Validation of SARS-CoV-2 neutralizing antibodies by ELISA

Abstract

SARS-CoV-2 is a virus that mainly attacks the respiratory system causing mild to fatal symptoms. SARS-COV-2 has spread rapidly causing a global pandemic. Vaccines have been developed to lower the risk of developing a severe infection and to lower the spread of the virus. Nevertheless, immunosuppressed patients might not develop the necessary immune protection despite receiving all vaccine boosters. This study aims at validating neutralizing antibodies against SARS-CoV-2, which can block the entrance of the virus to the host cell by blocking its spike protein (S). The ability of these antibodies can be used as treatment for SARS-CoV-2 infections. Nonetheless, the neutralizing antibodies must be validated to assess their affinity, specificity, and reproducibility before progressing to clinical trials, which is the aim of this study. In this study 3 types of single chain antibodies (scFv) generated from 4 rounds of phage display biopanning were validated by assessing them via ELISA. Anti-Trimer, anti-S1, and ant-Receptor Binding Domain (RBD) showed specific high binding to their respective target. On the neutralizing ELISA, the commercially available neutralizing antibody showed low, medium, and high neutralization against RBD BA.5, BA.1.1 and delta respectively. The quantity of binding of the scFv depends on the surface area of the different targets. The difference in neutralization activity is due to mutations in each RBD variant which gives the property of resistance against neutralizing antibodies. In conclusion, the 3 populations of neutralizing antibodies were validated to bind to their specific target, but these should be further confirmed by a neutralizing ELISA.