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Expression data from human PBMCs treated for 6h with the staphylococcal superantigens SEB and SEI

ABSTRACT: The species Staphylococcus (S.) aureus harbors 19 superantigen gene loci, six of which are located in the enterotoxin gene cluster (egc). While these egc superantigens are far more prevalent in clinical S. aureus isolates than non-egc superantigens, they are not a prominent cause of toxic shock. Moreover, neutralizing antibodies against egc superantigens are very rare, even among carriers of egc-positive S. aureus strains. In search of an explanation we have tested two non-exclusive hypotheses: 1) egc and non-egc superantigens have unique intrinsic properties and drive the immune system into different directions; 2) egc and non-egc-superantigens are released by S. aureus under different conditions, which shape the immune response. A comparison of three egc (SEI, SElM and SElO) and three non-egc superantigens (SEB, SElQ, TSST-1) revealed that both induced proliferation of human PBMC with comparable potency and elicited similar Th1/Th2-cytokine signatures. This was supported by gene expression analysis of PBMC stimulated with one representative superantigen from each group (SEI and SEB). They induced very similar transcriptional changes, especially of inflammation-associated gene networks, corresponding to a very strong Th1- and Th17-dominated immune response. In contrast, the regulation of superantigen release differed markedly between both superantigen groups. Egc-encoded proteins were secreted by S. aureus during exponential growth, while non-egc superantigens were released in the stationary phase. We conclude that the distinct biological behavior of egc and non-egc superantigens is not due to their intrinsic properties, which are very similar, but caused by their differential release by S. aureus.

ORGANISM(S): Homo sapiens

PROVIDER: GSE11281 | GEO | 2008/10/01

SECONDARY ACCESSION(S): PRJNA106687

REPOSITORIES: GEO

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Project description:The species Staphylococcus (S.) aureus harbors 19 superantigen gene loci, six of which are located in the enterotoxin gene cluster (egc). While these egc superantigens are far more prevalent in clinical S. aureus isolates than non-egc superantigens, they are not a prominent cause of toxic shock. Moreover, neutralizing antibodies against egc superantigens are very rare, even among carriers of egc-positive S. aureus strains. In search of an explanation we have tested two non-exclusive hypotheses: 1) egc and non-egc superantigens have unique intrinsic properties and drive the immune system into different directions; 2) egc and non-egc-superantigens are released by S. aureus under different conditions, which shape the immune response. A comparison of three egc (SEI, SElM and SElO) and three non-egc superantigens (SEB, SElQ, TSST-1) revealed that both induced proliferation of human PBMC with comparable potency and elicited similar Th1/Th2-cytokine signatures. This was supported by gene expression analysis of PBMC stimulated with one representative superantigen from each group (SEI and SEB). They induced very similar transcriptional changes, especially of inflammation-associated gene networks, corresponding to a very strong Th1- and Th17-dominated immune response. In contrast, the regulation of superantigen release differed markedly between both superantigen groups. Egc-encoded proteins were secreted by S. aureus during exponential growth, while non-egc superantigens were released in the stationary phase. We conclude that the distinct biological behavior of egc and non-egc superantigens is not due to their intrinsic properties, which are very similar, but caused by their differential release by S. aureus. Experiment Overall Design: PBMCs from 3 healthy blood donors were purified and treated with Medium (control) and recombinant staphylococcal superantigens SEB and SEI. After 6 hours of treatment, total RNA was extracted and hybridized to Affymetrix GeneChip Arrays.

Project description:Staphylococcus Enterotoxin B (SEB) is an exotoxin produced by Staphylococcus aureus. It is a public health threat during nosocomial infections. It is also considered as a biological weapon. The Centers for Disease Control and Prevention (CDC) lists SEB as a category B agent of Biodefence. SEB is easily aerosolized and can enter the host through inhalation which could lead to Acute Lung Injury (ALI) and in severe cases, it may result in multiple organ failure, shock and death. It is considered to be a Super-antigen as it activates a large number (30%) of T cells and results in the production of cytokines SEB binds directly to the non polymorphic region of MHC Class II which is expressed on antigen presenting cells and this complex activates T cells expressing a specific variable region of the β chain (Vβ8) of the T cell receptor (TCR). Thus, inhalation of SEB leads to recruitment of immune cells into the lung and secretion of pro-inflammatory cytokines which results in severe damage to the lung by increasing the permeability, and induction of respiratory failure. MicroRNA (miRNAs) is considered one of the mechanisms by which the epigenetic regulation happens. MicroRNA are noncoding small RNAs that have recently been shown to play a role in gene expression. The action of miRNA is dependent on its binding to 3’ Untranslated Region (3’UTR) of mRNA resulting in transcriptional or translational repression. Specifically, the efficacy of gene silencing is determined by the interaction of miRNA seed sequence with the target mRNA. Endocannabinoids are lipid molecules produced endogenously by host cells and bind to cannabinoid receptors, CB1 and CB2. N-Arachidonoylethanolamide or anandamide (AEA) is an endocannabinoid that has been shown to have immunomodulatory effects by our lab and others, although the precise mechanism is not clear. So far through my research, I found that Endocannabinoid is involved in a very unique way in the anti-inflammatory response through upregulation of many anti-inflammatory genes such as FOXP3, ARG1, and IL-10 that targeted by miRNA23a-3p and miRNA 34a-5p as well as the anti-inflammatory phenotype population as it show in the RT-PCR and flow cytometry results.

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Expression data from human PBMCs treated for 6h with the staphylococcal superantigens SEB and SEI

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