Viral interference in TO-2 cells infected with IPN virus isolated from clam, Meretrix lusoria.

The viral interference exhibited by HB-1 virus, a strain of infectious pancreatic necrosis virus (IPNV) isolated from hard clam, Meretrix lusoria, was studied. The TO-2 cells infected with serial passage HB-1 virus at 100 to 10-4 dilutions showed that viral interference was related to the degree of dilution of virus inoculum. The specific viral antigens were detected with immunofluorescent antibody stain technique in TO-2 cells which survived from high multiplicity infection of HB-1 virus. The virus yield in culture fluid from a series of 20 serial undiluted or diluted passages indicated that serial undiluted or low-diluted (10-1 to 10-2) passaging of HB-1 virus could induce autointerference in TO-2 cells. The defective interfering (DI) particles in the virus samples were considered to be responsible for the interference.The SDS-PAGE analyses for the polypeptide composition of virions from serial diluted and undiluted passaging showed that there were differences in β group. The truncated β polypeptides were regarded to be specific polypeptides produced by DI particles generated by serial undiluted passaging. We, thus, provided new information concerning IPN DI particles by comparing the properties of the virions produced by serial diluted and undiluted passaging of HB-1 virus, a strain of IPNV.