More COVID-19 studies suggest BA.2.86 may be less immune-evasive than feared

antibodies binding to cell receptors

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Two more lab groups—one from Sweden's Karolinska Institute and the other from Harvard University—have reported results of antibody neutralization lab experiments, which suggest vaccination or previous infection offer some protection against the highly mutated BA.2.86 SARS-CoV-2 variant.

In other developments, countries uploaded more BA.2.86 samples to genetic sequencing databases, and the United Kingdom updated its assessment of the variant.

Encouraging neutralization findings

The first BA.2.86 sequences were reported a few weeks ago, and the variant's high number of mutations signaled the biggest jump since the Omicron variant emerged following Delta variant circulation. Several scientists worried that the large magnitude of the change could allow BA.2.86 to easily evade earlier antibody protection from the vaccine or infection.

Last week, a group from Peking University reported the first lab studies on neutralization, which suggested that BA.2.86 had the capacity to escape antibodies from earlier XBB infection, but appeared to have lower infectivity than XBB.1.5 and EG.5 subvariants.

On September 1, the Karolinska Institute team reported its initial data from tests using the blood of donors from Stockholm, one cohort from before XBB circulated and the other after XBB arrived. On Twitter, Ben Murrell, PhD, with the Karolinska Institute, said the pre-XBB samples were poor at neutralizing BA.2.86 and didn't fare much better against XBB.1.5. "But, somewhat encouragingly, last week's samples were substantially better, with 8 out of 12 neutralizing BA.2.86 at titers over 100."

The team also screened some monoclonal antibodies, finding that BA.2.86 was resistant against all of them, including sotrovimab.

Murrell said the Karolinska lab's findings are consistent with the Peking University group's findings. (Chinese and Swedish researchers have detailed their findings in preprint reports.) "It isn't yet clear whether BA.2.86 (or its offspring) will outcompete the currently-circulating variants, and I don't think there is yet any data about its severity, but our antibodies don't appear to be completely powerless against it."

Our antibodies don't appear to be completely powerless against it.

Yesterday, researchers with the Barouch Lab, based at Harvard, on Twitter reported the first data from their antibody neutralization experiments, which suggest responses to BA.2.86 were lower than to BA.2, but were comparable to or higher than to current circulating variants. Neutralizing antibodies to all variants, including BA.2.86, increased following XBB infection.

Ninaad Lasrado, PhD, one of the researchers at the Barouch Lab, on Twitter said the experiments were done on samples from 66 people, including 44 who had received the bivalent (two-strain) mRNA COVID booster. He added that the findings fuel hopes that the new XBB.1.5 vaccines have the potential to induce cross-reactive neutralizing antibodies against other recombinants and against BA.2.86.

UK: Still no clear signal of BA.2.86 growth

In its updated risk assessment of BA.2.86, the UK Health Security Agency added a few details about the UK's three patients and addressed the unfolding global situation.

It said the first UK patient with BA.2.86 had a mild illness, and another had no respiratory symptoms. Also, a patient from Scotland was symptomatic. The HSA said two of the cases were sequenced through routine hospital surveillance of test-positive cases.

Though more countries have reported cases, there is still no clear signal of growth in any location. The HSA said by examining collection dates and phylogenic mapping, it's not clear if a mass gathering seeded the spread to other countries, if an outbreak involving BA.2.86 is under way in a country without surveillance, or if there is widespread transmission that wasn't detected by surveillance. The agency added, however, that phylogeny doesn't support widespread high-level community transmission.

With all the uncertainties about virus fitness, growth rates, and biological properties owing to the mutations, BA.2.86 doesn't meet the definition of a variant of concern.

Meanwhile, more countries have uploaded BA.2.86 samples to sequencing databases, according to variant trackers, including France and Spain. Also, other nations reported more additional samples, including one from Pennsylvania in the United States.

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