Antibody avidity and multi-specificity combined to confer protection against SARS-CoV-2 and resilience against viral escape

SARS-CoV-2, the causative agent of COVID-19, has been responsible for a global pandemic. Monoclonal antibodies have been used as antiviral therapeutics, but have been limited in efficacy by viral sequence variability in emerging variants of concern (VOCs), and in deployment by the need for high doses. In this study, we leverage the MULTI-specific, multi-Affinity antiBODY (Multabody, MB) platform, derived from the human apoferritin protomer, to drive the multimerization of antibody fragments and generate exceptionally potent and broad SARS-CoV-2 neutralizers. CryoEM revealed a high degree of homogeneity for the core of these engineered antibody-like molecules at 2.1 [A] resolution. We demonstrate that neutralization potency improvements of the MB over corresponding IgGs translates into superior in vivo protection: in the SARS-CoV-2 mouse challenge model, comparable in vivo protection was achieved for the MB delivered at 30x lower dose compared to the corresponding IgGs. Furthermore, we show how MBs potently neutralize SARS-CoV-2 VOCs by leveraging augmented avidity, even when corresponding IgGs lose their ability to neutralize potently. Multiple mAb specificities could also be combined into a single MB molecule to expand the neutralization breadth beyond SARS-CoV-2 to other sarbecoviruses. Our work demonstrates how avidity and multi-specificity combined can be leveraged to confer protection and resilience against viral diversity that exceeds that of traditional monoclonal antibody therapies.

Antigenic characterization of the SARS-CoV-2 Omicron subvariant BA.2.75

The SARS-CoV-2 Omicron subvariant BA.2.75 emerged recently and appears to be spreading rapidly. It has nine mutations in its spike compared to BA.2, raising concerns it may further evade vaccine-elicited and therapeutic antibodies. Here, we found BA.2.75 to be moderately more neutralization resistant to sera from vaccinated/boosted individuals than BA.2 (1.8-fold), similar to BA.2.12.1 (1.1-fold), but more neutralization sensitive than BA.4/5 (0.6-fold). Relative to BA.2, BA.2.75 showed heightened resistance to class 1 and class 3 monoclonal antibodies to the receptor-binding domain, while gaining sensitivity to class 2 antibodies. The resistance was largely conferred by the G446S and R460K mutations. Of note, BA.2.75 was slightly resistant (3.7-fold) to bebtelovimab, the only therapeutic antibody with potent activity against all Omicron subvariants. BA.2.75 also exhibited higher receptor binding affinity than other Omicron subvariants. BA.2.75 provides yet another example of the ongoing evolution of SARS-CoV-2 as it gains transmissibility while incrementally evading antibody neutralization.

SARS-CoV-2 omicron variants succumb in vitro to Artemisia annua hot water extracts

The SARS-CoV-2 (COVID-19) global pandemic continuous to infect and kill millions while rapidly evolving new variants that are more transmissible and evading vaccine-elicited antibodies. Artemisia annua L. extracts have shown potency against all previously tested variants. Here we further queried extract efficacy against omicron and its recent subvariants. Using Vero E6 cells, we measured the in vitro efficacy (IC50) of stored (frozen) dried-leaf hot-water A. annua L. extracts of four cultivars (A3, BUR, MED, and SAM) against SARS-CoV-2 variants: original WA1 (WT), BA.1.1.529+R346K (omicron), BA.2, BA.2.12.1, and BA.4. IC50 values normalized to the extract artemisinin (ART) content ranged from 0.5-16.5 {micro}M ART. When normalized to dry mass of the extracted A. annua leaves, values ranged from 20-106 {micro}g. Although IC50 values for these new variants are slightly higher than those reported for previously tested variants, they were within limits of assay variation. There was no measurable loss of cell viability at leaf dry weights [≤]50 {micro}g of any cultivar extract. Results continue to indicate that oral consumption of A. annua hot-water extracts (tea infusions) could potentially provide a cost-effective approach to help stave off this pandemic virus and its rapidly evolving variants.

SARS-CoV-2 Omicron BA.2.12.1, BA.4, and BA.5 subvariants evolved to extend antibody evasion

SARS-CoV-2 Omicron subvariants BA.2.12.1 and BA.4/5 have surged dramatically to become dominant in the United States and South Africa, respectively1,2. These novel subvariants carrying additional mutations in their spike proteins raise concerns that they may further evade neutralizing antibodies, thereby further compromising the efficacy of COVID-19 vaccines and therapeutic monoclonals. We now report findings from a systematic antigenic analysis of these surging Omicron subvariants. BA.2.12.1 is only modestly (1.8-fold) more resistant to sera from vaccinated and boosted individuals than BA.2. However, BA.4/5 is substantially (4.2-fold) more resistant and thus more likely to lead to vaccine breakthrough infections. Mutation at spike residue L452 found in both BA.2.12.1 and BA.4/5 facilitates escape from some antibodies directed to the so-called class 2 and 3 regions of the receptor-binding domain3. The F486V mutation found in BA.4/5 facilitates escape from certain class 1 and 2 antibodies but compromises the spike affinity for the viral receptor. The R493Q reversion mutation, however, restores receptor affinity and consequently the fitness of BA.4/5. Among therapeutic antibodies authorized for clinical use, only bebtelovimab retains full potency against both BA.2.12.1 and BA.4/5. The Omicron lineage of SARS-CoV-2 continues to evolve, successively yielding subvariants that are not only more transmissible but also more evasive to antibodies.

Antibody Evasion Properties of SARS-CoV-2 Omicron Sublineages

The identification of the Omicron variant (B.1.1.529.1 or BA.1) of SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) in Botswana in November 20211 immediately raised alarms due to the sheer number of mutations in the spike glycoprotein that could lead to striking antibody evasion. We2 and others3-6 recently reported results in this Journal confirming such a concern. Continuing surveillance of Omicron evolution has since revealed the rise in prevalence of two sublineages, BA.1 with an R346K mutation (BA.1+R346K) and B.1.1.529.2 (BA.2), with the latter containing 8 unique spike mutations while lacking 13 spike mutations found in BA.1. We therefore extended our studies to include antigenic characterization of these new sublineages. Polyclonal sera from patients infected by wild-type SARS-CoV-2 or recipients of current mRNA vaccines showed a substantial loss in neutralizing activity against both BA.1+R346K and BA.2, with drops comparable to that already reported for BA.12,3,5,6. These findings indicate that these three sublineages of Omicron are antigenically equidistant from the wild-type SARS-CoV-2 and thus similarly threaten the efficacies of current vaccines. BA.2 also exhibited marked resistance to 17 of 19 neutralizing monoclonal antibodies tested, including S309 (sotrovimab)7, which had retained appreciable activity against BA.1 and BA.1+R346K2-4,6. This new finding shows that no presently approved or authorized monoclonal antibody therapy could adequately cover all sublineages of the Omicron variant.

Viral dynamics and duration of PCR positivity of the SARS-CoV-2 Omicron variant

BackgroundThe combined impact of immunity and SARS-CoV-2 variants on viral kinetics during infections has been unclear. MethodsWe characterized 2,875 infections from the National Basketball Association occupational health cohort identified between June 2020 and January 2022 using serial RT-qPCR testing. Logistic regression and semi-mechanistic viral RNA kinetics models were used to quantify the effect of variant, symptom status, age, infection history, vaccination and antibody titer to founder SARS-CoV-2 strain on the duration of potential infectiousness and overall viral kinetics. The frequency of viral rebounds was quantified under multiple cycle threshold (Ct) value-based definitions. ResultsAmong individuals detected partway through their infection, 51.0% (95% credible interval [CrI]: 48.2-53.6%) remained potentially infectious (Ct<30) five days post detection, with small differences across variants and vaccination history. Only seven viral rebounds (0.7%; N=999) were observed, with rebound defined as 3+ days with Ct<30 following an initial clearance of 3+ days with Ct[≥]30. High antibody titers against the founder SARS-CoV-2 strain predicted lower peak viral loads and shorter durations of infection. Among Omicron BA.1 infections, boosted individuals had lower pre-booster antibody titers and longer clearance times than non-boosted individuals. ConclusionsSARS-CoV-2 viral kinetics are partly determined by immunity and variant but dominated by individual-level variation. Since booster vaccination protects against infection, longer clearance times for BA.1-infected, boosted individuals may reflect a less effective immune response, more common in older individuals, that increases infection risk and reduces viral RNA clearance rate. The shifting landscape of viral kinetics underscores the need for continued monitoring to optimize isolation policies and to contextualize the health impacts of therapeutics and vaccines. FundingSupported in part by CDC contract 200-2016-91779, Emergent Ventures at the Mercatus Center, the Huffman Family Donor Advised Fund, the MorrisSinger Fund, the National Basketball Association, and the National Basketball Players Association.

Striking Antibody Evasion Manifested by the Omicron Variant of SARS-CoV-2

The Omicron (B.1.1.529) variant of SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) was only recently detected in southern Africa, but its subsequent spread has been extensive, both regionally and globally1. It is expected to become dominant in the coming weeks2, probably due to enhanced transmissibility. A striking feature of this variant is the large number of spike mutations3 that pose a threat to the efficacy of current COVID-19 (coronavirus disease 2019) vaccines and antibody therapies4. This concern is amplified by the findings from our study. We found B.1.1.529 to be markedly resistant to neutralization by serum not only from convalescent patients, but also from individuals vaccinated with one of the four widely used COVID-19 vaccines. Even serum from persons vaccinated and boosted with mRNA-based vaccines exhibited substantially diminished neutralizing activity against B.1.1.529. By evaluating a panel of monoclonal antibodies to all known epitope clusters on the spike protein, we noted that the activity of 17 of the 19 antibodies tested were either abolished or impaired, including ones currently authorized or approved for use in patients. In addition, we also identified four new spike mutations (S371L, N440K, G446S, and Q493R) that confer greater antibody resistance to B.1.1.529. The Omicron variant presents a serious threat to many existing COVID-19 vaccines and therapies, compelling the development of new interventions that anticipate the evolutionary trajectory of SARS-CoV-2.

Isolation and comparative analysis of antibodies that broadly neutralize sarbecoviruses

The devastation caused by SARS-CoV-2 has made clear the importance of pandemic preparedness. To address future zoonotic outbreaks due to related viruses in the sarbecovirus subgenus, we identified a human monoclonal antibody, 10-40, that neutralized or bound all sarbecoviruses tested in vitro and protected against SARS-CoV-2 and SARS-CoV in vivo. Comparative studies with other receptor-binding domain (RBD)-directed antibodies showed 10-40 to have the greatest breadth against sarbecoviruses and thus its promise as an agent for pandemic preparedness. Moreover, structural analyses on 10-40 and similar antibodies not only defined an epitope cluster in the inner face of the RBD that is well conserved among sarbecoviruses, but also uncovered a new antibody class with a common CDRH3 motif. Our analyses also suggested that elicitation of this class of antibodies may not be overly difficult, an observation that bodes well for the development of a pan-sarbecovirus vaccine. One sentence summaryA monoclonal antibody that neutralizes or binds all sarbecoviruses tested and represents a reproducible antibody class.

A monoclonal antibody that neutralizes SARS-CoV-2 variants, SARS-CoV, and other sarbecoviruses

The repeated emergence of highly pathogenic human coronaviruses as well as their evolving variants highlight the need to develop potent and broad-spectrum antiviral therapeutics and vaccines. By screening monoclonal antibodies (mAbs) isolated from COVID-19-convalescent patients, we found one mAb, 2-36, with cross-neutralizing activity against SARS-CoV. We solved the cryo-EM structure of 2-36 in complex with SARS-CoV-2 or SARS-CoV spike, revealing a highly conserved epitope in the receptor-binding domain (RBD). Antibody 2-36 neutralized not only all current circulating SARS-CoV-2 variants and SARS-COV, but also a panel of bat and pangolin sarbecoviruses that can use human angiotensin-converting enzyme 2 (ACE2) as a receptor. We selected 2-36-escape viruses in vitro and confirmed that K378T in SARS-CoV-2 RBD led to viral resistance. Taken together, 2-36 represents a strategic reserve drug candidate for the prevention and treatment of possible diseases caused by pre-emergent SARS-related coronaviruses. Its epitope defines a promising target for the development of a pan-sarbecovirus vaccine.

Artemisia annua hot-water extracts show potent activity in vitro against Covid-19 variants including delta

Ethnopharmacological relevanceFor millennia in Southeast Asia, Artemisia annua L. was used to treat "fever". This medicinal plant is effective against numerous infectious microbial and viral diseases and is used by many global communities as a source of artemisinin derivatives that are first-line drugs to treat malaria. Aim of the StudyThe SARS-CoV-2 (Covid-19) global pandemic has killed millions and evolved numerous variants, with delta being the most transmissible to date and causing break-through infections of vaccinated individuals. We further queried the efficacy of A. annua cultivars against new variants. Materials and MethodsUsing Vero E6 cells, we measured anti-SARS-CoV-2 activity of dried-leaf hot-water A. annua extracts of four cultivars, A3, BUR, MED, and SAM, to determine their efficacy against five fully infectious variants of the virus: alpha (B.1.1.7), beta (B.1.351), gamma (P.1), delta (B.1.617.2), and kappa (B.1.617.1). ResultsIn addition to being effective against the original wild type WA1, A. annua cultivars A3, BUR, MED and SAM were also potent against all five variants. IC50 and IC90 values based on measured artemisinin content ranged from 0.3-8.4 M and 1.4-25.0 M, respectively. The IC50 and IC90 values based on dried leaf weight (DW) used to make the tea infusions ranged from 11.0-67.7 g DW and 59.5-160.6 g DW, respectively. Cell toxicity was insignificant at a leaf dry weight of [≤]50 g in the extract of any cultivar. ConclusionsResults suggest that oral consumption of A. annua hot-water extracts (tea infusions), could provide a cost-effective therapy to help stave off the rapid global spread of these variants, buying time for broader implementation of vaccines.

Identification of Novel Susceptible Genes of Gastric Cancer Based on Integrated Omics Data.

Gastric cancer (GC) is one of the most common causes of cancer-related deaths in the world. This cancer has been regarded as a biological and genetically heterogeneous disease with a poorly understood carcinogenesis at the molecular level. Thousands of biomarkers and susceptible loci have been explored via experimental and computational methods, but their effects on disease outcome are still unknown. Genome-wide association studies (GWAS) have identified multiple susceptible loci for GC, but due to the linkage disequilibrium (LD), single-nucleotide polymorphisms (SNPs) may fall within the non-coding region and exert their biological function by modulating the gene expression level. In this study, we collected 1,091 cases and 410,350 controls from the GWAS catalog database. Integrating with gene expression level data obtained from stomach tissue, we conducted a machine learning-based method to predict GC-susceptible genes. As a result, we identified 787 novel susceptible genes related to GC, which will provide new insight into the genetic and biological basis for the mechanism and pathology of GC development.

A third COVID-19 vaccine shot markedly boosts neutralizing antibody potency and breadth

COVID-19 (coronavirus disease 2019) vaccines have been rapidly developed and deployed globally as a measure to combat the disease. These vaccines have been demonstrated to confer significant protection, but there have been reports of temporal decay in antibody titer. Furthermore, several variants have been identified with variable degrees of antibody resistance. These two factors suggest that a booster vaccination may be worthy of consideration. While such a booster dose has been studied as a series of three homologous vaccines in healthy individuals, to our knowledge, information on a heterologous regimen remains unreported, despite the practical benefits of such a scheme. Here, in this observational study, we investigated the serological profile of four healthy individuals who received two doses of the BNT162b2 vaccine, followed by a third booster dose with the Ad26.COV2.S vaccine. We found that while all individuals had spike-binding antibodies at each of the timepoints tested, there was an appreciable drop in titer by four months following the second vaccination. The third vaccine dose robustly increased titers beyond that of two vaccinations, and these elicited antibodies had neutralizing capability against all SARS-CoV-2 strains tested in both a recombinant vesicular stomatitis virus-based pseudovirus assay and an authentic SARS-CoV-2 assay, except for one individual against B.1.351 in the latter assay. Thus, a third COVID-19 vaccine dose in healthy individuals promoted not just neutralizing antibody potency, but also induced breadth against dominant SARS-CoV-2 variants. SignificanceCOVID-19 vaccines confer protection from symptomatic disease, but the elicited antibody titer has been found to decrease with time. Furthermore, SARS-CoV-2 variants with relative resistance against antibody neutralization have been identified. To overcome such issues, a third vaccine dose applied as a booster vaccine may be necessary. We studied four healthy individuals who received a heterologous booster dose as a third vaccine. All of these individuals had heightened neutralizing antibody titer following the booster vaccination, and could neutralize nearly all variants tested. Thus, a heterologous third COVID-19 vaccine dose may be a mechanism to both heighten and broaden antibody titers, and could be an additional strategy for controlling the SARS-CoV-2 pandemic.

Neutralizing antibody 5-7 defines a distinct site of vulnerability in SARS-CoV-2 spike N-terminal domain

Antibodies that potently neutralize SARS-CoV-2 target mainly the receptor-binding domain or the N-terminal domain (NTD). Over a dozen potently neutralizing NTD-directed antibodies have been studied structurally, and all target a single antigenic supersite in NTD (site 1). Here we report the 3.7 [A] resolution cryo-EM structure of a potent NTD-directed neutralizing antibody 5-7, which recognizes a site distinct from other potently neutralizing antibodies, inserting a binding loop into an exposed hydrophobic pocket between the two sheets of the NTD {beta}-sandwich. Interestingly, this pocket has been previously identified as the binding site for hydrophobic molecules including heme metabolites, but we observe their presence to not substantially impede 5-7 recognition. Mirroring its distinctive binding, antibody 5-7 retains a distinctive neutralization potency with variants of concern (VOC). Overall, we reveal a hydrophobic pocket in NTD proposed for immune evasion can actually be used by the immune system for recognition. HighlightsO_LICryo-EM structure of neutralizing antibody 5-7 in complex with SARS CoV-2 spike C_LIO_LI5-7 recognizes NTD outside of the previously identified antigenic supersite C_LIO_LI5-7 binds to a site known to accommodate numerous hydrophobic ligands C_LIO_LIStructural basis of 5-7 neutralization tolerance to some variants of concern C_LI

Efficacy and breadth of adjuvanted SARS-CoV-2 receptor-binding domain nanoparticle vaccine in macaques

Emergence of novel variants of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) underscores the need for next-generation vaccines able to elicit broad and durable immunity. Here we report the evaluation of a ferritin nanoparticle vaccine displaying the receptor-binding domain of the SARS-CoV-2 spike protein (RFN) adjuvanted with Army Liposomal Formulation QS-21 (ALFQ). RFN vaccination of macaques using a two-dose regimen resulted in robust, predominantly Th1 CD4+ T cell responses and reciprocal peak mean neutralizing antibody titers of 14,000-21,000. Rapid control of viral replication was achieved in the upper and lower airways of animals after high-dose SARS-CoV-2 respiratory challenge, with undetectable replication within four days in 7 of 8 animals receiving 50 {micro}g RFN. Cross-neutralization activity against SARS-CoV-2 variant B.1.351 decreased only [~]2-fold relative to USA-WA1. In addition, neutralizing, effector antibody and cellular responses targeted the heterotypic SARS-CoV-1, highlighting the broad immunogenicity of RFN-ALFQ for SARS-like betacoronavirus vaccine development. Significance StatementThe emergence of SARS-CoV-2 variants of concern (VOC) that reduce the efficacy of current COVID-19 vaccines is a major threat to pandemic control. We evaluate a SARS-CoV-2 Spike receptor-binding domain ferritin nanoparticle protein vaccine (RFN) in a nonhuman primate challenge model that addresses the need for a next-generation, efficacious vaccine with increased pan-SARS breadth of coverage. RFN, adjuvanted with a liposomal-QS21 formulation (ALFQ), elicits humoral and cellular immune responses exceeding those of current vaccines in terms of breadth and potency and protects against high-dose respiratory tract challenge. Neutralization activity against the B.1.351 VOC within two-fold of wild-type virus and against SARS-CoV-1 indicate exceptional breadth. Our results support consideration of RFN for SARS-like betacoronavirus vaccine development.

Efficacy of a Broadly Neutralizing SARS-CoV-2 Ferritin Nanoparticle Vaccine in Nonhuman Primates

The emergence of novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants stresses the continued need for next-generation vaccines that confer broad protection against coronavirus disease 2019 (COVID-19). We developed and evaluated an adjuvanted SARS-CoV-2 Spike Ferritin Nanoparticle (SpFN) vaccine in nonhuman primates (NHPs). High-dose (50 {micro}g) SpFN vaccine, given twice within a 28 day interval, induced a Th1-biased CD4 T cell helper response and a peak neutralizing antibody geometric mean titer of 52,773 against wild-type virus, with activity against SARS-CoV-1 and minimal decrement against variants of concern. Vaccinated animals mounted an anamnestic response upon high-dose SARS-CoV-2 respiratory challenge that translated into rapid elimination of replicating virus in their upper and lower airways and lung parenchyma. SpFNs potent and broad immunogenicity profile and resulting efficacy in NHPs supports its utility as a candidate platform for SARS-like betacoronaviruses. One-Sentence SummaryA SARS-CoV-2 Spike protein ferritin nanoparticle vaccine, co-formulated with a liposomal adjuvant, elicits broad neutralizing antibody responses that exceed those observed for other major vaccines and rapidly protects against respiratory infection and disease in the upper and lower airways and lung tissue of nonhuman primates.

Increased Resistance of SARS-CoV-2 Variant P.1 to Antibody Neutralization

The relative resistance of SARS-CoV-2 variants B.1.1.7 and B.1.351 to antibody neutralization has been described recently. We now report that another emergent variant from Brazil, P.1, is not only refractory to multiple neutralizing monoclonal antibodies, but also more resistant to neutralization by convalescent plasma (3.4 fold) and vaccinee sera (3.8-4.8 fold). The cryo-electron microscopy structure of a soluble prefusion-stabilized spike reveals the P.1 trimer to adopt exclusively a conformation in which one of the receptor-binding domains is in the "up" position, with the functional impact of mutations appearing to arise from local changes instead of global conformational alterations. The P.1 variant threatens current antibody therapies but less so the protective efficacy of our vaccines.

Structural Basis for Accommodation of Emerging B.1.351 and B.1.1.7 Variants by Two Potent SARS-CoV-2 Neutralizing Antibodies

Emerging SARS-CoV-2 strains, B.1.1.7 and B.1.351, from the UK and South Africa, respectively show decreased neutralization by monoclonal antibodies and convalescent or vaccinee sera raised against the original wild-type virus, and are thus of clinical concern. However, the neutralization potency of two antibodies, 1-57 and 2-7, which target the receptor-binding domain (RBD) of spike, was unaffected by these emerging strains. Here, we report cryo-EM structures of 1-57 and 2-7 in complex with spike, revealing each of these antibodies to utilize a distinct mechanism to bypass or accommodate RBD mutations. Notably, each antibody represented a response with recognition distinct from those of frequent antibody classes. Moreover, many epitope residues recognized by 1-57 and 2-7 were outside hotspots of evolutionary pressure for both ACE2 binding and neutralizing antibody escape. We suggest the therapeutic use of antibodies like 1-57 and 2-7, which target less prevalent epitopes, could ameliorate issues of monoclonal antibody escape.

A Novel SARS-CoV-2 Variant of Concern, B.1.526, Identified in New York

Recent months have seen surges of SARS-CoV-2 infection across the globe with considerable viral evolution1-3. Extensive mutations in the spike protein may threaten efficacy of vaccines and therapeutic monoclonal antibodies4. Two signature mutations of concern are E484K, which plays a crucial role in the loss of neutralizing activity of antibodies, and N501Y, a driver of rapid worldwide transmission of the B.1.1.7 lineage. Here, we report the emergence of variant lineage B.1.526 that contains E484K and its alarming rise to dominance in New York City in early 2021. This variant is partially or completely resistant to two therapeutic monoclonal antibodies in clinical use and less susceptible to neutralization by convalescent plasma or vaccinee sera, posing a modest antigenic challenge. The B.1.526 lineage has now been reported from all 50 states in the US and numerous other countries. B.1.526 rapidly replaced earlier lineages in New York upon its emergence, with an estimated transmission advantage of 35%. Such transmission dynamics, together with the relative antibody resistance of its E484K sub-lineage, likely contributed to the sharp rise and rapid spread of B.1.526. Although SARS-CoV-2 B.1.526 initially outpaced B.1.1.7 in the region, its growth subsequently slowed concurrent with the rise of B.1.1.7 and ensuing variants.

Increased Resistance of SARS-CoV-2 Variants B.1.351 and B.1.1.7 to Antibody Neutralization

The COVID-19 pandemic has ravaged the globe, and its causative agent, SARS-CoV-2, continues to rage. Prospects of ending this pandemic rest on the development of effective interventions. Single and combination monoclonal antibody (mAb) therapeutics have received emergency use authorization1-3, with more in the pipeline4-7. Furthermore, multiple vaccine constructs have shown promise8, including two with ~95% protective efficacy against COVID-199,10. However, these interventions were directed toward the initial SARS-CoV-2 that emerged in 2019. The recent emergence of new SARS-CoV-2 variants B.1.1.7 in the UK11 and B.1.351 in South Africa12 is of concern because of their purported ease of transmission and extensive mutations in the spike protein. We now report that B.1.1.7 is refractory to neutralization by most mAbs to the N-terminal domain (NTD) of spike and relatively resistant to a few mAbs to the receptor-binding domain (RBD). It is not more resistant to convalescent plasma or vaccinee sera. Findings on B.1.351 are more worrisome in that this variant is not only refractory to neutralization by most NTD mAbs but also by multiple individual mAbs to the receptor-binding motif on RBD, largely due to an E484K mutation. Moreover, B.1.351 is markedly more resistant to neutralization by convalescent plasma (9.4 fold) and vaccinee sera (10.3-12.4 fold). B.1.351 and emergent variants13,14 with similar spike mutations present new challenges for mAb therapy and threaten the protective efficacy of current vaccines.

Potent SARS-CoV-2 Neutralizing Antibodies Directed Against Spike N-Terminal Domain Target a Single Supersite

Numerous antibodies that neutralize SARS-CoV-2 have been identified, and these generally target either the receptor-binding domain (RBD) or the N-terminal domain (NTD) of the viral spike. While RBD-directed antibodies have been extensively studied, far less is known about NTD-directed antibodies. Here we report cryo-EM and crystal structures for seven potent NTD-directed neutralizing antibodies in complex with spike or isolated NTD. These structures defined several antibody classes, with at least one observed in multiple convalescent donors. The structures revealed all seven antibodies to target a common surface, bordered by glycans N17, N74, N122, and N149. This site - formed primarily by a mobile {beta}-hairpin and several flexible loops - was highly electropositive, located at the periphery of the spike, and the largest glycan-free surface of NTD facing away from the viral membrane. Thus, in contrast to neutralizing RBD-directed antibodies that recognize multiple non-overlapping epitopes, potent NTD-directed neutralizing antibodies target a single supersite.