Defining Human Immunodeficiency Virus (HIV) Type 1 Immunotypes with Six Human Monoclonal Antibodies

Studies of HIV-1 immunological relatedness have revealed that genetic diversity does not parallel antigenic diversity and have recently shown that HIV-1 strains from different geographic regions from around the world can be grouped into a small number of immunologically defined groups (immunotypes). Previously, the binding patterns of 28 monoclonal antibodies (mAbs) (specific for V3 and C5 of gp120 and cluster I of gp41) with 26 HIV-1 virions obtained globally were determined in a virus binding assay. Analysis of the binding patterns of these 728 mAb/virus combinations now reveals that a particular subset containing six of the 28 mAbs can correctly immunotype 24 of the 26 isolates (92%) into three immunotypes. Like the original panel of mAbs, the subset of six mAbs identified was directed against epitopes in the V3 and C5 regions of gp 120 as well as cluster I of gp41. The binding patterns ("profiles") of these six mAbs with 24 additional HIV-1 virions from Cameroon confirmed that epitopes in V3 and C5 of gp120 and cluster I of gp41 are well exposed on these viruses. Multivariate analysis of the binding patterns of these six mAbs with all 50 viruses (26 obtained globally and 24 obtained from Cameroon) indicates that the viruses from Cameroon have binding profiles similar to viruses from the rest of the world and can be classified into the same three immunotypes that were previously described. This study suggests that a vaccine against HIV-1 need not be based on geographic origin of the virus or on clade, but may better be based on antigenic properties that classify the plethora of different HIV-1 viruses into immunologically defined groups.