The T Cell Receptor β-Chain Second Complementarity Determining Region Loop (CDR2β) Governs T Cell Activation and Vβ Specificity by Bacterial Superantigens

Rahman, Ashrafur; Bonsor, Daniel A.; Herfst, Christine A.; Pollard, Fraser; Peirce, Michael; Wyatt, Aaron W.; Kasper, Katherine J.; Madrenas, Joaquı́n; Sundberg, Eric J.; McCormick, John K.

doi:10.1074/jbc.m110.189068

Cited by 17 publications

(17 citation statements)

References 47 publications

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“…Human iNKT cells express Vb11 in their canonical TCR and from a molecular perspective, it is understandable that SEB would recognize human Vb11. The TCR b-chain CDR2 loop is the critical factor for Vb-specificity by diverse bacterial Sags, 51 and although the CDR2 loops of mouse Vbs 8.2, 7 and 2 show little sequence similarity, human Vb11 is orthologous to mouse Vb8.2 and they both share very similar CDR2b loop sequences. 15 However, previous investigations did not detect any Vb11 expansion in response to a number of staphylococcal SAgs including those tested in our study.…”

Section: Discussionmentioning

confidence: 99%

CD1d‐independent activation of mouse and human iNKT cells by bacterial superantigens

et al. 2011

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Invariant NKT (iNKT) cells are infrequent but important immunomodulatory lymphocytes that exhibit CD1d-restricted reactivity with glycolipid Ags. iNKT cells express a unique T-cell receptor (TCR) composed of an invariant a-chain, paired with a limited range of b-chains. Superantigens (SAgs) are microbial toxins defined by their ability to activate conventional T cells in a TCR b-chain variable domain (Vb)-specific manner. However, whether iNKT cells are directly activated by bacterial SAgs remains an open question. Herein, we explored the responsiveness of mouse and human iNKT cells to a panel of staphylococcal and streptococcal SAgs and examined the contribution of major histocompatibility complex (MHC) class II and CD1d to these responses. Bacterial SAgs that target mouse Vb8, such as staphylococcal enterotoxin B (SEB), were able to activate mouse hybridoma and primary hepatic iNKT cells in the presence of mouse APCs expressing human leukocyte antigen (HLA)-DR4. iNKT cell-mediated cytokine secretion in SEB-challenged HLA-DR4-transgenic mice was CD1d-independent and accompanied by a high interferon-c:interleukin-4 ratio consistent with an in vivo Th1 bias. Furthermore, iNKT cells from SEB-injected HLA-DR4-transgenic mice, and iNKT cells from SEB-treated human PBMCs, showed early activation by intracellular cytokine staining and CD69 expression. Unlike iNKT cell stimulation by a-galactosylceramide, stimulation by SEB did not induce TCR downregulation of either mouse or human iNKT cells. We conclude that Vb8-targeting bacterial SAgs can activate iNKT cells by utilizing a novel pathway that requires MHC class II interactions, but not CD1d. Therefore, iNKT cells fulfill important effector functions in response to bacterial SAgs and may provide attractive targets in the management of SAg-induced illnesses.

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Section: Discussionmentioning

confidence: 99%

CD1d‐independent activation of mouse and human iNKT cells by bacterial superantigens

et al. 2011

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“…Cloning of SpeC into the pET-41a vector has been described [55], and SmeZ was cloned in a similar manner to SpeC. All recombinant SAgs were produced by 200 µM isopropyl β-D-1-thiogalactopyranoside (IPTG)-induced expression in E. coli BL21(DE3), purified via nickel affinity chelation chromatography, and His 6 tags were removed using autoinactivation resistant His 6 ::TEV protease [56], as described [57], [58].…”

Section: Methodsmentioning

confidence: 99%

Bacterial Superantigens Promote Acute Nasopharyngeal Infection by Streptococcus pyogenes in a Human MHC Class II-Dependent Manner

et al. 2014

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Establishing the genetic determinants of niche adaptation by microbial pathogens to specific hosts is important for the management and control of infectious disease. Streptococcus pyogenes is a globally prominent human-specific bacterial pathogen that secretes superantigens (SAgs) as ‘trademark’ virulence factors. SAgs function to force the activation of T lymphocytes through direct binding to lateral surfaces of T cell receptors and class II major histocompatibility complex (MHC-II) molecules. S. pyogenes invariably encodes multiple SAgs, often within putative mobile genetic elements, and although SAgs are documented virulence factors for diseases such as scarlet fever and the streptococcal toxic shock syndrome (STSS), how these exotoxins contribute to the fitness and evolution of S. pyogenes is unknown. Here we show that acute infection in the nasopharynx is dependent upon both bacterial SAgs and host MHC-II molecules. S. pyogenes was rapidly cleared from the nasal cavity of wild-type C57BL/6 (B6) mice, whereas infection was enhanced up to ∼10,000-fold in B6 mice that express human MHC-II. This phenotype required the SpeA superantigen, and vaccination with an MHC –II binding mutant toxoid of SpeA dramatically inhibited infection. Our findings indicate that streptococcal SAgs are critical for the establishment of nasopharyngeal infection, thus providing an explanation as to why S. pyogenes produces these potent toxins. This work also highlights that SAg redundancy exists to avoid host anti-SAg humoral immune responses and to potentially overcome host MHC-II polymorphisms.

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“…Cells were resuspended in 10 mM Tris-HCl-500 mM NaCl (pH 7.5) and lysed at 25,000 lb/in 2 using a cell disruptor (Constants Systems, Ltd.). The His 6 -tagged proteins were purified using nickel column chromatography using a previously described protocol (26). The purified SaeR and SaeS c were dialyzed in buffers consisting of 10 mM Tris-HCl, 138 mM NaCl, and 2.7 mM KCl (pH 7.5) and 50 mM Tris-HCl, 50 mM KCl, and 1 mM MgCl 2 (pH 8.0), respectively (27), and concentrated up to 10-fold using Amicon centrifugal filter devices (Millipore).…”

Section: Methodsmentioning

confidence: 99%

The SaeRS Two-Component System Is a Direct and Dominant Transcriptional Activator of Toxic Shock Syndrome Toxin 1 in Staphylococcus aureus

et al. 2016

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Toxic shock syndrome toxin 1 (TSST-1) is a Staphylococcus aureus superantigen that has been implicated in both menstrual and nonmenstrual toxic shock syndrome (TSS). Despite the important role of TSST-1 in severe human disease, a comprehensive understanding of staphylococcal regulatory factors that control TSST-1 expression remains incomplete. The S. aureus exotoxin expression (Sae) operon contains a well-characterized two-component system that regulates a number of important exotoxins in S. aureus, although regulation of TSST-1 by the Sae system has not been investigated. We generated a defined deletion mutant of the Sae histidine kinase sensor (saeS) in the prototypic menstrual TSS strain S. aureus MN8. Mutation of saeS resulted in a complete loss of TSST-1 expression. Using both luciferase reporter experiments and quantitative real-time PCR, we demonstrate that the Sae system is an important transcriptional activator of TSST-1 expression. Recombinant SaeR was able to bind directly to the tst promoter to a region containing two SaeR consensus binding sites. Although the stand-alone SarA transcriptional regulator has been shown to be both a positive and a negative regulator of TSST-1, deletion of sarA in S. aureus MN8 resulted in a dramatic overexpression of TSST-1. As expected, mutation of agr also reduced TSST-1 expression, but this phenotype appeared to be independent of Sae. A double mutation of saeS and sarA resulted in the loss of TSST-1 expression. This work indicates that the Sae system is a dominant and direct transcriptional activator that is required for expression of TSST-1. IMPORTANCEThe TSST-1 superantigen is an exotoxin, produced by some strains of S. aureus, that has a clear role in both menstrual and nonmenstrual TSS. Although the well-characterized agr quorum sensing system is a known positive regulator of TSST-1, the molecular mechanisms that directly control TSST-1 expression are only partially understood. Our studies demonstrate that the Sae two-component regulatory system is a positive transcriptional regulator that binds directly to the TSST-1 promoter, and furthermore, our data suggest that Sae is required for expression of TSST-1. This work highlights how major regulatory circuits can converge to fine-tune exotoxin expression and suggests that the Sae regulatory system may be an important target for antivirulence strategies. Staphylococcus aureus is both a common commensal of humans and a prominent bacterial pathogen that is responsible for an assortment of illnesses ranging from self-limiting superficial infections to life-threatening invasive diseases (1). While most infections caused by S. aureus involve the coordinated expression of numerous virulence factors, a few select diseases, including staphylococcal scalded skin syndrome, food poisoning, and toxic shock syndrome (TSS), require the expression of specific staphylococcal exotoxins (2).Staphylococcal TSS is a rare but devastating disease that is caused by S. aureus strains that secrete high levels of superantigens. Super...

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The T Cell Receptor β-Chain Second Complementarity Determining Region Loop (CDR2β) Governs T Cell Activation and Vβ Specificity by Bacterial Superantigens

Cited by 17 publications

References 47 publications

CD1d‐independent activation of mouse and human iNKT cells by bacterial superantigens

CD1d‐independent activation of mouse and human iNKT cells by bacterial superantigens

Bacterial Superantigens Promote Acute Nasopharyngeal Infection by Streptococcus pyogenes in a Human MHC Class II-Dependent Manner

The SaeRS Two-Component System Is a Direct and Dominant Transcriptional Activator of Toxic Shock Syndrome Toxin 1 in Staphylococcus aureus

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