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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., (© 2024. The Author(s).)

HIV Envelope (Env) is the main vaccine target for induction of neutralizing antibodies. Stabilizing Env into native-like trimer (NLT) conformations is required for recombinant protein immunogens to induce autologous neutralizing antibodies(nAbs) against difficult to neutralize HIV strains (tier-2) in rabbits and non-human primates. Immunizations of mice with NLTs have generally failed to induce tier-2 nAbs. Here, we show that DNA-encoded NLTs fold properly in vivo and induce autologous tier-2 nAbs in mice. DNA-encoded NLTs also uniquely induce both CD4 + and CD8 + T-cell responses as compared to corresponding protein immunizations. Murine neutralizing antibodies are identified with an advanced sequencing technology. The structure of an Env-Ab (C05) complex, as determined by cryo-EM, identifies a previously undescribed neutralizing Env C3/V5 epitope. Beyond potential functional immunity gains, DNA vaccines permit in vivo folding of structured antigens and provide significant cost and speed advantages for enabling rapid evaluation of new HIV vaccines., (© 2022. The Author(s).)

In vaccine design, antigens are often arrayed in a multivalent nanoparticle form, but in vivo mechanisms underlying the enhanced immunity elicited by such vaccines remain poorly understood. We compared the fates of two different heavily glycosylated HIV antigens, a gp120-derived mini-protein and a large, stabilized envelope trimer, in protein nanoparticle or "free" forms after primary immunization. Unlike monomeric antigens, nanoparticles were rapidly shuttled to the follicular dendritic cell (FDC) network and then concentrated in germinal centers in a complement-, mannose-binding lectin (MBL)-, and immunogen glycan-dependent manner. Loss of FDC localization in MBL-deficient mice or via immunogen deglycosylation significantly affected antibody responses. These findings identify an innate immune-mediated recognition pathway promoting antibody responses to particulate antigens, with broad implications for humoral immunity and vaccine design., (Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

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 SHIV BG505 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 ID 50 nAb titer of ∼1:500 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., (Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.)

Elicitation of broadly neutralizing antibodies (bnAbs) is a primary HIV vaccine goal. Native-like trimers mimicking virion-associated spikes present nearly all bnAb epitopes and are therefore promising vaccine antigens. However, first generation native-like trimers expose epitopes for non-neutralizing antibodies (non-nAbs), which may hinder bnAb induction. We here employ computational and structure-guided design to develop improved native-like trimers that reduce exposure of non-nAb epitopes in the V3-loop and trimer base, minimize both CD4 reactivity and CD4-induced non-nAb epitope exposure, and increase thermal stability while maintaining bnAb antigenicity. In rabbit immunizations with native-like trimers of the 327c isolate, improved trimers suppress elicitation of V3-directed and tier-1 neutralizing antibodies and induce robust autologous tier-2 neutralization, unlike a first-generation trimer. The improved native-like trimers from diverse HIV isolates, and the design methods, have promise to assist in the development of a HIV vaccine.

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., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

A major goal of HIV-1 vaccine research is the design of immunogens capable of inducing broadly neutralizing antibodies (bnAbs) that bind to the viral envelope glycoprotein (Env). Poor binding of Env to unmutated precursors of bnAbs, including those of the VRC01 class, appears to be a major problem for bnAb induction. We engineered an immunogen that binds to VRC01-class bnAb precursors and immunized knock-in mice expressing germline-reverted VRC01 heavy chains. Induced antibodies showed characteristics of VRC01-class bnAbs, including a short CDRL3 (light-chain complementarity-determining region 3) and mutations that favored binding to near-native HIV-1 gp120 constructs. In contrast, native-like immunogens failed to activate VRC01-class precursors. The results suggest that rational epitope design can prime rare B cell precursors for affinity maturation to desired targets., (Copyright © 2015, American Association for the Advancement of Science.)

Broadly neutralizing monoclonal antibodies (bnmAbs) that target the high-mannose patch centered around the glycan at position 332 on HIV Env are promising vaccine leads and therapeutic candidates because they effectively protect against mucosal SHIV challenge and strongly suppress SHIV viremia in established infection in macaque models. However, these antibodies demonstrate varying degrees of dependency on the N332 glycan site, and the origins of their neutralization breadth are not always obvious. By measuring neutralization on an extended range of glycan site viral variants, we found that some bnmAbs can use alternate N-linked glycans in the absence of the N332 glycan site and therefore neutralize a substantial number of viruses lacking the site. Furthermore, many of the antibodies can neutralize viruses in which the N332 glycan site is shifted to the 334 position. Finally, we found that a combination of three antibody families that target the high-mannose patch can lead to 99% neutralization coverage of a large panel of viruses containing the N332/N334 glycan site and up to 66% coverage for viruses that lack the N332/N334 glycan site. The results indicate that a diverse response against the high-mannose patch may provide near-equivalent coverage as a combination of bnmAbs targeting multiple epitopes. Additionally, the ability of some bnmAbs to use other N-linked glycan sites can help counter neutralization escape mediated by shifting of glycosylation sites. Overall, this work highlights the importance of promiscuous glycan binding properties in bnmAbs to the high-mannose patch for optimal antiviral activity in either protective or therapeutic modalities., (Copyright © 2014, American Association for the Advancement of Science.)