CHRONIC GRANULOMATOUS DISEASE: STUDIES ON THE MOLECULAR MECHANISMS INVOLVED IN MICROBICIDAL DEFECT AND DESIGN OF NEW APPROACHES FOR THE TREAMENT OF THE DISEASE

Chronic granulomatous disease (CGD) is a genetic syndrome characterized by recurrent, often fatal infections due to the absence of NADPH oxidase, an enzyme complex generating the reactive oxygen species responsible for the oxygen-dependent microbicidal systems of phagocytes (neutrophils, monocytes, macrophages). An increased proinflammatory activity of neutrophils (PMN) also contributes to the pathophysiology of the disease. It has been recently proposed that additional factors might be responsible for the microbicidal defect of CGD PMN. In fact, it has been hypothesized that absence of NADPH oxidase, by altering the pH and K+ concentrations of the phagosome, would prevent activation of bactericidal proteins forming the so called oxygen-independent antimicrobial systems. The aims of this project are: 1. to re-examine the nature of the microbicidal defect of CGD PMN by evaluating the relative role of the oxygen-dependent microbicidal systems and of the variations of phagosomal pH and K+ concentrations thought to be involved in activation of the oxygen-independent antimicrobial systems. 2. to verify whether lysosomotropic drugs of potential clinical use, capable of correcting the abnormal phagosomal pH of CGD PMN, improve the microbicidal activity of these cells. Preliminary observations indicate that bacterial growth within CGD PMN is higher than in the absence of PMN. This may favour microbial expansion, prolong the inflammatory response and protect microorganisms from antibiotic therapy. Therefore, we will examine whether inhibition of phagocytosis will reduce microbial growth or even favour killing via the recently described neutrophil extracellular traps (NETs) and increase microbial susceptibility to antibiotics. Finally, it will be established whether lysosomotropic drugs and inhibitors of phagocytosis increase resistance to infection of animal models of CGD.