Growth of Trachipleistophora hominis (Microsporidia: Pleistophoridae) in C2,C12 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 muscle cells, inhibited myotube formation from myoblasts when grown in a mouse myoblast cell line C2,C12. Uninfected cultures readily converted to myotubes. Albendazole, a drug with known antimicrosporidial activity, was tested against T. hominis in C2,C12 cells. The drug was added when infection had reached 75% of C2,C12 cells, a level comparable to that obtained in heavily infected muscle in vivo. Doses of 1 ng/ml and 10 ng/ml had no effect on merogony or sporogony. In cultures exposed to 100 ng/ml albendazole, the C2,C12 cells remained in good condition while infection levels dropped to 25% over 7 weeks. Drug doses of 500 ng/ml and 1,000 ng/ml were deleterious 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 surface coat and its reticulate extensions. Meronts were not seen in cultures 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 polaroplast. The in vitro susceptibility of T. hominis to albendazole was low in comparison with in vitro susceptibility of other microsporidia of human origin.