Intracellular B. pertussis modulates human macrophage defense gene expression

VALDEZ, HUGO; OVIEDO, JUAN MARCOS; RODRIGUEZ, MARIA EUGENIA

Buenos Aires

Simposio; 11th International Bordetella Symposium; 2016

International Bordetella Society

Objective Our group recently showed that the encounter of Bordetella pertussis (Bp) with human macrophages in the absence of opsonic antibodies leads to the intracellular survival of a significant number of bacteria that, after a lag period, are able to replicate inside to macrophage. In this study we investigated the human macrophage defense response along the establishment of Bp intracellular infection.Material and MethodsUsing real-time PCR we examined the transcription level of key host defense genes of human monocytic cell line (THP-1) differentiated into macrophages during the Bp infection at 3, 24 and 48 h. The most relevant changes were confirmed at protein level.ResultsThe results showed that early transcriptional response to this pathogen was dominated by an up-regulation of host defense genes characteristics of macrophage activation like LYZ (lysozyme), CTSA (cathepsin), CTSC, CTSB, CTSD, CTSG, CTSS, CAT (catalase), IL-10, IL-8, TNF-α and SOCS3 (suppressor of cytokine signaling). At later time points both the bactericidal and the inflammatory response were progressively down-regulated and 48 hours after infection SOCS1 expression level was significantly up-regulated while TNF-α and SOCS3 were strongly down modulated. Infections assays ran in parallel with Bp mutants deficient in the production of Ptx and CyaA showed that Ptx is involved in the regulation of the expression of most of the genes implicated in the microbicidal activity that were down-modulated in infected cells, while the down-regulation of some others, as those involved in the inflammatory response, depends on the expression of either CyaA or Ptx. In agreement with these results both toxin defective mutants showed a significantly lower intracellular survival 48 hours after infection as compared with the wild type strain.ConclusionThe results obtained here suggest that during the intracellular infection Bp manipulates the intracellular macrophage environment; leading to M2 phenotype, permissive for intracellular survival.