CHICAGO, June 22 (Xinhua) -- A research at Washington University School of Medicine in St. Louis suggests that many, but not all, therapies made from combinations of two antibodies are effective against a wide range of COVID-19 variants.
The panel included mutations found in three of the four variants that have been designated "variants of concern" by the World Health Organization: Alpha first identified in the United Kingdom, Beta identified in South Africa and Gamma identified in Brazil, as well as an emerging variant from India similar to the Delta variant of concern. Researchers also tested variants from New York and California. They used a mix of virus samples originally obtained from people with COVID-19 and laboratory strains genetically engineered to contain key mutations.
The researchers evaluated the antibodies in hamsters and two strains of mice. They first gave the animals antibodies, singly or in the same combinations in which they are given to treat patients, a day before infecting them with one of the virus variants, monitored the animals' weight for six days and then measured the amount of virus in their noses, lungs and other parts of the body.
Although some single antibodies showed reduced or no ability to neutralize virus variants in a dish, low doses of most of the antibody combinations protected against disease caused by many of the variants. The researchers sequenced viral samples from the animals and found no evidence of drug resistance in viruses from any of the animals that had been treated with combination therapies.
"Dual therapy seemed to prevent the emergence of resistant viruses," said co-author Jacco Boon, an associate professor of medicine, of molecular microbiology and of pathology and immunology. "Resistance arose with some of the monotherapies, but never with combination therapy."
Since antibody-based COVID-19 therapies primarily are used to treat people who already are infected, the researchers also evaluated how well the antibody combinations performed when given after infection with the Beta variant. The antibody cocktails corresponding to those from AstraZeneca, Regeneron and Vir were all effective at reducing disease caused by the Gamma variant; the one from AbbVie only was partially protective, and the one from Lilly showed no efficacy at all.
"It's going to be useful going forward to understand how these monoclonal antibodies are going to behave as variants continue to emerge," said senior author Michael Diamond, a professor of medicine. "We need to think about and generate combinations of antibodies to preserve our ability to treat this disease. And we'll need to monitor for resistance - although, in my opinion, the use of specific combinations will make this less of an issue."
The findings were published Monday in the journal Nature.