GLuc and scFv proteins containing non-natural amino acids (nnAAs) for subsequent conjugation by azide-alkyne click chemistry. GLuc mutants with exposed alkyne reactive groups were produced by global replacement of methionine residues in CFPS. Antibody fragment scFvs contained a single exposed azide group using a scheme for site-specific incorporation of tyrosine analogs. Incorporation of tyrosine analogs at specific sites in proteins was performed using an engineered orthogonal tRNA-tRNA synthetase pair from an archaebacterium. The unique azide and alkyne side chains in GLuc and the antibody fragment scFv facilitated conjugation by click chemistry. GLuc-scFv conjugates were shown to differentiate between cells expressing a surface target of the scFv and cells that did not carry this marker.
View details for DOI 10.1016/j.bbrc.2009.10.087
View details for Web of Science ID 000272516700113
View details for PubMedID 19852937
Generation of CD8(+) T cell-mediated immunity against idiotype-negative lymphoma escapees
2009; 114 (20): 4477-4485
We investigated the ability of CpG-oligodeoxynucleotide to generate an anti-tumor CD8+ T-cell immune response and to synergize with passive antibody therapy. For these studies, we generated an antibody against the idiotype on the A20 B-cell lymphoma line. This antibody caused the regression of established tumors, but ultimately the tumors relapsed. The escaping surface IgG-negative tumor cells were resistant to both antibody-dependent cellular cytotoxicity and signaling-induced cell death. Addition of intratumoral CpG to antibody therapy cured large established tumors and prevented the occurrence of tumor escapees. The failure of the combination therapy in mice deficient for CD8+ T cells demonstrates the critical role of CD8+ T cells in tumor eradication. When mice were inoculated with 2 tumors and treated systemically with antibody followed by intratumoral CpG in just one tumor, both tumors regressed, indicating that a systemic immune response was generated. Although antibody therapy can eliminate tumor cells bearing the target antigen, it frequently selects for antigen loss variants. However, when a poly-specific T-cell response was generated against the tumor by intratumoral CpG, even large established tumors were cured. Such an immune response can prevent the emergence of antibody selected tumor escapees and provide long-lasting tumor protection.
View details for DOI 10.1182/blood-2009-05-223263
View details for Web of Science ID 000271727500020
View details for PubMedID 19762487
Enhanced B cell activation in the absence of CD81
2009; 21 (11): 1225-1237
CD81 is a component of the CD19/CD21 co-receptor complex in B cells. However, the role of CD81 in B cell activation has not been clearly elucidated. Here, we demonstrate that Cd81(-/-) B cells stimulated via their B cell receptor fluxed higher intracellular-free calcium ion along with increased phosphorylation of spleen tyrosine kinase and phospholipase gamma 2. Additionally, Cd81(-/-) B cells responded to toll like receptor 4 stimulation with increased nuclear factor-kappa B activation, cell proliferation and antibody secretion compared with wild-type B cells. Cd81(-/-) mice also mounted a significantly higher immune response to T-independent antigens than their wild-type counterparts. Finally, analysis of Cd81(-/-) B cells that were generated by bone marrow transplantation into Rag1(-/-) mice confirmed that the hyperactive phenotype is not dependent on the CD81-deficient environment. Taken together, these results indicate that CD81 plays a negative role in B cell activation in vitro and in vivo.
View details for DOI 10.1093/intimm/dxp090
View details for Web of Science ID 000271382200004
View details for PubMedID 19737782
Wiskott-Aldrich syndrome protein is an effector of Kit signaling
2009; 114 (14): 2900-2908
The pleiotropic receptor tyrosine kinase Kit can provide cytoskeletal signals that define cell shape, positioning, and migration, but the underlying mechanisms are less well understood. In this study, we provide evidence that Kit signals through Wiskott-Aldrich syndrome protein (WASP), the central hematopoietic actin nucleation-promoting factor and regulator of the cytoskeleton. Kit ligand (KL) stimulation resulted in transient tyrosine phosphorylation of WASP, as well as interacting proteins WASP-interacting protein and Arp2/3. KL-induced filopodia in bone marrow-derived mast cells (BMMCs) were significantly decreased in number and size in the absence of WASP. KL-dependent regulation of intracellular Ca(2+) levels was aberrant in WASP-deficient BMMCs. When BMMCs were derived from WASP-heterozygous female mice using KL as a growth factor, the cultures eventually developed from a mixture of WASP-positive and -negative populations into a homogenous WASP-positive culture derived from the WASP-positive progenitors. Thus, WASP expression conferred a selective advantage to the development of Kit-dependent hematopoiesis consistent with the selective advantage of WASP-positive hematopoietic cells observed in WAS-heterozygous female humans. Finally, KL-mediated gene expression in wild-type and WASP-deficient BMMCs was compared and revealed that approximately 30% of all Kit-induced changes were WASP dependent. The results indicate that Kit signaling through WASP is necessary for normal Kit-mediated filopodia formation, cell survival, and gene expression, and provide new insight into the mechanism in which WASP exerts a strong selective pressure in hematopoiesis.
View details for DOI 10.1182/blood-2009-01-200733
View details for Web of Science ID 000270387100013
View details for PubMedID 19643989
Engagement of CD81 induces ezrin tyrosine phosphorylation and its cellular redistribution with filamentous actin
JOURNAL OF CELL SCIENCE
2009; 122 (17): 3137-3144
CD81 is a tetraspanin family member involved in diverse cellular interactions in the immune and nervous systems and in cell fusion events. However, the mechanism of action of CD81 and of other tetraspanins has not been defined. We reasoned that identifying signaling molecules downstream of CD81 would provide mechanistic clues. We engaged CD81 on the surface of B-lymphocytes and identified the induced tyrosine-phosphorylated proteins by mass spectrometry. This analysis showed that the most prominent tyrosine phosphorylated protein was ezrin, an actin-binding protein and a member of the ezrin-radixin-moesin family. We also found that CD81 engagement induces spleen tyrosine kinase (Syk) and that Syk was involved in tyrosine phosphorylation of ezrin. After engagement of CD81, it colocalized with ezrin and F-actin, and this association was disrupted when Syk activation was blocked. Taken together, these studies suggest a model in which CD81 interfaces between the plasma membrane and the cytoskeleton by activating Syk, mobilizing ezrin, and recruiting F-actin to facilitate cytoskeletal reorganization and cell signaling. This mechanism might explain the pleiotropic effects induced in response to stimulation of cells by anti-CD81 antibodies or by the hepatitis C virus, which uses this molecule as its key receptor.
View details for DOI 10.1242/jcs.045658
View details for Web of Science ID 000269122000013
View details for PubMedID 19654214
Cell-free production of scFv fusion proteins: an efficient approach for personalized lymphoma vaccines
2007; 109 (8): 3393-3399
The unique immunoglobulin (Ig) idiotype on the surface of each B-cell lymphoma represents an ideal tumor-specific antigen for use as a therapeutic vaccine. We have used an Escherichia coli-based, cell-free protein-expression system to produce a vaccine within hours of cloning the Ig genes from a B-cell tumor. We demonstrated that a fusion protein consisting of an idiotypic single chain Fv antibody fragment (scFv) linked to a cytokine (GM-CSF) or to an immunostimulatory peptide was an effective lymphoma vaccine. These vaccines elicited humoral immune responses against the native Ig protein displayed on the surface of a tumor and protected mice against tumor challenge with efficacy equal to that of the conventional Ig produced in a mammalian cell and chemically coupled to keyhole limpet hemocyanin. The cell-free E coli system offers a platform for rapidly generating individualized vaccines, thereby allowing much more efficient application in the clinic.
View details for DOI 10.1182/blood-2006-07-030593
View details for Web of Science ID 000245658500047
View details for PubMedID 17164345
Building of the tetraspanin web: Distinct structural domains of CD81 function in different cellular compartments
MOLECULAR AND CELLULAR BIOLOGY
2006; 26 (4): 1373-1385
The tetraspanin web is composed of a network of tetraspanins and their partner proteins that facilitate cellular interactions and fusion events by an unknown mechanism. Our aim was to unravel the web partnership between the tetraspanin CD81 and CD19, a cell surface signaling molecule in B lymphocytes. We found that CD81 plays multiple roles in the processing, intracellular trafficking, and membrane functions of CD19. Surprisingly, these different roles are embodied in distinct CD81 domains, which function in the different cellular compartments: the N-terminal tail of CD81 has an effect on the glycosylation of CD19; the first transmembrane domain of CD81 is sufficient to support the exit of CD19 from the endoplasmic reticulum, although the large extracellular loop (LEL) of CD81 associates physically with CD19 early during biosynthesis; and finally, the TM2 and TM3 domains of CD81 play a role in the transmission of signals initiated upon engagement of the LEL. The participation of distinct CD81 domains in varied functions may explain the pleiotropic effects of CD81 within the tetraspanin web.
View details for DOI 10.1128/MCB.26.4.1373-1385.2006
View details for Web of Science ID 000235438200018
View details for PubMedID 16449649
Protein-protein interactions in the tetraspanin web
2005; 20: 218-224
Tetraspanins are evolutionarily conserved membrane proteins that tend to associate laterally with one another and to cluster dynamically with numerous partner proteins in membrane microdomains. Consequently, members of this family are involved in the coordination of intracellular and intercellular processes, including signal transduction; cell proliferation, adhesion, and migration; cell fusion; and host-parasite interactions.
View details for Web of Science ID 000230938100002
View details for PubMedID 16024509
Expression of the human germinal center-associated lymphoma (HGAL) protein, a new marker of germinal center B-cell derivation
2005; 105 (10): 3979-3986
We identified the human germinal center-associated lymphoma (HGAL) in gene-expression profiling studies of diffuse large B-cell lymphoma (DLBCL). The expression of HGAL correlated with survival in patients with DLBCL. The HGAL gene is the human homolog of M17, a mouse gene expressed specifically in normal germinal center (GC) B cells. We generated a monoclonal antibody against the HGAL protein and show that HGAL is expressed in the cytoplasm of GC lymphocytes and in lymphomas of GC derivation. Among 727 lymphomas tested by immunohistochemistry on tissue microarrays, HGAL staining was found in follicular lymphomas (103 of 107), Burkitt lymphomas (40 of 40), mediastinal large B lymphomas (7 of 8), and in DLBCLs (103 of 151). Most marginal zone lymphomas lacked HGAL staining. Lymphocyte-predominant Hodgkin lymphomas (12 of 17) and, surprisingly, classical Hodgkin lymphomas (78 of 107) were found to be positive. Hierarchical clustering of comparative immunohistologic results in DLBCLs demonstrates that the expression of HGAL is similar to 2 other GC-associated proteins, BCL6 and CD10, but different from 2 markers associated with a non-GC phenotype, MUM1/IRF4 and BCL2. The restricted expression and GC specificity of HGAL protein suggest that it may have an important role in the diagnosis of specific lymphomas, and, potentially in the identification of subtypes associated with different prognoses.
View details for DOI 10.1182/blood-2004-08-3112
View details for Web of Science ID 000229009000042
View details for PubMedID 15677569
Kinetics of HCV envelope proteins' interaction with CD81 large extracellular loop
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
2005; 328 (4): 1091-1100
We used BIAcore to analyze the kinetics of interactions between CD81 and hepatitis C virus (HCV) envelope proteins. We immobilized different forms of HCV envelope proteins (E1E2, E2, and E2(661)) on the sensor and monitored their interaction with injected fusion proteins of CD81 large extracellular loop (CD81LEL) and glutathione-S-transferase (CD81LEL-GST) or maltose binding protein (CD81LEL-MBP). The difference between the GST and MBP fusion proteins was their multimeric and monomeric forms, respectively. The association rate constants between CD81LEL-GST or CD81LEL-MBP and the E1E2, E2 or E2(661) HCV envelope proteins were similar. However, the dissociation rate constants of CD81LEL-MBP were higher than those of CD81LEL-GST. Interestingly, the dissociation rate constant of CD81LEL-GST from E1E2 was much lower than from E2 or E2(661). The interaction between both forms of the CD81LEL fusion proteins and the HCV envelope proteins best-fitted the "heterogeneous ligand" model. This model implies that two kinds of interactions occur between envelope proteins and CD81LEL: one is strong, the other is weak. It also implies that the heterogeneity is likely due to the HCV envelope proteins, which are known to form non-covalently linked heterodimers and disulfide-linked aggregate.
View details for DOI 10.1016/j.bbrc.2005.01.056
View details for Web of Science ID 000227233000039
View details for PubMedID 15707989
The tetraspanin web modulates immune-signalling complexes
NATURE REVIEWS IMMUNOLOGY
2005; 5 (2): 136-148
The tetraspanin web represents a new concept of molecular interactions in the immune system. Whereas most surface immune-modulating molecules involve receptor-ligand interactions, tetraspanins associate with partner proteins and facilitate their lateral positioning in the membrane. Moreover, the same tetraspanin molecule can associate with different proteins depending on the cell type. Most importantly, members of this family tend to associate with each other, together with their partners, in membrane microdomains that provide a scaffold for the transmission of external stimuli to intracellular-signalling components.
View details for DOI 10.1038/nri1548
View details for Web of Science ID 000226720800014
View details for PubMedID 15688041
The tetraspanin CD81 regulates the expression of CD19 during B cell development in a postendoplasmic reticulum compartment
JOURNAL OF IMMUNOLOGY
2003; 171 (8): 4062-4072
CD81 is a widely expressed tetraspanin that associates in B cells with CD19 in the CD19-CD21-CD81 signaling complex. CD81 is necessary for normal CD19 expression; cd81(-/-) B cells express lower levels of CD19, especially cd81(-/-) small pre-BII cells, which are almost devoid of surface CD19. The dependence of CD19 expression on CD81 is specific to this particular tetraspanin since cd9(-/-) B cells express normal levels of CD19. Furthermore, expression of human CD81 in mouse cd81(-/-) B cells restored surface CD19 to normal levels. Quantitative analysis of CD19 mRNA demonstrated normal levels, even in cd81(-/-) pre-BII cells. Analysis of CD19 at the protein level identified two CD19 glycoforms in both wild-type and cd81(-/-) B cells. The higher M(r) glycoform is significantly reduced in cd81(-/-) B cells and is endoglycosidase H (endo-H) resistant. In contrast, the low M(r) glycoform is comparably expressed in cd81(-/-) and in wild-type B cells and is endo-H sensitive. Because endo-H sensitivity is tightly correlated with endoplasmic reticulum localization, we suggest that the dependency of CD19 expression on CD81 occurs in a postendoplasmic reticulum compartment where CD81 is necessary for normal trafficking or for surface membrane stability of CD19.
View details for Web of Science ID 000185866100021
View details for PubMedID 14530327
CD81-dependent binding of hepatitis C virus E1E2 heterodimers
JOURNAL OF VIROLOGY
2003; 77 (19): 10677-10683
Hepatitis C virus (HCV) is the leading cause of chronic liver disease worldwide. HCV is also the major cause of mixed cryoglobulinemia, a B-lymphocyte proliferative disorder. Direct experimentation with native viral proteins is not feasible. Truncated versions of recombinant E2 envelope proteins, used as surrogates for viral particles, were shown to bind specifically to human CD81. However, truncated E2 may not fully mimic the surface of HCV virions because the virus encodes two envelope glycoproteins that associate with each other as E1E2 heterodimers. Here we show that E1E2 complexes efficiently bind to CD81 whereas truncated E2 is a weak binder, suggesting that truncated E2 is probably not the best tool with which to study cellular interactions. To gain better insight into virus-cell interactions, we developed a method by which to isolate E1E2 complexes that are properly folded. We demonstrate that purified E1E2 heterodimers bind to cells in a CD81-dependent manner. Furthermore, engagement of B cells by purified E1E2 heterodimers results in their aggregation and in protein tyrosine phosphorylation, a hallmark of B-cell activation. These studies provide a possible clue to the etiology of HCV-associated B-cell lymphoproliferative diseases. They also delineate a method by which to isolate biologically functional E1E2 complexes for the study of virus-host cell interaction in other cell types.
View details for DOI 10.1128/JVI.77.19.10677-10683.2003
View details for Web of Science ID 000185400400052
View details for PubMedID 12970454
Hepatitis C virus (HCV) and lymphomagenesis
LEUKEMIA & LYMPHOMA
2003; 44 (7): 1113-1120
Hepatitis C virus (HCV) is the major cause for non-A, non-B hepatitis. Most HCV-infected individuals do not clear the virus resulting in a chronic infection that may potentially lead to liver cirrhosis and hepatocellular carcinoma. In addition to hepatic manifestations, HCV infection is associated with B cell lymphoproliferative disorders, including mixed cryoglobulinemia, usually a benign condition, and overt B cell lymphoma. A direct role of HCV infection in the genesis of these B cell lymphoproliferative disorders has been suggested initially by epidemiological studies and is supported by recent studies, which analyzed the monoclonal B cells that proliferate in these disorders. How HCV induces B cell lymphoproliferative disorders is still unclear, it is probably not due to direct change of phenotype in B cells after viral infection, but may be due to an HCV-antigen driven process. Support for this hypothesis comes from the analysis of monoclonal B cells found in these disorders, which use a restricted repertoire of immunoglobulin variable region genes that are similar to those used by B cells that secrete anti-HCV antibodies. The fact that monoclonal IgM is resolved in HCV-infected patients who responded to anti-viral treatment supports the linkage between antigen persistence and B cell proliferation. Finally, the linkage between benign B cell proliferation and overt lymphoma is supported by the identification of a pre-malignant B cell clone that subsequently converted to an overt B cell lymphoma. The molecular basis for viral induced B cell proliferation is still unknown. One possibility is that HCV stimulates the proliferation of monoclonal B cells via their HCV-specific B cell receptor (BCR) on the cell surface. Binding of the HCVenvelope proteins to a cellular ligand, CD81, may also enhance this antigen-driven process. A recent report on regression of splenic marginal zone lymphoma after anti-viral treatment with interferon and ribavirin has significantly strengthened the cause-effect relationship between HCV infection and lymphoma. Further studies should determine whether BCRs expressed on HCV-associated lymphomas, particularly those that regress in response to anti-viral therapy, bind HCV antigens that stimulate their proliferation.
View details for DOI 10.1080/1042819031000076972
View details for Web of Science ID 000182775000003
View details for PubMedID 12916862
Recognition of native hepatitis C virus E1E2 heterodimers by a human monoclonal antibody
JOURNAL OF VIROLOGY
2003; 77 (2): 1604-1609
The majority of hepatitis C virus (HCV)-infected individuals progress from acute to chronic disease, despite the presence of a strong humoral immune response to the envelope glycoproteins E1 and E2. When expressed in mammalian cells, E1 and E2 form both noncovalently linked E1E2 heterodimers, believed to be properly folded, and disulfide-linked, high-molecular-weight aggregates that are misfolded. Previously, we identified 10 human monoclonal antibodies (HMAbs) that bind E2 glycoproteins from different genotypes. Here we demonstrate that one of these HMAbs, CBH-2, is unique in its ability to distinguish between properly folded and misfolded envelope proteins. This HMAb recognizes HCV-E2 only when complexed with E1. The E1E2 complexes recognized by CBH-2 are noncovalently linked heterodimers and not misfolded disulfide-linked, high-molecular-weight aggregates. The E1E2 heterodimers seen by CBH-2 no longer associate with the endoplasmic reticulum chaperone calnexin and are likely to represent the prebudding form of the HCV virion.
View details for DOI 10.1128/JVI.77.2.1604-1609.2003
View details for Web of Science ID 000180166600080
View details for PubMedID 12502876
Critical role of CD81 in cognate T-B cell interactions leading to T(h)2 responses
2002; 14 (5): 513-523
We previously demonstrated that CD81-/- mice fail to develop Th2-biased immune responses and allergen-induced airway hyper-reactivity. Because CD81 is expressed on both activated T and on B cells, we examined the role of CD81 expression by each cell type. We established an in vitro system by backcrossing the CD81 deletion to TCR transgenic (Tg) mice and to BCR Tg mice. Here we demonstrate that CD81 expression by T cells is critical for their induction of IL-4 synthesis by B cells. CD81-/- TCR Tg T cells were impaired in IL-4 production compared to CD81+/+ TCR Tg T cells, whereas CD81-/- and CD81+/+ BCR Tg B cells induced equivalent amounts of IL-4 in CD81+/+ TCR Tg T cells. CD81-/- TCR Tg T cells expressed reduced levels of ICOS, GATA-3, STAT6 and phosphorylated STAT6 when activated by antigen-presenting B cells. Taken together, these results indicate that CD81 expression by T cells greatly enhances cognate T-B cell interactions and greatly augments intracellular activation pathways leading to Th2 polarization.
View details for Web of Science ID 000175386200009
View details for PubMedID 11978781
The B-cell receptor of a hepatitis C virus (HCV)-associated non-Hodgkin lymphoma binds the viral E2 envelope protein, implicating HCV in lymphomagenesis
2001; 98 (13): 3745-3749
Hepatitis C virus (HCV) infection is associated with extrahepatic B-cell lymphoproliferative disorders. To determine whether a viral antigen drives this B-cell expansion, the B-cell receptors were cloned from HCV-associated lymphomas and were expressed as soluble immunoglobulins. The rescued immunoglobulins were then tested for their ability to bind the HCV-E2 envelope glycoprotein, an antigen that was previously implicated in the pathogenesis of HCV-associated B-cell diseases. One of 2 lymphoma immunoglobulin test cases bound the E2 protein in a manner identical to a bona fide human anti-E2 antibody. Moreover, it bound E2 from multiple viral genotypes, suggesting reactivity with a conserved E2 epitope. These findings support the hypothesis that some HCV-associated lymphomas originate from B cells that were initially activated by the HCV-E2 protein and might explain the association between HCV infection and some B-cell lymphoproliferative disorders.
View details for Web of Science ID 000172604700032
View details for PubMedID 11739181
In search of hepatitis C virus receptor(s).
Clinics in liver disease
2001; 5 (4): 873-893
Since the genomic sequence of HCV was determined, significant progress has been made towards understanding the functions of the HCV-encoded proteins, despite the lack of an efficient in-vitro replication system or convenient small-animal model. The identity of the receptor for HCV remains elusive, however. Low-density lipoprotein receptor, CD81, and GAGs may all act as receptors for HCV, either sequentially or by different viral quasispecies. Recent work using pseudotypic VSV bearing E1 or E2 chimeric molecules showed that entry of the E1 pseudotype can be inhibited by recombinant LDLr, whereas the E2 pseudotype is more sensitive to inhibition by recombinant CD81 or heparin. These results suggest that E1 and E2 may be responsible for interactions with different cellular molecules. It is also conceivable that additional, yet unidentified, cellular proteins are involved in viral binding and entry. Intriguingly, the reports of HCV-RNA associated with PBMC suggest that HCV infection may not be restricted to hepatocytes. Thus, separate reservoirs of virus may exist, and HCV may use different receptors to access these different cell types.
View details for PubMedID 11685799
Impaired dendritic cell maturation in patients with chronic, but not resolved, hepatitis C virus infection
2001; 97 (10): 3171-3176
Dendritic cells (DCs) are important for the initiation of immune responses to foreign antigens. Their antigen uptake and presentation capacities enable them to prime and activate T cells. Immature DCs capture antigens; however, they must be activated to mature before serving as efficient antigen-presenting cells. The antigen-presenting capacity of DCs can be diminished during viral infection and as a consequence of tumor formation. Chronic infection with hepatitis C virus (HCV) has been shown to affect the allostimulatory function of DCs. In this study, it is demonstrated that monocyte-derived DCs from patients with chronic HCV infection do not respond to maturation stimuli. Instead, they maintain their immature phenotype, reflected by the pattern of cell surface markers and by their continued capacity to uptake antigen. Moreover, their allostimulatory abilities are impaired compared with those of mature DCs derived from healthy donors. To investigate a possible correlation between viral clearance and this DC maturation defect, patients with resolved HCV infection after a course of antiviral therapy were studied. Results demonstrate that DCs from patients who cleared HCV behaved like DCs from healthy donors: in response to maturation stimuli, they decrease antigen uptake, up-regulate expression of appropriate surface markers, and are potent stimulators of allogeneic T cells. (Blood. 2001;97:3171-3176)
View details for Web of Science ID 000170301300033
View details for PubMedID 11342445
IL-18 gene transfer by adenovirus prevents the development of and reverses established allergen-induced airway hyperreactivity
JOURNAL OF IMMUNOLOGY
2001; 166 (10): 6392-6398
We examined the role of IL-18 in preventing the development of and in reversing established allergen-induced airway inflammation and airway hyperreactivity (AHR), the cardinal features of asthma. IL-18, which potently induces IFN-gamma, was administered into the respiratory tract as cDNA in a replication-deficient adenovirus (Adv). Treatment of OVA-sensitized mice with the IL-18-expressing Adv reduced allergen-specific IL-4 production, airway eosinophilia, and mucus production, increased IFN-gamma production, and prevented the development of AHR. The effects of the IL-18 Adv treatment were dependent on the presence of IFN-gamma and IL-12. Moreover, administration of the IL-18 Adv to mice with established AHR greatly reduced AHR and IL-4 production and increased IFN-gamma production. These results demonstrate that IL-18, when administered by Adv into the respiratory tract, effectively reduces AHR and replaces an established Th2-biased immune response with a Th1-biased response.
View details for Web of Science ID 000170948500068
View details for PubMedID 11342664
V(H)1-69 gene is preferentially used by hepatitis C virus-associated B cell lymphomas and by normal B cells responding to the E2 viral antigen
2001; 97 (4): 1023-1026
Hepatitis C virus (HCV)-associated B cell lymphomas were previously shown to express a restricted repertoire of immunoglobulin V(H) and V(L) genes, V(H)1-69 and VkappaA27, respectively. Although this suggests a role for antigen selection in the pathogenesis of these lymphomas, the driving antigen involved in the clonal expansion has not been identified. B cell response to a viral antigen, the HCV envelope glycoprotein 2 (E2), was analyzed in an asymptomatic HCV-infected patient. Single B cells, immortalized as hybridomas and selected for binding E2, were analyzed for their V gene usage. Sequences of these V region genes demonstrated that each hybridoma expressed unique V(H) and V(L) genes. Remarkably, these anti-E2 hybridomas preferentially used the V(H)1-69 gene. Analysis of replacement to silent mutation ratios indicated that the genes underwent somatic mutation and antigenic selection. In a separate report, human anti-E2 antibodies were also shown to express the same V(H) gene. These data strengthen the hypothesis that the HCV-associated lymphomas are derived from clonally expanded B cells stimulated by HCV.
View details for Web of Science ID 000166867200032
View details for PubMedID 11159532
Vaccination with allergen-IL-18 fusion DNA protects against, and reverses established, airway hyperreactivity in a murine asthma model
JOURNAL OF IMMUNOLOGY
2001; 166 (2): 959-965
Vaccination with naked DNA encoding a specific allergen has been shown previously to prevent, but not reverse, the development of allergen-induced airway hyperresponsiveness (AHR). To enhance the effectiveness of DNA vaccine therapies and make possible the treatment of established AHR, we developed a DNA vaccination plasmid containing OVA cDNA fused to IL-18 cDNA. Vaccination of naive mice either with this fusion DNA construct or with an OVA cDNA-containing plasmid protected the mice from the subsequent induction of AHR. Protection from AHR correlated with increased IFN-gamma production and reduced OVA-specific IgE production. The protection appeared to be mediated by IFN-gamma and CD8(+) cells because treatment of mice with neutralizing anti-IFN-gamma mAb or with depleting anti-CD8 mAb abolished the protective effect. Moreover, vaccination of mice with preexisting AHR with the OVA-IL-18 fusion DNA, but not with the OVA cDNA plasmid, reversed established AHR, reduced allergen-specific IL-4, and increased allergen-specific IFN-gamma production. Thus, combining IL-18 cDNA with OVA cDNA resulted in a vaccine construct that protected against the development of AHR, and that was unique among cDNA constructs in its capacity to reverse established AHR.
View details for Web of Science ID 000166259600033
View details for PubMedID 11145673
Human monoclonal antibodies that inhibit binding of hepatitis C virus E2 protein to CD81 and recognize conserved conformational epitopes
JOURNAL OF VIROLOGY
2000; 74 (22): 10407-10416
The intrinsic variability of hepatitis C virus (HCV) envelope proteins E1 and E2 complicates the identification of protective antibodies. In an attempt to identify antibodies to E2 proteins from divergent HCV isolates, we produced HCV E2 recombinant proteins from individuals infected with HCV genotypes 1a, 1b, 2a, and 2b. These proteins were then used to characterize 10 human monoclonal antibodies (HMAbs) produced from peripheral B cells isolated from an individual infected with HCV genotype 1b. Nine of the antibodies recognize conformational epitopes within HCV E2. Six HMAbs identify epitopes shared among HCV genotypes 1a, 1b, 2a, and 2b. Six, including five broadly reactive HMAbs, could inhibit binding of HCV E2 of genotypes 1a, 1b, 2a, and 2b to human CD81 when E2 and the antibody were simultaneously exposed to CD81. Surprisingly, all of the antibodies that inhibited the binding of E2 to CD81 retained the ability to recognize preformed CD81-E2 complexes generated with some of the same recombinant E2 proteins. Two antibodies that did not recognize preformed complexes of HCV 1a E2 and CD81 also inhibited binding of HCV 1a virions to CD81. Thus, HCV-infected individuals can produce antibodies that recognize conserved conformational epitopes and inhibit the binding of HCV to CD81. The inhibition is mediated via antibody binding to epitopes outside of the CD81 binding site in E2, possibly by preventing conformational changes in E2 that are required for CD81 binding.
View details for Web of Science ID 000090083800016
View details for PubMedID 11044085
Allergen-induced airway hyperreactivity is diminished in CD81-deficient mice
JOURNAL OF IMMUNOLOGY
2000; 165 (9): 5054-5061
We demonstrated previously that CD81(-/-) mice have an impaired Th2 response. To determine whether this impairment affected allergen-induced airway hyperreactivity (AHR), CD81(-/-) BALB/c mice and CD81(+/+) littermates were sensitized i.p. and challenged intranasally with OVA. Although wild type developed severe AHR, CD81(-/-) mice showed normal airway reactivity and reduced airway inflammation. Nevertheless, OVA-specific T cell proliferation was similar in both groups of mice. Analysis of cytokines secreted by the responding CD81(-/-) T cells, particularly those derived from peribronchial draining lymph nodes, revealed a dramatic reduction in IL-4, IL-5, and IL-13 synthesis. The decrease in cytokine production was not due to an intrinsic T cell deficiency because naive CD81(-/-) T cells responded to polyclonal Th1 and Th2 stimulation with normal proliferation and cytokine production. Moreover, there was an increase in T cells and a decrease in B cells in peribronchial lymph nodes and in spleens of immunized CD81(-/-) mice compared with wild-type animals. Interestingly, OVA-specific Ig levels, including IgE, were similar in CD81(-/-) and CD81(+/+) mice. Thus, CD81 plays a role in the development of AHR not by influencing Ag-specific IgE production but by regulating local cytokine production.
View details for Web of Science ID 000090076000039
View details for PubMedID 11046035
Differential expression of murine CD81 highlighted by new anti-mouse CD81 monoclonal antibodies
2000; 19 (1): 15-22
We describe the use of a soluble CD81-Fc fusion protein to screen for novel monoclonal antibody (MAb) reactive with the extracellular loops of murine CD81 (TAPA-1). Two such MAbs, Eat1 and Eat2 (for Extracellular Anti-TAPA1), were used to assess the expression and function of CD81 on murine lymphocytes. Although CD81 is expressed uniformly on all human lymphocytes, murine CD81 was found to be expressed at much higher levels on resting B cells than on resting T cells. This was particularly evident when staining with the new MAbs, Eat1 and Eat2. The molecule is also functionally active on B cells, as Eat1 and Eat2 induce homotypic adhesion of B lymphocytes. Stimulated B cells undergo early apoptotic events in the presence of Eat2, as shown by binding of Annexin V-fluorescein isothiocyanate (FITC). Polyclonal activation of murine T cells also induces higher level CD81 expression, and many immortalized murine T-cell lines express high levels of the protein. In contrast to human CD81, which is expressed equally on all thymocytes, murine CD81 is induced during thymic development, being expressed at high levels on CD4+CD8+ thymocytes, in contrast to other subsets of thymocytes. Finally, murine dendritic cells, splenic macrophages, and non-killer (NK) cells all express high levels of CD81. We conclude that CD81 is differentially expressed in the murine immune system, and is involved in regulating the adhesion and activation of murine B cells.
View details for Web of Science ID 000086240300002
View details for PubMedID 10768837
Cytotoxic T cell responses to DNA vaccination: Dependence on antigen presentation via class II MHC
JOURNAL OF IMMUNOLOGY
1998; 161 (12): 6532-6536
This study was designed to test whether cytotoxic T cell (CTL) responses to DNA vaccination are dependent upon MHC class II-restricted priming of CD4+ T cells. Because DNA vaccination may directly transfect dendritic cells, and dendritic cells may be capable of directly stimulating CD8+ T cell responses, such priming might be unnecessary. To test this hypothesis, C57BL/6 mice were immunized intramuscularly or intradermally with DNA encoding either whole OVA, a class I (Kb)-restricted peptide epitope of OVA (amino acids 257-264, SIINFEKL), or this class I-restricted epitope plus the adjacent class II (I-Ab)-restricted epitope of OVA (amino acids 265-280, TEWTSSNVMEERKIKV). Very low to negligible CTL responses were observed in mice vaccinated with the SIINFEKL construct, whereas mice vaccinated with the SIINFEKLTEWTSSNVMEERKIKV or with the complete OVA construct made equally robust CTL responses. These responses were sensitive to blocking by anti-CD8 mAb and were shown to be SIINFEKL-specific by using SIINFEKL peptide-pulsed EL-4 cells as targets. To ensure that the generation of these CTL responses was indeed dependent upon CD4+ T cell help, mice were depleted of either CD4+ or CD8+ cells before immunization. Depletion of CD4+ cells completely abrogated the CTL response to OVA DNA, as did depletion of CD8+ cells. Thus, we conclude that the CTL response to both intramuscular and intradermal DNA vaccination is highly dependent upon the generation of CD4+ T cell help via a class II MHC-dependent pathway. These results will be relevant for the construction of minimal-epitope vaccines for DNA immunization.
View details for Web of Science ID 000077436400014
View details for PubMedID 9862678
Sequences and expression of six new members of the tetraspanin/TM4SF family
BIOCHIMICA ET BIOPHYSICA ACTA-GENE STRUCTURE AND EXPRESSION
1998; 1399 (1): 101-104
Tetraspanins (or TM4SF) are expressed in a wide variety of species and regulate cell adhesion, migration, proliferation and differentiation. We have identified and sequenced six new members of the tetraspanin family, called Tspan-1-6, from human cDNA. Amino acid sequence analysis of the Tspans highlights conserved residues which may be critical to tetraspanin structure and function. The Tspans are differentially expressed in human tissues.
View details for Web of Science ID 000075343500016
View details for PubMedID 9714763
CD81 on B cells promotes interleukin 4 secretion and antibody production during T helper type 2 immune responses
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
1998; 95 (5): 2458-2462
Mice lacking CD81 (TAPA-1), a widely expressed tetraspanin molecule, have impaired antibody responses to protein antigens. This defect is specific to antigens that preferentially stimulate a T helper 2 response (ovalbumin or keyhole limpet hemocyanin in alum) and is only seen with T cell-dependent antigens. Absence of CD81 on B cells is sufficient to cause the defect. Also, antigen-specific interleukin (IL) 4 production is greatly reduced in the spleen and lymph nodes of CD81-null mice compared with heterozygous littermates. Thus, expression of CD81 on B cells is critical for inducing optimal IL-4 and antibody production during T helper 2 responses. These findings suggest that CD81 may interact with a ligand on T cells to signal IL-4 production. By using a soluble form of CD81 as a probe, a putative ligand for CD81 was identified on a subset of B and T cells. Two possible models for the interaction of CD81 on B cells with a potential ligand on either B or T cells are proposed.
View details for Web of Science ID 000072366600093
View details for PubMedID 9482907
CD81 (TAPA-1): A molecule involved in signal transduction and cell adhesion in the immune system
ANNUAL REVIEW OF IMMUNOLOGY
1998; 16: 89-109
CD81 (TAPA-1) is a widely expressed cell-surface protein involved in an astonishing variety of biologic responses. It has been cloned independently several times for different functional effects and is reported to influence adhesion, morphology, activation, proliferation, and differentiation of B, T, and other cells. On B cells CD81 is part of a complex with CD21, CD19, and Leu13. This complex reduces the threshold for B cell activation via the B cell receptor by bridging Ag specific recognition and CD21-mediated complement recognition. Similarly on T cells CD81 associates with CD4 and CD8 and provides a costimulatory signal with CD3. In fetal thymic organ culture, mAb to CD81 block maturation of CD4-CD8- thymocytes, and expression of CD81 on CHO cells endows those cells with the ability to support T cell maturation. However, CD81-deficient mice express normal numbers and subsets of T cells. These mice do exhibit diminished antibody responses to protein antigens. CD81 is also physically and functionally associated with several integrins. Anti-CD81 can activate integrin alpha 4 beta 1 (VLA-4) on B cells, facilitating their adhesion to tonsilar interfollicular stroma. Similarly, anti-CD81 can activate alpha L beta 2 (LFA-1) on human thymocytes. CD81 can also affect cognate B-T cell interactions because anti-CD81 increases IL-4 synthesis by T cells responding to antigen presented by B cells but not by monocytes. The tetraspanin superfamily (or TM4SF) includes CD81, CD9, CD37, CD53, CD63, CD82, CD151, and an increasing number of additional proteins. Like CD81, several tetraspanins are involved in cell adhesion, motility, and metastasis, as well as cell activation and signal transduction.
View details for Web of Science ID 000073129400004
View details for PubMedID 9597125
Idiotype vaccines for non-Hodgkin's lymphoma induce polyclonal immune responses that cover mutated tumor idiotypes: Comparison of different vaccine formulations
1997; 90 (9): 3699-3706
The idiotype (Id) of the Ig expressed on the surface of non-Hodgkin's lymphoma cells is a suitable target for immunotherapy. Indeed, treatment with monoclonal anti-Id antibodies (Abs) can induce long-lasting clinical remissions. However, some of the treated patients relapse with a tumor expressing Ig with point mutations in the idio recognized by the particular monoclonal antibody (MoAb). The alternative approach of active immunization with tumor Id can cure the disease in mice with established tumors and is now being studied in clinical trials. Here, we tested the hypothesis that active immunization with the idiotype would evoke a polyclonal immune response that would cover mutated tumor variants. As a test system, we chose the tumor from a patient who had achieved a complete remission after therapy with anti-Id Ab but subsequently relapsed with a mutated tumor variant no longer binding the treatment Ab. Mice were immunized with proteins and genetic vaccines derived from the original tumor, including (1) Id-keyhole limpet hemocyanin protein, (2) Id single-chain variable fragment (scFv) granulocyte-macrophage colony-stimulating factor (GM-CSF) protein, (3) DNA encoding the Id, and (4) an adenovirus encoding the Id. All immunized mice developed a specific immune response detecting tumor-derived Id proteins from the original tumor and from all tumor variants. We conclude that active immunization with tumor Id can induce a polyclonal immune response and therefore may prevent the escape of mutated tumor variants.
View details for Web of Science ID A1997YD10800047
View details for PubMedID 9345055
DNA vaccination with cytokine fusion constructs biases the immune response to ovalbumin
1997; 15 (15): 1687-1696
DNA vaccination may work through direct transfection of antigen presenting cells (APC), or by secretion of the encoded protein by muscle or skin cells for uptake by APC. If cytokines are attached to the antigen, they may influence APC or responding T cells to drive the response toward a Th1 or Th2 direction, and/or potentiate it in an antigen-specific manner. To test this concept, expression vectors were constructed containing the ovalbumin (OVA) gene either alone, or linked to cytokine genes including GM-CSF, IFN-gamma, IL-2, IL-4, IL-12, or a sequence encoding nine amino acids of IL-1 beta. These constructs expressed OVA-cytokine fusion proteins in vitro which retained cytokine bioactivity. C57BL/6 mice were injected intramuscularly with the DNA constructs. Little if any OVA-specific antibody was produced in response to any of the DNA constructs, except for OVA-IL-4. However, lymphocytes from BALB/c mice vaccinated with OVA-IL-12 and OVA-IL-1 beta constructs produced more IFN-gamma and less IL-4 during in vitro restimulation assays than did other groups. All constructs elicited OVA-specific cytotoxic responses which were maintained or even increased over 16 weeks. The OVA-IL-12 and OVA-IL-1 beta peptide constructs elicited the strongest cytotoxic responses at 2 weeks postinjection. Cytotoxic responses were seen in all animals, even those lacking OVA-specific Ab, and were not related to Ab level. These studies indicate that the humoral, cytokine, and cytotoxic responses to DNA vaccination can be effectively altered by certain cytokine fusion constructs.
View details for Web of Science ID A1997YB29800014
View details for PubMedID 9364701
The tetraspanin superfamily: Molecular facilitators
1997; 11 (6): 428-442
A legacy of molecular evolution is the formation of gene families encoding proteins that often serve related functions. One such family gaining recent attention is the tetraspanin superfamily, whose membership has grown to nearly 20 known genes since its discovery in 1990. All encode cell-surface proteins that span the membrane four times, forming two extracellular loops. Some of these genes are found in organisms as primitive as schistosomes and nematodes. Alternately known as the transmembrane 4 (TM4) superfamily or the TM4SF, 4TM, or tetraspan family, we propose here that the name tetraspanins be used for the purpose of standardization. What do the tetraspanins do? Awaiting definitive functional studies, we can only put together pieces of a puzzle that has been built by raising antibodies against these proteins and looking at their distribution, associations, and functions. A brief overview indicates that some tetraspanins are found in virtually all tissues (CD81, CD82, CD9, CD63), whereas others are highly restricted, such as CD37 (B cells) or CD53 (lymphoid and myeloid cells). Many of these proteins have a flair for promiscuous associations with other molecules, including lineage-specific proteins, integrins, and other tetraspanins. In terms of function, they are involved in diverse processes such as cell activation and proliferation, adhesion and motility, differentiation, and cancer. We propose that these functions may all relate to their ability to act as "molecular facilitators," grouping specific cell-surface proteins and thus increasing the formation and stability of functional signaling complexes.
View details for Web of Science ID A1997XE40400005
View details for PubMedID 9194523
An ovalbumin-IL-12 fusion protein is more effective than ovalbumin plus free recombinant IL-12 in inducing a T helper cell type 1-dominated immune response and inhibiting antigen-specific IgE production
JOURNAL OF IMMUNOLOGY
1997; 158 (9): 4137-4144
Optimal treatment of allergic diseases requires that the cytokine profile of allergen-specific T cells be redirected, with the conversion of Th2 profiles into Th1 cytokine profiles. This conversion, however, is difficult, since Th2 effector cells have relatively fixed cytokine profiles. To more effectively redirect the cytokine profiles of T cells, we constructed a cytokine fusion protein that contained the Ag OVA, fused to IL-12. Immunization with the OVA-IL-12 fusion protein induced anti-OVA IgG2a Ab and large quantities of OVA-specific IFN-gamma production. The Ag specificity of this response was dependent upon covalent linkage of Ag and IL-12, since immunization of mice with OVA alone induced little or no IFN-gamma, while immunization with OVA and free rIL-12 enhanced T cell production of IFN-gamma, but the IFN-gamma production was not OVA specific. To examine the effects of OVA-IL-12 in reversing ongoing Th2-dominated immune responses, BALB/c mice previously primed with OVA in alum to induce a Th2-dominated response, were vaccinated with the OVA-IL-12 protein. In such mice, OVA-IL-12 was much more effective than OVA plus free rIL-12 in significantly increasing Ag-specific IFN-gamma production and significantly decreasing Ag-specific IL-4 production. Moreover, OVA-IL-12 increased serum anti-OVA IgG2a and decreased anti-OVA IgE. These studies indicate that OVA-IL-12 can convert immune responses characterized by high IL-4 and high IgE synthesis into Th1-dominated responses in an Ag-specific manner.
View details for Web of Science ID A1997WV76100016
View details for PubMedID 9126973
Normal lymphocyte development but delayed humoral immune response in CD81-null mice
JOURNAL OF EXPERIMENTAL MEDICINE
1997; 185 (8): 1505-1510
CD81 is a cell surface molecule expressed on many cell types and associated with the CD19/CD21/Leu13 signal-transducing complex on B cells. A recent report implies that CD81 expression on thymic stromal cells is important in the maturation of thymocytes from CD4-CD8- to CD4+CD8+. However, we have produced CD81-null mice by gene targeting, and find that they undergo normal development of thymocytes and express normal numbers of T cells. B cells are also found in normal numbers in the spleen, blood, and peritoneal cavity of CD81-null mice, but they express a lower level of CD19 compared to heterozygous littermates. Finally, early antibody responses to the protein antigen ovalbumin are weaker in CD81-null mice compared to their heterozygous littermates. This is consistent with the proposed role of the CD19/CD21/CD81-signaling complex in lowering the threshold for B cell responses. These results show that CD81 is not required for maturation of T cells, but is important for optimal expression of CD19 on B cells and optimal stimulation of antibody production.
View details for Web of Science ID A1997WW04700013
View details for PubMedID 9126932
A nine-amino acid peptide from IL-1 beta augments antitumor immune responses induced by protein and DNA vaccines
JOURNAL OF IMMUNOLOGY
1996; 157 (12): 5503-5511
The idiotypic determinants of B cell lymphoma provide a tumor-specific Ag and a target for immunotherapy. We have developed several generations of idiotype vaccines that were tested in an animal model, the 38C13 mouse B cell lymphoma. Initially we showed that effective tumor immunity was elicited by the syngeneic Id when it was conjugated to a carrier protein and mixed with an adjuvant. A subsequent generation of Id vaccines eliminated the need for a carrier protein and for an adjuvant by incorporating cytokines into fusion proteins containing the Id. A third generation of vaccines consisting of naked DNA encoding the Id-granulocyte-macrophage colony-stimulating factor (GM-CSF) fusion proteins was equally effective in inducing tumor immunity. To determine whether Ig variable regions, in the absence of constant regions, could be immunotherapeutic in this model, we tested the use of single-chain Fv (scFv). scFv proteins, produced in bacteria, and naked DNA encoding scFv were used in this study. scFv was tested alone or fused to GM-CSF or an immunoenhancing peptide derived from IL-1beta. Here we demonstrate that scFv-GM-CSF was effective only when injected as a protein, not as a DNA vaccine. In contrast, both scFv-IL-1beta peptide fusion protein and naked DNA encoding it induced tumor immunity that protected mice from tumor challenge.
View details for Web of Science ID A1996VX02600036
View details for PubMedID 8955200
Ligation of TAPA-1 (CD81) or major histocompatibility complex class II in co-cultures of human B and T lymphocytes enhances interleukin-4 synthesis by antigen-specific CD4(+) T cells
EUROPEAN JOURNAL OF IMMUNOLOGY
1996; 26 (7): 1435-1442
We have previously shown that CD4+ T cells from allergic individuals are predisposed to producing interleukin (IL)-4 in response to allergens. IL-4 production could be modulated by antigen concentration as well as by the type of antigen-presenting cells (APC), with B lymphocytes inducing greater quantities of IL-4 than monocytes. Using this system we examined IL-4 synthesis after culture of CD4+ T cells with B cells, monocytes, or both, as APC in the presence of allergen and a monoclonal antibody against CD81 (TAPA-1), a member of the TM4 superfamily of proteins that regulates activation, proliferation and trafficking of B cells. Addition of anti-CD81 mAb during culture enhanced IL-4 synthesis by 2- to 70-fold over that using an isotype-matched control mAb. Furthermore, anti-CD81 mAb enhanced IL-4 synthesis in CD4+ T cells only when CD4+ T cells were cultured with B cells but not monocytes as APC, indicating that anti-CD81 mAb affected IL-4 synthesis in T cells via interactions with B cells. However, pretreatment of either population separately with anti-CD81 mAb prior to culture had no effect on subsequent IL-4 synthesis, suggesting a requirement for temporal or cooperative interactions between T and B lymphocytes. In addition, anti-CD81 mAb enhanced IL-4 production but reduced CD4+ T cell antigen-specific proliferation, demonstrating that IL-4 production and proliferation by CD4+ T cells were inversely related. Finally, mAb to major histocompatibility complex class II but not to anti-CD19 also enhanced IL-4 synthesis when B lymphocytes were used as APC. In all instances, enhancement of CD4+ IL-4 synthesis correlated with the presence of large cell aggregates in T-B lymphocyte cocultures. These results indicate that the capacity of B cells to induce IL-4 can be significantly enhanced by ligation of particular molecules on their surface and should aid in the design of treatments for diseases in which modulation of the cytokine profile would be beneficial.
View details for Web of Science ID A1996UY11000005
View details for PubMedID 8766544
Novel unconventional binding site in the variable region of immunoglobulins
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
1996; 93 (12): 6019-6024
The variable immunoglobulin (Ig) domains contain hypervariable regions that are involved in the formation of the antigen binding site. Besides the canonical antigen binding site, so-called unconventional sites also reside in the variable region that bind bacterial and viral proteins. Docking to these unconventional sites does not typically interfere with antigen binding, which suggests that these sites may be a part of the biological functions of Igs. Herein, a novel unconventional binding site is described. The site is detected with 8-azidopurine nucleotide photoaffinity probes that label antibodies efficiently and under mild conditions. Tryptic peptides were isolated from photolabeled monoclonal antibodies and aligned with the variable antibody domains of heavy and light chains. The structure of a variable Ig fragment was used to model the binding of the purine nucleotide to invariant residues in a hydrophobic pocket of the Ig molecule at a location distant from the antigen binding site. Monoclonal and polyclonal antibodies were biotinylated with the photoaffinity linker and used in fluorescence-activated cell sorter and ELISA analyses. The data support the utility of this site for tethering diagnostic and therapeutic agents to the variable Ig fragment region without impairing the structural and functional integrity of antibodies.
View details for Web of Science ID A1996UQ45500064
View details for PubMedID 8650212
THE TAPA-1 MOLECULE IS ASSOCIATED ON THE SURFACE OF B-CELLS WITH HLA-DR MOLECULES
JOURNAL OF IMMUNOLOGY
1993; 151 (8): 4090-4097
TAPA-1 is a transmembrane protein that has been shown to be involved in cell growth and cellular adhesion. Our studies were aimed at determining the mechanisms of the biologic phenomena mediated by TAPA-1, which include the identification of proteins that are associated with it on the surface of lymphocytes. We and others have previously shown that Leu-13, a leukocyte Ag, is one such molecule and that in B cells TAPA-1 is associated with the CD19 Ag. Herein we identify an additional molecule, HLA-DR, that is noncovalently associated on the surface of B cells with TAPA-1. This association was first detected by immunoprecipitation by anti-TAPA-1 and by anti-HLA-DR antibodies in the presence of mild detergents. The initial observation was confirmed by 2-dimensional SDS-PAGE and by direct identification of TAPA-1 in anti-HLA-DR immunoprecipitates by Western blot analysis. The association of the two molecules on the surface of a human B cell line was shown by cocapping experiments. In addition, antibodies to both molecules can induce cellular adhesion and an antiproliferative effect. Because the tissue distribution of these two molecules only partially overlaps, with TAPA-1 being expressed on most cell types and MHC class II expressed on a more restricted group of tissue, it is possible that the TAPA-1 molecule provides a basic function that can augment a cell type specific activity. In B cells the association of TAPA-1 with CD19 and HLA-DR may increase cellular interaction and play a supporting role in the transmission of specific signals.
View details for Web of Science ID A1993MB16300015
View details for PubMedID 8409388
ANTI-TAPA-1 ANTIBODIES INDUCE PROTEIN-TYROSINE PHOSPHORYLATION THAT IS PREVENTED BY INCREASING INTRACELLULAR THIOL LEVELS
JOURNAL OF IMMUNOLOGY
1993; 151 (4): 1918-1925
We studied the signal induced by the anti-TAPA-1 antibody and compared it to the signal induced by anti-IgM antibodies in a human B cell line, OCl-LY8. We found that exposure of these cells to either antibody resulted in a rapid increase in protein tyrosine phosphorylation which was prevented by inhibitors of tyrosine kinases. Tyrosine phosphorylation was an early event in the cascase leading to the antiproliferative effect of the anti-TAPA-1 antibody. However, 2-ME, a reducing agent that is not an inhibitor of tyrosine kinases, prevented both tyrosine phosphorylation and the antiproliferative effect of the antibody. Cells grown in low concentrations of 2-ME did not exhibit an increase in tyrosine phosphorylation in response to the anti-TAPA-1 antibody and were insensitive to the antiproliferative effect of the antibody. In contrast, the same cells maintained in 2-ME were able to induce tyrosine phosphorylation in response to anti-IgM. The use of 2-ME resulted in an increase in intracellular thiols, mostly glutathione. Moreover, compounds that block glutathione synthesis rendered cells susceptible to the antibody, even in the presence of 2-ME. These experiments demonstrate that tyrosine kinases are involved in propagating the antiproliferative signal initiated by the anti-TAPA-1 antibody and suggest that this signal is dependent upon the level of intracellular thiols.
View details for Web of Science ID A1993LR90400017
View details for PubMedID 7688390
EXPRESSION OF TAPA-1 IN PREIMPLANTATION MOUSE EMBRYOS
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
1992; 186 (3): 1201-1206
TAPA-1 is a member of a new family of evolutionarily conserved transmembrane proteins which may be involved in regulation of cell growth and/or cell signalling. We have examined the temporal pattern of TAPA-1 RNA expression during mouse development. Using a sensitive reverse transcription/polymerase chain reaction assay, we show that TAPA-1 RNA is present in oocytes, fertilized eggs and cleavage stage embryos.
View details for Web of Science ID A1992JJ80300003
View details for PubMedID 1380797
USE OF FAMILY SPECIFIC LEADER REGION PRIMERS FOR PCR AMPLIFICATION OF THE HUMAN HEAVY-CHAIN VARIABLE REGION GENE REPERTOIRE
1992; 29 (2): 193-203
We have designed a set of six, non-degenerate oligonucleotide primers, corresponding to the 5' leader regions of each of the six human VH gene families. A general strategy for family specific polymerase chain reaction amplification is described using these primers and a conserved 3' primer corresponding to frame work 3, JH, or constant region. This strategy was used to isolate and sequence novel human germline VH genes belonging to the VH2 and VH4 families. Under certain conditions, chimeric VH sequences were created by a "jumping polymerase chain reaction", combining DNA segments from different germline genes, but this could be avoided by limiting the number of amplification cycles. PCR amplification with these family specific primers will facilitate studies of the repertoire of germline VH genes as well as studies on VH gene usage in normal and aberrant (B cell malignancies, autoimmune diseases, etc.) B cell populations.
View details for Web of Science ID A1992HF03200006
View details for PubMedID 1542297
IG VH GENE-EXPRESSION AMONG HUMAN FOLLICULAR LYMPHOMAS
1991; 78 (6): 1561-1568
Thirty-six randomly selected cases of low grade follicular lymphoma (FL) were analyzed for Ig heavy chain variable region (VH) gene expression. Assignment to one of the six human VH gene families (VH1 to VH6) was made with a polymerase chain reaction-based technique using family-specific leader primers. The frequency of VH family use in FL was found to be similar to that reported for normal peripheral blood lymphocytes and is therefore also roughly proportional to VH family size. To evaluate expression within an individual family, all of the lymphoma VH genes from the middle size VH4 family were sequenced and compared with previously published sequences. Of these eight lymphoma VH sequences, six were most closely related to just two of the 10 known functional VH4 germline genes. Nonrandom usage by FL of the JH3, JH4, and JH5 joining segments was also observed. Nucleotide sequences were also determined for 10 randomly selected lymphoma VH genes from the large VH3 family. With one possible exception, none of these lymphoma VH sequences appear to represent any of the VH3 genes that may be preferentially used in the fetal repertoire.
View details for Web of Science ID A1991GF44400023
View details for PubMedID 1909196
STRUCTURE AND MEMBRANE TOPOLOGY OF TAPA-1
JOURNAL OF BIOLOGICAL CHEMISTRY
1991; 266 (22): 14597-14602
TAPA-1 (the target of an antiproliferative antibody) is a 26-kDa cell surface protein expressed on most human cell lines. TAPA-1 is a member of an evolutionarily related family of cell surface proteins all of which contain four transmembrane domains. A model is proposed for topology of TAPA-1 based on proteolysis studies in the in vitro translated protein embedded into microsomal membranes. This analysis predicts that the amino and the carboxyl termini of the molecule are cytoplasmic and that the two hydrophilic regions of the molecule are extracellular. The antigenic epitope of the human TAPA-1 is contained within a subregion of the second extracellular domain of the protein. This is the only region in the protein that has not been tightly conserved in mammalian evolution.
View details for Web of Science ID A1991FZ35100076
View details for PubMedID 1860863
GENOMIC ORGANIZATION AND CHROMOSOMAL LOCALIZATION OF THE TAPA-1 GENE
JOURNAL OF IMMUNOLOGY
1991; 147 (3): 1030-1036
TAPA-1 is a 26-kDa integral membrane protein expressed on many human cell types. Antibodies against TAPA-1 induce homotypic aggregation of cells and can inhibit their growth. The murine homologue of TAPA-1 was cloned from both cDNA and genomic DNA libraries. A very high level of homology was found between human and mouse TAPA-1. The 5' untranslated region of the TAPA-1 gene resembles housekeeping gene promoters with respect to G + C content and the presence of potential Sp1 binding sites. The chromosomal localization of human and murine TAPA-1 genes was determined by Southern blot experiments using DNA from somatic cell hybrids. The genes were found to be part of a conserved syntenic group in mouse chromosome 7 and the short arm of human chromosome 11. The organization of the TAPA-1 gene and the projection of the exon boundaries on the proposed protein structure are presented.
View details for Web of Science ID A1991FY29200041
View details for PubMedID 1650385
TAPA-1, THE TARGET OF AN ANTIPROLIFERATIVE ANTIBODY, IS ASSOCIATED ON THE CELL-SURFACE WITH THE LEU-13 ANTIGEN
JOURNAL OF IMMUNOLOGY
1990; 145 (7): 2207-2213
A murine mAb, 5A6 (IgG1), has been isolated by immunization with a human B lymphoma cell line and screening for growth inhibition. The antibody immunoprecipitated a single chain protein of 26 kDa from cell lysates made with Triton X-100 but additional proteins were precipitated when cell lysates were made with the milder detergent CHAPS (3-[3-cholamidopropyl)dimethylammonio)-1-propane sulfate). We have identified one of these coprecipitated molecules as the 16-kDa Leu-13 Ag. 5A6 and anti-Leu-13 showed similar, although not identical, reactivity, growth inhibition and temperature-dependent aggregation effects among hematolymphoid cell lines. The aggregation induced by 5A6 and anti-Leu-13 was not dependent on LFA-1 (lymphocyte function-associated Ag-1). The cell-surface expression of both TAPA-1 (target of an antiproliferative antibody-1) and Leu-13 could be down-modulated by binding to their respective antibodies and they could be reciprocally comodulated. These results suggest that TAPA-1 and Leu-13 form a complex on the cell surface and play a role in growth control through a common pathway.
View details for Web of Science ID A1990DZ68500029
View details for PubMedID 2398277
TAPA-1, THE TARGET OF AN ANTIPROLIFERATIVE ANTIBODY, DEFINES A NEW FAMILY OF TRANSMEMBRANE PROTEINS
MOLECULAR AND CELLULAR BIOLOGY
1990; 10 (8): 4007-4015
A murine monoclonal antibody was identified by its ability to induce a reversible antiproliferative effect on a human lymphoma cell line. Immunoprecipitation studies revealed that the antibody reacted with a 26-kilodalton cell surface protein (TAPA-1). A diverse group of human cell lines, including hematolymphoid, neuroectodermal, and mesenchymal cells, expressed the TAPA-1 protein. Many of the lymphoid cell lines, in particular those derived from large cell lymphomas, were susceptible to the antiproliferative effects of the antibody. TAPA-1 may therefore play an important role in the regulation of lymphoma cell growth. A cDNA clone coding for TAPA-1 was isolated by using the monoclonal antibody to screen an expression library in COS cells. Analysis of the deduced amino acid sequence indicated that the protein is highly hydrophobic and that it contains four putative transmembrane domains and a potential N-myristoylation site. TAPA-1 showed strong homology with the CD37 leukocyte antigen and with the ME491 melanoma-associated antigen, both of which have been implicated in the regulation of cell growth.
View details for Web of Science ID A1990DP92000016
View details for PubMedID 1695320
IDIOTYPIC VARIATION IN A HUMAN B-LYMPHOMA CELL-LINE
JOURNAL OF IMMUNOLOGY
1990; 144 (2): 752-758
The Ig Id of a B cell lymphoma serves as a distinct marker of the malignant clone and thus as a tumor-specific target for antibody therapy. Somatic variation of the Ig genes expressed by B cell tumors can lead to loss of reactivity with anti-Id antibodies and escape of tumors from the therapeutic effects of such antibodies. In our study, we have used anti-Id antibodies to screen for variants within a cell line derived from a patient with a large cell lymphoma of the B cell type. Cells were simultaneously stained on their surface for idiotypic and for isotypic Ig determinants using reagents labeled with different fluorochromes. Tumor cells expressing intact Ig molecules with alteration of their idiotypic determinants were isolated with the fluorescence activated cell sorter. Idiotypic variation was an ongoing process in vitro with Id- variants being generated at a rate of 2.7 x 10(-4)/cell per generation and Ig- cells being produced at a rate of 1.31 x 10(-5)/cell per generation. Subcloned variants expressed subtle differences in reactivity with a panel of three non-cross-blocking anti-Id antibodies. Analysis of Ig gene rearrangements by the Southern blotting technique using a JH probe established that the variants and the original tumor cells were all clonally related. Immunoprecipitation of surface labeled Ig molecules from the variant subclones disclosed major alterations of the lambda-L chains with no gross alterations of the mu-H chains. Related studies have established that the tumor cells undergo rearrangement and expression of new lambda-L chain genes.
View details for Web of Science ID A1990CH29500051
View details for PubMedID 2295809
FUNCTIONAL IMMUNOGLOBULIN LIGHT CHAIN GENES ARE REPLACED BY ONGOING REARRANGEMENTS OF GERMLINE VK GENES TO DOWNSTREAM JK SEGMENTS IN A MURINE B-CELL LINE
JOURNAL OF EXPERIMENTAL MEDICINE
1989; 170 (1): 1-13
A murine B cell lymphoma (38C13) was subjected to immunoselection with mAbs directed against the idiotypic determinants of its cell surface Ig. Variants emerged with altered Ig receptors containing identical heavy chains but different light chains. The functional light chain genes in these variants were composed of V kappa segments drawn from the V kappa Ox-1 family, which had replaced the V kappa gene expressed by the parental tumor by rearranging to downstream J kappa segments. Rearrangement at the kappa locus continued to occur spontaneously, giving rise to secondary and tertiary variants at a rate of 1.9 x 10(-4) per cell per generation. Variants were isolated that had ceased production of surface Ig but went on to rearrange again and to become surface Ig+. The Ig- state may be an intermediate step providing a stimulus for continued rearrangement. This process provides an additional mechanism for generating diversity within B cell clones and expands the use of the available repertoire of Ig genes.
View details for Web of Science ID A1989AE68500001
View details for PubMedID 2501443
ACTIVATION OF AN EXCLUDED IMMUNOGLOBULIN ALLELE IN A HUMAN B-LYMPHOMA CELL-LINE
1989; 244 (4902): 337-339
Mature B cells that express surface immunoglobulin (Ig) are usually committed to their original Ig product. It was shown that such a cell can replace its light chain by rearranging and expressing a new light chain from the other allele. Anti-idiotype antibodies were used to isolate idiotypic variants from a surface IgM+lambda+ human B cell tumor line. The variants expressed a new lambda light chain. Both the original and the new lambda transcripts were present in the variant cells, but only the new one was expressed as a protein on the cell surface. Therefore, although the cell exhibited allelic exclusion and had only one Ig receptor at a time, the commitment to a particular light chain gene was reversible.
View details for Web of Science ID A1989U213700028
View details for PubMedID 2496466
ALTERNATIVE V-KAPPA GENE REARRANGEMENTS IN A MURINE B-CELL LYMPHOMA - AN EXPLANATION FOR IDIOTYPIC HETEROGENEITY
JOURNAL OF EXPERIMENTAL MEDICINE
1988; 168 (5): 1607-1620
Idiotype variants of 38C13, a murine B cell lymphoma, have been isolated by immunoselection with antiidiotype mAbs. The V region genes for the kappa light chains and mu heavy chains expressed by these tumor cells were sequenced and compared. There was no evidence for V region somatic point mutation in this tumor. However, while the heavy chain genes were all identical, the light chain genes were all different. The light chain genes of each variant were derived from the V kappa-Ox1 gene family and joined to J kappa 4, whereas the light chain gene of the parental tumor was derived from the V kappa 9 family and joined to J kappa 2. Two of the variants used the identical V kappa gene but differed by the inclusion of a variable number of additional nucleotides in the V/J joint. Thus, the idiotypic heterogeneity of this B cell lymphoma arises as a consequence of alternative light chain rearrangements rather than point mutation. This process repetitively uses members of the same V kappa gene family. Two of the variants use the identical V kappa and J kappa gene segments but differ by the presence of extra nucleotides at the V kappa/J kappa joint.
View details for Web of Science ID A1988Q904300008
View details for PubMedID 3141553
HYBRIDOMA FUSION CELL-LINES CONTAIN AN ABERRANT KAPPA TRANSCRIPT
1988; 25 (10): 991-995
The V region sequence of a non-productive kappa transcript from two myeloma fusion partners has been determined. This transcript has an aberrant VJ recombination site resulting in a translation stop site at position 105. It is variably expressed in hybridomas made from all fusion partners derived from the original MOPC-21 tumor. The amount of this transcript may greatly exceed levels of the productive light chain mRNA.
View details for Web of Science ID A1988Q584500005
View details for PubMedID 3146025
MUTATIONAL HOT SPOTS IN IG V-REGION GENES OF HUMAN FOLLICULAR LYMPHOMAS
JOURNAL OF EXPERIMENTAL MEDICINE
1988; 168 (2): 475-489
The genes coding for the Ig light chains expressed in two cases of human follicular lymphoma were cloned and sequenced. In each case, multiple independent isolates of the tumor population were compared. Although each tumor represented a single clone of B cells with a unique V/J joint, different cells within each tumor had accumulated multiple point mutations in the V gene during clonal expansion. Most of the mutations observed were silent, but some resulted in amino acid replacements. Identical silent mutations were often observed in independent isolates of each tumor. By combining the current data with VH sequences obtained previously from the same cells, it was apparent that the repetitive silent mutations could not be explained solely by a genealogic tree. Such mutations could represent hot spots whose tendency to mutate may be influenced by neighboring DNA sequences or by the methylation of specific cytosine residues.
View details for Web of Science ID A1988P872200002
View details for PubMedID 3045247
IDIOTYPE VACCINATION AGAINST MURINE B-CELL LYMPHOMA - HUMORAL AND CELLULAR-RESPONSES ELICITED BY TUMOR-DERIVED IMMUNOGLOBULIN-M AND ITS MOLECULAR SUBUNITS
JOURNAL OF IMMUNOLOGY
1987; 139 (8): 2825-2833
C3H/HeN mice were immunized with idiotypic immunoglobulin M (IgM) and its molecular subunits from the syngeneic 38C13 lymphoma. Immunization with idiotypic IgM (38C-Id) resulted in idiotype-specific humoral and cellular immunity and protection against a lethal tumor cell challenge. Heavy (H38C) and light (L38C) chains were isolated by electroelution from preparative polyacrylamide gels. Both of these immunogens induced significant resistance to a subsequent tumor challenge. Variable region immunogens, in the form of trpE-fusion proteins, were obtained by cloning heavy and light chain variable region genes into the expression plasmid pATH-11. Of these, only the trpE-VH38C immunogen yielded immune resistance to tumor challenge. Finally, the nucleic acid sequence of 38C-Id light chain was determined and, based on the corresponding amino acid sequence and an analysis of predicted secondary structure, a region of potential antigenicity in complementarity-determining region 3 was chosen for the production of a synthetic peptide. Vaccination with this synthetic peptide resulted in significant suppression of tumor growth. Analysis of the humoral and cellular immunity generated by these vaccines revealed the presence of antibodies reactive with native idiotypic IgM only in 38C-Id, H38C, and trpE-VH38C immune sera, although the latter two were not idiotype-specific. Idiotype-specific lymphocytes, which proliferated in response to native 38C-Id, were observed in all immune animals. With the exception of the fusion protein immunogens, conjugation to an immunogenic carrier protein (keyhole limpet hemocyanin or thyroglobulin) was required for optimal humoral and cellular responses.
View details for Web of Science ID A1987K320700049
View details for PubMedID 3498771
A RAPID METHOD FOR CLONING AND SEQUENCING VARIABLE-REGION GENES OF EXPRESSED IMMUNOGLOBULINS
1987; 54 (2-3): 167-173
A rapid procedure is described for cloning immunoglobulin V region genes from cells that express them. cDNA is synthesized from mRNA template using primers homologous to the immunoglobulin constant-region genes. Blunt-ended, double-stranded cDNA is obtained by sequential addition of enzymes to a single tube. The cDNA is inserted directly into the M13 vector, which is screened by plaque lifting for the presence of specific inserts. Screening probes can be generated from 32P-labeled single-stranded cDNAs generated from primers different from those used for cloning, or alternatively, from previously cloned V or C gene segments. The ease of cloning a cDNA V region is directly related to the abundance of Ig-specific mRNA within the cell of interest. This method minimizes the number of steps and the time needed to obtain accurate and complete sequences of any expressed Ig V region gene.
View details for Web of Science ID A1987J212400002
View details for PubMedID 3653692
- ANTI-IDIOTYPE ANTIBODIES REVEAL THE EXISTENCE OF SOMATIC MUTATION IN HUMAN B-CELL LYMPHOMA MONOGRAPHS IN ALLERGY 1987; 22: 194-203
SYNGENEIC ANTIIDIOTYPIC IMMUNE-RESPONSES TO A B-CELL LYMPHOMA - COMPARISON BETWEEN HEAVY-CHAIN HYPERVARIABLE REGION PEPTIDES AND INTACT IG AS IMMUNOGENS
JOURNAL OF EXPERIMENTAL MEDICINE
1985; 162 (1): 19-34
The nucleic acid sequence of the heavy chain variable region (VH) expressed by 38C13, a B cell tumor of C3H origin, was determined by a combination of direct (messenger RNA) mRNA sequencing by primer extension and complementary DNA (cDNA) isolation and sequencing in M13. The VH amino acid sequence was deduced, and hypervariable regions were identified. From an analysis of predicted secondary structure, regions of predicted antigenicity were chosen, and a series of synthetic peptides corresponding to CDR2 and CDR3 (complementarity-determining region) were produced. These peptides were coupled to protein carriers and used to immunize syngeneic C3H mice. All peptides gave rise to a vigorous antibody response. However, only the CDR3 peptides induced antibodies that crossreacted with the isolated H chain protein. Only one CDR3 peptide induced antibody-producing clones, isolated as hybridomas, that reacted with the intact IgM protein. However, the appearance of these clones was a low-frequency event. All antibodies reacting with the H chain or the intact IgM protein were idiotypically specific for 38C13. These monoclonal antiidiotype (anti-Id) antibodies, raised against CDR3 peptides, gave strong reactions in enzyme-linked immunosorbent assays and immunoblots, but they were of low affinity compared to syngeneic anti-Id raised against the intact IgM protein. Moreover, while the intact IgM was capable of inducing tumor immunity, the CDR peptides were not able to do so.
View details for Web of Science ID A1985ALW4900002
View details for PubMedID 3925067
THE NUCLEOTIDE AND AMINO-ACID CODING SEQUENCE OF A GENE FOR H-1 HISTONE THAT INTERACTS WITH EUCHROMATIN - THE EARLY EMBRYONIC H-1 GENE OF THE SEA-URCHIN STRONGYLOCENTROTUS-PURPURATUS
JOURNAL OF BIOLOGICAL CHEMISTRY
1982; 257 (16): 9438-9443
We have determined the nucleotide sequence of the gene that codes for an H1 histone associated with euchromatin in the sea urchin Strongylocentrotus purpuratus. The gene codes for a protein of 205 amino acids. The nucleotide sequence of this gene is homologous to the sequence of H1 mRNA that is expressed during early embryonic development. We have compared the nucleotide and protein coding sequences of this H1 gene to those of the early H1 histone gene of the sea urchin Psammechinus miliaris. There is considerable drift by nucleotide substitution between the two genes randomly distributed across the mRNA coding region. Despite this divergence of nucleotide sequence, there are local constraints on amino acid substitutions throughout the molecule and especially in its central region. We have also compared the amino acid sequence in this central hydrophobic region of the euchromatic S. purpuratus H1 histone to the same region in H1 and H5 histones associated with heterochromatin. We show that certain amino acids are conserved and aligned in frameworks in all the sequenced H1 proteins.
View details for Web of Science ID A1982PC82800040
View details for PubMedID 7107576
MONOCISTRONIC TRANSCRIPTION IS THE PHYSIOLOGICAL MECHANISM OF SEA-URCHIN EMBRYONIC HISTONE GENE-EXPRESSION
MOLECULAR AND CELLULAR BIOLOGY
1981; 1 (7): 661-671
We have examined histone gene expression during the early stages of sea urchin embryogenesis. The five histone genes expressed at that time are contained in tandem repetitive segments. It has been suggested that adjacent coding regions and their intervening spacer sequences are transcribed into large polycistronic messenger ribonucleic acid (RNA) precursors. We have subcloned into pBR322 deoxyribonucleic acid (DNA) sequences mapping either in the coding region, the 5' spacer, or the 3' spacer of the H2B histone gene. These clones were used to produce radioiodinated hybridization probes. We measured the steady-state quantity of H2B messenger RNA as well as spacer-specific RNA in the total RNA from embryos taken at various stages of development from fertilization to hatching of blastulae (0 to 22 h post-fertilization). Small amounts of RNA hybridizing to both spacer probes could be found. However, we show that these RNAs form mismatched hybrids with the spacer DNA and therefore cannot originate from the spacers present in the histone genes. We conclude that there is no detectable transcription of the spacer regions on either side of the H2B histone gene. The detection limit for RNA complementary to the 5' spacer sequence corresponds to a maximum of about three RNA molecules per cell, an amount shown to be far less than the projected steady-state pool size of a putative polycistronic transcript, if such a precursor were to be the obligatory transcript of the histone genes. (This conclusion was derived by using the known rates of production of H2B mRNA throughout early development [R. E. Maxson and F. H. Wilt, Dev. Biol., in press].) The physiologically relevant transcript of the histone genes in early development is therefore monocistronic and probably identical to the messenger RNA itself.
View details for Web of Science ID A1981LW62900009
View details for PubMedID 9279379
LEADER SEQUENCES OF STRONGYLOCENTROTUS-PURPURATUS HISTONE MESSENGER-RNAS START AT A UNIQUE HEPTANUCLEOTIDE COMMON TO ALL 5 HISTONE GENES
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA-BIOLOGICAL SCIENCES
1980; 77 (3): 1265-1269
We have determined the sequence of the untranslated leader nucleotides of all five histone mRNAs from Strongylocentrotus purpuratus by the dideoxy chain termination method. Total polysomal RNA from sea urchin embryos was used as a substrate for cDNA synthesis primed by specific DNA restriction fragments. Each of the primers was derived from the 5'-terminal part of the coding region for a different histone protein. The five histone mRNA leader sequences are different in length and primary structure. The 5' termini of all five histone mRNAs coincide with the unique heptanucleotide Py-Py-A-T-T-C-Pu in genomic DNA. This sequence, which defines the start of the individual histone mRNAs, is preceded by the A+T-rich octanucleotide identified in front of all eukaryotic structural genes where sequences have been determined to date.
View details for Web of Science ID A1980JL81400003
View details for PubMedID 6154927
- SEQUENCE OF THE 5'-END OF STRONGYLOCENTROTUS-PURPURATUS H2B HISTONE MESSENGER RNA AND ITS LOCATION WITHIN HISTONE DNA NATURE 1979; 279 (5715): 737-739
RAPID PURIFICATION OF BIOLOGICALLY-ACTIVE INDIVIDUAL HISTONE MESSENGER-RNAS BY HYBRIDIZATION TO CLONED DNA LINKED TO CELLULOSE
1979; 18 (1): 208-213
We describe a rapid and simple method for the purification of biologically active messenger RNAs. The method allows the isolation in a few hours of specific mRNAs from either whole cell or polysomal RNA even if the RNA represents less than 1% of the starting molecules. We used, as a model, cloned sea urchin (Strongylocentrotus purpuratus) histone gene fragments linked to cellulose by the method of B. E. Noyes & G. R. Stark (1975) Cell 5, 301--310) as hybridization probes to isolate specific histone mRNAs from whole cell and polysomal RNA extracts. RNAs isolated in this manner maintain their biological activity, serving as templates for histone proteins in a wheat-germ, cell-free protein translation system. In addition, radiolabeled histone-specific RNA purified from cleavage stage sea urchin embryos, pulse labeled for short periods of time and analyzed on denaturing polyacrylamide gels, was the same size as mature histone mRNA's.
View details for Web of Science ID A1979GD90000032
View details for PubMedID 369596
SEA-URCHIN NUCLEI USE RNA POLYMERASE-II TO TRANSCRIBE DISCRETE HISTONE RNAS LARGER THAN MESSENGERS
1978; 15 (1): 151-162
RNA transcribed in isolated sea urchin nuclei and assayed by hybridization to histone genes cloned in E. coli contains sequences homologous to each of the five histone genes. Histone RNA is synthesized exclusively from the same DNA strand which is the template in vivo. Synthesis of the histone gene transcripts is sensitive to alpha-amanitin concentrations which inhibit RNA polymerase II activity. The fraction of histone RNA synthesized in vitro is comparable at two developmental stages to the fraction synthesized in vivo. The nuclear histone transcripts contain sequences homologous to spacer DNA regions present between the coding regions of the 6500 base pair (bp) histone gene repeat unit. The transcription of spacer sequences was demonstrated by hybridization of the nuclear transcripts to subcloned spacer DNA. Although the bulk of the RNA transcripts are greater than 2000 bases long, the histone-specific transcripts are of discrete sizes ranging from 100 bases to about 1100 bases long. Each histone gene hybridizes with at least one of the larger transcripts and with a different subset of smaller RNAs. We do not detect any giant polycistronic transcript spanning the entire histone repeat unit.
View details for Web of Science ID A1978FQ44400014
View details for PubMedID 699039
A CpG-loaded tumor cell vaccine induces antitumor CD4(+) T cells that are effective in adoptive therapy for large and established tumors
AMER SOC HEMATOLOGY. 2011: 118-127
We designed a whole tumor cell vaccine by "loading" lymphoma tumor cells with CG-enriched oligodeoxynucleotide (CpG), a ligand for the Toll-like receptor 9 (TLR9). CpG-loaded tumor cells were phagocytosed, delivering both tumor antigen(s) and the immunostimulatory CpG molecule to antigen-presenting cells (APCs). These APCs then expressed increased levels of costimulatory molecules and induced T-cell immunity. TLR9 was required in the APCs but not in the CpG-loaded tumor cell. We demonstrate that T cells induced by this vaccine are effective in adoptive cellular therapy for lymphoma. T cells from vaccinated mice transferred into irradiated, syngeneic recipients protected against subsequent lymphoma challenge and, remarkably, led to regression of large and established tumors. This therapeutic effect could be transferred by CD4(+) but not by CD8(+) T cells. A CpG-loaded whole-cell vaccination is practical and has strong potential for translation to the clinical setting. It is currently being tested in a clinical trial of adoptive immunotherapy for mantle-cell lymphoma.
View details for DOI 10.1182/blood-2010-06-288456
View details for Web of Science ID 000285963900021
View details for PubMedID 20876455
Distinct CD81 domains control CD19 maturation in B cells
FEDERATION AMER SOC EXP BIOL. 2005: A881-A881
View details for Web of Science ID 000227610706244
CD81 and T cells enhances T-B cell interactions leading to antigen-specific Th2 responses
FEDERATION AMER SOC EXP BIOL. 2001: A1030-A1030
View details for Web of Science ID 000167454201828
Preferential expression of the VH1-69 gene in an anti-hepatitis C virus (HCV) immune response in an HCV-infected individual
FEDERATION AMER SOC EXP BIOL. 2000: A1122-A1122
View details for Web of Science ID 000086643101237
Reduced allergen-induced airway hyperreactivity in CD81 deficient mice
FEDERATION AMER SOC EXP BIOL. 2000: A1067-A1067
View details for Web of Science ID 000086643100914