Baculovirus-expressed nonstructural protein NS2 of bluetongue virus induces a cytotoxic T-cell response in mice which affords partial protection.

Virus-specific cytotoxic T lymphocytes were generated in two strains of mice (BALB/c and CBA/Ca) against baculovirus recombinant proteins (minor and nonstructural) derived from bluetongue virus serotype 10. Immunization of mice with recombinant baculovirus insect cell extracts expressing the nonstructural protein NS2 (Bac-NS2) conferred partial protection against infection with vaccinia virus expressing the NS2 protein. This protective immunity was mediated by CD8+ cells. In contrast, no protection was observed when mice were immunized with similarly expressed Bac-NS1 or -NS3 or the virion minor structural proteins (Bac-VP1, -VP4, or -VP6). Furthermore, the in vitro cytotoxicity activity of T cells derived from immunized animals did not correlate to the protective efficacy of baculovirus recombinant proteins. The implications of this work with regard to the design of noninfectious subunit vaccines are discussed.