Effects of purine nucleosides on the in vitro growth of Cryptosporidium parvum

The effect of purine nucleosides on the in vitro growth of Cryptosporidium parvum was studied. Culturing the parasite in THP-1 cells for 72 h in growth medium supplemented with adenosine or inosine improved the parasite yields especially in the first 48 h. Similar results were obtained with parasites cultured in Madin–Darby bovine kidney cells and incubated for 24 h with inosine. The addition of inosine to 72-h cultures enhanced the growth of C. parvum in THP-1 cells, especially the trophic stages, whereas the analogue formycin B was toxic to the parasites and induced a marked decrease in the gamont stages. The monitoring of the added purine nucleosides by high performance liquid chromatography showed that at 37°C in the presence of THP-1 cells, a rapid uptake of inosine occurred with hypoxanthine being the main purine present after 2 h in the medium.