Inhibition by rifampin of African swine fever virus replication in tissue culture.

Vaccinia virus and African swine fever virus are deoxyribonucleic acid viruses of cytoplasmic origin. The fact that rifampin inhibits the replication of the former virus led to an investigation of its effect on African swine fever virus. The virus used was cytopathogenic to a PK-15 cell line, hemadsorbing in pig leukocyte cultures and lethal to pigs. Rifampin clearly inhibited the multiplication and cytopathogenicity of the virus in PK-15 cells. There was a 1- to 5-log reduction in virus titer depending upon the rifampin concentration, the multiplicity of infection, and the time after infection. Inhibition was greatest at a concentration of 200 mug of rifampin/ml. The drug was not viricidal per se, and the inhibition of virus replication was not due to the cell-granulating effect of rifampin since cultures which were transiently pretreated for long as 90 hr with 200 mug of drug/ml supported viral replication to the same degree as untreated cultures.