MAIT Cells Are Major Contributors to the Cytokine Response in Group A Streptococcal Toxic Shock Syndrome

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 116; no. 51; pp. 25923 - 25931
• Main Authors: Emgård, Johanna, Bergsten, Helena, McCormick, John K., Barrantes, Israel, Skrede, Steinar, Sandberg, Johan K., Norrby-Teglund, Anna
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 17.12.2019
• Series: PNAS Plus
• Subjects: Adult; Aged; Antigens; Biological Sciences; Biosynthesis; CD25 antigen; CD38 antigen; CD69 antigen; Cell activation; Cytokines; Cytokines - blood; Cytokines - metabolism; Depletion; Histocompatibility antigen HLA; HLA-DR Antigens - metabolism; Human behavior; Humans; IL-1β; Interferon-gamma - metabolism; Interleukin 12; Interleukin 18; Interleukin 2; Interleukin-12 - metabolism; Interleukin-18 - metabolism; Interleukin-1alpha - metabolism; Interleukin-2 - metabolism; Lymphocytes; Lymphocytes T; Lymphotoxin-alpha - metabolism; Medicin och hälsovetenskap; Metabolites; Microorganisms; Middle Aged; Mucosa; Mucosal-Associated Invariant T Cells - immunology; Pathogenesis; Peripheral blood mononuclear cells; PNAS Plus; Receptors, Antigen, T-Cell, alpha-beta - metabolism; Riboflavin; Riboflavin - biosynthesis; Septic shock; Shock, Septic - immunology; Streptococcal Infections - immunology; Streptococcal toxic shock syndrome; Streptococcus; Streptococcus pyogenes - immunology; Streptococcus pyogenes - pathogenicity; Superantigens; Superantigens - metabolism; T cell receptors; Toxic shock syndrome; Tumor necrosis factor; γ-Interferon; cytokine; Streptococcus pyogenes; MAIT cells; superantigens
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.1910883116

Streptococcal toxic shock syndrome (STSS) is a rapidly progressing, life-threatening, systemic reaction to invasive infection caused by group A streptococci (GAS). GAS superantigens are key mediators of STSS through their potent activation of T cells leading to a cytokine storm and consequently vascular leakage, shock, and multiorgan failure. Mucosal-associated invariant T (MAIT) cells recognize MR1-presented antigens derived from microbial riboflavin biosynthesis and mount protective innate-like immune responses against the microbes producing such metabolites. GAS lack de novo riboflavin synthesis, and the role of MAIT cells in STSS has therefore so far been overlooked. Here we have conducted a comprehensive analysis of human MAIT cell responses to GAS, aiming to understand the contribution of MAIT cells to the pathogenesis of STSS. We show that MAIT cells are strongly activated and represent the major T cell source of IFNγ and TNF in the early stages of response to GAS. MAIT cell activation is biphasic with a rapid TCR Vβ2-specific, TNF-dominated response to superantigens and a later IL-12- and IL-18-dependent, IFNγ-dominated response to both bacterial cells and secreted factors. Depletion of MAIT cells from PBMC resulted in decreased total production of IFNγ, IL-1β, IL-2, and TNFβ. Peripheral blood MAIT cells in patients with STSS expressed elevated levels of the activation markers CD69, CD25, CD38, and HLA-DR during the acute compared with the convalescent phase. Our data demonstrate that MAIT cells are major contributors to the early cytokine response to GAS, and are therefore likely to contribute to the pathological cytokine storm underlying STSS.