Chiron, the sub-variant that escapes antibodies
Chiron, the daughter of Centaurus, also descends from Omicron 2 but has even more mutations. How widespread is this sub-variant and how well is it able to evade antibodies?
Chiron, as the leader of the centaurs guarding the violent in Dante's Inferno , is the particular name attributed to the sub-variant BA.2.75.2 .
It is also considered the daughter of Centaurus (BA.2.75) , a sub-variant of Omicron, because just like this one it has several mutations compared to Omicron 2, which not only make it a mix but also attract attention since, according to research published in The Lancet Infectious Diseases , it has "a wide capacity to escape from neutralizing antibodies".
I STUDY
The authors of the research, from the Karolinska Institutet, Federal Polytechnic Eth of Zurich and Imperial College of London, tried to understand whether the virus, in its evolved form, was able to escape the antibodies we have available, in the blood or with respect to some monoclonal antibodies.
THE BLOOD ANALYSIS
To learn more about Chiron, the researchers analyzed the serum of some blood donors in Stockholm taking into consideration three time frames.
The samples of the first group dated back to November 2021, that is, before the emergence of the Omicron variant. Those of the second were from April 2022, following a wave of Covid infections (caused first by Omicron 1 and then by Omicron 2) and after the introduction of third doses of the vaccine. And finally, the last batch was from September 2022, after the release of Omicron 5.
THE RESULTS
The analyzes showed that, in all three time frames, the serum antibodies had a “significantly lower” neutralization capacity of BA.2.75.2 than all the other variants tested. This means that Chiron appears to be able to better escape immunity.
As for monoclonal antibodies, the sub-variant completely escapes Cilgavimab and the combination of Cilgavimab and Tixagevimab (known as Evusheld by AstraZeneca), while Sotrovimab has a low neutralizing capacity.
BEBTELOVIMAB, THE ONLY EFFECTIVE MONOCLONAL
The only monoclonal antibody that really gave positive results was Eli Lilly 's Bebtelovimab, which neutralized all tested variants "in a powerful way". As early as August , Eric Topol, American scientist director of the Scripps Research Translational Institute in La Jolla in California, reported that it was the only monoclonal available that was effective against Omicron 5.
However, the Food and Drug Admistration (Fda) approved it in February for emergency use but specified that "this is not the therapy of choice, and should only be used if other treatments are not accessible. or clinically appropriate ". In Italy, it was not approved.
HOW IS IT DIFFERENT FROM CENTAURUS
Centaurus has 9 new mutations on the spike protein and 5 outside it, the most concerning mutation being G446S.
Chiron, compared to the 'mother', has 3 additional mutations on the spike protein – R346T, F486S and D1199N – which make it even more resistant than Centaurus.
HOW DIFFUSED IS IT
Omicron has not yet been ousted by any other variant because its sub-variants have become predominant, especially Omicron 5.
However, even Omicron 2 (from which Centaurus and Chiron descend) continues to be monitored by the World Health Organization (WHO) because, as recalled by the latest flash survey of the Higher Institute of Health (Iss) updated on 4 October, it is slightly increasing precisely because of these two sub-variants.
WHERE IT IS DIFFUSED
At the end of September, Time said, the strain was reported in 47 countries and 39 American states, where it still represents less than 1% of cases.
This is a machine translation from Italian language of a post published on Start Magazine at the URL https://www.startmag.it/sanita/chiron-la-sottovariante-che-sfugge-agli-anticorpi/ on Tue, 18 Oct 2022 11:43:00 +0000.