Sexual Development of Cryptosporidium

Project Abstract The protozoan parasite Cryptosporidium is one of the most important causes of severe diarrheal disease. In the U.S. this parasite is responsible for half of all waterborne disease outbreaks, some of which have occurred at massive scale. Patients suffering from immunosuppression due to HIV/AIDS, organ transplantation, or cancer are in gravest danger. The global public health impact is even larger: after Rotavirus, Cryptosporidium is the most important diarrheal pathogen in small children. In particular in the context of malnutrition, cryptosporidiosis has a highly significant imprint on childhood mortality. Cryptosporidiosis is also linked to stunting, thus leaving a lasting shadow on the future of children. This parasite has a single host life cycle, asexual and sexual processes occur sequentially in the intestinal epithelium of the same host. Completion of this developmental program is required for continued infection, severe disease, and transmission. We have built robust experimental systems to observe and manipulate the sexual development of Cryptosporidium and we unraveled key elements of the mechanisms that control the underlying gene expression systems. In this application we will define the epigenetic mechanisms that govern transition from asexual to sexual replication, we will unravel how the parasites choses between a male or female fate, and we will use emerging cyro-electron tomography and parasite genetics to understand how the unique ultrastructure of male gametes enables fertilization. The resulting findings will impact on our fundamental understanding of parasite development and on translational efforts to develop drugs and vaccines.