Simultaneous analysis of antigen-specific B and T cells after SARS-CoV-2 infection and vaccination (preprint)

Conventional methods for quantifying and phenotyping antigen-specific lymphocytes can rapidly deplete irreplaceable specimens. This is due to the fact that antigen-specific T and B cells have historically been analyzed in independent assays each requiring millions of cells. A technique that facilitates the simultaneous detection of antigen-specific T and B cells would allow for more thorough immune profiling with significantly reduced sample requirements. To this end, we developed the B And T cell Tandem Lymphocyte Evaluation (BATTLE) assay, which allows for the simultaneous identification of SARS-CoV-2 Spike reactive T and B cells using an optimized Activation Induced Marker (AIM) T cell assay and dual-color B cell antigen probes. Using this assay, we demonstrate that antigen-specific B and T cell subsets can be identified simultaneously using conventional flow cytometry platforms and provide insight into the differential effects of mRNA vaccination on B and T cell populations following natural SARS-CoV-2 infection.

Assessing unused residual Pfizer-BioNTech Covid-19 vaccine: a community observational study (preprint)

Worldwide morbidity and mortality associated with Covid-19 are severe and ongoing. The Pfizer-BioNTech vaccine is said to be up to 95% effective against severe disease or death. We were able to demonstrate that an additional 9.8% of COVID-19 vaccine doses could theoretically be given if the residual vaccine within the reconstituted Pfizer vials after six doses are extracted were used. This could be achieved by aseptically combining this excess vaccine from multiple vials to achieve full 0.3ml doses. MethodsAn observational study was conducted in April, 2021, at a mass vaccine site run by a community volunteer organization on Bainbridge Island, Washington. We measured the amount of Pfizer-BioNTech COVID-19 vaccine that was left in 172 vials after six doses had been withdrawn per Centers for Disease Control (CDC) protocol. ResultsA total of 30.68 ml of leftover vaccine was measured and discarded as medical waste. 1,036 doses were given from these vials. An extra 102 doses theoretically could have been given using the residual vaccine in the vials. This would have resulted in 9.8% additional doses of COVID-19 vaccine without requiring new vials. ConclusionThe ability to combine solution from reconstituted Pfizer vaccine vials to minimize waste and obtain additional doses of vaccine could result in an increase in the number of individuals that could be vaccinated worldwide without additional cost. Further studies to validate our findings are warranted. Clinical trials to study the feasibility, safety and efficacy of protocols using this excess vaccine should be considered.

Divergent trajectories of antiviral memory after SARS-Cov-2 infection (preprint)

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is normally controlled by effective host immunity including innate, humoral and cellular responses. However, the trajectories and correlates of acquired immunity, and the capacity of memory responses months after infection to neutralise variants of concern - which has important public health implications - is not fully understood. To address this, we studied a cohort of 78 UK healthcare workers who presented in April to June 2020 with symptomatic PCR-confirmed infection or who tested positive during an asymptomatic screening programme and tracked virus-specific B and T cell responses longitudinally at 5-6 time points each over 6 months, prior to vaccination. We observed a highly variable range of responses, some of which - T cell interferon-gamma (IFN-γ) ELISpot, N-specific antibody waned over time across the cohort, while others (spike-specific antibody, B cell memory ELISpot) were stable. In such cohorts, antiviral antibody has been linked to protection against re-infection. We used integrative analysis and a machine-learning approach (SIMON - Sequential Iterative Modeling Over Night) to explore this heterogeneity and to identify predictors of sustained immune responses. Hierarchical clustering defined a group of high and low antibody responders, which showed stability over time regardless of clinical presentation. These antibody responses correlated with IFN-γ ELISpot measures of T cell immunity and represent a subgroup of patients with a robust trajectory for longer term immunity. Importantly, this immune-phenotype associates with higher levels of neutralising antibodies not only against the infecting (Victoria) strain but also against variants B.1.1.7 (alpha) and B.1.351 (beta). Overall memory responses to SARS-CoV-2 show distinct trajectories following early priming, that may define subsequent protection against infection and severe disease from novel variants.

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.

Relieving ICU Pressures and Reducing Mortality in COVID-19: A Framework for Early Intervention (preprint)

Delayed presentation of COVID-19 pneumonia leads to higher mortality and greater use of healthcare resources. Early identification of progressive COVID-19 cases saves lives, reduces the pressure on healthcare services, and facilitates the easing of social restrictions. To improve the earlier detection of COVID-19 pneumonia in the community we provide a narrative review of current evidence examining the clinical parameters associated with disease progression. We explore the symptoms that may suggest COVID-19 progression; the timing of deterioration; the utility of basic observations; the value of post-exertion oxygen saturations, and the use of CRP to monitor disease progression. We go on to provide recommendations for monitoring the COVID-19 patient in the community and discuss thresholds for further assessment.

Prophylactic intranasal administration of a TLR2 agonist reduces upper respiratory tract viral shedding in a SARS-CoV-2 challenge ferret model (preprint)

Respiratory viruses such as coronaviruses represent major ongoing global threats, causing epidemics and pandemics with huge economic burden. Rapid spread of virus through populations poses an enormous challenge for outbreak control. Like all respiratory viruses, the most recent novel human coronavirus SARS-CoV-2, initiates infection in the upper respiratory tract (URT). Infected individuals are often asymptomatic, yet highly infectious and readily transmit virus. A therapy that restricts initial replication in the URT has the potential to prevent progression of severe lower respiratory tract disease as well as limiting person-to-person transmission. We show that prophylactic intra-nasal administration of the TLR2/6 agonist INNA-051 in a SARS-CoV-2 ferret infection model effectively reduces levels of viral RNA in the nose and throat. The results of our study support clinical development of a therapy based on prophylactic TLR2/6 innate immune activation in the URT to reduce SARS-CoV-2 transmission and provide protection against COVID-19.

Structural and Functional Comparison of SARS-CoV-2-Spike Receptor Binding Domain Produced in Pichia pastoris and Mammalian Cells (preprint)

The yeast Pichia pastoris is a cost-effective and easily scalable system for recombinant protein production. In this work we compared the conformation of the receptor binding domain (RBD) from SARS-CoV-2 Spike protein expressed in P. pastoris and in the well established HEK-293T mammalian cell system. RBD obtained from both yeast and mammalian cells was properly folded, as indicated by UV-absorption, circular dichroism and tryptophan fluorescence. They also had similar stability, as indicated by temperature-induced unfolding (observed Tm were 50 {degrees}C and 52 {degrees}C for RBD produced in P. pastoris and HEK-293T cells, respectively). Moreover, the stability of both variants was similarly reduced when the ionic strength was increased, in agreement with a computational analysis predicting that a set of ionic interactions may stabilize RBD structure. Further characterization by HPLC, size-exclusion chromatography and mass spectrometry revealed a higher heterogeneity of RBD expressed in P. pastoris relative to that produced in HEK-293T cells, which disappeared after enzymatic removal of glycans. The production of RBD in P. pastoris was scaled-up in a bioreactor, with yields above 45 mg/L of 90% pure protein, thus potentially allowing large scale immunizations to produce neutralizing antibodies, as well as the large scale production of serological tests for SARS-CoV-2.

Fixed single-cell RNA sequencing for understanding virus infection and host response (preprint)

Single-cell RNA sequencing studies requiring intracellular protein staining, rare-cell sorting, or pathogen inactivation are severely limited because current high-throughput methods are incompatible with paraformaldehyde treatment, a very common and simple tissue/cell fixation and preservation technique. Here we present FD-seq, a high-throughput method for droplet-based RNA sequencing of paraformaldehyde-fixed, stained and sorted single-cells. We used FD-seq to address two important questions in virology. First, by analyzing a rare population of cells supporting lytic reactivation of the human tumor virus KSHV, we identified TMEM119 as a host factor that mediates reactivation. Second, we studied the transcriptome of lung cells infected with the 2 coronavirus OC43, which causes the common cold and also serves as a safer model pathogen for SARS-CoV-2. We found that pro-inflammatory pathways are primarily upregulated in abortively-infected or uninfected bystander cells, which are exposed to the virus but fail to express high level of viral genes. FD-seq is suitable for characterizing rare cell populations of interest, for studying high-containment biological samples after inactivation, and for integrating intracellular phenotypic with transcriptomic information.

Mutational signatures in countries affected by SARS-CoV-2: Implications in host-pathogen interactome (preprint)

We are in the midst of the third severe coronavirus outbreak caused by SARS-CoV-2 with unprecedented health and socio-economic consequences due to the COVID-19. Globally, the major thrust of scientific efforts has shifted to the design of potent vaccine and anti-viral candidates. Earlier genome analyses have shown global dominance of some mutations purportedly indicative of similar infectivity and transmissibility of SARS-CoV-2 worldwide. Using high-quality large dataset of 25k whole-genome sequences, we show emergence of new cluster of mutations as result of geographic evolution of SARS-CoV-2 in local population ({greater than or equal to}10%) of different nations. Using statistical analysis, we observe that these mutations have either significantly co-occurred in globally dominant strains or have shown mutual exclusivity in other cases. These mutations potentially modulate structural stability of proteins, some of which forms part of SARS-CoV-2-human interactome. The high confidence druggable host proteins are also up-regulated during SARS-CoV-2 infection. Mutations occurring in potential hot-spot regions within likely T-cell and B-cell epitopes or in proteins as part of host-viral interactome, could hamper vaccine or drug efficacy in local population. Overall, our study provides comprehensive view of emerging geo-clonal mutations which would aid researchers to understand and develop effective countermeasures in the current crisis.

Comparison of Rhesus and Cynomolgus macaques as an authentic model for COVID-19. (preprint)

A novel coronavirus, SARS-CoV-2, has been identified as the causative agent of the current COVID-19 pandemic. Animal models, and in particular non-human primates, are essential to understand the pathogenesis of emerging diseases and to the safety and efficacy of novel vaccines and therapeutics. Here, we show that SARS-CoV-2 replicates in the upper and lower respiratory tract and causes pulmonary lesions in both rhesus and cynomolgus macaques, resembling the mild clinical cases of COVID-19 in humans. Immune responses against SARS-CoV-2 were also similar in both species and equivalent to those reported in milder infections and convalescent human patients. Importantly, we have devised a new method for lung histopathology scoring that will provide a metric to enable clearer decision making for this key endpoint. In contrast to prior publications, in which rhesus are accepted to be the optimal study species, we provide convincing evidence that both macaque species authentically represent mild to moderate forms of COVID-19 observed in the majority of the human population and both species should be used to evaluate the safety and efficacy of novel and repurposed interventions against SARS-CoV-2. Accessing cynomolgus macaques will greatly alleviate the pressures on current rhesus stocks.

Dose-dependent response to infection with SARS-CoV-2 in the ferret model: evidence of protection to re-challenge (preprint)

In December 2019 an outbreak of coronavirus disease (COVID-19) emerged in Wuhan, China. The causative agent was subsequently identified and named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which rapidly spread worldwide causing a pandemic. Currently there are no licensed vaccines or therapeutics available against SARS-CoV-2 but numerous candidate vaccines are in development and repurposed drugs are being tested in the clinic. There is a vital need for authentic COVID-19 animal models to further our understanding of pathogenesis and viral spread in addition to pre-clinical evaluation of candidate interventions. Here we report a dose titration study of SARS-CoV-2 to determine the most suitable infectious dose to use in the ferret model. We show that a high (5x106 pfu) and medium (5x104 pfu) dose of SARS-CoV-2 induces consistent upper respiratory tract (URT) viral RNA shedding in both groups of six challenged animals, whilst a low dose (5x102 pfu) resulted in only one of six displaying signs of URT viral RNA replication. The URT shedding lasted up to 21 days in the high dose animals with intermittent positive signal from day 14. Sequential culls revealed distinct pathological signs of mild multifocal bronchopneumonia in approximately 5-15% of the lung, observed on day 3 in high and medium dosed animals, with presence of mild broncho-interstitial pneumonia on day 7 onwards. No obvious elevated temperature or signs of coughing or dyspnoea were observed although animals did present with a consistent post-viral fatigue lasting from day 9-14 in the medium and high dose groups. After virus shedding ceased, re-challenged ferrets were shown to be fully protected from acute lung pathology. The endpoints of URT viral RNA replication in addition to distinct lung pathology and post viral fatigue were observed most consistently in the high dose group. This ferret model of SARS-CoV-2 infection presents a mild clinical disease (as displayed by 80% of patients infected with SARS-CoV-2). In addition, intermittent viral shedding on days 14-21 parallel observations reported in a minority of clinical cases.