staphylococcus aureus isolates encode variant staphylococcal enterotoxin b proteins that are diverse in superantigenicity and lethality金黄色葡萄球菌分离株葡萄球菌肠毒素b编码变体不同的蛋白质在superantigenicity和杀伤力.pdf

Staphylococcus aureus Isolates Encode Variant Staphylococcal Enterotoxin B Proteins That Are Diverse in Superantigenicity and Lethality 1 1 2 2 3 Petra L. Kohler , Seth D. Greenwood , Suba Nookala , Malak Kotb , David M. Kranz , Patrick M. Schlievert4* 1 Department of Microbiology, University of Minnesota Medical School, Minneapolis, Minnesota, United States of America, 2 Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati Medical School, Cincinnati, Ohio, United States of America, 3 Department of Biochemistry, School of Molecular and Cellular Biology, University of Illinois, Urbana, Illinois, United States of America, 4 Department of Microbiology, University of Iowa Carver College of Medicine, Iowa City, Iowa, United States of America Abstract Staphylococcus aureus produces superantigens (SAgs) that bind and cross-link T cells and APCs, leading to activation and proliferation of immune cells. SAgs bind to variable regions of the b-chains of T cell receptors (Vb-TCRs), and each SAg binds a unique subset of Vb-TCRs. This binding leads to massive cytokine production and can result in toxic shock syndrome (TSS). The most abundantly produced staphylococcal SAgs and the most common causes of staphylococcal TSS are TSS toxin-1 (TSST-1), and staphylococcal enterotoxins B and C (SEB and SEC, respectively). There are several characterized variants of humans SECs, designated SEC1-4, but only one variant of SEB has been described. Sequencing the seb genes from over 20 S. aureus isolates show there are at least five different alleles of seb, encoding forms of SEB with predicted amino acid substitutions outside of the predicted immune-cell binding regions of the SAgs. Examination of purified, variant