Scientists gauge an antibody’s usefulness by its ability to block virus from infecting and killing cells in a dish. So-called neutralizing antibodies that prevent infection are thought to be more powerful than antibodies that recognize the virus but can’t block infection, although both neutralizing and non-neutralizing antibodies contribute to defending the body.
The researchers found that five of the 13 antibodies neutralized the original strain. When they tested the neutralizing antibodies against the new variants, all five antibodies neutralized delta, three neutralized alpha and delta, and only one neutralized all four variants.
“In face of vaccination, delta is relatively a wimpy virus,” Ellebedy said. “If we had a variant that was more resistant like beta but spread as easily as delta, we’d be in more trouble.”
The antibody that neutralized all four variants of concern — as well as three additional variants tested separately — was called 2C08. In animal experiments, 2C08 also protected hamsters from disease caused by every variant tested: the original variant, delta and a mimic of beta.
Some people may have antibodies just as powerful as 2C08 protecting them against SARS-CoV-2 and its many variants, Ellebedy said.
Using publicly available databases, the researchers discovered that about 20% of people infected or vaccinated against SARS-CoV-2 create antibodies that recognize the same spot on the virus that is targeted by 2C08. Moreover, very few virus variants (.008%) carry mutations that allow them to escape antibodies targeting that spot.
“This antibody is not unique to the person we got it from,” Ellebedy said. “Multiple antibodies targeting this area have been described in the literature; at least one is under development as a COVID-19 therapy. Similar antibodies have been generated by people infected in Italy and people infected in China and people vaccinated in New York. So it’s not limited to people of certain backgrounds or ethnicities; it’s not generated only by vaccination or by infection. A lot of people make this antibody, which is great because it is very potent and neutralizes every variant we tested.”