The SARS-CoV-2 protein ORF3c is a mitochondrial modulator of innate immunity (preprint)

The SARS-CoV-2 genome encodes a multitude of accessory proteins. Using comparative genomic approaches, an additional accessory protein, ORF3c, has been predicted to be encoded within the ORF3a sgmRNA. Expression of ORF3c during infection has been confirmed independently by ribosome profiling. Despite ORF3c also being present in the 2002-2003 SARS-CoV, its function has remained unexplored. Here we show that ORF3c localises to mitochondria during infection, where it inhibits innate immunity by restricting IFN-β production, but not NF-κB activation or JAK-STAT signalling downstream of type I IFN stimulation. We find that ORF3c acts after stimulation with cytoplasmic RNA helicases RIG-I or MDA5 or adaptor protein MAVS, but not after TRIF, TBK1 or phospho-IRF3 stimulation. ORF3c co-immunoprecipitates with the antiviral proteins MAVS and PGAM5 and induces MAVS cleavage by caspase-3. Together, these data provide insight into an uncharacterised mechanism of innate immune evasion by this important human pathogen.

Gene delivery of a single,structurally engineered Coronavirus vaccine antigen elicits SARS-CoV-2 Omicron and pan-Sarbecovirus neutralisation (preprint)

Of the coronaviruses that have caused zoonotic spill overs in past two decades, the diverse group of beta-coronaviruses (β-CoVs) represent the greatest threats. Towards achieving broad vaccine protection from these viruses, vaccines composed of multiple antigens, each capable of eliciting broad neutralising responses across a subgroup will be required. Utilising a novel platform for selecting immune optimized, structurally engineered antigens capable of eliciting protective responses across a group of related viruses, we demonstrate proof-concept against the greater sarbecoviruses sub-genus with a single antigen structure. From an array of phylogenetically informed antigen structures displaying different broad neutralising epitopes, synthetic genes expressing these were selected based on broad immune responses in BALB/C mice. Improved protection against the Delta variant was further observed in K18-hACE2 mice on boosting with the lead designs of mice primed by an approved COVID-19 vaccine. Immunogenicity of the lead vaccine antigen and breadth of neutralisation against the SARS-CoV, SARS-CoV-2, WIV16, and RaTG13 was confirmed in guinea pigs using needleless intradermal immunisation. Immunogenicity was further confirmed in rabbits with GMP manufactured DNA immunogen. Notably, given the increasing number of mutations acquired by SARS-CoV-2 variants of concern (VOCs), the rabbit sera were tested for the capacity to neutralise VOCs - Beta, Gamma, Delta, as well as the most diverse Omicron variant. The consistent neutralising ability of the vaccine sera against the emerging VOCs validate broad specificity of the vaccine design. Here, we demonstrate proof-of-concept of this Digitally Immune Optimised, Selected vaccine (DIOSvax) antigen pipeline for the in vivo selection of single nucleic acid-based immunogens. Such gene-based antigens can be readily delivered alone or in combination, and seamlessly scaled with vaccine delivery modalities such as viral vector or mRNA-based vaccines.

Endemic Seasonal Coronavirus Neutralisation and COVID-19 severity (preprint)

The virus SARS-CoV-2, responsible for the global COVID-19 pandemic, spread rapidly around the world causing high morbidity and mortality because humans have no pre-existing immunity. However, there are four known, endemic seasonal coronaviruses in humans (HCoVs) and whether antibodies for these HCoVs play a role in severity of COVID-19 disease has generated a lot of interest. Of these seasonal viruses NL63 is of particular interest as it uses the same cell entry receptor as SARS-CoV-2.We use functional, neutralising assays to investigate cross reactive antibodies and their relationship with COVID-19 severity. We analysed neutralisation of SARS-CoV-2, NL63, HKU1, and 229E in 38 COVID-19 patients and 62 healthcare workers, and a further 182 samples to specifically study the relationship between SARS-CoV-2 and NL63.We found that although HCoV neutralisation was very common there was little evidence that these antibodies neutralised SARS-CoV-2. Despite no evidence in cross neutralisation, levels of NL63 neutralisating antibodies become elevated after exposure to SARS-CoV-2 through infection or following vaccination.

Breadth of neutralising antibody responses to SARS-CoV-2 variants of concern is augmented by vaccination following prior infection: studies in UK healthcare workers and immunodeficient patients (preprint)

Approximately 75% of the UK population has received only one dose of a 2-dose COVID-19 vaccine regime in the face of circulating SARS-CoV-2 Variants of Concern (VOCs). We aimed to determine the levels of vaccine-induced neutralising antibodies to SARS-CoV-2 variants B.1.1.7, B.1.351 and P.1. To do so, we undertook a single-centre cross-sectional study of health care workers (HCWs) and outpatients with immunodeficiencies (IDP) based at the same critical care tertiary NHS Trust, following a single dose of either BNT162b2 or AZD1222 vaccines. Data revealed low neutralising antibodies (nAbs) in IDPs, with only 5% and 3% showing detectable neutralisation of B.1.1.7 and B.1.351, respectively. In contrast, healthy HCWs without a prior SARS-CoV-2 infection demonstrated a wide range of nAb titres post-vaccination with responses significantly lower than HCWs with prior SARS-CoV-2 infection. Neutralisation of VOCs with the E484K mutation (B.1.351 and P.1) were consistently lower in HCWs in the absence of evidence of prior SARS-CoV-2 infection (p<0.001). Notably, in vaccinated HCWs with prior SARS-CoV-2 infection, there was a significant increase of neutralising titres post-vaccination to all variants, compared to their pre-vaccination neutralisation titres. This underscores the importance of vaccination to boost neutralising antibody breadth to VOCs, and also provides support for the hypothesis that repeated immunisations will boost protective immunity in individuals without prior SARS-CoV-2 exposure.

Towards Internationally standardised humoral Immune Correlates of Protection from SARS CoV 2 infection and COVID-19 disease (preprint)

Precision monitoring of antibody responses during the COVID-19 pandemic is increasingly important during large scale vaccine rollout and rise in prevalence of Severe Acute Respiratory Syndrome-related Coronavirus-2 (SARS-CoV-2) variants of concern (VOC). Equally important is defining Correlates of Protection (CoP) for SARS-CoV-2 infection and COVID-19 disease. Data from epidemiological studies and vaccine trials identified virus neutralising antibodies (Nab) and SARS-CoV-2 antigen-specific (notably RBD, and S) binding antibodies as candidate CoP. In this study, we used the World Health Organisation (WHO) international standard to benchmark neutralising antibody responses and a large panel of binding antibody assays to compare convalescent sera obtained from: a) COVID-19 patients; b) SARS-CoV-2 seropositive healthcare workers (HCW) and c) seronegative HCW. The ultimate aim of this study, was to identify biomarkers of humoral immunity that could be used as candidate CoP in internationally accepted unitage. Whenever suitable, the antibody levels of the samples studied were expressed in International Units (INU) for virus neutralisation assays or International Binding Antibody Units (BAU) for ELISA tests. In this work we used commercial and non-commercial antibody binding assays; a lateral flow test for detection of SARS-CoV-2-specific IgG / IgM; a high throughput multiplexed particle flow cytometry assay for SARS-CoV-2 Spike (S), Nucleocapsid (N) and Receptor Binding Domain (RBD) proteins); a multiplex antigen semi-automated immuno-blotting assay measuring IgM, IgA and IgG; a pseudotyped microneutralisation test (pMN) and electroporation-dependent neutralisation assay (EDNA). Our results indicate that overall, severe COVID-19 patients showed statistically significantly higher levels of SARS-CoV-2-specific neutralising antibodies (average 1029 IU/ml) than those observed in seropositive HCW with mild or asymptomatic infections (379 IU/ml) and that clinical severity scoring, based on WHO guidelines was tightly correlated with neutralisation and RBD / S binding assays. In addition, there was a positive correlation between severity, N-antibody assays and intracellular virus neutralisation.

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.

Critical care workers have lower seroprevalence of SARS-CoV-2 IgG compared with non-patient facing staff in first wave of COVID19. (preprint)

With the first 2020 surge of the COVID-19 pandemic, many health care workers (HCW) were re-deployed to critical care environments to support intensive care teams to look after high numbers of patients with severe COVID-19. There was considerable anxiety of increased risk of COVID19 for staff working in these environments. Using a multiplex platform to assess serum IgG responses to SARS-CoV-2 N, S and RBD proteins, and detailed symptom reporting, we screened over 500 HCW (25% of the total workforce) in a quaternary level hospital to explore the relationship between workplace and evidence of exposure to SARS-CoV-2. Whilst 45% of the cohort reported symptoms that they consider may have represented COVID-19, overall seroprevalence was 14% with anosmia and fever being the most discriminating symptoms for seropositive status. There was a significant difference in seropositive status between staff working in clinical and non-clinical roles (9% patient facing critical care, 15% patient facing non-critical care, 22% nonpatient facing). In the seropositive cohort, symptom severity increased with age for men and not for women. In contrast, there was no relationship between symptom severity and age or sex in the seronegative cohort reporting possible COVID-19 symptoms. Of the 12 staff screened PCR positive (10 symptomatic), 3 showed no evidence of seroconversion in convalescence. Conclusion: The current approach to Personal Protective Equipment (PPE) appears highly effective in protecting staff from patient acquired infection in the critical care environment including protecting staff managing interhospital transfers of COVID-19 patients. The relationship between seroconversion and disease severity in different demographics warrants further investigation. Longitudinally paired virological and serological surveillance, with symptom reporting are urgently required to better understand the role of antibody in the outcome of HCW exposure during subsequent waves of COVID-19 in health care environments.

A clinical MALDI-ToF Mass spectrometry assay for SARS-CoV-2: Rational design and multi-disciplinary team work. (preprint)

The COVID-19 pandemic caused by the SARS-CoV-2 Coronavirus has stretched national testing capacities to breaking points in almost all countries of the world. The need to rapidly screen vast numbers of a countrys population in order to control the spread of the infection is paramount. However, the logistical requirement for reagent supply (and associated cost) of RT-PCR based testing (the current front-line test) have been hugely problematic. Mass spectrometry-based methods using swab and gargle samples have been reported with promise, but have not approached the task from a systematic analysis of the entire diagnostic process. Here, the pipeline from sample processing, the biological characteristics of the pathogen in human biofluid, the downstream bio- and physical-chemistry and the all-important data processing with clinical interpretation and reporting, are carefully compiled into a single high throughput and reproducible rapid process. Utilizing MALDI-ToF mass spectrometric detection to viral envelope glycoproteins in a systems biology - multidisciplinary team approach, we have achieved a multifaceted clinical MALDI ToF MS screening test, primarily (but not limited to) SARS-CoV-2, with direct applicable to other future epidemics/pandemics that may arise. The clinical information generated not only includes SARS-CoV-2 Coronavirus detection - (Spike protein fragments S1, S2b, S2a peaks), but other respiratory viral infections detected as well as an assessment of generalised oral upper respiratory immune response (elevated total Ig light chain peak) and a measure of the viral immune response (elevated intensity of IgA heavy chain peak). The advantages of the method include; 1) ease of sampling, 2) speed of analysis, and much reduced cost of testing. These features reveal the diagnostic utility of MALDI-ToF mass spectrometry as a powerful and economically-attractive global solution. Abstract graphic O_FIG O_LINKSMALLFIG WIDTH=183 HEIGHT=200 SRC="FIGDIR/small/20176669v1_ufig1.gif" ALT="Figure 1"> View larger version (53K): org.highwire.dtl.DTLVardef@1b84899org.highwire.dtl.DTLVardef@1a665e7org.highwire.dtl.DTLVardef@16c3f49org.highwire.dtl.DTLVardef@1aee6de_HPS_FORMAT_FIGEXP M_FIG C_FIG