Presentation of hepatitis B virus preS2 epitope on bluetongue virus core-like particles.

A chimeric protein containing most of the hepatitis B virus preS2 region (amino acid residues 1-48) upstream to, and colinear with the amino-terminus of bluetongue virus VP7 protein (preS2-VP7) was expressed by a recombinant Autographa californica nuclear polyhedrosis virus (AcNPV). The chimeric protein formed BTV core-like particles (CLPs) in Spodoptera frugiperda cells only when the cells were coinfected with this recombinant virus and a recombinant baculovirus that expresses unmodified VP7 and VP3 of BTV. The ratio of preS2-VP7 incorporated into CLPs was influenced by the relative multiplicities of infection of the two viruses. Immunoelectron microscopy of the chimeric particles indicated that the preS2 epitope was exposed on the surface of the CLPs. When insect cells were coinfected with the preS2-VP7 recombinant virus and a baculovirus vector that synthesized only the VP3 protein, no CLPs were identified.