Coxiella survival mechanisms in the intracellular niche

PROJECT SUMMARY/ABSTRACT Coxiella burnetii is the causative agent of human Q fever, a zoonotic disease that can cause a debilitating, flu- like illness in acute cases, or a life-threatening endocarditis in chronically infected patients. Q fever patients present with few distinguishing clinical features, and chronic disease requires a minimum of 18 months of antibiotic treatment, highlighting the need for new therapeutics. An obligate intracellular pathogen, Coxiella survives inside a vacuole within infected cells that has characteristics of a functional phagolysosome, including active proteases and phosphatases and moderately acidic pH, a physicochemical parameter to which C. burnetii is exquisitely adapted. C. burnetii is a strict moderate acidophile capable of efficient nutrient transport, catabolism and replication only within a narrow pH range under both host cell-free and intracellular conditions. The objective of this application is to identify host and pathogen factors that function to maintain both CCV and bacterial cytoplasmic pH. Aim 1 will test the hypothesis that C. burnetii controls bacterial cytoplasmic pH via carbonic anhydrase-dependent metabolism of CO2 and also how the metabolically dormant Small Cell Variant of C. burnetii protects the pathogen against acid stress. Aim 2 will test the hypothesis that C. burnetii regulates CCV pH by manipulating host lysosomal biogenesis. Understanding the molecular mechanisms behind C. burnetii survival within the acidic CCV will allow identification of potential therapeutic targets.