title: 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.
abstract: The 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.
authors: Duke Human Vaccine Institute and Department of Medicine, Duke University School of Medicine, Durham, North Carolina 27710, USA.
authors: Elin S
authors: ES
authors: Gray
authors: M Anthony
authors: MA
authors: Moody
authors: Constantinos Kurt
authors: CK
authors: Wibmer
authors: Xi
authors: X
authors: Chen
authors: Dawn
authors: D
authors: Marshall
authors: Joshua
authors: J
authors: Amos
authors: Penny L
authors: PL
authors: Moore
authors: Andrew
authors: A
authors: Foulger
authors: Jae-Sung
authors: JS
authors: Yu
authors: Bronwen
authors: B
authors: Lambson
authors: Salim
authors: S
authors: Abdool Karim
authors: John
authors: J
authors: Whitesides
authors: Georgia D
authors: GD
authors: Tomaras
authors: Barton F
authors: BF
authors: Haynes
authors: Lynn
authors: L
authors: Morris
authors: Hua-Xin
authors: HX
authors: Liao
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