New year, new variant. Just as scientists were becoming familiar with the alphabetic soup of SARS-CoV-2 variants circulating around the world (its BQ. 1. 1, CH. 1. 1 and BF. 7), one lineage reaches the top, thanks to a new specific. mutation.
Subvariant XBB. 1. 5 now accounts for about 28% of COVID-19 cases in the United States, according to projections from the U. S. Centers for Disease Control and Prevention (CDC). It is expanding globally in the U. S. in Atlanta, Georgia. In the northeastern United States, it turned out to have temporarily outgrown the collection of other immunity-avoidance variants that were expected to circulate side-by-side this winter.
“It’s almost going to dominate the world. I can’t locate a single competitor now. Everything else is time for none,” says Yunlong Cao, an immunologist at Peking University in Beijing, whose team is reading the XBB. 1. 5 houses in the lab. .
Scientists warn that the effect of XBB. 1. 5, in the U. S. In the U. S. and beyond, it’s still far from clear. exposure to past waves of COVID-19 and vaccines, especially recent boosters for those at peak threat of severe illness.
However, even if XBB. 1. 5 does not cause giant waves of COVID-19, it will be vital to trace the lineage in depth, according to the researchers. Additional evolutionary gains.
As the call suggests, XBB. 1. 5 is a branch of a variant of SARS-CoV-2 called XBB. This lineage is a recombinant of two descendants of the BA. 2 lineage that began to develop in early 2022; BA. 2 itself is a branch of Omicron. The XBB spike protein has a number of mutations that make the variant able to evade antibodies. In Singapore.
Observers of the variant detected XBB. 1. 5 in late 2022, thanks to a rarely observed amino acid substitution, called F486P, in the spike protein. Experiments in Cao’s lab suggest that the mutation enhances the variant’s ability to bind to the human ACE2 receptor. , which SARS-CoV-2 uses to invade cells1. Importantly, the mutation does not appear to erode XBB’s ability to evade antibodies. The effects were published on bioRxiv’s preprint server on January five and have not yet been peer-reviewed. “XBB fears the ACE2 link,” Cao says, and the F486P update in XBB. 1. 5 is helping to overcome this deficiency.
The dating between a variant’s ability to bind to ACE2 and its transmissibility isn’t entirely clear, says Jesse Bloom, an evolutionary virologist at Fred Hutchinson Cancer Center in Seattle, Washington. But for XBB. 1. 5, “F486P turns out to have pushed it,” allowing the virus to spread,” he says.
The CDC estimates that XBB. 1. 5 is the maximum non-unusual variant of the moment in the United States, comprising 28% of cases nationally and more than 70% in the Northeast (see “New Year, New Variant”). Moritz Gerstung, a computational biologist at the German Cancer Research Center in Heidelberg, estimates that cases of the variant are doubling every week in the United States, and a little slower in other countries where the variant has emerged. This is comparable to the rate at which the BQ. 1 and BQ. 1. 1 variants were higher in September 2022, but slower than previous Omicron waves. “The propagation of XBB. 1. 5 is still incredibly fast,” says Gerstung.
What’s unclear is whether this expansion will be sustained or whether the variant will lead to particular infections, Gerstung adds. BQ. 1 and BQ. 1. 1 seemed to be in a position to generate significant waves, only to lose strength in Europe and the North. América. Si the same is true with XBB. 1. 5, it is possible that the lineage will end up quietly replacing other variants in some countries without causing a large backlog of cases.
Jennifer Surtees, a biochemist at the University at Buffalo in New York, wonders if researchers are overestimating the expansion of XBB. 1. 5 in the northeastern United States. you have yet to realize the meteoric accumulation in the XBB. 1. 5 genomes that New York labs are recording.
Assessing the effect of XBB. 1. 5 may not be straightforward, due to declining COVID-19 testing, Surtees adds. “I think we’re literally flying blind right now. We have no idea how many instances actually exist.
Tulio de Oliveira, a bioinformatician at Stellenbosch University in South Africa, believes researchers deserve to take a look at hospital cases and other measures of disease severity to better measure the effect of XBB. 1. 5. Factors such as a bloodless snap in the northeastern U. S. The U. S. and Christmas gatherings may partly explain the obvious rise in the variant, he says. “I think a lot of scientists draw conclusions and predictions very early and with very little data. “
One thing researchers can agree on is that XBB. 1. 5, like its predecessor XBB, is a master of immune evasion. It carries many spike mutations that attenuate the potency of antibodies produced through vaccination and infection, adding earlier strains of Omicron. Building bivalent vaccines increase levels of antibodies capable of blocking XBB infection (and XBB. 1. 5) in laboratory tests2,3, but not much, Cao notes.
Throughout 2022, the researchers, along with Cao, observed that Omicron’s lines stumbled upon a succession of mutations that prevented antibodies in the viral spike protein that allowed new lines to triumph over immunity acquired through vaccines and past waves. XBB. 1. 5 is much more transmissible than other variants in flux thanks to the addition of the F486P mutation, so lately there is little evolutionary stress in the lineage to replace more, Cao says.
But as overall immunity to the subvariant strengthens, XBB. 1. 5 may not stop, he says. “We’re going to see a lot of new mutations that we’ve never noticed before. “
Nature 613, 222-223 (2023)
doi: https://doi. org/10. 1038/d41586-023-00014-3
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