Secreted proteins from Neisseria meningitidis mediate differential human gene expression and immune activation.

Meningococcal secreted proteins (MSPs) have been poorly characterized. We hypothesized that MSPs play essential roles in host--bacterial interactions and in the pathogenesis of disease. In order to test this, we examined differential host gene expression in human meningeal-derived cells, in response to endotoxin-depleted MSPs compared to live bacteria. Using expression arrays, upregulated expression of several pro-inflammatory and apoptosis-related genes was found to be induced by MSPs. The transcription and translation of representative genes was confirmed by using various methods. Increased interleukin 8 (IL-8) and cyclooxygenase 2 (COX-2) gene transcription was confirmed using real-time PCR. Upregulated IL-8, IL-6, ICAM-1 and COX-2 protein expression were confirmed by ELISA, flow cytometry or Western immunoblots. Furthermore, exposure of cells to MSPs or live meningococci induced a small significant resistance effect to staurosporine-induced apoptosis. Secreted meningococcal virulence factors are therefore important in inducing host inflammatory responses and resistance to apoptosis, and they are worthy of extensive investigation.