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Summary The third variable (V3) loop and the CD4 binding site (CD4bs) of the HIV-1 envelope are frequently targeted by neutralizing antibodies (nAbs) in infected individuals. In chronic infection, HIV-1 escape mutants repopulate the plasma, and V3 and CD4bs nAbs emerge that can neutralize heterologous tier 1 easy-to-neutralize but not tier 2 difficult-to-neutralize HIV-1 isolates. However, neutralization sensitivity of autologous plasma viruses to this type of nAb response has not been studied. We describe the development and evolution in vivo of antibodies distinguished by their target specificity for V3 and CD4bs epitopes on autologous tier 2 viruses but not on heterologous tier 2 viruses. A surprisingly high fraction of autologous circulating viruses was sensitive to these antibodies. These findings demonstrate a role for V3 and CD4bs antibodies in constraining the native envelope trimer in vivo to a neutralization-resistant phenotype, explaining why HIV-1 transmission generally occurs by tier 2 neutralization-resistant viruses. [ABSTRACT FROM AUTHOR]

Summary Induction of HIV-1 broad neutralizing antibodies (bnAbs) is a goal of HIV-1 vaccine development but has remained challenging partially due to unusual traits of bnAbs, including high somatic hypermutation (SHM) frequencies and in-frame insertions and deletions (indels). Here we examined the propensity and functional requirement for indels within HIV-1 bnAbs. High-throughput sequencing of the immunoglobulin (Ig) V H DJ H genes in HIV-1 infected and uninfected individuals revealed that the indel frequency was elevated among HIV-1-infected subjects, with no unique properties attributable to bnAb-producing individuals. This increased indel occurrence depended only on the frequency of SHM point mutations. Indel-encoded regions were generally proximal to antigen binding sites. Additionally, reconstruction of a HIV-1 CD4-binding site bnAb clonal lineage revealed that a large compound V H DJ H indel was required for bnAb activity. Thus, vaccine development should focus on designing regimens targeted at sustained activation of bnAb lineages to achieve the required SHM and indel events. [ABSTRACT FROM AUTHOR]

Summary Monoclonal antibodies derived from blood plasma cells of acute HIV-1-infected individuals are predominantly targeted to the HIV Env gp41 and cross-reactive with commensal bacteria. To understand this phenomenon, we examined anti-HIV responses in ileum B cells using recombinant antibody technology and probed their relationship to commensal bacteria. The dominant ileum B cell response was to Env gp41. Remarkably, a majority (82%) of the ileum anti-gp41 antibodies cross-reacted with commensal bacteria, and of those, 43% showed non-HIV-1 antigen polyreactivity. Pyrosequencing revealed shared HIV-1 antibody clonal lineages between ileum and blood. Mutated immunoglobulin G antibodies cross-reactive with both Env gp41 and microbiota could also be isolated from the ileum of HIV-1 uninfected individuals. Thus, the gp41 commensal bacterial antigen cross-reactive antibodies originate in the intestine, and the gp41 Env response in HIV-1 infection can be derived from a preinfection memory B cell pool triggered by commensal bacteria that cross-react with Env. [ABSTRACT FROM AUTHOR]

A critical roadblock to HIV vaccine development is the inability to induce B cell lineages of broadly neutralizing antibodies (bnAbs) in humans. In people living with HIV-1, bnAbs take years to develop. The HVTN 133 clinical trial studied a peptide/liposome immunogen targeting B cell lineages of HIV-1 envelope (Env) membrane-proximal external region (MPER) bnAbs (NCT03934541). Here, we report MPER peptide-liposome induction of polyclonal HIV-1 B cell lineages of mature bnAbs and their precursors, the most potent of which neutralized 15% of global tier 2 HIV-1 strains and 35% of clade B strains with lineage initiation after the second immunization. Neutralization was enhanced by vaccine selection of improbable mutations that increased antibody binding to gp41 and lipids. This study demonstrates proof of concept for rapid vaccine induction of human B cell lineages with heterologous neutralizing activity and selection of antibody improbable mutations and outlines a path for successful HIV-1 vaccine development. [Display omitted] • HIV gp41 MPER peptide-liposome vaccine elicited polyclonal NAbs in humans • Vaccine-induced MPER-reactive antibodies matured from precursors to bnAb status • Vaccine-selected improbable mutations conferred lipid binding and HIV neutralization • MPER bnAb lineage was initiated after two immunizations The HVTN 133 human clinical trial demonstrated the first success of vaccine induction of polyclonal heterologous HIV-1-neutralizing antibodies that target gp41 MPER. Williams and colleagues show that proximal-MPER bnAbs can be induced by gp41 MPER peptide-liposomes in humans to neutralize HIV-1. [ABSTRACT FROM AUTHOR]

Summary In HIV-1, the ability to mount antibody responses to conserved, neutralizing epitopes is critical for protection. Here we have studied the light chain usage of human and rhesus macaque antibodies targeted to a dominant region of the HIV-1 envelope second variable (V2) region involving lysine (K) 169, the site of immune pressure in the RV144 vaccine efficacy trial. We found that humans and rhesus macaques used orthologous lambda variable gene segments encoding a glutamic acid-aspartic acid (ED) motif for K169 recognition. Structure determination of an unmutated ancestor antibody demonstrated that the V2 binding site was preconfigured for ED motif-mediated recognition prior to maturation. Thus, light chain usage for recognition of the site of immune pressure in the RV144 trial is highly conserved across species. These data indicate that the HIV-1 K169-recognizing ED motif has persisted over the diversification between rhesus macaques and humans, suggesting an evolutionary advantage of this antibody recognition mode. [ABSTRACT FROM AUTHOR]

Summary: The RV144 HIV-1 trial of the canary pox vector (ALVAC-HIV) plus the gp120 AIDSVAX B/E vaccine demonstrated an estimated efficacy of 31%, which correlated directly with antibodies to HIV-1 envelope variable regions 1 and 2 (V1-V2). Genetic analysis of trial viruses revealed increased vaccine efficacy against viruses matching the vaccine strain at V2 residue 169. Here, we isolated four V2 monoclonal antibodies from RV144 vaccinees that recognize residue 169, neutralize laboratory-adapted HIV-1, and mediate killing of field-isolate HIV-1-infected CD4+ T cells. Crystal structures of two of the V2 antibodies demonstrated that residue 169 can exist within divergent helical and loop conformations, which contrasted dramatically with the β strand conformation previously observed with a broadly neutralizing antibody PG9. Thus, RV144 vaccine-induced immune pressure appears to target a region that may be both sequence variable and structurally polymorphic. Variation may signal sites of HIV-1 envelope vulnerability, providing vaccine designers with new options. [ABSTRACT FROM AUTHOR]

SARS-CoV-2-neutralizing antibodies (NAbs) protect against COVID-19. A concern regarding SARS-CoV-2 antibodies is whether they mediate disease enhancement. Here, we isolated NAbs against the receptor-binding domain (RBD) or the N-terminal domain (NTD) of SARS-CoV-2 spike from individuals with acute or convalescent SARS-CoV-2 or a history of SARS-CoV infection. Cryo-electron microscopy of RBD and NTD antibodies demonstrated function-specific modes of binding. Select RBD NAbs also demonstrated Fc receptor-γ (FcγR)-mediated enhancement of virus infection in vitro , while five non-neutralizing NTD antibodies mediated FcγR-independent in vitro infection enhancement. However, both types of infection-enhancing antibodies protected from SARS-CoV-2 replication in monkeys and mice. Three of 46 monkeys infused with enhancing antibodies had higher lung inflammation scores compared to controls. One monkey had alveolar edema and elevated bronchoalveolar lavage inflammatory cytokines. Thus, while in vitro antibody-enhanced infection does not necessarily herald enhanced infection in vivo , increased lung inflammation can rarely occur in SARS-CoV-2 antibody-infused macaques. [Display omitted] • RBD or NTD antibodies exhibited infection enhancement in vitro but not in vivo • Neutralizing or infection-enhancing NTD antibodies bound distinct epitopes • In vitro infection-enhancing antibodies protected from SARS-CoV-2 in vivo • Cross-reactive RBD-neutralizing antibodies were protective—most potent DH1047 Convalescent human-derived SARS-CoV-2 RBD and NTD antibodies mediated neutralization as well as infection enhancement in vitro , yet infusion of these antibodies in mice or cynomolgus macaques resulted in suppression of virus replication. [ABSTRACT FROM AUTHOR]

SARS-CoV-2 infection has emerged as a serious global pandemic. Because of the high transmissibility of the virus and the high rate of morbidity and mortality associated with COVID-19, developing effective and safe vaccines is a top research priority. Here, we provide a detailed evaluation of the immunogenicity of lipid nanoparticle-encapsulated, nucleoside-modified mRNA (mRNA-LNP) vaccines encoding the full-length SARS-CoV-2 spike protein or the spike receptor binding domain in mice. We demonstrate that a single dose of these vaccines induces strong type 1 CD4+ and CD8+ T cell responses, as well as long-lived plasma and memory B cell responses. Additionally, we detect robust and sustained neutralizing antibody responses and the antibodies elicited by nucleoside-modified mRNA vaccines do not show antibody-dependent enhancement of infection in vitro. Our findings suggest that the nucleoside-modified mRNA-LNP vaccine platform can induce robust immune responses and is a promising candidate to combat COVID-19. • mRNA vaccines induce robust type 1 CD4+ and CD8+ T cells in the spleen and lung • Vaccine-induced T cells readily exit the vasculature and enter the lung parenchyma • mRNA vaccines elicit strong long-lived plasma cell and memory B cell responses • mRNA vaccines induce antibodies with potent anti-SARS-CoV-2 neutralization activity SARS-CoV-2 mRNA-based vaccines are among the most promising vaccine candidates against COVID-19. Laczkó et al. evaluate two nucleoside-modified mRNA vaccine candidates in mice and demonstrate that they induce potent T and B cell immune responses and high levels of neutralizing antibodies after administration of a single vaccine dose. [ABSTRACT FROM AUTHOR]

The emergence of three highly pathogenic human coronaviruses-severe acute respiratory syndrome coronavirus (SARS-CoV) in 2003, Middle Eastern respiratory syndrome (MERS)-CoV in 2012, and SARS-CoV-2 in 2019-underlines the need to develop broadly active vaccines against the Merbecovirus and Sarbecovirus betacoronavirus subgenera. While SARS-CoV-2 vaccines protect against severe COVID-19, they do not protect against other sarbecoviruses or merbecoviruses. Here, we vaccinate mice with a trivalent sortase-conjugate nanoparticle (scNP) vaccine containing the SARS-CoV-2, RsSHC014, and MERS-CoV receptor-binding domains (RBDs), which elicited live-virus neutralizing antibody responses. The trivalent RBD scNP elicited serum neutralizing antibodies against bat zoonotic Wuhan Institute of Virology-1 (WIV-1)-CoV, SARS-CoV, SARS-CoV-2 BA.1, SARS-CoV-2 XBB.1.5, and MERS-CoV live viruses. The monovalent SARS-CoV-2 RBD scNP vaccine only protected against Sarbecovirus challenge, whereas the trivalent RBD scNP vaccine protected against both Merbecovirus and Sarbecovirus challenge in highly pathogenic and lethal mouse models. This study demonstrates proof of concept for a single pan-sarbecovirus/pan-merbecovirus vaccine that protects against three highly pathogenic human coronaviruses spanning two betacoronavirus subgenera., Competing Interests: Declaration of interests B.F.H. and K.O.S. have filed US patents regarding the nanoparticle vaccine. R.S.B. is on the scientific advisory boards of VaxArt, Invivyd, and Takeda., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

The success of nucleoside-modified mRNAs in lipid nanoparticles (mRNA-LNP) as COVID-19 vaccines heralded a new era of vaccine development. For HIV-1, multivalent envelope (Env) trimer protein nanoparticles are superior immunogens compared with trimers alone for priming of broadly neutralizing antibody (bnAb) B cell lineages. The successful expression of complex multivalent nanoparticle immunogens with mRNAs has not been demonstrated. Here, we show that mRNAs can encode antigenic Env trimers on ferritin nanoparticles that initiate bnAb precursor B cell expansion and induce serum autologous tier 2 neutralizing activity in bnAb precursor V H  + V L knock-in mice. Next-generation sequencing demonstrates acquisition of critical mutations, and monoclonal antibodies that neutralize heterologous HIV-1 isolates are isolated. Thus, mRNA-LNP can encode complex immunogens and may be of use in design of germline-targeting and sequential boosting immunogens for HIV-1 vaccine development., Competing Interests: Declaration of interests B.F.H., K.O.S., and K.W. have patent applications on some of the concepts and immunogens discussed in this paper., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Elicitation of broadly neutralizing antibodies (bnAbs) by an HIV vaccine will involve priming the immune system to activate antibody precursors, followed by boosting immunizations to select for antibodies with functional features required for neutralization breadth. The higher the number of acquired mutations necessary for function, the more convoluted are the antibody developmental pathways. HIV bnAbs acquire a large number of somatic mutations, but not all mutations are functionally important. In this study, we identify a minimal subset of mutations sufficient for the function of the naturally occurring V3-glycan bnAb DH270.6. Using antibody library screening, candidate envelope immunogens that interact with DH270.6-like antibodies containing this set of key mutations are identified and selected in vitro. Our results demonstrate that less complex B cell evolutionary pathways than those naturally observed exist for the induction of HIV bnAbs by vaccination, and they establish rational approaches to identify boosting candidate immunogens., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

The continual emergence of novel coronaviruses (CoV), such as severe acute respiratory syndrome-(SARS)-CoV-2, highlights the critical need for broadly reactive therapeutics and vaccines against this family of viruses. From a recovered SARS-CoV donor sample, we identify and characterize a panel of six monoclonal antibodies that cross-react with CoV spike (S) proteins from the highly pathogenic SARS-CoV and SARS-CoV-2, and demonstrate a spectrum of reactivity against other CoVs. Epitope mapping reveals that these antibodies recognize multiple epitopes on SARS-CoV-2 S, including the receptor-binding domain, the N-terminal domain, and the S2 subunit. Functional characterization demonstrates that the antibodies mediate phagocytosis-and in some cases trogocytosis-but not neutralization in vitro . When tested in vivo in murine models, two of the antibodies demonstrate a reduction in hemorrhagic pathology in the lungs. The identification of cross-reactive epitopes recognized by functional antibodies expands the repertoire of targets for pan-coronavirus vaccine design strategies., Competing Interests: A.R.S. and I.S.G. are co-founders of AbSeek Bio. A.R.S., K.J.K., I.S.G., D.W., N.W., and J.S.M. are listed as inventors on patents filed describing the antibodies mentioned here. D.W., J.S.M., B.S.G., and N.W. are also listed as inventors on US patent application no. 62/972,886 (2019-nCoV vaccine). M.S.D. is a consultant for Inbios, Vir Biotechnology, NGM Biopharmaceuticals, and Carnival Corporation and is on the Scientific Advisory Boards of Moderna and Immunome. The Diamond laboratory has unrelated sponsored research agreements from Emergent BioSolutions, Moderna, and Vir Biotechnology. J.E.C. has served as a consultant for Eli Lilly, GlaxoSmithKline, and Luna Biologics; is a member of the Scientific Advisory Boards of CompuVax and Meissa Vaccines; and is Founder of IDBiologics. The Crowe laboratory at Vanderbilt University Medical Center has received sponsored research agreements from IDBiologics and AstraZeneca. R.S.B. has competing interests associated with Eli Lily, Takeda Pharmaceuticals, and Pfizer. The Georgiev laboratory at Vanderbilt University Medical Center has received unrelated funding from Takeda Pharmaceuticals., (© 2021 The Author(s).)

Natural antibodies (Abs) can target host glycans on the surface of pathogens. We studied the evolution of glycan-reactive B cells of rhesus macaques and humans using glycosylated HIV-1 envelope (Env) as a model antigen. 2G12 is a broadly neutralizing Ab (bnAb) that targets a conserved glycan patch on Env of geographically diverse HIV-1 strains using a unique heavy-chain (V H ) domain-swapped architecture that results in fragment antigen-binding (Fab) dimerization. Here, we describe HIV-1 Env Fab-dimerized glycan (FDG)-reactive bnAbs without V H -swapped domains from simian-human immunodeficiency virus (SHIV)-infected macaques. FDG Abs also recognized cell-surface glycans on diverse pathogens, including yeast and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike. FDG precursors were expanded by glycan-bearing immunogens in macaques and were abundant in HIV-1-naive humans. Moreover, FDG precursors were predominately mutated IgM + IgD + CD27 + , thus suggesting that they originated from a pool of antigen-experienced IgM + or marginal zone B cells., Competing Interests: Declaration of interests B.A. and W.E.W. are co-founders of Chemitope Technologies, and G.M.L. is a founder of Avidea Technologies that now commercially produce peptides used in our HIV-1 vaccination regimen. The remaining authors declare no competing interests., (Copyright © 2021 Elsevier Inc. All rights reserved.)

The severe acute respiratory coronavirus 2 (SARS-CoV-2) spike (S) protein is the target of vaccine design efforts to end the coronavirus disease 2019 (COVID-19) pandemic. Despite a low mutation rate, isolates with the D614G substitution in the S protein appeared early during the pandemic and are now the dominant form worldwide. Here, we explore S conformational changes and the effects of the D614G mutation on a soluble S ectodomain construct. Cryoelectron microscopy (cryo-EM) structures reveal altered receptor binding domain (RBD) disposition; antigenicity and proteolysis experiments reveal structural changes and enhanced furin cleavage efficiency of the G614 variant. Furthermore, furin cleavage alters the up/down ratio of the RBDs in the G614 S ectodomain, demonstrating an allosteric effect on RBD positioning triggered by changes in the SD2 region, which harbors residue 614 and the furin cleavage site. Our results elucidate SARS-CoV-2 S conformational landscape and allostery and have implications for vaccine design., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.)

HIV-1-infected infants develop broadly neutralizing antibodies (bnAbs) more rapidly than adults, suggesting differences in the neonatal versus adult responses to the HIV-1 envelope (Env). Here, trimeric forms of HIV-1 Env immunogens elicit increased gp120- and gp41-specific antibodies more rapidly in neonatal macaques than adult macaques. Transcriptome analyses of neonatal versus adult immune cells after Env vaccination reveal that neonatal macaques have higher levels of the apoptosis regulator BCL2 in T cells and lower levels of the immunosuppressive interleukin-10 (IL-10) receptor alpha (IL10RA) mRNA transcripts in T cells, B cells, natural killer (NK) cells, and monocytes. In addition, immunized neonatal macaques exhibit increased frequencies of activated blood T follicular helper-like (Tfh) cells compared to adults. Thus, neonatal macaques have transcriptome signatures of decreased immunosuppression and apoptosis compared with adult macaques, providing an immune landscape conducive to early-life immunization prior to sexual debut., Competing Interests: Declaration of Interests B.F.H. and K.O.S. have patent applications for some of the immunogens used in this study., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

The aim of this work was to start collecting information on rational combination of antibody (Ab) and T cell vaccines into single regimens. Two promising candidate HIV-1 vaccine strategies, sequential isolates of CH505 virus Envs developed for initiation of broadly neutralizing antibody lineages and conserved-mosaic tHIVconsvX immunogens aiming to induce effective cross-clade T cell responses, were combined to assess vaccine interactions. These immunogens were delivered in heterologous vector/modality regimens consisting of non-replicating simian (chimpanzee) adenovirus ChAdOx1 (C), non-replicating poxvirus MVA (M), and adjuvanted protein (P). Outbred CD1-SWISS mice were vaccinated intramuscularly using either parallel CM8M (tHIVconsvX)/CPPP (CH505) or sequential CM16M (tHIVconsvX)/CPPP (CH505) protocols, the latter of which delivered T cell CM prior to the CH505 Env. CM8M (tHIVconsvX) and CPPP or CMMP (CH505) vaccinations alone were included as comparators. The vaccine-elicited HIV-1-specific trimer-binding and neutralizing Abs and CD8 + /CD4 + T cell responses induced by the combined and comparator regimens were not statistically separable among regimens. The Ab-lineage immunogen strategy was particularly suited for combined regimens for its likely less potent induction of Env-specific T cell responses relative to homologous epitope-based vaccine strategies. These results inform design of the first rationally combined Ab and T cell vaccine regimens in human volunteers.

Despite the enormous effort in the development of effective vaccines against HIV-1, no vaccine candidate has elicited broadly neutralizing antibodies in humans. Thus, generation of more effective anti-HIV vaccines is critically needed. Here we characterize the immune responses induced by nucleoside-modified and purified mRNA-lipid nanoparticle (mRNA-LNP) vaccines encoding the clade C transmitted/founder HIV-1 envelope (Env) 1086C. Intradermal vaccination with nucleoside-modified 1086C Env mRNA-LNPs elicited high levels of gp120-specific antibodies in rabbits and rhesus macaques. Antibodies generated in rabbits neutralized a tier 1 virus, but no tier 2 neutralization activity could be measured. Importantly, three of six non-human primates developed antibodies that neutralized the autologous tier 2 strain. Despite stable anti-gp120 immunoglobulin G (IgG) levels, tier 2 neutralization titers started to drop 4 weeks after booster immunizations. Serum from both immunized rabbits and non-human primates demonstrated antibody-dependent cellular cytotoxicity activity. Collectively, these results are supportive of continued development of nucleoside-modified and purified mRNA-LNP vaccines for HIV. Optimization of Env immunogens and vaccination protocols are needed to increase antibody neutralization breadth and durability., (Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved.)

The events required for the induction of broad neutralizing antibodies (bnAbs) following HIV-1 envelope (Env) vaccination are unknown, and their induction in animal models as proof of concept would be critical. Here, we describe the induction of plasma antibodies capable of neutralizing heterologous primary (tier 2) HIV-1 strains in one macaque and two rabbits. Env immunogens were designed to induce CD4 binding site (CD4bs) bnAbs, but surprisingly, the macaque developed V1V2-glycan bnAbs. Env immunization of CD4bs bnAb heavy chain rearrangement (V H DJ H ) knockin mice similarly induced V1V2-glycan neutralizing antibodies (nAbs), wherein the human CD4bs V H  chains were replaced with mouse rearrangements bearing diversity region (D)-D fusions, creating antibodies with long, tyrosine-rich HCDR3s. Our results show that Env vaccination can elicit broad neutralization of tier 2 HIV-1, demonstrate that V1V2-glycan bnAbs are more readily induced than CD4bs bnAbs, and define V H replacement and diversity region fusion as potential mechanisms for generating V1V2-glycan bnAb site antibodies., (Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.)

Induction of broadly neutralizing antibodies (bnAbs) that target HIV-1 envelope (Env) is a goal of HIV-1 vaccine development. A bnAb target is the Env third variable loop (V3)-glycan site. To determine whether immunization could induce antibodies to the V3-glycan bnAb binding site, we repetitively immunized macaques over a 4-year period with an Env expressing V3-high mannose glycans. Env immunizations elicited plasma antibodies that neutralized HIV-1 expressing only high-mannose glycans-a characteristic shared by early bnAb B cell lineage members. A rhesus recombinant monoclonal antibody from a vaccinated macaque bound to the V3-glycan site at the same amino acids as broadly neutralizing antibodies. A structure of the antibody bound to glycan revealed that the three variable heavy-chain complementarity-determining regions formed a cavity into which glycan could insert and neutralized multiple HIV-1 isolates with high-mannose glycans. Thus, HIV-1 Env vaccination induced mannose-dependent antibodies with characteristics of V3-glycan bnAb precursors., (Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.)

Detailed studies of the broadly neutralizing antibodies (bNAbs) that underlie the best available examples of the humoral immune response to HIV are providing important information for the development of therapies and prophylaxis for HIV-1 infection. Here, we report a CD4-binding site (CD4bs) antibody, named N6, that potently neutralized 98% of HIV-1 isolates, including 16 of 20 that were resistant to other members of its class. N6 evolved a mode of recognition such that its binding was not impacted by the loss of individual contacts across the immunoglobulin heavy chain. In addition, structural analysis revealed that the orientation of N6 permitted it to avoid steric clashes with glycans, which is a common mechanism of resistance. Thus, an HIV-1-specific bNAb can achieve potent, near-pan neutralization of HIV-1, making it an attractive candidate for use in therapy and prophylaxis., (Published by Elsevier Inc.)

The design of an effective HIV-1 vaccine remains a major challenge. Several vaccine strategies based on viral vectors have been evaluated in preclinical and clinical trials, with largely disappointing results. Integrase defective lentiviral vectors (IDLV) represent a promising vaccine candidate given their ability to induce durable and protective immune responses in mice after a single immunization. Here, we evaluated the immunogenicity of a SIV-based IDLV in nonhuman primates. Six rhesus monkeys were primed intramuscularly with IDLV-Env and boosted with the same vector after 1 year. A single immunization with IDLV-Env induced broad humoral and cellular immune responses that waned over time but were still detectable at 1 year postprime. The boost with IDLV-Env performed at 1 year from the prime induced a remarkable increase in both antibodies and T-cell responses. Antibody binding specificity showed a predominant cross-clade gp120-directed response. Monkeys' sera efficiently blocked anti-V2 and anti-CD4 binding site antibodies, neutralized the tier 1 MW965.26 pseudovirus and mediated antibody-dependent cellular cytotoxicity (ADCC). Durable polyfunctional Env-specific T-cell responses were also elicited. Our study demonstrates that an IDLV-Env-based vaccine induces functional, comprehensive, and durable immune responses in Rhesus macaques. These results support further evaluation of IDLV as a new HIV-1 vaccine delivery platform.

Antibodies with ontogenies from VH1-2 or VH1-46-germline genes dominate the broadly neutralizing response against the CD4-binding site (CD4bs) on HIV-1. Here, we define with longitudinal sampling from time-of-infection the development of a VH1-46-derived antibody lineage that matured to neutralize 90% of HIV-1 isolates. Structures of lineage antibodies CH235 (week 41 from time-of-infection, 18% breadth), CH235.9 (week 152, 77%), and CH235.12 (week 323, 90%) demonstrated the maturing epitope to focus on the conformationally invariant portion of the CD4bs. Similarities between CH235 lineage and five unrelated CD4bs lineages in epitope focusing, length-of-time to develop breadth, and extraordinary level of somatic hypermutation suggested commonalities in maturation among all CD4bs antibodies. Fortunately, the required CH235-lineage hypermutation appeared substantially guided by the intrinsic mutability of the VH1-46 gene, which closely resembled VH1-2. We integrated our CH235-lineage findings with a second broadly neutralizing lineage and HIV-1 co-evolution to suggest a vaccination strategy for inducing both lineages., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Antibodies that neutralize autologous transmitted/founder (TF) HIV occur in most HIV-infected individuals and can evolve to neutralization breadth. Autologous neutralizing antibodies (nAbs) against neutralization-resistant (Tier-2) viruses are rarely induced by vaccination. Whereas broadly neutralizing antibody (bnAb)-HIV-Envelope structures have been defined, the structures of autologous nAbs have not. Here, we show that immunization with TF mutant Envs gp140 oligomers induced high-titer, V5-dependent plasma neutralization for a Tier-2 autologous TF evolved mutant virus. Structural analysis of autologous nAb DH427 revealed binding to V5, demonstrating the source of narrow nAb specificity and explaining the failure to acquire breadth. Thus, oligomeric TF Envs can elicit autologous nAbs to Tier-2 HIVs, but induction of bnAbs will require targeting of precursors of B cell lineages that can mature to heterologous neutralization., (Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.)