Intralysosomal pathogens differentially influence the proteolytic potential of their niche

Area of Science:

• Microbiology
• Cell Biology
• Pathogen-Host Interactions

Background:

• Intracellular pathogens must evade host cell degradation for survival.
• Coxiella burnetii and Leishmania species are unique pathogens that replicate within host cell phagolysosomes.
• C. burnetii was previously shown to remove cathepsin B, a lysosomal protease, during infection.

Purpose of the Study:

• To investigate if Leishmania mexicana employs a similar strategy to C. burnetii by manipulating host cell lysosomes.
• To compare the survival mechanisms of L. mexicana and C. burnetii within the phagolysosomal compartment.

Main Methods:

• Immunoblotting and protease activity-based probes were used to assess cathepsin activity in L. mexicana-infected cells.
• Mass spectrometry was employed to analyze the host cell proteome and secretome.
• Co-infection experiments were conducted using THP-1 macrophage-like cells.

Main Results:

• L. mexicana infection did not lead to decreased cathepsin activity, unlike C. burnetii.
• Co-infection showed that L. mexicana does not influence C. burnetii-induced lysosomal remodeling.
• Mass spectrometry confirmed L. mexicana does not increase lysosomal protein abundance intracellularly or extracellularly.

Conclusions:

• C. burnetii and L. mexicana utilize distinct mechanisms to survive within the hostile phagolysosomal environment.
• L. mexicana does not employ lysosomal protease removal as a virulence strategy.
• Pathogen survival strategies within the same intracellular niche can be divergent.