SUBCORE-LIKE 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

The genes encoding the two major core proteins (VP2 and VP7) of Broadh aven (BRD) virus, a tick-borne orbivirus, were inserted into the genom e of Autographa californica nuclear polyhedrosis virus (AcNPV) under t he control of copies of the AcNPV polyhedrin promoter to produce two r ecombinant baculoviruses. Infection of Spodoptera frugiperda (Sf) cell s with a recombinant AcNPV that synthesized BRDV VP2 produced large nu mbers of BRDV subcore-like particles. Co-infection of cells with the t wo recombinants that made either BRDV VP2 or VP7 produced core-like pa rticles similar in appearance to authentic BRDV cores. No evidence was obtained for the formation of core-like particles between the major c ore 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, indic ating that in this respect the proteins of these two orbiviruses are i ncompatible, unlike the situation previously described for epizootic h aemorrhagic disease virus and BTV core proteins.