国际英语新闻:New evidence shows COVID-19 antibodies, vaccines less effective against variants

CHICAGO, March 4 (Xinhua) -- A research at Washington University School of Medicine in St. Louis indicates that three new, fast-spreading variants of the virus that cause COVID-19 can evade antibodies that work against the original form of the virus that sparked the pandemic.

To assess whether the new variants could evade antibodies made for the original form of the virus, the researchers tested the ability of antibodies to neutralize three virus variants in the laboratory.

The researchers tested the variants against antibodies in the blood of people who had recovered from SARS-CoV-2 infection or were vaccinated with the Pfizer vaccine. They also tested antibodies in the blood of mice, hamsters and monkeys that had been vaccinated with an experimental COVID-19 vaccine, developed at Washington University School of Medicine, that can be given through the nose.

The B.1.1.7 (found in Britain) variant could be neutralized with similar levels of antibodies as were needed to neutralize the original virus. But the other two variants required from 3.5 to 10 times as much antibody for neutralization.

The researchers then tested monoclonal antibodies: mass-produced replicas of individual antibodies that are exceptionally good at neutralizing the original virus. When the researchers tested the new viral variants against a panel of monoclonal antibodies, the results ranged from broadly effective to completely ineffective.

Since each virus variant carried multiple mutations in the spike gene, the researchers created a panel of viruses with single mutations so they could parse out the effect of each mutation. Most of the variation in antibody effectiveness could be attributed to a single amino acid change in the spike protein. This change, called E484K, was found in the B.1.135 from South Africa and B.1.1.248 from Brazil variants, but not B.1.1.7 from Britain.

The B.1.135 variant is widespread in South Africa, which may explain why one of the vaccines tested in people was less effective in South Africa than in the United States, where the variant is still rare, said senior author Michael S. Diamond.

"We don't exactly know what the consequences of these new variants are going to be yet," said Diamond, also a professor of molecular microbiology and of pathology & immunology. "It is clear that we will need to continually screen antibodies to make sure they're still working as new variants arise and spread and potentially adjust our vaccine and antibody-treatment strategies."

The findings are published Thursday in Nature Medicine.