Broad neutralization coverage of HIV by multiple highly potent antibodies

Abstract

Broadly neutralizing antibodies against highly variable viral pathogens are much sought after to treat or protect against global circulating viruses. Here we probed the neutralizing antibody repertoires of four human immunodeficiency virus (HIV)-infected donors with remarkably broad and potent neutralizing responses and rescued 17 new monoclonal antibodies that neutralize broadly across clades. Many of the new monoclonal antibodies are almost tenfold more potent than the recently described PG9, PG16 and VRC01 broadly neutralizing monoclonal antibodies and 100-fold more potent than the original prototype HIV broadly neutralizing monoclonal antibodies. The monoclonal antibodies largely recapitulate the neutralization breadth found in the corresponding donor serum and many recognize novel epitopes on envelope (Env) glycoprotein gp120, illuminating new targets for vaccine design. Analysis of neutralization by the full complement of anti-HIV broadly neutralizing monoclonal antibodies now available reveals that certain combinations of antibodies should offer markedly more favourable coverage of the enormous diversity of global circulating viruses than others and these combinations might be sought in active or passive immunization regimes. Overall, the isolation of multiple HIV broadly neutralizing monoclonal antibodies from several donors that, in aggregate, provide broad coverage at low concentrations is a highly positive indicator for the eventual design of an effective antibody-based HIV vaccine.

© 2011 Macmillan Publishers Limited. All rights reserved

Figures

Figure 1. Neutralization activity of the newly identified PGT antibodies

a, Median neutralization potency against viruses neutralized with an IC50 < 50 μg/ml. The color-coding is as follows: yellow, 2 - 20 μg/ml; orange, 0.2 - 2 μg/ml; red, < 0.2 μg/ml. b, Neutralization breadth at different IC50 cut-offs. The color-coding is as follows: green, 1% to 30%; yellow, 30% to 60%; orange, 60% to 90%; red, > 90%.

Figure 2. Key MAbs fully recapitulate serum neutralization by the corresponding donor serum

Serum breadth was corelated with the breadth of the broadest MAb for each donor (% viruses neutralized at NT50 > 100 or IC50 < 50 μg/ml, respectively). Of note, MAbs isolated from donor 39 could not completely recapitulate the serum neutralization breadth.

Figure 3. Epitope mapping of PGT antibodies

a, Competition of PGT MAbs with sCD4 (soluble CD4), b12 (anti-CD4bs), 2G12 (anti-glycan), F425/b4e8 (anti-V3), X5 (CD4i), PG9 (anti-V1/V2 and V3, quaternary) and each other. Competition assays were performed by ELISA using gp120Bal or gp120 JR-FL, except for the PG9 competition assay, which was performed on the surface of JR-FLE168K or JR-CSF transfected cells. Boxes are color coded as follows: red, 75–100% competition; orange, 50–75% competition; yellow, 25–50% competition; gray, <25% competition. Experiments were performed in duplicate, and data represent an average of at least two independent experiments. b, Glycan microarray analysis (Consortium for Functional Glycomics, CFG, v 5.0) reveals that PGT MAbs 125, 126, 127, 128, and 130 contact Man8 (313), Man8GlcNAc2 (193), Man9 (314) and Man9GlcNAc2 (194) glycans directly. Only glycans structures with RFU (relative fluorescent units) > 3000 are shown. PGT-131 showed no detectable binding to the CFG glycan array but bound to Man9-oligodendrons (data not shown). Error bars represent standard deviation. c, d, Binding of PGT MAbs 125, 126, 127, 128 and 130 to gp120 is competed by Man9 oligodendrons but not Man4 oligodendrons. Binding of 131 to immobilized gp120 was too low to measure any competition.

Figure 4. Certain antibodies or antibody combinations are able to cover a broad range of HIV isolates at low, vaccine achievable, concentrations

a, Cumulative frequency distribution of IC50 values of broadly neutralizing MAbs tested against a 162-virus panel. The y-axis shows the cumulative frequency of IC50 values up to the concentration shown on the x-axis and can therefore also be interpreted as the breadth at a specific IC50 cut-off. b, c, Percent viruses covered by single MAbs (solid lines) or by at least one of the MAbs in dual combinations (dashed black lines) dependent on individual concentrations. The grey area in both panels is the coverage of 26 MAbs tested on the 162-virus panel (PGT121-123, PGT125-128, PGT130-131, PGT135-137, PGT141-145, PG9, PG16, PGC14, VRC01, PGV04, b12, 2G12, 4E10, 2F5) and depicts the theoretical maximal achievable coverage known to date.