Mutational analysis and molecular modeling of the binding of Staphylococcus aureus enterotoxin C2 to a murine T cell receptor Vβ10 chain

Abstract

We investigated the role of the β chain HV4 region in the binding of a Vβ10 T cell receptor to superantigen S. aureus enterotoxin C2 (SEC2)/MHC class II complexes. Residues 6971 of the Cw3/1.1 TCR Vβ10 chain, derived from an H‐2Kd‐restricted cytotoxic clone, were individually changed to alanine using site‐directed mutagenesis, and mutated TCR β chains were transfected along with the wild‐type TCR α chain into a TCR α–β– T hybridoma. SEC2/MHC recognition was measured by IL‐2 production. Alanine substitutions in the HV4β region, either did not affect (Ser69 and Lys71), or increased the recognition of SEC2/HLA‐DR1 complex (Asp70), arguing against a general and direct role for the HV4β region in superantigenrecognition. A theoretical‐computational model of the SEC2/TCR Vβ10 chain complex was constructed and predicted the presence of a unique salt bridge between Vβ Asp30 and SEC2 Lys103. A perfect correlation was found between the likely presence of this salt bridge and the capacity of the HV4β and previously obtained CDR1β alanine mutants to induce an equal or greater response than the wild‐type TCR.

Epidermal filaggrin deficiency mediates increased systemic T-helper 17 immune response

“…We found an increased frequency of CD4 + T cells in the lymph nodes expressing TCR Vβ10, a receptor that binds S. aureus superantigen enterotoxin C2, in adult ft/ft mice when compared with adult C57BL6 and BALB/c mice, but also when compared with 2‐week‐old ft/ft mice (Fig. a,b) . This indicates an induced expansion of CD4 + T cells expressing TCR Vβ10 in adult ft/ft mice.…”

“…It was recently suggested that IL‐17‐mediated skin inflammation in ft/ft mice is driven by infections . S. aureus , a common microorganism found on the skin of patients with AD, produces superantigens that bind to specific TCR β chains . Flow cytometric analysis showed an altered TCR β‐chain repertoire in cells from skin‐draining lymph nodes in ft/ft mice when compared with WT controls (Fig.…”

A Mutant of Staphylococcal Enterotoxin C Devoid of Bacterial Superantigenic Activity Elicits a Th2 Immune Response for Protection againstStaphylococcus aureusInfection

“…Since two physicians injected themselves with 3 to 5 g of superantigenic toxin and subsequently developed TSS, it is probable that a very slight infection could induce TSS (37). Several residues of SEC for binding to TCR that are important for superantigenicity have been identified (10,20,22,35). In the present study, we changed N23 of the SEC molecule to A23 and obtained a single-site mutant SEC devoid of superantigenic activity.…”

“…and Q210, for binding to TCR are important for superantigenicity (10,20,22,35). In this study, we changed the N23 residue of SEC2 molecule to A23 (Fig.…”

“…Fields et al (10) reported the crystal structure of an SEC complex with a T-cell receptor (TCR) ␤-chain and showed that SEC2 and SEC3 bind in the same way to the TCR ␤-chain. Recent studies demonstrated that several residues of SEC, including T20, N23, Y90, K103, and Q210, are important for binding to TCR and are also important for superantigenicity (10,20,22,35). Several reports described the toxicities and biological activities of wild-type and mutant SEA, SEB, and toxic shock syndrome toxin 1 (TSST-1) and showed that genetically altered SEA and SEB were immunogenic in mice and rhesus monkeys (1,31,41,43).…”