Bordetella parapertussis survives the innate interaction with immune cells and replicates inside macrophages in a O-Antigen dependent manner.

GORGOJO, JUAN; HARVILL, ERIC; RODRÍGUEZ MARIA EUGENIA

Dublin

Simposio; 10th International Symposium on Bordetella; 2013

Bordetella International Society

Antibodies induced by pertussis acellular vaccines do not opsonize B. parapertussis due to the presence of the O Antigen. Neutrophil uptake of B. parapertussis in the absence of opsonic antibodies leads to the failure of lysosomal maturation and bacterial killing in a lipid rafts-dependent manner. The O Antigen is involved in this non-bactericidal interaction by directing the bacteria to the lipid rafts of the host cell. We here evaluated the outcome of the innate interaction of this pathogen with human macrophages, a common reservoir of many persistent pathogens. Using confocal microscopy and fluorescent probes we investigated the fate of B. parapertussis upon phagocytosis. Intracellular bacterial survival was evaluated by Polymyxin B protection assays. Our results show that a small fraction of bacteria survived upon phagocytosis and were found in non-acidic/LAMP negative compartments 24 hours post-infection. After another 24 hours a significant increase in the intracellular number of viable bacteria was detected together with a significant decrease in the proportion of intracellular bacteria colocalizing with lysosomal markers. At this time of infection most of the bacteria were found in compartments with characteristic of replicative phagosomes. Again, the O Antigen was found involved in this non-bactericidal trafficking. A mutant defective in O Antigen expression showed a significant decrease in intracellular viability and was mainly found in lysosomal compartments 48 hours after infection. These results indicate that Bordetella parapertussis, interferes with the bactericidal activity of both PMN and macrophages affecting its traffic to lysosomes in a O Antigen-dependent manner