Antigen analysis of red sea bream iridovirus and comparison with other fish iridoviruses

Red sea bream iridovirus (RSIV) causes epizootic disease outbreaks involving mortality in cultured marine fishes in southwestern Japan. The reactivities of anti-RSIV polyclonal antibody and the monoclonal antibodies (MAbs) against RSIV to the RSIV isolates from various cultured marine fish species and diverse geographic regions were examined. All the isolates showed similar reaction patterns by an indirect immunofluorescence (IF) test with anti-RSIV serum. However, some MAbs reacted with restricted number of RSIV isolates. The antigenic relationship between RSIV and three iridoviruses associated with systemic infection in fish, epizootic haematopoietic necrosis virus (EHNV), the iridovirus isolated from sheatfish (SFIV) and the iridovirus isolated from grouper (GN) was examined. Although cross reactivities were observed between RSIV and other fish iridoviruses by IF test or immunoprecipitation test using anti-RSIV serum, none of the MAbs against RSIV reacted with EHNV, SFIV or GIV infected cells.