A Novel Fully Human Recombinant Antibody Neutralizing the α-hemolysin of Staphylococcus Aureus

Abstract BackgroundMethicillin-resistant Staphylococcus aureus (MRSA) is resistant to almost all β-lactam antibiotics. Hence, new ways to control MRSA infection, such as antibacterial antibodies, need to be explored. α-Hemolysin is the most important virulence factor widely expressed in S. aureus. This study aimed to develop a new fully human antibody against α-hemolysin of S. aureus and explore its neutralizing effect. ResultsThe single-chain antibody fragments（scFvs）against S. aureus were screened from a fully human scFv library using phage display technology with purified α-hemolysin protein. The selected scFvs had good binding affinities to α-hemolysin and were highly specific to S. aureus. The IgG-like scFv-Fc inserted into the pcDNA3.1 or pMH3 vector was expressed in HEK293F suspension cells to extend the antibody's in vivo half-life and restore Fc function. The size of purified scFv-Fc was about 55 kDa. The functions of expressed scFv-Fcs against α-hemolysin were validated. The results of A549 cytotoxicity assays showed that scFv10-Fc and scFv555-Fc had better protective effects than other scFv-Fcs on A549 cells. The results of anti-rabbit erythrocyte lysis assay confirmed that scFv555-Fc had a significant neutralizing effect on toxins. The scFv555-Fc was used to construct the docking model of antigen–antibody complexes using Discovery Studio software. It predicted that the key binding sites of α-hemolysin were TYR28, LYS37, PHE39, ARG56, and LYS58, which might be the key toxic sites of α-hemolysin.ConclusionsA novel fully human scFv-Fc antibody neutralizing the α-hemolysin toxin of S. aureus was successfully developed. The findings might provide a new theoretical basis and treatment method for preventing MRSA infection.