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U.S. researchers have discovered an antibody that can neutralize all known viral variants. A universal vaccine seems within reach.
Since its first appearance just over two and a half years ago in Wuhan, China, Sars-CoV-2 coronavirus has evolved dramatically. Continuous mutations have led to new variants becoming increasingly adept at evading our immune defenses. Most notably, the circulating omicron subvariant BA.5 has modified its receptor-binding site so that antibodies produced by previous infections or vaccination can no longer dock to its spike protein. Therefore, those who have been vaccinated and those who have recovered are protected mainly from severe courses of covid-19 but not from reinfection.
Scientists are always looking for new, more broadly effective antibodies against Sars-CoV-2. They hope to find a vaccine that works not only against all previous variants of the coronavirus but also future ones. A team led by Sai Luo at Harvard Medical School in Boston has found what they are looking for and maybe one step closer to a universal vaccine.
They have identified an antibody that can neutralize all known variants of SARS-CoV-2. The antibody was developed using mice genetically engineered to produce human immune cells. The team modified the mouse genome so that the animals had a vast number of different human B cells – the cells that produce the antibodies.
The rodents were injected twice at four-week intervals with the spike protein of the Wuhan strain of Sars-CoV-2 or nanoparticles with only its binding site. This caused the mice’s humanized immune system to produce nine different strains of antibodies against the coronavirus.
To determine how well these defense proteins worked against the different viral variants, the researchers performed neutralization tests with one monoclonal antibody from each line. The SP1-77 antibody proved to be particularly effective.
“SP1-77 very potently neutralized all previously known Sars-CoV-2 variants, including the recently emerged omicron subvariants BA.1, BA.2, BA.3, BA.4/5, and BA.2.12.1,” Luo and his colleague’s report. SP1-77 does not dock at the coronavirus receptor-binding site as most other antibodies do. “Structural analyses confirmed that the antibody binds on the opposite side from the ACE2-binding site,” the team writes—a site on the spike protein rarely affected by coronavirus mutations.
In addition, although SP1-77 allows the virus to dock with the ACE2 receptor on the cell surface, it blocks the fusion of the outer viral membrane with the cell’s membrane – a step essential for the virus to enter the cell the scientists describe. As a result, the coronavirus can bind to human cells but cannot join them and thus cannot infect them.
- source: heute.at/picture: pixabay.com
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