Screening and identification of broadly neutralizing antibodies against different mutant strains of SARS-CoV2

Objective To screen high-affinity neutralizing antibodies with broad spectrum specificity against different SARS-CoV2 mutants and verify their functions. Methods Balb/c mice were immunized twice with SARS-CoV2 S protein mRNA vaccine coated with liposome, and the specific antibody content in serum was determined. The mice with higher antibody titer were selected for shock immunization. The spleen cells of mice after shock immunization were fused with myeloma cells to prepare fusion cells, and the clones that produces monoclonal antibodies against different parts of S protein were screened by limited dilution and ELISA. Monoclonal antibody was purified and neutral-ization experiments were performed to verify the neutralization activity of the antibody. Monoclonal antibodies with broad spectrum binding properties against recombinant receptor binding domain(RBD) proteins of four SARS-CoV2 mutants were screened by ELISA. Results After twice immunizations, the serum antibody titer against S protein in high dose group 4 was the highest. After shock immunity and cell fusion, 12 hybridoma cell clones with binding activity to S protein were screened, among which 9 strains specifically bound to RBD protein. The neutralization test results showed that the antibodies 41, 46 and 47 had significant neutralization activity in vitro. Compared with the other two antibodies, antibody 46 showed broad-spectrum binding activity to the RBD proteins of four SARS-CoV2 mutants including Omicron. Conclusions Antibody 46 is a broad-spectrum specific neutralizing antibody against four different SARS-CoV2 mutants, which can be further humanized and potentially used for the treatment of COVID-19.