Parnad Basu, Amity University Kolkata
While the whole world is fighting with SARS-CoV-2, scientists are continuously searching for ways to beat the virus. Doing so, they have found out an antibody, CR3022. This CR3022 was able to neutralize the SARS-CoV, which caused an epidemic in 2003. CR3022 had been collected from a patient 14 years ago. In a recent study, scientists found that the binding affinity and neutralization of CR3022 is related to one (P384A) of the four mutational differences in the antibody’s epitope. The spike glycoproteins of SARS-CoV and SARS-CoV-2 have 77% amino acid sequence identity. And the CR3022 targets only the receptor-binding domain (RBD) of the spike glycoprotein, that too when the RBD is the ‘up’ conformation on the spike glycoprotein. This helps the CR3022 to show higher affinity in SARS-CoV than SARS-CoV-2.
In the study, scientists saw that out of four SARS-CoV-2 RBD mutants, CR3022 can only neutralize the P384A but not A372T, T430M, and H519N. P384A also increases the binding affinity of SARS-CoV-2 RBD to CR3022. In addition to that, it was also observed that while binding with SARS-CoV RBD and SARS-CoV-2 RBD, CR3022 forms three H-bonds and only one H-bond respectively. Thus, making the CR3022 and SARS-CoV RBD bond energetically preferable. CR3022 antibody can also form a stable complex with SARS-CoV spike glycoprotein in a prefusion conformation but falls apart in the case of SARS-CoV-2 spike glycoprotein. Although CR3022-bound RBD is flexible, the bivalent binding of CR3022 to spike glycoprotein does not occur as there was no IgG avidity effect observed.
Looking at the current pandemic, it is obvious that SARS-CoV-2 is going to circulate in humans for a very long period. There are already some vaccines that scientists hope will work well against SARS-CoV-2. However, if SARS-CoV-2 can show antigenic drift to escape vaccine-induced immunity is still not known.
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Reference: https://doi.org/10.1371/journal.ppat.1009089
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