Reduced capacity of antibodies from patients infected with human immunodeficiency virus type 1 (HIV-1) group O to neutralize primary isolates of HIV-1 group M viruses

Neutralizing antibody patterns in sera of persons infected with human immunodeficiency virus type 1 (HIV-1) groups M and a to their homologous and heterologous primary isolates were determined in a peripheral blood mononuclear cell-based neutralization assay and correlated with their ability to bind to V3 loop synthetic peptides. Most HIV-1 group M sera (9/16) neutralized HIV-1 group a viruses, whereas fewer group a sera (3/13) only weakly neutralized HIV-1 group M viruses. Group M sera neutralizing HIV-1 group a viruses neutralized other HIV-1 group M viruses with titers of 1:10-1:1280. V3 loop binding capacity of sera did not reflect their neutralizing capacity of the homologous isolate. Despite the reduced neutralizing capacity of group a-infected patients ' sera to group M viruses, some group M- infected patients ' sera neutralized both HIV-1 group M and a isolates, suggesting that they share some conserved neutralizing epitopes. Nucleic acid sequence analysis of the envelope gene of hu-man immunodeficiency virus type 1 (HIV-1) isolates has thus far distinguished at least 8 subtypes, A-H [1-3], which to-gether are referred to as HIV-1 group M (for major). However, the relevance of these genetic subtypes in terms of neutraliza