BioProject

The species Staphylococcus (S.) aureus harbors 19 superantigen gene loci, six of which are located in the enterotoxin gene cluster (egc). More...

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. 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. Less...