B. pertussis manipulates the macrophage phenotype while promoting its own intracellular survival

VALDEZ, HUGO; BALBOA, LUACIANA; GORGOJO, JUAN PABLO; SASIAIN, M. DEL CARMEN; RODRIGUEZ, MARÍA EUGENIA

Brussels

Simposio; 12th International Symposium on Bordetella; 2019

During microbial infection macrophage (MØ) response includes the polarization into classically or alternatively activated cells (M1 or M2, respectively). A proper MØ polarization is critical for bacterial clearance. The aim of this study was to examine the influence of MØ polarization in the development of Bp intracellular infections. To this end, primary human monocytes were differentiated into MØ in the presence of GM-CSF+INF-gamma/LPS, M-CSF+IL-4, or M-CSF+IL10, to obtain M1, M2a or M2c phenotypes, respectively. Bacterial phagocytosis was assessed by two-colors fluorescence microscopy. Intracellular trafficking and survival were determined at 3 and 48 h postinfection by confocal microscopy and Polymyxin B protection assays, respectively. MØ surface markers were evaluated by flow cytometry and the inflammatory response by cytokine determination by qPCR and ELISA. M1 macrophages showed a lower phagocytosis activity but a higher bactericidal activity as compared with M2a or M2c. Three hours after phagocytosis M1 showed a strong proinflammatory response evidenced by the production of high levels of TNF-α. Forty-eight hours after infection, however, an increase of CD206, CD163, and CD209 were detected on the surface of infected M1 suggesting a bacterial manipulation of the phenotype. Conversely, Bp infection of M2a and M2c did not induce TNF-α at any time post-infection while both phenotypes showed a significant increase in surface CD206, CD163 and CD209 as the infection progressed. This increase was higher in M2c than in M2a. Interestingly, high levels of anti-inflammatory cytokines, namely, IL-10 and TGF were found induced in all three MØ phenotypes at late times post-infection. Our results showed that B. pertussis intracellular survival was significantly higher in M2 than M1, being M2c the best candidate to develop into a niche of persistence. The results, however, also demonstrated that B. pertussis seems able to manipulate all three MØ phenotypes and survive inside any of them.