Subtyping of human immunodeficiency virus type 1 strains by using antibodies specific for the third variable domain (V3) of gp120: results may be affected by divergent V3 sequences.

Human immunodeficiency virus type 1 serotype C was found in 545 of 712 Ethiopian patients by peptide enzyme immunoassay. Serotyping failed in 146 samples due to the absence of V3 antibodies or multiple reactivities. In 6 of 34 samples, discordant results were obtained by serotyping and genotyping, possibly due to divergent V3 sequences.