Staphylococcus aureus produces a family of at least 21 distinct superantigens (SAgs) which include staphylococcal enterotoxins (SEs), staphylococcal enterotoxin-like toxins (SEls), and toxic shock syndrome toxin-1 (TSST-1), and contribute to disease pathogenesis via modulation of the host immune response. Specific SAgs have been shown to cause toxinoses such as staphylococcal food poisoning and toxic shock syndrome, and have been implicated in immunological disorders such as rheumatoid arthritis, psoriasis, and Kawasaki syndrome. However the role of SAgs in disease pathogenesis, in general, is poorly understood. S. aureus is a common cause of bovine mastitis. Analysis of the genome sequence of the bovine strain RF122 revealed genes encoding bovine variants of characterized SAgs, TSST-1, SElL, SEC, SEG, SEI, SElU, SElO, SElN and a truncated form of SElM. In addition we identified 3 genes with sequence homology to characterized SAgs, which are predicted to encode novel SAgs, SElX, SElY and SElZ. Expression of all 11 predicted SAg genes was detected in vitro, including several with growth phase-dependent expression. Characterization of a novel SAg, SElX which is encoded in the core genome of 94% of phylogenetically diverse S. aureus strains from human and animal infections was carried out. In addition to its superantigenic properties, SElX has a unique predicted structure characterized by a truncated SAg B domain. At least 14 different alleles of the selx gene were identified among the common human and animal pathogenic clones, and evidence for assortive recombination of selx alleles between distinct clonal lineages was discovered. SElX was expressed by representative human, bovine and ovine strains in vitro, in a growth phase dependent manner, and during human, bovine and ovine infections, consistent with a broad role in the pathogenesis of different S. aureus diseases in multiple hosts. SElX produced by bovine- and ovine-specialized S. aureus strains had 10-fold greater mitogenic activity and a distinct V activation profile for bovine lymphocytes compared to SElX made by the human strain USA300 indicating functional diversification of selx alleles from different hosts. This is the first description of a core-genome encoded SAg of S. aureus. The discovery that the great majority of S. aureus clinical isolates have superantigenic capacity has important implications for our understanding of staphylococcal disease pathogenesis. To investigate the role of SAgs in disease pathogenesis, a SAg-deficient strain of S. aureus, RF122-8 was constructed by sequential allele replacement. RF122-encoded SAg genes were cloned into the pALC2073 plasmid, which has an inducible promoter allowing controlled expression in the SAg-deficient strain RF122-8. These constructs allowed us to determine that TSST-1bov, SElLbov, SECbov, SElNbov, SEIbov and novel SAgs, SElXbov and SElYbov were mitogenic for bovine Tcells, and stimulated T-cell receptor variable (TRBV) sub-family-specific activation. Preliminary experimental intra-mammary infections of dairy cows revealed that clinical symptoms were similar during infection with wild type RF122 and SAg-deficient strains, including high somatic cell counts (6 LogSCC), and elevated body temperature (106 °F). However a higher infectious dose was required to establish infection with the SAg-deficient strain RF122-8 in comparison to the wild type, RF122 indicating an attenuation of virulence. Overall, these data provide broad new insights into the importance of SAgs in staphylococcal disease pathogenesis.

Lactobacillus casei cell wall extract (LCWE)- induced coronary arteritis in mice models Kawasaki disease (KD). LCWE injections consist of T-cell dependent factors that expand superantigen (SAg)-activated T-cell receptor (TCR) Vβ6+ cells, and T-cell independent factors (i.e. TLR2 activity) that localize and sustain the immune response. TLR2 can upregulate costimulatory molecules to rescue SAg-activated T-cells from apoptosis. Accordingly, SAg-activated costimulation-rescued TCRVβ6+ cells are predicted to express activation markers, produce cytokines and be able to induce coronary arteritis. MAM was identified as a SAg able to activate TCRVβ6+ cells in a manner similar to LCWE; however a combination of MAM and TLR2 agonist Pam3Cys could not induce coronary arteritis. As another marker of disease, leukocyte recruitment molecule expression in the hearts of MAM+Pam3Cys- injected mice was found to be lower than in LCWE- injected mice. Therefore, LCWE contains unique features beyond TCRVβ6 stimulation and TLR2 activity that are important for disease induction.

Lactobacillus casei cell wall extract (LCWE)- induced coronary arteritis in mice models Kawasaki disease (KD). LCWE injections consist of T-cell dependent factors that expand superantigen (SAg)-activated T-cell receptor (TCR) Vβ6+ cells, and T-cell independent factors (i.e. TLR2 activity) that localize and sustain the immune response. TLR2 can upregulate costimulatory molecules to rescue SAg-activated T-cells from apoptosis. Accordingly, SAg-activated costimulation-rescued TCRVβ6+ cells are predicted to express activation markers, produce cytokines and be able to induce coronary arteritis. MAM was identified as a SAg able to activate TCRVβ6+ cells in a manner similar to LCWE; however a combination of MAM and TLR2 agonist Pam3Cys could not induce coronary arteritis. As another marker of disease, leukocyte recruitment molecule expression in the hearts of MAM+Pam3Cys- injected mice was found to be lower than in LCWE- injected mice. Therefore, LCWE contains unique features beyond TCRVβ6 stimulation and TLR2 activity that are important for disease induction.

Thesis (Ph. D.)--University of Washington, 1997. / Vita. Includes bibliographical references (leaves [113]-133).

Thesis (Ph. D., Microbiology, Molecular Biology, and Biochemistry)--University of Idaho, July 2007. / Major professor: Gregory A. Bohach. Includes bibliographical references. Also available online (PDF file) by subscription or by purchasing the individual file.

Thesis (Ph.D )--University of Tennessee Health Science Center, 2008. / Title from title page screen (viewed on Sept. 17 2008). Research advisor: Malak Y. Kotb, Ph.D. Document formatted into pages (xvii, 189 p. : ill.). Vita. Abstract. Includes bibliographical references (p. 161-189).

Staphylococcus aureus is the leading cause of infective endocarditis in the United States. Infective endocarditis (IE) is defined as an infection of the endocardium, typically involving the heart valves. The hallmark features of IE are vegetations. Vegetations are cauliflower-like, stratified biofilms of bacteria and host factors that develop on the valve leaflets of the heart. The mechanisms of how vegetations form are not well understood, and as a consequence the bacterial factors that are important for development of IE are not well defined. My studies focus on the role of a family of S. aureus exoproteins known as superantigens and their role in IE. Superantigens (SAgs) are a class of secreted virulence factors that have been extensively studied for their role in systemic diseases such as toxic shock syndrome (TSS), pneumonia, and food poisoning. The SAg protein family is comprised of 23 distinct members designated as staphylococcal enterotoxin (SE) or enterotoxin-like (SEl) and toxic shock syndrome toxin-1 (TSST-1). The term superantigen is derived from the ability of SAgs to interact with the immune system, resulting in a nearly 3000-fold increase in activation when compared to standard antigens. SAgs have a defined structure that is composed of 2 domains, a carboxy-terminal beta-grasp domain and amino-terminal oligosaccharide/oligonucleotide binding (OB) fold. Defined groups of SAgs are associated with S. aureus strains isolated from specific diseases, but few studies have been done to determine the role of SAgs in diseases outside of TSS and food poisoning. The enterotoxin gene cluster (egc) is a group of 6 SAgs (selo, selm, sei, selu, seln, and seg) assembled into an operon-like cluster that is present in the majority of S. aureus strains isolated from IE patients. My studies have determined that the egc is able to induce vegetations when expressed in avirulent S. aureus strains. This is the first time the egc has been directly associated with IE. I further characterized the capacity of the individual egc proteins to induce vegetations. Four (selo, selm, sei, and selu) of the 6 egc SAgs were able to induce vegetation formation. This is the first time the individual egc proteins have been characterized and directly associated with IE. I also demonstrated that the egc proteins may not be exclusively expressed as a single polycistronic transcript but that selu and seg contain promoter elements that may drive their individual expression. Lastly, I provide evidence that the egc SAgs may be regulated by MgrA, a global regulator of S. aureus associated with virulence factor expression.

Diss. (sammanfattning) Umeå : Umeå universitet, 2006. / Härtill 4 uppsatser.

Thesis (Ph.D.)--University of Alabama at Birmingham, 2009. / Title from PDF title page (viewed on July 1, 2010). Includes bibliographical references.

Du fait de leurs propriétés immunostimulantes, les entérotoxines de Staphylococcus aureus (SEs) sont aussi considérées comme des outils thérapeutiques anticancéreux potentiels. Cependant, leurs implications dans de nombreuses pathologies humaines limitent leurs utilisations. Récemment, un opéron dénommé enterotoxin gene cluster (egc) codant pour cinq entérotoxines (SEG, SEI, SElM, SElN et SElO) supposées être de moindre virulence pour l’organisme, a été mis en évidence. En 2004, des patients atteints de carcinome broncho-pulmonaire ont été traités par l’administration d’un surnageant de culture d’une souche de S. aureus, contenant l’opéron egc. Ce traitement a permis d’allonger la durée de survie, et n’a eu aucun effet secondaire. Dans ce cadre, l’objectif de cette thèse a été d’étudier l’activité anti-tumorale des toxines de l’egc. Nos travaux ont mis en évidence l’activité tumoricide de ces toxines, induite par l’activation du système immunitaire. Cette toxicité est médiée par la sécrétion de nombreux médiateurs solubles comme le TNF-α et le NO. Nous avons confirmé le caractère pro-inflammatoire de type Th1 des toxines de l’egc. Nos travaux ont également montré qu’hormis SEI, les toxines de l’egc induisent des sécrétions de cytokines, chimiokines, protéases matricielles (MMPs) et facteurs de croissances nettement inférieures à celle induites par le reste des SEs. Ces résultats pourraient expliquer la faible toxicité associée aux toxines de l’egc. Enfin, nous avons montré que SElO possèdent une toxicité intrinsèque vis-à-vis des lignées tumorales. Cette étude plaide en faveur de l'intérêt des toxines de l’egc dans le développement de nouvelles approches en thérapie anti-tumorale / The use of classical superantigens (e.g. SEA, SEB and SEC) for treatment of cancer has resulted in a low response rates due to serious toxicity in humans. However, in a recent clinical study, remarkable results in treating lung cancer were obtained using superantigens encoded by the enterotoxin gene cluster (egc) without causing any significant toxicity. The current study was performed to investigate how egc superantigens (i.e. SEG, SEI, SElM, SElN and SElO) have tumoricidal activity with low toxicity. Indeed, we first demonstrated that tumoricidal activity of egc-SEs is mediated by immune cell activation, in particular, by secretion of soluble mediators such as nitric oxide and TNF-α. Thus, the proteomic analysis of the PBMC supernatants, showed that SEs-egc enhance the expression of pro-inflammatory cytokines, chimokines and many other biomarkers. Interestingly, levels were significantly higher in supernatants of SEA-stimulated PBMC than those with egc superantigens suggesting that staphylococcal superantigens differs in their inflammatory proprerties. Our results suggest that the relative lower pro-inflammatory activity of egc toxins may explain the low toxicity of these toxins observed during the clinical trial. Finally, we showed that SElO have a direct cytostatic activity against tumor cells. These findings suggest that egc-SEs seems to be good candidates for the development of new drugs in cancer therapy