Use of Human Lung Tissue Models for Screening of Drugs Against SARS-CoV-2 Infection (preprint)

The repurposing of licenced drugs for use against COVID-19 is one of the most rapid ways to develop new and alternative therapeutic options to manage the ongoing pandemic. Given the approximately 8,000 licenced compounds available from Compounds Australia that can be screened, this paper demonstrates the utility of commercially-available ex vivo/3D airway and alveolar tissue models. These models are a closer representation of in vivo studies compared to in vitro models, but retain the benefits of rapid in vitro screening for drug efficacy. We demonstrate that several existing drugs appear to show anti-SARS-CoV-2 activity against both Delta and Omicron Variants of Concern in the airway model. In particular, fluvoxamine, as well as aprepitant, everolimus, and sirolimus have virus reduction efficacy comparable to the current standard of care (remdesivir, molnupiravir, nirmatrelvir). Whilst these results are encouraging, further testing and efficacy studies are required before clinical use can be considered.

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.