Infection and Illness in Human Subjects Challenged with Two Snow Mountain Virus (SMV) Inocula Open Access

Qu, Hongyan (Fall 2022)

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Snow Mountain Virus is the prototype strain of genogroup II and genotype 2 NoV. Since the 1970s, a number of NoV (including SMV) human challenge studies have been performed, mainly in the United States, to study NoV immune response, pathogenesis, and vaccine efficacy.



The aim of this study is to evaluate infection and illness in subjects challenged with two different SMV inocula and identify factors associated with viral shedding and clinical symptoms.



We analyzed data sets from two SMV human challenge studies previously conducted in 2000-2002 and 2015-2018, respectively. Clinical and laboratory data were analyzed for infection and illness rates, severity scores of acute gastroenteritis in subjects with clinical symptoms, viral shedding, and serum IgG/IgA conversion. Logistic regression analysis was used to examine what factors were associated with post-challenge infection and illness.



The two clinical datasets had a total of 49 subjects. 15 subjects were orally challenged with a first generation SMV inoculum 1 between 2000-2002, and 34 subjects were orally challenged with a second generation SMV inoculum 2 between 2015-2018. There were no statistically significant differences in overall infection and illness rates between subjects challenged with inoculum 1 and inoculum 2. However, individuals challenged with inoculum 1 experienced more severe clinical symptoms of acute gastroenteritis, demonstrating significantly higher severity scores (6.00 vs. 2.94, P=0.003) compared with those challenged with inoculum 2. We also observed that pre-challenge serum blockade antibody titers 50% (BT50) were associated with protection from SMV infection (P=0.046) but not with illness (P=0.146) after controlling for covariates. In addition, the data showed that subjects infected with inoculum 2 tended to have longer viral shedding compared with those infected with inoculum 1.



Understanding the difference between the two SMV inocula is critical for NoV vaccine evaluation because illness and viral shedding are two important outcomes.

Table of Contents

Distribution Agreement, Approval Sheet, Abstract cover Sheet, Abstract, Thesis Cover Page, Acknowledgements, Table of Contents, Chapter I: Introduction and Literature review 1. Introduction, 2. Epidemiology of NoV Infection 3. Clinical systems of NoV Infection. 4. NoV Human Challenge Study 5. NoV Laboratory Diagnosis. 6. NoV Vaccine Development, Chapter II: Manuscript, 1. Abstract 2. Introduction, 3. Material and methods. 4. Definition of SMV Infection. 5. Measurement of serum antibodies 6. Statistical analysis. 7. Results 8. Discussion 9. Tables. 10. References. Chapter III: Conclusions/Limitations/Public Health Significances 1. Conclusions 2. Limitations 3. Public Health Significance

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