Characterization of intracellular and extracellular vaccinia virus variants: N1-isonicotinoyl-N2-3-methyl-4-chlorobenzoylhydrazine interferes with cytoplasmic virus dissemination and release.

Infectious vaccinia virus can be purified from whole cells by experimentally induced lysis (intracellular virus) or from supernatant growth medium (extracellular virus). Extracellular virus and intracellular virus differed by buoyant density (1.237 versus 1.272 g/cm3), phospholipid content and composition, and polypeptide pattern. Differences in structural polypeptides on the virus surface could be detected by lactoperoxidase-catalyzed radioiodination or Brij treatment. Characteristic of extracellular virus was an additional polypeptide, with a molecular weight of 37,000 (37K), which represented 5 to 7% of the total particle protein. Antibodies to the 37K protein detected only some of the cell-associated particles late in normal infection. Upon treatment of infected cultures with N1-isonicotinoyl-N2-3-methyl-4-chlorobenzoylhydrazine, a drug which prevents vaccinia virus release, no particle-associated 37K protein could be detected. In all other properties tested so far, except for a slight difference in phospholipid composition, the virus obtained in the presence of the drug resembled the normal intracellular virus. N1-Isonicotinoyl-N2-3-methyl-4-chlorobenzoylhydrazine prevented vesicularization of intracellular viral particles. Lack of vesicularization was accompanied by the absence of particle-associated 37K viral protein and seemed to correlate with an inhibition of virus dissemination to the cell periphery.