In vitro activities of lytic peptides against the sporozoites of Cryptosporidium parvum.

Cryptosporidium parvum is a protozoan parasite that causes mild to severe diarrheal disease in animals and humans. There are currently no effective chemotherapeutic agents available for the treatment of cryptosporidiosis. Recent studies have described small, naturally occurring antimicrobial lytic peptides with antiprotozoal activities. In the present study, the anticryptosporidial activities of three synthetic lytic peptides were determined in an in vitro sporozoite susceptibility assay. Sporozoite viability was assessed microscopically by the uptake of the vital dyes fluorescein diacetate and propidium iodide. Sporozoite viability was reduced by 93.5% following a 60-min exposure to 10 microM Hecate-1 at 37 degrees C. Shiva-10 reduced sporozoite viability by approximately 74.0% after a 60-min exposure at 100 microM and 37 degrees C. The cecropin-b analog SB-37 reduced sporozoite viability by 6.0% following a 60-min exposure at 100 microM and 37 degrees C. A control peptide showed no anticryptosporidial activity.