Biology subjects

Callaghan, S.

Publications and source records attributed to Callaghan, S..

At least 19 recordsLinked to original sources

bioRxiv2026

Protective pan-betacoronavirus neutralizing antibodies by vaccination

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 SUMMARYEpitope-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.

immunology↗

bioRxiv2026

Early clonal dominance at priming sets the trajectory for broad HIV serum neutralization

Inducing broadly neutralizing antibodies (bnAbs) remains a central challenge in HIV vaccine development 1-3. Germline-targeting immunogens are designed to activate rare bnAb precursor B cell lineages 4-12, yet the relationships between priming efficiency, clonal dominance, and downstream serum neutralization remain poorly defined. We recently demonstrated that vaccination with an engineered V2-apex germline-targeting trimer Q23-APEX-GT2 successfully recruits and activates rare long-CDRH3 B cell precursors in outbred macaques 13. Here, we dissect the immunological mechanisms governing bnAb precursor priming and early B cell expansion and define clonal features that drive progression to serum neutralization breadth. Our antigen-specific B cell analyses showed that Q23-APEX-GT2 consistently engaged long-CDRH3 precursors, although priming efficiency varied across animals. Longitudinal deep lineage tracing across lymph node and blood compartments revealed that early recruitment of multiple diverse long-CDRH3 lineages, followed by preferential expansion and dominance of one or two clones, strongly predicted serum neutralization potency. Subsequent CAP256.SU SHIV infection efficiently recalled vaccine-seeded clones, accelerated affinity maturation, and drove broad heterologous neutralization in most animals. Notably, one macaque with diverse and expanded V2-apex lineages rapidly achieved [~]70% serum neutralization breadth. Importantly, longitudinal tracing revealed that bona fide bnAbs can emerge from vaccine-primed precursors, while also uncovering "born-wrong" bnAb-like lineages that expand yet remain non-neutralizing, despite structurally validated recognition of the V2-apex bnAb site. Together, these findings establish priming efficiency coupled with early clonal dominance as key determinants of serum bnAb induction and provide a mechanistic framework to guide rational HIV vaccine design.

immunology↗

bioRxiv2026

Heterologous betacoronavirus spike immunization in nonhuman primates elicits cross-reactive antibodies that neutralize both sarbeco- and merbecoviruses

In anticipation of future coronavirus (CoV) pandemics, developing vaccines that elicit broadly neutralizing antibodies (bnAbs) against diverse CoVs is critical. Here, we vaccinated rhesus macaques with SARS-CoV-2 spike (S)-protein, then boosted with heterologous {beta}-CoV S-proteins to focus responses to common conserved S2 bnAb epitopes. Initial SARS-CoV-2 priming elicited receptor-binding domain (RBD)-focused responses, while MERS-CoV boosting redirected responses toward the S2 region, including the stem-helix bnAb site. Although S2-directed serum cross-neutralization was undetectable and most isolated cross-reactive monoclonal antibodies (mAbs) targeted non-neutralizing epitopes, two S2 stem-helix mAbs were identified from memory B cells. These bnAbs neutralized diverse sarbeco- and merbecoviruses, including MERS-CoV, and conferred robust in vivo protection against SARS-CoV-2 challenge. Structural studies revealed that these macaque bnAbs closely mimic human S2-stem bnAbs induced by infection. These findings provide proof-of-principle for vaccination strategies that elicit broadly protective {beta}-coronavirus responses and highlight non-human primates as a translational model for evaluating S2-targeted immunogens.

immunology↗

bioRxiv2025

Structure-guided design of native-like HIV Env Single Chain Trimers for enhanced stability, immunogenicity, and versatile vaccine delivery

Stabilizing the HIV envelope (Env) trimer in its native prefusion conformation is key to eliciting broadly neutralizing antibodies (bnAbs). We present a generalizable single-chain trimer-(SCT) design platform that enables the production of stable, native-like Env trimers across diverse HIV strains. Using a structure-guided approach, we developed CAP256.SU-SCT9, based on a CAP256.SU Env shown to induce V2-apex bnAbs in humans and rhesus macaques. CAP256.SU-SCT9 trimer exhibited native-like structure, bnAb-specific antigenicity, authentic glycosylation, and compatibility with nucleic acid and nanoparticle delivery. We extended this design strategy to a panel of HIV Envs representing global diversity, and immunogens known to initiate bnAb responses in humans. Structural analyses confirmed that SCTs consistently maintained prefusion-closed conformations, favorable glycan profiles, strong binding to trimer-specific bnAbs, and low reactivity with non-neutralizing antibodies. These findings establish SCT as a versatile platform for HIV trimer immunogen design, with potential to support next-generation vaccines aimed at eliciting protective bnAb responses.

immunology↗

bioRxiv2025

Germline-targeting HIV immunogen induces cross-neutralizing antibodies in outbred macaques

Germline-targeting-(GT) is a promising strategy to activate rare broadly neutralizing antibody (bnAb)-producing B cells against HIV, but induction of such responses in outbred animals has not been achieved. Using antibody-guided structure-based design, we engineered a germline-targeting trimer immunogen Q23-APEX-GT2 that primes diverse V2-apex bnAb precursors. Q23-APEX-GT2 efficiently activated V2-apex-specific B cells in humanized knock-in mice and consistently elicited immunofocused antibody responses in rhesus macaques, priming multiple long CDRH3-loop bnAb-B cell lineages. Monoclonal antibodies from immunized macaques exhibited broad heterologous HIV trimer binding and cross-neutralization. Atomic-level structural studies confirmed precise epitope targeting and revealed CDRH3-paratope configurations that mirrored those of human V2-apex bnAbs. This study provides proof-of-principle for successful priming and maturation of authentic V2-apex bnAb precursors in outbred macaques, underscoring the potential of V2-apex-targeted vaccines. HIGHLIGHTSO_LIEngineered Q23-APEX-GT2 trimer to stimulate diverse V2-apex bnAb B cell precursors C_LIO_LIQ23-APEX-GT2 primed rare V2-apex bnAb B cells in mice and outbred rhesus macaques C_LIO_LIQ23-APEX-GT2 elicited immunofocused antibody responses and diverse V2-apex B cell lineages with desirable long-CDRH3 paratope properties C_LIO_LIQ23-APEX-GT2 alone induced V2-apex antibodies with broad HIV trimer binding and modest neutralization breadth C_LIO_LIStructural analysis confirmed bnAb site targeting, mirroring human and rhesus V2-apex bnAbs C_LI

immunology↗

bioRxiv2025

Directed evolution of a stem-helix targeting antibody enables MERS-CoV cross-neutralization through enhanced binding affinity

Broadly neutralizing antibodies (bnAbs) targeting conserved regions of the betacoronavirus spike are important for pan-betacoronavirus protection and pandemic preparedness. Here, we report on the isolation of a human monoclonal antibody, CC65.1, from a SARS-CoV-2 convalescent donor that targets the conserved S2 stem helix region. CC65.1 neutralizes various sarbecoviruses, including SARS-CoV-2, and binds the MERS-CoV spike but lacks MERS-CoV-neutralizing activity due to insufficient binding affinity. We utilized directed evolution to enhance the binding affinity of CC65.1 for the MERS-CoV S2 stem helix, yielding engineered antibody variants with newly acquired MERS-CoV-neutralizing activity. High-resolution structural analysis reveals key paratope mutations that optimize binding and stabilize epitope engagement. Our findings demonstrate the potential of rational antibody engineering to expand bnAb breadth across divergent betacoronaviruses. This work supports the development of engineered bnAbs and S2-targeted vaccines for broad betacoronavirus countermeasures and highlights strategies to achieve cross-lineage immunity for future pandemic threats. Author SummaryThe persistent emergence of new SARS-CoV-2 variants of concern that evade neutralizing antibody responses and other zoonotic betacoronaviruses with pandemic potential have provided strong motivation to develop broadly neutralizing antibodies (bnAbs) that target more conserved regions of the spike protein in sarbecoviruses and other betacoronaviruses. Here, we employed a directed evolution strategy to engineer the sarbecovirus-neutralizing antibody CC65.1, which targets the conserved S2 stem helix, to enhance its binding affinity with the MERS-CoV stem helix region, thereby conferring MERS-CoV neutralization. High-resolution structural studies of engineered CC65.1 revealed that key mutations reshape the paratope to better accommodate and stabilize the MERS-CoV S2 stem helix, resulting in increased binding affinity and neutralization potency. This study emphasizes the critical role of affinity maturation in expanding neutralization breadth and provides valuable insights for design of bnAbs to prevent and treat pandemic threats by betacoronaviruses.

immunology↗

bioRxiv2025

Rapid acquisition of HIV-1 neutralization breadth in a rhesus V2 apex germline antibody mouse model after a single bolus immunization

Current vaccine strategies to elicit broadly neutralizing antibodies (bnAbs) against HIV-1 generally propose complex, multi-boost immunization regimens. In rhesus macaques, SHIV infection has been observed to rapidly drive the development of some classes of bnAbs that share structural similarities with those in humans. Here, we generated a knockin mouse model with B cells bearing the unmutated common ancestor (UCA) of the V2 apex-targeted bnAb lineage, V033-a. A single immunization of mice with a germline-targeting native-like trimer was sufficient to recapitulate the ontogeny of the mature rhesus bnAb in knockin mice--including rare, disfavored somatic mutations--leading to the induction of antibodies that exhibited potent neutralization against both autologous and heterologous tier 2 viruses. A boost with Env escape mutant trimers further improved breadth and potency, and cryo-EM structure revealed the structural basis for heterologous neutralization breadth. Non-human primate and mouse models can thus combine with structure to serve as a platform for identifying and confirming immunogens that streamline HIV-vaccination regimens.

immunology↗

bioRxiv2024

Conformational ensemble-based framework enables rapid development of Lassa virus vaccine candidates

Lassa virus (LASV), an arenavirus endemic to West Africa, poses a significant public health threat due to its high pathogenicity and expanding geographic risk zone. LASV glycoprotein complex (GPC) is the only known target of neutralizing antibodies, but its inherent metastability and conformational flexibility have hindered the development of GPC-based vaccines. We employed a variant of AlphaFold2 (AF2), called subsampled AF2, to generate diverse structures of LASV GPC that capture an array of potential conformational states using MSA subsampling and dropout layers. Conformational ensembles identified several metamorphic domains--areas of significant conformational flexibility--that could be targeted to stabilize the GPC in its immunogenic prefusion state. ProteinMPNN was then used to redesign GPC sequences to minimize the mobility of metamorphic domains. These redesigned sequences were further filtered using subsampled AF2, leading to the identification of promising GPC variants for further testing. A small library of redesigned GPC sequences was experimentally validated and showed significantly increased protein yields compared to controls. Antigenic profiles indicated these variants preserved essential epitopes for effective immune response, suggesting their potential for broad protective efficacy. Our results demonstrate that AI-driven approaches can predict the conformational landscape of complex pathogens. This knowledge can be used to stabilize viral proteins, such as LASV GPC, in their prefusion conformation, optimizing them for stability and expression, and offering a streamlined framework for vaccine design. Our deep learning / machine learning enabled framework contributes to global efforts to combat LASV and has broader implications for vaccine design and pandemic preparedness.

immunology↗

bioRxiv2024

Decoding protein dynamicity in DNA ligase activity through deep learning-based structural ensembles

Numerous proteins perform their functions by transitioning between various structures. Understanding the conformational ensembles associated with these states is essential for uncovering crucial mechanistic aspects that regulate protein function. In this study, we utilized AlphaFold3 (AF3) to investigate the structural dynamics and mechanisms of enzymes involved in DNA homeostasis, using NAD-dependent Taq ligases and human DNA Ligase 1 as a case example. Modifying the input parameters for AF3 yielded detailed conformational states of a DNA-binding enzyme, thereby offering enhanced mechanistic insights. We applied AF3 to model the various stages of thermophilic Taq DNA ligase activity, from its ground state to substrate-bound complexes, revealing significant mobility in the N-terminal adenylation and C-terminal BRCT domains. These detailed structural ensembles provided novel insights into the enzymes behavior during DNA repair, underscoring the potential of AF3 in elucidating mechanistic details critical for therapeutic and biotechnological targeting. Extending this approach to human LIG1, we examined its end-joining activity on double-strand breaks (DSBs) with short 3 and 5 overhangs. In alignment with published experimental data, AF3 conformational ensembles indicated LIG1 has lower catalytic efficiency for 5 overhangs due to suboptimal DNA positioning within the catalytic site, demonstrating AF3s capability to capture subtle yet functionally significant conformational differences by generating conformational ensembles capturing greater structural variance.

molecular biology↗

bioRxiv2024

HIV-1 neutralizing antibodies in SHIV-infected macaques recapitulate structurally divergent modes of human V2 apex recognition with a single D gene

Broadly neutralizing antibodies targeting the V2 apex of the HIV-1 envelope trimer are among the most common specificities elicited in HIV-1-infected humans and simian-human immunodeficiency virus (SHIV)-infected macaques. To gain insight into the prevalent induction of these antibodies, we isolated and characterized 11 V2 apex-directed neutralizing antibody lineages from SHIV-infected rhesus macaques. Remarkably, all SHIV-induced V2 apex lineages were derived from reading frame two of the rhesus DH3-15*01 gene. Cryo-EM structures of envelope trimers in complex with antibodies from nine rhesus lineages revealed modes of recognition that mimicked three canonical human V2 apex-recognition modes. Notably, amino acids encoded by DH3-15*01 played divergent structural roles, inserting into a hole at the trimer apex, H-bonding to an exposed strand, or forming part of a loop scaffold. Overall, we identify a DH3-15*01-signature for rhesus V2 apex broadly neutralizing antibodies and show that highly selected genetic elements can play multiple roles in antigen recognition. HighlightsO_LIIsolated 11 V2 apex-targeted HIV-neutralizing lineages from 10 SHIV-infected Indian-origin rhesus macaques C_LIO_LICryo-EM structures of Fab-Env complexes for nine rhesus lineages reveal modes of recognition that mimic three modes of human V2 apex antibody recognition C_LIO_LIAll SHIV-elicited V2 apex lineages, including two others previously published, derive from the same DH3-15*01 gene utilizing reading frame two C_LIO_LIThe DH3-15*01 gene in reading frame two provides a necessary, but not sufficient, signature for V2 apex-directed broadly neutralizing antibodies C_LIO_LIStructural roles played by DH3-15*01-encoded amino acids differed substantially in different lineages, even for those with the same recognition mode C_LIO_LIPropose that the anionic, aromatic, and extended character of DH3-15*01 in reading frame two provides a selective advantage for V2 apex recognition compared to B cells derived from other D genes in the naive rhesus repertoire C_LIO_LIDemonstrate that highly selected genetic elements can play multiple roles in antigen recognition, providing a structural means to enhance recognition diversity C_LI

immunology↗

bioRxiv2023

Germline-targeting chimpanzee SIV Envelopes induce V2-apex broadly neutralizing-like B cell precursors in a rhesus macaque infection model

Eliciting broadly neutralizing antibodies-(bnAbs) remains a major goal of HIV-1 vaccine research. Previously, we showed that a soluble chimpanzee SIV Envelope-(Env) trimer, MT145K, bound several human V2-apex bnAb-precursors and stimulated an appropriate response in V2-apex bnAb precursor-expressing knock-in mice. Here, we tested the immunogenicity of three MT145 variants (MT145, MT145K, MT145K.dV5) expressed as chimeric simian-chimpanzee-immunodeficiency-viruses-(SCIVs) in rhesus macaques-(RMs). All three viruses established productive infections with high setpoint vRNA titers. RMs infected with the germline-targeting SCIV_MT145K and SCIV_MT145K.dV5 exhibited larger and more clonally expanded B cell lineages featuring long anionic heavy chain complementary-determining-regions-(HCDR3s) compared with wildtype SCIV_MT145. Moreover, antigen-specific B cell analysis revealed enrichment for long-CDHR3-bearing antibodies in SCIV_MT145K.dV5 infected animals with paratope features resembling prototypic V2-apex bnAbs and their precursors. Although none of the animals developed bnAbs, these results show that germline-targeting SCIVs can activate and preferentially expand B cells expressing V2-apex bnAb-like precursors, the first step in bnAb elicitation. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=180 HEIGHT=200 SRC="FIGDIR/small/558743v1_ufig1.gif" ALT="Figure 1"> View larger version (57K): org.highwire.dtl.DTLVardef@17673c8org.highwire.dtl.DTLVardef@1ab61a8org.highwire.dtl.DTLVardef@98781forg.highwire.dtl.DTLVardef@1f63e9b_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2023

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

Developing broad coronavirus vaccines requires identifying and understanding the molecular basis of broadly neutralizing antibody (bnAb) spike sites. In our previous work, we identified sarbecovirus spike RBD group 1 and 2 bnAbs. We have now shown that many of these bnAbs can still neutralize highly mutated SARS-CoV-2 variants, including the XBB.1.5. Structural studies revealed that group 1 bnAbs use recurrent germline encoded CDRH3 features to interact with a conserved RBD region that overlaps with class 4 bnAb site. Group 2 bnAbs recognize a less well-characterized "site V" on the RBD and destabilize spike trimer. The site V has remained largely unchanged in SARS-CoV- 2 variants and is highly conserved across diverse sarbecoviruses, making it a promising target for broad coronavirus vaccine development. Our findings suggest that targeted vaccine strategies may be needed to induce effective B cell responses to escape resistant subdominant spike RBD bnAb sites.

immunology↗

bioRxiv2022

Broadly neutralizing anti-S2 antibodies protect against all three human betacoronaviruses that cause severe disease

Pan-betacoronavirus neutralizing antibodies may hold the key to developing broadly protective vaccines against coronaviruses that cause severe disease, for anticipating novel pandemic-causing viruses, and to respond more effectively to SARS-CoV-2 variants. The emergence of the Omicron variant of SARS-CoV-2 has illustrated the limitations of solely targeting the receptor binding domain (RBD) of the envelope Spike (S)-protein. Here, we isolated a large panel of broadly neutralizing antibodies (bnAbs) from SARS-CoV-2 recovered-vaccinated donors that target a conserved S2 region in the fusion machinery on betacoronavirus spikes. Select bnAbs show broad in vivo protection against all three pathogenic betacoronaviruses, SARS-CoV-1, SARS-CoV-2 and MERS-CoV, that have spilled over into humans in the past 20 years to cause severe disease. The bnAbs provide new opportunities for antibody-based interventions and key insights for developing pan-betacoronavirus vaccines.

immunology↗

bioRxiv2021

Molecular insights into antibody-mediated protection against the prototypic simian immunodeficiency virus

SIVmac239 infection of macaques is a favored model of human HIV infection. However, the SIVmac239 envelope (Env) trimer structure, glycan occupancy, and the targets and ability of neutralizing antibodies (nAbs) to protect against SIVmac239 remain unknown. Here, we report the isolation of SIVmac239 nAbs that recognize a glycan hole and the V1/V4 loop. A high-resolution structure of a SIVmac239 Env trimer-nAb complex shows many similarities to HIV and SIVcpz Envs, but with distinct V4 features and an extended V1 loop. Moreover, SIVmac239 Env has a higher glycan shield density than HIV Env that may contribute to poor or delayed nAb responses in SIVmac239-infected macaques. Passive transfer of a nAb protects macaques from repeated low dose intraveneous SIVmac239 challenge at serum titers comparable to those described for protection of humans against HIV infection. Our results provide structural insights for vaccine design and shed light on antibody-mediated protection in the SIV model.

immunology↗

bioRxiv2021

Targeted isolation of panels of diverse human broadly neutralizing antibodies against SARS-like viruses

The emergence of current SARS-CoV-2 variants of concern (VOCs) and potential future spillovers of SARS-like coronaviruses into humans pose a major threat to human health and the global economy 1-7. Development of broadly effective coronavirus vaccines that can mitigate these threats is needed 8, 9. Notably, several recent studies have revealed that vaccination of recovered COVID-19 donors results in enhanced nAb responses compared to SARS-CoV-2 infection or vaccination alone 10-13. Here, we utilized a targeted donor selection strategy to isolate a large panel of broadly neutralizing antibodies (bnAbs) to sarbecoviruses from two such donors. Many of the bnAbs are remarkably effective in neutralization against sarbecoviruses that use ACE2 for viral entry and a substantial fraction also show notable binding to non-ACE2-using sarbecoviruses. The bnAbs are equally effective against most SARS-CoV-2 VOCs and many neutralize the Omicron variant. Neutralization breadth is achieved by bnAb binding to epitopes on a relatively conserved face of the receptor binding domain (RBD) as opposed to strain-specific nAbs to the receptor binding site that are commonly elicited in SARS-CoV-2 infection and vaccination 14-18. Consistent with targeting of conserved sites, select RBD bnAbs exhibited in vivo protective efficacy against diverse SARS-like coronaviruses in a prophylaxis challenge model. The generation of a large panel of potent bnAbs provides new opportunities and choices for next-generation antibody prophylactic and therapeutic applications and, importantly, provides a molecular basis for effective design of pan-sarbecovirus vaccines.

immunology↗

bioRxiv2021

Broadly neutralizing antibodies to SARS-related viruses can be readily induced in rhesus macaques

To prepare for future coronavirus (CoV) pandemics, it is desirable to generate vaccines capable of eliciting neutralizing antibody responses against multiple CoVs. Because of the phylogenetic similarity to humans, rhesus macaques are an animal model of choice for many virus-challenge and vaccine-evaluation studies, including SARS-CoV-2. Here, we show that immunization of macaques with SARS-CoV-2 spike (S) protein generates potent receptor binding domain cross- neutralizing antibody (nAb) responses to both SARS-CoV-2 and SARS-CoV-1, in contrast to human infection or vaccination where responses are typically SARS-CoV-2-specific. Furthermore, the macaque nAbs are equally effective against SARS-CoV-2 variants of concern. Structural studies show that different immunodominant sites are targeted by the two primate species. Human antibodies generally target epitopes strongly overlapping the ACE2 receptor binding site (RBS), whereas the macaque antibodies recognize a relatively conserved region proximal to the RBS that represents another potential pan-SARS-related virus site rarely targeted by human antibodies. B cell repertoire differences between the two primates appear to significantly influence the vaccine response and suggest care in the use of rhesus macaques in evaluation of vaccines to SARS-related viruses intended for human use. ONE SENTENCE SUMMARYBroadly neutralizing antibodies to an unappreciated site of conservation in the RBD in SARS- related viruses can be readily induced in rhesus macaques because of distinct properties of the naive macaque B cell repertoire that suggest prudence in the use of the macaque model in SARS vaccine evaluation and design.

immunology↗

bioRxiv2021

A protective broadly cross-reactive human antibody defines a conserved site of vulnerability on beta-coronavirus spikes

Broadly neutralizing antibodies (bnAbs) to coronaviruses (CoVs) are valuable in their own right as prophylactic and therapeutic reagents to treat diverse CoVs and, importantly, as templates for rational pan-CoV vaccine design. We recently described a bnAb, CC40.8, from a coronavirus disease 2019 (COVID-19)-convalescent donor that exhibits broad reactivity with human beta-coronaviruses ({beta}-CoVs). Here, we showed that CC40.8 targets the conserved S2 stem-helix region of the coronavirus spike fusion machinery. We determined a crystal structure of CC40.8 Fab with a SARS-CoV-2 S2 stem-peptide at 1.6 [A] resolution and found that the peptide adopted a mainly helical structure. Conserved residues in {beta}-CoVs interacted with CC40.8 antibody, thereby providing a molecular basis for its broad reactivity. CC40.8 exhibited in vivo protective efficacy against SARS-CoV-2 challenge in two animal models. In both models, CC40.8-treated animals exhibited less weight loss and reduced lung viral titers compared to controls. Furthermore, we noted CC40.8-like bnAbs are relatively rare in human COVID-19 infection and therefore their elicitation may require rational structure-based vaccine design strategies. Overall, our study describes a target on {beta}-CoV spike proteins for protective antibodies that may facilitate the development of pan-{beta}-CoV vaccines. SUMMARYA human mAb isolated from a COVID-19 donor defines a protective cross-neutralizing epitope for pan-{beta}-CoV vaccine design strategies

immunology↗

bioRxiv2021

Site-specific steric control of SARS-CoV-2 spike glycosylation

A central tenet in the design of vaccines is the display of native-like antigens in the elicitation of protective immunity. The abundance of N-linked glycans across the SARS-CoV-2 spike protein is a potential source of heterogeneity between the many different vaccine candidates under investigation. Here, we investigate the glycosylation of recombinant SARS-CoV-2 spike proteins from five different laboratories and compare them against infectious virus S protein. We find patterns which are conserved across all samples and this can be associated with site-specific stalling of glycan maturation which act as a highly sensitive reporter of protein structure. Molecular dynamics (MD) simulations of a fully glycosylated spike support s a model of steric restrictions that shape enzymatic processing of the glycans. These results suggest that recombinant spike-based SARS-CoV-2 immunogen glycosylation reproducibly recapitulates signatures of viral glycosylation.

biochemistry↗