Potent neutralization of primary human immunodeficiency virus clade C isolates with a synergistic combination of human monoclonal antibodies raised against clade B

Objectives: We investigated the ability of several human neutralizing monoc lonal antibodies (mAbs), originally raised against human immunodeficiency v irus (HIV) clade B isolates, to neutralize primary clade C isolates as sing le agents and in combination. tudy Design/Methods: HIV clade C isolates from five different countries wer e tested for susceptibility to neutralization by anti-clade B mAbs in human peripheral blood mononuclear cells. Monoclonal antibody combinations were evaluated for possible synergy. Results: All 20 primary HIV clade C isolates could be neutralized 97.5% to 100% by a quadruple combination of mAbs IgG1b12. 2G12, 2F5, and 4E10. These mAbs recognized conserved epitopes and were highly synergistic, resulting in strong cross-clade neutralization. Conclusions: In our previous experiment, a synergistic combination of human neutralizing mABs protected all macaque neonates against oral challenge wi th a simian-human immunodeficiency virus encoding HIV env. Together, our da ta suggest that passive immunization with currently available anticlade B m Abs could play a role in preventing HIV clade C transmission through breast feeding.