Omicron's latest subvariants have mutant combinations, making them more immune than ever before.
Nearly 3 years after the pandemic, the virus faces a daunting "challenge": constantly mutating new ones to break through the immunity built up by humans through vaccines and countless infections. A worrying new statistic suggests that several newly discovered strains of the virus with some immune evasion have caught scientists' attention. One or more of these variants are likely to trigger a new wave of epidemics this fall and winter.
"We can say with certainty that something is about to happen, and there is a lot of uncertainty in it." Cornelius Roemer, who studies viral evolution at the University of Basel, said. Whether they lead to more hospitalizations and deaths is a big question.
Emma Hodcroft, a molecular epidemiologist at the University of Bern, said: "It is not surprising that the virus has these changes in immune evasion. "Gradually, the coronavirus may last as long as the common cold or flu, and will come back every year." ”
It now appears that the strains driving the latest wave of the pandemic are all subvariants of Omicron, which have swept the world over the past year. These include the most famous variant, BA.2, which surpasses the original BA.1 in an all-out rate; the more contagious variant BA.5 has been found in many parts of the world; in addition to the outbreak of the BA.2.75.2 variant in India, Singapore and parts of Europe. BQ.1.1, a variant from BA.5, has also been found in several countries.
Despite their different origins, some new strains have been found to have similar combinations of mutations to evade the immune system's defenses, a notable example of convergent evolution. Jesse Bloom, an evolutionary biologist at Fred Hutchinson Cancer Center, said they all change at six key points in the viral genome that affect how well neutralizing antibodies from vaccination or previous infections bind to the virus.
To quickly assess the new subvariant's ability to evade immunity, the researchers replicated the virus's spike protein and exposed them to monoclonal antibodies or human serum to measure the antibody's ability to stop the variant from infecting cells. Through such tests, researchers in China and Sweden found that the spike protein from BA.2.75.2 can effectively evade almost all monoclonal antibodies used to treat the new coronavirus, suggesting that existing treatments may become ineffective. The team also found that BA.2.75.2 appears to be very good at evading immunity in humans.
In a preprint released Sept. 19, Ben Murrell, an immunologist at the Karolinska Institutet, and his colleagues report. BA.2.75.2 is less than one-sixth of the neutralization effect compared to BA.5. "This is the most resistant variant we've ever evaluated," says Karolinska virologist Daniel Sheward.
Dr. Cao Yunlong, an immunologist at Peking University, and his colleagues found a breakthrough infection of BA.2.75.2 on BA.1, BA.2 or BA.5 immune samples after testing blood samples from 40 people who had received three doses of CoronaVac (Sinovac vaccine) and another 100 who had been vaccinated. The team also found that BQ.1.1 has an equally astonishing ability to evade antibodies.
Dr. Cao and his colleagues report that the new variant has not lost any ability to infect human cell receptors, meaning that the variant is not less contagious. Some of the evidence they released suggests that the infected variant proproportionally triggers more faulty antibodies — those that bind tightly to the virus but don't impair its ability to infect cells. Dr. Cao Yunlong said that all these findings may indicate a huge epidemic signal. "Immune escape mutation has never been seen before, but the virus is still evolving rapidly," he said. "It's bad."
Sheward and Murrell agree that we expect a large number of coronavirus infections around the world in the coming months, as happened during the Omicron outbreak last winter. But they were less pessimistic than Dr. Cao, noting that more people are now recovering from infections or receiving additional vaccine doses, including the Omicron-specific booster, which began rolling out this month. These will boost overall antibody levels and potentially expand the antibody library, Sheward said: "I don't think we're quite back to square one yet." ”
"The option of adding BA.5 to vaccine boosters still looks like a good option," Bloom added. "Booster vaccines will always be one step behind, but the good news is that BA.5 booster vaccines will be one to two steps behind virus evolution, not five steps behind."
Once more people are infected with the new strain, how brutal the process of coronavirus resurgence will become. The next wave of the pandemic could also provide clues about better containment, Murrell said: "I think we're going to learn a lot this winter." ”
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