Antibodies from former COVID patients neutralise Delta, Omicron

An international research team, led by Tel Aviv University, has demonstrated that antibodies isolated from the immune system of recovered COVID-19 patients are effective in neutralising all known strains of the virus, including the Delta and Omicron variants. Published in the journal Communications Biology, the discovery may eliminate the need for repeated booster vaccinations and strengthen the immune system of populations at risk.

The work is a continuation of a preliminary study conducted in October 2020, at the height of the COVID-19 crisis. At that time, Tel Aviv’s Dr Natalia Freund and colleagues sequenced all the B immune system cells from the blood of people who had recovered from the original COVID strain in Israel and isolated nine antibodies that the patients produced. The researchers have now found that some of these antibodies are very effective in neutralising the Delta and Omicron variants.

“In the previous study, we showed that the various antibodies that are formed in response to infection with the original virus are directed against different sites of the virus,” Freund said. “The most effective antibodies were those that bound to the virus’s ‘spike’ protein, in the same place where the spike binds the cellular receptor ACE2. Of course, we were not the only ones to isolate these antibodies, and the global health system made extensive use of them until the arrival of the different variants of the coronavirus, which in fact rendered most of those antibodies useless.

“In the current study, we proved that two other antibodies, TAU-1109 and TAU-2310, which bind the viral spike protein in a different area from the region where most of the antibodies were concentrated until now (and were therefore less effective in neutralising the original strain), are actually very effective in neutralising the Delta and Omicron variants. According to our findings, the effectiveness of the first antibody, TAU-1109, in neutralising the Omicron strain is 92%, and in neutralising the Delta strain, 90%. The second antibody, TAU-2310, neutralises the Omicron variant with an efficacy of 84%, and the Delta variant with an efficacy of 97%.”

According to Freund, the effectiveness of these antibodies might be related to the evolution of the virus. She explained, “The infectivity of the virus increased with each variant because each time, it changed the amino acid sequence of the part of the spike protein that binds to the ACE2 receptor, thereby increasing its infectivity and at the same time evading the natural antibodies that were created following vaccinations. In contrast, the antibodies TAU-1109 and TAU-2310 don’t bind to the ACE2 receptor binding site, but to another region of the spike protein — an area of the viral spike that for some reason does not undergo many mutations — and they are therefore effective in neutralising more viral variants.”

The two antibodies, cloned in Freund’s laboratory at Tel Aviv University, were sent for tests to check their effectiveness against live viruses in laboratory cultures at the University of California San Diego and against pseudoviruses in the laboratories of Bar-Ilan University in the Galilee. The results were identical and equally encouraging in both tests, leading Freund to believe that the antibodies could bring about a real revolution in the fight against COVID-19.

“For reasons we still don’t yet fully understand, the level of antibodies against COVID-19 declines significantly after three months, which is why we see people getting infected again and again, even after being vaccinated three times,” she said. “In our view, targeted treatment with antibodies and their delivery to the body in high concentrations can serve as an effective substitute for repeated boosters, especially for at-risk populations and those with weakened immune systems.

“COVID-19 infection can cause serious illness, and we know that providing antibodies in the first days following infection can stop the spread of the virus. It is therefore possible that by using effective antibody treatment, we will not have to provide booster doses to the entire population every time there is a new variant.”

Image credit: iStock.com/Dr_Microbe

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