Modulation of S. epidermidis-induced innate immune responses in neonatal whole blood.

BACKGROUND: Coagulase-negative staphylococci (CoNS) such as Staphylococcus epidermidis are highly prevalent pathogens for sepsis in neonates. The interaction between host, environment and pathogenic factors of S. epidermidis are still poorly understood. Our objective was to address the role of several pathogenic factors of S. epidermidis on neonatal cytokine responses and to characterize the influence of three immunomodulatory drugs. METHODS: We performed an ex-vivo model of S. epidermidis sepsis by assessment of blood cytokine production in neonatal whole blood stimulation assays (ELISA). S. epidermidis strains with different characteristics were added as full pathogen to umbilical cord blood cultures and the influence of indomethacin, ibuprofen and furosemide on neonatal immune response to S. epidermidis was evaluated (Flow cytometry). RESULTS: Stimulation with S. epidermidis sepsis strains induced higher IL-6 and IL-10 expression than stimulation with colonization strains. Biofilm formation in clinical isolates was associated with increased IL-10 but not IL-6 levels. In contrast, stimulation with mutant strains for biofilm formation and extracellular virulence factors had no major effect on cytokine expression. Notably, addition of ibuprofen or indomethacin to S. epidermidis inoculated whole blood resulted in mildly increased expression of TNF-α but not IL-6, while frusemide decreased the production of pro-inflammatory cytokines, i.e. IL-6 and IL-8. CONCLUSIONS: The virulence of sepsis strains is coherent with increased cytokine production in our whole-blood in-vitro sepsis model. Biofilm formation and expression of extracellular virulence factors had no major influence on readouts in our setting. It is important to acknowledge that several drugs used in neonatal care have immunomodulatory potential.

Immunomodulatory effects of Sanglifehrin A in the innate and acquired immune response of neonatal whole blood cells.

Previous investigations have shown the immunosuppressive activity of the immunophilin-binding macrolide Sanglifehrin A (SFA). In adults, SFA also exerts anti-inflammatory properties in lipopolysaccharide (LPS)-stimulated whole blood cultures. It was the aim of this study to investigate whether the unique properties of SFA are also present in the neonatal immune system, as neonates are susceptible to serious infection due to an immaturity of immune responses. We used a whole blood assay to investigate the impact of SFA on T-cell proliferation and secretion of T-cell cytokines upon Anti-CD3/Anti-CD28 costimulation. In addition, interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-alpha) secretion was assessed in whole blood monocytes after LPS stimulation. Furthermore, the influence of SFA on LPS-induced signal transduction pathways, specifically the activity of p42/44, p38 and Ap-1, was assessed in neonatal PBMCs. Neonatal cord blood lymphocytes were found to have a diminished IL-4, IL-6, TNF-alpha and interferon-gamma (IFN-gamma) production upon Anti-CD3/Anti-CD28 costimulation compared to adult whole blood lymphocytes. In contrast, no significant differences were noted for either IL-2 production or proliferation of CD4+ cells. Upon addition of 1000nM SFA to neonatal whole blood cultures, a significant inhibition of both, T-cell cytokine secretion and proliferation was demonstrated. In line with data from adult whole blood cultures, SFA proved to be a strong inhibitor of LPS-induced expression of IL-6 and TNF-alpha in the neonatal whole blood system. In signal transduction studies of the LPS pathway, a potent inhibition of the protein kinase p42/44 was demonstrated. SFA was also shown to block nuclear translocation of the transcription factor Ap-1. SFA was proved to have inhibitory effects on innate and acquired immune response of neonatal whole blood cells. The protein kinase p42/44 and the transcription factor Ap-1 were demonstrated to be potential key molecules for the anti-inflammatory effect of SFA.