Immunogenicity of a recombinant infectious hematopoietic necrosis virus glycoprotein produced in insect cells

Abstract

A recombinant infectious hematopoietic necrosis virus (IHNV) glycoprotein (G protein), produced in Spodoptera frugiperda (Sf9) cells following infection with a baculovirus vector containing the full-length (1.6 kb) glycoprotein gene, provided very limited protection in rainbow trout Oncorhynchus mykiss challenged with IHNV. Fish were injected intraperitoneally (i.p.) with Sf9 cells grown at 20 degrees C (RecGlow) or 27 degrees C (RecGhigh) expressing the glycoprotein gene. Various antigen (Ag) preparations were administered to adult rainbow trout or rainbow trout fry. Sera collected from adult fish were evaluated for IHNV neutralization activity by a complement-dependent neutralization assay. Anti-IHNV neutralizing activity was observed in sera, but the percent of fish responding was significantly lower (p < 0.05) in comparison to fish immunized with a low virulence strain of IHNV (LV-IHNV). A small number of fish immunized with RecGlow or RecGhigh possessed IHNV G protein specific antibodies (Abs) in their serum. Cumulative mortality (CM) of rainbow trout fry (mean weight, 1 g) vaccinated by i.p. injection of freeze/thawed Sf9 cells producing RecGlow was 18% in initial trials following IHNV challenge. This level of protection was significant (p < 0.05) but was not long lasting, and neutralizing Abs were not detected in pooled serum samples. When trout fry (mean weight, 0.6 g) were vaccinated with supernatant collected from sonicated Sf9 cells, Sf9 cells producing RecGlow, or Sf9 cells producing RecGhigh, CM averaged 46%. Protection was enhanced over negative controls, but not the positive controls (2% CM), suggesting that in the first trial soluble cellular proteins may have provided some level of non-specific protection, regardless of recombinant protein expression. Although some immunity was elicited in fish, and RecGlow provided short-term protection from IHNV, Ab-mediated protection could not be demonstrated. The results suggest that recombinant G proteins produced in insect cells lack the immunogenicity associated with vaccination of fish with an attenuated strain of IHNV.

The NV Gene of Snakehead Rhabdovirus (SHRV) Is Not Required for Pathogenesis, and a Heterologous Glycoprotein Can Be Incorporated into the SHRV Envelope

“…at 30°C. The difference in optimal growth temperatures for the two viruses might result from conformational instability of the IHNV glycoprotein at 30°C as reported by Cain et al (5).…”

Cellular and molecular immune responses of the sea bass (Dicentrarchus labrax) experimentally infected with betanodavirus

“…Consequently, much effort is required to investigate immune response of sea bass against VER antigens. The main viral antigen employed to induce specific antibodies and activate a protective immune memory is the capsid protein, largely shown to be immunogenic in fish [1,2,19,20]. Moreover, immunisation of sea bass with synthetic peptides derived from the VERv capsid may induce antibody titers [20] and triggers the B cell immune responses [21].…”

“…The knowledge of immune defence mechanisms against viral infection in teleost fish species is a matter of intense investigation and interesting results have been obtained through the study of protective mechanisms in vivo, by evaluating the gene expression of immunoregulatory peptides, as well as by analysing anti-virus specific antibody levels [1,2]. Antiviral activities of fish species include the activation of innate and acquired immune responses [3e5], with the promising possibilities offered by genetic vaccination to control the spreading of virosis induced by VHSV and IHNV in salmonid species [6,7].…”

Exogenous antigens and the stimulation of MHC class I restricted cell-mediated cytotoxicity: possible strategies for fish vaccines

“…The N protein of VSV contained in cellular debris elicits a CTL response in mice (Bachmann et al, 1994b). Interesting in this respect is that immunisation of trout fry with recombinant IHNV G protein in freeze/thawed insect cells induced some protection, although no neutralising antibodies could be detected (Cain et al, 1999). Several studies indicate that ISCOMs containing rhabdovirus antigens stimulate a CTL response in mammals and that these are promising vaccine components.…”