Developed variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have become a growing concern worldwide due to their rapid transmission and ability to cause severe infection. A new study led by Ronit Rosenfeld of the Israeli Institute for Biological Research confirms evidence that specific monoclonal antibodies can bind to the receptor-binding domain in variants B.1.1.7 and B.1.351 and effectively neutralize them.
The study “The neutralizing power of therapeutic human monoclonal antibodies against SARS-CoV-2 is retained against new viral variants” is available as a bioRxiv* server, while the article is being reviewed.
The research team previously reported that certain receptor-binding monoclonal antibodies and an N-terminal domain, such as MD65, successfully neutralized SARS-CoV-2. in vitro i in vivo studies.
The current study is based on these findings by measuring the binding ability of four monoclonal antibodies that neutralize SARS-CoV-2 – MD65, MD62, MD29 and BL6 – to four different epitopes of spike receptor-binding domains. Receptor-binding domains contained six mutations commonly associated with the worrying variants, including N501Y, S477N, P.1, and E484K.
They also evaluated the neutralizing power of two monoclonal antibodies specific for the N-terminal domain of B.1.1.7 and B.1351 variant. Biolayer interferometry analysis was used to assess binding capacity.
Binding profile among monoclonal antibodies
The researchers found about 5-22% of the binding lost due to five or six substitutions in the SARS-CoV-2 receptor binding domain.
A significant decrease in binding by 74% was observed in the K417N mutation with the MD62 monoclonal antibody. A 17% reduction in binding to MD65 antibody was also observed.
Of the 4 monoclonal antibodies specific for the receptor-binding domain, MD65 was most effective in neutralizing and providing long-lasting immunity in small doses.
Comparison of epitope recognition with competitor MD65
The LY-CoV555 monoclonal antibody potentially competes with the MD65 monoclonal antibody by binding to hACE2. Although researchers note that the two monoclonal antibodies do not have similar sequences and their recognition patterns may differ despite targeting close epitopes.
To test this theory, the researchers evaluated the binding of LY-CoV555 against the helical protein SARS-CoV-2 and how it was compared to the binding profile of MD65.
In the presence of the MD65 monoclonal antibody, the LY-CoV555 antibody could not bind to the rRBD protein, indicating that both antibodies have epitope targets.
Against SARS-CoV-2 mutations, LY-CoV555 was successfully recognized and bound to N439K, Y453Y, S477N, and N501Y.
However, the presence of E484K substitution blocked the binding of LY-CoV555 to epitopes. “This observation is consistent with recently reported studies, which suggest that E484K substitution is responsible for reversing the neutralization of natural variants of SARS-CoV-2, which carry this mutation, by LY-CoV555 mAb”, the researchers wrote.
Binding ability against multiple SARS-CoV-2 mutations
The researchers used recombinant mutated subgroup S1 subunit proteins that are a combination of mutations found in variants B.1.1.7 and B.1.351. It contains mutations N501Y, K417N and E484K.
Monoclonal antibodies MD65, MD29, BL6 and LY-CoV555 successfully bound to B.1.1.7 recombinant protein classes. However, the binding capacity of MD62 decreased by about 45%. This suggests that structural changes in the spike protein B.1.1.7 may have affected MD62 binding.
The decrease in LY-CoV555 binding and the decrease in BL6 binding by 18% in the B.1.351 recombinant spike protein are probably due to E484K substitution. Monoclonal antibody MD62 could not recognize and bind to the epitope, and binding to MD65 was reduced by 65%. The researchers suggest that the decrease in binding ability is likely due to the presence of K417N substitution.
The potential for immune escape from worrying variants
The researchers evaluated the ability of six monoclonal antibodies and LY-CoV555 to neutralize the worrying variants associated with escape from the immune system. In particular, they evaluated their according to the N-terminal domain for B.1.1.7 and B.1.351 live variants.
MD65, MD62, MD29, BL6 and LY-CoV555 were the most successful in neutralizing variant B.1.1.7. The researchers noted that MD65, MD29, and BL6 showed superior neutralization.
Variant B.1.351 showed a stronger immune escape potential than variant B.1.1.7. Similar to that observed with B.1.351 of the recombinant spike protein, MD62 and LY-CoV555 showed complete loss of binding.
Fortunately, MD65, MD29, and BL6 effectively neutralized variant B.1.351.
* bioRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be considered definitive, guide clinical practice / health-related behavior, or treat it as established information.