Antigenic reactivity of the major glycoprotein of equine infectious anemia virus, a retrovirus.

The immunogenic contributions of the carbohydrate and peptide portions of the major envelope glycoprotein of equine infections anemia virus, EIAV gp90, were analyzed by measuring the effects of specific glycosidase and protease digestions on the reactivity of the glycoprotein with immune sera from infected horses. The results of both direct and competitive radioimmunoassay demonstrated that immune sera contained antibodies reactive with both the carbohydrate and protein moieties of EIAV gp90, with the predominant reactivity apparently against the gp90 peptide epitopes. These results contrast with previous descriptions of retrovirus glycoprotein antigenicity in which antigenic reactivity was attributed exclusively to protein (Friend murine leukemia virus) or to carbohydrate (bovine leukemia virus). Thus EIAV gp90 displays a complex antigenicity which must be taken into consideration in analyzing the biochemical nature of antigenic variation of the virus during persistent infections in horses.