DAO 36:67-72 (1999)  -  doi:10.3354/dao036067

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

Kenneth D. Cain1,*, Scott E. LaPatra2, Bill Shewmaker2, Jerry Jones2, Katherine M. Byrne1, Sandra S. Ristow1,**

1Dept. of Animal Sciences, Washington State University, Pullman, Washington 99164-6351, USA
2Clear Springs Foods, Inc., PO Box 712, Buhl, Idaho 83316, USA
*Present address: Immunobiology Unit, University of Technology Sydney, Gore Hill, New South Wales 2065, Australia
**Addressee for correspondence. E-mail:

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°C (RecGlow) or 27°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.

KEY WORDS: IHNV · Baculovirus · Recombinant glycoprotein · Immunization · Rainbow trout

Full text in pdf format