Expression of the outer capsid protein VP5 of two bluetongue viruses, and synthesis of chimeric double-shelled virus-like particles using combinations of recombinant baculoviruses.

We have previously reported the assembly of virus-like particles (VLPs), consisting of the four major structural proteins of bluetongue virus (BTV), in Spodoptera frugiperda cells coinfected with recombinant baculoviruses (French et al. (1990). J. Virol. 64, 5695-5700). In this paper we report further studies using this system to assemble heterologous VLPs containing the outer capsid proteins (VP2 and VP5) of a range of different BTV serotypes. S. frugiperda cells were coinfected with three recombinant baculoviruses; a dual recombinant expressing VP3 and VP7 (of BTV-17 and -10, respectively) in combination with a single recombinant expressing VP2 of BTV-1, -2, -10, -11, 13, or -17 and an additional single recombinant expressing VP5 of BTV-2, BTV-10, or BTV-13. The resultant VLPs were purified and analyzed by electronmicroscopy, Western immunoblotting, and hemagglutination assays to determine whether double-shelled VLPs had been assembled. In the course of these experiments the VP2 proteins of all six available serotypes were successfully incorporated into VLPs. Particles from two different combinations of chimeric VLPs (having VP2 derived from BTV-1 or that of BTV-17) were used to raise antisera in guinea pigs. Both of these sera showed high neutralizing antibody titers against live BTV, indicating that heterologous VLPs may have potential for use in anti-BTV vaccines.