CHARACTERIZATION OF HUMAN SEROTYPE-1 ASTROVIRUS-NEUTRALIZING EPITOPES

Astroviruses are important agents of pediatric gastroenteritis, To bet ter understand astrovirus antigenic structure and the basis of protect ive immunity, monoclonal antibodies (MAbs) were produced against serot ype 1 human astrovirus, Four MAbs were generated, One MAb (8G4) was no nneutralizing but reacted to all seven serotypes of astrovirus by enzy me-linked immunosorbentassay (ELISA) and immunoperoxidase staining of infected cells, Three MAbs were found to have potent neutralizing acti vity against astrovirus. The first (5B7) was serotype 1 specific, anot her (7C2) neutralized all seven human astrovirus serotypes, while the third (3B2) neutralized serotypes 1 and 7. Immunoprecipitation of radi olabeled astrovirus proteins from supernatants of astrovirus-infected cells showed that all three neutralizing antibodies reacted with VP29, MAb 5B7 also reacted strongly with VP26, A competition ELISA showed t hat all three neutralizing antibodies competed with each other for bin ding to purified astrovirus virions, suggesting that their epitopes we re topographically in close proximity, None of the neutralizing MAbs c ompeted with nonneutralizing MAb 8G4, The neutralizing MAbs were used to select antigenic variant astroviruses, which were then studied in n eutralization assays, These assays also suggested a close relationship between the respective epitopes, All three neutralizing MAbs were abl e to prevent attachment of radiolabeled astrovirus particles to human Caco 2 intestinal cell monolayers, Taken together, these data suggest that the astrovirus capsid protein VP29 may be important in viral neut ralization, heterotypic immunity, and virus attachment to target cells .