Toxic shock syndrome toxin 1 binds to major histocompatibility complex class II molecules.

Abstract

Toxic shock syndrome toxin 1 (TSST-1) is a 22-kDa exotoxin produced by strains of Staphylococcus aureus and implicated in the pathogenesis of toxic shock syndrome. In common with other staphylococcal exotoxins, TSST-1 has diverse immunological effects. These include the induction of interleukin 2 receptor expression, interleukin 2 synthesis, proliferation of human T lymphocytes, and stimulation of interleukin 1 synthesis by human monocytes. Toxic shock syndrome is a severe and often fatal disorder consistently associated with Staphylococcus aureus infection and characterized by multiple organ dysfunction (1-3). The exotoxin toxic shock syndrome toxin 1 (TSST-1) is a 22-kDa protein (4) produced by most strains of S. aureus isolated from patients with toxic shock syndrome (5, 6) and capable of inducing the disease in animal models (7). TSST-1 induces interleukin 1 synthesis by human monocytes (8, 9), accessory-cell-dependent proliferation of human T lymphocytes (10, 11), and the suppression of pokeweed mitogeninduced immunoglobulin synthesis by human lymphocytes (12). All three activities appear to reside in a 14-kDa internal toxin fragment and could not be dissected with multiple monoclonal antibodies (mAbs) (13,14). The identification of a cellular receptor for TSST-1 is important for the understanding of the mechanism of action of this toxin. TSST-1 has been reported to bind to cultured epithelial cells (15) and to T cells but not to monocytes or B cells (16). To the best of our knowledge, the nature of the binding site has not been described. In the present study we demonstrate that TSST-1 binds to human major histocompatibility complex (MHC) class II molecules.MATERIALS AND METHODS Cell Preparations. Peripheral blood mononuclear cells (PBMCs) were isolated by standard methods (11). Highly purified populations of T lymphocytes and monocytes were prepared as described (11,17). The preparation of B cells (18) from surgical specimens of human tonsil and of thymocytes (19) obtained from surgical specimens removed during open heart surgery were as described.Normal human fibroblasts were grown from skin biopsies, propagated, and harvested as described (20). Interferon y (IFN-y) treatment of fibroblasts was performed as described (20) L-Cell Transfectants. The L-cell transfectants expressing HLA class II molecules used in this study were gifts of R. Karr (University of Iowa, IA) and were prepared by transfection of the respective full-length cDNA clones (DRa, DR4f3I, DPw4a, DPw4p, DQ7a, and DQw3,8) in the expression vector pcD together with the pSV2-neo plasmid into DAP.3 murine L-cell fibroblasts (21). Cells were grown in tissue culture plates in complete RPMI 1640 medium containing G418 (250 jug/ml; GIBCO, Grand Island, NY) and were harvested by incubation for 15-20 min in isotonic phosphate-buffered saline (pH 7.4; PBS) containing 0.53 mM EDTA.Toxins. TSST-1 was prepared as described (22) and iodinated using chloramine-T. The mean specific activity of the labeled toxin was 950 Ci/mmol (range, 230-1700 Ci/m...

The staphylococcal toxic shock syndrome toxin 1 triggers B cell proliferation and differentiation via major histocompatibility complex-unrestricted cognate T/B cell interaction.

“…known to inhibit TSST 1 binding to B cells (8), also inhibited TSST 1-triggered B cell responses (data not shown) . In contrast, the anti-HLA-DR and -DQmAb ST259, which had no effect on the binding of TSST1 to B cells, failed to inhibit TSST1-triggered B cell responses.…”

“…The binding of TSST1 to purified B cells was performed as previously described (8) . TSST1 was iodinated using chloramine T and the specific activity of labeled TSST-1 was in the range of950 Ci/mmol.…”

Induction of CC chemokines in human peripheral blood mononuclear cells by staphylococcal exotoxins and its prevention by pentoxifylline

“…Staphylococcal toxic shock syndrome toxin 1 (TSST-1), and the distantly related enterotoxin A (SEA) and enterotoxin B (SEB) are also called superantigens because they induce massive proliferation of T cells. These superantigens bind directly to the major histocompatibility complex class II molecules on antigen-presenting cells (APC) and stimulate T cells expressing specific V␤ elements in the T cell receptors [5,6]. Their interactions with cells of the immune system initiate a massive production of the proinflammatory cytokines, tumor-necrosis factor ␣ (TNF-␣), interferon-␥ (IFN-␥), and interleukin-1 (IL-1).…”

Suppression of Endotoxin- and Staphylococcal Exotoxin-Induced Cytokines and Chemokines by a Phospholipase C Inhibitor in Human Peripheral Blood Mononuclear Cells

“…LPS from gram-negative bacteria binds to serum LPS-binding protein, which then facilitates its binding to the cell surface protein CD14 on monocytes/macrophages and other cells (21). The subsequent interaction of LPS-CD14 complex with Toll-like receptors on these cells initiates transmembrane signaling and cellular activation to secrete cytokines and chemokines (15).Staphylococcal toxic shock syndrome toxin 1 (TSST-1), and the structurally related enterotoxins, are bacterial exotoxins that bind directly to major histocompatibility complex class II molecules on antigen-presenting cells (APC) (4,8,19) and stimulate T cells expressing specific V␤ elements (5, 9). These toxins are called superantigens because of their ability to polyclonally activate large populations of T cells (10).…”

“…Staphylococcal toxic shock syndrome toxin 1 (TSST-1), and the structurally related enterotoxins, are bacterial exotoxins that bind directly to major histocompatibility complex class II molecules on antigen-presenting cells (APC) (4,8,19) and stimulate T cells expressing specific V␤ elements (5, 9). These toxins are called superantigens because of their ability to polyclonally activate large populations of T cells (10).…”