The infectivity of cultural forms of a Peru strain of Trypanosoma cruzi for CFI mice and reduviid bugs

Growth and differentiation of Trypanosoma cruzi cultivated with a Triatoma infestans embryo cell line

Trypanosoma cruzi strain Peru was cultivated in the presence of an established cell line of Triatoma infestans embryo cells (TI- 32). Bloodstream trypomastigotes differentiated into amastigote-like cells (first differentiation phase) which multiplied to form large clusters of cells. Because of their clustering nature, a new term, "staphylomastigotes," has been proposed for this stage. After 10 days of cultivation, 90% of the staphylomastigotes underwent differentiation (2nd differentiation phase) to trypomastigotes (approximately 98%) or epimastigotes (approximately 2%). Bloodstream trypomastigotes cultivated without TI-32 cells underwent the first, but not the 2nd differentiation phase, although occasional epimastogotes were seen (less than 1%). The evidence presented suggests that TI-32 cells produce a labile factor(s) important not only for initiation of the 2nd differentiation phase but also for maintaining the parasites in the trypomastigote stage. The pH of the culture medium was not the initiating factor for the 2nd differentiation phase. Infectivity studies indicated that staphylomastigotes were as infective as blood stream trypomastigotes, but that metacyclic trypomastigotes isolated from culture after the 2nd differentiation phase were slightly more infective than bloodstream forms. Electromicrographs of styphylomastigotes do not provide any evidence of exchange of genetic material between cells.

The infectivity of single flagellates of Trypanosoma cruzi

Single organisms of Trypanosoma cruzi of the virulent Peru strain were isolated by direct visualisation and were injected peritoneally into CFI mice. Single trypanomastigotes of different morphology and from different sources (mouse blood, in vitro cufture and bug faeces) were used. Single trypanomastigotes from mouse blood caused parasitaemia and fataiity in a high percentage of mice. This was true irrespective of the morphology (broad or narrow form) of the trypano mastigo tec. Single organisms of the culture forms were also capable of causing infection, although these were less infectious than single trypanomastigotes obtained from mouse blood or the reduviid bug. The difficulties attendant on the performance of the cloning technique are discussed and some indication is given of how these problems can be overcome.