Reversal of Anti-viral Effects of Rifampicin

Abstract

RIFAMPICIN prevents vaccinia virus growth^1,2 by a still undefined mechanism. Viral DNA and early and late species of messenger RNA are synthesized in the presence of rifampicin^3–6; early and late viral proteins are also made, although synthesis of the latter declines sooner than in the absence of the drug^3,4,6,7. Rifampicin does not inhibit the RNA polymerase activity contained within purified vaccinia virus particles^3,5,7–9, but the drug prevents the formation of particulate RNA polymerase activity⁵. This enzyme can ordinarily be demonstrated, at late times in vaccinia-infected cells, after treatment of cytoplasmic fractions with mercaptoethanol and detergents^10–13. Rifampicin has also been found to block vaccinia virus assembly during the formation of the viral envelope and preceding the appearance of virus particles^6,14. The sequence of events which follows the removal of rifampicin has now been examined in order to correlate the effects observed on the formation of the late particulate RNA polymerase activity and on the assembly of viral envelopes.