An autoradiographic study on the intracellular development of vaccinia virus.

Abstract

Abstract The multiplication of intracellular vaccinia virus in HeLa cells was followed over the complete growth cycle by plaque assay after sonic disintegration of the infected monolayers. A constant proportion of the adsorbed virus lost identity as plaque-forming units immediately after infection. These particles were considered in eclipse since this loss persisted throughout the lag phase. Nuclear radioactivity of host cells prelabeled with thymidine- H 3 was not transferred appreciably to the cytoplasm upon infection, indicating that host deoxyribonucleic acid was not incorporated into the newly synthesized virus. Occasional bizarre transfer of nuclear label to the cytoplasm was observed. Infection stimulated an early nuclear response which was observed most readily with prelabeled cells. Thymidine- H 3 was incorporated into the cytoplasm of cells labeled after infection, and the sites of accumulation of label were considered to be the sites of viral DNA synthesis. Thymidine- H 3 accumulated most rapidly during the period between 1.5 and 6 hours after infection. The virus units migrated outward from the centers of synthesis after formation and dispersed throughout the cytoplasm. Inclusion bodies lost label when observed during the late hours following infection, and the radioactivity was found throughout the extensions of the cell.