February 7-14 2021
A promising modified antibody
2 vaccines and 2 treatments based on antibodies have been authorised in the United States against COVID-19. However, the question remains as to whether they will be effective against new variants of the virus. In addition, epidemics are recurrent, and there are numerous coronaviruses active in the animal reservoir which may, like SARS-CoV-2, cross the species barrier and infect humans.
How should the vaccines function is order to be effective? As with other coronaviruses, the SARS-CoV-2 spike (S) surface protein enables the virus to enter cells and constitutes the principal target of neutralizing antibodies. SARS-CoV-1 and SARS-CoV-2 share 76% of the protein sequence of S, but very few cross-neutralizing antibodies, that is, those effective against different coronaviruses, are known. These antibodies could, however, prove to be an interesting alternative to combat future epidemics. Cross-neutralizing antibodies are in general less effective, but American researchers have recently discovered a more powerful version.
The antibody in question was isolated in a patient who had recovered from illness in the SARS epidemic of 2003. This antibody has a relatively modest neutralizing activity against different coronaviruses. It was modified in vitro so as to maximise its affinity and its neutralization potential. It possesses a highly conserved epitope across different coronaviruses, covering the cell receptor binding site (RBD site) for viral particle entry. It thereby is able to neutralize clade 1 sarbecovirus, part of the coronavirus. The modified antibody was tested on mice in vivo, providing effective protection against SARS and COVID-19, as prophylaxis or therapeutic agent.
This antibody, as developed during this study, has potential as a treatment not only against COVID-19, but also against other respiratory illnesses caused by coronaviruses.