Scientists identify antibodies that can neutralize Omicron variant
By Hannah Jackson, CTVNews.ca writer
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Barrie, Ont., Canada (CTV Network) — A team of scientists have identified antibodies they say can neutralize Omicron and other COVID-19 variants.
According to a new study, a group of international researchers have found certain antibodies can target areas of the virus spike protein that don’t undergo significant changes as the virus mutates.
The findings were published Dec. 23 in the scientific journal Nature.
The research project was led by David Veelser, an investigator with the Howard Hughes Medical Institute, and Davide Corti of Humabs Biomed, a subsidiary of Vir Biotechnology in Switzerland.
Veesler, who is also an associate professor of Biochemistry at the University of Washington School of Medicine in Seattle, said by identifying the targets of the “broadly neutralizing” antibodies on the spike protein, it could be possible to design vaccines and antibody treatments that will be effective against Omicron, or other variants that may emerge.
“This finding tells us that by focusing on antibodies that target these highly conserved sites on the spike protein, there is a way to overcome the virus’ continual evolution,” Veesler said in a press release. AN UNUSUAL VARIANT
The Omicron variant is considered to be “unusual” because of a large number of mutations to two key areas of the virus’ spike protein.
Speaking at a press conference last month, Canada’s Chief Public Health Officer, Dr. Theresa Tam, said one area of mutations is in the virus’ spike receptor binding domain.
“Where the virus attaches itself and invades our cells,” she explained.
The other area of mutation is in the antigenic supersite, Tam said, “because it is a target for our body’s defensive or neutralizing antibodies.”
Thirty-seven mutations have been detected in the spike protein in the Omicron variant.
Researchers believe this is part of the reason the variant has been able to spread so quickly, and can infect people who are fully vaccinated, as well as those who have previously had COVID-19 infection.
According to Veesler, the main question he and his colleagues were seeking to answer, was how the “constellation of mutations in the spike protein of the Omicron variant affected its ability to bind to cells and to evade the immune system’s antibody responses.” CREATING A PSEUDOVIRUS
In order to conduct the study, the researchers created a pseudovirus — a disabled, non-replicating virus — that produces spike proteins like a coronavirus.
Next, they created pseudoviruses that had spike proteins similar to that of the Omicron variant, and other, earlier strains of SARS-CoV-2, the virus that causes COVID-19.
The researchers did this in order to see how well the different versions of the spike protein were able to bind to the protein on the surface of cells, which is how the virus latches onto and enters the cell.
“The protein is known as the angiotensin converting enzyme-2 (ACE2) receptor,” according to the study.
The researchers found that the Omicron variant could bind 2.4 times better than the spike protein from the virus strain detected at the beginning of the pandemic.
The scientists also found that the Omicron variant could bind to mouse ACE2 receptors quickly.
The researchers said this suggests Omicron “might be able to ‘ping-pong’ between humans and other mammals.”
The scientists also used antibodies from patients who had previously been infected with earlier versions of the COVID-19 virus, those who had been vaccinated against the earlier strains, and those who both were previously infected and vaccinated.
They looked at how well the antibodies from vaccines and previous infections protected against the Omicron variant.
The researchers found that people who had been infected with earlier strains and those who had received one of the “six most-used vaccines” all had reduced ability to block an Omicron infection.
Those who had previously been infected and those who received the Johnson & Johnson, Sputnik V or Sinopharm vaccines had little or no ability to block the Omicron variant from invading their cells.
However, those who had received two doses of an mRNA vaccine series from Moderna or Pfizer-BioNTech, or the AstraZeneca vaccine, did have some neutralizing activity.
Despite this, the press release notes that the ability to neutralize the variant was reduced between 20 and 40 fold.
The study found that antibodies from people who had previously been infected, recovered, and then had two vaccine doses also proved to have some neutralizing ability.
The researchers tested a large panel of antibodies generated against earlier versions of the virus, and identified four classes of antibodies that retained their ability to neutralize the Omicron variant.
“Members of each of these classes target one of four specific areas of the spike protein present in not only SARS-CoV-2 variants, but also a group of related coronaviruses, called sarbecoviruses,” the press release reads. “These sites on the protein may persist because they play an essential function that the protein would lose if they mutated. Such areas are called ‘conserved.’”
Veesler said that finding that antibodies are able to neutralize the virus by recognizing the conserved areas in various variants suggests that vaccines and antibody treatments that target those areas could be effective against a number of strains that could arise due to mutation.
Each of the largest vaccine manufacturers have said they are looking into making a Omicron-specific vaccine amid the most recent surge in COVID-19 cases.
In Canada, officials are urging members of the public to get a third dose of a COVID-19 vaccine as soon as they are available, and provinces and territories have opened up booster eligibility to larger swaths of the population in a bid to increase protection and stem the spread of the virus.
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