Recently, Mahmoud Saleh successfully defended his PhD dissertation titled, “Innate and Adaptive Immune Responses Shape the Outcome of Clostridium difficile infection”. During his time in Bill Petri’s lab, Mahmoud studied the underlying mechanism of increased incidence and severity of C. difficile infection in inflammatory bowel disease (IBD) patients. The mouse model that he developed and the focus on the role of the immune response during infection led to the discovery of a novel role for Th17 cells in the pathogenesis of C. difficile, now published in Cell Host & Microbe.
Mahmoud showed that colitis-induced Th17 cells persist after recovery from colitis and that these cells are necessary and sufficient to exacerbate the severity of a subsequent C. difficile infection. Using clinical samples of almost 400 C. difficile patients, Mahmoud also showed that elevated levels of the Th17 cytokines IL-23 and IL-6 in the serum correlate with severe disease suggesting that this pathway is important during human infection. Given the important role for Th17 cells in the pathogenesis of IBD, Mahmoud’s work suggests that targeting these cells may not ameliorate IBD symptoms but also protect this highly susceptible population from severe disease. Congratulations, Mahmoud!