BA. 275.2: New Omicron subvariant can evade almost all protective antibodies: study

By Alexandra Mae Jones, Editor

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Toronto, Ontario (CTV Network) – A new study from Swedish researchers suggests that the world could see a dramatic increase in COVID-19 cases this winter due to new mutations creating variants that could evade immunity from vaccines or previous infections.

The BA.2.75.2 variant, one of the latest developments in the Omicron lineage of COVID-19, can evade the majority of neutralizing antibodies in the blood, according to the study, and is also resistant to several antiviral treatments. of monoclonal antibodies that have been created. to care for COVID-19 patients.

The mutations that make this possible in BA.2.75.2 appear in other variants as the virus continues to grow and evolve, researchers say – and it’s still unclear whether bivalent vaccines will provide more immunity. robust against this particular variant.

The study, published Thursday in the Lancet Infectious Diseases, looked at three subvariants of Omicron and found that although vaccines still offer some protection against them, some variants are better than others at evading antibodies.

“Although antibody immunity did not completely disappear, BA.2.75.2 showed far more dramatic resistance than the variants we have previously studied, largely due to two mutations in the binding domain. spike protein receptor,” Ben Murrell, corresponding author and assistant professor in the Department of Microbiology, Tumor, and Cell Biology at the Karolinska Institutet, said in a press release.

Currently, the BA.5 is one of the most dominant variants in North America, according to the study. According to the most recent data from the Public Health Agency of Canada, BA.5 and BA.4 currently dominate in Canada. Additionally, the World Health Organization monitors other variants, including BA.2.75.

BA.2.75.2 is the last mutation of BA.2.75. Previous research has shown that BA.2.75 isn’t as good at evading antibodies as BA.5, but BA.2.75.2 has additional mutations that made researchers sit up and take notice.

Several specific mutations within the BA.2.75.2 variant had already been associated with a higher escape percentage in previous variants, according to the study. But BA.2.75.2 combines mutations in a way that could potentially make it much more infectious.

A diagram accompanying the search highlighted structural differences in the receptor binding domain between BA.2 and BA.2.75, as well as differences between BA.2.75 and BA.2.75.2 to show how this variant continued to mutate.

And the researchers say BA.2.75.2 is a far cry from the final form of COVID-19.

“We now know that this is just a constellation of emerging variants with similar mutations that will likely come to dominate in the near future,” Murrell said. “We should expect infections to increase this winter.”

To examine the variant in a real-world setting, the researchers used blood samples from approximately 75 donors who were collected at three intervals: in 2021 before the emergence of Omicron and twice in 2022 after an increase in cases. and deployment of the third dose of vaccine.

“At all three time points, serum antibody neutralization of BA.2.75.2 was significantly lower than all other variants tested,” the study says.

They observed that two mutations that distinguished BA.2.75.2 from BA.2.75 “contributed to the significantly improved resistance” of the new variant.

The researchers also examined whether a variety of preclinical monoclonal antibody treatments available in Sweden were able to neutralize the BA.2.75.2, BA.4.6 and BA.2.10.4 variants.

These treatments are primarily used for those who are at high risk of developing severe disease if they contract COVID-19.

One treatment called cilgavimab was effective against BA.2.10.4, while another called sotrovimab showed poor results against BA.2.75.2 and BA.2.10.4, with better results against BA.4.6.

Only one treatment – bebtelovimab – was able to “potently” neutralize BA.2.75.2 and the other variants, the researchers found.

Bebtelovimab, which was developed by a Vancouver lab in conjunction with an American company, has been approved for use in the United States, but not yet in Canada.

The statement noted that scientists still don’t know if this variant will increase winter hospitalizations, but evidence suggests that if BA.2.75.2 starts circulating more, these regions could definitely see more cases due to increased capacity. of this variant to conquer. the protective shield from vaccines or previous infection.

Researchers hope that new bivalent vaccines, which have been modified to include protection against early Omicron variants, might provide stronger antibodies to block these new variants, but scientists don’t yet have enough data.

“We expect them to be beneficial, but we don’t know by how much yet,” Murrell said.

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