Publications by authors named "Daniel W Kulp"

46 Publications

A DNA-Launched Nanoparticle Vaccine Elicits CD8 T-cell Immunity to Promote Tumor Control.

Cancer Immunol Res 2020 11 10;8(11):1354-1364. Epub 2020 Sep 10.

The Vaccine and Immunotherapy Center, Wistar Institute, Philadelphia, Pennsylvania.

Cytolytic T cells (CTL) play a pivotal role in surveillance against tumors. Induction of CTL responses by vaccination may be challenging, as it requires direct transduction of target cells or special adjuvants to promote cross-presentation. Here, we observed induction of robust CTL responses through electroporation-facilitated, DNA-launched nanoparticle vaccination (DLnano-vaccines). Electroporation was observed to mediate transient tissue apoptosis and macrophage infiltration, which were deemed essential to the induction of CTLs by DLnano-vaccines through a systemic macrophage depletion study. Bolus delivery of protein nano-vaccines followed by electroporation, however, failed to induce CTLs, suggesting direct production of nano-vaccines may be required. Following these observations, new DLnano-vaccines scaffolding immunodominant melanoma Gp100 and Trp2 epitopes were designed and shown to induce more potent and consistent epitope-specific CTL responses than the corresponding DNA monomeric vaccines or CpG-adjuvanted peptide vaccines. DNA, but not recombinant protein, nano-vaccinations induced CTL responses to these epitopes and suppressed melanoma tumor growth in mouse models in a CD8 T-cell-dependent fashion. Further studies to explore the use of DLnano-vaccines against other cancer targets and the biology with which they induce CTLs are important.
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http://dx.doi.org/10.1158/2326-6066.CIR-20-0061DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7642117PMC
November 2020

SARS-CoV-2 Assays To Detect Functional Antibody Responses That Block ACE2 Recognition in Vaccinated Animals and Infected Patients.

J Clin Microbiol 2020 10 21;58(11). Epub 2020 Oct 21.

Vaccine and Immunotherapy Center, Wistar Institute, Philadelphia, Pennsylvania, USA

evere cute espiratory yndrome ronairus (SARS-CoV-2) has caused a global pandemic of COVID-19, resulting in cases of mild to severe respiratory distress and significant mortality. The global outbreak of this novel coronavirus has now infected >20 million people worldwide, with >5 million cases in the United States (11 August 2020). The development of diagnostic and research tools to determine infection and vaccine efficacy is critically needed. We have developed multiple serologic assays using newly designed SARS-CoV-2 reagents for detecting the presence of receptor-binding antibodies in sera. The first assay is surface plasmon resonance (SPR) based and can quantitate both antibody binding to the SARS-CoV-2 spike protein and blocking to the Angiotensin-converting enzyme 2 (ACE2) receptor in a single experiment. The second assay is enzyme-linked immunosorbent assay (ELISA) based and can measure competition and blocking of the ACE2 receptor to the SARS-CoV-2 spike protein with antispike antibodies. The assay is highly versatile, and we demonstrate the broad utility of the assay by measuring antibody functionality of sera from small animals and nonhuman primates immunized with an experimental SARS-CoV-2 vaccine. In addition, we employ the assay to measure receptor blocking of sera from SARS-CoV-2-infected patients. The assay is shown to correlate with pseudovirus neutralization titers. This type of rapid, surrogate neutralization diagnostic can be employed widely to help study SARS-CoV-2 infection and assess the efficacy of vaccines.
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http://dx.doi.org/10.1128/JCM.01533-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7587116PMC
October 2020

Incorporation of a Novel CD4+ Helper Epitope Identified from Aquifex aeolicus Enhances Humoral Responses Induced by DNA and Protein Vaccinations.

iScience 2020 Aug 6;23(8):101399. Epub 2020 Aug 6.

The Vaccine and Immunotherapy Center, Wistar Institute, Philadelphia, PA 19104, USA. Electronic address:

CD4+ T cells play an important role in the maturation of the antibody responses. Conjugation of identified CD4+ T cell helper epitope to the target antigen has been developed as a strategy to enhance vaccine-induced humoral immunity. In this work, we reported the identification of a novel HLA-IAb helper epitope LS-3 from Aquifex aeolicus. In silico analysis predicted this epitope to have high binding affinity to common human HLA alleles and have complementary binding coverage to the established PADRE epitope. Introduction of HLA-IAb knockout mutations to the LS-3 epitope significantly attenuated humoral responses induced by a vaccine containing this epitope. Finally, engineered fusion of the epitope to a model antigen, influenza hemagglutinin, significantly improved both binding and hemagglutination inhibition antibody responses in mice receiving DNA or protein vaccines. In summary, LS-3 and additional identified CD4+ helper epitopes may be further explored to improve vaccine responses in translational studies.
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http://dx.doi.org/10.1016/j.isci.2020.101399DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7409978PMC
August 2020

Immunogenicity of a DNA vaccine candidate for COVID-19.

Nat Commun 2020 05 20;11(1):2601. Epub 2020 May 20.

Inovio Pharmaceuticals, Plymouth Meeting, Philadelphia, PA, 19462, USA.

The coronavirus family member, SARS-CoV-2 has been identified as the causal agent for the pandemic viral pneumonia disease, COVID-19. At this time, no vaccine is available to control further dissemination of the disease. We have previously engineered a synthetic DNA vaccine targeting the MERS coronavirus Spike (S) protein, the major surface antigen of coronaviruses, which is currently in clinical study. Here we build on this prior experience to generate a synthetic DNA-based vaccine candidate targeting SARS-CoV-2 S protein. The engineered construct, INO-4800, results in robust expression of the S protein in vitro. Following immunization of mice and guinea pigs with INO-4800 we measure antigen-specific T cell responses, functional antibodies which neutralize the SARS-CoV-2 infection and block Spike protein binding to the ACE2 receptor, and biodistribution of SARS-CoV-2 targeting antibodies to the lungs. This preliminary dataset identifies INO-4800 as a potential COVID-19 vaccine candidate, supporting further translational study.
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http://dx.doi.org/10.1038/s41467-020-16505-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7239918PMC
May 2020

In Vivo Assembly of Nanoparticles Achieved through Synergy of Structure-Based Protein Engineering and Synthetic DNA Generates Enhanced Adaptive Immunity.

Adv Sci (Weinh) 2020 Apr 27;7(8):1902802. Epub 2020 Feb 27.

The Vaccine and Immunotherapy Center The Wistar Institute Philadelphia PA 19104 USA.

Nanotechnologies are considered to be of growing importance to the vaccine field. Through decoration of immunogens on multivalent nanoparticles, designed nanovaccines can elicit improved humoral immunity. However, significant practical and monetary challenges in large-scale production of nanovaccines have impeded their widespread clinical translation. Here, an alternative approach is illustrated integrating computational protein modeling and adaptive electroporation-mediated synthetic DNA delivery, thus enabling direct in vivo production of nanovaccines. DNA-launched nanoparticles are demonstrated displaying an HIV immunogen spontaneously self-assembled in vivo. DNA-launched nanovaccines induce stronger humoral responses than their monomeric counterparts in both mice and guinea pigs, and uniquely elicit CD8+ effector T-cell immunity as compared to recombinant protein nanovaccines. Improvements in vaccine responses recapitulate when DNA-launched nanovaccines with alternative scaffolds and decorated antigen are designed and evaluated. Finally, evaluation of functional immune responses induced by DLnanovaccines demonstrates that, in comparison to control mice or mice immunized with DNA-encoded hemagglutinin monomer, mice immunized with a DNA-launched hemagglutinin nanoparticle vaccine fully survive a lethal influenza challenge, and have substantially lower viral load, weight loss, and influenza-induced lung pathology. Additional study of these next-generation in vivo-produced nanovaccines may offer advantages for immunization against multiple disease targets.
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http://dx.doi.org/10.1002/advs.201902802DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7175333PMC
April 2020

Engineered immunogen binding to alum adjuvant enhances humoral immunity.

Nat Med 2020 03 17;26(3):430-440. Epub 2020 Feb 17.

Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA.

Adjuvants are central to the efficacy of subunit vaccines. Aluminum hydroxide (alum) is the most commonly used vaccine adjuvant, yet its adjuvanticity is often weak and mechanisms of triggering antibody responses remain poorly understood. We demonstrate that site-specific modification of immunogens with short peptides composed of repeating phosphoserine (pSer) residues enhances binding to alum and prolongs immunogen bioavailability. The pSer-modified immunogens formulated in alum elicited greatly increased germinal center, antibody, neutralizing antibody, memory and long-lived plasma cell responses compared to conventional alum-adsorbed immunogens. Mechanistically, pSer-immunogen:alum complexes form nanoparticles that traffic to lymph nodes and trigger B cell activation through multivalent and oriented antigen display. Direct uptake of antigen-decorated alum particles by B cells upregulated antigen processing and presentation pathways, further enhancing B cell activation. These data provide insights into mechanisms of action of alum and introduce a readily translatable approach to significantly improve humoral immunity to subunit vaccines using a clinical adjuvant.
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http://dx.doi.org/10.1038/s41591-020-0753-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7069805PMC
March 2020

In vivo delivery of synthetic DNA-encoded antibodies induces broad HIV-1-neutralizing activity.

J Clin Invest 2020 02;130(2):827-837

Vaccine and Immunotherapy Center, The Wistar Institute, Philadelphia, Pennsylvania, USA.

Interventions to prevent HIV-1 infection and alternative tools in HIV cure therapy remain pressing goals. Recently, numerous broadly neutralizing HIV-1 monoclonal antibodies (bNAbs) have been developed that possess the characteristics necessary for potential prophylactic or therapeutic approaches. However, formulation complexities, especially for multiantibody deliveries, long infusion times, and production issues could limit the use of these bNAbs when deployed, globally affecting their potential application. Here, we describe an approach utilizing synthetic DNA-encoded monoclonal antibodies (dmAbs) for direct in vivo production of prespecified neutralizing activity. We designed 16 different bNAbs as dmAb cassettes and studied their activity in small and large animals. Sera from animals administered dmAbs neutralized multiple HIV-1 isolates with activity similar to that of their parental recombinant mAbs. Delivery of multiple dmAbs to a single animal led to increased neutralization breadth. Two dmAbs, PGDM1400 and PGT121, were advanced into nonhuman primates for study. High peak-circulating levels (between 6 and 34 μg/ml) of these dmAbs were measured, and the sera of all animals displayed broad neutralizing activity. The dmAb approach provides an important local delivery platform for the in vivo generation of HIV-1 bNAbs and for other infectious disease antibodies.
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http://dx.doi.org/10.1172/JCI132779DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6994112PMC
February 2020

A generalized HIV vaccine design strategy for priming of broadly neutralizing antibody responses.

Science 2019 12 31;366(6470). Epub 2019 Oct 31.

Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA 92037, USA.

Vaccine induction of broadly neutralizing antibodies (bnAbs) to HIV remains a major challenge. Germline-targeting immunogens hold promise for initiating the induction of certain bnAb classes; yet for most bnAbs, a strong dependence on antibody heavy chain complementarity-determining region 3 (HCDR3) is a major barrier. Exploiting ultradeep human antibody sequencing data, we identified a diverse set of potential antibody precursors for a bnAb with dominant HCDR3 contacts. We then developed HIV envelope trimer-based immunogens that primed responses from rare bnAb-precursor B cells in a mouse model and bound a range of potential bnAb-precursor human naïve B cells in ex vivo screens. Our repertoire-guided germline-targeting approach provides a framework for priming the induction of many HIV bnAbs and could be applied to most HCDR3-dominant antibodies from other pathogens.
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http://dx.doi.org/10.1126/science.aax4380DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7092357PMC
December 2019

Enhancing humoral immunity via sustained-release implantable microneedle patch vaccination.

Proc Natl Acad Sci U S A 2019 08 29;116(33):16473-16478. Epub 2019 Jul 29.

Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139;

Sustained exposure of lymphoid tissues to vaccine antigens promotes humoral immunity, but traditional bolus immunizations lead to rapid antigen clearance. We describe a technology to tailor vaccine kinetics in a needle-free platform translatable to human immunization. Solid pyramidal microneedle (MN) arrays were fabricated with silk fibroin protein tips encapsulating a stabilized HIV envelope trimer immunogen and adjuvant, supported on a dissolving polymer base. Upon brief skin application, vaccine-loaded silk tips are implanted in the epidermis/upper dermis where they release vaccine over a time period determined by the crystallinity of the silk matrix. Following MN immunization in mice, Env trimer was released over 2 wk in the skin, correlating with increased germinal center (GC) B cell responses, a ∼1,300-fold increase in serum IgG titers and a 16-fold increase in bone marrow (BM) plasma cells compared with bolus immunization. Thus, implantable MNs provide a practical means to substantially enhance humoral immunity to subunit vaccines.
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http://dx.doi.org/10.1073/pnas.1902179116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6697788PMC
August 2019

Slow Delivery Immunization Enhances HIV Neutralizing Antibody and Germinal Center Responses via Modulation of Immunodominance.

Cell 2019 05 9;177(5):1153-1171.e28. Epub 2019 May 9.

Division of Vaccine Discovery, La Jolla Institute for Immunology (LJI), La Jolla, CA 92037, USA; Center for HIV/AIDS Vaccine Immunology and Immunogen Discovery (Scripps CHAVI-ID), The Scripps Research Institute, La Jolla, CA 92037, USA; Department of Medicine, University of California, San Diego, La Jolla, CA 92037, USA. Electronic address:

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 (T) 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.
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http://dx.doi.org/10.1016/j.cell.2019.04.012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6619430PMC
May 2019

Protein engineering and particulate display of B-cell epitopes to facilitate development of novel vaccines.

Curr Opin Immunol 2019 08 28;59:49-56. Epub 2019 Apr 28.

Vaccine and Immunotherapy Center, The Wistar Institute, Philadelphia, PA 19104, United States. Electronic address:

Induction of antigen-specific humoral immunity is a correlate of protection for many diseases and remains a primary vaccine goal. Pathogens can evade such responses by limiting epitope access, by diversifying surface residues, or by keeping antigens in metastable conformations. B cells can target diverse epitopes on an antigen, but only a subset of which produce functional antibodies. Structure-based immunogen engineering can help overcome these hurdles by using structural information for targeted induction of particular antibodies while improving the overall vaccine immunogenicity. This review will cover recent progress in vaccine design, specifically focusing on strategies to stabilize antigens for optimal B-cell epitope exposure, engineer synthetic B-cell epitopes to induce antibodies with specific features and enhancement of vaccine potency through antigen presentation on multivalent particles.
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http://dx.doi.org/10.1016/j.coi.2019.03.003DOI Listing
August 2019

Innate immune recognition of glycans targets HIV nanoparticle immunogens to germinal centers.

Science 2019 02 20;363(6427):649-654. Epub 2018 Dec 20.

Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

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.
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http://dx.doi.org/10.1126/science.aat9120DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6420719PMC
February 2019

Vaccine-Induced Protection from Homologous Tier 2 SHIV Challenge in Nonhuman Primates Depends on Serum-Neutralizing Antibody Titers.

Immunity 2019 01 11;50(1):241-252.e6. Epub 2018 Dec 11.

Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA 92037, USA; Center for HIV/AIDS Vaccine Immunology and Immunogen Discovery (CHAVI-ID), The Scripps Research Institute, La Jolla, CA 92037, USA; IAVI Neutralizing Antibody Center and the Collaboration for AIDS Vaccine Discovery (CAVD), The Scripps Research Institute, La Jolla, CA 92037, USA; Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, and Harvard University, Cambridge, MA 02139, USA. Electronic address:

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 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 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.
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http://dx.doi.org/10.1016/j.immuni.2018.11.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6335502PMC
January 2019

Enhancing Humoral Responses Against HIV Envelope Trimers via Nanoparticle Delivery with Stabilized Synthetic Liposomes.

Sci Rep 2018 11 8;8(1):16527. Epub 2018 Nov 8.

Koch Institute, MIT, Massachusetts, USA.

An HIV vaccine capable of eliciting durable neutralizing antibody responses continues to be an important unmet need. Multivalent nanoparticles displaying a high density of envelope trimers may be promising immunogen forms to elicit strong and durable humoral responses to HIV, but critical particle design criteria remain to be fully defined. To this end, we developed strategies to covalently anchor a stabilized gp140 trimer, BG505 MD39, on the surfaces of synthetic liposomes to study the effects of trimer density and vesicle stability on vaccine-elicited humoral responses in mice. CryoEM imaging revealed homogeneously distributed and oriented MD39 on the surface of liposomes irrespective of particle size, lipid composition, and conjugation strategy. Immunization with covalent MD39-coupled liposomes led to increased germinal center and antigen-specific T follicular helper cell responses and significantly higher avidity serum MD39-specific IgG responses compared to immunization with soluble MD39 trimers. A priming immunization with liposomal-MD39 was important for elicitation of high avidity antibody responses, regardless of whether booster immunizations were administered with either soluble or particulate trimers. The stability of trimer anchoring to liposomes was critical for these effects, as germinal center and output antibody responses were further increased by liposome compositions incorporating sphingomyelin that exhibited high in vitro stability in the presence of serum. Together these data highlight key liposome design features for optimizing humoral immunity to lipid nanoparticle immunogens.
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http://dx.doi.org/10.1038/s41598-018-34853-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6224390PMC
November 2018

The human naive B cell repertoire contains distinct subclasses for a germline-targeting HIV-1 vaccine immunogen.

Sci Transl Med 2018 07;10(448)

Division of Vaccine Discovery, La Jolla Institute for Allergy and Immunology, La Jolla, CA 92037, USA.

Traditional vaccine development to prevent some of the worst current pandemic diseases has been unsuccessful so far. Germline-targeting immunogens have potential to prime protective antibodies (Abs) via more targeted immune responses. Success of germline-targeting vaccines in humans will depend on the composition of the human naive B cell repertoire, including the frequencies and affinities of epitope-specific B cells. However, the human naive B cell repertoire remains largely undefined. Assessment of antigen-specific human naive B cells among hundreds of millions of B cells from multiple donors may be used as pre-phase 1 ex vivo human testing to potentially forecast B cell and Ab responses to new vaccine designs. VRC01 is an HIV broadly neutralizing Ab (bnAb) against the envelope CD4-binding site (CD4bs). We characterized naive human B cells recognizing eOD-GT8, a germline-targeting HIV-1 vaccine candidate immunogen designed to prime VRC01-class Abs. Several distinct subclasses of VRC01-class naive B cells were identified, sharing sequence characteristics with inferred precursors of known bnAbs VRC01, VRC23, PCIN63, and N6. Multiple naive B cell clones exactly matched mature VRC01-class bnAb L-CDR3 sequences. Non-VRC01-class B cells were also characterized, revealing recurrent public light chain sequences. Unexpectedly, we also identified naive B cells related to the IOMA-class CD4bs bnAb. These different subclasses within the human repertoire had strong initial affinities () to the immunogen, up to 13 nM, and represent encouraging indications that multiple independent pathways may exist for vaccine-elicited VRC01-class bnAb development in most individuals. The frequencies of these distinct eOD-GT8 B cell specificities give insights into antigen-specific compositional features of the human naive B cell repertoire and provide actionable information for vaccine design and advancement.
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http://dx.doi.org/10.1126/scitranslmed.aat0381DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6145074PMC
July 2018

Precursor Frequency and Affinity Determine B Cell Competitive Fitness in Germinal Centers, Tested with Germline-Targeting HIV Vaccine Immunogens.

Immunity 2018 01 26;48(1):133-146.e6. Epub 2017 Dec 26.

Division of Vaccine Discovery, La Jolla Institute for Allergy and Immunology, La Jolla, CA, 92037, USA; Center for HIV/AIDS Vaccine Immunology and Immunogen Discovery (CHAVI-ID), The Scripps Research Institute, La Jolla, CA 92037, USA; Division of Infectious Diseases, Department of Medicine, University of California San Diego, La Jolla, CA 92037, USA. Electronic address:

How precursor frequencies and antigen affinities impact interclonal B cell competition is a particularly relevant issue for candidate germline-targeting HIV vaccine designs because of the in vivo rarity of naive B cells that recognize broadly neutralizing epitopes. Knowing the frequencies and affinities of HIV-specific VRC01-class naive human B cells, we transferred B cells with germline VRC01 B cell receptors into congenic recipients to elucidate the roles of precursor frequency, antigen affinity, and avidity on B cell responses following immunization. All three factors were interdependently limiting for competitive success of VRC01-class B cells. In physiological high-affinity conditions using a multivalent immunogen, rare VRC01-class B cells successfully competed in germinal centers (GC), underwent extensive somatic hypermutation, and differentiated into memory B cells. The data reveal dominant influences of precursor frequency, affinity, and avidity for interclonal GC competition and indicate that germline-targeting immunogens can overcome these challenges with high-affinity multimeric designs.
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http://dx.doi.org/10.1016/j.immuni.2017.11.023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5773359PMC
January 2018

Structure-based design of native-like HIV-1 envelope trimers to silence non-neutralizing epitopes and eliminate CD4 binding.

Nat Commun 2017 11 21;8(1):1655. Epub 2017 Nov 21.

Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA, 92037, USA.

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.
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http://dx.doi.org/10.1038/s41467-017-01549-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5698488PMC
November 2017

Elicitation of Robust Tier 2 Neutralizing Antibody Responses in Nonhuman Primates by HIV Envelope Trimer Immunization Using Optimized Approaches.

Immunity 2017 06;46(6):1073-1088.e6

Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA 92037, USA; Center for HIV/AIDS Vaccine Immunology and Immunogen Discovery, The Scripps Research Institute, La Jolla, CA 92037, USA; IAVI Neutralizing Antibody Center and the Collaboration for AIDS Vaccine Discovery, The Scripps Research Institute, La Jolla, CA 92037, USA; Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, and Harvard University, Cambridge, MA 02139, USA. Electronic address:

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.
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http://dx.doi.org/10.1016/j.immuni.2017.05.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5483234PMC
June 2017

Global site-specific N-glycosylation analysis of HIV envelope glycoprotein.

Nat Commun 2017 03 28;8:14954. Epub 2017 Mar 28.

Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA.

HIV-1 envelope glycoprotein (Env) is the sole target for broadly neutralizing antibodies (bnAbs) and the focus for design of an antibody-based HIV vaccine. The Env trimer is covered by ∼90N-linked glycans, which shield the underlying protein from immune surveillance. bNAbs to HIV develop during infection, with many showing dependence on glycans for binding to Env. The ability to routinely assess the glycan type at each glycosylation site may facilitate design of improved vaccine candidates. Here we present a general mass spectrometry-based proteomics strategy that uses specific endoglycosidases to introduce mass signatures that distinguish peptide glycosites that are unoccupied or occupied by high-mannose/hybrid or complex-type glycans. The method yields >95% sequence coverage for Env, provides semi-quantitative analysis of the glycosylation status at each glycosite. We find that most glycosites in recombinant Env trimers are fully occupied by glycans, varying in the proportion of high-mannose/hybrid and complex-type glycans.
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http://dx.doi.org/10.1038/ncomms14954DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5379070PMC
March 2017

Effects of partially dismantling the CD4 binding site glycan fence of HIV-1 Envelope glycoprotein trimers on neutralizing antibody induction.

Virology 2017 05 6;505:193-209. Epub 2017 Mar 6.

San Diego Biomedical Research Institute, 10865 Road to the Cure, San Diego, CA 92121, USA. Electronic address:

Previously, VLPs bearing JR-FL strain HIV-1 Envelope trimers elicited potent neutralizing antibodies (nAbs) in 2/8 rabbits (PLoS Pathog 11(5): e1004932) by taking advantage of a naturally absent glycan at position 197 that borders the CD4 binding site (CD4bs). In new immunizations, we attempted to improve nAb responses by removing the N362 glycan that also lines the CD4bs. All 4 rabbits developed nAbs. One targeted the N197 glycan hole like our previous sera. Two sera depended on the N463 glycan, again suggesting CD4bs overlap. Heterologous boosts appeared to reduce nAb clashes with the N362 glycan. The fourth serum targeted a N362 glycan-sensitive epitope. VLP manufacture challenges prevented us from immunizing larger rabbit numbers to empower a robust statistical analysis. Nevertheless, trends suggest that targeted glycan removal may improve nAb induction by exposing new epitopes and that it may be possible to modify nAb specificity using rational heterologous boosts.
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http://dx.doi.org/10.1016/j.virol.2017.02.024DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5895097PMC
May 2017

HIV Vaccine Design to Target Germline Precursors of Glycan-Dependent Broadly Neutralizing Antibodies.

Immunity 2016 09 8;45(3):483-496. Epub 2016 Sep 8.

Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA 92037, USA; IAVI Neutralizing Antibody Center, The Scripps Research Institute, La Jolla, CA 92037, USA; Center for HIV/AIDS Vaccine Immunology and Immunogen Discovery, The Scripps Research Institute, La Jolla, CA 92037, USA; The Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology and Harvard University, Cambridge, MA 02139, USA. Electronic address:

Broadly neutralizing antibodies (bnAbs) against the N332 supersite of the HIV envelope (Env) trimer are the most common bnAbs induced during infection, making them promising leads for vaccine design. Wild-type Env glycoproteins lack detectable affinity for supersite-bnAb germline precursors and are therefore unsuitable immunogens to prime supersite-bnAb responses. We employed mammalian cell surface display to design stabilized Env trimers with affinity for germline-reverted precursors of PGT121-class supersite bnAbs. The trimers maintained native-like antigenicity and structure, activated PGT121 inferred-germline B cells ex vivo when multimerized on liposomes, and primed PGT121-like responses in PGT121 inferred-germline knockin mice. Design intermediates have levels of epitope modification between wild-type and germline-targeting trimers; their mutation gradient suggests sequential immunization to induce bnAbs, in which the germline-targeting prime is followed by progressively less-mutated design intermediates and, lastly, with native trimers. The vaccine design strategies described could be utilized to target other epitopes on HIV or other pathogens.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5040827PMC
http://dx.doi.org/10.1016/j.immuni.2016.08.016DOI Listing
September 2016

Tailored Immunogens Direct Affinity Maturation toward HIV Neutralizing Antibodies.

Cell 2016 Sep;166(6):1459-1470.e11

Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA 92037, USA; IAVI Neutralizing Antibody Center, The Scripps Research Institute, La Jolla, CA 92037, USA; Center for HIV/AIDS Vaccine Immunology and Immunogen Discovery, The Scripps Research Institute, La Jolla, CA 92037, USA; Ragon Institute of MGH, MIT and Harvard, Cambridge, MA 02129, USA. Electronic address:

Induction of broadly neutralizing antibodies (bnAbs) is a primary goal of HIV vaccine development. VRC01-class bnAbs are important vaccine leads because their precursor B cells targeted by an engineered priming immunogen are relatively common among humans. This priming immunogen has demonstrated the ability to initiate a bnAb response in animal models, but recall and maturation toward bnAb development has not been shown. Here, we report the development of boosting immunogens designed to guide the genetic and functional maturation of previously primed VRC01-class precursors. Boosting a transgenic mouse model expressing germline VRC01 heavy chains produced broad neutralization of near-native isolates (N276A) and weak neutralization of fully native HIV. Functional and genetic characteristics indicate that the boosted mAbs are consistent with partially mature VRC01-class antibodies and place them on a maturation trajectory that leads toward mature VRC01-class bnAbs. The results show how reductionist sequential immunization can guide maturation of HIV bnAb responses.
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http://dx.doi.org/10.1016/j.cell.2016.08.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5018249PMC
September 2016

Sequential Immunization Elicits Broadly Neutralizing Anti-HIV-1 Antibodies in Ig Knockin Mice.

Cell 2016 Sep;166(6):1445-1458.e12

Laboratory of Molecular Immunology and Howard Hughes Medical Institute, The Rockefeller University, New York, NY 10065, USA. Electronic address:

A vaccine that elicits broadly neutralizing antibodies (bNAbs) against HIV-1 is likely to be protective, but this has not been achieved. To explore immunization regimens that might elicit bNAbs, we produced and immunized mice expressing the predicted germline PGT121, a bNAb specific for the V3-loop and surrounding glycans on the HIV-1 spike. Priming with an epitope-modified immunogen designed to activate germline antibody-expressing B cells, followed by ELISA-guided boosting with a sequence of directional immunogens, native-like trimers with decreasing epitope modification, elicited heterologous tier-2-neutralizing responses. In contrast, repeated immunization with the priming immunogen did not. Antibody cloning confirmed elicitation of high levels of somatic mutation and tier-2-neutralizing antibodies resembling the authentic human bNAb. Our data establish that sequential immunization with specifically designed immunogens can induce high levels of somatic mutation and shepherd antibody maturation to produce bNAbs from their inferred germline precursors.
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http://dx.doi.org/10.1016/j.cell.2016.07.030DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5019122PMC
September 2016

Priming HIV-1 broadly neutralizing antibody precursors in human Ig loci transgenic mice.

Science 2016 09 8;353(6307):1557-1560. Epub 2016 Sep 8.

Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA 92037, USA. International AIDS Vaccine Initiative (IAVI) Neutralizing Antibody Center, The Scripps Research Institute, La Jolla, CA 92037, USA. Center for HIV/AIDS Vaccine Immunology and Immunogen Discovery, The Scripps Research Institute, La Jolla, CA 92037, USA. Ragon Institute of Massachusetts General Hospital (MGH), MIT, and Harvard, Cambridge, MA 02129, USA.

A major obstacle to a broadly neutralizing antibody (bnAb)-based HIV vaccine is the activation of appropriate B cell precursors. Germline-targeting immunogens must be capable of priming rare bnAb precursors in the physiological setting. We tested the ability of the VRC01-class bnAb germline-targeting immunogen eOD-GT8 60mer (60-subunit self-assembling nanoparticle) to activate appropriate precursors in mice transgenic for human immunoglobulin (Ig) loci. Despite an average frequency of, at most, about one VRC01-class precursor per mouse, we found that at least 29% of singly immunized mice produced a VRC01-class memory response, suggesting that priming generally succeeded when at least one precursor was present. The results demonstrate the feasibility of using germline targeting to prime specific and exceedingly rare bnAb-precursor B cells within a humanlike repertoire.
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http://dx.doi.org/10.1126/science.aah3945DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5404394PMC
September 2016

Holes in the Glycan Shield of the Native HIV Envelope Are a Target of Trimer-Elicited Neutralizing Antibodies.

Cell Rep 2016 08 18;16(9):2327-38. Epub 2016 Aug 18.

Department of Immunology & Microbial Science, IAVI Neutralizing Antibody Center, The Scripps Research Institute, La Jolla, CA 92037, USA; Center for HIV/AIDS Vaccine Immunology and Immunogen Discovery, The Scripps Research Institute, La Jolla, CA 92037, USA; Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology and Harvard University, Cambridge, MA 02139, USA. Electronic address:

A major advance in the search for an HIV vaccine has been the development of a near-native Envelope trimer (BG505 SOSIP.664) that can induce robust autologous Tier 2 neutralization. Here, potently neutralizing monoclonal antibodies (nAbs) from rabbits immunized with BG505 SOSIP.664 are shown to recognize an immunodominant region of gp120 centered on residue 241. Residue 241 occupies a hole in the glycan defenses of the BG505 isolate, with fewer than 3% of global isolates lacking a glycan site at this position. However, at least one conserved glycan site is missing in 89% of viruses, suggesting the presence of glycan holes in most HIV isolates. Serum evidence is consistent with targeting of holes in natural infection. The immunogenic nature of breaches in the glycan shield has been under-appreciated in previous attempts to understand autologous neutralizing antibody responses and has important potential consequences for HIV vaccine design.
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http://dx.doi.org/10.1016/j.celrep.2016.07.074DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5007210PMC
August 2016

HIV-1 broadly neutralizing antibody precursor B cells revealed by germline-targeting immunogen.

Science 2016 Mar;351(6280):1458-63

Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA 92037, USA. IAVI Neutralizing Antibody Center, The Scripps Research Institute, La Jolla, CA 92037, USA. Center for HIV/AIDS Vaccine Immunology and Immunogen Discovery, The Scripps Research Institute, La Jolla, CA 92037, USA. Ragon Institute of MGH, MIT, and Harvard, Cambridge, MA 02129, USA.

Induction of broadly neutralizing antibodies (bnAbs) is a major HIV vaccine goal. Germline-targeting immunogens aim to initiate bnAb induction by activating bnAb germline precursor B cells. Critical unmet challenges are to determine whether bnAb precursor naïve B cells bind germline-targeting immunogens and occur at sufficient frequency in humans for reliable vaccine responses. Using deep mutational scanning and multitarget optimization, we developed a germline-targeting immunogen (eOD-GT8) for diverse VRC01-class bnAbs. We then used the immunogen to isolate VRC01-class precursor naïve B cells from HIV-uninfected donors. Frequencies of true VRC01-class precursors, their structures, and their eOD-GT8 affinities support this immunogen as a candidate human vaccine prime. These methods could be applied to germline targeting for other classes of HIV bnAbs and for Abs to other pathogens.
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http://dx.doi.org/10.1126/science.aad9195DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4872700PMC
March 2016

Glycan clustering stabilizes the mannose patch of HIV-1 and preserves vulnerability to broadly neutralizing antibodies.

Nat Commun 2015 Jun 24;6:7479. Epub 2015 Jun 24.

Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.

The envelope spike of HIV-1 employs a 'glycan shield' to protect itself from antibody-mediated neutralization. Paradoxically, however, potent broadly neutralizing antibodies (bnAbs) that target this shield have been isolated. The unusually high glycan density on the gp120 subunit limits processing during biosynthesis, leaving a region of under-processed oligomannose-type structures, which is a primary target of these bnAbs. Here we investigate the contribution of individual glycosylation sites in the formation of this so-called intrinsic mannose patch. Deletion of individual sites has a limited effect on the overall size of the intrinsic mannose patch but leads to changes in the processing of neighbouring glycans. These structural changes are largely tolerated by a panel of glycan-dependent bnAbs targeting these regions, indicating a degree of plasticity in their recognition. These results support the intrinsic mannose patch as a stable target for vaccine design.
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http://dx.doi.org/10.1038/ncomms8479DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4500839PMC
June 2015

Immunization for HIV-1 Broadly Neutralizing Antibodies in Human Ig Knockin Mice.

Cell 2015 Jun;161(7):1505-15

Laboratory of Molecular Immunology, The Rockefeller University, New York, NY 10065, USA; Howard Hughes Medical Institute. Electronic address:

A subset of individuals infected with HIV-1 develops broadly neutralizing antibodies (bNAbs) that can prevent infection, but it has not yet been possible to elicit these antibodies by immunization. To systematically explore how immunization might be tailored to produce them, we generated mice expressing the predicted germline or mature heavy chains of a potent bNAb to the CD4 binding site (CD4bs) on the HIV-1 envelope glycoprotein (Env). Immunogens specifically designed to activate B cells bearing germline antibodies are required to initiate immune responses, but they do not elicit bNAbs. In contrast, native-like Env trimers fail to activate B cells expressing germline antibodies but elicit bNAbs by selecting for a restricted group of light chains bearing specific somatic mutations that enhance neutralizing activity. The data suggest that vaccination to elicit anti-HIV-1 antibodies will require immunization with a succession of related immunogens.
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http://dx.doi.org/10.1016/j.cell.2015.06.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4604566PMC
June 2015