Growth and Differentiation of Trypanosoma cruzi Cultivated with a Triatoma infestans Embryo Cell Line*

Abstract

T. cruzi strain Peru was cultivated in the presence of an established cell line of T. infestans embryo cells (TI-32). Bloodstream trypomastigotes differentiated into amastigote-like cells (1st differentiation phase) which multiplied to form large clusters of cells. Because of their clustering nature, a new term, staphylomastigotes, was proposed for this stage. After 10 days of cultivation, 90% of the staphylomastigotes underwent differentiation (2nd differentiation phase) to trypomastigotes (.apprx. 98%) or epimastigotes (.apprx. 2%). Bloodstream trypomastigotes cultivated without TI-32 cells underwent the 1st, but not the 2nd differentiation phase, although occasional epimastigotes were seen (< 1%). TI-32 cells produced a labile factor(s) important not only for initiation of the 2nd differentiation phase but also for maintaining the parasites in the trpomastigote stage. The pH of the culture medium was not the initiating factor for the 2nd differentiation phase. Staphylomastigotes were as infective as bloodstream trypomastigotes, but metacyclic trypomastigotes isolated from culture after the 2nd differentiation phase were slightly more infective than bloodstream forms. EM of styphylomastigotes do not provide any evidence of exchange of genetic material between cells.