A team of US researchers has identified and tested an antibody that limits the severity of infections from a variety of coronaviruses, including those that cause COVID-19 as well as the original SARS illness.

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Researchers at Duke University and the University of North Carolina (UNC) at Chapel tested the antibody in experimental models. When given after infections, the antibody reduced severe lung symptoms. "This antibody has the potential to be therapeutic for the current epidemic. It could also be available for future outbreaks, if or when other coronaviruses jump from their natural hosts to humans," said Barton Haynes, director of Duke Human Vaccine Institute.

In the study, published in the journal Science Translational Medicine, the team isolated the antibody by analysing the blood from a patient who had been infected with the original SARS-CoV-1 virus, which caused the SARS outbreak in the early 2000s, and from a current COVID-19 patient.

They identified more than 1,700 antibodies, which the immune system produces to bind at specific sites on specific viruses to block the pathogen from infecting cells. When viruses mutate, many binding sites are altered or eliminated, leaving antibodies ineffectual. But there are often sites on the virus that remain unchanged despite mutations.

The researchers focused on antibodies that target these sites because of their potential to be highly effective across different lineages of a virus. Of the 1,700 antibodies from the two individuals, the Duke researchers found 50 antibodies that had the ability to bind to both the SARS-CoV-1 virus as well as SARS-CoV-2, which causes COVID-19.

Further analysis found that one of those cross-binding antibodies was especially potent-able to bind to a multitude of coronaviruses in addition to the two human-infecting pathogens. "This antibody binds to the coronavirus at a location that is conserved across numerous mutations and variations. As a result, it can neutralise a wide range of coronaviruses," Haynes said.