Localization of pestiviral envelope proteins E-rns and E2 at the cell surface and on isolated particles

The glycoproteins E-rns of classical swine fever virus (CSFV) and E-rns and E2 of bovine viral diarrhoea virus (BVDV) are shown to be located at the s urface of infected cells by the use of indirect immunofluorescence and by c ytofluorometric analysis. The positive immunostaining of the cell surface w as further analysed by immunogold electron microscopy and it could be shown that only extracellular virions were labelled. Gold granules were not seen at the cellular plasma membrane. In contrast to BVDV E2, the CSFV E2 of vi rions sticking to the plasma membrane was not accessible to the respective monoclonal antibodies. However, CSFV particles isolated from culture supern atant were able to bind both monoclonal anti-E-rns and anti-E2 antibodies. For CSFV and BVDV, binding of anti-E-rns antibodies to the virions was more pronounced than that of anti-E2. This finding was unexpected since E2 is c onsidered to be the immunodominant glycoprotein.