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Comparison of Transcriptional Signatures of Three Staphylococcal Superantigenic Toxins in Human Epidermal Melanocytes

ABSTRACT: Staphylococcus aureus, a gram-positive bacterium, causes food poisoning and toxic shock syndrome through the production of superantigenic toxins known as Staphylococcal enterotoxins serotypes A-J (SEA, SEB, etc.) and toxic shock syndrome toxin-1 (TSST-1). A subset of these toxins have been classified as potential biothreat agents. The chronology of molecular events that could potentially characterize superantigenic toxicity and early pathogenesis is not well understood. The focus of this study was to determine the distinct and shared mechanisms of response to three toxins of the superantigenic family, namely SEA, SEB and TSST-1. Since skin functions as the front line of the host’s defense mechanism, melanocytes were selected for the study and treated with 25 µg/mL of one of these three toxins. Cells were collected after treatment for six different time periods, ranging from 0.5 h to 48 h. Total RNA was investigated using gene expression microarrays containing approximately 50,000 probes, and a subset of the results were validated using NanoString assays. Transcriptomic expression data indicated that each of these three toxins had a unique longitudinal trajectory. In particular, the gene expression profiles of SEB post-exposure was very distinct from those for SEA and TSST-1 superantigens. All three superantigens showed enriched biological networks related to necrosis, skin disorders, and inflammation. The three superantigens share some similarities in acting on the mechanisms underlying apoptosis, innate immunity, and other biological processes. Pathways related to innate immunity, such as the patterns of cytokine production and acute-phase response, showed toxin-specific regulation. The differentially regulated networks can be logical targets for early therapeutic intervention and can potentially serve as early diagnostic markers for superantigen-induced toxicity.

ORGANISM(S): Homo sapiens

PROVIDER: GSE124756 | GEO | 2022/06/30

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.

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Comparison of Transcriptional Signatures of Three Staphylococcal Superantigenic Toxins in Human Epidermal Melanocytes

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