Master of Science, Unlisted University (2007)
Bachelor of Science, Unlisted University (2005)
Doctor of Philosophy, University of California Davis (2012)
Cancer immunobiology and the development of immunological treatments against tumorigenesis/cancer.
Natural Killer (NK) cell-based immunotherapies and NK biology.
Hematopoietic stem cell transplanation
Natural killer (NK) cells express inhibitory receptors with varied binding affinities to specific major histocompatibility complex class I (MHC-I) haplotypes. NK cells can be classified as licensed or unlicensed based on their ability or inability to bind MHC-I, respectively. The role of donor vs host MHC on their development after allogeneic hematopoietic stem cell transplantation (allo-HSCT) is not known. Following reciprocal MHC-disparate allogeneic transplants and during de novo NK-cell recovery, depletion of the licensed and not unlicensed population of NK cells as determined by the licensing patterns of donor MHC-I haplotypes, resulted in significantly increased susceptibility to murine cytomegalovirus (MCMV) infection. A corresponding expansion of the licensed Ly49H(+) NK cells occurred with greater interferon γ production by these cells than unlicensed NK cells in the context of donor MHC-I. Thus, NK licensing behavior to MCMV corresponds to the donor, and not recipient, MHC haplotype after allo-HSCT in mice.
View details for DOI 10.1182/blood-2013-02-483503
View details for Web of Science ID 000323394300030
View details for PubMedID 23818546
NK subsets have activating and inhibitory receptors that bind MHC-I. Ly49A is a mouse inhibitory receptor that binds with high affinity to H2(d) in both a cis- and trans-manner. Ly49A cis-associations limit trans-interactions with H2(d)-expressing targets as well as mAb binding. We demonstrate that cis-interactions affect mAb effector functions. In vivo administration of anti-Ly49A depleted NK cells in H2(b) but not H2(d) mice. Despite lack of depletion, in vivo treatment with anti-Ly49A reduced NK killing capabilities and inhibited activation, partially due to its agonistic effect. These data explain the previously described in vivo effects on bone marrow allograft rejection observed with anti-Ly49A treatment in H2(d)-haplotype mice. However, prior treatment of mice with poly(I:C) or mouse CMV infection resulted in increased Ly49A expression and Ly49A(+) NK cell depletion in H2(d) mice. These data indicate that, although Ly49 mAbs can exert similar in vivo effects in mice with different MHC haplotypes, these effects are mediated via different mechanisms of action correlating with Ly49A expression levels and can be altered within the same strain contingent on stimuli. This illustrates the marked diversity of mAb effector functions due to the regulation of the level of expression of target Ags and responses by stimulatory incidents such as infection.
View details for DOI 10.4049/jimmunol.1300202
View details for Web of Science ID 000321260100021
View details for PubMedID 23752612
Natural killer (NK) cells show differential functionality based on their capability of binding to self-MHC consistent with licensing. Here we show in vivo confirmation of the physiologic effects of licensing with differential effects of NK subsets on anti-murine cytomegalovirus (anti-MCMV) responses after syngeneic hematopoietic stem cell transplantation (HSCT) or regulatory T-cell (Treg) depletion. After HSCT, depletion of licensed NK cells led to far greater viral loads in target organs early after infection compared with nondepleted and unlicensed depleted mice. There was a preferential expansion of licensed, C-type lectin-like activating receptor Ly49H+ NK cells with increased IFNγ production after infection in nondepleted mice post-HSCT and after Treg depletion. Adoptive transfer of licensed NK subsets into immunodeficient hosts provided significantly greater MCMV resistance compared with transfer of total NK populations or unlicensed subsets. In non-HSCT mice, only concurrent depletion of Tregs or TGF-β neutralization resulted in detection of NK licensing effects. This suggests that licensed NK cells are the initial and rapidly responding population of NK cells to MCMV infection, but are highly regulated by Tregs and TGF-β.
View details for DOI 10.1073/pnas.1218767110
View details for Web of Science ID 000318682300063
View details for PubMedID 23589894
Natural killer (NK) cells can mediate the rejection of bone marrow allografts and exist as subsets based on expression of inhibitory/activating receptors that can bind MHC. In vitro data have shown that NK subsets bearing Ly49 receptors for self-MHC class I have intrinsically higher effector function, supporting the hypothesis that NK cells undergo a host MHC-dependent functional education. These subsets also play a role in bone marrow cell (BMC) allograft rejection. Thus far, little in vivo evidence for this preferential licensing across mouse strains with different MHC haplotypes has been shown. We assessed the intrinsic response potential of the different Ly49(+) subsets in BMC rejection by using β2-microglobulin deficient (β2m(-/-)) mice as donors. Using congenic and allogeneic mice as recipients and depleting the different Ly49 subsets, we found that NK subsets bearing Ly49s, which bind "self-MHC" were found to be the dominant subset responsible for β2m(-/-) BMC rejection. This provides in vivo evidence for host MHC class I-dependent functional education. Interestingly, all H2(d) strain mice regardless of background were able to resist significantly greater amounts of β2m(-/-), but not wild-type BMC than H2(b) mice, providing evidence that the rheostat hypothesis regarding Ly49 affinities for MHC and NK-cell function impacts BMC rejection capability.
View details for DOI 10.1182/blood-2011-08-374314
View details for Web of Science ID 000300420900036
View details for PubMedID 22184406
Immune deficiency immediately following bone marrow transplantation (BMT) increases susceptibility to opportunistic infections as well as tumor relapse. Natural Killer (NK) cells play important roles in the resistance to virally infected and transformed cells. Interleukin (IL)-15 has been shown to be essential for NK cell development and survival. We administered human (h) IL-15 cDNA (pIL-15) via hydrodynamic delivery to murine recipients undergoing congenic BMT to determine its effects on NK cell reconstitution. Hydrodynamic pIL-15 delivery resulted in high levels of hIL-15 protein in the serum that lasted for several days and then quickly declined. The appearance of hIL-15 was followed by a significant increase of mature donor-derived NK cells within the bone marrow, spleens, and livers of the treated recipients. No accumulation of immature NK cell progenitors was observed. The NK cells from IL-15-treated recipients displayed an activated phenotype and were lytically active toward tumor targets in vitro to a similar degree as did those cells from recipients treated with control plasmid. This suggests that the predominant effect of IL-15 was a quantitative increase in total NK cell numbers and not qualitative changes in NK cell functions. No toxicities or adverse effects were observed. Studies performed in transplanted mice bearing renal carcinoma tumors demonstrated that this mode of hIL-15 gene delivery resulted in increased antitumor responses. These results support the use of cytokine gene transfer-based regimens as a platform to augment NK cell recovery after BMT.
View details for DOI 10.1016/j.bbmt.2011.08.023
View details for Web of Science ID 000300472700006
View details for PubMedID 21906575
Natural killer (NK) cell subsets can be defined by the differential expression of inhibitory receptors for MHC class I molecules. Early after congenic HSCT, we found that Ly49G2(high) single-positive NK cells repopulated, displayed an activated phenotype, and were highly cytolytic. Over time, this subset was replaced with NK cells with a normal pattern of Ly49 expression. Treatment of mice with IL-2 also resulted in the rapid expansion of these Ly49G2(high) single-positive NK cells. Only the Ly49g (Klra7) Pro1 transcript was highly induced in both HSCT- and IL-2-treated recipients. MHC-independent expansion of the Ly49G2(+) subset was also observed after Listeria monocytogenes or mouse cytomegalovirus infection. Our data indicate that during reconstitution after HSCT and various activation stimuli, Ly49G2(+) NK cells represent the "first-responder" NK cells, which occur independently of NK-cell licensing via Ly49-MHC interactions. These data suggest that the inhibitory Ly49G2 receptor represents an activation marker on mouse NK cells under various conditions.
View details for DOI 10.1182/blood-2010-11-316653
View details for Web of Science ID 000292244000011
View details for PubMedID 21498673
Interleukin (IL)-2 has been extensively examined to promote clinical T and natural killer (NK) cell responses. Regulatory T cells (Tregs) have been shown to regulate many aspects of the immune system, including NK cell-mediated responses. We have demonstrated that in vivo administration of IL-2 led to activation and expansion of both NK cells and immunosuppressive Tregs. Therefore, we attempted to augment NK cell antitumor effects by concurrently depleting Tregs using anti-CD25. Increased NK cell activation by IL-2 was found to be correlated with an increase in classical, short-term NK cell in vitro killing assays regardless of the depletion of Tregs. But when splenocytes of the treated mice were used in long-term tumor outgrowth experiments, we observed that prior depletion of Tregs from IL-2 administration led to improved antitumor effects compared with either treatment alone. Importantly, these in vitro data are correlated with subsequent in vivo survival of leukemia-bearing mice, in which co-treatment of IL-2 with anti-CD25 led to significantly improved survival compared with mice treated with either IL-2 alone or with Treg depletion. Prior depletion of NK1.1(+) cells, but not of CD8(+) cells, completely abrogated all antitumor effects mediated by IL-2 and anti-CD25 combination therapy. These findings demonstrate that superior NK cell-mediated antileukemic effects can be achieved with IL-2 administration and concurrent depletion of CD25(+) cells.
View details for DOI 10.1016/j.bbmt.2008.08.001
View details for Web of Science ID 000259669100002
View details for PubMedID 18804038