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Toxins 2018, 10(4), 139; https://doi.org/10.3390/toxins10040139

Characterization of Human Type C Enterotoxin Produced by Clinical S. epidermidis Isolates

1
Institut de Bactériologie, 3 rue Koeberlé, Université de Strasbourg, CHRU Strasbourg, Fédération de Médecine Translationnelle de Strasbourg, VBP EA 7290, F-67000 Strasbourg, France
2
Laboratoire de Microbiologie du Centre National Hospitalier et Universitaire Hubert Koutoukou-Maga, Cotonou 01 BP 386, Benin
3
Faculté des Sciences et Techniques, Laboratoire de Biologie et de Typage Moléculaire en Microbiologie, Université d’Abomey, Calavi, Cotonou 05 BP 1604, Benin
*
Author to whom correspondence should be addressed.
Received: 5 March 2018 / Revised: 19 March 2018 / Accepted: 20 March 2018 / Published: 27 March 2018
(This article belongs to the Section Bacterial Toxins)
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Abstract

Staphylococcal Enterotoxins (SEs) are superantigens (SAg) originally produced by S. aureus, but their presence in coagulase negative staphylococci (CNS) has long been suspected. This study aims to better characterize a novel C-like enterotoxin expressed by clinical S. epidermidis strains, called SECepi. We isolated and characterized SECepi for its molecular and functional properties. The toxin was structurally modeled according to its significant similarity with S. aureus SEC3. Most of SEC amino acid residues important for the formation of the trimolecular Major Histocompatibility Complex II MHCII–SEC–T Cell Receptor TCR complex are conserved in SECepi. The functional properties of SECepi were estimated after cloning, expression in E. coli, and purification. The recombinant SECepi toxin exhibits biological characteristics of a SAg including stimulation of human T-cell mitogenicity, inducing and releasing high cytokines levels: IL-2, -4, -6, -8, -10, IFN-γ, TNF-α and GM-CSF at a dose as low as 3.7 pM. Compared to SECaureus, the production of pro-sepsis cytokine IL-6 is significantly higher with SECepi-activated lymphocytes. Furthermore, SECepi is stable to heat, pepsin or trypsin hydrolysis. The SECepi superantigen produced by CNS is functionally very close to that of S. aureus, possibly inducing a systemic inflammatory response at least comparable to that of SECaureus, and may account for S. epidermidis pathogenicity. View Full-Text
Keywords: enterotoxins; superantigens; coagulase-negative staphylococci; S. epidermidis; mitogenicity; cytokines enterotoxins; superantigens; coagulase-negative staphylococci; S. epidermidis; mitogenicity; cytokines
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Nanoukon, C.; Affolabi, D.; Keller, D.; Tollo, R.; Riegel, P.; Baba-Moussa, L.; Prévost, G. Characterization of Human Type C Enterotoxin Produced by Clinical S. epidermidis Isolates. Toxins 2018, 10, 139.

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