VIRAL SHEDDING AND FECAL IGA RESPONSE AFTER NORWALK VIRUS-INFECTION

Protection is not conferred by preexposure to Norwalk virus (NV). By u se of an ELISA with baculovirus-expressed recombinant NV (rNV) capsid protein, the pattern of NV fecal shedding and the protective effect of rNV-specific fecal IgA (flgA) were investigated in volunteers who wer e repeatedly challenged with NV. After the first challenge, ill volunt eers were significantly more likely than well volunteers to have NV an tigen in their stool (P < .05). After challenge, antigen shedding was detected on days 1-13; ill volunteers shed the antigen longer (P = .02 ). A higher prechallenge rNV-specific flgA geometric mean titer was fo und in ill compared with well volunteers (P < .05) and in infected ver sus noninfected volunteers (P < .05). NV shedding was common after inf ection and was present up to 2 weeks after challenge. Preexisting rNV- specific flgA, like serum IgG, is not protective and may be a marker f or symptomatic disease.