In a new study published in Nature, researchers found that mutations of omicron variant change how the virus infects cells and reduce the virus’s sensitivity to therapeutic and vaccine-elicited antibodies.
Booster doses of mRNA vaccines improve neutralization, and the antiviral drugs remdesevir and molnupiravir retains efficacy against omicron.
Previous studies have shown that the omicron variant carries approximately 36 mutations in the spike protein, the part of the virus that facilitates entry into host cells.
In the current study, to understand how omicron may respond to existing COVID-19 treatments, researchers incubated both live and pseudoviral particles with clinically approved antibodies to analyze the interactions between the antibodies and the omicron spike.
They find that casivirimab and imdevimab, which have been shown to be particularly effective at neutralizing delta when used together, lose all neutralizing activity against omicron when used either individually or in combination.
The antiviral agents remdesivir and molnupiravir are shown to have similar activity against delta and omicron.
To determine the effectiveness of existing vaccines against omicron, researchers produced virus particles expressing the spike protein from omicron or delta.
They then exposed them to serum from individuals vaccinated with either the Pfizer–BioNTech or Oxford–AstraZeneca vaccine.
They observed at least a 10-fold reduction in the neutralization of omicron compared to delta after two doses of either vaccine, with further waning in response associated with increasing time since the second dose.
Neutralization of omicron was not detectable for the majority of individuals who had received two doses of Oxford–AstraZeneca.
Further sera from the same groups, but boosted with Pfizer–BioNTech as a third dose, was shown to increase neutralization.
Similar results were observed for two doses of Pfizer–BioNTech in experiments using live viruses.
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The study was conducted by Bo Meng et al, the publication title is Altered TMPRSS2 usage by SARS-CoV-2 Omicron impacts tropism and fusogenicity.
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