engleski

Autophagic vacuole as a niche for Francisella

Francisella tularensis is an intracellular bacterial pathogen that replicates in various cell types and has a complex intracellular life cycle. Early after infection, Francisella escapes the phagosome and reaches the cytosol, where the bacteria undergo extensive replication. Once in the cytosol, Francisella becomes the target of antibacterial autophagy. Many intracellular pathogens have evolved strategies to survive autophagy or to exploit this process for their replication. Here, we investigated the role of autophagy in the intracellular life cycle of Francisella during the early and late stages of infection in vitro. We determined the intracellular replication and cytotoxicity of Francisella tularensis subsp. holarctica LVS in primary murine macrophages after inhibition of autophagy with 3-methyladenine. To investigate the interaction of Francisella with the endocytic compartment of mouse macrophages, we examined the colocalization of intracellular bacteria with the lysosome marker (LAMP1) and the autophagy marker LC3B with confocal microscopy. The LVS strain replicated efficiently in primary murine macrophages. Intracellular replication and cytotoxicity of LVS were statistically reduced by 3-methyladenine, confirming that Francisella uses autophagy for its intracellular growth. Using fluorescence microscopy, we found that most bacteria were in the cytosol 6 hours after infection and did not colocalize with autophagy or lysosome markers. At 24 hours post-infection, most bacteria were in LAMP1- and LC3-positive vacuoles. Localization of the bacteria in LAMP1- and LC3-positive vacuoles was significantly inhibited by 3-methyladenine. Overall, our results demonstrated that the LVS strain forms vacuoles that exhibit autophagic features and require autophagy for its intracellular replication

autophagy ; Francisella ; in vitro ; LVS

nije evidentirano