Defective vaccinia virus particles in interferon-treated infected cells

Vaccinia virus particles formed in interferon-treated, infected cells have been isolated. These particles have been characterized with regard to polypeptide composition, and ability to adsorb, penetrate, uncoat, and synthesize proteins in infected cells. As determined by one-dimensional SDS-PAGE analysis, with interferon concentrations of 100-500 u/ml, the pattern of [35S]methionine-labeled virion proteins was not altered; higher doses of interferon resulted in decreased labeling of some proteins. However, interferon doses of 100-500 u/ml decreased phosphorylation of vaccinia virus basic core polypeptide (P-11) by 30-70%; the same doses of interferon decreased the labeling of virus glycoproteins by 40-80%. Virus purified from interferon-treated cells adsorb, penetrate, and uncoat to a lesser extent than virus control. During infection to cells, these virus particles caused shutoff and synthesized the same spectrum of viral proteins as normal virus. These findings show that there are protein alterations in vaccinia virus particles isolated from interferon-treated, infected cells. These alterations may contribute to limit the spread of virus infection.