Antibodies capable of neutralizing HIV-1 often target variable regions 1 and 2 (V1V2) of the HIV-1 envelope, but the mechanism of their elicitation has been unclear. Here we define the developmental ...pathway by which such antibodies are generated and acquire the requisite molecular characteristics for neutralization. Twelve somatically related neutralizing antibodies (CAP256-VRC26.01-12) were isolated from donor CAP256 (from the Centre for the AIDS Programme of Research in South Africa (CAPRISA)); each antibody contained the protruding tyrosine-sulphated, anionic antigen-binding loop (complementarity-determining region (CDR) H3) characteristic of this category of antibodies. Their unmutated ancestor emerged between weeks 30-38 post-infection with a 35-residue CDR H3, and neutralized the virus that superinfected this individual 15 weeks after initial infection. Improved neutralization breadth and potency occurred by week 59 with modest affinity maturation, and was preceded by extensive diversification of the virus population. HIV-1 V1V2-directed neutralizing antibodies can thus develop relatively rapidly through initial selection of B cells with a long CDR H3, and limited subsequent somatic hypermutation. These data provide important insights relevant to HIV-1 vaccine development.
Neutralizing antibodies are likely to play a crucial part in a preventative HIV-1 vaccine. Although efforts to elicit broadly cross-neutralizing (BCN) antibodies by vaccination have been ...unsuccessful, a minority of individuals naturally develop these antibodies after many years of infection. How such antibodies arise, and the role of viral evolution in shaping these responses, is unknown. Here we show, in two HIV-1-infected individuals who developed BCN antibodies targeting the glycan at Asn332 on the gp120 envelope, that this glycan was absent on the initial infecting virus. However, this BCN epitope evolved within 6 months, through immune escape from earlier strain-specific antibodies that resulted in a shift of a glycan to position 332. Both viruses that lacked the glycan at amino acid 332 were resistant to the Asn332-dependent BCN monoclonal antibody PGT128 (ref. 8), whereas escaped variants that acquired this glycan were sensitive. Analysis of large sequence and neutralization data sets showed the 332 glycan to be significantly under-represented in transmitted subtype C viruses compared to chronic viruses, with the absence of this glycan corresponding with resistance to PGT128. These findings highlight the dynamic interplay between early antibodies and viral escape in driving the evolution of conserved BCN antibody epitopes.
Antibodies that bind residue K169 in the V2 region of the HIV-1 envelope correlated with reduced risk of infection in the RV144 vaccine trial but were restricted to two ED-motif-encoding light chain ...genes. Here, we identify an HIV-infected donor with high-titer V2 peptide-binding antibodies and isolate two antibody lineages (CAP228-16H/19F and CAP228-3D) that mediate potent antibody-dependent cell-mediated cytotoxicity (ADCC). Both lineages use the IGHV5-51 heavy chain germline gene, similar to the RV144 antibody CH58, but one lineage (CAP228-16H/19F) uses a light chain without the ED motif. A cocrystal structure of CAP228-16H bound to a V2 peptide identified a IGLV3-21 gene-encoded DDxD motif that is used to bind K169, with a mechanism that allows CAP228-16H to recognize more globally relevant V2 immunotypes. Overall, these data further our understanding of the development of cross-reactive, V2-binding, antiviral antibodies and effectively expand the human light chain repertoire able to respond to RV144-like immunogens.
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•V2-specific antibodies from HIV infection that resemble vaccine-elicited antibodies•Use of a different antibody light chain with a different V2 K169-binding motif•Show broad ADCC activity against globally relevant V2 immunotypes•Increases the repertoire of B cells able to respond to RV144 V2 immunogens
V2-directed antibodies from the RV144 vaccine trial correlated with reduced HIV-1 infection risk but exhibited restricted light chain gene usage. Here, van Eeden et al. isolate similar antibodies from an HIV-1-infected individual and identify a third V2-reactive light chain gene, increasing the antibody repertoire potentially elicited by vaccination.
We report here on HIV-1 immunization results in rabbits and macaques co-immunized with clade C gp160 DNA and gp140 trimeric envelope vaccines, a strategy similar to a recent clinical trial that ...showed improved speed and magnitude of humoral responses. Clade C envelopes were isolated from CAP257, an individual who developed a unique temporal pattern of neutralization breadth development, comprising three separate "Waves" targeting distinct Env epitopes and different HIV clades. We used phylogeny and neutralization criteria to down-select envelope vaccine candidates, and confirmed antigenicity of our antigens by interaction with well-characterized broadly neutralizing monoclonal antibodies. Using these envelopes, we performed rabbit studies that screened for immunogenicity of CAP257 Envs from timepoints preceding peak neutralization breadth in each Wave. Selected CAP257 envelopes from Waves 1 and 2, during the first 2 years of infection that were highly immunogenic in rabbits were then tested in macaques. We found that in rabbits and macaques, co-immunization of DNA, and protein envelope-based vaccines induced maximum binding and neutralizing antibody titers with three immunizations. No further benefit was obtained with additional immunizations. The vaccine strategies recapitulated the Wave-specific epitope targeting observed in the CAP257 participant, and elicited Tier 1A, 1B, and Tier 2 heterologous neutralization. CAP257 envelope immunogens also induced the development of ADCC and T
responses in macaques, and these responses positively correlated with heterologous neutralization. Together, the results from two animal models in this study have implications for identifying effective vaccine immunogens. We used a multi-step strategy to (1) select an Env donor with well-characterized neutralization breadth development; (2) study Env phylogeny for potential immunogens circulating near peak breadth timepoints during the first 2 years of infection; (3) test down-selected Envs for antigenicity; (4) screen down-selected Envs in an effective vaccine regimen in rabbits; and (5) advance the most immunogenic Envs to NHP studies. The results were an induction of high titers of HIV-1 envelope-specific antibodies with increasing avidity and cross-clade neutralizing antibodies with effector functions that together may improve the potential for protection in a pre-clinical SHIV model.
Abstract
Background
HIV-1 infects a wide range of CD4
+
T cells with different phenotypic properties and differing expression levels of entry coreceptors. We sought to determine the viral tropism of ...subtype C (C-HIV) Envelope (Env) clones for different CD4
+
T cell subsets and whether tropism changes during acute to chronic disease progression. HIV-1
envs
were amplified from the plasma of five C-HIV infected women from three untreated time points; less than 2 months, 1-year and 3-years post-infection. Pseudoviruses were generated from Env clones, phenotyped for coreceptor usage and CD4
+
T cell subset tropism was measured by flow cytometry.
Results
A total of 50 C-HIV
envs
were cloned and screened for functionality in pseudovirus infection assays. Phylogenetic and variable region characteristic analysis demonstrated evolution in
envs
between time points. We found 45 pseudoviruses were functional and all used CCR5 to mediate entry into NP2/CD4/CCR5 cells. In vitro infection assays showed transitional memory (TM) and effector memory (EM) CD4
+
T cells were more frequently infected (median: 46% and 25% of total infected CD4
+
T cells respectively) than naïve, stem cell memory, central memory and terminally differentiated cells. This was not due to these subsets contributing a higher proportion of the CD4
+
T cell pool, rather these subsets were more susceptible to infection (median: 5.38% EM and 2.15% TM cells infected), consistent with heightened CCR5 expression on EM and TM cells. No inter- or intra-participant changes in CD4
+
T cell subset tropism were observed across the three-time points.
Conclusions
CD4
+
T cell subsets that express more CCR5 were more susceptible to infection with C-HIV Envs, suggesting that these may be the major cellular targets during the first 3 years of infection. Moreover, we found that viral tropism for different CD4
+
T cell subsets in vitro did not change between Envs cloned from acute to chronic disease stages. Finally, central memory, naïve and stem cell memory CD4
+
T cell subsets were susceptible to infection, albeit inefficiently by Envs from all time-points, suggesting that direct infection of these cells may help establish the latent reservoir early in infection.
The VH1-2 restricted VRC01-class of antibodies targeting the HIV envelope CD4 binding site are a major focus of HIV vaccine strategies. However, a detailed analysis of VRC01-class antibody ...development has been limited by the rare nature of these responses during natural infection and the lack of longitudinal sampling of such responses. To inform vaccine strategies, we mapped the development of a VRC01-class antibody lineage (PCIN63) in the subtype C infected IAVI Protocol C neutralizer PC063. PCIN63 monoclonal antibodies had the hallmark VRC01-class features and demonstrated neutralization breadth similar to the prototype VRC01 antibody, but were 2- to 3-fold less mutated. Maturation occurred rapidly within ∼24 months of emergence of the lineage and somatic hypermutations accumulated at key contact residues. This longitudinal study of broadly neutralizing VRC01-class antibody lineage reveals early binding to the N276-glycan during affinity maturation, which may have implications for vaccine design.
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•Isolation of PCIN63, a VRC01-class CD4-binding site Ab lineage with only 12% SHM•PCIN63 lineage emerged at 40 months post infection and achieved breadth in 2 years•Identification of a putative PCIN63 UCA reveals the importance of the CDRL3•PCIN63 bnAbs segregate in N276 glycan- dependent and -independent sub-families
Understanding the molecular basis of HIV Env-specific broadly neutralizing antibodies (bnAbs) development especially, at early stages, is key for germline-targeting vaccine design strategies. Umotoy et al. mapped the development of a VRC01-class bnAb lineage that achieved breadth in 2 years, revealing early binding to the N276-glycan during affinity maturation, which may have implications for vaccine design.
Eliciting antibodies that neutralize a broad range of circulating HIV strains (broadly neutralizing antibodies bnAbs) represents a key priority for vaccine development. HIV superinfection ...(re-infection with a second strain following an established infection) has been associated with neutralization breadth, and can provide insights into how the immune system responds to sequential exposure to distinct HIV envelope glycoproteins (Env). Characterizing the neutralizing antibody (nAb) responses in four superinfected women revealed that superinfection does not boost memory nAb responses primed by the first infection or promote nAb responses to epitopes conserved in both infecting viruses. While one superinfected individual developed potent bnAbs, superinfection was likely not the driver as the nAb response did not target an epitope conserved in both viruses. Rather, sequential exposure led to nAbs specific to each Env but did not promote bnAb development. Thus, sequential immunization with heterologous Envs may not be sufficient to focus the immune response onto conserved epitopes.
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•HIV superinfection does not efficiently recruit cross-reactive memory B cells•Superinfection results in antibody responses specific to each infecting strain•No evidence that superinfection drives the development of bnAbs
HIV-infected individuals can be re-infected with a second strain (superinfection), providing a model that informs the use of sequential immunizations in future vaccines. Sheward et al. find that superinfection fails to boost memory B cells primed by the first infection and does not promote broadly neutralizing antibodies to HIV.
Neutralizing antibodies (nAbs) to highly variable viral pathogens show remarkable diversification during infection, resulting in an “arms race” between virus and host. Studies of nAb lineages have ...shown how somatic hypermutation (SHM) in immunoglobulin (Ig)-variable regions enables maturing antibodies to neutralize emerging viral escape variants. However, the Ig-constant region (which determines isotype) can also influence epitope recognition. Here, we use longitudinal deep sequencing of an HIV-directed nAb lineage, CAP88-CH06, and identify several co-circulating isotypes (IgG3, IgG1, IgA1, IgG2, and IgA2), some of which share identical variable regions. First, we show that IgG3 and IgA1 isotypes are better able to neutralize longitudinal autologous viruses and epitope mutants than can IgG1. Second, detrimental class-switch recombination (CSR) events that resulted in reduced neutralization can be rescued by further CSR, which we term “switch redemption.” Thus, CSR represents an additional immunological mechanism to counter viral escape from HIV-specific antibody responses.
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•Multiple co-circulating isotypes within an HIV neutralizing antibody lineage•Differential neutralization of emerging viral escape variants is mediated by isotype•Detrimental isotype switching can be rescued by further class-switch recombination•Class-switch recombination contributes to antibody-virus co-evolution
Scheepers et al. show within an HIV-specific antibody lineage that isotypes confer variable ability to neutralize emerging viral escape variants. This suggests that class switching, in addition to somatic hypermutation of immunoglobulin-variable regions, contributes to antibody maturation during infection.
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