EVIDENCE OF A MAJOR NEUTRALIZABLE CONFORMATIONAL EPITOPE REGION ON VP2 OF INFECTIOUS PANCREATIC NECROSIS VIRUS

A collection of neutralizing monoclonal antibodies (MAbs) produced aga inst the LWVRT 60.1, Jasper and N1 strains of infectious pancreatic ne crosis virus (IPNV) were selected for the analysis of VP2 epitopes. Pr evious characterization of the LW and JA MAbs allowed the identificati on of continuous and discontinuous epitopes but the topological locali zation of these sites remained obscure. The ability of these MAbs to d ifferentiate individual epitopes was evaluated by additivity and compe tition assays using antigen-coated plates and by surface plasmon reson ance (SPR), an automated biosensor system that is able to retain the c onformation integrity of proteins. IPNV-neutralizing MAbs defined a ma jor, conformational-dependent and immunodominant area where continuous epitopes represent portions of a larger discontinuous epitope. Moreov er, weakly neutralizing MAbs could interact with internal sites, locat ed within the foldings of the polypeptide chain. Anti-VP2 MAbs prepare d against the European serotype N1 recognized and competed for epitope s present on the North American strains LWVRT 60.1 and Jasper. Attempt s to establish the proximity of VP2 and VP3 epitopes have been made by SPR. Results indicate that these major structural proteins do not ove rlap in the virion.