Polypeptide composition of extracellular enveloped vaccinia virus

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Abstract
Extracellular enveloped vaccinia (EEV) virus grown in [rabbit cornea] SIRC and in [human cervical carcinoma] HeLa cells was purified by consecutive centrifugations in sucrose and cesium chloride gradients. A higher degree of purity was obtained with virus material prepared in SIRC cells. The polypeptides of purified EEV and INV (intracellular naked vaccinia) virus were compared in polyacrylamide slab gel electrophoresis. Three proteins (200,00 MW 200K [kilodalton], 95K and 13K) detected in HeLa-derived INV were absent in EEV. Two INV proteins (65K and 30K) occurred in reduced concentrations in EEV, while another INV protein (27K) was increased in EEV. INV from SIRC cells showed similar alterations of these proteins (with the exception of the 30K and 13K proteins). Detergent treatment, ether extraction and Pronase treatment showed that these 6 proteins are located at the surface of INV and are not necessary for infectivity. Eight proteins (210K, 110K, 89K, 42K, 37K, 21.5K, 21K and 20K) were detected in EEV that were absent from INV. Brij-58 treatment was employed to remove the envelope from EEV, resulting in the formation of naked particles and an envelope fraction which were separated on CsCl gradients. The envelope fraction contained all 8 proteins. Seven of the 8 proteins were glycoproteins, with the 37K protein being the only unglycosylated protein. Apparently, a processing of surface INV particle proteins occurs during envelopment. The resultant EEV particle is comprised of an INV particle with a modified surface composition enclosed in an envelope containing virus-specific proteins unique to EEV.