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Published on: April 29, 2020
Dose-Response of a Norovirus GII.2 Controlled Human Challenge Model Inoculum
Nadine Rouphael1, Allison Beck1, Amy E Kirby2
1Hope Clinic of the Emory Vaccine Center, Division of Infectious Diseases, Department of Medicine, School of Medicine, Emory University, Atlanta, Georgia, USA.
Background:
Genogroup II noroviruses are the most common cause of acute infectious gastroenteritis. We evaluated the use of a new GII.2 inoculum in a human challenge.
Methods:
Forty-four healthy adults (36 secretor-positive and 8 secretor-negative for histo-blood group antigens) were challenged with ascending doses of a new safety-tested Snow Mountain virus (SMV) GII.2 norovirus inoculum (1.2 × 104 to 1.2 × 107 genome equivalent copies [GEC]; n = 38) or placebo (n = 6). Illness was defined as diarrhea and/or vomiting postchallenge in subjects with evidence of infection (defined as GII.2 norovirus RNA detection in stool and/or anti-SMV immunoglobulin G [IgG] seroconversion).
Results:
The highest dose was associated with SMV infection in 90%, and illness in 70% of subjects with 10 of 12 secretor-positive (83%) and 4 of 8 secretor-negative (50%) becoming ill. There was no association between prechallenge anti-SMV serum IgG concentration, carbohydrate-binding blockade antibody, or salivary immunoglobulin A and infection. The median infectious dose (ID50) was 5.1 × 105 GEC.
Conclusions:
High rates of infection and illness were observed in both secretor-positive and secretor-negative subjects in this challenge study. However, a high dose will be required to achieve the target of 75% illness to make this an efficient model for evaluating potential norovirus vaccines and therapeutics.
Clinical Trials Registration:
NCT02473224.
