Eliciting broadly neutralizing antibodies (bnAbs) that target the HIV-1 envelope glycoprotein (Env) remains a central goal of HIV vaccine design. Among these, antibodies directed against the V1/V2 apex epitope represent an important class of bnAbs with potent and broad neutralizing activity. As HIV-1 bnAbs often require extensive somatic hypermutation, a complete understanding of bnAb maturation pathways is essential to guide bnAb development during immunization.
Here, we combine negative-stain electron microscopy polyclonal epitope mapping (nsEMPEM) and cryo-electron microscopy (cryo-EM) to characterize potent and broad V1/V2 apex antibodies elicited in rhesus macaques immunized with the germline targeting immunogen CAP256.GT1.
nsEMPEM analyses identified apex-targeting antibodies present in sera twelve weeks after the priming immunization, indicating successful engagement of desired precursor lineages. Polyclonal epitope mapping and biophysical characterization of antibody responses to candidate immunogens guided subsequent boosting strategies and successfully facilitated bnAb development. High-resolution cryo-EM structures of bnAbs isolated over a year after the priming immunization revealed that these antibodies recapitulate the binding modes and structural features observed in human-derived V1/V2 apex bnAbs isolated from chronically infected donors, further supporting the utility of nonhuman primate models for evaluating germline-targeting immunogens.
Together, these findings demonstrate the applicability of structural and polyclonal epitope mapping approaches in guiding rational vaccine design.
Howard Hughes Medical Institute Emerging Pathogens Initiative; Bill and Melinda Gates Foundation Collaboration for AIDS Vaccine Discovery (CAVD); National Institutes of Health National Institute of Allergy and Infectious Diseases (NIH NIAID) Grants R01 AI 167716, R61 AI 161818, P01 AI 177683
Vaccines and Immunotherapy (VAC)
Ipsita Krishnamurthy, Xuduo Li, Raiees Andrabi et al.· Journal of Immunology· 0 citations
The continued emergence of betacoronaviruses underscores the urgent need for vaccines that provide broadly protective immunity. Here, we present an epitope-focused vaccine strategy targeting the conserved S2 stem-helix region of the spike fusion machinery, a broadly neutralizing antibody-(bnAb) epitope shared across betacoronaviruses yet partially occluded on the native spike. Immunization of non-human primates with engineered S2 stem-helix nanoparticle immunogens, alone or followed by a SARS-CoV-2 BA.1 spike mRNA boost, elicited broadly cross-reactive antibody responses against sarbecoviruses, merbecoviruses, and embecoviruses and neutralized SARS-CoV-2, multiple variants, other sarbecoviruses, and MERS-CoV. Vaccine-elicited monoclonal antibodies displayed broad in-vitro neutralizing activity and protected against both SARS-CoV-2 and MERS-CoV in-vivo. Structural analyses revealed conserved features between rhesus and human stem-helix bnAbs, supporting the translational potential. Overall, our findings provide proof-of-concept that epitope-focused nanoparticle immunogens can target partially occluded, immunoquiescent bnAb epitopes, laying the groundwork for pan-betacoronavirus vaccines that provide broad protection and strengthen pandemic preparedness. ONE SENTENCE SUMMARY Epitope-focused S2 stem-helix nanoparticle immunogens elicit protective broadly neutralizing antibodies (bnAbs) against diverse betacoronaviruses in non-human primates, establishing a framework for development of pan-betacoronavirus vaccines.
Panpan Zhou, Ziqi Feng, Wan-ting He et al.· bioRxiv· 0 citations
The isolation of a human monoclonal antibody from a SARS-CoV-2 convalescent donor that targets the conserved S2 stem helix region is reported, demonstrating the potential of in vitro affinity maturation to expand the neutralization breadth of stem-helix-targeting antibodies across divergent betacoronaviruses.
Panpan Zhou, M. Yuan, Yue-Xiu Zhang et al.· PLoS Pathogens· 0 citations
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