SYNTHESIS OF RECOMBINANT BACULOVIRUSES EXPRESSING THE OUTER CAPSID PROTEIN VP2 OF 5 BTV SEROTYPES AND THE INDUCTION OF NEUTRALIZING ANTIBODIES TO HOMOLOGOUS AND HETEROLOGOUS BTV SEROTYPES

DNA representing RNA segment L2 of 5 different bluetongue virus (BTV) serotypes (BTV-1, -2, -11, -13 and -17) corresponding to the gene that codes for the BTV neutralization antigen VP2, have been inserted indi vidually into baculovirus transfer vectors in lieu of the 5' coding re gion of the polyhedrin gene of Autographa californica nuclear polyhedr osis virus (AcNPV). After co-transfection of Spodoptera frugiperda cel ls with wild-type AcNPV DNA in the presence of the derived transfer ve ctor DNAs, polyhedrin-negative recombinant baculoviruses were recovere d. When S. frugiperda cells were infected with each of these viruses, protein was made similar in size and antigenic properties to the authe ntic BTV VP2 protein. To evaluate the biological activities of these p roteins, antibodies were raised to them in guinea pigs. The neutraliza tion capabilities of these antisera were tested against homologous and , for two of the higher titered sera, heterologous BTV serotypes. Each antiserum neutralized the infectivity of the homologous virus serotyp e. In heterologous virus challenges, the serum raised to the VP2 prote in of BTV-13 also neutralized the infectivity of BTV-1, and to lesser extents BTV3, -16, -8 and -9 (BTV-2, -10, -11, -15 were not tested). T he serum raised to the VP2 of BTV-17 neutralized BTV-20 and -21, and t o lesser extents BTV-4 and -8 (again, BTV-2, -10, -11, -15 were not te sted).