DETECTION OF IMMUNOGLOBULIN-M (IGM), IGA, AND IGG NORWALK VIRUS-SPECIFIC ANTIBODIES BY INDIRECT ENZYME-LINKED-IMMUNOSORBENT-ASSAY WITH BACULOVIRUS-EXPRESSED NORWALK VIRUS CAPSID ANTIGEN IN ADULT VOLUNTEERS CHALLENGED WITH NORWALK VIRUS

Pre- and postexposure sera collected from 17 adult volunteers challeng ed with Norwalk virus as described previously (D. Y. Graham, X. Jiang, T. Tanaka, A. Opekun, P. Madore, and M. K. Estes, J. Infect. Dis. 170 :34-43, 1994) were examined for Norwalk virus-specific immunoglobulin M (IgM), IgA, and IgG by indirect enzyme-linked immunosorbent assays w ith recombinant Norwalk virus antigen bound to the solid phase. Sixtee n of the 17 volunteers had evidence of past infection, all presenting with preexisting IgG antibody of high avidity; only one volunteer had no evidence of previous infection. Virus infection was detected in 14 of the 16 volunteers with evidence of past infection, and 9 of the inf ected volunteers had symptomatic illness. A significant rise in both v irus-specific IgA and IgG titers was detected after challenge in all o f the volunteers who became ill. Five of the asymptomatic volunteers w ho were infected had rising titers of virus-specific IgG, but only two of the five had a concomitant rise in their virus-specific IgA antibo dy titers. Antibody rises were detectable in eight of nine ill volunte ers 8 to 11 days after challenge but in the asymptomatic volunteers on ly after more than 15 days had elapsed. Virus-specific IgM was detecte d after challenge in all 14 infected volunteers. Between symptomatic a nd asymptomatic volunteers there were no significant differences in ti ters of virus-specific IgG and IgA in serum before challenge; however, there were significantly higher titers in symptomatic volunteers betw een 8 and >90 days after challenge for virus-specific IgG and 8 and 24 days after challenge for virus-specific IgA.