Make way for the “recombinant” variant XE

Omicron’s family continues to grow. After BA.2, the majority in Quebec, the “recombinant” variant XE has been discovered in several countries, including Canada. There is nothing abnormal about its appearance, say the experts consulted by The Press. But this is not good news. Here’s why.

Posted at 6:00 a.m.

Suzanne Colpron

Suzanne Colpron
The Press

What is a recombinant variant?

It is the result of the fusion of two existing strains. This phenomenon occurs when a person is infected by two lineages at the same time. ” It happens. It’s already arrived. It will continue to happen, ”says André Veillette, immunologist at the Montreal Clinical Research Institute. Indeed, when viruses attack a cell, they can exchange parts of their genome and pick up mutations from each other. “There are many viruses that use the recombination method”, specifies Alain Lamarre, professor-researcher specializing in immunology and virology at the National Institute for Scientific Research.

What do we know about XE?

It comes from the mixture of two strains of the lineage of Omicron, BA.1 and BA.2. The XE attracts attention because it circulates a lot in England, where there are 1125 cases. Other countries, including Canada, have also detected it on their territory. “The more you will have transmission in the population, the more likely you will be that a person will be co-infected by different lineages”, specifies Inès Levade, specialized scientific adviser at the Laboratoire de santé publique du Québec and coordinator of the committee of experts. on the genomic monitoring of SARS-CoV-2. All known recombinant variants have a name whose first letter is X. The first is called XA and the last is XT.


Inès Levade, Specialized Scientific Advisor at the Quebec Public Health Laboratory

Does the XE circulate in Quebec?

No. At least, we have not yet detected it with certainty. But five cases of another recombinant, which strongly resembles XE, have been identified in Quebec. Only one case of XE has been found in Canada to date.

How do we go about identifying these new forms of the coronavirus?

A program called Pangolin, run by a research group, assigns them a name based on the number of cases reported worldwide.

Is there anything to worry about?

Yes. According to the scientists, these variants can become more transmissible or more resistant to vaccines. “The problem with recombination is that it allows you to have lots of new mutations at once,” explains Inès Levade, from the Laboratoire de santé publique du Québec. “It actually allows the virus to make much larger combinations of mutations much faster. It can change its epidemiological and clinical characteristics. So it’s something to watch out for. »


André Veillette, immunologist at the Montreal Clinical Research Institute

Is XE more transmissible?

Yes, it would be 10% more contagious than BA.2. “Does it cause more severe illnesses? It’s not clear, says Mr. Veillette. Should it be more vaccine resistant than BA.1 or BA.2? I doubt it, but it’s not clear either. »

Could he dethrone BA.2?

The odds are low. “But it is possible if it is introduced into poorly protected populations,” says Alain Lamarre. Two types of variants can supplant BA.2. “There are variants that replicate faster and infect faster, those that will win obstacle races, notes André Veillette. And escape variants that bypass the immune system, like Omicron, but even more effectively. Inès Levade recalls that when Delta was the dominant strain, it was expected that the worrying new subline would come from Delta. But it was Omicron, which had a very high number of mutations, which created the surprise.


Alain Lamarre, professor-researcher specializing in immunology and virology at the National Institute for Scientific Research

What precautions should be taken?

Epidemiological surveillance and sequencing of the virus must be carried out. In Quebec, about 700 PCR tests are sequenced per week to identify the lines that are circulating, says Leavening. “We also sequence travelers, in collaboration with the federal government, to see what comes in from other countries,” she adds.

What to expect next?

“People who hoped that we would get out of it quickly will be disappointed, answers Alain Lamarre. We are stuck with the virus for a long time and there is no easy way out, because it manages to infect vaccinated people, even triple vaccinated people, and even those who have had recent COVID. I think it’s going to take another vaccine. We have reached the limit of the effectiveness of these vaccines, which are too different from the circulating strains. »

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