Bacterial superantigens promote acute nasopharyngeal infection by Streptococcus pyogenes in a human MHC Class II-dependent manner

• Published in: PLoS pathogens Vol. 10; no. 5; p. e1004155
• Main Authors: Kasper, Katherine J, Zeppa, Joseph J, Wakabayashi, Adrienne T, Xu, Stacey X, Mazzuca, Delfina M, Welch, Ian, Baroja, Miren L, Kotb, Malak, Cairns, Ewa, Cleary, P Patrick, Haeryfar, S M Mansour, McCormick, John K
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01-05-2014; Public Library of Science (PLoS)
• Subjects: Acute Disease; Animals; Bacterial Proteins - immunology; Bacterial Proteins - metabolism; Bacteriology; Biology and Life Sciences; Cardiovascular disease; Care and treatment; Cytokines; Development and progression; Exotoxins - immunology; Exotoxins - metabolism; Experiments; Fever; Health aspects; Histocompatibility Antigens Class II - immunology; Humans; Infections; Medical research; Medicine and Health Sciences; Membrane Proteins - immunology; Membrane Proteins - metabolism; Mice, Inbred C57BL; Nasopharynx - immunology; Pathogenesis; Patient outcomes; Receptors, Antigen, T-Cell - immunology; Software; Streptococcal infections; Streptococcal Infections - immunology; Streptococcal Infections - prevention & control; Streptococcus pyogenes - genetics; Streptococcus pyogenes - immunology; Superantigens; Superantigens - genetics; Superantigens - immunology; T-Lymphocytes - immunology; Virulence (Microbiology); United States
• ISSN: 1553-7374; 1553-7366; 1553-7374
• DOI: 10.1371/journal.ppat.1004155

Establishing the genetic determinants of niche adaptation by microbial pathogens to specific hosts is important for the management and control of infectious disease. Streptococcus pyogenes is a globally prominent human-specific bacterial pathogen that secretes superantigens (SAgs) as 'trademark' virulence factors. SAgs function to force the activation of T lymphocytes through direct binding to lateral surfaces of T cell receptors and class II major histocompatibility complex (MHC-II) molecules. S. pyogenes invariably encodes multiple SAgs, often within putative mobile genetic elements, and although SAgs are documented virulence factors for diseases such as scarlet fever and the streptococcal toxic shock syndrome (STSS), how these exotoxins contribute to the fitness and evolution of S. pyogenes is unknown. Here we show that acute infection in the nasopharynx is dependent upon both bacterial SAgs and host MHC-II molecules. S. pyogenes was rapidly cleared from the nasal cavity of wild-type C57BL/6 (B6) mice, whereas infection was enhanced up to ∼10,000-fold in B6 mice that express human MHC-II. This phenotype required the SpeA superantigen, and vaccination with an MHC -II binding mutant toxoid of SpeA dramatically inhibited infection. Our findings indicate that streptococcal SAgs are critical for the establishment of nasopharyngeal infection, thus providing an explanation as to why S. pyogenes produces these potent toxins. This work also highlights that SAg redundancy exists to avoid host anti-SAg humoral immune responses and to potentially overcome host MHC-II polymorphisms.