Highly Thermotolerant SARS-CoV-2 Vaccine Elicits Neutralising Antibodies Against Delta and Omicron in Mice (preprint)

As the existing vaccines do not completely prevent infections or community transmission of the coronavirus disease-19 (COVID-19), there is an unmet need for vaccines that can better combat severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) variants of concern (VOC) and also eliminate cold chain requirements. We show that highly thermo-tolerant monomeric and trimeric receptor binding domain derivatives that can withstand 100C for 90 minutes and 37C for four weeks elicit high antibody titres in mice that received prime-boost immunization on Days 0 and 21; and that these antibodies neutralize SARS-CoV-2 variants VIC31 (containing the Spike D614G mutation), Delta and Omicron (BA.1.1) VOC. Compared to VIC31, there was an average 14.4-fold reduction in neutralization against BA.1.1 for the three monomeric, and 16.5-fold re-duction for the three trimeric antigen-adjuvant combinations; the corresponding values against Delta were 2.5 and 3.0. Our findings suggest that monomeric formulations are suitable for the upcoming Phase I human clinical trials, and that there is potential for improving efficacy with vaccine matching to improve responses against emerging variants. These findings are consistent with in silico modelling and AlphaFold predictions which show that while oligomeric presentation can be generally beneficial, it can make important epitopes inaccessible.

At least three doses of leading vaccines essential for neutralization of SARS-CoV-2 Omicron variant (preprint)

Plasma samples taken at different time points from donors who received either AstraZeneca (Vaxzevria) or Pfizer (Comirnaty) or Moderna (Spikevax) coronavirus disease-19 (COVID-19) vaccine were assessed in virus neutralization assays against Delta and Omicron variants of concern and a reference isolate (VIC31). With the Pfizer vaccine there was 6-8 fold reduction in 50% neutralizing antibody titres (NT50) against Delta and VIC31 at 6 months compared to 2 weeks after the second dose; followed by 25-fold increase at 2 weeks after the third dose. Neutralisation of Omicron was only consistently observed 2 weeks after the third dose, with most samples having titres below the limit of detection at earlier timepoints. Moderna results were similar to Pfizer at 2 weeks after the second dose, while the titres for AstraZeneca samples derived from older donors were 7-fold lower against VIC31 and below the limit of detection against Delta and Omicron. Age and gender were not found to significantly impact our results. These observations indicate that vaccine matching may be needed, and that at least a third dose of these vaccines is necessary to generate sufficient neutralising antibodies against emerging variants of concern, especially Omicron, amidst the challenges of ensuring vaccine equity worldwide.

Cooccurrence of N501Y, P681R and other key mutations in SARS-CoV-2 Spike (preprint)

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has produced five variants of concern (VOC) to date. The important Spike mutation N501Y is common to Alpha, Beta, Gamma and Omicron VOC, while the P681R is key to the spread of Delta. We have analysed circa 4.2 million SARS-CoV-2 genome sequences from the largest repository Global Initiative on Sharing All Influenza Data (GISAID) and demonstrated that these two mutations have cooccurred on the Spike D614G mutation background at least 3,678 times from 17 October 2020 to 1 November 2021. In contrast, the Y501-H681 combination, which is common to Alpha and Omicron VOC, is present in circa 1.1 million entries. Two-thirds of the 3,678 cooccurrences were in France, Turkey or US (East Coast), and the rest across 57 other countries. 55.5% and 4.6% of the cooccurrences were Alpha Q.4 and Gamma P.1.8 sub-lineages acquiring the P681R; 10.7% and 3.8% were Delta B.1.617.2 lineage and AY.33 sub-lineage acquiring the N501Y; the remaining 10.2% were in other variants. Despite the selective advantages individually conferred by N501Y and P681R, the Y501-R681 combination counterintuitively did not outcompete other variants in every instance we have examined. While this is a relief to worldwide public health efforts, in vitro and in vivo studies are urgently required in the absence of a strong in silico explanation for this phenomenon. This study demonstrates a pipeline to analyse combinations of key mutations from public domain information in a systematic manner and provide early warnings of spread.

But Mouse, you are not alone: On some severe acute respiratory syndrome coronavirus 2 variants infecting mice (preprint)

In silico predictions combined with in vitro, in vivo and in situ observations collectively suggest that mouse adaptation of the SARS-CoV-2 virus requires an aromatic substitution in position 501 or position 498 (but not both) of the spike proteins receptor binding domain. This effect could be enhanced by mutations in positions 417, 484 and 493 (especially K417N, E484K, Q493K and Q493R), and to a lesser extent by mutations in positions 486 and 499 (such as F486L and P499T). Such enhancements due to more favourable binding interactions with residues on the complementary angiotensin-converting enzyme 2 (ACE2) interface, are however, unlikely to sustain mouse infectivity on their own based on theoretical and experimental evidence to date. Our current understanding thus points to the Alpha, Beta and Gamma variants of concern infecting mice, while Delta and Delta Plus lack a similar biomolecular basis to do so. This paper identifies a list of countries where local field surveillance of mice is encouraged because they may have come in contact with humans who had the virus with adaptive mutation(s). It also provides a systematic methodology to analyze the potential for other animal reservoirs and their likely locations.

Live virus neutralisation of the 501Y.V1 and 501Y.V2 SARS-CoV-2 variants following INO-4800 vaccination of ferrets (preprint)

The ongoing COVID-19 pandemic has resulted in significant global morbidity and mortality on a scale similar to the influenza pandemic of 1918. Over the course of the last few months, a number of SARS-CoV-2 variants have been identified against which vaccine-induced immune responses may be less effective. These variants-of-concern have garnered significant attention in the media, with discussion around their impact on the future of the pandemic and the ability of leading COVID-19 vaccines to protect against them effectively. To address concerns about emerging SARS-CoV-2 variants affecting vaccine-induced immunity, we investigated the neutralisation of representative G614, 501Y.V1 and 501Y.V2 virus isolates using sera from ferrets that had received prime-boost doses of the DNA vaccine, INO-4800. Neutralisation titres against G614 and 501Y.V1 were comparable, but titres against the 501Y.V2 variant were approximately 4-fold lower, similar to results reported with other nucleic acid vaccines and supported by in silico biomolecular modelling. The results confirm that the vaccine-induced neutralising antibodies generated by INO-4800 remain effective against current variants-of-concern, albeit with lower neutralisation titres against 501Y.V2 similar to other leading nucleic acid-based vaccines.