Development and application of a monoclonal antibody against grouper iridovirus (GIV) major capsid protein.

The major capsid protein (MCP) is a main structural protein of iridoviruses, and is used as a marker for the identification, differentiation and classification of ranaviruses. In the present study, six monoclonal antibodies (mAbs) against recombinant MCP of grouper iridovirus (GIV) were produced and characterized. All of the six mAbs were of IgG1 isotype. Among the mAbs, GIV-MCP-mAb-21 showed the highest reactivity in ELISA and was used to further characterize the expression of GIV-MCP during viral replication. RT-PCR and Western blot analyses revealed that GIV-MCP is a late gene during GIV infection. By immunofluorescence assay, the presence of GIV-MCP was observed in not only the cytoplasm but also the nucleus of GIV-infected cells, a surprising finding that might indicate additional role of GIV-MCP. In conclusion, the newly established GIV-MCP-mAbs are a valuable tool for GIV diagnostic and future studies on GIV pathogenesis.