A study comparing four variants of SARS-CoV-2 shows how the Omicron variant is adept at entering cells and escaping neutralisation from existing vaccines or prior infection, potentially contributing to the variant’s high transmissibility. Published in journal ‘Proceedings of the National Academy of Sciences’ (PNAS) on July 19, the study suggests that Omicron mutations increase the infectivity of SARS-CoV-2 virus-like particles and decrease antibody neutralisation. Researchers examined the virus using virus-like particles (VLPs) that imitate the SARS-CoV-2 proteins’ structural characteristics. VLPs of the B.1, B.1.1, Delta, and Omicron variants were evaluated against antisera samples from 38 COVID-19 survivors, both vaccinated and unvaccinated, by Jennifer Doudna, Melanie Ott, and colleagues.

In contrast to the original B.1 strain, antisera from the same individual who had received two vaccinations were up to 15 times less effective at neutralising Omicron in vitro. Nevertheless, the in vitro neutralising activity against Omicron was significantly increased in sera from participants who had received a third mRNA vaccine within 16 to 21 days. The in vitro neutralising potency of four currently available monoclonal antibody therapies—casirivimab, imdevimab, sotrovimab, and bebtelovimab—was then assessed by the authors. They discovered that only bebtelovimab was significantly effective against Omicron. According to the findings, the authors hypothesise that Omicron may be particularly contagious in part because it is a harder strain to neutralise. The researchers also found an existing monoclonal antibody that might in vitro neutralise the variation.

Effective vaccine and treatment development depends on an understanding of the molecular factors that influence severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral fitness. The advent of viral variations such as Delta and Omicron highlighted the need to evaluate infectivity and antibody neutralisation, although research on intact SARS-CoV-2 is being conducted slowly due to biosafety level 3 handling requirements.