Subcore- and core-like particles of Broadhaven virus (BRDV), a tick-borne orbivirus, synthesized from baculovirus expressed VP2 and VP7, the major core proteins of BRDV

Abstract

The genes encoding the two major core proteins (VP2 and VP7) of Broadhaven (BRD) virus, a tick-borne orbivirus, were inserted into the genome of Autographa californica nuclear polyhedrosis virus (AcNPV) under the control of copies of the AcNPV polyhedrin promoter to produce two recombinant baculoviruses. Infection of Spodoptera frugiperda (Sf) cells with a recombinant AcNPV that synthesized BRDV VP2 produced large numbers of BRDV subcore-like particles. Co-infection of cells with the two recombinants that made either BRDV VP2 or VP7 produced core-like particles similar in appearance to authentic BRDV cores. No evidence was obtained for the formation of core-like particles between the major core proteins of BRDV and those of bluetongue virus (BTV) following the co-expression of BRDV VP2 and BTV VP7, or BRDV VP7 and BTV VP3, indicating that in this respect the proteins of these two orbiviruses are incompatible, unlike the situation previously described for epizootic haemorrhagic disease virus and BTV core proteins.