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Age is a major risk factor for hospitalization and death after SARS-CoV-2 infection, even in vaccinees. Suboptimal responses to a primary vaccination course have been reported in the elderly, but there is little information regarding the impact of age on responses to booster third doses. Here we show that individuals 70 or older who received a primary two dose schedule with AZD1222 and booster third dose with mRNA vaccine achieved significantly lower neutralizing antibody responses against SARS-CoV-2 spike pseudotyped virus compared to those younger than 70. One month after the booster neither the concentration of serum binding anti spike IgG antibody, nor the frequency of spike-specific B cells showed differences by age grouping. However, the impaired neutralization potency and breadth post-third dose in the elderly was associated with enrichment of circulating "atypical" spike-specific B cells expressing CD11c and FCRL5. Single cell RNA sequencing confirmed an expansion of TBX21-, ITGAX-expressing B cells in the elderly that enriched for B cell activation/receptor signalling pathway genes. Importantly we also observed impaired T cell responses to SARS-CoV-2 spike peptides in the elderly post-booster, both in terms of IFNgamma and IL2 secretion, as well as a decrease in T cell receptor signalling pathway genes. This expansion of atypical B cells and impaired T cell responses may contribute to the generation of less affinity-matured antibodies, with lower neutralizing capacity post-third dose in the elderly. Altogether, our data reveal the extent and potential mechanistic underpinning of the impaired vaccine responses present in the elderly after a booster dose, contributing to their increased susceptibility to COVID-19 infection.
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BackgroundThere are no real world data on vaccine elicited neutralising antibody responses for the worlds most widely used vaccine, AZD1222, in African populations following scale up. Here, we measured i) baseline SARS-CoV-2 seroprevalence and levels of protective neutralizing antibodies prior to vaccination rollout using both flow cytometric based analysis of binding antibodies to nucleocapsid (N), coupled with virus neutralisation approaches and ii) neutralizing antibody responses to VOC prior to vaccination (January 2021) and after two-doses of AZD1222 vaccine administered with a 12 week interval in Lagos, Nigeria - a period when the Delta variant was circulating. MethodsHealth workers at multiple sites in Lagos were recruited to the study. For binding antibody measurement, IgG antibodies against SARS-COV-2 Wuhan-1 receptor-binding domain (RBD), trimeric spike protein (S), nucleocapsid protein (N) and Omicron S1 were measured using the Luminex-based SARS-CoV-2-IgG assay by flow cytometry. For plasma neutralising antibody measurement, SARS-CoV-2 lentiviral pseudovirus (PV) were prepared by transfecting 293T cells with Wuhan-614G wild type (WT), B.1.617.2 (Delta) and BA.1 (Omicron) plasmids in conjunction with HIV-1 expression vectors and luciferase encoding genome flanked by LTRs. We performed serial plasma dilutions from each time point and mixed plasma with PV before infecting HeLa-ACE2 cell lines, reading out luminescence and calculating ID50 (reciprocal dilution of sera required to inhibit 50% of PV infection). ResultsOur underlying study population receiving at least one dose of vaccine comprised 140 participants with a median age of 40 (interquartile range: 33, 48). 62/140 (44%) participants were anti-N IgG positive prior to administration of first vaccine dose. 49 had plasma samples available at baseline prior to vaccination and at two follow-up timepoints post two dose vaccination for neutralization assays. Half of the participants, 25/49 (51%) were IgG anti-N positive at baseline. Of the 24 individuals anti-N Ab negative at baseline, 12/24 had ID50 above the cut-off of 20. In these individuals, binding antibodies to S were also detectable, and neutralisation correlated with IgG anti-S, suggesting waning of N antibody after infection. Overall, neutralizing Ab titres to WT 1 month after second dose were 2579 and at 3 months post second-dose were 1695. As expected, lower levels of neutralization were observed against the Delta GMT 549 and Omicron variants 269 at 1 month. Positive anti-N IgG Ab status at baseline was associated with significantly higher titres of neutralizing antibodies following vaccination across all tested VOC. Those with anti-N Abs present at baseline did not experience waning of responses between months 1 and 3 post second dose. When data were analysed for negative anti-N IgG status at any timepoint, there was a significant decline in neutralization and binding antibodies between 1 month and 3 months post second-dose. The GMT in these individuals for Delta and Omicron was approximately 100, nearly a log lower in comparison to WT. We tested anti-N IgG in subjects who were anti-N IgG negative at baseline (n=78) and became positive between 1- and 3-months post second dose and found 7/49 (14%) with de-novo infection, with one additional participant demonstrating both reinfection and breakthrough infection to yield a total breakthrough rate of 8/49 (16%). Neutralising and binding Ab titres 1 month post vaccine, prior to breakthrough, were not associated with breakthrough infection. Neutralizing titres were higher at the last time point in individuals who had experienced vaccine breakthrough infection (with no evidence of infection prior to vaccine), indicating a boosting effect of infection in addition to vaccine. However, neutralisation and binding S antibodies against Omicron were low in those with either prior exposure or infection following two dose AZD1222. ConclusionsAZD1222 is immunogenic in this real world west African cohort with significant background seroprevalence and incidence of breakthrough infection over a short time period. Prior infection and breakthrough infection induced higher anti-SARS-CoV-2 Ab responses at 3 months post vaccine against all widely circulating VOC. However, responses to Omicron BA.1 were low at three months regardless of hybrid immunity from prior exposure or breakthrough infection. Booster doses after AZD1222 should be considered in the African setting, even after natural infection, as future variants may be more pathogenic as well as immune evasive in the context of waning immunity.
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Over 20 mutations have been identified in the N-Terminal Domain (NTD) of SARS-CoV-2 spike and yet few of them are fully characterised. Here we first examined the contribution of the NTD to infection and cell-cell fusion by constructing different VOC-based chimeric spikes bearing B.1617 lineage (Delta and Kappa variants) NTDs and generating spike pseudotyped lentivirus (PV). We found the Delta NTD on a Kappa or WT background increased spike S1/S2 cleavage efficiency and virus entry, specifically in Calu-3 lung cells and airway organoids, through use of TMPRSS2. We have previously shown Delta spike confers rapid cell-cell fusion kinetics; here we show that increased fusogenicity can be conferred to WT and Kappa variant spikes by transfer of the Delta NTD. Moving to contemporary variants, we found that BA.2 had higher entry efficiency in a range of cell types as compared to BA.1. BA.2 showed higher fusogenic activity than BA.1, but the BA.2 NTD could not confer higher fusion to BA.1 spike. There was low efficiency of TMPRSS2 usage by both BA.1 and BA.2, and chimeras of Omicron BA.1 and BA.2 spikes with a Delta NTD did not result in more efficient use of TMRPSS2 or cell-cell fusogenicity. We conclude that the NTD allosterically modulates S1/S2 cleavage and spike-mediated functions such as entry and cell-cell fusion in a spike context dependent manner, and allosteric interactions may be lost when combining regions from more distantly related spike proteins. These data may explain the lack of successful SARS-CoV-2 inter-variant recombinants bearing breakpoints within spike.
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The COVID-19 pandemic caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) presents a great threat to human health. The interplay between the virus and host plays a crucial role in successful virus replication and transmission. Understanding host-virus interactions is essential for development of new COVID-19 treatment strategies. Here we show that SARS-CoV-2 infection triggers redistribution of cyclin D1 and cyclin D3 from the nucleus to the cytoplasm, followed by its proteasomal degradation. No changes to other cyclins or cyclin dependent kinases were observed. Further, cyclin D depletion was independent from SARS-CoV-2 mediated cell cycle arrest in early S phase or S/G2/M phase. Cyclin D3 knockdown by small interfering RNA specifically enhanced progeny virus titres in supernatants. Finally, cyclin D3 co-immunoprecipitated with SARS-CoV-2 Envelope and Membrane proteins. We propose that cyclin D3 inhibits virion assembly and is depleted during SARS-CoV-2 infection to restore efficient assembly and release of newly produced virions.
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The first SARS-CoV-2 variant of concern (VOC) to be designated was lineage B.1.1.7, later labelled by the World Health Organisation (WHO) as Alpha. Originating in early Autumn but discovered in December 2020, it spread rapidly and caused large waves of infections worldwide. The Alpha variant is notable for being defined by a long ancestral phylogenetic branch with an increased evolutionary rate, along which only two sequences have been sampled. Alpha genomes comprise a well-supported monophyletic clade within which the evolutionary rate is more typical of SARS-CoV-2. The Alpha epidemic continued to grow despite the continued restrictions on social mixing across the UK, and the imposition of new restrictions, in particular the English national lockdown in November 2020. While these interventions succeeded in reducing the absolute number of cases, the impact of these non-pharmaceutical interventions was predominantly to drive the decline of the SARS-CoV-2 lineages which preceded Alpha. We investigate the only two sampled sequences that fall on the branch ancestral to Alpha. We find that one is likely to be a true intermediate sequence, providing information about the order of mutational events that led to Alpha. We explore alternate hypotheses that can explain how Alpha acquired a large number of mutations yet remained largely unobserved in a region of high genomic surveillance: an under-sampled geographical location, a non-human animal population, or a chronically-infected individual. We conclude that the last hypothesis provides the best explanation of the observed behaviour and dynamics of the variant, although we find that the individual need not be immunocompromised, as persistently-infected immunocompetent hosts also display a higher within-host rate of evolution. Finally, we compare the ancestral branches and mutation profiles of other VOCs to each other, and identify that Delta appears to be an outlier both in terms of the genomic locations of its defining mutations, and its lack of rapid evolutionary rate on the ancestral branch. As new variants, such as Omicron, continue to evolve (potentially through similar mechanisms) it remains important to investigate the origins of other variants to identify ways to potentially disrupt their evolution and emergence.
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Among the 30 non-synonymous nucleotide substitutions in the Omicron S-gene are 13 that have only rarely been seen in other SARS-CoV-2 sequences. These mutations cluster within three functionally important regions of the S-gene at sites that will likely impact (i) interactions between subunits of the Spike trimer and the predisposition of subunits to shift from down to up configurations, (ii) interactions of Spike with ACE2 receptors, and (iii) the priming of Spike for membrane fusion. We show here that, based on both the rarity of these 13 mutations in intrapatient sequencing reads and patterns of selection at the codon sites where the mutations occur in SARS-CoV-2 and related sarbecoviruses, prior to the emergence of Omicron the mutations would have been predicted to decrease the fitness of any genomes within which they occurred. We further propose that the mutations in each of the three clusters therefore cooperatively interact to both mitigate their individual fitness costs, and adaptively alter the function of Spike. Given the evident epidemic growth advantages of Omicron over all previously known SARS-CoV-2 lineages, it is crucial to determine both how such complex and highly adaptive mutation constellations were assembled within the Omicron S-gene, and why, despite unprecedented global genomic surveillance efforts, the early stages of this assembly process went completely undetected.
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The SARS-CoV-2 Omicron BA.1 variant emerged in late 2021 and is characterised by multiple spike mutations across all spike domains. Here we show that Omicron BA.1 has higher affinity for ACE2 compared to Delta, and confers very significant evasion of therapeutic monoclonal and vaccine-elicited polyclonal neutralising antibodies after two doses. mRNA vaccination as a third vaccine dose rescues and broadens neutralisation. Importantly, antiviral drugs remdesevir and molnupiravir retain efficacy against Omicron BA.1. We found that in human nasal epithelial 3D cultures replication was similar for both Omicron and Delta. However, in lower airway organoids, Calu-3 lung cells and gut adenocarcinoma cell lines live Omicron virus demonstrated significantly lower replication in comparison to Delta. We noted that despite presence of mutations predicted to favour spike S1/S2 cleavage, the spike protein is less efficiently cleaved in live Omicron virions compared to Delta virions. We mapped the replication differences between the variants to entry efficiency using spike pseudotyped virus (PV) entry assays. The defect for Omicron PV in specific cell types correlated with higher cellular RNA expression of TMPRSS2, and accordingly knock down of TMPRSS2 impacted Delta entry to a greater extent as compared to Omicron. Furthermore, drug inhibitors targeting specific entry pathways demonstrated that the Omicron spike inefficiently utilises the cellular protease TMPRSS2 that mediates cell entry via plasma membrane fusion. Instead, we demonstrate that Omicron spike has greater dependency on cell entry via the endocytic pathway requiring the activity of endosomal cathepsins to cleave spike. Consistent with suboptimal S1/S2 cleavage and inability to utilise TMPRSS2, syncytium formation by the Omicron spike was dramatically impaired compared to the Delta spike. Overall, Omicron appears to have gained significant evasion from neutralising antibodies whilst maintaining sensitivity to antiviral drugs targeting the polymerase. Omicron has shifted cellular tropism away from TMPRSS2 expressing cells that are enriched in cells found in the lower respiratory and GI tracts, with implications for altered pathogenesis.
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Breakthrough infections with SARS-CoV-2 Delta variant have been reported in vaccine recipients and in individuals infected with previous variants. However the potential for fully vaccinated individuals (two doses) to transmit SARS-CoV-2 is unclear. We here analyse data from health care workers in two hospitals in India, constructing probable transmission networks from epidemiological and virus genome sequence data using a suite of computational approaches. Among known cases we identify a high probability that doubly vaccinated individuals transmitted SARS-CoV-2, and potential cases of virus transmission between individuals who had received two doses of vaccine. Our findings highlight the need for ongoing infection control measures even in highly vaccinated populations.
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Patients on dialysis are at risk of severe course of SARS-CoV-2 infection. Understanding the neutralizing activity and coverage of SARS-CoV-2 variants of vaccine-elicited antibodies is required to guide prophylactic and therapeutic COVID-19 interventions in this frail population. By analyzing plasma samples from 130 hemodialysis and 13 peritoneal dialysis patients after two doses of BNT162b2 or mRNA-1273 vaccines, we found that 35% of the patients had low-level or undetectable IgG antibodies to SARS-CoV-2 Spike (S). Neutralizing antibodies against the vaccine-matched SARS-CoV-2 and Delta variant were low or undetectable in 49% and 77% of patients, respectively, and were further reduced against other emerging variants. The fraction of non-responding patients was higher in SARS-CoV-2-naive hemodialysis patients immunized with BNT162b2 (66%) than those immunized with mRNA-1273 (23%). The reduced neutralizing activity correlated with low antibody avidity. Patients followed up to 7 months after vaccination showed a rapid decay of the antibody response with an average 21- and 10-fold reduction of neutralizing antibodies to vaccine-matched SARS-CoV-2 and Delta variant, which increased the fraction of non-responders to 84% and 90%, respectively. These data indicate that dialysis patients should be prioritized for additional vaccination boosts. Nevertheless, their antibody response to SARS-CoV-2 must be continuously monitored to adopt the best prophylactic and therapeutic strategy.
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Prevention of SARS-CoV-2 entry in cells through the modulation of viral host receptors, such as ACE2, could represent a new therapeutic approach complementing vaccination. However, the mechanisms controlling ACE2 expression remain elusive. Here, we identify the farnesoid X receptor (FXR) as a direct regulator of ACE2 transcription in multiple COVID19-affected tissues, including the gastrointestinal and respiratory systems. We demonstrate that FXR antagonists, including the over-the-counter compound z-guggulsterone (ZGG) and the off-patent drug ursodeoxycholic acid (UDCA), downregulate ACE2 levels, and reduce susceptibility to SARS-CoV-2 infection in lung, cholangiocyte and gut organoids. We then show that therapeutic levels of UDCA downregulate ACE2 in human organs perfused ex situ and reduce SARS-CoV-2 infection ex vivo. Finally, we perform a retrospective study using registry data and identify a correlation between UDCA treatment and positive clinical outcomes following SARS-CoV-2 infection, including hospitalisation, ICU admission and death. In conclusion, we identify a novel function of FXR in controlling ACE2 expression and provide evidence that this approach could be beneficial for reducing SARS-CoV-2 infection, thereby paving the road for future clinical trials.
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Delhi, the national capital of India, has experienced multiple SARS-CoV-2 outbreaks in 2020 and reached a population seropositivity of over 50% by 2021. During April 2021, the city became overwhelmed by COVID-19 cases and fatalities, as a new variant B.1.617.2 (Delta) replaced B.1.1.7 (Alpha). A Bayesian model explains the growth advantage of Delta through a combination of increased transmissibility and partial reduction of immunity elicited by prior infection (median estimates; x1.5-fold, 20% reduction). Seropositivity of an employee and family cohort increased from 42% to 86% between March and July 2021, with 27% reinfections, as judged by increased antibody concentration after previous decline. The likely high transmissibility and partial evasion of immunity by the Delta variant contributed to an overwhelming surge in Delhi. One-Sentence SummaryDelhi experienced an overwhelming surge of COVID-19 cases and fatalities peaking in May 2021 as the highly transmissible and immune evasive Delta variant replaced the Alpha variant.
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The SARS-CoV-2 B.1.617.2 (Delta) variant was first identified in the state of Maharashtra in late 2020 and spread throughout India, outcompeting pre-existing lineages including B.1.617.1 (Kappa) and B.1.1.7 (Alpha). In vitro, B.1.617.2 is 6-fold less sensitive to serum neutralising antibodies from recovered individuals, and 8-fold less sensitive to vaccine-elicited antibodies as compared to wild type Wuhan-1 bearing D614G. Serum neutralising titres against B.1.617.2 were lower in ChAdOx-1 versus BNT162b2 vaccinees. B.1.617.2 spike pseudotyped viruses exhibited compromised sensitivity to monoclonal antibodies against the receptor binding domain (RBD) and N-terminal domain (NTD), in particular to the clinically approved bamlavinimab and imdevimab monoclonal antibodies. B.1.617.2 demonstrated higher replication efficiency in both airway organoid and human airway epithelial systems as compared to B.1.1.7, associated with B.1.617.2 spike being in a predominantly cleaved state compared to B.1.1.7. Additionally we observed that B.1.617.2 had higher replication and spike mediated entry as compared to B.1.617.1, potentially explaining B.1.617.2 dominance. In an analysis of over 130 SARS-CoV-2 infected healthcare workers across three centres in India during a period of mixed lineage circulation, we observed substantially reduced ChAdOx-1 vaccine efficacy against B.1.617.2 relative to non-B.1.617.2. Compromised vaccine efficacy against the highly fit and immune evasive B.1.617.2 Delta variant warrants continued infection control measures in the post-vaccination era.
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The emergence and rapid rise in prevalence of three independent SARS-CoV-2 "501Y lineages, B.1.1.7, B.1.351 and P.1, in the last three months of 2020 prompted renewed concerns about the evolutionary capacity of SARS-CoV-2 to adapt to both rising population immunity, and public health interventions such as vaccines and social distancing. Viruses giving rise to the different 501Y lineages have, presumably under intense natural selection following a shift in host environment, independently acquired multiple unique and convergent mutations. As a consequence, all have gained epidemiological and immunological properties that will likely complicate the control of COVID-19. Here, by examining patterns of mutations that arose in SARS-CoV-2 genomes during the pandemic we find evidence of a major change in the selective forces acting on various SARS-CoV-2 genes and gene segments (such as S, nsp2 and nsp6), that likely coincided with the emergence of the 501Y lineages. In addition to involving continuing sequence diversification, we find evidence that a significant portion of the ongoing adaptive evolution of the 501Y lineages also involves further convergence between the lineages. Our findings highlight the importance of monitoring how members of these known 501Y lineages, and others still undiscovered, are convergently evolving similar strategies to ensure their persistence in the face of mounting infection and vaccine induced host immune recognition.
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Two dose mRNA vaccination provides excellent protection against SARS-CoV-2. However, there are few data on vaccine efficacy in elderly individuals above the age of 801. Additionally, new variants of concern (VOC) with reduced sensitivity to neutralising antibodies have raised fears for vulnerable groups. Here we assessed humoral and cellular immune responses following vaccination with mRNA vaccine BNT162b22 in elderly participants prospectively recruited from the community and younger health care workers. Median age was 72 years and 51% were females amongst 140 participants. Neutralising antibody responses after the first vaccine dose diminished with increasing age, with a marked drop in participants over 80 years old. Sera from participants below and above 80 showed significantly lower neutralisation potency against B.1.1.7, B.1.351 and P.1. variants of concern as compared to wild type. Those over 80 were more likely to lack any neutralisation against VOC compared to younger participants following first dose. The adjusted odds ratio for inadequate neutralisation activity against the B.1.1.7, P.1 and B.1.351 variant in the older versus younger age group was 4.3 (95% CI 2.0-9.3, p<0.001), 6.7 (95% CI 1.7-26.3, p=0.008) and 1.7 (95% CI 0.5-5.7, p=0.41). Binding IgG and IgA antibodies were lower in the elderly, as was the frequency of SARS-CoV-2 Spike specific B-memory cells. We observed a trend towards lower somatic hypermutation in participants with suboptimal neutralisation, and elderly participants demonstrated clear reduction in class switched somatic hypermutation, driven by the IgA1/2 isotype. SARS-CoV-2 Spike specific T-cell IFN{gamma} and IL-2 responses fell with increasing age, and both cytokines were secreted primarily by CD4 T cells. We conclude that the elderly are a high risk population that warrant specific measures in order to mitigate against vaccine failure, particularly where variants of concern are circulating.
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Multiple SARS-CoV-2 vaccines have shown protective efficacy, which is most likely mediated by neutralizing antibodies recognizing the viral entry protein, Spike. Antibodies from SARS-CoV-2 infection neutralize the virus by focused targeting of Spike and there is limited serum cross-neutralization of the closely-related SARS-CoV. As new SARS-CoV-2 variants are rapidly emerging, exemplified by the B.1.1.7, 501Y.V2 and P.1 lineages, it is critical to understand if antibody responses induced by infection with the original SARS-CoV-2 virus or the current vaccines will remain effective against virus variants. In this study we evaluate neutralization of a series of mutated Spike pseudotypes including a B.1.1.7 Spike pseudotype. The analyses of a panel of Spike-specific monoclonal antibodies revealed that the neutralizing activity of some antibodies was dramatically reduced by Spike mutations. In contrast, polyclonal antibodies in the serum of patients infected in early 2020 remained active against most mutated Spike pseudotypes. The majority of serum samples were equally able to neutralize the B.1.1.7 Spike pseudotype, however potency was reduced in a small number of samples (3 of 36) by 5-10-fold. This work highlights that changes in the SARS-CoV-2 Spike can alter neutralization sensitivity and underlines the need for effective real-time monitoring of emerging mutations and their impact on vaccine efficacy.
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Severe Covid-19 is associated with elevated plasma Factor V (FV) and increased risk of thromboembolism. We report that neutrophils, T regulatory cells (Tregs), and monocytes from patients with severe Covid-19 express FV, and expression correlates with T cell lymphopenia. In vitro full length FV, but not FV activated by thrombin cleavage, suppresses T cell proliferation. Increased and prolonged FV expression by cells of the innate and adaptive immune systems may contribute to lymphopenia in severe Covid-19. Activation by thrombin destroys the immunosuppressive properties of FV. Anticoagulation in Covid-19 patients may have the unintended consequence of suppressing the adaptive immune system.
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In a study of 207 SARS-CoV2-infected individuals with a range of severities followed over 12 weeks from symptom onset, we demonstrate that an early robust bystander CD8 T cell immune response, without systemic inflammation, is characteristic of asymptomatic or mild disease. Those presenting to hospital had delayed bystander responses and systemic inflammation already evident at around symptom onset. Such early evidence of inflammation suggests immunopathology may be inevitable in some individuals, or that preventative intervention might be needed before symptom onset. Viral load does not correlate with the development of this pathological response, but does with its subsequent severity. Immune recovery is complex, with profound persistent cellular abnormalities correlating with a change in the nature of the inflammatory response, where signatures characteristic of increased oxidative phosphorylation and reactive-oxygen species-associated inflammation replace those driven by TNF and IL-6. These late immunometabolic inflammatory changes and unresolved immune defects may have clinical implications.
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SARS-CoV-2 Spike protein is critical for virus infection via engagement of ACE2, and amino acid variation in Spike is increasingly appreciated. Given both vaccines and therapeutics are designed around Wuhan-1 Spike, this raises the theoretical possibility of virus escape, particularly in immunocompromised individuals where prolonged viral replication occurs. Here we report chronic SARS-CoV-2 with reduced sensitivity to neutralising antibodies in an immune suppressed individual treated with convalescent plasma, generating whole genome ultradeep sequences by both short and long read technologies over 23 time points spanning 101 days. Although little change was observed in the overall viral population structure following two courses of remdesivir over the first 57 days, N501Y in Spike was transiently detected at day 55 and V157L in RdRp emerged. However, following convalescent plasma we observed large, dynamic virus population shifts, with the emergence of a dominant viral strain bearing D796H in S2 and{Delta} H69/{Delta}V70 in the S1 N-terminal domain NTD of the Spike protein. As passively transferred serum antibodies diminished, viruses with the escape genotype diminished in frequency, before returning during a final, unsuccessful course of convalescent plasma. In vitro, the Spike escape double mutant bearing{Delta} H69/{Delta}V70 and D796H conferred decreased sensitivity to convalescent plasma, whilst maintaining infectivity similar to wild type. D796H appeared to be the main contributor to decreased susceptibility, but incurred an infectivity defect. The{Delta} H69/{Delta}V70 single mutant had two-fold higher infectivity compared to wild type and appeared to compensate for the reduced infectivity of D796H. Consistent with the observed mutations being outside the RBD, monoclonal antibodies targeting the RBD were not impacted by either or both mutations, but a non RBD binding monoclonal antibody was less potent against{Delta} H69/{Delta}V70 and the double mutant. These data reveal strong selection on SARS-CoV-2 during convalescent plasma therapy associated with emergence of viral variants with reduced susceptibility to neutralising antibodies.
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SARS-CoV-2 amino acid replacements in the receptor binding domain (RBD) occur relatively frequently and some have a consequence for immune recognition. Here we report recurrent emergence and significant onward transmission of a six-nucleotide out of frame deletion in the S gene, which results in loss of two amino acids: H69 and V70. We report that in human infections {Delta}H69/V70 often co-occurs with the receptor binding motif amino acid replacements N501Y, N439K and Y453F, and in the latter two cases has followed the RBD mutation. One of the {Delta}H69/V70+ N501Y lineages, now known as B.1.1.7, has undergone rapid expansion and includes eight S gene mutations: RBD (N501Y and A570D), S1 ({Delta}H69/V70 and {Delta}144) and S2 (P681H, T716I, S982A and D1118H). In vitro, we show that {Delta}H69/V70 does not reduce serum neutralisation across multiple convalescent sera. However, {Delta}H69/V70 increases infectivity and is associated with increased incorporation of cleaved spike into virions. {Delta}H69/V70 is able to compensate for small infectivity defects induced by RBD mutations N501Y, N439K and Y453F. In addition, replacement of H69 and V70 residues in the B.1.1.7 spike reduces its infectivity and spike mediated cell-cell fusion. Based on our data {Delta}H69/V70 likely acts as a permissive mutation that allows acquisition of otherwise deleterious immune escape mutations. Enhanced surveillance for the {Delta}H69/V70 deletion with and without RBD mutations should be considered as a global priority not only as a marker for the B.1.1.7 variant, but potentially also for other emerging variants of concern. Vaccines designed to target the deleted spike protein could mitigate against its emergence as increased selective forces from immunity and vaccines increase globally. HighlightsO_LI{Delta}H69/V70 is present in at least 28 SARS-CoV-2 lineages C_LIO_LI{Delta}H69/V70 does not confer escape from convalescent sera C_LIO_LI{Delta}H69/V70 increases spike infectivity and compensates for RBD mutations C_LIO_LI{Delta}H69/V70 is associated with greater spike cleavage C_LIO_LIB.1.1.7 requires {Delta}H69/V70 for optimal spike cleavage and infectivity C_LI
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SARS-CoV-2 transmission occurs via airborne droplets and surface contamination. We show tiles coated with TiO2 120 days previously can inactivate SARS-CoV-2 under ambient indoor lighting with 87% reduction in titres at 1h and complete loss by 5h exposure. TiO2 coatings could be an important tool in containing SARS-CoV-2.
