MATERIALS AND METHODS
SMV human challenge study 1 [11]: 15 healthy human subjects were challenged with one dose of SMV inoculum, ranging from 31.7 to 3.17 × 105 genome copies quantitated by RT-qPCR [13]. Subjects remained in the hospital clinical research unit for five days after challenge. Stool, serum, vomitus, saliva samples and clinical information were collected daily. Subjects were also followed up on days 7, 15, 30, and 45 post-challenge for stool and serum sample collection [11].
SMV human challenge study 2 [9]: The study consisted of four sequential cohorts and a placebo group. In cohorts 1 through 3 (all subjects were secretor positive), individuals per cohort were challenged with 1.2 x 104 genome equivalent copies (GEC) (cohort 1), 1.2 x 106 GEC (cohort 2) and 1.2 x 107 GEC (cohort 3) of SMV. Cohort 4 only included secretor-negative subjects, and they were challenged with a dose of 1.2 x 107 GEC. Subjects remained in the hospital clinical research unit for five days after challenge. Stool, serum, vomitus, saliva samples and clinical information were collected. Subjects were also followed up on days 7, 15, 30, and 45 post-challenge for stool and serum sample collection. For this secondary data analysis, a total of 33 subjects who received the SMV inoculum and completed the study [9] were included in this study.
All the laboratory assays, including detection of anti-SMV IgG in serum, detection of secretor status, and quantification of SMV RNA in stool have been described previously [9, 11]. SMV infection was defined as RNA detection in any post-challenge stool sample by RT-PCR or specific RT-qPCR with CT values < 40 in duplicate reactions and/or anti-SMV serum IgG conversion by ELISA in any post-challenge serum sample vs. pre-challenge serum sample. Illness was defined as those infected with SMV who presented with diarrhea ≥3 loose or liquid stools or ≥300 g of loose or liquid stools in any continuous 24-h period, or one or more vomiting episodes during the inpatient period and with one other clinical sign or symptom such as fever, abdominal cramps, nausea, headache, chills, fatigue, or myalgia.