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Infect. Immun. doi:10.1128/IAI.00045-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Identification and characterization of two novel staphylococcal enterotoxins types S and T

Department of Veterinary Medicine, Faculty of Agriculture, Iwate University, Ueda 3-18-8, Morioka, Iwate 020-8550, Japan; Department of Microbiology and Immunology, Tokyo Women's Medical University School of Medicine, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan; Department of Microbiology and Immunology, Hirosaki University Graduate School of Medicine, 5 Zaifu-cho, Hirosaki 036-8562, Japan; The Corporation for Production and Research of Laboratory Primates, Hachimandai 1-1, Tsukuba, Ibaraki 305-0843, Japan

^* To whom correspondence should be addressed. Email: omo{at}iwate-u.ac.jp.

	Abstract

Two novel genes coding for two superantigens, staphylococcal enterotoxins S and T (SES and SET) were identified in staphylococcal entertoxin-like toxin genes (selj and selr) encoding plasmid pF5, which is harbored by Staphylococcus aureus strain Fukuoka 5. This strain was implicated in a food-poisoning incident in Fukuoka City, Japan, in 1997. Recombinant (r)SES specifically stimulated human T cells in T cell receptor (TCR) V9- and V16-specific manner in the presence of MHC class II⁺ antigen presenting cells (APCs). rSET also stimulated T cells in the presence of MHC class II⁺ APC, although its V skewing was not found in reactive T cells. Subsequently, we examined the emetic activity of SES and SET. We also studied SElR to determine emetic activity in primates. This toxin was identified in previous studies but not examined in terms of possessing emetic activity for primates. rSES induced emetic reactions in 2 of 4 monkeys at a dose of 100 µg/kg within 5 hours of intragastric administration. In one monkey, rSET induced a delayed reaction (24 hours post-administration) at a dose of 100 µg/kg and in the other one, reaction occurred 5 days post-administration. rSElR induced reaction in 2 of 6 animals within 5 hours at 100 µg/kg. On this basis, we speculate that the causative toxins of vomiting in the Fukuoka case are SES and SER. Additionally, SES, SER, and SET also induced emesis in house musk shrews as in the monkeys.