S:D614G and S:H655Y are gateway mutations that act epistatically to promote SARS-CoV-2 variant fitness (preprint)

SARS-CoV-2 variants bearing complex combinations of mutations have been associated with increased transmissibility, COVID-19 severity, and immune escape. S:D614G may have facilitated emergence of such variants since they appeared after S:D614G had gone to fixation. To test this hypothesis, Spike sequences from an immunocompromised individual with prolonged infection, and from the major SARS-CoV-2 variants of concern, were reverted to the ancestral S:D614. In all cases, infectivity of the revertants was compromised. Rare SARS-CoV-2 lineages that lack S:D614G were identified and the infectivity of these was dependent upon S:Q613H or S:H655Y. Notably, Gamma and Omicron variants possess both S:D614G and S:H655Y, each of which contributed to infectivity of these variants. All three mutations, S:Q613H, S:D614G, and S:H655Y, stabilized Spike on virions, consistent with selection of these mutations by a common molecular mechanism. Among sarbecoviruses, S:Q613H, S:D614G, and S:H655Y are only detected in SARS-CoV-2, which uniquely possesses a polybasic S1/S2 cleavage site. Results of genetic and biochemical experiments here demonstrated that S:D614G and S:H655Y are likely adaptations to the cleavage site. CryoEM revealed that both mutations shift the Spike receptor binding domain towards the open conformation required for ACE2-binding and Spikes bearing either S:D614G or S:H655Y spontaneously mimic the smFRET signal that ACE2 induces in the parental molecule. Data from these orthogonal experiments demonstrate that S:D614G and S:H655Y are convergent adaptations to the polybasic S1/S2 cleavage site, which stabilize S1 on the virion in the open RBD conformation that is on-pathway for target cell fusion, and thereby act epistatically to promote the fitness of variants bearing complex combinations of clinically significant mutations.

Multimodal surveillance of SARS-CoV-2 at a university enables development of a robust outbreak response framework (preprint)

Universities are particularly vulnerable to infectious disease outbreaks and are also ideal environments to study transmission dynamics and evaluate mitigation and surveillance measures when outbreaks occur. Here, we introduce a SARS-CoV-2 surveillance and response framework based on high-resolution, multimodal data collected during the 2020-2021 academic year at Colorado Mesa University. We analyzed epidemiological and sociobehavioral data (demographics, contact tracing, and wifi-based co-location data) alongside pathogen surveillance data (wastewater, random, and reflexive diagnostic testing; and viral genomic sequencing of wastewater and clinical specimens) to characterize outbreak dynamics and inform policy decisions. We quantified group attributes that increased disease risk, and highlighted parallels between traditional and wifi-based contact tracing. We additionally used clinical and environmental viral sequencing to identify cryptic transmission, cluster overdispersion, and novel lineages or mutations. Ultimately, we used distinct data types to identify information that may help shape institutional policy and to develop a model of pathogen surveillance suitable for the future of outbreak preparedness.

Vaccine Breakthrough Infection with the SARS-CoV-2 Delta or Omicron (BA.1) Variant Leads to Distinct Profiles of Neutralizing Antibody Responses (preprint)

There is increasing evidence that the risk of SARS-CoV-2 infection among vaccinated individuals is variant-specific, suggesting that protective immunity against SARS-CoV-2 may differ by variant. We enrolled vaccinated (n = 39) and unvaccinated (n = 11) individuals with acute, symptomatic SARS-CoV-2 Delta or Omicron infection and performed SARS-CoV-2 viral load quantification, whole-genome sequencing, and variant-specific antibody characterization at the time of acute illness and convalescence. Viral load at the time of infection was inversely correlated with antibody binding and neutralizing antibody responses. Increases in antibody titers and neutralizing activity occurred at convalescence in a variant-specific manner. Across all variants tested, convalescent neutralization titers in unvaccinated individuals were markedly lower than in vaccinated individuals. For individuals infected with the Delta variant, neutralizing antibody responses were weakest against BA.2, whereas infection with Omicron BA.1 variant generated a broader response against all tested variants, including BA.2.

Analysis of 6.4 million SARS-CoV-2 genomes identifies mutations associated with fitness (preprint)

Repeated emergence of SARS-CoV-2 variants with increased fitness necessitates rapid detection and characterization of new lineages. To address this need, we developed PyR 0 , a hierarchical Bayesian multinomial logistic regression model that infers relative prevalence of all viral lineages across geographic regions, detects lineages increasing in prevalence, and identifies mutations relevant to fitness. Applying PyR 0 to all publicly available SARS-CoV-2 genomes, we identify numerous substitutions that increase fitness, including previously identified spike mutations and many non-spike mutations within the nucleocapsid and nonstructural proteins. PyR 0 forecasts growth of new lineages from their mutational profile, identifies viral lineages of concern as they emerge, and prioritizes mutations of biological and public health concern for functional characterization. One Sentence summary A Bayesian hierarchical model of all SARS-CoV-2 viral genomes predicts lineage fitness and identifies associated mutations.

Innate lymphoid cells and disease tolerance in SARS-CoV-2 infection (preprint)

BACKGROUNDRisk of severe coronavirus disease 2019 (COVID-19) increases with age, is greater in males, and is associated with decreased numbers of blood lymphoid cells. Though the reasons for these robust associations are unclear, effects of age and sex on innate and adaptive lymphoid subsets, including on homeostatic innate lymphoid cells (ILCs) implicated in disease tolerance, may underlie the effects of age and sex on COVID-19 morbidity and mortality. METHODSFlow cytometry was used to quantitate subsets of blood lymphoid cells from people infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), comparing those hospitalized with severe COVID-19 (n=40) and those treated as outpatients for less severe disease (n=51). 86 healthy individuals served as controls. The relationship between abundance of specific blood lymphoid cell types, age, sex, hospitalization, duration of hospitalization, and elevation of blood markers for systemic inflammation, was determined using multiple regression. RESULTSAfter accounting for effects of age and sex, hospitalization for COVID-19 was associated with 1.78-fold fewer ILCs (95%CI: 2.34-1.36; p = 4.55 x 10-5) and 2.31-fold fewer CD16+ natural killer (NK) cells (95%CI: 3.1-1.71; p = 1.04 x 10-7), when compared to uninfected controls. Among people infected with SARS-CoV-2, the odds ratio for hospitalization, adjusted for age, sex, and duration of symptoms, was 0.413 (95%CI: 0.197-0.724; p = 0.00691) for every 2-fold increase in ILCs. In addition, higher ILC abundance was associated with less time spent in the hospital and lower levels of blood markers associated with COVID-19 severity: each two-fold increase in ILC abundance was associated with a 9.38 day decrease in duration of hospital stay (95% CI: 15.76-3.01; p= 0.0054), and decrease in blood C-reactive protein (CRP) by 46.29 mg/L (95% CI: 71.34-21.24; p = 6.25 x 10-4), erythrocyte sedimentation rate (ESR) by 11.04 mm/h (95% CI: 21.94-0.13; p = 0.047), and the fibrin degradation product D-dimer by 1098.52 ng/mL (95% CI: 1932.84-264.19; p = 0.011). CONCLUSIONSBoth ILCs and NK cells were depleted in the blood of people hospitalized for severe COVID-19, but, among lymphoid cell subsets, only ILC abundance was independently associated with the need for hospitalization, duration of hospital stay, and severity of inflammation. These results indicate that, by promoting disease tolerance, homeostatic ILCs protect against morbidity and mortality in SARS-CoV-2 infection, and suggest that reduction in the number of ILCs with age and in males accounts for the increased risk of severe COVID-19 in these demographic groups.

Phylogenetic analysis of SARS-CoV-2 in the Boston area highlights the role of recurrent importation and superspreading events (preprint)

SARS-CoV-2 has caused a severe, ongoing outbreak of COVID-19 in Massachusetts with 111,070 confirmed cases and 8,433 deaths as of August 1, 2020. To investigate the introduction, spread, and epidemiology of COVID-19 in the Boston area, we sequenced and analyzed 772 complete SARS-CoV-2 genomes from the region, including nearly all confirmed cases within the first week of the epidemic and hundreds of cases from major outbreaks at a conference, a nursing facility, and among homeless shelter guests and staff. The data reveal over 80 introductions into the Boston area, predominantly from elsewhere in the United States and Europe. We studied two superspreading events covered by the data, events that led to very different outcomes because of the timing and populations involved. One produced rapid spread in a vulnerable population but little onward transmission, while the other was a major contributor to sustained community transmission, including outbreaks in homeless populations, and was exported to several other domestic and international sites. The same two events differed significantly in the number of new mutations seen, raising the possibility that SARS-CoV-2 superspreading might encompass disparate transmission dynamics. Our results highlight the failure of measures to prevent importation into MA early in the outbreak, underscore the role of superspreading in amplifying an outbreak in a major urban area, and lay a foundation for contact tracing informed by genetic data.

Unique mutational changes in SARS-CoV2 genome of different state of India (preprint)

COVID-19 is a global pandemic causing more than 8 million deaths till mid-August, 2020. In India, more than 3 million confirmed cases have been reported although with relatively low death rate of 1.8%. In this study, we sequenced 47 genomes of SARS-CoV-2 from the patients of 13 districts of Uttar Pradesh (UP), the largest state of India using third-generation sequencing technique. The phylogenetic clustering revealed that no UP sample was aligned with the previously defined USA clade, where the mortality was high. We identified 56 distinct SNP variations in the genomes of UP resulting in a unique mutation rate of 1.19% per sequence, which is greater than the value 0.88% obtained for the rest of India. The relatively less death rate in UP indicates that the mutation in the virus is deleterious. Further investigation is required with larger sample size to determine the degree of virulence vis-a-vis SNP variation.

SARS-CoV-2 3CLpro Whole Human Proteome Cleavage Prediction and Enrichment/Depletion Analysis (preprint)

A novel coronavirus (SARS-CoV-2) has devastated the globe as a pandemic that has killed more than 800,000 people. Effective and widespread vaccination is still uncertain, so many scientific efforts have been directed towards discovering antiviral treatments. Many drugs are being investigated to inhibit the coronavirus main protease, 3CLpro, from cleaving its viral polyprotein, but few publications have addressed this proteases interactions with the host proteome or their probable contribution to virulence. Too few host protein cleavages have been experimentally verified to fully understand 3CLpros global effects on relevant cellular pathways and tissues. Here, we set out to determine this proteases targets and corresponding potential drug targets. Using a neural network trained on coronavirus proteomes with a Matthews correlation coefficient of 0.983, we predict that a large proportion of the human proteome is vulnerable to 3CLpro, with 4,460 out of approximately 20,000 human proteins containing at least one predicted cleavage site. These cleavages are nonrandomly distributed and are enriched in the epithelium along the respiratory tract, brain, testis, plasma, and immune tissues and depleted in olfactory and gustatory receptors despite the prevalence of anosmia and ageusia in COVID-19 patients. Affected cellular pathways include cytoskeleton/motor/cell adhesion proteins, nuclear condensation and other epigenetics, host transcription and RNAi, coagulation, pattern recognition receptors, growth factor, lipoproteins, redox, ubiquitination, and apoptosis. This whole proteome cleavage prediction demonstrates the importance of 3CLpro in expected and nontrivial pathways affecting virulence, lead us to propose more than a dozen potential therapeutic targets against coronaviruses, and should therefore be applied to all viral proteases and experimentally verified.

Identification of SARS-CoV-2 induced pathways reveal drug repurposing strategies (preprint)

The global outbreak of SARS-CoV-2 necessitates the rapid development of new therapies against COVID-19 infection. Here, we present the identification of 200 approved drugs, appropriate for repurposing against COVID-19. We constructed a SARS-CoV-2-induced protein (SIP) network, based on disease signatures defined by COVID-19 multi-omic datasets(Bojkova et al., 2020; Gordon et al., 2020), and cross-examined these pathways against approved drugs. This analysis identified 200 drugs predicted to target SARS-CoV-2-induced pathways, 40 of which are already in COVID-19 clinical trials(Clinicaltrials.gov, 2020) testifying to the validity of the approach. Using artificial neural network analysis we classified these 200 drugs into 9 distinct pathways, within two overarching mechanisms of action (MoAs): viral replication (130) and immune response (70). A subset of drugs implicated in viral replication were tested in cellular assays and two (proguanil and sulfasalazine) were shown to inhibit replication. This unbiased and validated analysis opens new avenues for the rapid repurposing of approved drugs into clinical trials.

SARS-CoV-2 infection of human iPSC-derived cardiac cells predicts novel cytopathic features in hearts of COVID-19 patients (preprint)

COVID-19 causes cardiac dysfunction in up to 50% of patients, but the pathogenesis remains unclear. Infection of human iPSC-derived cardiomyocytes with SARS-CoV-2 revealed robust transcriptomic and morphological signatures of damage in cardiomyocytes. These morphological signatures include a distinct pattern of sarcomere fragmentation, with specific cleavage of thick filaments, and numerous iPSC-cardiomyocytes that lacked nuclear DNA. Human autopsy specimens from COVID-19 patients also displayed marked sarcomeric disruption and similar fragmentation, as well as prevalently enucleated cardiomyocytes. These striking transcriptomic and cytopathic changes provide a roadmap to understand the mechanisms of COVID-19 cardiac damage, search for potential treatments, and determine the basis for prolonged cardiac morbidity observed in this pandemic.

Experimental infection of cattle with SARS-CoV-2 (preprint)

Six cattle (Bos taurus) were intranasally inoculated with SARS-CoV-2 and kept together with three naive in-contact animals. Low-level virus replication and a specific sero-reactivity were observed in two inoculated animals, despite the presence of high antibody titers against a bovine betacoronavirus. The in-contact animals did not become infected.

Pathogenicity, immunogenicity, and protective ability of an attenuated SARS-CoV-2 variant with a deletion at the S1/S2 junction of the spike protein (preprint)

SARS-CoV-2 contains a PRRA polybasic cleavage motif considered critical for efficient infection and transmission in humans. We previously reported that virus variants with spike protein S1/S2 junction deletions spanning this motif are attenuated. Here we characterize a further cell-adapted SARS-CoV-2 variant, Ca-DelMut. Ca-DelMut replicates more efficiently than wild type or parental virus in cells, but causes no apparent disease in hamsters, despite replicating in respiratory tissues. Unlike wild type virus, Ca-DelMut does not induce proinflammatory cytokines in hamster infections, but still triggers a strong neutralizing antibody response. Ca-DelMut-immunized hamsters challenged with wild type SARS-CoV-2 are fully protected, demonstrating sterilizing immunity.

Discovery of drugs to treat cytokine storm-induced cardiac dysfunction using human cardiac organoids (preprint)

SARS-CoV2 infection leads to cardiac injury and dysfunction in 20-30% of hospitalized patients1 and higher rates of mortality in patients with pre-existing cardiovascular disease2,3. Inflammatory factors released as part of the cytokine storm are thought to play a critical role in cardiac dysfunction in severe COVID-19 patients4. Here we use human cardiac organoids combined with high sensitivity phosphoproteomics and single nuclei RNA sequencing to identify inflammatory targets inducing cardiac dysfunction. This state-of-the-art pipeline allowed rapid deconvolution of mechanisms and identification of putative therapeutics. We identify a novel interferon-{gamma} driven BRD4 (bromodomain protein 4)-fibrosis/iNOS axis as a key intracellular mediator of inflammation-induced cardiac dysfunction. This axis is therapeutically targetable using BRD4 inhibitors, which promoted full recovery of function in human cardiac organoids and prevented severe inflammation and death in a cytokine-storm mouse model. The BRD inhibitor INCB054329 was the most efficacious, and is a prime candidate for drug repurposing to attenuate cardiac dysfunction and improve COVID-19 mortality in humans.

Dynamics of the N-terminal domain of SARS-CoV-2 nucleocapsid protein drives dsRNA melting in a counterintuitive tweezer-like mechanism (preprint)

The N protein of betacoronaviruses is responsible for nucleocapsid assembly and other essential regulatory functions. Its N-terminal domain (NTD) interacts and melts the double-stranded transcriptional regulatory sequences (dsTRS), regulating the discontinuous subgenome transcription process. Here, we used molecular dynamics (MD) simulations to study the binding of SARS-CoV-2 N-NTD to non-specific (NS) and TRS dsRNAs. We probed dsRNAs Watson and Crick (WC) base-pairing over 25 replicas of 100 ns MD simulations, showing that only one N-NTD of dimeric N is enough to destabilize dsRNAs, initiating melting. N-NTD dsRNA destabilizing activity was more efficient for dsTRS than dsNS. N-NTD dynamics, especially a tweezer-like motion of {beta}2-{beta}3 and * 2-{beta}5 loops, played a key role in WC base-pairing destabilization. Based on experimental information available in the literature, we constructed kinetics models for N-NTD-mediated dsRNA melting. Our results support a 1:1 stoichiometry (N-NTD:dsRNA), matching MD simulations and raising different possibilities for N-NTD action: (i) two N-NTDs of dimeric N would act independently, increasing efficiency; (ii) two N-NTDs of dimeric N would bind to two different RNA sites, bridging distant regions of the genome; and (iii) monomeric N would be active, opening up the possibility of a regulatory dissociation event.

An hACE2 peptide mimic blocks SARS-CoV-2 Pulmonary Cell Infection (preprint)

In the light of the recent accumulated knowledge on SARS-CoV-2 and its mode of human cells invasion, the binding of viral spike glycoprotein to human Angiotensin Converting Enzyme 2 (hACE2) receptor plays a central role in cell entry. We designed a series of peptides mimicking the N-terminal helix of hACE2 protein which contains most of the contacting residues at the binding site and have a high helical folding propensity in aqueous solution. Our best peptide mimic binds to the virus spike protein with high affinity and is able to block SARS-CoV-2 human pulmonary cell infection with an inhibitory concentration (IC50) in the nanomolar range. This first in class blocking peptide mimic represents a powerful tool that might be used in prophylactic and therapeutic approaches to fight the coronavirus disease 2019 (COVID-19). In BriefHelical peptide mimicking H1 helix of hACE2 and composed of only natural amino acids binds to SARS-CoV-2 spike protein with high affinity and blocks human pulmonary cells infection with IC50 in the nM range. HighlightsA peptide mimic of hACE2 designed from H1 helix and composed of only natural amino acids show high helical folding propensity in aqueous media. This peptide mimic binds to virus spike RBD with high affinity (sub-nM range). This peptide mimic blocks SARS-CoV-2 pulmonary cells infection with an IC50 in the nM range. This peptide mimic is devoid of toxicity on pulmonary cells.

Flagellin from Pseudomonas aeruginosa increases the expression of the SARS-CoV2 entry protease TMPRSS2 in airway epithelial cells (preprint)

The major challenge of the COVID-19 health crisis is to identify the factors of susceptibility to SARS-Cov2 in order to adapt the recommendations to the populations and to reduce the risk of getting COVID-19 to the most vulnerable people especially those having chronic respiratory diseases (CRD) including cystic fibrosis (CF) and chronic pulmonary respiratory diseases (COPD). Airway epithelial cells (AEC) are playing a critical role in the immune response and in COVID-19 severity. SARS-CoV-2 infects the airways through ACE2 receptor and the host protease TMPRSS2 was shown to play a major role in SARS-CoV-2 infectivity. In this report we showed that Pseudomonas aeruginosa and its virulence factor flagellin (Fla-PA), a ligand of Toll-Like receptor 5 are able to increase TMPRSS2 expression in control and CF AEC. In contrast, no effect was observed with recombinant Salmonella typhimurium flagellin, used as an adjuvant in the clinical development of new vaccines against respiratory viruses. Considering the urgency of the health situation, this result is of major significance for patients with CRD (COPD, CF) which are frequently infected and colonized by P. aeruginosa during the course of the disease. In the general population, a P. aeruginosa ventilator-associated pneumonia in SARS-CoV-2 patients under intubation in intensive care units could be also deleterious and should be monitored with care.

The influence of major S protein mutations of SARS-CoV-2 on the potential B cell epitopes (preprint)

SARS-CoV-2 has rapidly transmitted worldwide and results in the COVID-19 pandemic. Spike glycoprotein on surface is a key factor of viral transmission, and has appeared a lot of variants due to gene mutations, which may influence the viral antigenicity and vaccine efficacy. Here, we used bioinformatic tools to analyze B-cell epitopes of prototype S protein and its 9 common variants. 12 potential linear and 53 discontinuous epitopes of B-cells were predicted from the S protein prototype. Importantly, by comparing the epitope alterations between prototype and variants, we demonstrate that B-cell epitopes and antigenicity of 9 variants appear significantly different alterations. The dominant D614G variant impacts the potential epitope least, only with moderately elevated antigenicity, while the epitopes and antigenicity of some mutants(V483A, V367F, etc.) with small incidence in the population change greatly. These results suggest that the currently developed vaccines should be valid for a majority of SARS-CoV-2 infectors. This study provides a scientific basis for large-scale application of SARS-CoV-2 vaccines and for taking precautions against the probable appearance of antigen escape induced by genetic variation after vaccination. Author SummaryThe global pandemic of SARS-CoV-2 has lasted for more than half a year and has not yet been contained. Until now there is no effective treatment for SARS-CoV-2 caused disease (COVID-19). Successful vaccine development seems to be the only hope. However, this novel coronavirus belongs to the RNA virus, there is a high mutation rate in the genome, and these mutations often locate on the Spike proteins of virus, the gripper of the virus entering the cells. Vaccination induce the generation of antibodies, which block Spike protein. However, the Spike protein variants may change the recognition and binding of antibodies and make the vaccine ineffective. In this study, we predict neutralizing antibody recognition sites (B cell epitopes) of the prototype S protein of SARS-COV2, along with several common variants using bioinformatics tools. We discovered the variability in antigenicity among the mutants, for instance, in the more widespread D614G variant the change of epitope was least affected, only with slight increase of antigenicity. However, the antigenic epitopes of some mutants change greatly. These results could be of potential importance for future vaccine design and application against SARS-CoV2 variants.

The SARS-CoV-2 Envelope and Membrane proteins modulate maturation and retention of the Spike protein, allowing optimal formation of VLPs in presence of Nucleoprotein (preprint)

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a {beta}-coronavirus, is the causative agent of the COVID-19 pandemic. Like for other coronaviruses, its particles are composed of four structural proteins, namely Spike S, Envelope E, Membrane M and Nucleoprotein N proteins. The involvement of each of these proteins and their interplays during the assembly process of this new virus are poorly-defined and are likely {beta}-coronavirus-type different. Therefore, we sought to investigate how SARS-CoV-2 behaves for its assembly by expression assays of S, in combination with E, M and/or N. By combining biochemical and imaging assays, we showed that E and M regulate intracellular trafficking of S and hence its furin-mediated processing. Indeed, our imaging data revealed that S remains at ERGIC or Golgi compartments upon expression of E or M, like for SARS-CoV-2 infected cells. By studying a mutant of S, we showed that its cytoplasmic tail, and more specifically, its C-terminal retrieval motif, is required for the M-mediated retention in the ERGIC, whereas E induces S retention by modulating the cell secretory pathway. We also highlighted that E and M induce a specific maturation of S N-glycosylation, which is observed on particles and lysates from infected cells independently of its mechanisms of intracellular retention. Finally, we showed that both M, E and N are required for optimal production of virus-like-proteins. Altogether, our results indicated that E and M proteins influence the properties of S proteins to promote assembly of viral particles. Our results therefore highlight both similarities and dissimilarities in these events, as compared to other {beta}-coronaviruses. Author SummaryThe severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the COVID-19 pandemic. Its viral particles are composed of four structural proteins, namely Spike S, Envelope E, Membrane M and Nucleoprotein N proteins, though their involvement in the virion assembly remain unknown for this particular coronavirus. Here we showed that presence of E and M influence the localization and maturation of S protein, in term of cleavage and N-glycosylation maturation. Indeed, E protein is able to slow down the cell secretory pathway whereas M-induced retention of S requires the retrieval motif in S C-terminus. We also highlighted that E and M might regulate the N glycosylation maturation of S independently of its intracellular retention mechanism. Finally, we showed that the four structural proteins are required for optimal formation of virus-like particles, highlighting the involvement of N, E and M in assembly of infectious particles. Altogether, our results highlight both similarities and dissimilarities in these events, as compared to other {beta}-coronaviruses.