Activation of in vitro proliferation of human T cells by a synthetic peptide of toxic shock syndrome toxin 1

A 21-mer synthetic peptide (KGEKVDLNTKRTKKSQHTSEG), designated TSST-1(58-78), was constructed from the primary structure of the toxic shock syndrome toxin 1 (TSST-1). The peptide reacted with a panel of neutralizing monoclonal Antibodies (MAbs) to whole TSST-1 in solid-phase immunoassays. TSST-1(58-78) promoted the in vitro proliferation of human peripheral blood mononuclear cells (PBMC) in a dose-dependent manner. Minimum dose required for stimulation (P less than or equal to .05 microM) was 0.75 microM peptide. This mitogenic effect was abrogated by incubation of the peptide with MAbs to whole TSST-1 before addition to PBMC. The ability of TSST-1(58-78) to stimulate the proliferation of highly purified resting human T cells was analyzed. Significant proliferation (P less than or equal to .01) was observed only in the presence of increasing populations of monocytes added to the cultures. Adherent human monocytes exposed to TSST-1(58-78) released tumor necrosis factor. Thus, some of the immunoregulatory properties attributed to TSST-1 are demonstrated by the region of the toxin represented by the peptide TSST-1(58-78).