Genome biology of staphylococcal enterotoxin family

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In recent years, many new staphylococcal enterotoxins (SEs) have been reported. It has been known that certain SE genes are associated with mobile genetic elements such as pathogenicity islands, prophages, and plasmids. These facts imply that superantigenic toxin genes are transferred horizontally between staphylococcal strains. There is a possibility that these mobile genetic elements have played an important role in the evolution of S.aureus as a pathogen. To investigate pathobiology and epidemiology of these newly identified SEs, we had undertaken studies shown hi below.1.We have developed a comprehensive detection system for 18 kinds of classical and newly described staphylococcal superantigenic toxin genes using four sets of multiplex PCR. Analysis of the relationship between toxin genotypes and toxin genes encoding profiles of mobile genetic elements suggests its possible role in determining superantigenic toxin genotypes in S.aureus as combinations of toxin gene-encoding mobile … More genetic elements. Subsequently, we investigated new type of SE-encoding pathogenicity islands using PFGE/southern method. We have found that SEB-encoding islands are classified into at least 3 groups.2.We have determined complete nucleotides sequence of sed, selj and selj encoding plasmid, p196,using transposomics strategy. This plasmid is encoding penicillin resistance operon and Cd-resistance operon, in addition to three kinds of SE (SE1) genes.3.We characterized a novel staphylococcal entertoxin (SE)-like putative toxin SE1R and SE1P. The SE1R protein showed significant T cell stimulation activity. MHC class II molecules were required for T cell stimulation by SER. SER stimulated T cells bearing receptors Vβ 3,11,12,13.2, and 14. These results suggested that SER acts as a superantigen. SE1P induced a substantial proliferative response and the production of cytokines IL-2,EFN-γ,TNF-α, and IL-4 from human T cells when administered at a concentration of 0.4 pM or more. The expression of MHC class II molecules on accessory cells was required for T cell stimulation by SE1P. SE1P selectively stimulated a vast number of human T cells bearing receptors Vβ 5.1,6,8,16,18, and 21.3. These results indicated that SE1P acts as a superantigen. SE1P proved to be emetic in the house musk shrew emetic assay, although at a relatively high dose. We investigated whether immunization with non-toxic mutant SEC (mSEC), devoid of superantigenic activity, can protect against S.aureus infection. Immunization with mSEC devoid of superantigenic properties provides protection against S.aureus infection and the protection might be mediated by the IL-10 and IL-4 induction and down-regulation of IFN-γ, as well as SEC neutralizing antibodies. Also, we demonstrate that staphylococcal SEA induces an increase in intracellular calcium ([Ca^<2+>]i) in human intestinal epithelial cells and the [Ca^<2+>]i is released from intracellular stores. Less