New Omicron subvariant XBB could be more infectious, better at evading immunity, study finds
- It’s the product of two strains merging, which has not been the case in previous coronavirus variants, Japanese team says
- Their results suggest XBB is highly transmissible and resistant to the immune response from being previously infected
This could result in a higher transmission rate and immunity escape, researchers from the University of Tokyo, Hokkaido University and Kyoto University said in a paper posted to preprint server bioRxiv on Tuesday.
Their investigation suggests that XBB is the first documented case of a Sars-CoV-2 variant increasing its fitness among humans through recombination – rather than through single mutations.
The researchers found that subvariants of Omicron – which emerged at the end of 2021 – had gone through convergent evolution, with most substitutions occurring on the spike protein. That protein is located outside the coronavirus and allows it to penetrate host cells and cause infection.
Some substitutions to the spike protein increase its ability to bind to the ACE2 – or angiotensin-converting enzyme 2 – receptor. Others help it to evade immunity from vaccination or previous infection.
But XBB is different, according to the Japanese study. The subvariant – which is expected to become dominant in some countries such as the United States – “emerged as a recombinant lineage between the second generation Omicron variants”, lead author Professor Kei Sato, of the University of Tokyo, wrote in the paper.
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