Project description:Background: Biological interpretation of gene expression data may differ depending on underlying assumptions and statistical tests used by the chosen bioinformatic tool. We used Gene Set Enrichment Analysis (GSEA) and Ingenuity Pathway Analysis (IPA) to analyze previously generated gene expression profiles induced in human monocytes by N. meningitidis and IL-10 (“the model system”), and by meningococcal sepsis plasma before and after immunodepletion of IL-10 (“the patient plasma system”). The objectives were to compare whether these two methods resulted in similar biological interpretation of the datasets; and identify whether GSEA provided additional insight about the human monocyte host response to meningococcal activation. Results: In both experimental models, GSEA and IPA associated genes induced in monocytes by N. meningitidis with pro-inflammatory innate immune activation, including TNF-signaling, Toll-like receptor signaling, JAK-STAT-signaling, type I and type II interferon. GSEA associated genes regulated by the presence of IL-10 with similar gene sets in both the model system and the patient plasma system. In the model system, GSEA and IPA identified 170 genes associated with oxidative phosphorylation/mitochondrial function to be down-regulated in monocytes stimulated with meningococci. In the patient plasma system, GSEA and IPA combined identified 122 genes associated with oxidative phosphorylation/mitochondrial dysfunction to be down-regulated by meningococcal sepsis plasma depleted for IL-10. Combining analyses from GSEA and IPA identified that some genes associated with oxidative phosphorylation/mitochondrial function that were inhibited by N. meningitidis were partially up-regulated by IL-10. Conclusions: Biological processes associated with the gene expression changes in the model system of meningococcal sepsis was comparable to the results found in the patient plasma system. By combining GSEA with IPA, we have discovered an inhibitory effect exerted by N. meningitidis on genes associated with oxidative phosphorylation, and that IL-10 possibly partially dampen this strong inhibitory effect, thereby identifying, to our knowledge, yet another area where IL-10 regulates the effect of LPS. We suggest that relying on a single bioinformatic tool together with arbitrarily chosen filtering criteria for data analysis may result in overlooking relevant biological processes and signaling pathways associated with genes differentially expressed between compared experimental conditions.

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Proteomic profiling of human monocytes stimulated in vitro with N. meningitidis

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