Characterization and Distribution of a New Enterotoxin-Related Superantigen Produced by <i>Staphylococcus aureus</i>
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Staphylococcal enterotoxins (SEs) are a family of structurally related pyrogenic exotoxins consisting of the five prototypic SEs (types A to E) and three newly characterized SEs (types G to I) produced by <i>Staphylococcus aureus</i> (<i>S. aureus</i>). They also work as superantigens and cause food poisoning and shock symptoms in humans. In this study, we cloned a new variant gene of the <i>seg</i> and characterized its superantigenic properties and distribution among the clinical isolates of <i>S. aureus</i>. The gene encodes a 233 amino acid protein which is highly homologous to SEG (97.7%). The variant SEG (SEGv) expressed by the cloned gene exerted mitogenic activity on human peripheral blood mononuclear cells at the concentration of 100pg/ml. T cells bearing Vβ3, 12, 13.1, 13.2, 14 and 15 were preferentially expanded after stimulation with the recombinant protein. The mRNA of the variant <i>seg</i> gene was detected in the total RNA of the organisms bearing this gene. By PCR, 27 out of 48 clinical isolates of <i>S. aureus</i> (56%) possessed either the <i>seg</i> or variant <i>seg</i> gene. These findings suggest that SEG, or SEGv, is one of the most frequently produced superantigen exotoxins by <i>S. aureus</i> and may participate in the inflammatory process of the host by activating a distinct set of Vβ families of T cells.
- Japanese Journal of Microbiology
Japanese Journal of Microbiology 44(2), 79-88, 2000
Center For Academic Publications Japan