VP2 protein carries neutralization epitopes in blotched snakehead virus (BSNV)

Abstract

A new aquabirnavirus (BSNV, blotched snakehead virus) was isolated from a persistently infected warmwater fish cell line (BSN) developed from blotched snakehead (Channa lucius). Four polypeptides of molecular mass 112 (polyprotein, PP), 91 (VP1), 44 (VP2) and 37 (VP3) kDa have been identified in BSNV. The reciprocal cross-neutralisation studies involving BSNV and four classical strains of infectious pancreatic necrosis virus (IPNV), strains WB, Sp, Ab and TV-1, revealed that BSNV antiserum was capable of neutralising only homologous virus while no cross reaction was evident against the other viruses. In order to further study and compare the antigenic properties of the virion structural proteins of BSNV and IPNV strain Sp, Western blot analysis of separated viral proteins was conducted using antisera against BSNV and IPNV Sp. The analysis indicated that VP2 protein (44 kDa) of BSNV alone was recognised by homologous antiserum while antiserum against IPNV Sp did not recognise any BSNV polypeptides. This, combined with weak recognition of the structural protein VP2 of IPNV Sp and SGV using BSNV antiserum showed that VP2 is probably the only protein expressed on the virion surface and this protein carries neutralisation epitopes in BSNV.