title: Characterizing anti-HIV monoclonal antibodies and immune sera by defining the mechanism of neutralization.
abstract: Understanding the nature of neutralization may provide information for crafting improvements in HIV vaccines. Using JR-FL as a prototype primary pseudovirus, we first investigated anti-HIV monoclonal antibodies (mAbs) in several neutralization formats designed to elucidate the timing of neutralization. MAb b12 was most effective before receptor binding, 2G12 neutralized effectively even after CD4 binding, and X5 and a V3 loop mAb (LE311) were inactive in a standard format but were induced by sCD4. Consistent with this latter finding, native PAGE indicated that X5 and V3 mAb binding to Envelope trimers was dependent on sCD4 binding. In contrast, 2F5 and 4E10 were active even post-CD4/CCR5 engagement. We next analyzed the neutralization mechanism of a panel of HIV+ donor plasmas of various potencies. All mediated high levels of post-CD4 neutralization that was not associated with activity in the standard format. None, however, neutralized effectively in the post-CD4/CCR5 format, suggesting that 2F5/4E10-like Abs were absent or at low concentrations. Finally, we analyzed a non-neutralizing plasma spiked with mAbs b12, 2G12 or 2F5, which resulted in increases in neutralization titers consistent with the activities of the mAbs. We conclude that these methods, together with other mapping approaches, may provide a better understanding of neutralization that could be useful in vaccine research.
authors.affiliation: Torrey Pines Institute for Molecular Studies, 3550 General Atomics Court, San Diego, CA 92121, USA.
authors.forename: Emma T
authors.initials: ET
authors.lastname: Crooks
authors.forename: Penny L
authors.initials: PL
authors.lastname: Moore
authors.forename: Douglas
authors.initials: D
authors.lastname: Richman
authors.forename: James
authors.initials: J
authors.lastname: Robinson
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Crooks
authors.forename: Michael
authors.initials: M
authors.lastname: Franti
authors.forename: Norbert
authors.initials: N
authors.lastname: Schülke
authors.forename: James M
authors.initials: JM
authors.lastname: Binley
mesh_terms: D016915:AIDS Vaccines / Q000276:immunology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D018604:Epitope Mapping; D015699:HIV Envelope Protein gp120 / Q000276:immunology; D015700:HIV Envelope Protein gp41 / Q000276:immunology; D015658:HIV Infections / Q000097:blood / Q000276:immunology; D015497:HIV-1 / Q000276:immunology*; D006801:Humans; D007106:Immune Sera / Q000276:immunology*; D051379:Mice; D009500:Neutralization Tests / Q000379:methods; D010446:Peptide Fragments / Q000276:immunology
chemical_list: D016915:AIDS Vaccines; D000911:Antibodies, Monoclonal; D015699:HIV Envelope Protein gp120; D015700:HIV Envelope Protein gp41; C059762:HIV envelope protein gp120 (305-321); D007106:Immune Sera; D010446:Peptide Fragments