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A preprint of a study conducted by researchers from Utrecht University, in collaboration with Erasmus MC and Harbor BioMed, outlines the first report of a human monoclonal antibody that can block SARS-CoV-2.



Understanding antibodies: Terms and definitions



Monoclonal antibody potently inhibits SARS-CoV-2







The spike proteins of SARS-CoV-2 and SARS-CoV are very similar on a structural level, sharing 77.5% of their amino acid sequence. Blocking the initial binding of the virus to the ACE2 receptor via the spike protein is one potential treatment avenue. Here's where monoclonal antibodies could help.



Monoclonal antibodies that target vulnerable sites on viral surface proteins are an emerging approach for treating infectious diseases. In this study by Wang et al., a human antibody known as 47D11 was found to bind to SARS-CoV-2 and SARS-CoV, and to potently inhibit the virus' infection of Vero cells, a type of cell line.





An unexpected mechanism of action

How exactly does 47D11 neutralize coronavirus? The scientists aren't too sure yet. However, it appears that it's not by preventing the S protein from binding to ACE2, interestingly.



The authors say in the preprint: "Our data show that 47D11 neutralizes SARS-CoV and SARS-CoV-2 through a yet unknown mechanism that is different from 86 receptor binding interference. Alternative mechanisms of coronavirus neutralization by receptor binding domain-targeting antibodies have been reported including spike inactivation through antibody-induced destabilization of its prefusion structure, which may also apply for 47D11."







They continue: "47D11 binds a conserved epitope on the spike receptor binding domain explaining its ability to cross-neutralize SARS-CoV and SARS-CoV-2, using a mechanism that is independent of receptor binding inhibition."





"Far too early to speculate"

Research leader and last author Berend-Jan Bosch (Utrecht University) does not want to raise false expectations. It is a promising first step, but it is far too early to speculate about the potential efficacy in humans. The research is being reviewed by a leading scientific journal. Further comments can be provided once the item has been accepted.