Solid-phase immune electron microscopy with human immunoglobulin M for serotyping of Norwalk-like viruses

A solid-phase immune electron microscopy method that uses protein A, goat anti-human immunoglobulin M (IgM), and human serum is described. Evaluation of the method with different immunoglobulin fractions showed that human IgM constituted the major virus capture antibody. The method appeared to distinguish between two Norwalk-like virus serotypes and demonstrated specific IgM responses to these serotypes in infected individuals. Further work is being carried out to define the relationship of these two serotypes to the previously described Norwalk agent (A. Z. Kapikian, R. G. Wyatt, R. Dolin, T. S. Thornhill, A. R. Kalica, and R. M. Chanock, J. Virol. 10:1075-1081, 1972), and four subsequent hospital outbreaks are being studied.