[Morphological proof of vaccinia virus multiplication in enucleated cells]

Primary monkey kidney cells were enucleated by the combined effect of cytochalasin B and ultracentrifugation. The effectiveness of enucleation in the experiments was 96-99%. Cytoplasts after 1-hour restoration were inoculated with the WR strain of vaccinia virus at a multiplicity of 0.1, 1.0, 10, and 50 PFU/cell. Within 20-21 h postinoculation when a marked cytopathic effect of the virus was evident, the material was fixed for electron microscopy. Serial ultrathin sections of the infected material were examined. Careful examination of the infected cytoplasts revealed all the usual stages of the morphogenetic cycle of vaccinia virus, from virion absorption by the host cell to clumps of mature virus particles in the cytoplasm and extracellularly. Vaccinia virus is thought to have morphologically complete replication cycle in the cytoplasts.