Abstract
Superantigens (SAgs) are a class of immunostimulatory exotoxins that activate large numbers of T cells, leading to overproduction of cytokines and subsequent inflammatory reactions and systemic toxicity. Staphylococcal enterotoxin C (SEC), a SAg secreted by Staphylococcus aureus, has been implicated in various illnesses including non-menstrual toxic shock syndrome (TSS) and necrotizing pneumonia. SEC has been shown to cause TSS illness in rabbits and the toxin contributes to lethality associated with methicillin-resistant S.aureus (MRSA) in a rabbit model of pneumonia. With the goal of reducing morbidity and mortality associated with SEC, a high-affinity variant of the extracellular variable domain of the T-cell receptor beta-chain for SEC (~14 kDa) was generated by directed evolution using yeast display. This protein was characterized biochemically and shown to cross-react with the homologous (65% identical) SAg staphylococcal enterotoxin B (SEB). The soluble, high-affinity T-cell receptor protein neutralized SEC and SEB in vitro and also significantly reduced the bacterial burden of an SEC-positive strain of MRSA (USA400 MW2) in an infective endocarditis model. The neutralizing agent also prevented lethality due to MW2 in a necrotizing pneumonia rabbit model. These studies characterize a soluble high-affinity neutralizing agent against SEC, which is cross-reactive with SEB, and that has potential to be used intravenously with antibiotics to manage staphylococcal diseases that involve these SAgs.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Anti-Bacterial Agents / administration & dosage*
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Anti-Bacterial Agents / biosynthesis
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Anti-Bacterial Agents / chemistry
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Cell Line
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Cell Surface Display Techniques
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Directed Molecular Evolution
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Disease Models, Animal
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Endocarditis, Bacterial / drug therapy
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Endocarditis, Bacterial / immunology
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Endocarditis, Bacterial / microbiology
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Enterotoxins / antagonists & inhibitors*
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Enterotoxins / metabolism
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Humans
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Interleukin-2 / metabolism
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Lymphocyte Activation
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Methicillin-Resistant Staphylococcus aureus / immunology
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Methicillin-Resistant Staphylococcus aureus / metabolism
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Pneumonia, Staphylococcal / drug therapy
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Pneumonia, Staphylococcal / immunology
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Pneumonia, Staphylococcal / microbiology
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Protein Binding
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Protein Engineering
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Rabbits
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Receptors, Antigen, T-Cell, alpha-beta / administration & dosage*
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Receptors, Antigen, T-Cell, alpha-beta / biosynthesis
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Receptors, Antigen, T-Cell, alpha-beta / chemistry
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Receptors, Antigen, T-Cell, alpha-beta / genetics
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Recombinant Proteins / administration & dosage
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Recombinant Proteins / biosynthesis
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Recombinant Proteins / chemistry
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Recombinant Proteins / genetics
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Staphylococcal Infections / drug therapy
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Staphylococcal Infections / immunology
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Staphylococcal Infections / microbiology
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Superantigens / metabolism*
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Superantigens / pharmacology
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T-Lymphocytes / drug effects
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T-Lymphocytes / immunology
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T-Lymphocytes / metabolism
Substances
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Anti-Bacterial Agents
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Enterotoxins
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Interleukin-2
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Receptors, Antigen, T-Cell, alpha-beta
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Recombinant Proteins
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Superantigens
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enterotoxin C, staphylococcal