Immunogenicity properties of authentic and heterologously synthesized structural protein VP2 of infectious pancreatic necrosis virus.

The sole coat protein VP2 of infectious pancreatic necrosis virus (IPNV) was isolated and purified from intact virions, propagated in CHSE-214 cells. Likewise was the full-length VP2 protein isolated and purified upon cloning and expression of the corresponding complete gene in E. coli. The two purified proteins of different synthetic origins carrying identical primary structures were utilized in an immunization program using a rabbit model. Sera obtained against both immunogens react equally well with authentic and recombinant VP2 in Western blots and ELISAs. Also, the total net binding forces as determined by avidity index (AI) calculations were high and of similar stature, exceeding 80. An IPNV infection of susceptible and permissive CHSE-214 cells could only be neutralized by IgG preparations obtained from rabbits immunized with authentic VP2. Only such antibodies were able to aggregate and sediment radiolabeled virions in glycerol gradients upon rate zonal centrifugations. The presence of sugar moieties on the authentic protein is suggested to be of pivotal importance in eliciting an immune response capable of preventing infection in cell cultures in vitro.