EXPRESSION AND CHARACTERIZATION OF THE 2 OUTER CAPSID PROTEINS OF AFRICAN HORSESICKNESS VIRUS - THE ROLE OF VP2 IN VIRUS NEUTRALIZATION

African horsesickness virus (AHSV) is a gnat-transmitted member of the Orbivirus genus of the Reoviridae family. The virus has a genome of 1 0 double-stranded RNA species (L1-L3, M4-M6, S7-S10). The L2 and M6 ge nes of AHSV serotype 4 (AHSV-4) which encode the outer capsid proteins VP2 and VP5, respectively, were inserted into recombinant baculovirus es downstream of the baculovirus polyhedrin, or p10 promoters. Recombi nant baculoviruses expressing VP2, VP5, or VP2 and VP5 proteins of AHS V-4 were isolated. The expressed AHSV proteins were similar in size an d antigenic properties to those of viral AHSV-4. Expressed VP2 and VP5 proteins were purified to homogeneity and utilized to differentiate s era from vaccinated and infected horses. Antigens were also used to de termine whether any other AHSV serotypes are related to AHSV-4. The re sults indicated that AHSV-4 is distantly related to some serotypes (e. g., AHSV-2, -6, and -9) but not to others (e.g., AHSV-5 and -7). Hyper immune monospecific antisera raised in rabbits with purified VP2 neutr alized the infectivity of a virulent strain of AHSV-4 isolated from an infected horse during a recent outbreak of the disease in Spain. (C) 1994 Academic Press, Inc.