Assessment of the Biological Impact of SARS-CoV-2 Genetic Variation Using an Authentic Virus Neutralisation Assay with Convalescent Plasma, Vaccinee Sera, and Standard Reagents.

In the summer of 2020, it became clear that the genetic composition of SARS-CoV-2 was changing rapidly. This was highlighted by the rapid emergence of the D614G mutation at that time. In the autumn of 2020, the project entitled "Agility" was initiated with funding from the Coalition for Epidemic Preparedness Innovations (CEPI) to assess new variants of SARS-CoV-2. The project was designed to reach out and intercept swabs containing live variant viruses in order to generate highly characterised master and working stocks, and to assess the biological consequences of the rapid genetic changes using both in vitro and in vivo approaches. Since November 2020, a total of 21 variants have been acquired and tested against either a panel of convalescent sera from early in the pandemic, and/or a panel of plasma from triple-vaccinated participants. A pattern of continuous evolution of SARS-CoV-2 has been revealed. Sequential characterisation of the most globally significant variants available to us, generated in real-time, indicated that the most recent Omicron variants appear to have evolved in a manner that avoids immunological recognition by convalescent plasma from the era of the ancestral virus when analysed in an authentic virus neutralisation assay.

Intrinsic host susceptibility among multiple species to intranasal SARS-CoV-2 identifies diverse virological, biodistribution and pathological outcomes.

SARS-CoV-2 exhibits a diverse host species range with variable outcomes, enabling differential host susceptibility studies to assess suitability for pre-clinical countermeasure and pathogenesis studies. Baseline virological, molecular and pathological outcomes were determined among multiple species-one Old World non-human primate (NHP) species (cynomolgus macaques), two New World NHP species (red-bellied tamarins; common marmosets) and Syrian hamsters-following single-dose, atraumatic intranasal administration of SARS-CoV-2/Victoria-01. After serial sacrifice 2, 10 and 28-days post-infection (dpi), hamsters and cynomolgus macaques displayed differential virus biodistribution across respiratory, gastrointestinal and cardiovascular systems. Uniquely, New World tamarins, unlike marmosets, exhibited high levels of acute upper airway infection, infectious virus recovery associated with mild lung pathology representing a host previously unrecognized as susceptible to SARS-CoV-2. Across all species, lung pathology was identified post-clearance of virus shedding (antigen/RNA), with an association of virus particles within replication organelles in lung sections analysed by electron microscopy. Disrupted cell ultrastructure and lung architecture, including abnormal morphology of mitochondria 10-28 dpi, represented on-going pathophysiological consequences of SARS-CoV-2 in predominantly asymptomatic hosts. Infection kinetics and host pathology comparators using standardized methodologies enables model selection to bridge differential outcomes within upper and lower respiratory tracts and elucidate longer-term consequences of asymptomatic SARS-CoV-2 infection.