Bio

Clinical Focus


  • Gastroenterology/Nutrition/Hepatology, Pediatric
  • Pediatric Gastroenterology

Academic Appointments


Professional Education


  • Medical Education:Vanderbilt University School of Medicine (1979) TN
  • Residency:Boston City Hospital (1982) MA
  • Board Certification: Pediatrics, American Board of Pediatrics (1987)
  • Fellowship:Stanford University School of Medicine (1990) CA
  • Fellowship:Massachusetts General Hospital (1986) MA
  • Internship:Boston City Hospital (1979) MA

Research & Scholarship

Current Research and Scholarly Interests


Viral gastroenteritis is the single most important cause of diarrhea in infancy world-wide and accounts for enormous morbidity and mortality in children in both the developing and developed worlds. Our laboratory is interested in the pathogenesis of viral gastroenteritis, specifically in intestinal factors which are critical to the outcome of rotavirus infection which range from asymptomatic viral shedding to severe clinical disease. Previous observations have shown that rotavirus has both a narrowly defined tissue tropism, essentially mature enterocytes of the intestinal villus tip, and a fairly narrow host range restriction, causing disease mainly in suckling animals and usually only with viral strains derived from the same host species. We believe that local gastrointestinal factors determine the outcome of rotavirus infection. Specific studies include:

1) Cell receptors for rotavirus are being identified and characterized by a variety of biochemical and immunological approaches.
2) Rotavirus penetration of target cell membranes. Work from our lab has shown that this is a critical step in determing host cell susceptibility to the virus.
3) Role of enteric secretions on rotavirus pathogeneis. Rotavirus requires exogenous trypsin for replication. We are studying the effects of gastrointestinal proteases and acid secretion on rotavirus pathogeneis in vitro and in vivo.
4) Role of intestinal mucins as a defense mechanism against rotavirus.
5) Mucosal immunity and protection from enteric viral pathogens.

Teaching

2013-14 Courses


Publications

Journal Articles


  • Infliximab for the treatment of granulomatous peritonitis. Digestive diseases and sciences Yeh, A. M., Kerner, J., Hillard, P., Bass, D. 2013; 58 (12): 3397-3399

    View details for DOI 10.1007/s10620-013-2726-6

    View details for PubMedID 23817923

  • Cost-effectiveness of Universal Serologic Screening to Prevent Nontraumatic Hip and Vertebral Fractures in Patients With Celiac Disease. Clinical gastroenterology and hepatology Park, K. T., Tsai, R., Wang, L., Khavari, N., Bachrach, L., Bass, D. 2013; 11 (6): 645-653

    Abstract

    Patients with asymptomatic or poorly managed celiac disease can experience bone loss, placing them at risk for hip and vertebral fractures. We analyzed the cost-effectiveness of universal serologic screening (USS) vs symptomatic at-risk screening (SAS) strategies for celiac disease because of the risk of nontraumatic hip and vertebral fractures if untreated or undiagnosed.We developed a lifetime Markov model of the screening strategies, each with male or female cohorts of 1000 patients who were 12 years old when screening began. We screened serum samples for levels of immunoglobulin A, compared with tissue transglutaminase and total immunoglobulin A, and findings were confirmed by mucosal biopsy. Transition probabilities and quality of life estimates were obtained from the literature. We used generalizable cost estimates and Medicare reimbursement rates and ran deterministic and probabilistic sensitivity analyses.For men, the average lifetime costs were $8532 and $8472 for USS and SAS strategies, respectively, corresponding to average quality-adjusted life year gains of 25.511 and 25.515. Similarly for women, costs were $11,383 and $11,328 for USS and SAS strategies, respectively, corresponding to quality-adjusted life year gains of 25.74 and 25.75. Compared with the current standard of care (SAS), USS produced higher average lifetime costs and lower quality of life for each sex. Deterministic and probabilistic sensitivity analyses showed that the model was robust to realistic changes in all the variables, making USS cost-ineffective on the basis of these outcomes.USS and SAS are similar in lifetime costs and quality of life, although the current SAS strategy was overall more cost-effective in preventing bone loss and fractures among patients with undiagnosed or subclinical disease. On the basis of best available supportive evidence, it is more cost-effective to maintain the standard celiac screening practices, although future robust population-based evidence in other health outcomes could be leveraged to reevaluate current screening guidelines.

    View details for DOI 10.1016/j.cgh.2012.12.037

    View details for PubMedID 23357490

  • Cost-Effectiveness of Early Colectomy With Ileal Pouch-Anal Anastamosis Versus Standard Medical Therapy in Severe Ulcerative Colitis ANNALS OF SURGERY Park, K. T., Tsai, R., Perez, F., Cipriano, L. E., Bass, D., Garber, A. M. 2012; 256 (1): 117-124

    Abstract

    Inflammatory bowel diseases are costly chronic gastrointestinal diseases. We aimed to determine whether immediate colectomy with ileal pouch-anal anastamosis (IPAA) after diagnosis of severe ulcerative colitis (UC) was cost-effective compared to the standard medical therapy.We created a Markov model simulating 2 cohorts of 21-year-old patients with severe UC, following them until 100 years of age or death, comparing early colectomy with IPAA strategy to the standard medical therapy strategy. Deterministic and probabilistic analyses were performed.Standard medical care accrued a discounted lifetime cost of $236,370 per patient. In contrast, early colectomy with IPAA accrued a discounted lifetime cost of $147,763 per patient. Lifetime quality-adjusted life-years gained (QALY-gained) for standard medical therapy was 20.78, while QALY-gained for early colectomy with IPAA was 20.72. The resulting incremental cost-effectiveness ratio (?costs/?QALY) was approximately $1.5 million per QALY-gained. Results were robust to one-way sensitivity analyses for all variables in the model. Quality-of-life after colectomy with IPAA was the most sensitive variable impacting cost-effectiveness. A low utility value of less than 0.7 after colectomy with IPAA was necessary for the colectomy with IPAA strategy to be cost-ineffective.Under the appropriate clinical settings, early colectomy with IPAA after diagnosis of severe UC reduces health care expenditures and provides comparable quality of life compared to exhaustive standard medical therapy.

    View details for DOI 10.1097/SLA.0b013e3182445321

    View details for Web of Science ID 000306083300020

    View details for PubMedID 22270693

  • Cost-effectiveness Analysis of Adjunct VSL#3 Therapy Versus Standard Medical Therapy in Pediatric Ulcerative Colitis JOURNAL OF PEDIATRIC GASTROENTEROLOGY AND NUTRITION Park, K. T., Perez, F., Tsai, R., Honkanen, A., Bass, D., Garber, A. 2011; 53 (5): 489-496

    Abstract

    Inflammatory bowel diseases (IBDs) are costly chronic gastrointestinal diseases, with pediatric IBD representing increased costs per patient compared to adult disease. Health care expenditures for ulcerative colitis (UC) are >$2 billion annually. It is not clear whether the addition of VSL#3 to standard medical therapy in UC induction and maintenance of remission is a cost-effective strategy.We performed a systematic review of the literature and created a Markov model simulating a cohort of 10-year-old patients with severe UC, studying them until 100 years of age or death. We compared 2 strategies: standard medical therapy versus medical therapy + VSL#3. For both strategies, we assumed that patients progressed through escalating therapies--mesalamine, azathioprine, and infliximab--before receiving a colectomy + ileal pouch anal anastamosis (IPAA) if the 3 medical therapy options were exhausted. The primary outcome measure was the incremental cost-effectiveness ratio (ICER), defined as the difference of costs between strategies for each quality-adjusted life-year (QALY) gained. One-way sensitivity analyses were performed on variables to determine the key variables affecting cost-effectiveness.Standard medical care accrued a lifetime cost of $203,317 per patient, compared to $212,582 per patient for medical therapy + VSL#3. Lifetime QALYs gained was comparable for standard medical therapy and medical therapy + VSL#3 at 24.93 versus 25.05, respectively. Using the definition of ICER <50,000/QALY as a cost-effective intervention, medical therapy + VSL#3 produced an ICER of $79,910 per QALY gained, making this strategy cost-ineffective. Sensitivity analyses showed that 4 key parameters could affect the cost-effectiveness of the 2 strategies: cost of colectomy + IPAA, maintenance cost after surgery, probability of developing pouchitis after surgery, and the quality of life after a colectomy + IPAA. High surgical and postsurgical costs, a high probability of developing pouchitis, and a low quality of life after a colectomy + IPAA could make adjunct VSL#3 use a cost-effective strategy.Given present data, adjunct VSL#3 use for pediatric UC induction and maintenance of remission is not cost-effective, although several key parameters could make this strategy cost-effective. The quality of life after an IPAA is the single most important variable predicting whether this procedure benefits patients over escalating standard medical therapy.

    View details for DOI 10.1097/MPG.0b013e3182293a5e

    View details for Web of Science ID 000296383000007

    View details for PubMedID 21694634

  • Acute Liver Failure and Aplastic Anemia in an 11-Year-Old Girl DIGESTIVE DISEASES AND SCIENCES Yeh, A. M., Mojtahed, A., Bass, D. 2011; 56 (8): 2237-2240

    View details for DOI 10.1007/s10620-011-1678-y

    View details for Web of Science ID 000293296100006

    View details for PubMedID 21442323

  • Inflammatory Bowel Disease-Attributable Costs and Cost-effective Strategies in the United States: A Review INFLAMMATORY BOWEL DISEASES Park, K. T., Bass, D. 2011; 17 (7): 1603-1609

    Abstract

    The United States spends more for healthcare than any other country in the world. With the rising prevalence of both Crohn's disease and ulcerative colitis, inflammatory bowel disease (IBD) represents the leading chronic gastrointestinal disease with increasing healthcare expenditures in the US. IBD costs have shifted from inpatient to outpatient care since the introduction of biologic therapies as the standard of care. Gastroenterologists need to be aware of the national cost burden of IBD and clinical practices that optimize cost-efficiency. This investigation offers a systematic review of the economics of IBD and evidence-based strategies for cost-effective management.

    View details for DOI 10.1002/ibd.21488

    View details for Web of Science ID 000292415200017

    View details for PubMedID 21053357

  • Immunophenotyping of Peripheral Eosinophils Demonstrates Activation in Eosinophilic Esophagitis JOURNAL OF PEDIATRIC GASTROENTEROLOGY AND NUTRITION Tammie Nguyen, T., Gernez, Y., Fuentebella, J., Patel, A., Tirouvanziam, R., Reshamwala, N., Bass, D., Berquist, W. E., Cox, K. L., Kerner, J. A., Nadeau, K. C. 2011; 53 (1): 40-47

    Abstract

    Eosinophilic esophagitis (EoE) is a chronic inflammatory disorder characterized by upper gastrointestinal symptoms and the presence of high numbers of eosinophils in the esophagus. Although eosinophils in the esophagus have been found to be activated in subjects with EoE, detailed studies of intracellular signaling pathways involved in the mechanism of activation of eosinophils in EoE have heretofore been limited. The aim of the study was to assess whether any surface molecules or transcription factors are activated in peripheral eosinophils in subjects with EoE.Eosinophils and CD3+ lymphocytes were identified directly from 50 ?L of whole blood of EoE and control subjects. Using Hi-FACS, levels of surface activation markers, including CD66b, and intracellular phosphoepitopes, including phosphorylated forms of signal transducer and activator of transcription (phospho-STAT) 1 and 6, were measured within each cell subset.Levels of surface CD66b as well as levels of intracellular phospho-STAT1 and phospho-STAT6 in peripheral blood eosinophils were significantly higher for untreated subjects with EoE vs healthy controls (P < 0.05). Levels of phospho-STAT1 and phospho-STAT6 in peripheral blood eosinophils were lower in subjects with EoE on therapy versus untreated subjects with EoE (P < 0.05).Levels of phospho-STAT1 and phospho-STAT6, transcription factors involved in inflammatory processes, were both significantly higher in peripheral eosinophils from untreated (ie, newly diagnosed) subjects with EoE versus subjects with EoE on therapy, healthy controls. Blood-based measurements of CD66b and phospho-STAT levels in peripheral eosinophils may be beneficial for identifying EoE.

    View details for DOI 10.1097/MPG.0b013e318212647a

    View details for Web of Science ID 000291925500006

    View details for PubMedID 21694534

  • Proton Pump Inhibitor Treatment for Congenital Chloride Diarrhea DIGESTIVE DISEASES AND SCIENCES Pieroni, K. P., Bass, D. 2011; 56 (3): 673-676

    View details for DOI 10.1007/s10620-010-1491-z

    View details for Web of Science ID 000287501500008

    View details for PubMedID 21127979

  • Analysis of clinical variables associated with tolerance in pediatric liver transplant recipients PEDIATRIC TRANSPLANTATION Talisetti, A., Hurwitz, M., Sarwal, M., Berquist, W., Castillo, R., Bass, D., Concepcion, W., Esquivel, C. O., Cox, K. 2010; 14 (8): 976-979

    Abstract

    Tolerance has been defined as stable graft function off IMS. We reviewed the data of 369 pediatric liver transplant patients to examine demographic differences that may have a PV of pediatric LT tolerance. Of the 369 patients, 280 patients were stable with detectable blood levels of IMS agents and with good graft function without biopsy proven REJ > 1 yr posttransplantation, 18 patients were noted to be TOL off IMS, 27 patients were taking MIS with drug levels below detectable range by standard laboratory parameters, and 44 patients developed one or more episodes of biopsy proven acute or chronic REJ > 1 yr post-transplantation. Variables, including percentage of biliary atresia, type of transplanted organ, history of EBV infection, patient and donor gender, and ABO blood type mismatch between recipient and donor did not have PV of tolerance. Average age in years was 1.37 ± 1.53 (0.3-4.9) for TOL, 1.14 ± 0.89 (0.4-3.1) for MIS and 3.35 ± 4.45 (0.3-16) for REJ. Age difference of TOL/MIS vs. REJ was significant (p =0.002) and TOL vs. REJ was significant (0.01). Age at the time of transplantation is an important predictor in the development of pediatric LT tolerance.

    View details for DOI 10.1111/j.1399-3046.2010.01360.x

    View details for Web of Science ID 000285229500007

    View details for PubMedID 21108705

  • Increased HLA-DR Expression on Tissue Eosinophils in Eosinophilic Esophagitis JOURNAL OF PEDIATRIC GASTROENTEROLOGY AND NUTRITION Patel, A. J., Fuentebella, J., Gernez, Y., Nguyen, T., Bass, D., Berquist, W., Cox, K., Sibley, E., Kerner, J., Nadeau, K. 2010; 51 (3): 290-294

    Abstract

    The aim of the study was to investigate whether eosinophils have increased human leukocyte antigen (HLA)-DR expression in subjects with eosinophilic esophagitis (EoE) compared with controls.Patients who were undergoing an upper endoscopy with biopsies for suspected gastroesophageal reflux disease (GERD) or EoE at Lucile Packard Children's Hospital were enrolled. In total, the blood and tissue samples of 10 healthy controls (HC), 11 subjects with GERD, and 10 with EoE were studied. Multiple tissue staining to identify eosinophils (via eosinophil cationic protein-clone EG2) and major histocompatibility complex class II cell surface receptors (via HLA-DR) was performed via immunohistochemistry. The peripheral blood was analyzed using flow cytometry to detect eosinophil HLA-DR expression among these subjects.In the tissue, a greater proportion of eosinophils expressed HLA-DR among the subjects with EoE (mean 0.83 +/- 0.14, n = 9) relative to those with GERD (mean 0.18 +/- 0.19, n = 8, P < 0.01) and HC (mean 0.18 +/- 0.13, n = 6, P < 0.01). In total, 6 participants (4 HC subjects and 2 subjects with GERD) did not have any eosinophils identified on tissue staining and were unable to be included in the present statistical analysis. In the blood, there was no statistically significant difference in eosinophil HLA-DR expression among HC subjects (mean 415 +/- 217, n = 6), subjects with GERD (mean 507 +/- 429, n = 2), and those with EoE (mean 334 +/- 181, n = 6).These data demonstrate that the eosinophils from the esophagus of subjects with EoE have increased HLA-DR expression within this tissue.

    View details for DOI 10.1097/MPG.0b013e3181e083e7

    View details for Web of Science ID 000281453500008

    View details for PubMedID 20639774

  • Increased Number of Regulatory T Cells in Children With Eosinophilic Esophagitis JOURNAL OF PEDIATRIC GASTROENTEROLOGY AND NUTRITION Fuentebella, J., Patel, A., Nguyen, T., Sanjanwala, B., Berquist, W., Kerner, J. A., Bass, D., Cox, K., Hurwitz, M., Huang, J., Nguyen, C., Quiros, J. a., Nadeau, K. 2010; 51 (3): 283-289

    Abstract

    There are limited data on the role of regulatory T cells (Treg) in the disease pathology of eosinophilic esophagitis (EoE). We tested the differences in Treg in subjects with EoE compared with those with gastroesophageal reflux disease (GERD) and healthy controls (HC).Pediatric patients evaluated by endoscopy were recruited for our study. Participants were categorized into 3 groups: EoE, GERD, and HC. RNA purified from esophageal biopsies were used for real-time quantitative polymerase chain reaction assays and tested for forkhead box P3 (FoxP3) mRNA expression. Treg were identified as CD4+CD25hiCD127lo cells in peripheral blood and as CD3+/FoxP3+cells in esophageal tissue.Forty-eight subjects were analyzed by real-time quantitative polymerase chain reaction: EoE (n = 33), GERD (n = 7), and HC (n = 8). FoxP3 expression was higher by up to 1.5-fold in the EoE group compared with the GERD and HC groups (P < 0.05). Protein levels of FoxP3 in blood and tissue were then investigated in 21 subjects: EoE (n = 10), GERD (n = 6), and HC (n = 5). The percentage of Treg and their subsets in peripheral blood were not significant between groups (P > 0.05). The amount of Treg in esophageal tissue was significantly greater in the EoE group (mean 10.7 CD3+/FoxP3+cells/high power field [HPF]) compared with the other groups (GERD, mean 1.7 CD3+/FoxP3+cells/HPF and HC, mean 1.6 CD3+/FoxP3+cells/HPF) (P < 0.05).We show that Treg are increased in esophageal tissue of EoE subjects compared with GERD and HC subjects. The present study illustrates another possible mechanism involved in EoE that implicates impairment of immune homeostasis.

    View details for DOI 10.1097/MPG.0b013e3181e0817b

    View details for Web of Science ID 000281453500007

    View details for PubMedID 20639775

  • Eotaxin and FGF enhance signaling through an extracellular signal-related kinase (ERK)-dependent pathway in the pathogenesis of Eosinophilic esophagitis. Allergy, asthma, and clinical immunology : official journal of the Canadian Society of Allergy and Clinical Immunology Huang, J. J., Joh, J. W., Fuentebella, J., Patel, A., Nguyen, T., Seki, S., Hoyte, L., Reshamwala, N., Nguyen, C., Quiros, A., Bass, D., Sibley, E., Berquist, W., Cox, K., Kerner, J., Nadeau, K. C. 2010; 6 (1): 25-?

    Abstract

    Eosinophilic esophagitis (EoE) is characterized by the inflammation of the esophagus and the infiltration of eosinophils into the esophagus, leading to symptoms such as dysphagia and stricture formation. Systemic immune indicators like eotaxin and fibroblast growth factor were evaluated for possible synergistic pathological effects. Moreover, blood cells, local tissue, and plasma from EoE and control subjects were studied to determine if the localized disease was associated with a systemic effect that correlated with presence of EoE disease.Real-time polymerase chain reaction from peripheral blood mononuclear cells (PBMC), immunohistochemistry from local esophageal biopsies, fluid assays on plasma, and fluorescence-activated cell sorting on peripheral blood cells from subjects were used to study the systemic immune indicators in newly diagnosed EoE (n = 35), treated EoE (n = 9), Gastroesophageal reflux disease (GERD) (n = 8), ulcerative colitis (n = 5), Crohn's disease (n = 5), and healthy controls (n = 8).Of the transcripts tested for possible immune indicators, we found extracellular signal-regulated kinase (ERK), Bcl-2, bFGF (basic fibroblast growth factor), and eotaxin levels were highly upregulated in PBMC and associated with disease presence of EoE. Increased FGF detected by immunohistochemistry in esophageal tissues and in PBMC was correlated with low levels of pro-apoptotic factors (Fas, Caspase 8) in PBMC from EoE subjects. Plasma-derived bFGF was shown to be the most elevated and most specific in EoE subjects in comparison to healthy controls and disease control subjects.We describe for the first time a possible mechanism by which increased FGF is associated with inhibiting apoptosis in local esophageal tissues of EoE subjects as compared to controls. Eotaxin and FGF signaling pathways share activation through the ERK pathway; together, they could act to increase eosinophil activation and prolong the half-life of eosinophils in local tissues of the esophagus in EoE subjects.

    View details for DOI 10.1186/1710-1492-6-25

    View details for PubMedID 20815913

  • Viral infections: new and emerging CURRENT OPINION IN GASTROENTEROLOGY Khan, M. A., Bass, D. M. 2010; 26 (1): 26-30

    Abstract

    Viral gastrointestinal diseases are a leading cause of childhood death worldwide. Recognition of specific causes as they pertain to epidemiology, pathogenesis, treatment, and prevention is necessary for the clinician as scientific advances allow for greater understanding of the diseases. The present review summarizes these advances for commonly encountered causes of viral gastroenteritis.Implementation of rotavirus vaccine has decreased the burden of this disease in many communities, and advances in molecular testing of the virus increase the ability to test for the virus. The tools utilized to test for these viruses are quite sensitive however, and are limited to primarily research investigations. Associations between virus and other gastrointestinal diseases have been evaluated as well, as have the host factors contributing to susceptibility to these infections.Viral gastroenteritis is common, and specific viruses are difficult to identify. Testing of these viruses through PCR or electron microscopy as a research tool is important, as is recognition of host risk factors, epidemiologic issues, and development of prevention and treatment strategies by identifying virus transmission.

    View details for DOI 10.1097/MOG.0b013e328333d7af

    View details for Web of Science ID 000273306100005

    View details for PubMedID 19907323

  • Abdominal Pain, Gastrointestinal Bleeding, and Weight Loss in a 17-Year-Old Male DIGESTIVE DISEASES AND SCIENCES Fuentebella, J., Bass, D., Longacre, T., Ro, K. 2009; 54 (4): 722-724

    View details for DOI 10.1007/s10620-008-0644-9

    View details for Web of Science ID 000263832600004

    View details for PubMedID 19082713

  • Laboratory evaluation of inflammatory bowel disease CURRENT OPINION IN PEDIATRICS Wong, A., Bass, D. 2008; 20 (5): 566-570

    Abstract

    Recognizing inflammatory bowel disease (IBD) is straightforward when alarm symptoms are present, such as bloody diarrhea and weight loss. When the presentation is subtle or atypical, physicians must determine which patients warrant evaluation for IBD. Appropriate use of noninvasive tests can help identify which patients should undergo further investigation.Currently IBD serologies lack high enough sensitivity and specificity to make them useful as a screening test for distinguishing IBD from other disorders, but they may have a role in classifying subtypes of IBD. Fecal markers seem promising for helping to differentiate IBD from irritable bowl syndrome and for monitoring disease activity. Pharmacogenetically guided dosing is recommended for safe use of thiopurines but ongoing routine laboratory monitoring remains important. Thiopurine metabolite measurement can be useful but may not be needed in all cases.Primary care physicians should continue to rely on routine laboratory tests and clinical suspicion to decide which patients with abdominal pain to refer to a gastroenterologist. Serology panels are not useful for IBD screening as the results may lead to unnecessary procedures. Although fecal markers do show promise as a screening test for IBD, patient resistance to providing stool samples may limit its usefulness in disease monitoring. Thiopurine metabolite levels are best used in conjunction with clinical status and routine laboratory tests to monitor clinical response and adverse events.

    View details for DOI 10.1097/MOP.0b013e32830d3aaf

    View details for Web of Science ID 000259711200008

    View details for PubMedID 18781120

  • Recent advances and evidence gaps in persistent diarrhea JOURNAL OF PEDIATRIC GASTROENTEROLOGY AND NUTRITION Bhutta, Z. A., Nelson, E. A., Lee, W. S., Tarr, P. I., Zablah, R., Phua, K. B., Lindley, K., Bass, D., Phillips, A. 2008; 47 (2): 260-265

    View details for Web of Science ID 000258009700026

    View details for PubMedID 18664885

  • Use of serologic markers as a screening tool in inflammatory bowel disease compared with elevated erythrocyte sedimentation rate and anemia PEDIATRICS Sabery, N., Bass, D. 2007; 119 (1): E193-E199

    Abstract

    The purpose of this work was to evaluate the use of serologic testing as a screening test for inflammatory bowel disease compared with erythrocyte sedimentation rate and hemoglobin in a referred patient population with suspected inflammatory bowel disease.A retrospective study was performed, reviewing medical charts of patients who had inflammatory bowel disease serology performed at Prometheus Laboratories from September 2002 to September 2004. Patients were divided into 4 categories: ulcerative colitis, Crohn disease, indeterminate colitis, and noninflammatory bowel disease groups. Patients were categorized based on clinical evaluation by board-certified pediatric gastroenterologists.A total of 227 patients seen at the Lucile Packard Children's Hospital Gastroenterology Clinic had inflammatory bowel disease serology performed at or before the time of diagnosis. Seventeen charts were excluded secondary to inadequate information. Forty children were found to have inflammatory bowel disease, a prevalence of 19%. Overall, serologic testing for inflammatory bowel disease had 60% sensitivity and 92% specificity. A positive laboratory test for anemia or an elevated erythrocyte sedimentation rate had 83% sensitivity, whereas the combination of anemia and elevated erythrocyte sedimentation rate had 96% specificity. The positive predictive value of serologic testing was 60% compared with 79% in patients with anemia and elevated erythrocyte sedimentation rate. The positive predictive value of serologic testing in the subgroup of subjects without rectal bleeding (139 subjects) was only 35% compared with 60% using routine tests. Almost one third of all positive serologic tests were in patients with no demonstrable inflammatory bowel disease.As a pediatric inflammatory bowel disease screening strategy for the general pediatrician or gastroenterologist, the measurement of the combination of erythrocyte sedimentation rate and hemoglobin has a higher positive predictive value and is more sensitive, more specific, and less costly than commercial serologic testing.

    View details for DOI 10.1542/peds.2006-1361

    View details for Web of Science ID 000243191800028

    View details for PubMedID 17158948

  • Gastrointestinal bleeding CLINICAL PEDIATRICS Nguyen, P. C., Garcia-Careaga, M., Bass, D. 2005; 44 (7): 641-643

    View details for Web of Science ID 000231687200015

    View details for PubMedID 16151574

  • Maturation and trafficking markers on rotavirus-specific B cells during acute infection and convalescence in children JOURNAL OF VIROLOGY Jaimes, M. C., Rojas, O. L., Kunkel, E. J., Lazarus, N. H., Soler, D., BUTCHER, E. C., Bass, D., Angel, J., Franco, M. A., Greenberg, H. B. 2004; 78 (20): 10967-10976

    Abstract

    We have previously studied B cells, from people and mice, that express rotavirus-specific surface immunoglobulin (RV-sIg) by flow cytometry with recombinant virus-like particles that contain green fluorescent protein. In the present study we characterized circulating B cells with RV-sIg in children with acute and convalescent infection. During acute infection, circulating RV-sIgD(-) B cells are predominantly large, CD38(high), CD27(high), CD138(+/-), CCR6(-), alpha4beta7(+), CCR9(+), CCR10(+), cutaneous lymphocyte antigen-negative (CLA(-)), L-selectin(int/-), and sIgM(+), sIgG(-), sIgA(+/-) lymphocytes. This phenotype likely corresponds to gut-targeted plasma cells and plasmablasts. During convalescence the phenotype switches to small and large lymphocytes, CD38(int/-), CD27(int/-), CCR6(+), alpha4beta7(+/-), CCR9(+/-) and CCR10(-), most likely representing RV-specific memory B cells with both gut and systemic trafficking profiles. Of note, during acute RV infection both total and RV-specific murine IgM and IgA antibody-secreting cells migrate efficiently to CCL28 (the CCR10 ligand) and to a lesser extent to CCL25 (the CCR9 ligand). Our results show that CCR10 and CCR9 can be expressed on IgM as well as IgA antibody-secreting cells in response to acute intestinal infection, likely helping target these cells to the gut. However, these intestinal infection-induced plasmablasts lack the CLA homing receptor for skin, consistent with mechanisms of differential CCR10 participation in skin T versus intestinal plasma cell homing. Interestingly, RV memory cells generally lack CCR9 and CCR10 and instead express CCR6, which may enable recruitment to diverse epithelial sites of inflammation.

    View details for DOI 10.1028/JVI.78.20.10967-10976.2004

    View details for Web of Science ID 000224229000014

    View details for PubMedID 15452217

  • Intestinal Imaging of children with acute rotavirus gastroenteritis JOURNAL OF PEDIATRIC GASTROENTEROLOGY AND NUTRITION Bass, D., Cordoba, T., Dekker, T., Schuind, A., Cassady, J. 2004; 39 (3): 270-274

    Abstract

    To examine the morphology and motility of the distal small bowel of infants with rotavirus gastroenteritis using non-invasive/non-ionizing imaging technology.Prospective, non-randomized observational study of five infants with symptomatic rotavirus infection. Infants were imaged by real-time magnetic resonance imaging (MRI) and ultrasound within 5 days of onset of gastroenteritis symptoms. Imaging studies were repeated in the convalescent period 5 to 9 weeks later.Three of five infants had a significant increase in the ileal wall thickness visualized by ultrasound during acute rotavirus infection compared with convalescence. The number and size of mesenteric lymph nodes visualized by ultrasound appeared similar in the acute and convalescent phases, as did peristaltic activity assessed by MRI.Abdominal ultrasound can detect changes in ileal wall thickness in infants with rotavirus infection. These changes may reflect ileal inflammation elicited by viral infection. Such studies may prove useful in evaluating morphologic response to attenuated rotavirus vaccines.

    View details for Web of Science ID 000223570600009

    View details for PubMedID 15319628

  • Noncirrhotic portal hypertension in association with juvenile nephropathic cystinosis: Case presentation and review of the literature JOURNAL OF INHERITED METABOLIC DISEASE DiDomenico, P., Berry, G., Bass, D., Fridge, J., Sarwal, M. 2004; 27 (5): 693-699

    Abstract

    We report a case of portal hypertension and oesophageal varices arising in an 18-year-old female renal transplant recipient with juvenile nephropathic cystinosis diagnosed at 6 years of age. The patient had a history of poor compliance with her prescribed cysteamine therapy. Routine examination revealed normal liver function without hepatomegaly but asymptomatic splenomegaly. An abdominal ultrasound suggested mild oesophageal varices, confirmed later on endoscopy. A liver biopsy revealed an abundance of cystine crystals within the hepatic Kupffer cells, with preserved hepatic architecture. Although the pathophysiology of this rare complication is unclear, in the absence of other aetiologies the likely cause is the patient's poorly controlled cystinosis. As cystinotic patients live longer with improved renal transplant management and cysteamine therapy, it is of interest to characterize the long-term course of the illness after renal transplantation. An understanding of the pathophysiology of hepatic dysfunction will be required to manage this potential late complication of the disease.

    View details for Web of Science ID 000224100100019

    View details for PubMedID 15669688

  • Astrovirus, adenovirus, and rotavirus in hospitalized children: Prevalence and association with gastroenteritis JOURNAL OF PEDIATRIC GASTROENTEROLOGY AND NUTRITION Rodriguez-Baez, N., O'Brien, R., Qiu, S. Q., Bass, D. M. 2002; 35 (1): 64-68

    Abstract

    Agents of viral gastroenteritis such as astrovirus, rotavirus, and adenovirus are common pediatric pathogens accounting for many physician visits, hospital admissions, and nosocomial infections. Previous hospital-based prevalence studies have examined mainly symptomatic children.To evaluate the prevalence of astrovirus, rotavirus, and adenovirus infections among hospitalized children less than 6 years of age, regardless of symptoms, and determine association with gastroenteritis.From September 1998 to June 2000, stool specimens were collected twice weekly from children less than five years of age admitted to two wards in a tertiary-care children's hospital. A total of 480 samples were obtained from 309 hospitalizations. Stools were examined using antibody-based ELISA for astrovirus, rotavirus, and adenovirus. Clinical data was abstracted from patient records.Twenty one percent of the children had gastroenteritis symptoms at some point during their hospitalizations (43% were hospital acquired). Astrovirus was detected in 5.2% of all children compared to 6.8% with rotavirus and 0.8% with adenovirus serotypes 40 or 41. Nosocomial acquisition was common. Seventy five percent of astrovirus infections and 90% rotavirus infections were symptomatic. Astrovirus infections were significantly more likely to occur in younger infants and in children with compromised immunity. Rotavirus infections were significantly more likely to cause dehydration. In a three-year passive surveillance of gastroenteritis at the hospital, astrovirus and rotavirus infections peaked simultaneously in winter months.Rotavirus and astrovirus are common symptomatic infections on pediatric wards and contribute greatly to inpatient morbidity. Adenoviruses played a limited role in gastroenteritis in hospitalized children in this study.

    View details for DOI 10.1097/01.MPG.0000021335.28968.16

    View details for Web of Science ID 000177102600013

    View details for PubMedID 12142812

  • Gastrointestinal safety of an extended-release, nondeformable, oral dosage form (OROS (R))(1) - A retrospective study DRUG SAFETY Bass, D. M., Prevo, M., Waxman, D. S. 2002; 25 (14): 1021-1033

    Abstract

    The OROS osmotic (OSM) dosage form optimises extended-release oral administration by controlling the rate of drug release for a predetermined time, providing constant, patterned, or pulsed delivery profiles. OSM products include prescription medications for urology, CNS, and cardiovascular indications, as well as over-the-counter nasal/sinus congestion medications.This retrospective study examines US gastrointestinal (GI) safety data for the OROS dosage form following nearly two decades of use. Although GI injury and obstruction are known effects of oral medications, some reports have suggested that extended-release products pose a greater risk of GI injury and obstruction than other oral dosage forms. Products incorporating OROS technology are being prescribed to an expanding range of patients; a review of the GI safety data for this dosage form thus seemed timely and appropriate. US safety information was obtained from three sources: English language literature published from 1982 until June 1, 2000 from five major biomedical databases;postmarketing safety reports from January 1, 1983 until June 1, 2000 available through the Freedom of Information Act; andcommercial safety information obtained directly from ALZA Corporation's in-house safety database for those OSM products for which ALZA has reporting responsibility. US distribution data from IMS National Prescription Audit trade mark Plus data were used to estimate cumulative product distribution totals. These totals were combined with numbers of unique GI events to determine the estimated frequency of events.Nearly 13 billion OSM tablets are estimated to have been distributed in the US. The incidence of all clinically significant GI adverse events for OSM products (including intestinal, gastric, and oesophageal irritation, injury, and obstruction) reported in the US was approximately one case in >76 million tablets distributed. The majority (78%; estimated incidence: one case in 29 million tablets) of cases were reported in patients taking Procardia XL (nifedipine). Oesophageal and lower GI obstruction were reported primarily in patients with pre-existing abnormalities or disease of the GI tract. Among paediatric patients, one obstruction was reported in an estimated 37.7 million tablets distributed. Reports of GI irritation associated with OSM products were consistent with known effects of the same drug substances in other dosage forms.A review of long-term safety experience with products using OSM controlled-release technology yields a low incidence of clinically significant GI events. Properly prescribed, extended-release products provide substantial therapeutic and convenience benefits without additional risk.

    View details for Web of Science ID 000179420000004

    View details for PubMedID 12408733

  • Proteolytic processing of the astrovirus capsid JOURNAL OF VIROLOGY Bass, D. M., Qiu, S. Q. 2000; 74 (4): 1810-1814

    Abstract

    To further characterize the nature of proteolytic processing of the astrovirus capsid, we infected Caco-2 cells with a high multiplicity of astrovirus without trypsin in the presence of 5 to 10% fetal calf serum. These infections were characterized by pulse-chase labeling with [35S]Smethionine, electron microscopy, gel electrophoresis of purified viral particles, and analysis of infectivity of such particles with and without added trypsin. Pulse-chase experiments showed that the astrovirus capsid protein was initially translated as an approximately 87-kDa protein. The 87-kDa capsid protein was rapidly converted intracellularly to a 79-kDa form which was found in smaller amounts in the cell supernatant. Purification by differential centrifugation yielded particles that appeared quite similar to trypsin-grown astrovirus particles by negatively stained electron microscopy. These particles were antigenically distinct from trypsin-treated virions as demonstrated by their various reactions with monoclonal antibodies in a solid-phase immunoassay. The purified trypsin-free particles were mainly composed of the 79-kDa capsid protein which was found to have an amino terminus at residue 71 of the entire open reading frame 2 (ORF2) product. The cleavage site was identified in a highly conserved region of the astrovirus ORF2 product. These trypsin-free particles were minimally infectious in cultured Caco-2 cells but became highly infectious (10(5)-fold increase) after trypsin but not chymotrypsin treatment. This trypsin-enhanced infectivity correlated with conversion of the 79-kDa capsid protein to three smaller peptides of approximately 34, 29, and 26 kDa.

    View details for Web of Science ID 000084958000027

    View details for PubMedID 10644354

  • Lack of a role for type I and type II interferons in the resolution of rotavirus-induced diarrhea and infection in mice JOURNAL OF INTERFERON AND CYTOKINE RESEARCH Angel, J., Franco, M. A., Greenberg, H. B., Bass, D. 1999; 19 (6): 655-659

    Abstract

    Rotavirus infects the intestinal epithelium of most mammalian species and causes diarrhea in infants. Previously, we have shown that both type I and II human interferons (IFNs) have potent and mechanistically discreet antiviral effects in vitro against rotavirus. We have also shown that adult IFN-gamma knockout (-/-) mice have no alteration in clearance of primary rotavirus infection. In the present studies, we wished to determine the importance of both IFN types in modulation of degree and duration of disease and infection in mice. Immunocompetent suckling mice were treated orally (5,000 IU) or parenterally (500 IU) with type I and II murine IFNs before and after challenge with virulent murine rotavirus. Treated animals developed diarrhea indistinguishable from that observed in untreated control mice. In other experiments, type I IFN receptor -/- suckling mice and IFN-gamma-/- suckling mice developed diarrhea of similar characteristics and duration and had comparable quantities of viral antigen in their intestines as did immunocompetent mice. Furthermore, type I IFN receptor -/- adult mice infected with rotavirus shed equivalent quantities of viral antigen and with similar kinetics as the control mice. Thus, IFNs do not seem to be major inhibitors of rotavirus diarrhea or replication in mice.

    View details for Web of Science ID 000081510000014

    View details for PubMedID 10433367

  • Travel vaccines INFECTIOUS DISEASE CLINICS OF NORTH AMERICA Thompson, R. F., Bass, D. M., HOFFMAN, S. L. 1999; 13 (1): 149-?

    Abstract

    Travel-related infectious diseases are exceedingly common, difficult to diagnose, and sometimes preventable. Vaccination is one tool for reducing the risk of infectious disease for some travelers. Both healthcare providers and travelers need to be aware of the new travel vaccines, and new formulations of older vaccines that now are available. This article presents an update on vaccines for cholera, Japanese encephalitis, rabies, rotavirus, typhoid, and malaria.

    View details for Web of Science ID 000079651800012

    View details for PubMedID 10198797

  • Prevalence of astroviruses in a children's hospital JOURNAL OF CLINICAL MICROBIOLOGY Shastri, S., Doane, A. M., Gonzales, J., Upadhyayula, U., Bass, D. M. 1998; 36 (9): 2571-2574

    Abstract

    An enzyme immunoassay for astrovirus was used to screen 357 stool samples from 267 symptomatic inpatients at a tertiary-care children's hospital. Thirty stool samples from 26 patients contained astrovirus antigen, while rotavirus was found in 34 samples and Clostridium difficile toxin was found in 40. Half of the astrovirus infections were nosocomial. Additional pathogens were identified in six of the astrovirus antigen-positive stool samples. Most (80%) of the astroviruses recovered were of serotype 1. Astrovirus infections were significantly more common than rotavirus or C. difficile infections in very young infants and in those with surgical short-bowel syndrome.

    View details for Web of Science ID 000075420800033

    View details for PubMedID 9705394

  • Celiac disease presenting as gait disturbance and ataxia in infancy JOURNAL OF CHILD NEUROLOGY Hahn, J. S., Sum, J. M., Bass, D., Crowley, R. S., Horoupian, D. S. 1998; 13 (7): 351-353

    View details for Web of Science ID 000075150900010

    View details for PubMedID 9701487

  • Studies of the role for NSP4 in the pathogenesis of homologous murine rotavirus diarrhea JOURNAL OF INFECTIOUS DISEASES Angel, J., Tang, B. Z., Feng, N. G., Greenberg, H. B., Bass, D. 1998; 177 (2): 455-458

    Abstract

    A rotavirus (RV) nonstructural protein, NSP4, has recently been proposed to function as an enterotoxin in the pathogenesis of RV diarrhea. The role of NSP4 in the pathogenesis of RV diarrhea was examined by infecting cystic fibrosis transmembrane conductance regulator (CFTR) knockout mice with virulent murine RV and by comparing deduced amino acid sequences of RV gene 10 encoding NSP4 from three distinct sets of virulent and tissue culture-adapted avirulent variant RVs. Homozygous CFTR (CFTR-/-) mice, which do not respond to any known intestinal secretagogues, experienced diarrhea comparable to that in normal CFTR+/+ littermates after RV challenge. Comparison of amino acid sequences of NSP4 from virulent and attenuated pairs of RVs failed to show consistent or significant changes. Together, these data suggest that enterotoxigenic properties of RV NSP4 are not critical in the pathogenesis of murine RV diarrhea and that attenuation of murine RVs is not usually mediated by mutations in the gene encoding NSP4.

    View details for Web of Science ID 000071801500026

    View details for PubMedID 9466536

  • Wernicke encephalopathy and Beriberi during total parenteral nutrition attributable to multivitamin infusion shortage PEDIATRICS Hahn, J. S., Berquist, W., Alcorn, D. M., Chamberlain, L., Bass, D. 1998; 101 (1)

    Abstract

    Wernicke encephalopathy (WE) is an acute neurologic disorder characterized by a triad of ophthalmoplegia, ataxia, and mental confusion. WE is attributable to thiamine (vitamin B1) deficiency. Beriberi is the systemic counterpart of thiamine deficiency and often manifests in cardiovascular collapse. WE is usually associated with alcoholism and malnutrition. It has also been seen in people with gastrointestinal diseases with malabsorption. Patients who have received total parenteral nutrition (TPN) without proper replacement of thiamine have also developed WE. Since November 1996, there has been a shortage of multivitamin infusion (MVI). Many patients who were on chronic TPN with MVI ceased to receive the MVI and were converted to an oral form of the multivitamin. As a result, there have been several reports of children and adults on TPN who have developed WE as a result of thiamine deficiency. With this case report, we bring to attention the association of the MVI shortage and WE. Early diagnosis of WE is important, because if it is treated with thiamine in the acute stages, the neurologic and cardiovascular abnormalities can be reversed.We report a 20-year-old female patient with Crohn's disease who developed WE as a result of thiamine deficiency. She had Crohn's disease since age 9 years and was on chronic TPN. Two months before admission, MVI was discontinued in the TPN because of the shortage of its supply. An oral multivitamin tablet was substituted instead. She was admitted to the hospital for persistent vomiting. In the hospital, she continued to receive TPN without MVI, but continued taking an oral multivitamin preparation. Two weeks after admission, she developed signs of WE including diplopia, ophthalmoplegia, nystagmus, and memory disturbance. She also developed hypotension that was thought to be caused by beriberi. She was treated with 50 mg of intravenous thiamine. Within hours of the intravenous thiamine, her hypotension resolved. The day after the infusion, she no longer complained of diplopia, and her ophthalmoplegia had improved dramatically. Magnetic resonance imaging showed several areas of abnormally high signal on T2-weighted images in the brainstem, thalamus, and mamillary bodies. The topographic distribution of these changes was typical of WE. After 2 months, her mental status and neurologic status had recovered completely.WE and thiamine deficiency should be considered in all patients with malabsorption, malnutrition, and malignancies. WE from thiamine deficiency can occur as a result of cessation of MVI in the TPN infusion. Even if an oral multivitamin preparation is given instead of MVI, patients with malabsorption may not absorb thiamine adequately. Prompt diagnosis of WE is important because it is potentially fatal and readily treatable with thiamine supplementation. Early recognition of WE may be more difficult in children, because the classic triad of symptoms may not develop fully. Magnetic resonance imaging may be useful in these cases to confirm the diagnosis of WE. Because the shortage of MVI is expected to be a long-term, there are likely to be more cases of WE in the pediatric population of TPN-dependent children. Because there is no shortage of intravenous thiamine, it should be administered with TPN even if MVI is not available.

    View details for Web of Science ID 000071331400026

    View details for PubMedID 9417174

  • Characterization of human serotype 1 astrovirus-neutralizing epitopes JOURNAL OF VIROLOGY Bass, D. M., Upadhyayula, U. 1997; 71 (11): 8666-8671

    Abstract

    Astroviruses are important agents of pediatric gastroenteritis. To better understand astrovirus antigenic structure and the basis of protective immunity, monoclonal antibodies (MAbs) were produced against serotype 1 human astrovirus. Four MAbs were generated. One MAb (8G4) was nonneutralizing but reacted to all seven serotypes of astrovirus by enzyme-linked immunosorbentassay (ELISA) and immunoperoxidase staining of infected cells. Three MAbs were found to have potent neutralizing activity against astrovirus. The first (5B7) was serotype 1 specific, another (7C2) neutralized all seven human astrovirus serotypes, while the third (3B2) neutralized serotypes 1 and 7. Immunoprecipitation of radiolabeled astrovirus proteins from supernatants of astrovirus-infected cells showed that all three neutralizing antibodies reacted with VP29. MAb 5B7 also reacted strongly with VP26. A competition ELISA showed that all three neutralizing antibodies competed with each other for binding to purified astrovirus virions, suggesting that their epitopes were topographically in close proximity. None of the neutralizing MAbs competed with nonneutralizing MAb 8G4. The neutralizing MAbs were used to select antigenic variant astroviruses, which were then studied in neutralization assays. These assays also suggested a close relationship between the respective epitopes. All three neutralizing MAbs were able to prevent attachment of radiolabeled astrovirus particles to human Caco 2 intestinal cell monolayers. Taken together, these data suggest that the astrovirus capsid protein VP29 may be important in viral neutralization, heterotypic immunity, and virus attachment to target cells.

    View details for Web of Science ID A1997YB14300068

    View details for PubMedID 9343224

  • Expression of mucosal homing receptor alpha 4 beta 7 by circulating CD4(+) cells with memory for intestinal rotavirus JOURNAL OF CLINICAL INVESTIGATION Rott, L. S., Rose, J. R., Bass, D., Williams, M. B., Greenberg, H. B., BUTCHER, E. C. 1997; 100 (5): 1204-1208

    Abstract

    The integrin alpha4beta7 mediates lymphocyte binding to mucosal addressin cell adhesion molecule-1, and its expression defines lymphocytes capable of trafficking through the intestines and the intestinal lymphoid tissues. We examined the ability of discrete alpha4beta7(hi) and alpha4beta7- subsets of circulating memory phenotype (CD45RA-) CD4+ T cells to proliferate in response to rotavirus, a ubiquitous intestinal pathogen. alpha4beta7(hi) memory (CD45RA-) CD4+ T cells displayed much greater reactivity to rotavirus than alpha4beta7- memory or naive (CD45RA+) CD4+ T cells. In contrast, alpha4beta7- memory cells were the predominant population responsive to mumps antigen after intramuscular vaccination. Our results are consistent with the conclusion that natural rotavirus infection, an enteric pathogen, results in a specific circulating memory CD4+ response that is largely limited to the gut-homing alpha4beta7+ subpopulation. This phenotype is not shared with memory cells elicited by intramuscular immunization (shown here) or by skin contact allergens. The results support the hypothesis that gut trafficking memory CD4+ T cells comprise cellular memory for intestinal antigens and suggest that regulated expression of alpha4beta7 helps target and segregate intestinal versus systemic immune response.

    View details for Web of Science ID A1997XV75300030

    View details for PubMedID 9276738

  • Interferon gamma and interleukin 1, but not interferon alfa, inhibit rotavirus entry into human intestinal cell lines GASTROENTEROLOGY Bass, D. M. 1997; 113 (1): 81-89

    Abstract

    Rotavirus, an important agent of gastroenteritis in children, causes diarrhea by infecting differentiated villus enterocytes in the small intestine. The aim of this study was to determine whether cytokines that can be expressed by mucosal cells have an effect on the rotavirus susceptibility of cultured human enterocytes.Caco-2 and HT-29 cells were pretreated with various cytokines before challenge with rotavirus.Interleukin (IL)-1, interferon (IFN)-alpha, and IFN-gamma pretreatment led to a dose-dependent resistance to rotavirus infection. Maximum effects occurred after 72 hours of pretreatment, whereas no detectable inhibition occurred with <12 hours of pretreatment. Liposomal transfection of single-shelled and double-shelled rotavirus particles bypassed the block to rotavirus replication in IFN-gamma- and IL-1-treated but not IFN-alpha-treated cells. Binding studies with purified, metabolically labeled rotavirus showed no significant difference among IFN-gamma- and IFN-alpha-treated and control Caco-2 cells. Viral entry into Caco-2 cells was significantly inhibited by IFN-gamma and IL-1 but not IFN-alpha.IFN-alpha and IFN-gamma induce rotavirus resistance by different mechanisms, suggesting that cytokines play a role in host defense against viral agents by changing the phenotype of intestinal epithelial cells.

    View details for Web of Science ID A1997XJ38300015

    View details for PubMedID 9207265

  • Viral infections of the gastrointestinal tract CURRENT OPINION IN GASTROENTEROLOGY Bass, D. 1996; 12 (1): 76-81
  • DANSYLCADAVERINE AND CYTOCHALASIN-D ENHANCE ROTAVIRUS INFECTION OF MURINE L-CELLS VIROLOGY Bass, D. M., Baylor, M., Chen, C., Upadhyayula, U. 1995; 212 (2): 429-437

    Abstract

    Although murine L cells bind and internalize rotavirus as well as permissive cell lines, L cells are essentially nonpermissive for rotaviruses. In nonpermissive cell lines such as L cells, internalized rotavirus fails to uncoat and remains as infectious, double-shelled particles. This block in the infectious cycle can be overcome by direct lipofection of viral particles into the L cell cytoplasm. We hypothesized that the internalized rotavirus particles within L cells are sequestered in the endocytic pathway and are unable to initiate infection. L cells were pretreated with a variety of inhibitors of endocytosis prior to infection with rhesus rotavirus. While agents which inhibit acidification of endosomes had no effect on rotavirus infection, two potential direct inhibitors of vesicular transport, dansylcadaverine and cytochalasin D, enhanced rotavirus infection of L cells 5- to 10-fold. All of the drugs, including both inhibitors of endocytosis and lysosomotrophic agents, significantly reduced infection of L cells by serotype 1 reovirus which is known to infect L cells by the endocytic pathway. Time course studies demonstrated that the drugs were effective in promoting rotavirus infection of L cells in only the early phases of infection. Pretreatment of L cells with dansylcadaverine significantly decreased the number of intact, double-shelled rotavirus particles sequestered within the cells. Inhibition of endocytosis may increase the efficiency of infection of L cells by rotavirus by allowing an increased proportion of attached rotavirus virions to enter cells by a productive route which is probably direct membrane penetration.

    View details for Web of Science ID A1995RY72500015

    View details for PubMedID 7571412

  • Effects of cytokines on rotavirus infection of human CaCo 2 intestinal cells CYTOKINES, CHOLERA, AND THE GUT Bass, D. M. 1995: 99-103
  • VIRAL-INFECTIONS OF THE GASTROINTESTINAL-TRACT CURRENT OPINION IN GASTROENTEROLOGY Bass, D. 1995; 11 (1): 58-62
  • Can we actively treat rotavirus gastroenteritis? Journal of pediatric gastroenterology and nutrition Bass, D. 1994; 19 (4): 473-474

    View details for PubMedID 7877007

  • MURINE INTESTINAL MUCINS INHIBIT ROTAVIRUS INFECTION GASTROENTEROLOGY Chen, C. C., Baylor, M., Bass, D. M. 1993; 105 (1): 84-92

    Abstract

    Mucin, a population of polymeric glycoproteins, constitutes the primary component of the mucus layer that overlies the gastrointestinal tract. These studies aimed to determine whether murine intestinal mucins inhibit rotavirus infection.Murine intestinal mucins were obtained by scraping segments of mouse intestine and purification via CsCl gradient centrifugation and sepharose 4B chromatography. Inhibition of infection was determined by quantitation of immunoperoxidase-stained cells after infection with mucin-rotavirus mixtures.Crude and purified intestinal mucins from suckling and adult mice are potent inhibitors of replication of a simian rotavirus, rhesus rotavirus (RRV), but weak inhibitors of other rotaviruses. In all preparations, colonic mucins were more potent inhibitors of RRV than small intestinal mucins. Suckling mucins neutralized RRV more effectively than adult mucins. In a panel of rotavirus reassortants, susceptibility to mucin inhibition correlated with the ability to hemagglutinate human type O erythrocytes and with RRV gene 4. Murine intestinal mucin inhibited RRV binding to MA104 cells, suggesting inhibition of virus-cell attachment to be the mechanism for neutralization. Mercaptoethanol or neuraminidase inhibited mucins' anti-RRV activities, implying the functional importance of mucins' polymeric structure and sialic acid content.These findings suggest that intestinal mucins represent a barrier to certain rotavirus infections.

    View details for Web of Science ID A1993LJ98400011

    View details for PubMedID 8390382

  • CHILDHOOD AND VIRAL-INFECTIONS CURRENT OPINION IN INFECTIOUS DISEASES Bass, D. 1993; 6 (1): 83-87
  • LIPOSOME-MEDIATED TRANSFECTION OF INTACT VIRAL PARTICLES REVEALS THAT PLASMA-MEMBRANE PENETRATION DETERMINES PERMISSIVITY OF TISSUE-CULTURE CELLS TO ROTAVIRUS JOURNAL OF CLINICAL INVESTIGATION Bass, D. M., Baylor, M. R., Chen, C., Mackow, E. M., Bremont, M., Greenberg, H. B. 1992; 90 (6): 2313-2320

    Abstract

    Rotaviruses are an important cause of gastroenteritis in human infants. In vivo, rotavirus displays striking cell tropism with viral replication generally restricted to the villus tip enterocytes of the small intestine. We studied a panel of cell lines that vary significantly in their permissivity to rotavirus infection. L cells and HEp2 cells were relatively resistant to rotavirus infection compared with permissive Ma104 cells and HT29 cells. RNA transcription among the cell lines was proportional to antigen synthesis making a translational or posttranslational block an unlikely source of observed differences in susceptibility. All of the cell lines bound and internalized radiolabeled virus equally well, as measured by escape from surface protease treatment. Analysis of the escape of cell bound virus from neutralizing monoclonal antibody revealed that rotavirus did not immediately enter an eclipse phase in nonpermissive cells, but was internalized in an infectious form for several hours, possibly sequestered within endocytic vacuoles. L cells and HEp2 cells were as permissive as Ma104 and HT29 cells when rotavirus infection was mediated by transfection of single- or double-shelled rotavirus particles with cationic liposomes (Lipofectin). Rotavirus cell tropism in tissue culture cells is determined by the ability of infecting virions to traverse the plasma membrane of the cells into the cytoplasmic compartment.

    View details for Web of Science ID A1992KE76300020

    View details for PubMedID 1334974

  • MOLECULAR-BASIS OF AGE-DEPENDENT GASTRIC INACTIVATION OF RHESUS ROTAVIRUS IN THE MOUSE JOURNAL OF CLINICAL INVESTIGATION Bass, D. M., Baylor, M., Broome, R., Greenberg, H. B. 1992; 89 (6): 1741-1745

    Abstract

    Rotavirus requires specific proteolytic activation by trypsin for efficient replication in tissue culture. To observe the nature of intestinal proteolytic activation of rotavirus in vivo, metabolically labeled rhesus rotavirus (RRV) grown in the presence of trypsin inhibitors was administered to adult and 10-d-old suckling mice by gavage. In the adult stomach, vp4 was cleaved in a manner distinct from in vitro trypsin cleavage. In the suckling stomach, RRV vp4 remains largely uncleaved. The alternative cleavage in the adult stomach was associated with a profound decrease in viral infectivity. vp4 from RRV recovered from the suckling small intestinal lumen was cleaved in a pattern similar or identical to in vitro trypsin-activated virus with bands comigrating with vp5* and vp8*. In contrast, vp4 was not observed in any recognizable form in RRV recovered from adult intestines. Comparison of infectivity of virus recovered from suckling and adult intestines revealed a 10,000-fold decrease in titer in the virus recovered from the adult intestine. In vitro digestions of RRV revealed that pepsin digestion can cleave RRV vp4 and markedly enhance acid-induced loss of rotavirus infectivity. Subsequent digestion with chymotrypsin removes most of the pepsin cleavage products of vp4. Virus injected directly into jejunal loops of adult mice and virus administered orally to adult mice pretreated with antiacid drugs retained infectivity. These studies indicate the development of gastric acid and pepsin secretion may be an important host defense factor in rotavirus gastroenteritis.

    View details for Web of Science ID A1992HX97400007

    View details for PubMedID 1318323

  • STRATEGIES FOR THE IDENTIFICATION OF ICOSAHEDRAL VIRUS RECEPTORS JOURNAL OF CLINICAL INVESTIGATION Bass, D. M., Greenberg, H. B. 1992; 89 (1): 3-9

    View details for Web of Science ID A1992GY56100001

    View details for PubMedID 1309536

  • IDENTIFICATION AND PARTIAL CHARACTERIZATION OF A RHESUS ROTAVIRUS BINDING GLYCOPROTEIN ON MURINE ENTEROCYTES VIROLOGY Bass, D. M., MACKOW, E. R., Greenberg, H. B. 1991; 183 (2): 602-610

    Abstract

    In order to assess the possibility that rotavirus binds to a specific cellular receptor on enterocytes, we have used a viral overlay protein blot assay to study viral binding to murine intestinal brush border membranes (BBM). Infectious double-shelled particles of rhesus rotavirus bound specifically to two approximately 300- and 330-kDa glycoproteins from BBM prepared from suckling mice. Significantly less rotavirus binding was observed when adult BBM were examined. Rats have never been shown to harbor natural group A rotavirus infection and correspondingly, rat BBM showed no rotavirus binding activity. In suckling mice, rotavirus was found to bind to villus tip membranes to a much greater extent than to crypt preparations. Rotavirus binding activity was abolished by treatment of membrane preparations with protease. Analysis by glycolytic digestion of BBM with N- and O-glyconases revealed evidence for both N- and O-linked glycosylation of the rotavirus binding protein. Also neuraminidase digestion showed that O-linked sialic acid residues were required for virus binding. Monoclonal antibodies which immunoprecipitate the 300-kDa viral binding glycoprotein react with the apical surface of suckling but not adult enterocytes by Western blot. Baculovirus-expressed vp4, the rotavirus outer capsid spike protein, bound to the 300- and 330-kDa proteins and competed with rotavirus particles for binding sites. The ability of rotavirus to bind via vp4 to large BBM glycoproteins correlates with in vivo rotavirus cell tropism and host range restriction. Specific host cell receptor expression may be important in rotavirus pathogenesis.

    View details for Web of Science ID A1991FW36100016

    View details for PubMedID 1649504

  • SYMMETRICAL INFECTION OF ROTAVIRUS ON POLARIZED HUMAN INTESTINAL EPITHELIAL (CACO-2) CELLS JOURNAL OF VIROLOGY Svensson, L., Finlay, B. B., Bass, D., VONBONSDORFF, C. H., Greenberg, H. B. 1991; 65 (8): 4190-4197

    Abstract

    When rotavirus infects the mature villus tip cells of the small intestine, it encounters a highly polarized epithelium. In order to understand this virus-cell interaction more completely, we utilized a cell culture-adapted rhesus rotavirus (RRV) to infect human intestinal (Caco-2) and Madin-Darby canine kidney (MDCK-1) polarized epithelial cells grown on a permeable support. Filter-grown Caco-2 cells and MDCK-1 cells, producing a transepithelial resistance of 300 to 500 and greater than 1,000 omega . cm2, respectively, were infected from either the apical or basolateral domain with RRV or Semliki Forest virus. Whereas Semliki Forest virus infection only occurred when input virions had access to the basolateral domain of MDCK-1 or Caco-2 cells, RRV infected MDCK-1 and Caco-2 monolayers in a symmetric manner. The effect of rotavirus infection on monolayer permeability was analyzed by measuring the transepithelial electrical resistance. Rotavirus infection on filter-grown Caco-2 cells caused a transmembrane leak at 18 h postinfection, before the development of the cytopathic effect (CPE) and extensive virus release. Electrical resistance was completely abolished between 24 and 36 h postinfection. Although no CPE could be detected on RRV-infected MDCK cells, the infection caused a transmembrane leak that totally abolished the electrical resistance at 18 to 24 h postinfection. Cell viability and the CPE analysis together with immunohistochemistry and immunofluorescence data indicated that the abolishment of resistance across the monolayer was due not to an effect on the plasma membrane of the cells but to an effect on the paracellular pathway limited by tight junctions. Attachment and penetration of rotavirus onto Caco-2 cells caused no measurable transmembrane leak during the first hour of infection.

    View details for Web of Science ID A1991FY29700028

    View details for PubMedID 1649325

  • IMMUNIZATION WITH BACULOVIRUS-EXPRESSED VP4 PROTEIN PASSIVELY PROTECTS AGAINST SIMIAN AND MURINE ROTAVIRUS CHALLENGE JOURNAL OF VIROLOGY MACKOW, E. R., Vo, P. T., Broome, R., Bass, D., Greenberg, H. B. 1990; 64 (4): 1698-1703

    Abstract

    A baculovirus-expressed VP4 protein derived from the simian rhesus rotavirus (RRV) was used to parenterally immunize murine dams. VP4-immunized dams developed high levels of neutralizing antibodies against RRV and low levels of cross-reactive neutralizing antibodies against human strains Wa, ST3, and S2 and animal strains SA-11, NCDV, and Eb. Newborn mice suckled on VP4-immunized dams were protected against a virulent challenge dose of the simian strain RRV and against murine rotavirus Eb. The cross-reactive nature of the serum-neutralizing response generated by VP4 immunization and the protective efficacy of the immunization suggest that recombinant-expressed VP4 proteins should be considered as viable vaccine candidates.

    View details for Web of Science ID A1990CT84500034

    View details for PubMedID 2157052

  • NS35 AND NOT VP7 IS THE SOLUBLE ROTAVIRUS PROTEIN WHICH BINDS TO TARGET-CELLS JOURNAL OF VIROLOGY Bass, D. M., MACKOW, E. R., Greenberg, H. B. 1990; 64 (1): 322-330

    Abstract

    Recent studies using radiolabeled rotavirus lysates have demonstrated a 35-kilodalton viral protein that binds specifically to the surface of MA104 cells (N. Fukuhara, O. Yoshie, S. Kitakoa, and T. Konno, J. Virol. 62:2209-2218, 1988; M. Sabara, J. Gilchrist, G.R. Hudson, and L.A. Babiuk, J. Virol. 53:58-66, 1985). The binding protein was identified as vp7, an outer capsid glycoprotein and the product of rotavirus gene 9. These studies concluded that vp7 mediated viral attachment to MA104 cells and that the binding of a soluble viral protein to a cell monolayer mirrored the attachment of infectious rotavirus to permissive tissue culture cells. In the process of determining which viral protein adheres to the in vivo target cell in rotavirus infection, the mammalian enterocyte, we found that a similar 35-kilodalton rhesus rotavirus (RRV) protein bound to both MA104 cells and murine enterocytes. However, further analysis of this protein by immunoprecipitation, inhibition of glycosylation, and partial proteolysis showed that it was not the RRV gene 9 product, vp7, but the gene 8 product, NS35. Similar results were obtained by using porcine rotavirus (OSU) and bovine rotavirus (NCDV) strains. Binding studies using the in vitro-expressed products of RRV genes 8 and 9 confirmed these results. Since double-shelled virions inhibited the binding of NS35 to cells, we looked for the presence of this protein in preparations of purified virus. Examination of density gradient-purified virus preparations revealed biochemical and immunological evidence that NS35 copurifies in small amounts with double-shelled virions. Thus, these studies clearly demonstrated that when rotavirus proteins are prepared in a soluble form from infected cells, NS35, and not vp7, binds to the surfaces of MA104 cells and murine enterocytes. The observations do not confirm previous experimental results which supported the hypothesis that vp7 was the viral attachment protein. They are consistent with but do not prove the hypothesis that NS35 functions as the rotavirus attachment protein.

    View details for Web of Science ID A1990CE14700036

    View details for PubMedID 2152820

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