Age- and sex-specific differences in immune responses to BNT162b2 COVID-19 and live-attenuated influenza vaccines in UK adolescents (preprint)

Key to understanding COVID-19 correlates of protection is assessing vaccine-induced immunity in different demographic groups. Sex- and age-specific immune differences have a wide impact on outcomes from infections and immunisations. Typically, adult females make stronger immune responses and have better disease outcomes but suffer more adverse events following vaccination and are more prone to autoimmune disease. To understand better the mechanisms underlying these differences in vaccine responses, we studied immune responses to two doses of BNT162b2 Pfizer COVID-19 vaccine in an adolescent cohort (n=34, ages 12-16), an age group previously shown to make significantly greater immune responses to the same vaccine compared to young adults. At the same time, we were able to evaluate immune responses to the co-administered live attenuated influenza vaccine, which has been shown to induce stronger immune responses in adult females. Blood samples from 34 adolescents taken pre- and post-vaccination with COVID-19 and influenza vaccines were assayed for SARS-CoV-2-specific IgG and neutralising antibodies, and cellular immunity specific for SARS-CoV-2 and endemic betacoronaviruses. IgG targeting influenza lineages contained in the influenza vaccine was also assessed. As previously demonstrated, total IgG responses to SARS-CoV-2 Spike antigens were significantly higher among vaccinated adolescents compared to adults (aged 32-52) who received the BNT162b2 vaccine (comparing infection-naive, 49,696 vs 33,339; p=0.03; comparing SARS-CoV-2 previously-infected, 743,691 vs 269,985; p<0.0001) by MSD v-plex assay. However, unexpectedly, antibody responses to BNT162b2 and the live-attenuated influenza vaccine were not higher among female adolescents compared to males; among infection-naive adolescents, antibody responses to BNT162b2 were higher in males than females (62,270 vs 36,951 p=0.008). No sex difference was identified in vaccinated adults. These unexpected findings may result from the introduction of novel mRNA vaccination platforms, generating patterns of immunity divergent from established trends, and providing new insights into what might be protective following COVID-19 vaccination.

CD4+ and CD8+ T cell and antibody correlates of protection against Delta vaccine breakthrough infection: A nested case-control study within the PITCH study (preprint)

T cell correlates of protection against SARS-CoV-2 infection after vaccination ('vaccine breakthrough') are incompletely defined, especially the specific contributions of CD4+ and CD8+ T cells. We studied 279 volunteers in the Protective Immunity from T Cells in Healthcare Workers (PITCH) UK study, including 32 cases (with SARS-CoV-2 positive testing after two vaccine doses during the Delta-dominant era) and 247 controls (no positive test nor anti-nucleocapsid seroconversion during this period). 28 days after second vaccination, before all breakthroughs occurred, cases had lower ancestral S- and RBD-specific immunoglobulin G titres and S1- and S2-specific T cell interferon gamma (IFN{gamma}) responses compared with controls. In a subset of matched cases and controls, cases had lower CD4+ and CD8+ IFN{gamma} and tumour necrosis factor responses to Delta S peptides with reduced CD8+ responses to Delta versus ancestral peptides compared with controls. Our findings support a protective role for T cells against Delta breakthrough infection.

Omicron BA.1/BA.2 infections in triple-vaccinated individuals enhance a diverse repertoire of mucosal and blood immune responses (preprint)

Pronounced immune escape by the SARS-CoV-2 Omicron variant has resulted in large numbers of individuals with hybrid immunity, generated through a combination of vaccination and infection. Based primarily on circulating neutralizing antibody (NAb) data, concerns have been raised that omicron breakthrough infections in triple-vaccinated individuals result in poor induction of omicron-specific immunity, and that a history of prior SARS-CoV-2 in particular is associated with profound immune dampening. Taking a broader and comprehensive approach, we characterized mucosal and blood immunity to both spike and non-spike antigens following BA.1/BA.2 infections in triple mRNA-vaccinated individuals, with and without a history of previous SARS-CoV-2 infection. We find that the majority of individuals increase BA.1/BA.2/BA.5-specific NAb following infection, but confirm that the magnitude of increase and post-omicron titres are indeed higher in those who were infection-naive. In contrast, significant increases in nasal antibody responses are seen regardless of prior infection history, including neutralizing activity against BA.5 spike. Spike-specific T cells increase only in infection-naive vaccinees; however, post-omicron T cell responses are still significantly higher in previously-infected individuals, who appear to have maximally induced responses with a CD8+ phenotype of high cytotoxic potential after their 3rd mRNA vaccine dose. Antibody and T cell responses to non-spike antigens also increase significantly regardless of prior infection status, with a boost seen in previously-infected individuals to immunity primed by their first infection. These findings suggest that hybrid immunity induced by omicron breakthrough infections is highly dynamic, complex, and compartmentalised, with significant immune enhancement that can help protect against COVID-19 caused by future omicron variants.

Evaluation of QuantiFERON SARS-CoV-2 interferon-γ release assay following SARS-CoV-2 infection and vaccination (preprint)

Background: T cells are important in preventing severe disease from SARS-CoV-2, but scalable and field-adaptable alternatives to expert T cell assays are needed. The interferon-gamma release assay QuantiFERON platform was developed to detect T cell responses to SARS-CoV-2 from whole blood with relatively basic equipment and flexibility of processing timelines. Methods: 48 participants with different infection and vaccination backgrounds were recruited. Whole blood samples were analysed using the QuantiFERON SARS-CoV-2 assay in parallel with the well-established Protective Immunity from T Cells in Healthcare workers (PITCH) ELISpot, which can evaluate spike-specific T cell responses. Aims: The primary aims of this cross-sectional observational cohort study were to establish if the QuantiFERON SARS-Co-V-2 assay could discern differences between specified groups and to assess the sensitivity of the assay compared to the PITCH ELISpot. Findings: The QuantiFERON SARS-CoV-2 distinguished acutely infected individuals (12-21 days post positive PCR) from naive individuals (p< 0.0001) with 100% sensitivity and specificity for SARS-CoV-2 T cells, whilst the PITCH ELISpot had reduced sensitivity (62.5%) for the acute infection group. Sensitivity with QuantiFERON for previous infection was 12.5% (172-444 days post positive test) and was inferior to the PITCH ELISpot (75%). Although the QuantiFERON assay could discern differences between unvaccinated and vaccinated individuals (55-166 days since second vaccination), the latter also had reduced sensitivity (55.5%) compared to the PITCH ELISpot (66.6%). Conclusion: The QuantiFERON SARS-CoV-2 assay showed potential as a T cell evaluation tool soon after SARS-CoV-2 infection but has lower sensitivity for use in reliable evaluation of vaccination or more distant infection.

Characterisation of SARS-CoV-2 genomic variations in response to molnupiravir treatment in the AGILE Phase IIa clinical trial. (preprint)

Molnupiravir is an antiviral approved for treating COVID-19, which is thought to drive lethal error catastrophe. How this drug-induced mechanism of action impacts the emergence of resistance mutations is unclear. AGILE Candidate Specific Trial (CST)-2 is a phase IIa trial randomising 180 adult outpatients with SARS-COV-2 infection within five days of symptom onset to molnupiravir or placebo, with rich serial sampling of nasopharyngeal swabs over 29 days. Viral sequences, that passed genome quality control criteria, from subjects who received molnupiravir (n=59) or a placebo (n=65) were analysed by high-throughput amplicon sequencing. We found evidence that molnupiravir significantly increased the transition/transversion frequency in SARS-CoV-2 in patients, a hallmark of molnupiravir treatment. Over the course of treatment, no consistent, accumulated mutations were identified in either arm.

Evolution of long-term hybrid immunity in healthcare workers after different COVID-19 vaccination regimens: a longitudinal observational cohort study (preprint)

Both infection and vaccination, alone or in combination, generate antibody and T cell responses against SARS-CoV-2. However, the maintenance of such responses - and hence protection from disease - requires careful characterisation. In a large prospective study of UK healthcare workers (PITCH, within the larger SIREN study) we previously observed that prior infection impacted strongly on subsequent cellular and humoral immunity induced after long and short dosing intervals of BNT162b2 (Pfizer/BioNTech) vaccination. Here, we report longer follow up of 684 HCWs in this cohort over 6-9 months following two doses of BNT162b2 or AZ1222 (Oxford/AstraZeneca) vaccination and following a subsequent BNT162b2 booster vaccination. We make three important observations: Firstly, the dynamics of humoral and cellular responses differ; binding and neutralising antibodies declined whereas T and B cell responses were better maintained after the second vaccine dose. Secondly, vaccine boosting restored IgG levels to post second dose levels and broadened neutralising activity against variants of concern including omicron BA.1, alongside further boosting of T cell responses. Thirdly, prior infection maintained its impact driving larger T cell responses compared to never infected people, including after the third dose. In conclusion, the maintenance of T cell responses in time and against variants of concern may account for continued protection against severe disease.

Statistical analysis plan for the INHALEd nebulised unfractionated HEParin for the treatment of hospitalised patients with COVID-19 (INHALE-HEP) meta-trial (preprint)

The INHALE-HEP meta-trial is a prospective collaborative individual participant data meta-analysis of randomised controlled trials and early phase studies, to evaluate whether inhaled nebulised UFH in hospitalised patients with COVID-19 who do not require immediate invasive mechanical ventilation, significantly reduces intubation (or death, for patients who died before intubation) at day 28 compared to standard care alone. Objective: In keeping with best practice and with the published protocol, a pre-specified statistical analysis plan has been described and made public before completion of patient recruitment and data collection into the INHALE-HEP meta-trial. Methods: Our statistical analysis plan was designed by the INHALE-HEP executive committee and statisticians and approved by the INHALE-HEP steering committee. We reviewed the data collected as specified in the meta-trial protocol and collected in individual contributing studies. We present information pertaining to data collection, pre-specified subgroups, and study outcomes. Primary and secondary outcomes are defined, and additional subgroup analyses of pre-defined variables are described. Results: We have described our methods for presenting the trial profile and baseline characteristics, as well as our Bayesian approach to monitoring and meta-analysing individual patient data, outcomes and adverse events. All analyses will follow the intention-to-treat principle, considering all participants in the treatment group to which they were assigned, except for cases lost to follow-up or withdrawn. Conclusion: To minimise analytical bias, we have developed a statistical analysis plan and made this available to the public domain before completion of patient recruitment and data collection into the INHALE-HEP meta-trial.

Rapid selection of P323L in the SARS-CoV-2 polymerase (NSP12) in humans and non-human primate models and confers a large plaque phenotype (preprint)

The mutational landscape of SARS-CoV-2 varies at both the dominant viral genome sequence and minor genomic variant population. An early change associated with transmissibility was the D614G substitution in the spike protein. This appeared to be accompanied by a P323L substitution in the viral polymerase (NSP12), but this latter change was not under strong selective pressure. Investigation of P323L/D614G changes in the human population showed rapid emergence during the containment phase and early surge phase of wave 1 in the UK. This rapid substitution was from minor genomic variants to become part of the dominant viral genome sequence. A rapid emergence of 323L but not 614G was observed in a non-human primate model of COVID-19 using a starting virus with P323 and D614 in the dominant genome sequence and 323L and 614G in the minor variant population. In cell culture, a recombinant virus with 323L in NSP12 had a larger plaque size than the same recombinant virus with P323. These data suggest that it may be possible to predict the emergence of a new variant based on tracking the distribution and frequency of minor variant genomes at a population level, rather than just focusing on providing information on the dominant viral genome sequence e.g., consensus level reporting. The ability to predict an emerging variant of SARS-CoV-2 in the global landscape may aid in the evaluation of medical countermeasures and non-pharmaceutical interventions.

Poor Antibody Responses to SARS-CoV-2 Infection or Vaccination Are Associated With High Re-Infection Rates in Haemodialysis and Renal Transplant Patients (preprint)

Background: Patients with end-stage renal disease (ESRD) are vulnerable to SARS-CoV-2 infection and mount poor antibody responses to standard vaccines. We addressed whether ESRD patients could mount immune responses that protected against re-infection following natural SARS-CoV-2 infection or 2-dose vaccination.Methods: Haemodialysis (HD and renal transplant patients were recruited following SARS-CoV-2 infection (n=46) or before SARS-CoV-2 vaccination (n=94). SARS-CoV-2 IgG responses, surrogate neutralising antibody (NAb) titres to wildtype and VOCs, T cell responses and viral sequencing in the vaccine-naïve convalescent cohort were serially assessed following infection. Surrogate NAb titres were measured pre-vaccination and 33 days after 2nd vaccine. Incidence of breakthrough infection was assessed 180 days following 1st vaccination. Findings: 22% of vaccine-naive HD (n=9/36) and transplant patients (n=1/10) demonstrated PCR-positive re-infection (RI) at median 212 days (IQR 140-239) post 1st infection. Prior to RI episodes, RI patients demonstrated poor IgG Spike and RBD responses which were equivalent to levels in pre-pandemic sera (median RI titres: Spike 187 AU/ml, IQR 143-3432, p=0.96; RBD 145 AU/ml, IQR 85-938, p>0.99), unlike patients who developed a single infection only (SI) when compared to pre-pandemic sera (median SI titres: Spike 22826 AU/ml, IQR 1255-63811, p<0.0001; RBD 9588 AU/ml, IQR 270-21616, p=0.001). IgG Spike and RBD titres increased following RI compared to pre-pandemic sera (median RI titres: Spike 22611 AU/ml, IQR 4488-75509, p=0.0006; RBD 6354 AU/ml, IQR 1671-20962, p=0.01). T cell analysis revealed no differences between RI and SI cohorts. Following 2-dose vaccination, 5% of the HD cohort who received AZD1222 (n=3/61) developed breakthrough infection at 6 months following 1st vaccination, unlike those who received BNT162b2 (n=0/16). AZD1222-vaccinated, infection-naïve (I-N) HD patients (n=32) and immunosuppressed transplant recipients (n=17) made poor NAb responses to wildtype, alpha, beta and gamma when compared to infection-experienced (I-E) HD patients (n=29) (I-N vs I-E HD wildtype p<0.0001, alpha p=0.0007, beta p<0.0001, gamma p=0.002). NAb responses improved with BNT162b2 vaccination (n=16); RI patients mounted larger NAb responses to AZD1222 vaccination than SI patients (wildtype p=0.01, alpha p=0.02, beta p<0.02). Interpretation: ESRD patients are highly susceptible to SARS-CoV-2 re-infection, or breakthrough infection following vaccination, associated with poor protective antibody responses. SARS-CoV-2-specific IgG and surrogate NAb responses increase with repeated exposure (infection experience and/or vaccination) in patients who survive infections. Our findings support the case for specific booster regimens in such immune-incompetent patients. Funding Information: Oxford Transplant Foundation, Oxfordshire Health Services Research Committee, UK Department of Health and Social Care, Huo Family Foundation, NIHR (COV19-RECPLAS), UK Coronavirus Immunology Consortium, NIHR Oxford Biomedical Research Centre, WT109965MA.Declaration of Interests: We declare no competing interestsEthics Approval Statement: Haemodialysis (HD) and transplant cohorts: In this prospective, observational cohort study, HD and transplant patients within Oxford University Hospitals NHS Foundation Trust(OUH) were recruited under Oxford Radcliffe Biobank approved studies, “Biomarkers to stratify risk in Renal Transplant Recipients and Dialysis Patients with Covid-19” (ref: ORB 20/A056), and “Immunological responses to COVID-19 vaccines in transplant and haemodialysis patients” (ref: ORB 21/A014). The Oxford Radcliffe Biobank has a favorable ethics opinion from the South Central Oxford Committee C (REC: 19/SC/0173). Healthcare Worker cohort (HC, PITCH study): PITCH is a sub-study of the SIREN study which was approved by the Berkshire Research Ethics Committee, Health Research 250 Authority (IRAS ID 284460, REC reference 20/SC/0230), with PITCH recognised as a sub-study on 2 December 2020. SIREN is registered with ISRCTN (Trial ID:252 ISRCTN11041050)The study was conducted in compliance with all relevant ethical regulations for work with human participants, and according to the principles of the Declaration of Helsinki (2008) and the International Conference on Harmonization (ICH) Good Clinical Practice (GCP) guidelines. Written informed consent was obtained for all patients enrolled in the study.

Durability of ChAdOx1 nCov-19 (AZD1222) vaccination in people living with HIV - responses to SARS-CoV-2, variants of concern and circulating coronaviruses (preprint)

Duration of protection from SARS-CoV-2 infection in people with HIV (PWH) following vaccination is unclear. In a sub-study of the phase 2/3 the COV002 trial (NCT04400838), 54 HIV positive male participants on antiretroviral therapy (undetectable viral loads, CD4+ T cells >350 cells/ul) received two doses of ChAdOx1 nCoV-19 (AZD1222) 4-6 weeks apart and were followed for 6 months. Responses to vaccination were determined by serology (IgG ELISA and MesoScale Discovery (MSD)), neutralisation, ACE-2 inhibition, gamma interferon ELISpot, activation-induced marker (AIM) assay and T cell proliferation. We show that 6 months after vaccination the majority of measurable immune responses were greater than pre-vaccination baseline, but with evidence of a decline in both humoral and cell mediated immunity. There was, however, no significant difference compared to a cohort of HIV-uninfected individuals vaccinated with the same regimen. Responses to the variants of concern were detectable, although were lower than wild type. Pre-existing cross-reactive T cell responses to SARS-CoV-2 spike were associated with greater post-vaccine immunity and correlated with prior exposure to beta coronaviruses. These data support the on-going policy to vaccinate PWH against SARS-CoV-2, and underpin the need for long-term monitoring of responses after vaccination.

A potent SARS-CoV-2 neutralising nanobody shows therapeutic efficacy in the Syrian golden hamster model of COVID-19 (preprint)

SARS-CoV-2 remains a global threat to human health particularly as escape mutants emerge. There is an unmet need for effective treatments against COVID-19 for which neutralizing single domain antibodies (nanobodies) have significant potential. Their small size and stability mean that nanobodies are compatible with respiratory administration. We report four nanobodies (C5, H3, C1, F2) engineered as homotrimers with pmolar affinity for the receptor binding domain (RBD) of the SARS-CoV-2 spike protein. Crystal structures show C5 and H3 overlap the ACE2 epitope, whilst C1 and F2 bind to a different epitope. Cryo Electron Microscopy shows C5 binding results in an all down arrangement of the Spike protein. C1, H3 and C5 all neutralize the Victoria strain, and the highly transmissible Alpha (B.1.1.7 first identified in Kent, UK) strain and C1 also neutralizes the Beta (B.1.35, first identified in South Africa). Administration of C5-trimer via the respiratory route showed potent therapeutic efficacy in the Syrian hamster model of COVID-19 and separately effective prophylaxis. The molecule was similarly potent by intraperitoneal injection.

Fatal COVID-19 outcomes are associated with an antibody response targeting epitopes shared with endemic coronaviruses (preprint)

It is unclear whether prior endemic coronavirus infections affect COVID-19 severity. Here, we show that in cases of fatal COVID-19, antibody responses to the SARS-COV-2 spike are directed against epitopes shared with endemic beta-coronaviruses in the S2 subunit of the SARS-CoV-2 spike protein. This immune response is associated with the compromised production of a de novo SARS-CoV-2 spike response among individuals with fatal COVID-19 outcomes.

Metagenomic Identification of a New Sarbecovirus from Horseshoe Bats in Europe (preprint)

The source of the COVID-19 pandemic is unknown, but the natural host of the progenitor sarbecovirus is thought to be Asian horseshoe (rhinolophid) bats. We identified and sequenced a novel sarbecovirus (RhGB01) from a British horseshoe bat, at the western extreme of the rhinolophid range. Our results extend both the geographic and species ranges of sarbecoviruses and suggest their presence throughout the horseshoe bat distribution. Within the receptor binding domain, but excluding the receptor binding motif, RhGB01 has a 77% (SARS-CoV-2) and 81% (SARS-CoV) amino acid homology. While apparently lacking hACE2 binding ability, and hence unlikely to be zoonotic without mutation, RhGB01 presents opportunity for SARS-CoV-2 and other sarbecovirus homologous recombination. Our findings highlight that the natural distribution of sarbecoviruses and opportunities for recombination through intermediate host co-infection are underestimated. Preventing transmission of SARS-CoV-2 to bats is critical with the current global mass vaccination campaign against this virus.

Sequence analysis of SARS-CoV-2 in nasopharyngeal samples from patients with COVID-19 illustrates population variation and diverse phenotypes, placing the in vitro growth properties of B.1.1.7 and B.1.351 lineage viruses in context. (preprint)

New variants of SARS-CoV-2 are continuing to emerge and dominate the regional and global sequence landscapes. Several variants have been labelled as Variants of Concern (VOCs) because of perceptions or evidence that these may have a transmission advantage, increased risk of morbidly and/or mortality or immune evasion in the context of prior infection or vaccination. Placing the VOCs in context and also the underlying variability of SARS-CoV-2 is essential in understanding virus evolution and selection pressures. Sequences of SARS-CoV-2 in nasopharyngeal swabs from hospitalised patients in the UK were determined and virus isolated. The data indicated the virus existed as a population with a consensus level and non-synonymous changes at a minor variant. For example, viruses containing the nsp12 P323L variation from the Wuhan reference sequence, contained minor variants at the position including P and F and other amino acids. These populations were generally preserved when isolates were amplified in cell culture. In order to place VOCs B.1.1.7 (the UK Kent variant) and B.1.351 (the South African variant) in context their growth was compared to a spread of other clinical isolates. The data indicated that the growth in cell culture of the B.1.1.7 VOC was no different from other variants, suggesting that its apparent transmission advantage was not down to replicating more quickly. Growth of B.1.351 was towards the higher end of the variants. Overall, the study suggested that studying the biology of SARS-CoV-2 is complicated by population dynamics and that these need to be considered with new variants.

B.1.1.7 became the dominant variant in Lebanon (preprint)

ABSTRACT Recently, a new variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) designated VOC 202012/01 (or B.1.1.7 lineage) has become highly prevalent in several countries, after first being described in the United Kingdom (UK). Its rate of transmission has been estimated to be increased compared to other lineages. In the present study, we show the emergence, dominance and the rapid spread of the B.1.1.7 lineage in Lebanon.

Identification and quantification of SARS-CoV-2 leader subgenomic mRNA gene junctions in nasopharyngeal samples shows phasic transcription in animal models of COVID-19 and aberrant pattens in humans (preprint)

Introduction: SARS-CoV-2 has a complex strategy for the transcription of viral subgenomic mRNAs (sgmRNAs), which are targets for nucleic acid diagnostics. Each of these sgRNAs has a unique 5 sequence, the leader-transcriptional regulatory sequence gene junction (leader-TRS-junction), that can be identified using sequencing. Results: High resolution sequencing has been used to investigate the biology of SARS-CoV-2 and the host response in cell culture models and from clinical samples. LeTRS, a bioinformatics tool, was developed to identify leader-TRS-junctions and be used as a proxy to quantify sgmRNAs for understanding virus biology. This was tested on published datasets and clinical samples from patients and longitudinal samples from animal models with COVID-19. Discussion: LeTRS identified known leader-TRS-junctions and identified novel species that were common across different species. The data indicated multi-phasic abundance of sgmRNAs in two different animal models, with spikes in sgmRNA abundance reflected in human samples, and therefore has implications for transmission models and nucleic acid-based diagnostics.

One or two dose regimen of the SARS-CoV-2 synthetic DNA vaccine INO-4800 protects against respiratory tract disease burden in nonhuman primate challenge model (preprint)

Safe and effective vaccines will provide essential medical countermeasures to tackle the COVID-19 pandemic. Here, we evaluate the safety, immunogenicity and efficacy of the intradermal delivery of INO-4800, a synthetic DNA vaccine candidate encoding the SARS-CoV-2 spike protein in the rhesus macaque model. Single and 2 dose vaccination regimens were evaluated. Vaccination induces both binding and neutralizing antibodies, along with IFN-γ-producing T cells against SARS-CoV-2. Upon administration of a high viral dose (5 x 106 pfu) via the intranasal and intratracheal routes we observe significantly reduced virus load in the lung and throat, in the vaccinated animals compared to controls. 2 doses of INO-4800 is associated with more robust vaccine-induced immune responses and improved viral protection. Importantly, histopathological examination of lung tissue provides no indication of vaccine-enhanced disease following SARS-CoV-2 challenge in INO-4800 immunized animals. This vaccine candidate is currently under clinical evaluation as a 2 dose regimen.

ChAdOx1 nCoV-19 protection against SARS-CoV-2 in rhesus macaque and ferret challenge models (preprint)

Vaccines against SARS-CoV-2 are urgently required. Here we report detailed immune profiling after ChAdOx1 nCoV-19 (AZD1222) and subsequent challenge in two animal models of SARS-CoV-2 mediated disease. We demonstrate in rhesus macaques the lung pathology caused by SARS-CoV-2 mediated pneumonia is reduced by prior vaccination with ChAdOx1 nCoV-19 which induced neutralising antibody responses after a single intramuscular administration. In a second animal model, ferrets, ChAdOx1 nCoV-19 reduced both virus shedding and lung pathology. Antibody titers were boosted by a second dose. Data from these challenge models and the detailed immune profiling, support the continued clinical evaluation of ChAdOx1 nCoV-19.

Changes in SARS-CoV-2 before the peak in each country, producing unique variants. (preprint)

The second and third waves of coronavirus disease 2019 (COVID-19) have caused problems worldwide. Those are often thought to have resulted from people's carelessness or people not following restrictions, but in reality, the cause remains unclear. Here, using an objective analytical method, we present the changes in the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus causing COVID-19 over time. The virus has mutated in three major directions, with three groups remaining to date. The basic structure of the groups was completed by April and shared across all continents. However, the virus continued to mutate independently in each country after the borders were closed. In particular, the virus mutated before the occurrence of a second or third peak. It seems that the mutations conferred higher infectivity to the virus, because of which the virus overcame previously effective protections. Currently, each country may possess such a unique stronger variant, which may cause another peak in other countries. These viruses could also serve as sources of mutations by exchanging parts of the genome. Such mutations could create a variant with superior infectivity.

The SARS-CoV-2 spike protein disrupts the cooperative function of human cardiac pericytes - endothelial cells through CD147 receptor-mediated signalling: a potential non-infective mechanism of COVID-19 microvascular disease (preprint)

Background: Severe coronavirus disease 2019 (COVID-19) manifests as a life-threatening microvascular syndrome. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) uses primarily the capsid spike (S) protein to engage with its receptors and infect host cells. To date, it is still not known if the S protein alone, without the other viral elements, is able to trigger vascular cell signalling and provoke cell dysfunction. Methods: We investigated the effects of the recombinant, stabilised S protein on primary human cardiac pericytes (PCs) signalling and function. Endpoints included cell viability, proliferation, migration, cooperation with endothelial cells (ECs) in angiogenesis assays, and release of pro-inflammatory cytokines. Adopting a blocking strategy against the S protein receptors ACE2 and CD147, we explored which receptor mediates the S protein signalling in PCs. Findings: We show, for the first time, that the recombinant S protein alone elicits functional alterations in cardiac PCs. This was documented as: (1) increased migration, (2) reduced ability to support EC network formation on Matrigel, (3) secretion of pro-inflammatory molecules typically involved in the cytokine storm; and (4) production of pro-apoptotic factors responsible for EC death. Furthermore, the S protein stimulates the phosphorylation/activation of the extracellular signal-regulated kinase 1/2 (ERK1/2) through the CD147 receptor, but not ACE2, in cardiac PCs. Accordingly, the neutralization of CD147, using a blocking antibody, prevented the activation of ERK1/2 and partially rescued the PC function in the presence of the S protein. Interpretation: Our findings suggest the new, intriguing hypothesis that the S protein may elicit vascular cell dysfunction, potentially amplifying, or perpetuating, the damage caused by the whole coronavirus. This mechanism may have clinical and therapeutic implication.