Unique superantigen activity of staphylococcal exfoliative toxins

Certain strains of Staphylococcus aureus express one or both of two related , but immunologically distinct, exfoliative toxins (ETA and ETB), These tox ins induce the symptoms associated with staphylococcal scalded skin syndrom e, Both ETs have been shown to stimulate T cell proliferation. Recently, it was reported that ETA, is a superantigen that stimulates T cells bearing h uman V beta 2 or several murine V beta s. However, other investigators have proposed that the superantigenicity reported for ETA resulted from contami nants in commercial preparations. This present study addresses those confli cting reports by assessing the biological and immunologic activities of hig hly purified rETs, ETA and ETB required APCs to induce selective polyclonal expansion of several human V beta s (huV beta s), although, neither toxin expanded huV beta 2. ETB induced expansion of murine T cells bearing V beta s 7 and 8. those that have the highest homology to the huV beta s expanded by ETA and ETB. Although how cytometry of ETB-stimulated T cells matched P CR results, stimulation by ETA reduced percentages of T cells positive for several huV beta s that had been shown to hare increased levels of mRNA tra nscripts. Elh and ETB induced contrasting reactions in vivo. In rabbits, ET B was moderately pyrogenic and enhanced susceptibility to lethal shock, whi le ETA lacked both activities, Predictions based on comparisons with other superantigens suggest molecular regions potential?, involved in receptor bi nding in the ETA crystal structure and a modeled ETB three-dimensional stru cture. These results show that ETs are superantigens with unique properties that could account for the discrepancies reported.