In vitro effect on Cryptosporidium parvum of short-term exposure to cathelicidin peptides

Two laboratory methods, a cell culture system and double fluorogenic staining, were used to study the viability and infective ability of Cryptosporidium parvum sporozoites and oocysts after short-term exposure to four cathelicidin peptides. The compounds, SMAP-29, BMAP-28, PG-1 and Bac7(1-35), exerted a strong cytotoxic effect on sporozoites, but did not affect the viability and function of oocysts consistently. Overall, in the sporozoite series, a percentage of the viable population decreased rapidly to less than detectable levels after 15 and 60 min exposure to the peptides at concentrations of 100 and 10 mug/mL, respectively. In the oocyst series, no compound produced complete inhibition of parasite growth: 60-85% of the oocyst population was viable after 180 min exposure at 100 mug/mL. SMAP-29 exerted the highest activity against both sporozoites and oocysts.