RESUMO
A key barrier to the development of vaccines that induce broadly neutralizing antibodies (bnAbs) against human immunodeficiency virus (HIV) and other viruses of high antigenic diversity is the design of priming immunogens that induce rare bnAb-precursor B cells. The high neutralization breadth of the HIV bnAb 10E8 makes elicitation of 10E8-class bnAbs desirable; however, the recessed epitope within gp41 makes envelope trimers poor priming immunogens and requires that 10E8-class bnAbs possess a long heavy chain complementarity determining region 3 (HCDR3) with a specific binding motif. We developed germline-targeting epitope scaffolds with affinity for 10E8-class precursors and engineered nanoparticles for multivalent display. Scaffolds exhibited epitope structural mimicry and bound bnAb-precursor human naive B cells in ex vivo screens, protein nanoparticles induced bnAb-precursor responses in stringent mouse models and rhesus macaques, and mRNA-encoded nanoparticles triggered similar responses in mice. Thus, germline-targeting epitope scaffold nanoparticles can elicit rare bnAb-precursor B cells with predefined binding specificities and HCDR3 features.
Assuntos
Vacinas contra a AIDS , Anticorpos Neutralizantes , Anticorpos Anti-HIV , Proteína gp41 do Envelope de HIV , Infecções por HIV , HIV-1 , Macaca mulatta , Animais , Humanos , Proteína gp41 do Envelope de HIV/imunologia , Anticorpos Anti-HIV/imunologia , Camundongos , Vacinas contra a AIDS/imunologia , Anticorpos Neutralizantes/imunologia , HIV-1/imunologia , Infecções por HIV/imunologia , Infecções por HIV/prevenção & controle , Infecções por HIV/virologia , Vacinação , Anticorpos Amplamente Neutralizantes/imunologia , Linfócitos B/imunologia , Nanopartículas/química , Feminino , Regiões Determinantes de Complementaridade/imunologia , Epitopos/imunologiaRESUMO
Conventional immunization strategies will likely be insufficient for the development of a broadly neutralizing antibody (bnAb) vaccine for HIV or other difficult pathogens because of the immunological hurdles posed, including B cell immunodominance and germinal center (GC) quantity and quality. We found that two independent methods of slow delivery immunization of rhesus monkeys (RMs) resulted in more robust T follicular helper (TFH) cell responses and GC B cells with improved Env-binding, tracked by longitudinal fine needle aspirates. Improved GCs correlated with the development of >20-fold higher titers of autologous nAbs. Using a new RM genomic immunoglobulin locus reference, we identified differential IgV gene use between immunization modalities. Ab mapping demonstrated targeting of immunodominant non-neutralizing epitopes by conventional bolus-immunized animals, whereas slow delivery-immunized animals targeted a more diverse set of epitopes. Thus, alternative immunization strategies can enhance nAb development by altering GCs and modulating the immunodominance of non-neutralizing epitopes.
Assuntos
Anticorpos Neutralizantes/imunologia , Linfócitos B/imunologia , Centro Germinativo/imunologia , Anticorpos Anti-HIV/imunologia , HIV-1/imunologia , Imunização Passiva , Linfócitos T Auxiliares-Indutores/imunologia , Animais , Linfócitos B/patologia , Feminino , Centro Germinativo/patologia , Centro Germinativo/virologia , Macaca mulatta , Masculino , Linfócitos T Auxiliares-Indutores/patologia , Produtos do Gene env do Vírus da Imunodeficiência Humana/imunologiaRESUMO
Vaccines generate high-affinity antibodies by recruiting antigen-specific B cells to germinal centers (GCs), but the mechanisms governing the recruitment to GCs on secondary challenges remain unclear. Here, using preclinical SARS-CoV and HIV mouse models, we demonstrated that the antibodies elicited during primary humoral responses shaped the naive B cell recruitment to GCs during secondary exposures. The antibodies from primary responses could either enhance or, conversely, restrict the GC participation of naive B cells: broad-binding, low-affinity, and low-titer antibodies enhanced recruitment, whereas, by contrast, the high titers of high-affinity, mono-epitope-specific antibodies attenuated cognate naive B cell recruitment. Thus, the directionality and intensity of that effect was determined by antibody concentration, affinity, and epitope specificity. Circulating antibodies can, therefore, be important determinants of antigen immunogenicity. Future vaccines may need to overcome-or could, alternatively, leverage-the effects of circulating primary antibodies on subsequent naive B cell recruitment.
Assuntos
Linfócitos B , Centro Germinativo , Animais , Anticorpos Neutralizantes , Anticorpos Antivirais , Antígenos , Epitopos , Imunidade Humoral , CamundongosRESUMO
Passive administration of HIV neutralizing antibodies (nAbs) can protect macaques from hard-to-neutralize (tier 2) chimeric simian-human immunodeficiency virus (SHIV) challenge. However, conditions for nAb-mediated protection after vaccination have not been established. Here, we selected groups of 6 rhesus macaques with either high or low serum nAb titers from a total of 78 animals immunized with recombinant native-like (SOSIP) Env trimers. Repeat intrarectal challenge with homologous tier 2 SHIVBG505 led to rapid infection in unimmunized and low-titer animals. High-titer animals, however, demonstrated protection that was gradually lost as nAb titers waned over time. An autologous serum ID50 nAb titer of â¼1:500 afforded more than 90% protection from medium-dose SHIV infection. In contrast, antibody-dependent cellular cytotoxicity and T cell activity did not correlate with protection. Therefore, Env protein-based vaccination strategies can protect against hard-to-neutralize SHIV challenge in rhesus macaques by inducing tier 2 nAbs, provided appropriate neutralizing titers can be reached and maintained.
Assuntos
Vacinas contra a AIDS/imunologia , Anticorpos Anti-HIV/imunologia , Infecções por HIV/imunologia , HIV/fisiologia , Síndrome de Imunodeficiência Adquirida dos Símios/imunologia , Vírus da Imunodeficiência Símia/fisiologia , Produtos do Gene env do Vírus da Imunodeficiência Humana/imunologia , Animais , Anticorpos Neutralizantes/imunologia , Humanos , Macaca mulatta , VacinaçãoRESUMO
The elicitation of broadly neutralizing antibodies (bNAbs) against the HIV-1 envelope glycoprotein (Env) trimer remains a major vaccine challenge. Most cross-conserved protein determinants are occluded by self-N-glycan shielding, limiting B cell recognition of the underlying polypeptide surface. The exceptions to the contiguous glycan shield include the conserved receptor CD4 binding site (CD4bs) and glycoprotein (gp)41 elements proximal to the furin cleavage site. Accordingly, we performed heterologous trimer-liposome prime:boosting in rabbits to drive B cells specific for cross-conserved sites. To preferentially expose the CD4bs to B cells, we eliminated proximal N-glycans while maintaining the native-like state of the cleavage-independent NFL trimers, followed by gradual N-glycan restoration coupled with heterologous boosting. This approach successfully elicited CD4bs-directed, cross-neutralizing Abs, including one targeting a unique glycan-protein epitope and a bNAb (87% breadth) directed to the gp120:gp41 interface, both resolved by high-resolution cryoelectron microscopy. This study provides proof-of-principle immunogenicity toward eliciting bNAbs by vaccination.
Assuntos
Vacinas contra a AIDS/imunologia , Anticorpos Neutralizantes/imunologia , Anticorpos Anti-HIV/imunologia , Infecções por HIV/imunologia , HIV-1/imunologia , Lipossomos , Produtos do Gene env do Vírus da Imunodeficiência Humana/imunologia , Animais , Linfócitos B/imunologia , Linfócitos B/metabolismo , Antígenos CD4/química , Antígenos CD4/imunologia , Antígenos CD4/metabolismo , Complemento C3/imunologia , Complemento C3/metabolismo , Apresentação Cruzada/imunologia , Epitopos/imunologia , Glicosilação , Infecções por HIV/virologia , Humanos , Imunoglobulina G/imunologia , Modelos Moleculares , Testes de Neutralização , Polissacarídeos/imunologia , Polissacarídeos/metabolismo , Ligação Proteica , Conformação Proteica , Coelhos , Produtos do Gene env do Vírus da Imunodeficiência Humana/administração & dosagem , Produtos do Gene env do Vírus da Imunodeficiência Humana/química , Produtos do Gene env do Vírus da Imunodeficiência Humana/metabolismoRESUMO
Germinal centres are the engines of antibody evolution. Here, using human immunodeficiency virus (HIV) Env protein immunogen priming in rhesus monkeys followed by a long period without further immunization, we demonstrate germinal centre B (BGC) cells that last for at least 6 months. A 186-fold increase in BGC cells was present by week 10 compared with conventional immunization. Single-cell transcriptional profiling showed that both light- and dark-zone germinal centre states were sustained. Antibody somatic hypermutation of BGC cells continued to accumulate throughout the 29-week priming period, with evidence of selective pressure. Env-binding BGC cells were still 49-fold above baseline at 29 weeks, which suggests that they could remain active for even longer periods of time. High titres of HIV-neutralizing antibodies were generated after a single booster immunization. Fully glycosylated HIV trimer protein is a complex antigen, posing considerable immunodominance challenges for B cells1,2. Memory B cells generated under these long priming conditions had higher levels of antibody somatic hypermutation, and both memory B cells and antibodies were more likely to recognize non-immunodominant epitopes. Numerous BGC cell lineage phylogenies spanning more than the 6-month germinal centre period were identified, demonstrating continuous germinal centre activity and selection for at least 191 days with no further antigen exposure. A long-prime, slow-delivery (12 days) immunization approach holds promise for difficult vaccine targets and suggests that patience can have great value for tuning of germinal centres to maximize antibody responses.
Assuntos
Afinidade de Anticorpos , Linfócitos B , Movimento Celular , Células Clonais , Centro Germinativo , Anticorpos Anti-HIV , Imunização , Animais , Anticorpos Neutralizantes/genética , Anticorpos Neutralizantes/imunologia , Afinidade de Anticorpos/genética , Afinidade de Anticorpos/imunologia , Linfócitos B/citologia , Linfócitos B/imunologia , Células Clonais/citologia , Células Clonais/imunologia , Epitopos de Linfócito B/imunologia , Perfilação da Expressão Gênica , Centro Germinativo/citologia , Centro Germinativo/imunologia , Anticorpos Anti-HIV/genética , Anticorpos Anti-HIV/imunologia , Infecções por HIV/imunologia , HIV-1/imunologia , Humanos , Imunização Secundária , Macaca mulatta/imunologia , Macaca mulatta/virologia , Células B de Memória/citologia , Células B de Memória/imunologia , Análise de Célula Única , Hipermutação Somática de Imunoglobulina/genética , Hipermutação Somática de Imunoglobulina/imunologia , Fatores de Tempo , Produtos do Gene env do Vírus da Imunodeficiência Humana/administração & dosagem , Produtos do Gene env do Vírus da Imunodeficiência Humana/imunologiaRESUMO
Characterizing polyclonal antibody responses via currently available methods is inherently complex and difficult. Mapping epitopes in an immune response is typically incomplete, which creates a barrier to fully understanding the humoral response to antigens and hinders rational vaccine design efforts. Here, we describe a method of characterizing polyclonal responses by using electron microscopy, and we applied this method to the immunization of rabbits with an HIV-1 envelope glycoprotein vaccine candidate, BG505 SOSIP.664. We detected known epitopes within the polyclonal sera and revealed how antibody responses evolved during the prime-boosting strategy to ultimately result in a neutralizing antibody response. We uncovered previously unidentified epitopes, including an epitope proximal to one recognized by human broadly neutralizing antibodies as well as potentially distracting non-neutralizing epitopes. Our method provides an efficient and semiquantitative map of epitopes that are targeted in a polyclonal antibody response and should be of widespread utility in vaccine and infection studies.
Assuntos
Vacinas contra a AIDS/imunologia , Anticorpos Neutralizantes/imunologia , Mapeamento de Epitopos/métodos , Epitopos/imunologia , Anticorpos Anti-HIV/imunologia , HIV-1/imunologia , Microscopia Eletrônica/métodos , Produtos do Gene env do Vírus da Imunodeficiência Humana/imunologia , Animais , Formação de Anticorpos/imunologia , Linhagem Celular , Feminino , Células HEK293 , Infecções por HIV/imunologia , Infecções por HIV/prevenção & controle , Humanos , Imunização , Fragmentos Fab das Imunoglobulinas/imunologia , Coelhos , Proteínas Recombinantes/imunologiaRESUMO
Broadly neutralizing antibodies (bnAbs) to HIV delineate vaccine targets and are prophylactic and therapeutic agents. Some of the most potent bnAbs target a quaternary epitope at the apex of the surface HIV envelope (Env) trimer. Using cryo-electron microscopy, we solved the atomic structure of an apex bnAb, PGT145, in complex with Env. We showed that the long anionic HCDR3 of PGT145 penetrated between glycans at the trimer 3-fold axis, to contact peptide residues from all three Env protomers, and thus explains its highly trimer-specific nature. Somatic hypermutation in the other CDRs of PGT145 were crucially involved in stabilizing the structure of the HCDR3, similar to bovine antibodies, to aid in recognition of a cluster of conserved basic residues hypothesized to facilitate trimer disassembly during viral entry. Overall, the findings exemplify the creative solutions that the human immune system can evolve to recognize a conserved motif buried under a canopy of glycans.
Assuntos
Anticorpos Neutralizantes/química , Domínios Proteicos , Multimerização Proteica , Estrutura Secundária de Proteína , Produtos do Gene env do Vírus da Imunodeficiência Humana/química , Sequência de Aminoácidos , Ânions/química , Anticorpos Neutralizantes/imunologia , Anticorpos Neutralizantes/metabolismo , Microscopia Crioeletrônica , Cristalografia por Raios X , Epitopos/química , Epitopos/imunologia , Epitopos/metabolismo , Células HEK293 , Anticorpos Anti-HIV/química , Anticorpos Anti-HIV/imunologia , Anticorpos Anti-HIV/metabolismo , HIV-1/imunologia , HIV-1/metabolismo , Humanos , Modelos Moleculares , Polissacarídeos/química , Polissacarídeos/imunologia , Polissacarídeos/metabolismo , Ligação Proteica/imunologia , Homologia de Sequência de Aminoácidos , Ressonância de Plasmônio de Superfície , Produtos do Gene env do Vírus da Imunodeficiência Humana/imunologia , Produtos do Gene env do Vírus da Imunodeficiência Humana/metabolismoRESUMO
The development of stabilized recombinant HIV envelope trimers that mimic the virion surface molecule has increased enthusiasm for a neutralizing antibody (nAb)-based HIV vaccine. However, there is limited experience with recombinant trimers as immunogens in nonhuman primates, which are typically used as a model for humans. Here, we tested multiple immunogens and immunization strategies head-to-head to determine their impact on the quantity, quality, and kinetics of autologous tier 2 nAb development. A bilateral, adjuvanted, subcutaneous immunization protocol induced reproducible tier 2 nAb responses after only two immunizations 8 weeks apart, and these were further enhanced by a third immunization with BG505 SOSIP trimer. We identified immunogens that minimized non-neutralizing V3 responses and demonstrated that continuous immunogen delivery could enhance nAb responses. nAb responses were strongly associated with germinal center reactions, as assessed by lymph node fine needle aspiration. This study provides a framework for preclinical and clinical vaccine studies targeting nAb elicitation.
Assuntos
Vacinas contra a AIDS/imunologia , Anticorpos Neutralizantes/uso terapêutico , Centro Germinativo/imunologia , Anticorpos Anti-HIV/uso terapêutico , Infecções por HIV/terapia , HIV-1/imunologia , Animais , Células Cultivadas , Epitopos de Linfócito B/química , Epitopos de Linfócito B/imunologia , Centro Germinativo/virologia , Infecções por HIV/imunologia , Humanos , Imunização , Injeções Subcutâneas , Primatas , Multimerização Proteica , Produtos do Gene env do Vírus da Imunodeficiência Humana/química , Produtos do Gene env do Vírus da Imunodeficiência Humana/imunologiaRESUMO
Antibody heavy chain (HC) and light chain (LC) variable region exons are assembled by V(D)J recombination. V(D)J junctional regions encode complementarity-determining-region 3 (CDR3), an antigen-contact region immensely diversified through nontemplated nucleotide additions ("N-regions") by terminal deoxynucleotidyl transferase (TdT). HIV-1 vaccine strategies seek to elicit human HIV-1 broadly neutralizing antibodies (bnAbs), such as the potent CD4-binding site VRC01-class bnAbs. Mice with primary B cells that express receptors (BCRs) representing bnAb precursors are used as vaccination models. VRC01-class bnAbs uniformly use human HC VH1-2 and commonly use human LCs Vκ3-20 or Vκ1-33 associated with an exceptionally short 5-amino-acid (5-aa) CDR3. Prior VRC01-class models had nonphysiological precursor levels and/or limited precursor diversity. Here, we describe VRC01-class rearranging mice that generate more physiological primary VRC01-class BCR repertoires via rearrangement of VH1-2, as well as Vκ1-33 and/or Vκ3-20 in association with diverse CDR3s. Human-like TdT expression in mouse precursor B cells increased LC CDR3 length and diversity and also promoted the generation of shorter LC CDR3s via N-region suppression of dominant microhomology-mediated Vκ-to-Jκ joins. Priming immunization with eOD-GT8 60mer, which strongly engages VRC01 precursors, induced robust VRC01-class germinal center B cell responses. Vκ3-20-based responses were enhanced by N-region addition, which generates Vκ3-20-to-Jκ junctional sequence combinations that encode VRC01-class 5-aa CDR3s with a critical E residue. VRC01-class-rearranging models should facilitate further evaluation of VRC01-class prime and boost immunogens. These new VRC01-class mouse models establish a prototype for the generation of vaccine-testing mouse models for other HIV-1 bnAb lineages that employ different HC or LC Vs.
Assuntos
Infecções por HIV , Soropositividade para HIV , HIV-1 , Vacinas , Camundongos , Humanos , Animais , Anticorpos Amplamente Neutralizantes , Anticorpos Neutralizantes , HIV-1/genética , Anticorpos Anti-HIV , DNA Nucleotidilexotransferase , Regiões Determinantes de Complementaridade/genética , Infecções por HIV/prevenção & controleRESUMO
Many neutralizing antibodies (nAbs) elicited to ancestral severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) through natural infection and vaccination have reduced effectiveness to SARS-CoV-2 variants. Here, we show that therapeutic antibody ADG20 is able to neutralize SARS-CoV-2 variants of concern (VOCs) including Omicron (B.1.1.529) as well as other SARS-related coronaviruses. We delineate the structural basis of this relatively escape-resistant epitope that extends from one end of the receptor binding site (RBS) into the highly conserved CR3022 site. ADG20 can then benefit from high potency through direct competition with ACE2 in the more variable RBS and interaction with the more highly conserved CR3022 site. Importantly, antibodies that are able to target this site generally neutralize a broad range of VOCs, albeit with reduced potency against Omicron. Thus, this conserved and vulnerable site can be exploited for the design of universal vaccines and therapeutic antibodies.
Assuntos
Anticorpos Monoclonais , Anticorpos Neutralizantes , Anticorpos Antivirais , COVID-19 , SARS-CoV-2 , Glicoproteína da Espícula de Coronavírus , Anticorpos Monoclonais/imunologia , Anticorpos Neutralizantes/imunologia , Anticorpos Antivirais/imunologia , COVID-19/imunologia , COVID-19/virologia , Epitopos/imunologia , Humanos , Testes de Neutralização , SARS-CoV-2/imunologia , Glicoproteína da Espícula de Coronavírus/imunologiaRESUMO
The human immunodeficiency virus type 1 (HIV-1) trimeric envelope glycoprotein (Env) is heavily glycosylated, creating a dense glycan shield that protects the underlying peptidic surface from antibody recognition. The absence of conserved glycans, due to missing potential N-linked glycosylation sites (PNGS), can result in strain-specific, autologous neutralizing antibody (NAb) responses. Here, we sought to gain a deeper understanding of the autologous neutralization by introducing holes in the otherwise dense glycan shields of the AMC011 and AMC016 SOSIP trimers. Specifically, when we knocked out the N130 and N289 glycans, which are absent from the well-characterized B41 SOSIP trimer, we observed stronger autologous NAb responses. We also analyzed the highly variable NAb responses induced in rabbits by diverse SOSIP trimers from subtypes A, B, and C. Statistical analysis, using linear regression, revealed that the cumulative area exposed on a trimer by glycan holes correlates with the magnitude of the autologous NAb response. IMPORTANCE Forty years after the first description of HIV-1, the search for a protective vaccine is still ongoing. The sole target for antibodies that can neutralize the virus are the trimeric envelope glycoproteins (Envs) located on the viral surface. The glycoprotein surface is covered with glycans that shield off the underlying protein components from recognition by the immune system. However, the Env trimers of some viral strains have holes in the glycan shield. Immunized animals developed antibodies against such glycan holes. These antibodies are generally strain specific. Here, we sought to gain a deeper understanding of what drives these specific immune responses. First, we show that strain-specific neutralizing antibody responses can be increased by creating artificial holes in the glycan shield. Second, when studying a diverse set of Env trimers with different characteristics, we found that the surface area of the glycan holes contributes prominently to the induction of strain-specific neutralizing antibodies.
Assuntos
Infecções por HIV/imunologia , HIV-1/imunologia , Polissacarídeos/metabolismo , Multimerização Proteica , Produtos do Gene env do Vírus da Imunodeficiência Humana/imunologia , Produtos do Gene env do Vírus da Imunodeficiência Humana/metabolismo , Vacinas contra a AIDS/imunologia , Aminoácidos/química , Aminoácidos/imunologia , Aminoácidos/metabolismo , Animais , Anticorpos Neutralizantes/imunologia , Formação de Anticorpos/imunologia , Antígenos Virais/imunologia , Glicosilação , Anticorpos Anti-HIV/imunologia , Infecções por HIV/metabolismo , Infecções por HIV/virologia , HIV-1/genética , Interações Hospedeiro-Patógeno , Humanos , Imunização , Modelos Moleculares , Conformação Proteica , Multimerização Proteica/imunologia , Coelhos , Deleção de Sequência , Relação Estrutura-Atividade , Produtos do Gene env do Vírus da Imunodeficiência Humana/química , Produtos do Gene env do Vírus da Imunodeficiência Humana/genéticaRESUMO
Stabilized HIV-1 envelope (Env) trimers elicit tier 2 autologous neutralizing antibody (nAb) responses in immunized animals. We previously demonstrated that BG505 SOSIP.664.T332N gp140 (BG505 SOSIP) immunization of rhesus macaques (RM) provided robust protection against autologous intra-vaginal simian-human immunodeficiency virus (SHIV) challenge that was predicted by high serum nAb titers. Here, we show that nAb in these protected RM targeted a glycan hole proximal to residue 465 in gp120 in all cases. nAb also targeted another glycan hole at residues 241/289 and an epitope in V1 at varying frequencies. Non-neutralizing antibodies directed at N611-shielded epitopes in gp41 were also present but were more prevalent in RM with low nAb titers. Longitudinal analysis demonstrated that nAb broadened in some RM during sequential immunization but remained focused in others, the latter being associated with increases in nAb titer. Thirty-eight monoclonal antibodies (mAbs) isolated from a protected RM with an exceptionally high serum neutralization titer bound to the trimer in ELISA, and four of the mAbs potently neutralized the BG505 Env pseudovirus (PV) and SHIV. The four neutralizing mAbs were clonally related and targeted the 465 glycan hole to varying degrees, mimicking the serum. The data demonstrate that the C3/465 glycan hole cluster was the dominant neutralization target in high titer protected RM, despite other co-circulating neutralizing and non-neutralizing specificities. The isolation of a neutralizing mAb family argues that clonotype expansion occurred during BG505 SOSIP immunization, leading to high titer, protective nAb and setting a desirable benchmark for HIV vaccines.
Assuntos
Anticorpos Neutralizantes/imunologia , Anticorpos Anti-HIV/imunologia , HIV-1/imunologia , Polissacarídeos/imunologia , Síndrome de Imunodeficiência Adquirida dos Símios/prevenção & controle , Vírus da Imunodeficiência Símia/imunologia , Produtos do Gene env do Vírus da Imunodeficiência Humana/imunologia , Animais , Epitopos/imunologia , Feminino , Infecções por HIV/imunologia , Infecções por HIV/virologia , Humanos , Imunização , Macaca mulatta , Síndrome de Imunodeficiência Adquirida dos Símios/imunologia , Síndrome de Imunodeficiência Adquirida dos Símios/virologia , VacinaçãoRESUMO
Evaluating the structure-function relationship of viral envelope (Env) evolution and the development of broadly cross-neutralizing antibodies (bnAbs) in natural infection can inform rational immunogen design. In the present study, we examined the magnitude and specificity of autologous neutralizing antibodies induced in rabbits by a novel HIV-1 clade C Env protein (1PGE-THIVC) vis-à-vis those developed in an elite neutralizer from whom the env sequence was obtained that was used to prepare the soluble Env protein. The novel 1PGE-THIVC Env trimer displayed a native like pre-fusion closed conformation in solution as determined by small angle X-ray scattering (SAXS) and negative stain electron microscopy (EM). This closed spike conformation of 1PGE-THIVC Env trimers was correlated with weak or undetectable binding of non-neutralizing monoclonal antibodies (mAbs) compared to neutralizing mAbs. Furthermore, 1PGE-THIVC SOSIP induced potent neutralizing antibodies in rabbits to autologous virus variants. The autologous neutralizing antibody specificity induced in rabbits by 1PGE-THIVC was mapped to the C3/V4 region (T362/P401) of viral Env. This observation agreed with electron microscopy polyclonal epitope mapping (EMPEM) of the Env trimer complexed with IgG Fab prepared from the immunized rabbit sera. Our study demonstrated neutralization of sequence matched and unmatched autologous viruses by serum antibodies induced in rabbits by 1PGE-THIVC and also highlighted a comparable specificity for the 1PGE-THIVC SOSIP trimer with that seen with polyclonal antibodies elicited in the elite neutralizer by negative-stain electron microscopy polyclonal epitope (ns-EMPEM) mapping.
Assuntos
Anticorpos Neutralizantes/sangue , Antígenos Virais/sangue , Anticorpos Anti-HIV/sangue , HIV-1/imunologia , Animais , Anticorpos Neutralizantes/imunologia , Antígenos Virais/imunologia , Epitopos/imunologia , Anticorpos Anti-HIV/imunologia , Infecções por HIV/imunologia , Humanos , Imunização/métodos , Coelhos , Vacinação/métodos , Produtos do Gene env do Vírus da Imunodeficiência Humana/imunologiaRESUMO
The development of an effective human immunodeficiency virus (HIV-1) vaccine is a high global health priority. Soluble native-like HIV-1 envelope glycoprotein trimers (Env), including those based on the SOSIP design, have shown promise as vaccine candidates by inducing neutralizing antibody responses against the autologous virus in animal models. However, to overcome HIV-1's extreme diversity a vaccine needs to induce broadly neutralizing antibodies (bNAbs). Such bNAbs can protect non-human primates (NHPs) and humans from infection. The prototypic BG505 SOSIP.664 immunogen is based on the BG505 env sequence isolated from an HIV-1-infected infant from Kenya who developed a bNAb response. Studying bNAb development during natural HIV-1 infection can inform vaccine design, however, it is unclear to what extent vaccine-induced antibody responses to Env are comparable to those induced by natural infection. Here, we compared Env antibody responses in BG505 SOSIP-immunized NHPs with those in BG505 SHIV-infected NHPs, by analyzing monoclonal antibodies (mAbs). We observed three major differences between BG505 SOSIP immunization and BG505 SHIV infection. First, SHIV infection resulted in more clonal expansion and less antibody diversity compared to SOSIP immunization, likely because of higher and/or prolonged antigenic stimulation and increased antigen diversity during infection. Second, while we retrieved comparatively fewer neutralizing mAbs (NAbs) from SOSIP-immunized animals, these NAbs targeted more diverse epitopes compared to NAbs from SHIV-infected animals. However, none of the NAbs, either elicited by vaccination or infection, showed any breadth. Finally, SOSIP immunization elicited antibodies against the base of the trimer, while infection did not, consistent with the base being placed onto the virus membrane in the latter setting. Together these data provide new insights into the antibody response against BG505 Env during infection and immunization and limitations that need to be overcome to induce better responses after vaccination.
Assuntos
Vacinas contra a AIDS/administração & dosagem , Anticorpos Neutralizantes/imunologia , Epitopos/imunologia , Infecções por HIV/imunologia , HIV-1/imunologia , Síndrome de Imunodeficiência Adquirida dos Símios/imunologia , Produtos do Gene env do Vírus da Imunodeficiência Humana/imunologia , Vacinas contra a AIDS/imunologia , Animais , Anticorpos Monoclonais/administração & dosagem , Anticorpos Monoclonais/imunologia , Formação de Anticorpos , Antígenos Virais/imunologia , Anticorpos Anti-HIV/imunologia , Infecções por HIV/virologia , Humanos , Imunização , Lactente , Quênia , Primatas , Multimerização Proteica , Síndrome de Imunodeficiência Adquirida dos Símios/prevenção & controle , Vírus da Imunodeficiência Símia/imunologia , VacinaçãoRESUMO
For many enveloped viruses, binding to a receptor(s) on a host cell acts as the first step in a series of events culminating in fusion with the host cell membrane and transfer of genetic material for replication. The envelope glycoprotein (Env) trimer on the surface of HIV is responsible for receptor binding and fusion. Although Env can tolerate a high degree of mutation in five variable regions (V1-V5), and also at N-linked glycosylation sites that contribute roughly half the mass of Env, the functional sites for recognition of receptor CD4 and co-receptor CXCR4/CCR5 are conserved and essential for viral fitness. Soluble SOSIP Env trimers are structural and antigenic mimics of the pre-fusion native, surface-presented Env, and are targets of broadly neutralizing antibodies. Thus, they are attractive immunogens for vaccine development. Here we present high-resolution cryo-electron microscopy structures of subtype B B41 SOSIP Env trimers in complex with CD4 and antibody 17b, or with antibody b12, at resolutions of 3.7 Å and 3.6 Å, respectively. We compare these to cryo-electron microscopy reconstructions of B41 SOSIP Env trimers with no ligand or in complex with either CD4 or the CD4-binding-site antibody PGV04 at 5.6 Å, 5.2 Å and 7.4 Å resolution, respectively. Consequently, we present the most complete description yet, to our knowledge, of the CD4-17b-induced intermediate and provide the molecular basis of the receptor-binding-induced conformational change required for HIV-1 entry into host cells. Both CD4 and b12 induce large, previously uncharacterized conformational rearrangements in the gp41 subunits, and the fusion peptide becomes buried in a newly formed pocket. These structures provide key details on the biological function of the type I viral fusion machine from HIV-1 as well as new templates for inhibitor design.
Assuntos
Regulação Alostérica , Microscopia Crioeletrônica , HIV-1/química , HIV-1/ultraestrutura , Produtos do Gene env do Vírus da Imunodeficiência Humana/metabolismo , Produtos do Gene env do Vírus da Imunodeficiência Humana/ultraestrutura , Regulação Alostérica/efeitos dos fármacos , Sequência de Aminoácidos , Anticorpos/química , Anticorpos/imunologia , Anticorpos/farmacologia , Anticorpos/ultraestrutura , Sítios de Ligação/efeitos dos fármacos , Antígenos CD4/química , Antígenos CD4/metabolismo , Antígenos CD4/ultraestrutura , Proteína gp41 do Envelope de HIV/química , Proteína gp41 do Envelope de HIV/genética , Proteína gp41 do Envelope de HIV/metabolismo , Proteína gp41 do Envelope de HIV/ultraestrutura , Fragmentos Fab das Imunoglobulinas/química , Fragmentos Fab das Imunoglobulinas/imunologia , Fragmentos Fab das Imunoglobulinas/farmacologia , Fragmentos Fab das Imunoglobulinas/ultraestrutura , Ligantes , Modelos Moleculares , Receptores CCR5/química , Receptores CCR5/metabolismo , Receptores de HIV/química , Receptores de HIV/metabolismo , Receptores de HIV/ultraestrutura , Produtos do Gene env do Vírus da Imunodeficiência Humana/química , Produtos do Gene env do Vírus da Imunodeficiência Humana/genéticaRESUMO
The dense array of N-linked glycans on the HIV-1 envelope glycoprotein (Env), known as the "glycan shield," is a key determinant of immunogenicity, yet intrinsic heterogeneity confounds typical structure-function analysis. Here, we present an integrated approach of single-particle electron cryomicroscopy (cryo-EM), computational modeling, and site-specific mass spectrometry (MS) to probe glycan shield structure and behavior at multiple levels. We found that dynamics lead to an extensive network of interglycan interactions that drive the formation of higher-order structure within the glycan shield. This structure defines diffuse boundaries between buried and exposed protein surface and creates a mapping of potentially immunogenic sites on Env. Analysis of Env expressed in different cell lines revealed how cryo-EM can detect subtle changes in glycan occupancy, composition, and dynamics that impact glycan shield structure and epitope accessibility. Importantly, this identified unforeseen changes in the glycan shield of Env obtained from expression in the same cell line used for vaccine production. Finally, by capturing the enzymatic deglycosylation of Env in a time-resolved manner, we found that highly connected glycan clusters are resistant to digestion and help stabilize the prefusion trimer, suggesting the glycan shield may function beyond immune evasion.