Broad and potent neutralizing antibodies from an African donor reveal a new HIV-1 vaccine target.
09 Oct 2009-Science (American Association for the Advancement of Science)-Vol. 326, Iss: 5950, pp 285-289
TL;DR: High-throughput screening has revealed two new broadly neutralizing antibodies from a clade A–infected donor in Africa, which exhibit great potency and are able to neutralize a wide range of viruses from many different clades.
Abstract: Broadly neutralizing antibodies (bNAbs), which develop over time in some HIV-1-infected individuals, define critical epitopes for HIV vaccine design. Using a systematic approach, we have examined neutralization breadth in the sera of about 1800 HIV-1-infected individuals, primarily infected with non-clade B viruses, and have selected donors for monoclonal antibody (mAb) generation. We then used a high-throughput neutralization screen of antibody-containing culture supernatants from about 30,000 activated memory B cells from a clade A-infected African donor to isolate two potent mAbs that target a broadly neutralizing epitope. This epitope is preferentially expressed on trimeric Envelope protein and spans conserved regions of variable loops of the gp120 subunit. The results provide a framework for the design of new vaccine candidates for the elicitation of bNAb responses.
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TL;DR: Three broadly neutralizing antibodies are identified, isolated from an HIV-1–infected individual, that exhibited great breadth and potency of neutralization and were specific for the co-receptor CD4-binding site of the glycoprotein 120 (gp120), part of the viral Env spike.
Abstract: Cross-reactive neutralizing antibodies (NAbs) are found in the sera of many HIV-1-infected individuals, but the virologic basis of their neutralization remains poorly understood. We used knowledge of HIV-1 envelope structure to develop antigenically resurfaced glycoproteins specific for the structurally conserved site of initial CD4 receptor binding. These probes were used to identify sera with NAbs to the CD4-binding site (CD4bs) and to isolate individual B cells from such an HIV-1-infected donor. By expressing immunoglobulin genes from individual cells, we identified three monoclonal antibodies, including a pair of somatic variants that neutralized over 90% of circulating HIV-1 isolates. Exceptionally broad HIV-1 neutralization can be achieved with individual antibodies targeted to the functionally conserved CD4bs of glycoprotein 120, an important insight for future HIV-1 vaccine design.
1,713 citations
Duke University1, Fred Hutchinson Cancer Research Center2, New York University3, Harvard University4, Mahidol University5, University of Maryland, Baltimore6, Public Health Research Institute7, Walter Reed Army Institute of Research8, National Institutes of Health9, University of California, Santa Cruz10, Thailand Ministry of Public Health11
TL;DR: V vaccines that are designed to induce higher levels of V1V2 antibodies and lower levels of Env-specific IgA antibodies than are induced by the RV144 vaccine may have improved efficacy against HIV-1 infection.
Abstract: Background In the RV144 trial, the estimated efficacy of a vaccine regimen against human immunodeficiency virus type 1 (HIV-1) was 31.2%. We performed a case–control analysis to identify antibody and cellular immune correlates of infection risk. Methods In pilot studies conducted with RV144 blood samples, 17 antibody or cellular assays met prespecified criteria, of which 6 were chosen for primary analysis to determine the roles of T-cell, IgG antibody, and IgA antibody responses in the modulation of infection risk. Assays were performed on samples from 41 vaccinees who became infected and 205 uninfected vaccinees, obtained 2 weeks after final immunization, to evaluate whether immune-response variables predicted HIV-1 infection through 42 months of follow-up. Results Of six primary variables, two correlated significantly with infection risk: the binding of IgG antibodies to variable regions 1 and 2 (V1V2) of HIV-1 envelope proteins (Env) correlated inversely with the rate of HIV-1 infection (estimated odds...
1,666 citations
TL;DR: 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.
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.
1,473 citations
TL;DR: A role for potent neutralizing antibodies (nAbs) in prophylaxis, and potentially therapy, of COVID-19 is suggested, as indicated by maintained weight and low lung viral titers in treated animals, and the passive transfer of a nAb provides protection against disease in high-dose SARS-CoV-2 challenge in Syrian hamsters.
Abstract: Countermeasures to prevent and treat coronavirus disease 2019 (COVID-19) are a global health priority. We enrolled a cohort of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-recovered participants, developed neutralization assays to investigate antibody responses, adapted our high-throughput antibody generation pipeline to rapidly screen more than 1800 antibodies, and established an animal model to test protection. We isolated potent neutralizing antibodies (nAbs) to two epitopes on the receptor binding domain (RBD) and to distinct non-RBD epitopes on the spike (S) protein. As indicated by maintained weight and low lung viral titers in treated animals, the passive transfer of a nAb provides protection against disease in high-dose SARS-CoV-2 challenge in Syrian hamsters. The study suggests a role for nAbs in prophylaxis, and potentially therapy, of COVID-19. The nAbs also define protective epitopes to guide vaccine design.
1,224 citations
Rockefeller University1, California Institute of Technology2, Free University of Berlin3, Memorial Sloan Kettering Cancer Center4, International AIDS Vaccine Initiative5, Scripps Research Institute6, Ragon Institute of MGH, MIT and Harvard7, Harvard University8, Howard Hughes Medical Institute9, Beth Israel Deaconess Medical Center10
TL;DR: Anti-HIV broadly neutralizing antibodies with similar specificities and modes of binding were found in multiple HIV-infected individuals, and cloned 576 new HIV antibodies from four unrelated individuals to determine whether they are part of a larger group of related molecules.
Abstract: Passive transfer of broadly neutralizing HIV antibodies can prevent infection, which suggests that vaccines that elicit such antibodies would be protective. Thus far, however, few broadly neutralizing HIV antibodies that occur naturally have been characterized. To determine whether these antibodies are part of a larger group of related molecules, we cloned 576 new HIV antibodies from four unrelated individuals. All four individuals produced expanded clones of potent broadly neutralizing CD4-binding-site antibodies that mimic binding to CD4. Despite extensive hypermutation, the new antibodies shared a consensus sequence of 68 immunoglobulin H (IgH) chain amino acids and arise independently from two related IgH genes. Comparison of the crystal structure of one of the antibodies to the broadly neutralizing antibody VRC01 revealed conservation of the contacts to the HIV spike.
1,110 citations
References
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TL;DR: It is demonstrated that antibodies can affect transmission and subsequent disease course after vaginal SHIV-challenge, and the data begin to define the type of antibody response that could play a role in protection against mucosal transmission of HIV-1.
Abstract: The development of the human immunodeficiency virus-1 (HIV-1)/simian immunodeficiency virus (SIV) chimeric virus macaque model (SHIV) permits the in vivo evaluation of anti-HIV-1 envelope glycoprotein immune responses. Using this model, others, and we have shown that passively infused antibody can protect against an intravenous challenge. However, HIV-1 is most often transmitted across mucosal surfaces and the intravenous challenge model may not accurately predict the role of antibody in protection against mucosal exposure. After controlling the macaque estrous cycle with progesterone, anti-HIV-1 neutralizing monoclonal antibodies 2F5 and 2G12, and HIV immune globulin were tested. Whereas all five control monkeys displayed high plasma viremia and rapid CD4 cell decline, 14 antibody-treated macaques were either completely protected against infection or against pathogenic manifestations of SHIV-infection. Infusion of all three antibodies together provided the greatest amount of protection, but a single monoclonal antibody, with modest virus neutralizing activity, was also protective. Compared with our previous intravenous challenge study with the same virus and antibodies, the data indicated that greater protection was achieved after vaginal challenge. This study demonstrates that antibodies can affect transmission and subsequent disease course after vaginal SHIV-challenge; the data begin to define the type of antibody response that could play a role in protection against mucosal transmission of HIV-1.
1,327 citations
TL;DR: A general correlation between in vitro neutralization and protection is indicated and it is suggested that a vaccine that elicits neutralizing antibody should have a protective effect against HIV-1 infection or disease.
Abstract: The role of antibody in protection against human immunodeficiency virus (HIV-1) has been difficult to study in animal models because most primary HIV-1 strains do not infect nonhuman primates. Using a chimeric simian/human immunodeficiency virus (SHIV) based on the envelope of a primary isolate (HIV-89.6), we performed passive-transfer experiments in rhesus macaques to study the role of anti-envelope antibodies in protection. Based on prior in vitro data showing neutralization synergy by antibody combinations, we evaluated HIV immune globulin (HIVIG), and human monoclonal antibodies (MAbs) 2F5 and 2G12 given alone, compared with the double combination 2F5/2G12 and the triple combination HIVIG/2F5/2G12. Antibodies were administered 24 h prior to intravenous challenge with the pathogenic SHIV-89.6PD. Six control monkeys displayed high plasma viremia, rapid CD4(+)-cell decline, and clinical AIDS within 14 weeks. Of six animals given HIVIG/2F5/2G12, three were completely protected; the remaining three animals became SHIV infected but displayed reduced plasma viremia and near normal CD4(+)-cell counts. One of three monkeys given 2F5/2G12 exhibited only transient evidence of infection; the other two had marked reductions in viral load. All monkeys that received HIVIG, 2F5, or 2G12 alone became infected and developed high-level plasma viremia. However, compared to controls, monkeys that received HIVIG or MAb 2G12 displayed a less profound drop in CD4(+) T cells and a more benign clinical course. These data indicate a general correlation between in vitro neutralization and protection and suggest that a vaccine that elicits neutralizing antibody should have a protective effect against HIV-1 infection or disease.
837 citations
TL;DR: Consideration of all the data, together with inspection of a molecular model of gp120, suggests that the most likely epitope for 2G12 is formed from mannose residues contributed by the glycans attached to N295 and N332, with the other glycans playing an indirect role in maintaining epitope conformation.
Abstract: The humoral immune response to infection by human immunodeficiency virus type 1 (HIV-1) is typically characterized by relatively low levels of neutralizing antibodies, particularly those with broad activity against many different isolates of the virus (6, 23, 35, 36, 46). As might perhaps be anticipated from this observation, the induction of such antibodies by vaccination has proven largely elusive (9). At the same time, interest in inducing broadly neutralizing antibodies has increased as it becomes clear that antibodies can provide considerable benefit against HIV or simian immunodeficiency virus (SIV) challenge in animal models (1, 17, 30-32, 44, 55). Fortunately, natural infection is not completely barren of lessons for vaccine design since, although HIV elicits weak cross-neutralizing responses, a small number of human monoclonal antibodies (MAbs) with broad activities have been isolated from infected individuals (7, 8, 12, 59, 60). One rational contribution to eliciting neutralizing antibodies by vaccination is then to explore the interaction of these antibodies with virus envelope at the molecular level and incorporate the information obtained into immunogen design. Here, we seek to understand the interaction of one broadly neutralizing antibody with HIV-1 envelope.
For some time, only three broadly neutralizing MAbs to HIV-1 were known (5, 12). Two of these MAbs bind to the surface glycoprotein, gp120, which is the viral receptor for CD4 and chemokine receptors CCR5 and CXCR4. These MAbs are b12, which recognizes an epitope overlapping the CD4 receptor site (7, 51), and 2G12, which recognizes an epitope based around the C4/V4 region of gp120 and is highly sensitive to the presence of N-linked glycans in this region (24, 60). One MAb, 2F5, binds to an epitope involving a linear motif (ELDKWA) on the membrane proximal region of the transmembrane envelope protein gp41 (8, 24, 43, 71). Recently, two MAbs, Z13 and 4E10, have been described which recognize a region close to the C terminus of the 2F5 epitope (56, 71). Another Fab with broad neutralizing ability, X5, recognizes a region close to the coreceptor binding site on gp120 and overlapping the epitope recognized by CD4-induced MAbs, such as 17b (37a).
We focus here on the MAb 2G12. In vitro, this MAb has been shown to neutralize a wide spectrum of different HIV-1 isolates (59, 60), including those from different clades, with the notable exception of clade E. In vivo, the MAb protects macaques against vaginal challenge with the chimeric virus SHIV 89.6P (32). The antibody recognizes a unique epitope in that it does not compete with any of the large panel of MAbs to gp120 that have been produced (37). The binding of 2G12 to gp120 is inhibited by a number of mutations that disrupt sequences encoding attachment of N-linked carbohydrate chains (60). These sequences are located in the C2 and C3 regions around the base of the V3 loop, the C4 region, and the V4 loop. The crystal structure of the core of gp120 suggests that the carbohydrate attachment sites are clustered together on a part of the gp120 molecule known as the “silent face” (27, 28, 66, 67). This extensive solvent-accessible face is largely covered by carbohydrate and expected to be relatively weakly immunogenic and, hence, is described as immunologically silent.
Carbohydrate-rich regions of glycoproteins are generally poorly immunogenic for a number of reasons. First, carbohydrates exhibit microheterogeneity; therefore, a single protein sequence would be expected to display multiple glycoforms, leading to the dilution of any single antigenic response (52). Second, large, potentially dynamic glycans (62, 64) can cover potential protein epitopes. Third, in the case of viruses, which depend on the host glycosylation machinery since they have none of their own, the oligosaccharides attached to potential antigens are the same as those attached to host glycoproteins. Therefore, in general, the host will display tolerance towards these sugars. The difficulty in eliciting antibodies to a carbohydrate face is consistent with the apparently unique nature of MAb 2G12.
Despite the probable placement of the 2G12 epitope on the silent face (or at the junction of silent and neutralizing faces) (26, 27, 49, 60), we understand relatively little about the molecular nature of the epitope. We do not know whether the epitope is exclusively carbohydrate, exclusively protein with a requirement for carbohydrate to maintain local protein structure, or some combination of these. We do not know the relative importance of the different carbohydrate chains that are potentially involved or which sugar residues are likely to be crucial.
To address these issues we have carried out a number of studies on the 2G12-gp120 interaction. These include a detailed glycan analysis of the gp120 N-linked carbohydrates, an examination of the effects of digestion of gp120 by various glycosidases, an analysis of the ability of various glycans and lectins to inhibit the interaction, extensive alanine scanning mutagenesis of gp120, sequence comparisons of gp120s with different abilities to interact with 2G12 and, finally, modeling studies of gp120. We conclude that Manα1→2Man-linked residues of the outer face of gp120 are required for the 2G12 epitope. Extensive site-directed mutagenesis demonstrated little dependence of 2G12 affinity on specific gp120 amino acid side chains.
696 citations
TL;DR: It is shown that passive intravenous transfer of the human neutralizing monoclonal antibody b12 provides dose-dependent protection to macaques vaginally challenged with the R5 virus SHIV162P4, suggesting that a vaccine based on antibody alone would need to sustain serum neutralizing antibody titers of the order of 1:400 to achieve sterile protection but that lower titers, around 1:100, could provide a significant benefit.
Abstract: A major unknown in human immunodeficiency virus (HIV-1) vaccine design is the efficacy of antibodies in preventing mucosal transmission of R5 viruses. These viruses, which use CCR5 as a coreceptor, appear to have a selective advantage in transmission of HIV-1 in humans. Hence R5 viruses predominate during primary infection and persist throughout the course of disease in most infected people. Vaginal challenge of macaques with chimeric simian/human immunodeficiency viruses (SHIV) is perhaps one of the best available animal models for human HIV-1 infection. Passive transfer studies are widely used to establish the conditions for antibody protection against viral challenge. Here we show that passive intravenous transfer of the human neutralizing monoclonal antibody b12 provides dose-dependent protection to macaques vaginally challenged with the R5 virus SHIV(162P4). Four of four monkeys given 25 mg of b12 per kg of body weight 6 h prior to challenge showed no evidence of viral infection (sterile protection). Two of four monkeys given 5 mg of b12/kg were similarly protected, whereas the other two showed significantly reduced and delayed plasma viremia compared to control animals. In contrast, all four monkeys treated with a dose of 1 mg/kg became infected with viremia levels close to those for control animals. Antibody b12 serum concentrations at the time of virus challenge corresponded to approximately 400 (25 mg/kg), 80 (5 mg/kg), and 16 (1 mg/kg) times the in vitro (90%) neutralization titers. Therefore, complete protection against mucosal challenge with an R5 SHIV required essentially complete neutralization of the infecting virus. This suggests that a vaccine based on antibody alone would need to sustain serum neutralizing antibody titers (90%) of the order of 1:400 to achieve sterile protection but that lower titers, around 1:100, could provide a significant benefit. The significance of such substerilizing neutralizing antibody titers in the context of a potent cellular immune response is an important area for further study.
696 citations
TL;DR: These elite neutralizers provide promising starting material for the isolation of broadly neutralizing monoclonal antibodies to assist in HIV-1 vaccine design.
Abstract: The development of a rapid and efficient system to identify human immunodeficiency virus type 1 (HIV-1)-infected individuals with broad and potent HIV-1-specific neutralizing antibody responses is an important step toward the discovery of critical neutralization targets for rational AIDS vaccine design. In this study, samples from HIV-1-infected volunteers from diverse epidemiological regions were screened for neutralization responses using pseudovirus panels composed of clades A, B, C, and D and circulating recombinant forms (CRFs). Initially, 463 serum and plasma samples from Australia, Rwanda, Uganda, the United Kingdom, and Zambia were screened to explore neutralization patterns and selection ranking algorithms. Samples were identified that neutralized representative isolates from at least four clade/CRF groups with titers above prespecified thresholds and ranked based on a weighted average of their log-transformed neutralization titers. Linear regression methods selected a five-pseudovirus subset, representing clades A, B, and C and one CRF01_AE, that could identify top-ranking samples with 50% inhibitory concentration (IC(50)) neutralization titers of >or=100 to multiple isolates within at least four clade groups. This reduced panel was then used to screen 1,234 new samples from the Ivory Coast, Kenya, South Africa, Thailand, and the United States, and 1% were identified as elite neutralizers. Elite activity is defined as the ability to neutralize, on average, more than one pseudovirus at an IC(50) titer of 300 within a clade group and across at least four clade groups. These elite neutralizers provide promising starting material for the isolation of broadly neutralizing monoclonal antibodies to assist in HIV-1 vaccine design.
584 citations