In vitro cultivation of Herpetosoma trypanosomes on embryonic fibroblasts and in semidefined cell-free medium.

Microtus agrestis embryo fibroblasts (MAEF) support the survival and multiplication at 37 C of the mammalian multiplicative forms of the Herpetosoma trypanosomes Trypanosoma microti, T. evotomys, T. musculi, and T. lewisi passaged from cultures on Schneider's Drosophila medium and of T. grosi from Grace's medium. MAEF layers with parasites were maintained for a period of over 5 mo. A semidefined cell-free medium also supported the multiplication (at 37 C) of the mammalian forms of the same trypanosome species, passaged directly from Schneider's Drosophila medium or Grace's medium, without their prior culture on cell lines. Reproductive stages were observed in cultures; T. microti and T. evotomys produced nests of dividing amastigotes from which trypomastigotes developed in the medium supernatant. Trypanosoma lewisi, T. musculi, and T. grosi divided initially as epimastigotes, which then transformed to bloodstream trypomastigotes. Multiplication of trypomastigotes was also observed. These methods of reproduction are the same as those reported in the respective mammalian hosts.