Gray, Elin Solomonovna.Moody, Michael Anthony.Wibmer, Constantinos Kurt.Chen, Xi.Marshall, Dawn J.Amos, Joshua.Moore, Penelope L.Foulger, Andrew.Yu, Jae-Sung.Lambson, Bronwen Elizabeth.Abdool Karim, Salim Safurdeen.Whitesides, John.Tomaras, Georgia D.Haynes, Barton F.Morris, Lynn.Liao, Hua-Xin.2012-11-192012-11-1920112011Gray E.S., et al. 2011. Isolation of a monoclonal antibody that targets the alpha-2 helix of gp120 and represents the initial autologous neutralizing-antibody response in an HIV-1 subtype C-infected individual. J. Virol. 85 (15), pp.7719–7729.0022-538Xhttp://dx.doi.org/10.1128/JVI.00563-11http://hdl.handle.net/10413/7884The C3-V4 region is a major target of autologous neutralizing antibodies in HIV-1 subtype C infection. We previously identified a Center for AIDS Program of Research in South Africa (CAPRISA) participant, CAP88, who developed a potent neutralizing-antibody response within 3 months of infection that targeted an epitope in the C3 region of the HIV-1 envelope (P. L. Moore et al., PLoS Pathog. 5:e1000598, 2009). Here we showed that these type-specific antibodies could be adsorbed using recombinant gp120 from the transmitted/founder virus from CAP88 but not by gp120 made from other isolates. Furthermore, this activity could be depleted using a chimeric gp120 protein that contained only the C3 region from the CAP88 viral envelope engrafted onto the unrelated CAP63 viral envelope (called 63-88C3). On the basis of this, a differential sorting of memory B cells was performed using gp120s made from 63-88C3 and CAP63 labeled with different fluorochromes as positive and negative probes, respectively. This strategy resulted in the isolation of a highly specific monoclonal antibody (MAb), called CAP88-CH06, that neutralized the CAP88 transmitted/founder virus and viruses from acute infection but was unable to neutralize CAP88 viruses isolated at 6 and 12 months postinfection. The latter viruses contained 2 amino acid changes in the alpha-2 helix of C3 that mediated escape from this MAb. One of these changes involved the introduction of an N-linked glycan at position 339 that occluded the epitope, while the other mutation (either E343K or E350K) was a charge change. Our data validate the use of differential sorting to isolate a MAb targeting a specific epitope in the envelope glycoprotein and provided insights into the mechanisms of autologous neutralization escape.enHIV antibodies.HIV infections--Immunology.Antibodies, Monoclonal.Peer reviewed journal article