Molecular and Biochemical Characterization of the Cryptosporidium Glycoprotein Ligand CSL

Cryptosporidiosis, caused by the ubiquitous parasite Cryptosporidium parvum, is a major cause of diarrhea in calves and other agriculturally important food animals throughout the world. The disease also affects humans that are exposed to parasite-contaminated food or water. Treatment and prevention of cryptosporidiosis remain problematic due to the absence of vaccines, and lack of effective parasite-specific drugs. Because cryptosporidiosis is resolved by specific host immune responses, immunologic control strategies have been investigated. To this end, our long term goals have been to identify molecular targets on the parasite which are recognized by protective immune responses, and to determine their role in the infection process. Limited knowledge on the mechanism of parasite attachment to host intestinal cells has hindered development of vaccines and drug discovery for cryptosporidiosis. Our recent efforts have culminated in the identification of a novel C. parvum glycoprotein, designated CSL, which is used as a parasite attachment ligand for intestinal cells. Because CSL is required for attachment to host cells, it is an opportune target for immunologic or pharmacologic intervention against cryptosporidiosis. We hypothesize that parasite attachment to host cells is mediated by functional peptide and carbohydrate domains contained in CSL. The following objectives will test this hypothesis: Objective 1. Identify the glycoprotein domains in native CSL which contain specific attachment molecules for host intestinal cells.Objective 2. Determine if specific attachment of CSL-derived glycopeptides identified in objective 1 is mediated by carbohydrates, or peptides, or both. Objective 3. Determine the complete molecular structure of the CSL glycopeptide-derived components identified in objective 2 which mediate specific attachment required for infection.