Reactions of Ugandan antisera with peptides encoded by V3 loop epitopes of human immunodeficiency virus type 1.

The specificities of antibodies reacting with peptides encoded by V3 loop apical epitopes were determined for sera from 230 seropositive Ugandans, including asymptomatic persons and AIDS patients, sampled between 1986 and 1992. Most (71%) of the sera reacted with the peptide encoded by HIV-MN, 59% reacted with a peptide containing a consensus sequence for Ugandan variants of the HIV-1 global subtype A (referred to as the Uganda A consensus), 59% reacted with a peptide containing a consensus sequence for Ugandan variants of the global subtype D (the Uganda D consensus); 19% of the sera also reacted with peptides encoded by the divergent Ugandan variant U31. There was no obvious correlation between the specificities of antibody binding and the V3 loop sequence of the corresponding virus isolate or provirus. Competitive inhibition and antibody adsorption experiments indicated that the MN peptide, the Uganda A consensus peptide, the Uganda D consensus peptide, and the U31 peptide were recognized by different sets of antibodies. Eighteen percent of the sera from AIDS patients and 26% of the sera from asymptomatic persons were monospecific for one of the MN, Uganda A, or Uganda D peptides. Whereas all except one of the singly reactive AIDS sera were specific for MN, 39% of the singly reactive asymptomatic sera were specific for MN, 39% for the Uganda A peptide, and 21% for the Uganda D peptides. We conclude that analysis of the specificities of antibodies against the V3 loop epitopes in sera from asymptomatic persons could provide useful epidemiological data about the prevalence of viral subtypes within a population.