ROLE OF HUMAN LUNG FIBROBLASTS IN THE Brucella abortus INFECTION BY INHALATION

PAIVA ALONSO IVAN; FLORENCIA MUÑOZ GONZALEZ; FOCARACCIO JULIETA; FERRERO MARIANA CRISTINA; BALDI, PABLO CÉSAR

Buenos Aires

Congreso; LXV REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE INMUNOLOGÍA; 2017

Sociedad Argentina de Inmunología

Inhalation of contaminated aerosols is one of the most common forms for human infection by Brucella abortus. Together with epithelial and endothelial cells, fibroblasts are an important component of the alveolar respiratory barrier. While the interaction of Brucella with human lung epithelial cells has been studied, its interaction with human lung fibroblasts remains unknown. In this work, we investigated the ability of B. abortus 2308 to infect and induce inflammatory mediators in a cell line of normal human lung fibroblasts (MRC-5). The cells were infected for 2 h and then incubated with gentamicin to kill extracellular bacteria (time 0 p.i.). At 2, 24 and 48 h p.i., cells were lysed to determine CFU of intracellular bacteria, and culture supernatants were collected at 48 h p.i. to measure cytokines. Results showed that B. abortus infects and replicates in lung fibroblasts and that its survival depends on a functional virB operon. The infection induced the secretion of interleukin-8 (IL-8) (p˂0.0001), which secretion was mediated by p38 MAPK and NF-κB pathways, and monocyte chemotactic protein 1 (MCP-1) (p˂0.0001), which secretion depended on p38 MAPK, NF-κB and PI3K pathways. Furthemore, the infection increases the secretion of gelatinase and collagenase (p˂0.0001). The cytokine secretion did not depend on bacterial viability since heat-killed B. abortus and B. abortus lipopolysaccharide were also able to induce IL-6, IL-8 and MCP-1 secretion. In addition, the secretion of IL-6 and MCP-1 by fibroblasts increased significantly upon stimulation with conditioned medium (CM) from B. abortus-infected macrophages as compared to stimulation with CM from non-infected cells. These results suggest that human lung fibroblasts respond to B. abortus infection producing chemokines either directly or by stimulation with soluble factors secreted by infected macrophages.