COMPARISON OF THE REACTIVITIES OF BACULOVIRUS-EXPRESSED RECOMBINANT NORWALK VIRUS CAPSID ANTIGEN WITH THOSE OF THE NATIVE NORWALK VIRUS-ANTIGEN IN SEROLOGIC ASSAYS AND SOME EPIDEMIOLOGIC OBSERVATIONS

Since the discovery of the Norwalk virus (NV) by immune electron micro scopy (IEM) in 1972, serologic studies with this virus have relied on particle-positive fecal material from infected volunteers as the sourc e of antigen because it has not been possible to propagate this virus in cell culture. However, the recent cloning of the W (strain 8FIIa) g enome and expression of the capsid protein in a baculovirus system to form ''virus-like particles'' has provided a consistent source of anti gen (designated rNV). The purpose of the present study was to compare the antigenicities of these rW particles with those of native W antige n derived from human fecal material by using well-characterized sera o btained from earlier studies. In IEM studies, the rNV antigen reacted with NV-specific antibodies in a manner similar to that observed previ ously when particle-positive fecal material was used as antigen. In ad dition, a direct enzyme-linked immunosorbent assay, in which the rW an tigen was used as antigen, proved efficient and specific for the detec tion of serologic responses to W compared with the previously establis hed techniques of IEM and blocking antibody immunoassays in which part icle-positive fecal material was used as the antigen. The availability of an unlimited source of antigen will enable serologic studies that will greatly increase our understanding of the epidemiology of W and i ts role in human enteric illness.