CHARACTERIZATION OF MONOCLONAL ANTIBODIES AGAINST STAPHYLOCOCCAL ENTEROTOXIN D SUPERANTIGEN

Abstract

Bacterial superantigens (SAgs) are a group of toxins produced by Staphylococcus aureus and group A streptococci that cause detrimental systemic effects by activating T cells in a T cell receptor (TCR) Vꞵ—specific manner. SAgs circumvent normal antigen processing and presentation by directly ligating major histocompatibility complex (MHC) class II molecules and TCRs. Although several modes of SAg binding have evolved, staphylococcal enterotoxin D (SED) is unique because it couples the properties of Zn2+-dependent MHC class II-binding with homodimer formation. To better address the interactions of SED with MHC class II and TCR, this study focuses on the production and characterization of monoclonal antibodies against this SAg. Enzyme-linked immunosorbent assays (ELISAs) show these antibodies to be highly specific for SED, but not other SEs, and that the antibodies are efficient in capturing SED. Specific binding of the antibodies was determined by surface plasmon resonance and flow cytometry. Based on these data, two subsets of antibodies were identified. One set of antibodies appears to bind an MHC class II binding interface of SED and the second set detected both bound and unbound toxin. Although, these antibodies were shown to be ineffective in inhibiting T cell proliferation in response to SED, the affinity and specificity of these antibodies indicates they can be used for identification and purification of SED.