STUDIES ON THE PROPERTIES OF AFRICAN HORSE-SICKNESS VIRUS

Abstract

Various physico-chemical, serologic, and histopathologic properties of African horse-sickness (AHS) virus were studied using highly susceptible hosts, monkey kidney stable (MS) and African green monkey kidney (VERO) cell line cultures. AHS virus was resistant to ether, trypsin, and heat, but was readily inactivated in acid. Infectivity titers of AHS virus decreased markedly by storing infectious tissue culture fluids at temperatures between -20 C and -30 C. However, the infectivity was stable at -70 C. Inactivation of the virus was caused mainly by the salts used in virus suspensions. Infectivity of the virus was protected from inactivation by adding sugars (sucrose, lactose, or glucose) to the virus suspensions. Complement-fixing titers of horse serums were 2- to 4-fold higher when the homologous antigens were prepared in MS cells. By improving this technique, complement fixation tests might be used for typing AHS virus. There were no serologic cross reactions between AHS virus and arbo- and reoviruses. Distribution of antigens in infected MS and VERO cell cultures was investigated by the fluorescent antibody technique. In the early stage of infection of MS cells, many granular antigens appeared in the cytoplasm. At a later stage, in many infected cells, 1 or 2 relatively large masses of antigens were observed in the cytoplasm and a fluorescent spot in or on top of the nucleus. Antigens were present in rosary-like cytoplasmic inclusion bodies dispersed along the nuclear membranes of infected VERO cells and appeared in the cytoplasm at the late stage of infection, in numerous granules.