Author: Chen Jin
Unit: Beijing Ditan Hospital affiliated to Capital Medical University
Recently, the national protein science center - Beijing (Phoenix Center) Yu Xiaobo researcher team, Capital Medical University affiliated Beijing Ditan Hospital Professor Wang Yajie team, the Chinese Center for Disease Control and Prevention Institute of Infectious Disease Prevention and Control Kan Biao researcher team and Beijing Yiqiao Shenzhou team jointly developed the new crown virus spike protein mutant neutral antibody detection chip project related article "Inhibitor screening using microarray identifies the the High capacity of neutralizing antibodies to Spike variants in SARS-CoV-2 infection and vaccination" was published in the journal Theranostics (IF:11.556) on February 28, 2022.
The global spread of the novel coronavirus (SARS-CoV-2) and the continuous emergence of mutant strains have brought great challenges to the existing vaccine and antibody drug defense system. In different strains of COVID-19, mutations that occur on spike proteins (Spike, S) are very noteworthy and worrying.
The S protein infects cells through its receptor binding domain (RBD) to the host ACE2 receptor and is an important target for therapeutic drug and vaccine development. Mutations in the RBD domain may attenuate the neutralizing effect of neutralizing antibodies, hindering drug development and reducing vaccine efficacy.
Therefore, how to quickly detect and evaluate the level and protection of antibodies that the human body can neutralize after infection with the new coronavirus or after vaccination, as well as observe the impact of mutations on vaccines and antibody drugs, and then develop new vaccines and antibody drugs, is crucial for epidemic prevention and control.
The chip developed by the team covers the neutral antibody detection chip of the new coronavirus spike protein mutant at more than 70 common mutation sites of the new coronavirus protein, which is flexible and fast, and can be updated and upgraded according to new viral mutations; only 20 microliters of serum samples are needed; and can be operated in conventional laboratories, without the need for P2 or P3 laboratories. Using this chip, the neutralizing effect of neutralizing antibody drugs and serum neutralizing antibodies in different populations on mutant strains can be systematically assessed (Figure 1).
Figure 1 Preparation and application of neutralizing antibody detection chip for new coronavirus spike protein mutants
Using the new coronavirus spike protein mutant neutralizing antibody detection chip, the team first evaluated the neutralizing effect of three anti-RBD antibodies on the mutant strain. The results found that the 73# antibody has no inhibitory effect on the S mutant, while the 21# and 53# antibodies can neutralize most S mutants (Figure 2A-C), indicating that not all anti-RBD antibodies are neutrally active.
Further analysis of the tolerance mutations and sensitive mutations of the 21# and 53# antibodies showed that about 50% of the tolerant mutation sites of the 21# and 53# antibodies were located at the binding interface between RBD and ACE2, while most of the sensitive mutations were located outside the binding interface between RBD and ACE2 (Figures 2D and 2E), indicating that antibodies targeting non-RBD epitopes may also have a neutralizing effect, providing an important target for the development of therapeutic antibody drugs for the new crown.
Fig. 2 Neutralizing effects of anti-RBD antibodies on different S mutants
Next, using the chip, they evaluated the neutralizing effect of serum neutralizing antibodies on mutant strains in 30 cases of the vaccine (Figure 3). The results showed that vaccine serum had a neutralizing effect on most S mutants, and clustering vaccinated populations into two groups based on neutralizing antibody titers (Figure 3A) revealed the heterogeneity of the immune response of the COVID-19 vaccine, suggesting that people with low neutralizing antibody titers may need to be vaccinated with boosters. Further compared with wild-type strains, sensitive and tolerated mutations that may affect the serum neutralization antibody activity of vaccines (Figure 3D-G) were identified, providing a theoretical basis for the development of a new COVID-19 vaccine.
What's more, high-titer neutralizing antibodies have fewer escape mutations compared to low-titer neutralizing antibodies (Figures 3B and 3C), indicating that high-titer neutralizing antibodies are more protective of mutant strains.
Fig. 3 Heterogeneity response of vaccine serum to S mutants
They then screened 104 vaccine serum samples using a pre-developed COVID-19 whole proteome polypeptide chip[1], and further analyzed the mechanism of high titer neutralizing antibodies in response to high protective efficacy of mutant strains from the perspective of antibody diversity. The results show that high titer neutralizing antibodies target more diverse epitopes (Figure 4), providing a scientific basis for the evaluation of vaccine effectiveness and the development of therapeutic antibodies and vaccines.
Figure 4 Total number of S protein epitopes recognized by neutralizing antibodies of different titers
Dr. Zhang Xiaomei, Dr. Liang Te and Ph.D. Wang Hongye of the National Protein Science Center, Zheng Mei, Ph.D. student of Beijing Ditan Hospital affiliated to Capital Medical University, and Zhou Haijian, researcher of the Institute of Infectious Disease Prevention and Control of the Chinese Center for Disease Control and Prevention, are the co-first authors of the article. Yu Xiaobo, researcher of the National Protein Science Center, Professor Wang Yajie of Beijing Ditan Hospital affiliated to Capital Medical University, and Kan Biao, researcher of the Institute of Infectious Disease Prevention and Control of the Chinese Center for Disease Control and Prevention, are the co-corresponding authors of the article.