SARS-CoV-2 Omicron subvariants BA.2.12.1 and BA.4/5 have surged notably to become dominant in the United States and South Africa, respectively
. These new subvariants carrying further 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 domain
. 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.
The COVID-19 pandemic has had widespread effects across the globe, and its causative agent, SARS-CoV-2, continues to spread. Effective interventions need to be developed to end this pandemic. Single ...and combination therapies with monoclonal antibodies have received emergency use authorization
, and more treatments are under development
. Furthermore, multiple vaccine constructs have shown promise
, including two that have an approximately 95% protective efficacy against COVID-19
. However, these interventions were directed against the initial SARS-CoV-2 virus that emerged in 2019. The recent detection of SARS-CoV-2 variants B.1.1.7 in the UK
and B.1.351 in South Africa
is of concern because of their purported ease of transmission and extensive mutations in the spike protein. Here we show that B.1.1.7 is refractory to neutralization by most monoclonal antibodies against the N-terminal domain of the spike protein and is relatively resistant to a few monoclonal antibodies against the receptor-binding domain. It is not more resistant to plasma from individuals who have recovered from COVID-19 or sera from individuals who have been vaccinated against SARS-CoV-2. The B.1.351 variant is not only refractory to neutralization by most monoclonal antibodies against the N-terminal domain but also by multiple individual monoclonal antibodies against the receptor-binding motif of the receptor-binding domain, which is mostly due to a mutation causing an E484K substitution. Moreover, compared to wild-type SARS-CoV-2, B.1.351 is markedly more resistant to neutralization by convalescent plasma (9.4-fold) and sera from individuals who have been vaccinated (10.3-12.4-fold). B.1.351 and emergent variants
with similar mutations in the spike protein present new challenges for monoclonal antibody therapies and threaten the protective efficacy of current vaccines.
Nirmatrelvir, an oral antiviral targeting the 3CL protease of SARS-CoV-2, has been demonstrated to be clinically useful against COVID-19 (refs.
). However, because SARS-CoV-2 has evolved to become ...resistant to other therapeutic modalities
, there is a concern that the same could occur for nirmatrelvir. Here we examined this possibility by in vitro passaging of SARS-CoV-2 in nirmatrelvir using two independent approaches, including one on a large scale. Indeed, highly resistant viruses emerged from both and their sequences showed a multitude of 3CL protease mutations. In the experiment peformed with many replicates, 53 independent viral lineages were selected with mutations observed at 23 different residues of the enzyme. Nevertheless, several common mutational pathways to nirmatrelvir resistance were preferred, with a majority of the viruses descending from T21I, P252L or T304I as precursor mutations. Construction and analysis of 13 recombinant SARS-CoV-2 clones showed that these mutations mediated only low-level resistance, whereas greater resistance required accumulation of additional mutations. E166V mutation conferred the strongest resistance (around 100-fold), but this mutation resulted in a loss of viral replicative fitness that was restored by compensatory changes such as L50F and T21I. Our findings indicate that SARS-CoV-2 resistance to nirmatrelvir does readily arise via multiple pathways in vitro, and the specific mutations observed herein form a strong foundation from which to study the mechanism of resistance in detail and to inform the design of next-generation protease inhibitors.
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron subvariant BA.2.75 emerged recently and appears to be spreading. It has nine mutations in spike compared with the currently ...circulating BA.2, raising concerns that it may further evade vaccine-elicited and therapeutic antibodies. 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 targeting the spike-receptor-binding domain while gaining sensitivity to class 2 antibodies. Resistance was largely conferred by G446S and R460K mutations. BA.2.75 was slightly resistant (3.7-fold) to bebtelovimab, a therapeutic antibody with potent activity against all Omicron subvariants. BA.2.75 also exhibited a higher binding affinity to host receptor ACE2 than other Omicron subvariants. BA.2.75 provides further insight into SARS-CoV-2 evolution as it gains transmissibility while incrementally evading antibody neutralization.
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•BA.2.75 is more resistant to neutralization by polyclonal sera than BA.2•BA.2.75 shows heightened resistance to class 1 and class 3 RBD-directed antibodies•BA.2.75 is the first variant to show discernible resistance to bebtelovimab•BA.2.75 exhibits higher human ACE2-binding affinity than other Omicron subvariants
Wang et al. have systematically evaluated the antigenic properties of the new SARS-CoV-2 Omicron subvariant BA.2.75. They found that BA.2.75 exhibits greater neutralization resistance to monoclonal antibodies and vaccine- and infection-induced sera than previous Omicron subvariant BA.2, while showing a higher binding affinity for human ACE2.
The recently reported B.1.1.529 Omicron variant of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) includes 34 mutations in the spike protein relative to the Wuhan strain, including 15 ...mutations in the receptor-binding domain (RBD). Functional studies have shown Omicron to substantially escape the activity of many SARS-CoV-2-neutralizing antibodies. Here, we report a 3.1 Å-resolution cryoelectron microscopy (cryo-EM) structure of the Omicron spike protein ectodomain. The structure depicts a spike that is exclusively in the 1-RBD-up conformation with high mobility of RBD. Many mutations cause steric clashes and/or altered interactions at antibody-binding surfaces, whereas others mediate changes of the spike structure in local regions to interfere with antibody recognition. Overall, the structure of the Omicron spike reveals how mutations alter its conformation and explains its extraordinary ability to evade neutralizing antibodies.
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•SARS-CoV-2 Omicron spike exclusively adopts a 1-RBD-up conformation•Omicron substitutions alter conformation and mobility of the RBD•A subset of Omicron mutations changes the local conformation of spike•The structure reveals the basis of antibody neutralization escape
Cerutti et al. report the cryo-EM structure of the SARS-CoV-2 Omicron spike in its ligand-free form. The structure elucidates the effect of the mutations on the global and local conformation of spike and explains the antibody resistance to the Omicron variant.
Viruses with approximately 50% homology to human influenza C virus (ICV) have recently been isolated from swine and cattle. The overall low homology to ICV, lack of antibody cross-reactivity to ICV ...in hemagglutination inhibition (HI) and agar gel immunodiffusion assays, and inability to productively reassort with ICV led to the proposal that these viruses represented a new genus of influenza virus, influenzavirus D (IDV). To further our understanding of the epidemiology of IDV, real-time reverse transcription-PCR was performed on a set of 208 samples from bovines with respiratory disease. Ten samples (4.8%) were positive and six viruses were successfully isolated in vitro. Phylogenetic analysis of full-genome sequences of these six new viruses and four previously reported viruses revealed two distinct cocirculating lineages represented by D/swine/Oklahoma/1334/2011 (D/OK) and D/bovine/Oklahoma/660/2013 (D/660), which frequently reassorted with one another. Antigenic analysis using the HI assay and lineage-representative D/OK and D/660 antiserum found up to an approximate 10-fold loss in cross-reactivity against heterologous clade antiserum. One isolate, D/bovine/Texas/3-13/2011 (D/3-13), clustered with the D/660 lineage, but also had high HI titers to heterologous (D/OK) clade antiserum. Molecular modeling of the hemagglutinin esterase fusion protein of D/3-13 identified a mutation at position 212 as a possible antigenic determinant responsible for the discrepant HI results. These results suggest that IDV is common in bovines with respiratory disease and that at least two genetic and antigenically distinct clades cocirculate.
A novel bovine influenza virus was recently identified. Detailed genetic and antigenic studies led to the proposal that this virus represents a new genus of influenza, influenzavirus D (IDV). Here, we show that IDV is common in clinical samples of bovine respiratory disease complex (BRDC), with a prevalence similar to that of other established BRDC etiological agents. These results are in good agreement with the near-ubiquitous seroprevalence of IDV previously found. Phylogenetic analysis of complete genome sequences found evidence for two distinct cocirculating lineages of IDV which freely reassort. Significant antigenic differences, which generally agreed with the surface glycoprotein hemagglutinin esterase phylogeny, were observed between the two lineages. Based on these results, and on the ability of IDV to infect and transmit in multiple mammalian species, additional studies to determine the pathogenic potential of IDV are warranted.
The diversity of B cell receptors provides a basis for recognizing numerous pathogens. Antibody repertoire sequencing has revealed relationships between B cell receptor sequences, their diversity, ...and their function in infection, vaccination, and disease. However, many repertoire datasets have been deposited without annotation or quality control, limiting their utility. To accelerate investigations of B cell immunoglobulin sequence repertoires and to facilitate development of algorithms for their analysis, we constructed a comprehensive public database of curated human B cell immunoglobulin sequence repertoires, cAb-Rep (https://cab-rep.c2b2.columbia.edu), which currently includes 306 immunoglobulin repertoires from 121 human donors, who were healthy, vaccinated, or had autoimmune disease. The database contains a total of 267.9 million V(D)J heavy chain and 72.9 million VJ light chain transcripts. These transcripts are full-length or near full-length, have been annotated with gene origin, antibody isotype, somatic hypermutations, and other biological characteristics, and are stored in FASTA format to facilitate their direct use by most current repertoire-analysis programs. We describe a website to search cAb-Rep for similar antibodies along with methods for analysis of the prevalence of antibodies with specific genetic signatures, for estimation of reproducibility of somatic hypermutation patterns of interest, and for delineating frequencies of somatically introduced
-glycosylation. cAb-Rep should be useful for investigating attributes of B cell sequence repertoires, for understanding characteristics of affinity maturation, and for identifying potential barriers to the elicitation of effective neutralizing antibodies in infection or by vaccination.
Antibodies with ontogenies from VH1-2 or VH1-46-germline genes dominate the broadly neutralizing response against the CD4-binding site (CD4bs) on HIV-1. Here, we define with longitudinal sampling ...from time-of-infection the development of a VH1-46-derived antibody lineage that matured to neutralize 90% of HIV-1 isolates. Structures of lineage antibodies CH235 (week 41 from time-of-infection, 18% breadth), CH235.9 (week 152, 77%), and CH235.12 (week 323, 90%) demonstrated the maturing epitope to focus on the conformationally invariant portion of the CD4bs. Similarities between CH235 lineage and five unrelated CD4bs lineages in epitope focusing, length-of-time to develop breadth, and extraordinary level of somatic hypermutation suggested commonalities in maturation among all CD4bs antibodies. Fortunately, the required CH235-lineage hypermutation appeared substantially guided by the intrinsic mutability of the VH1-46 gene, which closely resembled VH1-2. We integrated our CH235-lineage findings with a second broadly neutralizing lineage and HIV-1 co-evolution to suggest a vaccination strategy for inducing both lineages.
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•Developmental pathway of a CD4-mimicking antibody lineage from time of infection•Maturation involves focused recognition of CD4-binding site of vulnerability•Intrinsic VH1-46 gene mutability guides somatic mutation of CD4-binding site bnAbs•Study provided a strategy for inducing both CD4-mimicking and CDR H3-using bnAbs
The complete life history of an HIV-1 broadly neutralizing antibody lineage, from the time of infection through development of its full potency and breadth, reveals key features that are common between HIV-1 antibodies from unrelated donors and that can be exploited to induce similar antibodies with vaccines.
HIV-1-neutralizing antibodies develop in most HIV-1-infected individuals, although highly effective antibodies are generally observed only after years of chronic infection. Here, we characterize the ...rate of maturation and extent of diversity for the lineage that produced the broadly neutralizing antibody VRC01 through longitudinal sampling of peripheral B cell transcripts over 15 years and co-crystal structures of lineage members. Next-generation sequencing identified VRC01-lineage transcripts, which encompassed diverse antibodies organized into distinct phylogenetic clades. Prevalent clades maintained characteristic features of antigen recognition, though each evolved binding loops and disulfides that formed distinct recognition surfaces. Over the course of the study period, VRC01-lineage clades showed continuous evolution, with rates of ∼2 substitutions per 100 nucleotides per year, comparable to that of HIV-1 evolution. This high rate of antibody evolution provides a mechanism by which antibody lineages can achieve extraordinary diversity and, over years of chronic infection, develop effective HIV-1 neutralization.
Of the Orthomyxoviridae family of viruses, only influenza A viruses are thought to exist as multiple subtypes and has non-human maintenance hosts. In April 2011, nasal swabs were collected for virus ...isolation from pigs exhibiting influenza-like illness. Subsequent electron microscopic, biochemical, and genetic studies identified an orthomyxovirus with seven RNA segments exhibiting approximately 50% overall amino acid identity to human influenza C virus. Based on its genetic organizational similarities to influenza C viruses this virus has been provisionally designated C/Oklahoma/1334/2011 (C/OK). Phylogenetic analysis of the predicted viral proteins found that the divergence between C/OK and human influenza C viruses was similar to that observed between influenza A and B viruses. No cross reactivity was observed between C/OK and human influenza C viruses using hemagglutination inhibition (HI) assays. Additionally, screening of pig and human serum samples found that 9.5% and 1.3%, respectively, of individuals had measurable HI antibody titers to C/OK virus. C/OK virus was able to infect both ferrets and pigs and transmit to naive animals by direct contact. Cell culture studies showed that C/OK virus displayed a broader cellular tropism than a human influenza C virus. The observed difference in cellular tropism was further supported by structural analysis showing that hemagglutinin esterase (HE) proteins between two viruses have conserved enzymatic but divergent receptor-binding sites. These results suggest that C/OK virus represents a new subtype of influenza C viruses that currently circulates in pigs that has not been recognized previously. The presence of multiple subtypes of co-circulating influenza C viruses raises the possibility of reassortment and antigenic shift as mechanisms of influenza C virus evolution.
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