Title & Authors Journal Publication Date

Affinity-matured homotypic interactions induce spectrum of PfCSP structures that influence protection from malaria infection

Martin GM, Torres JL, Pholcharee T, Oyen D, Flores-Garcia Y, Gibson G, Moskovitz R, Beutler N, Jung DD, Copps J, Lee WH, Gonzalez-Paez G, Emerling D, MacGill RS, Locke E, King CR, Zavala F, Wilson IA, Ward AB.
Nature Communications July 28, 2023

The generation of high-quality antibody responses to Plasmodium falciparum (Pf) circumsporozoite protein (PfCSP), the primary surface antigen of Pf sporozoites, is paramount to the development of an effective malaria vaccine. Here we present an in-depth structural and functional analysis of a panel of potent antibodies encoded by the immunoglobulin heavy chain variable (IGHV) gene IGHV3-33, which is among the most prevalent and potent antibody families induced in the anti-PfCSP immune response and targets the Asn-Ala-Asn-Pro (NANP) repeat region. Cryo-electron microscopy (cryo-EM) reveals a remarkable spectrum of helical antibody-PfCSP structures stabilized by homotypic interactions between tightly packed fragments antigen binding (Fabs), many of which correlate with somatic hypermutation. We demonstrate a key role of these mutated homotypic contacts for high avidity binding to PfCSP and in protection from Pf malaria infection. Together, these data emphasize the importance of anti-homotypic affinity maturation in the frequent selection of IGHV3–33 antibodies and highlight key features underlying the potent protection of this antibody family. Here, the authors use cryo-EM to solve the structures of seven potent human antibodies, and demonstrate in vivo protection in a liver burden assay, using chimeric Plasmodium berghei sporozoites expressing Plasmodium falciparum circumsporozoite protein.

Protocol for analyzing antibody responses to glycoprotein antigens using electron-microscopy-based polyclonal epitope mapping

Turner HL, Jackson AM, Richey ST, Sewall LM, Antanasijevic A, Hangartner L, Ward AB.
STAR Protocols July 28, 2023

Electron microscopy-based polyclonal epitope mapping (EMPEM) can delineate epitope specificities of serum antibodies to a given antigen following vaccination or infection. Here, we present a protocol for the EMPEM method for rapid high-throughput assessment of antibody responses to glycoprotein antigens in vaccination and infection studies. We describe steps for antibody isolation and digestion, antigen complex and purification, and electron microscope imaging. We then detail procedures for processing and analysis of EMPEM data. For complete details on the use and execution of this protocol, please refer to Bianchi et al. (2018). 1

Human antibodies that neutralize respiratory droplet transmissible H5N1 influenza viruses

Thornburg NJ, Nannemann DP, Blum DL, Belser JA, Tumpey TM, Deshpande S, Fritz GA, Sapparapu G, Krause JC, Lee JH, Ward AB, Lee DE, Li S, Winarski KL, Spiller BW, Meiler J, Crowe JE Jr
Journal of Clinical Investigation July 25, 2023

Recent studies described the experimental adaptation of influenza H5 HAs that confers respiratory droplet transmission (rdt) to influenza virus in ferrets. Acquisition of the ability to transmit via aerosol may lead to the development of a highly pathogenic pandemic H5 virus. Vaccines are predicted to play an important role in H5N1 control should the virus become readily transmissible between humans. We obtained PBMCs from patients who received an A/Vietnam/1203/2004 H5N1 subunit vaccine. Human hybridomas were then generated and characterized. We identified antibodies that bound the HA head domain and recognized both WT and rdt H5 HAs. We used a combination of structural techniques to define a mechanism of antibody recognition of an H5 HA receptor–binding site that neutralized H5N1 influenza viruses and pseudoviruses carrying the HA rdt variants that have mutations near the receptor-binding site. Incorporation or retention of this critical antigenic site should be considered in the design of novel H5 HA immunogens to protect against mammalian-adapted H5N1 mutants.

Profound structural conservation of chemically cross-linked HIV-1 envelope glycoprotein experimental vaccine antigens

Martin GM, Russell RA, Mundsperger P, Harris S, Jovanoska L, Trajano LF, Schiffner T, Fabian K, Tolazzi M, Scarlatti G, McFarlane L, Cheeseman H, Aldon Y, Schermer EE, Breemen M, Sliepen K, Katinger D, Kunert R, Sanders RW, Shattock R, Ward AB, Sattentau QJ.
npj Vaccines July 13, 2023

Chemical cross-linking is used to stabilize protein structures with additional benefits of pathogen and toxin inactivation for vaccine use, but its use has been restricted by the potential for local or global structural distortion. This is of particular importance when the protein in question requires a high degree of structural conservation for inducing a biological outcome such as the elicitation of antibodies to conformationally sensitive epitopes. The HIV-1 envelope glycoprotein (Env) trimer is metastable and shifts between different conformational states, complicating its use as a vaccine antigen. Here we have used the hetero-bifunctional zero-length reagent 1-Ethyl-3-(3-Dimethylaminopropyl)-Carbodiimide (EDC) to cross-link two soluble Env trimers, selected well-folded trimer species using antibody affinity, and transferred this process to good manufacturing practice (GMP) for experimental medicine use. Cross-linking enhanced trimer stability to biophysical and enzyme attack. Cryo-EM analysis revealed that cross-linking retained the overall structure with root-mean-square deviations (RMSDs) between unmodified and cross-linked Env trimers of 0.4–0.5 Å. Despite this negligible distortion of global trimer structure, we identified individual inter-subunit, intra-subunit, and intra-protomer cross-links. Antigenicity and immunogenicity of the trimers were selectively modified by cross-linking, with cross-linked ConS retaining bnAb binding more consistently than ConM. Thus, the EDC cross-linking process improves trimer stability whilst maintaining protein folding, and is readily transferred to GMP, consistent with the more general use of this approach in protein-based vaccine design.

Induction of cross-neutralizing antibodies by a permuted hepatitis C virus glycoprotein nanoparticle vaccine candidate

Sliepen K, Radi? L, Capella-Pujol J, Watanabe Y, Zon I, Chumbe A, Lee WH, de Gast M, Koopsen J, Koekkoek S, Del Moral-Sánchez I, Brouwer PJM, Ravichandran R, Ozorowski G, King NP, Ward AB, van Gils MJ, Crispin M, Schinkel J, Sanders RW.
Nature Communications June 26, 2023

Hepatitis C virus (HCV) infection affects approximately 58 million people and causes ~300,000 deaths yearly. The only target for HCV neutralizing antibodies is the highly sequence diverse E1E2 glycoprotein. Eliciting broadly neutralizing antibodies that recognize conserved cross-neutralizing epitopes is important for an effective HCV vaccine. However, most recombinant HCV glycoprotein vaccines, which usually include only E2, induce only weak neutralizing antibody responses. Here, we describe recombinant soluble E1E2 immunogens that were generated by permutation of the E1 and E2 subunits. We displayed the E2E1 immunogens on two-component nanoparticles and these nanoparticles induce significantly more potent neutralizing antibody responses than E2. Next, we generated mosaic nanoparticles co-displaying six different E2E1 immunogens. These mosaic E2E1 nanoparticles elicit significantly improved neutralization compared to monovalent E2E1 nanoparticles. These results provide a roadmap for the generation of an HCV vaccine that induces potent and broad neutralization. E1E2 spike on the hepatitis C virion is an important target for vaccine design. Here, the authors permute the subunits to generate E2E1 immunogens and show that mosaic nanoparticles displaying different E2E1 antigens elicit cross-neutralizing antibodies in rabbits.

Fusion of the molecular adjuvant C3d to cleavage-independent native-like HIV-1 Env trimers improves the elicited antibody response

Bale S, Yang L, Alirezaei M, Wilson R, Ota T, Doyle ED, Cottrell CA, Guenaga J, Tran K, Li W, Stamatatos L, Nemazee D, Ward AB, Wyatt RT.
Frontiers in Immunology June 6, 2023

An effective HIV vaccine likely requires the elicitation of neutralizing antibodies (NAbs) against multiple HIV-1 clades. The recently developed cleavage-independent native flexibly linked (NFL) envelope (Env) trimers exhibit well-ordered conformation and elicit autologous tier 2 NAbs in multiple animal models. Here, we investigated whether the fusion of molecular adjuvant C3d to the Env trimers can improve B- cell germinal center (GC) formation and antibody responses. To generate Env-C3d trimers, we performed a glycine-serine- based (G4S) flexible peptide linker screening and identified a linker range that allowed native folding. A 30–60- amino- acid- long linker facilitates Env-to-C3d association and achieves the secretion of well-ordered trimers and the structural integrity and functional integrity of Env and C3d. The fusion of C3d did not dramatically affect the antigenicity of the Env trimers and enhanced the ability of the Env trimers to engage and activate B cells in vitro. In mice, the fusion of C3d enhanced germinal center formation, the magnitude of Env-specific binding antibodies, and the avidity of the antibodies in the presence of an adjuvant. The Sigma Adjuvant System (SAS) did not affect the trimer integrity in vitro but contributed to altered immunogenicity in vivo, resulting in increased tier 1 neutralization, likely by increased exposure of variable region 3 (V3). Taken together, the results indicate that the fusion of the molecular adjuvant, C3d, to the Env trimers improves antibody responses and could be useful for Env-based vaccines against HIV.

Fusion peptide of HIV-1 as a site of vulnerability to neutralizing antibody

Kong R, Xu K, Zhou T, Acharya P, Lemmin T, Liu K, Ozorowski G, Soto C, Taft JD, Bailer RT, Cale EM, Chen L, Choi CW, Chuang GY, Doria-Rose NA, Druz A, Georgiev IS, Gorman J, Huang J, Joyce MG, Louder MK, Ma X, McKee K, O'Dell S, Pancera M, Yang Y, Blanchard SC, Mothes W, Burton DR, Koff WC, Connors M, Ward AB, Kwong PD, Mascola JR
Science May 31, 2023

The HIV-1 fusion peptide, comprising 15 to 20 hydrophobic residues at the N terminus of the Env-gp41 subunit, is a critical component of the virus-cell entry machinery. Here, we report the identification of a neutralizing antibody, N123-VRC34.01, which targets the fusion peptide and blocks viral entry by inhibiting conformational changes in gp120 and gp41 subunits of Env required for entry. Crystal structures of N123-VRC34.01 liganded to the fusion peptide, and to the full Env trimer, revealed an epitope consisting of the N-terminal eight residues of the gp41 fusion peptide and glycan N88 of gp120, and molecular dynamics showed that the N-terminal portion of the fusion peptide can be solvent-exposed. These results reveal the fusion peptide to be a neutralizing antibody epitope and thus a target for vaccine design.

Conformational Plasticity in the HIV-1 Fusion Peptide Facilitates Recognition by Broadly Neutralizing Antibodies

Yuan M, Cottrell CA, Ozorowski G, van Gils MJ, Kumar S, Wu NC, Sarkar A, Torres JL, de Val N, Copps J, Moore JP, Sanders RW, Ward AB, Wilson IA.
Cell Host & Microbe May 27, 2023

The fusion peptide (FP) of HIV-1 envelope glycoprotein (Env) is essential for mediating viral entry. Detection of broadly neutralizing antibodies (bnAbs) that interact with the FP has revealed it as a site of vulnerability. We delineate X-ray and cryo-electron microscopy (cryo-EM) structures of bnAb ACS202, from an HIV-infected elite neutralizer, with an FP and with a soluble Env trimer (AMC011 SOSIP.v4.2) derived from the same patient. We show that ACS202 CDRH3 forms a “β strand” interaction with the exposed hydrophobic FP and recognizes a continuous region of gp120, including a conserved N-linked glycan at N88. A cryo-EM structure of another previously identified bnAb VRC34.01 with AMC011 SOSIP.v4.2 shows that it also penetrates through glycans to target the FP. We further demonstrate that the FP can twist and present different conformations for recognition by bnAbs, which enables approach to Env from diverse angles. The variable recognition of FP by bnAbs thus provides insights for vaccine design.

Structural conservation of Lassa virus glycoproteins and recognition by neutralizing antibodies

Perrett HR, Brouwer PJM, Hurtado J, Newby ML, Liu L, Müller-Kräuter H, Müller Aguirre S, Burger JA, Bouhuijs JH, Gibson G, Messmer T, Schieffelin JS, Antanasijevic A, Boons GJ, Strecker T, Crispin M, Sanders RW, Briney B, Ward AB.
Cell Reports May 18, 2023

Lassa fever is an acute hemorrhagic fever caused by the zoonotic Lassa virus (LASV). The LASV glycoprotein complex (GPC) mediates viral entry and is the sole target for neutralizing antibodies. Immunogen design is complicated by the metastable nature of recombinant GPCs and the antigenic differences among phylogenetically distinct LASV lineages. Despite the sequence diversity of the GPC, structures of most lineages are lacking. We present the development and characterization of prefusion-stabilized, trimeric GPCs of LASV lineages II, V, and VII, revealing structural conservation despite sequence diversity. High-resolution structures and biophysical characterization of the GPC in complex with GP1-A-specific antibodies suggest their neutralization mechanisms. Finally, we present the isolation and characterization of a trimer-preferring neutralizing antibody belonging to the GPC-B competition group with an epitope that spans adjacent protomers and includes the fusion peptide. Our work provides molecular detail information on LASV antigenic diversity and will guide efforts to design pan-LASV vaccines.

Structural basis of epitope selectivity and potent protection from malaria by PfCSP antibody L9

Martin GM, Fernández-Quintero ML, Lee WH, Pholcharee T, Eshun-Wilson L, Liedl KR, Pancera M, Seder RA, Wilson IA, Ward AB.
Nature Communications May 17, 2023

A primary objective in malaria vaccine design is the generation of high-quality antibody responses against the circumsporozoite protein of the malaria parasite, Plasmodium falciparum (PfCSP). To enable rational antigen design, we solved a cryo-EM structure of the highly potent anti-PfCSP antibody L9 in complex with recombinant PfCSP. We found that L9 Fab binds multivalently to the minor (NPNV) repeat domain, which is stabilized by a unique set of affinity-matured homotypic, antibody-antibody contacts. Molecular dynamics simulations revealed a critical role of the L9 light chain in integrity of the homotypic interface, which likely impacts PfCSP affinity and protective efficacy. These findings reveal the molecular mechanism of the unique NPNV selectivity of L9 and emphasize the importance of anti-homotypic affinity maturation in protective immunity against P. falciparum. The cryo-EM structure of the highly potent malaria antibody L9 reveals a key role of light-chain derived homotypic interactions in antigen binding and parasite inhibition, enabling antibody engineering and next-generation malaria vaccine design.

Structural insights into the broad protection against H1 influenza viruses by a computationally optimized hemagglutinin vaccine

Dzimianski JV, Han J, Sautto GA, O'Rourke SM, Cruz JM, Pierce SR, Ecker JW, Carlock MA, Nagashima KA, Mousa JJ, Ross TM, Ward AB, DuBois RM.
Communications Biology April 25, 2023

Influenza virus poses an ongoing human health threat with pandemic potential. Due to mutations in circulating strains, formulating effective vaccines remains a challenge. The use of computationally optimized broadly reactive antigen (COBRA) hemagglutinin (HA) proteins is a promising vaccine strategy to protect against a wide range of current and future influenza viruses. Though effective in preclinical studies, the mechanistic basis driving the broad reactivity of COBRA proteins remains to be elucidated. Here, we report the crystal structure of the COBRA HA termed P1 and identify antigenic and glycosylation properties that contribute to its immunogenicity. We further report the cryo-EM structure of the P1-elicited broadly neutralizing antibody 1F8 bound to COBRA P1, revealing 1F8 to recognize an atypical receptor binding site epitope via an unexpected mode of binding. Structural studies of a computationally optimized broadly reactive antigen hemagglutinin in complex with a broadly neutralizing antibody reveal its immunogenic properties and provide insights into flu vaccine design.

Bispecific antibodies targeting distinct regions of the spike protein potently neutralize SARS-CoV-2 variants of concern

Cho H, Gonzales-Wartz KK, Huang D, Yuan M, Peterson M, Liang J, Beutler N, Torres JL, Cong Y, Postnikova E, Bangaru S, Talana CA, Shi W, Yang ES, Zhang Y, Leung K, Wang L, Peng L, Skinner J, Li S, Wu NC, Liu H, Dacon C, Moyer T, Cohen M, Zhao M, Lee FE, Weinberg RS, Douagi I, Gross R, Schmaljohn C, Pegu A, Mascola JR, Holbrook M, Nemazee D, Rogers TF, Ward AB, Wilson IA, Crompton PD, Tan J.
Science Translational Medicine April 21, 2023

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern threatens the efficacy of existing vaccines and therapeutic antibodies and underscores the need for additional antibody-based tools that potently neutralize variants by targeting multiple sites of the spike protein. We isolated 216 monoclonal antibodies targeting SARS-CoV-2 from plasmablasts and memory B cells collected from patients with coronavirus disease 2019. The three most potent antibodies targeted distinct regions of the receptor-binding domain (RBD), and all three neutralized the SARS-CoV-2 Alpha and Beta variants. The crystal structure of the most potent antibody, CV503, revealed that it binds to the ridge region of SARS-CoV-2 RBD, competes with the angiotensin converting enzyme 2 receptor, and has limited contact with key variant residues K417, E484 and N501. We designed bispecific antibodies by combining non-overlapping specificities and identified five bispecific antibodies that inhibit SARS-CoV-2 infection at concentrations of less than 1 ng/mL. Through a distinct mode of action, three bispecific antibodies cross-linked adjacent spike proteins using dual N-terminal domain-RBD specificities. One bispecific antibody was greater than 100-fold more potent than a cocktail of its parent monoclonals in vitro and prevented clinical disease in a hamster model at a 2.5 mg/kg dose. Notably, two bispecific antibodies in our panel comparably neutralized the Alpha, Beta, Gamma and Delta variants and wild-type virus. Furthermore, a bispecific antibody that neutralized the Beta variant protected hamsters against SARS-CoV-2 expressing the E484K mutation. Thus, bispecific antibodies represent a promising next-generation countermeasure against SARS-CoV-2 variants of concern.

Single-component multilayered self-assembling protein nanoparticles presenting glycan-trimmed uncleaved prefusion optimized envelope trimmers as HIV-1 vaccine candidates

Zhang YN, Paynter J, Antanasijevic A, Allen JD, Eldad M, Lee YZ, Copps J, Newby ML, He L, Chavez D, Frost P, Goodroe A, Dutton J, Lanford R, Chen C, Wilson IA, Crispin M, Ward AB, Zhu J.
Nature Communications April 8, 2023

Uncleaved prefusion-optimized (UFO) design can stabilize diverse HIV-1 envelope glycoproteins (Envs). Single-component, self-assembling protein nanoparticles (1c-SApNP) can display 8 or 20 native-like Env trimers as vaccine candidates. We characterize the biophysical, structural, and antigenic properties of 1c-SApNPs that present the BG505 UFO trimer with wildtype and modified glycans. For 1c-SApNPs, glycan trimming improves recognition of the CD4 binding site without affecting broadly neutralizing antibodies (bNAbs) to major glycan epitopes. In mice, rabbits, and nonhuman primates, glycan trimming increases the frequency of vaccine responders (FVR) and steers antibody responses away from immunodominant glycan holes and glycan patches. The mechanism of vaccine-induced immunity is examined in mice. Compared with the UFO trimer, the multilayered E2p and I3-01v9 1c-SApNPs show 420 times longer retention in lymph node follicles, 20-32 times greater presentation on follicular dendritic cell dendrites, and up-to-4 times stronger germinal center reactions. These findings can inform future HIV-1 vaccine development. Here the authors present an HIV-1 vaccine strategy that combines Env stabilization, nanoparticle display, and glycan trimming, which improves neutralizing antibody responses, frequency of vaccine responders, and germinal center reactions in animal models.

Title & Authors Journal Publication Date

Immune memory shapes human polyclonal antibody responses to H2N2 vaccination

Yang YR, Han J, Perrett HR, Richey ST, Jackson AM, Rodriguez AJ, Gillespie RA, O’Connell S, Raab JE, Cominsky LY, Chopde A, Kanekiyo M, Houser KV, Chen GL, McDermott AB, Andrews SF, Ward AB

bioRxiv Aug. 23, 2023

Glycan heterogeneity as a cause of the persistent fraction in HIV-1 neutralization

Ringe RP, Colin P, Ozorowski G, Allen JD, Yasmeen A, Seabright GE, Lee JH, Antanasijevic A, Rantalainen K, Ketas T, Moore JP, Ward AB, Crispin M, Klasse PJ

Now Published: 10.1371/journal.ppat.1011601
bioRxiv Aug. 8, 2023

Focusing antibody responses to the fusion peptide in rhesus macaques

Cottrell CA, Pratap PP, Cirelli KM, Carnathan DG, Enemuo CA, Antanasijevic A, Ozorowski G, Sewall LM, Gao H, Greene KM, Allen JD, Ngo JT, Choe Y, Nogal B, Silva M, Bhiman J, Pauthner M, Irvine DJ, Montefiori D, Crispin M, Burton DR, Silvestri G, Crotty S, Ward AB

bioRxiv June 26, 2023

Structure of mechanically activated ion channel OSCA2.3 reveals mobile elements in the transmembrane domain

Jojoa-Cruz S, Burendei B, Lee WH, Ward AB

Now Published: 10.1016/j.str.2023.11.009
bioRxiv June 15, 2023

Evolving spike-protein N -glycosylation in SARS-CoV-2 variants

Baboo S, Diedrich JK, Torres JL, Copps J, Singh B, Garrett PT, Ward AB, Paulson JC, Yates JR

bioRxiv May 8, 2023

Ab initio prediction of specific phospholipid complexes and membrane association of HIV-1 MPER antibodies by multi-scale simulations

Maillie C, Golden J, Wilson IA, Ward AB, Mravic M

bioRxiv May 4, 2023

Broadly neutralizing antibodies targeting a conserved silent face of spike RBD resist extreme SARS-CoV-2 antigenic drift

Song G, Yuan M, Liu H, Capozzola T, Lin RN, Torres JL, He WT, Musharrafieh R, Dueker K, Zhou P, Callaghan S, Mishra N, Yong P, Anzanello F, Avillion G, Lina Vo A, Li X, Makhdoomi M, Feng Z, Zhu X, Peng L, Nemazee D, Safonova Y, Briney B, Ward AB, Burton DR, Wilson IA, Andrabi R

bioRxiv April 26, 2023