With the detection of an emerging Omicron sub-variant showing an alarming trend to avoid vaccine immunity, eyes are once again on COVID-19 cases. This sub-variant, called BA.2.75.2, can largely bypass neutralizing antibodies in the blood and resist several monoclonal antibody treatments, according to a new study from Sweden.
According to a statement by study author Ben Murrell, “Although antibody immunity was not completely lost, BA.2.75.2 exhibited much more dramatic resistance than the variants we previously examined, and was driven largely by two mutations in the spike protein’s receptor-binding domain.”
BA.2.75.2: The latest mutant of the BA.2.75 subvariant
BA.2.75.2 is identified as a subset of the Omicron variant and the most recent mutant of the BA.2.75 subvariant currently monitored by the World Health Organization. Since BA.2.75.2 was discovered earlier this fall, it has been reported in many countries, but only a small fraction of the total cases. Currently, it only accounts for 1.4 percent of U.S. cases, according to the U.S. Centers for Disease Control and Prevention.
The new research focused on three Omicron subvariants (BA.2.75.2, BA.4.6 and BA.2.10.4) and used serum samples from 75 individuals at three different time points: November 2021, April 2022, and late August/early September this year. .
“The neutralization of BA.2.75.2 by serum antibodies at the three time points was significantly lower than for all other variants tested,” the study authors wrote.
In fact, the subvariant was found to be more than six-fold less responsive to neutralizing antibodies than the currently dominant variant BA. The authors say this can be explained by two mutations that contribute to their “significantly improved resistance.”
The researchers also tested the sensitivity of the new subvariant to various monoclonal antibody therapies, namely antiviral therapies used for those at high risk of developing severe COVID-19. Of the treatments tested, only bebtelovimab was found to “strongly” neutralize BA.2.75.2.
“We now know that this is just one of the emerging variants with similar mutations that will become dominant in the near future,” Murrell said. “We should expect infections to increase this winter.”
However, it remains unclear whether this expected increase in infections will affect the number of hospitalizations. It is also unknown whether COVID vaccines modified to protect against early Omicron variants will protect against BA.2.75.2 and other emerging variants.
“We expect them to be useful, but we don’t know yet how [useful] they will be,” Murrell says.
The study was published in the journal The Lancet Infectious Diseases.
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