Characterization of the envelope proteins of pseudorabies virus

Abstract

Previously it was reported that among the proteins of purified pseudorabies virions there are 4 major glycoproteins. Several minor glycoproteins can also be identified by 2-dimensional gel electrophoresis. Removal of the viral envelope with Triton X-100 selectively removes from the virions all of the glycoproteins and several non-glycosylated proteins. Sedimentation analysis or chromatography of these proteins reveals that several are complexed with one another, some being covalently linked via disulfide bridges. Analysis of the proteins by immunoprecipitation with monoclonal antibodies reactive with the membrane proteins showed also that 3 of the 4 major virus glycoproteins (125K, 74K and 58K; gIIa, gIIb and gIIc, respectively) are linked covalently by disulfide bridges. All 3 extensive sequence homology as indicated by the identity of their antigenic determinants and by partial peptide mapping; they probably originate from a single protein precursor. The 4th major glycoprotein (98K; gIII) is not complexed to any other protein. Three minor glycoprotein (130K [gI], 98K [gIV] and 62K [gV]), which form a noncovalently linked complex with a 115K nonglycosylated protein, were also identified. Of the monoclonal antibodies used in this study, only those reactive with the major 98K glycoprotein (gIII) inhibit virus adsorption and neutralize virus infectivity in the absence of complement. All react with surface components of the virion, indicating that the proteins with which they react are exposed on the surface of the virions. A nomenclature for the pseudorabies virus glycoproteins is proposed.