However, these antibodies generally have few mutations, and this can lead to reversals: these antibodies can also attack the healthy body. Indeed, it is these mutations (or genetic recombinations) that are at the origin of those changes to the antibody-binding sites which give them their specificity. Without this, the antibodies are not precise enough and risk attacking too many false targets.
Study of these anti-RBD antibodies could potentially be a huge help in the fight against the pandemic. In order to select the best candidates, researchers sequenced 598 anti-bodies from 10 infected patients and then fine-tuned the results on the basis of several criteria:
- the reactivity of SARS-CoV-2 to the S1 protein
- the neutralising activity of the antibodies
- the minimum required concentration to neutralise 50% of the SARS-CoV-2
Taking these criteria into account, the 18 antibodies having the greatest success in recognising the virus envelope were examined. However, 4 of these antibodies also attack healthy human tissue in the brain, the smooth muscles of the lungs, the heart, the kidneys and the colon, making them poor allies in the fight against SARS-CoV-2.
In the list of the 14 remaining antibodies, CV07-209 was chosen as it had the strongest neutralising effect in vitro along with the weakest concentration. In order to test its prophylactic and therapeutic effects in vivo, an infection model was set up using SARS-CoV-2 on hamsters. In the “prophylactic” group, CV07-209 was administered with a concentration of 18 mg/kg 24 hours before infection, while in the “therapeutic” group, it was administered in the same dosage 2 hours before infection. There was also a control group injected with an antibody not specifically envisaged for use against SARS-CoV-2. The evolution of the infection was gauged by the hamsters’ weight loss as well as by measuring viral particles after sacrifice.