New Omicron sublineage shows extensive escape from neutralising antibodies

"This BA.2.75.2 sub-variant evolved from the earlier BA.2.75 and is hardly affected by neutralising antibodies and resistant to some antiviral monoclonal antibody drugs (cilgavimab, cilgavimab+tixagevimab)," writes Dobson.

Currently, the various sub-variants of omicron are dominant worldwide, as this variant has already mutated several times, but not once has coronavirus become a virus causing severe symptoms since the emergence of omicron.

It is not yet known whether BA.2.75.2 causes more severe disease than the currently dominant variants, but it certainly seems to be more effective in overwhelming the body's existing defences.

SARS-CoV-2 omicron sublineage BA.2.75 expanded rapidly in parts of the world, but it has so far not outcompeted BA.5 globally, note the authors of the study published in The Lancet.

"Despite similar geometric mean neutralising titres (GMT) to BA.5, BA.2.75 remained sensitive to classes of antibodies that BA.5 had escaped, suggesting scope for antibody evasion. The emergence of a sublineage of BA.2.75 carrying additional mutations R346T, F486S, and D1199N, growing rapidly, suggested more extensive escape from neutralising antibodies," they said.

They reported the sensitivity of emerging omicron sublineages BA.2.75.2, BA.4.6, and BA.2.10.4 to neutralisation by a panel of clinically relevant and preclinical monoclonal antibodies and by serum from blood donated in Stockholm, Sweden.

BA.2.75.2 and BA.4.6 both show complete escape from cilgavimab and a combination of cilgavimab and tixagevimab, whereas BA.2.10.4 retains some sensitivity to cilgavimab.

Sotrovimab exhibits similarly low potency against BA.5, BA.2.75.2, and BA.2.10.4, with some reduction against BA.4.6. Bebtelovimab still potently neutralises all variants they tested.

“While antibody immunity is not completely gone, BA.2.75.2 exhibited far more dramatic resistance than variants we’ve previously studied, largely driven by two mutations in the receptor binding domain of the spike protein,” said corresponding author Ben Murrell in a statement.

Since its discovery earlier this fall, BA.2.75.2 has been reported in several countries, but thankfully only makes up a small number of total cases. At present, it accounts for just 1.4 percent of US cases, according to the Centers for Disease Control and Prevention, iflscience.com reported.

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

Murrell added.

However, whether or not this anticipated rise in infections will affect the number of hospitalizations remains unclear. It is also not known whether the updated COVID vaccines, modified to protect against early Omicron variants, will be able to protect against BA.2.75.2 and other emerging variants.

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

Cover photo: Getty Images