Significance of Extracellular Enveloped Virus in the in vitro and in vivo Dissemination of Vaccinia

Abstract

The significance of extracellular enveloped vaccinia (EEV) for the in vitro and in vivo dissemination of vaccinia virus was investigated. The quantity of in vitro released extracellular virus correlated very closely with the ability of 13 vaccinia strains to cause long-range spread of infection (comet formation) in cell cultures infected at low m.o.i. but was not correlated with plaque size. The kinetics of virus spread after low m.o.i. was related to the amount of virus released from primary infected cells but not to their content of intracellular naked vaccinia (INV). Most extracellular vaccinia virus from IHD-J-infected RK-13 cells banded in CsCl density gradients as EEV (88%) while very little banded as INV (2%). Antisera to the envelope prevented comet formation while antisera to INV did not.