Functional Analysis of the TCR Binding Domain of Toxic Shock Syndrome Toxin-1 Predicts Further Diversity in MHC Class II/Superantigen/TCR Ternary Complexes

Staphylococcal toxic shock syndrome toxin-1 (TSST-1) is implicated in the pathogenesis of superantigen-mediated shock. We previously identified TSST-1 residues G31/S32 to be important for major histocompatibility complex (MHC) class II binding, as well as superantigenic and lethal activities. However, the site-directed TSST-1 mutant toxin, G31R, could still induce mitogenesis and low-level TNFalpha secretion, suggesting that additional MHC class II binding sites other than G31/S32 may exist. In the current study, a TSST-1-neutralizing monoclonal antibody, MAb5, was found to inhibit TSST-1 binding to human peripheral blood mononuclear cells, neutralize TSST-1-induced mitogenesis and cytokine secretion, and protect against TSST-1-induced lethality in vivo. Epitope mapping revealed that MAb5 bound to TSST-1 residues 51-56 (T(51-56);51YYSPAF56). Peptide T(51-56) was synthesized and found to also inhibit TSST-1 binding to human monocytes as well as TSST-1-induced mitogenesis, cytokine secretion, and lethality in vivo. This T(51-56) epitope, located within the beta3/beta4 loop, and the previously identified G31/S32 epitope, within the beta1/beta2 loop of TSST-1, are separated within the primary sequence, but spatially juxtaposed to each other. Collectively, these findings suggest that a discontinuous epitope comprising of regions within both the beta1/beta2 and beta3/beta4 loops, are critical for MHC class II binding, and the consequent superantigenic and lethal activities of TSST-1.

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Identification of MHC Class II-Associated Peptides That Promote the Presentation of Toxic Shock Syndrome Toxin-1 to T Cells

The Journal of Immunology ◽

10.4049/jimmunol.166.11.6514 ◽

2001 ◽

Vol 166 (11) ◽

pp. 6514-6522 ◽

Cited By ~ 12

Author(s):

Robert J. Hogan ◽

Josine VanBeek ◽

Dana R. Broussard ◽

Sherri L. Surman ◽

David L. Woodland

Keyword(s):

T Cells ◽

Mhc Class Ii ◽

Toxic Shock Syndrome ◽

Class Ii ◽

Toxic Shock ◽

Toxic Shock Syndrome Toxin

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Identification of class II major histocompatibility complex and T cell receptor binding sites in the superantigen toxic shock syndrome toxin 1.

Journal of Experimental Medicine ◽

10.1084/jem.181.6.2229 ◽

1995 ◽

Vol 181 (6) ◽

pp. 2229-2235 ◽

Cited By ~ 38

Author(s):

J M Hurley ◽

R Shimonkevitz ◽

A Hanagan ◽

K Enney ◽

E Boen ◽

...

Keyword(s):

T Cell ◽

T Cell Receptor ◽

Binding Sites ◽

Toxic Shock Syndrome ◽

Cell Receptor ◽

Class Ii ◽

Toxic Shock ◽

Mhc Molecules ◽

Histocompatibility Complex ◽

Toxic Shock Syndrome Toxin

Superantigens, in association with class II major histocompatibility complex (MHC) molecules, activate T cells bearing particular beta chain variable domains of the T cell receptor (TCR). Unlike conventional peptide antigens, superantigens bind as intact proteins to TCR and MHC molecules outside their peptide binding sites. To characterize these interactions at the molecular level, random point mutations were generated in the gene encoding toxic shock syndrome toxin 1, a bacterial superantigen associated with toxic shock syndrome. Functionally impaired mutants were identified based on their lack of murine and human T cell stimulatory activities, and experiments analyzing binding to human histocompatibility leukocyte antigen-DR molecules differentiated residues involved in MHC from TCR binding. The results showed that the great majority of mutations are clustered in two distinct regions of the toxic shock syndrome toxin 1 molecule. The class II MHC binding site is located in the hydrophobic region of the NH2-terminal domain, and the TCR binding site is primarily in the major central groove of the COOH-terminal domain. These studies provide insight into the interactions necessary for superantigen-mediated disease in humans.

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Sequences in both class II major histocompatibility complex alpha and beta chains contribute to the binding of the superantigen toxic shock syndrome toxin 1.

Journal of Experimental Medicine ◽

10.1084/jem.175.5.1301 ◽

1992 ◽

Vol 175 (5) ◽

pp. 1301-1305 ◽

Cited By ~ 19

Author(s):

N S Braunstein ◽

D A Weber ◽

X C Wang ◽

E O Long ◽

D Karp

Keyword(s):

Major Histocompatibility Complex ◽

T Cell ◽

Toxic Shock Syndrome ◽

Cell Receptor ◽

Class Ii ◽

Major Histocompatibility ◽

Toxic Shock ◽

Mhc Molecules ◽

Histocompatibility Complex ◽

Toxic Shock Syndrome Toxin

Class II major histocompatibility complex (MHC) molecules present peptides derived from processed antigen to antigen-specific CD4-positive T cells. In addition, class II molecules bind with high affinity another class of antigens, termed superantigens. T cell stimulation by superantigens depends almost exclusively on the V beta segment expressed by the T cell receptor (TCR). Mapping of the superantigen binding site on class II molecules should provide valuable information on how MHC and TCR molecules interact. Recombinant mouse I-A class II molecules expressed on transfected L cells were analyzed for their ability to bind the toxic shock syndrome toxin 1. Polymorphic residues in the alpha helices of both the alpha and beta chains of I-A contributed to quantitative toxin binding, suggesting that the toxin binds to either a combinatorial or a conformational site on class II MHC molecules.

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

Journal of Experimental Medicine ◽

10.1084/jem.170.6.2011 ◽

1989 ◽

Vol 170 (6) ◽

pp. 2011-2022 ◽

Cited By ~ 60

Author(s):

W Mourad ◽

P Scholl ◽

A Diaz ◽

R Geha ◽

T Chatila

Keyword(s):

Cell Proliferation ◽

B Cells ◽

B Cell ◽

Mhc Class Ii ◽

Cell Interaction ◽

Class Ii ◽

Toxic Shock ◽

Cell Proliferation And Differentiation ◽

Proliferation And Differentiation ◽

Toxic Shock Syndrome Toxin

The Staphylococcus aureus exotoxin toxic shock syndrome toxin 1 (TSST-1) is a potent activator of T cells and monocytes. We have recently demonstrated that TSST-1 is a superantigen that binds monomorphic determinants on MHC class II molecules. In the present study, we have examined the effect of TSST-1 on the activation and differentiation of high density human tonsillar B cells. TSST-1 bound to tonsilar B cells with high affinity and saturation kinetics. This binding was effectively inhibited by a combination of anti-HLA-DR and anti-HLA-DQ mAbs. Treatment of purified B cells with TSST-1 failed to induce B cell proliferation or Ig production. However, in the presence of irradiated T cells, TSST-1 induced resting B cells to proliferate and differentiate into Ig secretory cells. TSST-1 mimicked nominal antigen in that its induction of B cell responses was strictly dependent on physical contact between T and B cells, and was profoundly inhibited by anti-MHC class II mAbs, anti-CD3 mAbs, and, to a lesser extent, by anti-CD18 mAbs. However, unlike nominal antigen, TSST-1-mediated T/B cell interactions were MHC unrestricted. These results suggest that TSST-1 induces T cell-dependent B cell proliferation and differentiation by virtue of its ability to mediate MHC-unrestricted cognate T/B cell interaction via the TCR/CD3 complex and MHC class II antigens.

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