Immunoprecipitating human antigens associated with vesicular stomatitis virus grown in HeLa cells

Vesicular stomatitis virus (VSV) preparations made in HeLa cells, VSV(HeLa), appeared to contain non-viral structural proteins. This was suggested by neutralization of the virus with homologous and heterologous antisera made against VSV prepared in different cells. Antisera against uninfected HeLa cells failed to neutralize VSV(HeLa) but did immunoprecipitate the virus in the presence of Staphylococcus aureus. These immunoprecipitated VSV(HeLa) retained their infectivity, despite the presence of antibody and bacteria. The anti-HeLa cell serum did not react with VSV grown in rodent cells nor did anti-Vero cells serum immunoprecipitate VSV(HeLa). When the anti-HeLa cell serum was absorbed with whole HeLa cells, it no longer specifically precipitated VSV(HeLa). Because over 98% of infectious VSV(HeLa) was neutralizable by anti-VSV serum and immunoprecipitable by anti-HeLa serum, these virions were called mosaics. Physical identification of HeLa cell determinants on the mosaics was accomplished by further purification and radioiodination followed by selective immunoprecipitations with antisera. Two to three major bands with molecular weights around 75,000 Da were identified as HeLa cell determinants associated with the mosaic VSV(HeLa).