Mammalian cell invasion and intracellular trafficking by Trypanosoma cruzi infective forms

Renato A Mortara,Noemi N Taniwaki,Maria Cecília D.C Fernandes,Claudio V Da Silva,Carolina L'Abbate,Adriana B Fernandes,Walter K Andreoli,Solange Da Silva

doi:10.1590/s0001-37652005000100006

Abstract

Trypanosoma cruzi, the etiological agent of Chagas disease, occurs as different strains or isolates that may be grouped in two major phylogenetic lineages: T. cruzi I, associated with the sylvatic cycle and T. cruzi II, linked to the human disease. In the mammalian host the parasite has to invade cells and many studies implicated the flagellated trypomastigotes in this process. Several parasite surface components and some of host cell receptors with which they interact have been identified. Our work focused on how amastigotes, usually found growing in the cytoplasm, can invade mammalian cells with infectivities comparable to that of trypomastigotes. We found differences in cellular responses induced by amastigotes and trypomastigotes regarding cytoskeletal components and actin-rich projections. Extracellularly generated amastigotes of T. cruzi I strains may display greater infectivity than metacyclic trypomastigotes towards cultured cell lines as well as target cells that have modified expression of different classes of cellular components. Cultured host cells harboring the bacterium Coxiella burnetii allowed us to gain new insights into the trafficking properties of the different infective forms of T. cruzi, disclosing unexpected requirements for the parasite to transit between the parasitophorous vacuole to its final destination in the host cell cytoplasm.

Highlights

Trypanosoma cruzi, the etiological agent of Chagas’ disease, occurs as different strains or isolates that may be grouped in two major phylogenetic lineages: T. cruzi I, associated with the sylvatic cycle and T. cruzi II, linked to the human disease
Trypomastigotes are usually found in an acidic membrane-bound compartment referred to as phagosome or parasitophorous vacuole (PV), from where they eventually escape to differentiate into amastigotes in the cytoplasm (Kress et al 1975, Ley et al 1990, Meirelles et al 1986, 1987, 1992, Milder and Kloetzel 1980, Nogueira and Cohn 1976, Tanowitz et al 1975)
The variety of mechanisms used for invasion and escape from the parasitophorous vacuoles engaged by amastigotes and trypomastigotes is consistent with the complex repertoires of both infective forms and surface molecules that the parasite has evolved to ensure host colonization

Summary

AMASTIGOTES IN HeLa AND Vero CELLS

It has become increasingly evident that several intracellular pathogens specialized in subverting host cell pathways to their benefit. Besides the formation of the surface cups in HeLa cells, we noticed a remarkable response to extracellular amastigotes when they invade Vero cells In this fibroblastic cell line devoid of surface microvilli, protrusive lamellae formed at the sites of amastigote invasion (Procópio et al 1999) were markedly similar to shown by attaching Shigella flexneri (Bourdet-Sicard et al 2000, Clerc and Sansonetti 1987, Tran et al 2000). In all the actin-rich membrane extensions formed around invading amastigotes or trypomastigotes, accumulation of cytoskeletal elements, integrins or matrix elements could be detected, with some variability observed between the infective forms and target cells (Procópio et al 1999) These results were again consistent with the notion that each parasite-host cell pair mobilizes specific interacting components (see Table I). Activated (GTPase activity deficient) mutants of RhoA and Rac were found to

Ama pseudopodium cup none

TRYPOMASTIGOTES OF STRAINS FROM THE TWO MAJOR PHYLOGENETIC LINEAGES

Findings

CELL INVASION AND INTRACELLULAR FATE OF INFECTIVE FORMS