The growth of Trypanosoma cruzi in human diploid cells for the production of trypomastigotes.

The use of human diploid cell lines of finite life for the in vitro production of Trypanosoma cruzi is described. Both MRC5 and WI38 cells release trypomastigotes with less than 5% amastigotes. This could form the basis for biochemical and immunological studies, which were previously limited by the problems of separating parasites from blood. By selecting the in vitro passage number of the parasite it is possible to select for either the broad or the slender forms of trypomastigotes, allowing comparative studies of these forms within a single strain of the parasite. It is also possible to isolate amastigotes by disrupting the cells before trypomastigotes appear, and separating them from cell debris with Metrizamide. It is shown that by incorporating [3H]uridine in the cell-culture medium, labelled trypomastigotes are obtained. The release of this label (putative RNA) provides a relatively simple isotopic assay for parasite death. Examples of this assay for testing drug toxicity and in immunological lysis are presented.