CHAPTER 50 – Staphylococcal superantigens and the diseases they cause

Seventeen years have passed since the superantigen (SAG) concept was proposed for several exotoxins from Staphylococcus aureus (S. aureus), such as toxic shock syndrome (TSS) toxin-1 (TSST-1) and enterotoxin A (SEA) and B (SEB). Recently, staphylococcal and streptococcal species other than S. aureus and S. pyogenes were also reported to produce SAGs. To date, approximately 30 bacterial SAGs have been identified. A remarkable biological feature of SAGs is their capacity to stimulate T cells in vast numbers in a T cell receptor (TCR) Vβ element-specific manner in direct association with MHC class II molecules on antigen-presenting cells (APCs). This chapter reviews the progress in research into newstaphylococcal SAGs and the infectious diseases they cause, focusing on pathogenic mechanisms and early definitive disease diagnosis. Some staphylococcal enterotoxins were originally identified as enterotoxins because of their emetic activity. The international nomenclature committee on staphylococcal SAGs has proposed that only toxins exhibiting emetic activity after oral administration in a primate model be designated staphylococcal enterotoxins. Other related toxins lacking emetic activity or as yet untested for this activity were recommended to be designated "staphylococcal enterotoxin-like toxin type X (SEIX)." Staphylococcal SAGs exhibit potent T cell-stimulating activities that are closely related to the pathogenic mechanisms of TSS and NTED.