Proteins of bovine herpesvirus type 4 released into the culture medium of productively infected cells: identification of a 135K glycoprotein involved in viral attachment

Three bovine herpesvirus type 4 (BHV-4) proteins released into the culture medium of infected cells were identified, with M r values of 135K, 16K and 14.5K. Among these three proteins, two were precipitated by the monoclonal antibodies characterized in this work. One is a glycoprotein of 135K (gp8) which does not seem to be involved in BHV-4 neutralization. Moreover, this 135K glycoprotein adsorbed onto uninfected susceptible cells. The attachment of gp8 to cells was totally inhibited by the prior adsorption of unlabelled viral proteins. Moreover, anti-gp8 monoclonal antibodies were effective in inhibiting the adsorption of gp8. These results indicate that gp8 could be involved in BHV-4 attachment.