Sci Rep. 2016 Nov 9;6:36813. doi: 10.1038/srep36813.

Streptococcus pneumoniae resists intracellular killing by olfactory ensheathing cells but not by microglia.

Macedo-Ramos H1,2,3, Ruiz-Mendoza S1,2, Mariante RM4,5, Guimarães EV5, Quadros-de-Souza LC1, Paiva MM6, Ferreira EO7, Pinto TC8, Teixeira LM8, Allodi S2,3, Baetas-da-Cruz W1,2.

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Olfactory ensheathing cells (OECs) are a type of specialized glial cell currently considered as having a double function in the nervous system: one regenerative, and another immune. Streptococcus pneumoniae is a major agent of severe infections in humans, including meningitis. It is commonly found in the nasopharynx of asymptomatic carriers, and, under certain still unknown conditions, can invade the brain. We evaluated whether pneumococcal cells recovered from lysed OECs and microglia are able to survive by manipulating the host cell activation. An intracellular-survival assay of S. pneumoniae in OECs showed a significant number of bacterial CFU recovered after 3 h of infection. In contrast, microglia assays resulted in a reduced number of CFU. Electron-microscopy analysis revealed a large number of pneumococci with apparently intact morphology. However, microglia cells showed endocytic vesicles containing only bacterial cell debris. Infection of OEC cultures resulted in continuous NF-κB activation. The IFN-γ-induced increase of iNOS expression was reversed in infected OECs. OECs are susceptible to S. pneumoniae infection, which can suppress their cytotoxic mechanisms in order to survive. We suggest that, in contrast to microglia, OECs might serve as safe targets for pneumococci, providing a more stable environment for evasion of the immune system.

PMID: 27827453 PMCID: PMC5101813 DOI: 10.1038/srep36813

[PubMed - in process]