Expression of recombinant capsid proteins of Chitta virus, a genogroup II Norwalk virus, and development of an ELISA to detect the viral antigen

The second open reading frame (ORF2) gene of the Chitta virus (CHV) was clo ned to construct a recombinant baculovirus, The CHV ORF2 is predicted to en code a capsid protein of 535 amino acids (aa), CHV showed a high aa identit y in the capsid region with genogroup II Norwalk virus (NV) (65-85 %), but a low aa identity with genogroup I NV (44-46%), Phylogenetic analysis of th e ORF2 gene demonstrated that CHV is genetically closely related to the Haw aii virus included in genogroup II NV. The recombinant capsid protein of CH V (rCHV) self-assembled to form empty virus-like particles (VLPs) when expr essed in insect cells with the recombinant baculovirus. An enzyme-linked im munosorbent assay (ELISA) based on antisera to rCHV was developed to detect CHV antigen in stools, The antigen ELISA appeared to be highly specific to both rCHV and CHV-like strains. In addition, combined use of antigen ELISA s using antibodies against two antigenically distinct recombinant VLPs, the recombinant Chiba virus (rCV) and recombinant Seto virus (rSEV), enabled u s to determine the genetic as well as antigenic relationship among these th ree viruses.