LYT1 protein is required for efficient in vitro infection by Trypanosoma cruzi

Trypanosoma cruzi invasion of host cells involves several discrete steps: attachment, parasite internalization mediated by recruitment and fusion of host cell lysosomes, and escape from the parasitophorous vacuole to liberate amastigotes to multiply freely in the cytosol. This report describes the initial characterization of the LYT1 gene and the demonstration that the gene product is involved in cell lysis and infectivity. Mutational analysis demonstrated that deletion of LYT1 resulted in attenuation of infection, which was associated with diminished hemolytic activity. Reintroduction of LYT1 restored infectivity in null mutants, confirming the critical role of LYT1 in infection. Additionally, in vitro stage transition experiments with LYT1-deficient lines showed that these parasites converted to extracellular amastigote-like cells and metacyclic trypomastigotes more rapidly than wild-type parasites, suggesting that the diminished infectivity was not a result of the LYT1 deficiency that affected the parasite's ability to complete the life cycle.