Immunogenicity of synthetic peptides representing antigenic determinants on the infectious hematopoietic necrosis virus glycoprotein

Abstract

Three peptides, P76, P226, and P268 representing 3 putative antigenic determinants on the glycoprotein of infectious hematopoietic necrosis virus (IHNV), were synthesized and injected into rainbow trout Oncorhynchus mykiss to assess their immunogenicity. Antisera extracted from the immunized trout were analyzed using an enzyme linked immunosorbent assay (ELISA) for the presence of antibodies that could bind to the peptides or to intact virions of IHNV. The antisera were also tested for neutralizing activity against iHNV by a complement-mediated neutralization assay. In general, recognition of the peptides and IHNV was low and only a few antibody binding patterns were demonstrated. Antisera from fish injected with P76 constructs recognized the homologous peptide more than the heterologous peptides, whereas antisera from fish inoculated with either P226 or P268 constructs recognized P76 equally, or better, than the homologous peptide; however, there was a high degree of individual variation within each treatment group. Neutralization activity was demonstrated by serum from a single fish injected with one of the peptides (P268) and from 7 of 10 positive control fish infected with an attenuated strain of IHNV. Possible explanations for the dichotomous immune responses are discussed. These results indicate we need to improve our overall understanding of the fish immune system in order to facilitate the development of an efficacious vaccine against IHNV.