Complementation of recombinant baculoviruses by coinfection with wild-type virus facilitates production in insect larvae of antigenic proteins of hepatitis B virus and influenza virus

We describe the coinfection of insects with wild-type and recombinant baculoviruses in which the polyhedrin gene promoter is used to express hepatitis B virus envelope protein (hepatitis B virus surface antigen; HBsAg) or influenza A virus neuraminidase (NA). Viruses were administered per os to larvae of the cabbage looper, Trichoplusia ni, causing an infection that within 5 days resulted in the production of ≃0.15 mg of HBsAg per insect, representing 1.5% of the total extracted protein, or ≃2.8 mg of NA per insect, representing 28% of the total extractable protein. The HBsAg and NA produced by infected larvae were purified from insect lysates. These proteins were antigenic as determined by conformation-dependent immunoassays. The NA was enzymatically active with conventional substrates. The method of infection described allows genetic complementation by wild-type virus of recombinant viruses lacking the polyhedrin gene essential for infection per os and has implications for the high-yield production in insect larvae of other recombinant proteins of baculoviruses.