Isolation of Monoclonal Antibodies to Group A Streptococcus Antigens Using Phage Display

High-affinity monoclonal antibodies are valuable tools for studying the humoral immune response to Group A Streptococcus (GAS) antigens. This protocol describes a method for the selection of monoclonal antibody fragments that bind to GAS antigens using either naïve or immune repertoires displayed on the surface of M13 bacteriophage. Clones that specifically bind to GAS antigens are enriched for during the biopanning process, in which antibody-phage clones bind to an immobilized GAS antigen and are then washed, eluted, and amplified for subsequent rounds of selection. After the final round of biopanning, individual clones are screened by phage enzyme-linked immunosorbent assay (ELISA), and unique clones are identified by DNA fingerprinting and sequencing. The isolated monoclonal antibodies can be used to explore antibody-antigen interactions in molecular detail and provide insight into the protective mechanisms from GAS infection.