Expression of Bluetongue Virus Group-specific Antigen VP3 in Insect Cells by a Baculovirus Vector: Its Use for the Detection of Bluetongue Virus Antibodies

DNA representing RNA segment 3 of bluetongue virus (BTV) serotype 17, corresponding to the gene that codes for a group-specific antigen VP3, has been inserted into a baculovirus transfer vector in lieu of the 5' coding region of the polyhedrin gene of Autographa californica nuclear polyhedrosis virus (AcNPV). After cotransfection of Spodoptera frugiperda cells with wild-type AcNPV DNA in the presence of the derived recombinant transfer vector DNA, polyhedrin-negative recombinant baculoviruses were recovered. When S. frugiperda cells were infected with one of these recombinant viruses, a protein that was similar in size and antigenic properties to the BTV VP3 protein was synthesized. Antibodies raised in mice or rabbits to the baculovirus-expressed VP3 protein immunoprecipitated the VP3 protein of BTV-17 as well as that of BTV-10. The expressed antigen reacted with antisera representing four U.S.A. BTV serotypes in an indirect ELISA test.