Characterization and Distribution of a New Enterotoxin-Related Superantigen Produced by <i>Staphylococcus aureus</i>

J-STAGE
  • Abe Jun
    Department of Child Ecology, National Children's Medical Research Center
  • Ito Yasuhiko
    Department of Allergy and Immunology, National Children's Medical Research Center
  • Onimaru Michiko
    Department of Child Ecology, National Children's Medical Research Center
  • Kohsaka Takao
    Department of Allergy and Immunology, National Children's Medical Research Center
  • Takeda Tae
    Department of Infectious Diseases Research, National Children's Medical Research Center

抄録

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 Staphylococcus aureus (S. aureus). 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 seg and characterized its superantigenic properties and distribution among the clinical isolates of S. aureus. 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 seg gene was detected in the total RNA of the organisms bearing this gene. By PCR, 27 out of 48 clinical isolates of S. aureus (56%) possessed either the seg or variant seg gene. These findings suggest that SEG, or SEGv, is one of the most frequently produced superantigen exotoxins by S. aureus and may participate in the inflammatory process of the host by activating a distinct set of Vβ families of T cells.

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