The reported serological relatedness between the major
glycoproteins of human immunodeficiency virus (HIV gp120) and equine infectious anaemia virus (
EIAV gp90) was examined using purified
antigens in radioimmunoprecipitation (RIP), radioimmunoassay (RIA) and immunoblot assays with reference serum from
acquired immunodeficiency syndrome (
AIDS) patients, an anti-gp120 goat serum and EIAV-infected horse serum. To assess the contributions of
glycoprotein oligosaccharide and
peptide components to any observed reactivities,
antigens treated with
endoglycosidase F to remove
carbohydrate were assayed in parallel with the intact
glycoprotein. The results of the experiments indicated that the reactivity observed for each
antigen was dependent on the immunoassay employed. The RIP and RIA analyses demonstrated that HIV gp120 is equally reactive with the
AIDS patient serum, the goat anti-gp120 serum and the EIAV-infected horse serum, whereas the
EIAV gp90 reacted only with the horse serum. In immunoblot assays, the HIV gp120 reacted with
AIDS patient serum, but not with the EIAV-infected horse serum. Deglycosylation of the HIV gp120 evidently increased its reactivity with the
AIDS patient serum, had no significant effect on its reactivity with the goat antiserum, and essentially abolished its reactivity with the EIAV reference serum. Thus, it appears that the serological cross-reactivity observed between HIV gp120 and sera from EIAV-infected horses can be attributed to the
oligosaccharide rather than the
peptide components of the viral
glycoprotein. These studies also emphasize the necessity of employing several assay procedures in assessing lentivirus antigenicity.