Serotype-specific antigen ELISA for detection of Chiba virus in stools

Chiba virus (CV), a Norwalk-like virus (NLV), was first identified as a cau se of oyster-associated outbreak of gastroenteritis that occurred in Chiba prefecture, Japan, in 1987. An enzyme-linked immunosorbent assay (ELISA), b ased on hyperimmune antisera to recombinant baculovirus-expressed capsid pr oteins of CV (rCV), was developed to detect CV antigen in stools. No cross- reactions were observed with other enteric viruses including enteroviruses, rotaviruses, astroviruses, or enteric adenoviruses. The ELISA was used to screen 101 stools collected from 16 oyster-associated outbreaks of acute ga stroenteritis. Twelve stools (11.9%) from seven outbreaks were positive for CV antigen. Ten rCV ELISA-positive strains were confirmed by RT-PCR and nu cleotide sequencing. ELISA positive strains showed 96-100% nucleotide seque nce identity to each other, though they were obtained nine years apart. Phy logenetic analysis demonstrated that all ten strains clustered with the pro totype CV in genogroup I viruses. We concluded that the antigen ELISA descr ibed in this study is highly type-specific, and that this method should be useful for epidemiological surveys of Chiba virus infections. (C) 2000 Wile y-Liss, Inc.