Fig 1. Comparative course of infection of human fibroblasts with T. cruzi CL Brener and CL-14.

Intracellular T. cruzi life stages in mammalian cells: extracellular T. cruzi trypomastigotes actively penetrate mammalian cells where they differentiate into amastigotes and escape the vacuole before beginning to proliferate at ~24 hours post-infection (A). Amastigotes replicate intracellularly in the host cell cytoplasm for 3–5 days, and then differentiate into motile trypomastigotes that are eventually released upon disruption of the host cell. Tissue-culture derived trypomastigotes of the CLB and CL-14 T. cruzi strains were similarly able to establish intracellular infection in cultured HFF (B) but exhibited markedly different intracellular growth dynamics as amastigotes. (C) Differences in the peak day of trypomastigote release from infected monolayers (D).