Growth of Trachipleistophora hominis (Microsporidia : Pleistophoridae) in C-2,C-12 mouse myoblast cells and response to treatment with albendazole

The microsporidium Trachipleistophora hominis Hollister, Canning, Weidner, Field, Kench et Marriott, 1996, originally isolated from human skeletal mus cle cells, inhibited myotube formation from myoblasts when grown in a mouse myoblast cell line C-2,C-12. Uninfected cultures readily converted to myot ubes. Albendazole, a drug with known antimicro-sporidial activity, was test ed against T. hominis in C-2,C-12 cells. The drug was added when infection had reached 75% Of C-2,C-12 cells, a level comparable to that obtained in h eavily infected muscle in vivo. Doses of 100 ng/ml and 10 ng/ml had no effe ct on merogony or sporogony. In cultures exposed to 100 ng/ml albendazole, the C-2,C-12 Cells remained in good condition while infection levels droppe d to 25% over 7 weeks. Drug doses of 500 ng/ml and 1,000 ng/ml were deleter ious to the host cells but some spores retained viability and were able to establish new infections once albendazole pressure was removed. T. hominis meronts exposed to 100 ng/ml albendazole mostly lacked the normally thick s urface coat and its reticulate extensions. Meronts were not seen in culture s exposed to higher drug doses. Albendazole at a concentration of 100 ng/ml and higher had a profound effect on spore morphogenesis. There was erratic coiling of the polar tube, often involving the formation of double tubes, and chaotic disposition of membranes which could have been those of polarop last. The in vitro susceptibility of T. hominis to albendazole was low in c omparison with in vitro susceptibility of other microsporidia of human orig in.