Amoebiasis, a human infection developed by 50 million persons every year, is caused by the protozoan parasite, Entamoeba histolytica. The parasite invades the intestinal mucosa where it causes dysentery, in some cases liver abscesses are formed too. Two major processes sustain amoebiasis: (i) amoebic motility supported by the interaction with the extracellular matrix and the reorganization of the amoebic cytoskeleton, and (ii) adhesion to human cells that is a consequence of the activity of surface receptors and cytoskeleton dynamics of both the amoeba and the host cell. Our project aims to:

1. Elucidate the cytoskeletal changes necessary for motility as well as the signaling pathways triggered by the interactions between the parasite and the external environment.

2. Identify the parasite molecules necessary for amoebic interaction with human cells and their role in the cross-talk between amoeba and human cells leading to cell death and inflammation.

3. Analyze amoebiasis by pathophysiology and by biotechnology developments.

Cellular analysis of cytoskeleton activities during chemotaxis and phagocytosis

E. histolytica has remarkably adapted its very simple cytoskeleton to motility, infection and phagocytosis of human cells. We have identified principal actors of the cytoskeleton dynamics, molecularly analyzed the encoding genes and further analyzed their functions. A Physics approach allows to conclude on the capital role of the parasite’s myosins in the mechanical and visco-elastic properties of its versatile cytoskeleton. A proteomic high-resolution analysis of phagosomes provided a first global view of their composition revealing new cystokeleton components and signaling molecules associated to myosins. Mobility of E. histolytica is enhanced by pro-inflammatory molecules and the PAK kinase is involved in parasite polarization during chemotaxis.

Imaging the infectious process in a tri-dimensional living tissue highlighted the role of adhesive molecules in parasite motility during the liver infection, chemotaxis towards inflammatory molecules and the onset of cellular apoptosis.

Expression analysis of genes involved in Entamoeba histolytica pathogenic process.

Blockage of transcripts by antisense and RNA interference, enabling down regulation of gene expression, has been developed with a large success. Thanks to the completion of a genomic project, we have set up a dedicated microarray with E. histolytica transcripts. Using them, we conclude that infection relies on a stress response in the parasite. A diverse group of transcripts encoding new lysine rich proteins have been revealed as relevant pathogenic factors. One of them, KERP1, has been in addition evaluated as an efficient candidate for diagnosis of the infection. Our next plans are to develop a deeper analysis of the parasite cytoskeleton related activities, and the molecular and cellular analysis leading to understand the trafficking of the new pathogenic factors identified; as well as their role in the killing of human cells. Our ultimate aim is to progress in the understanding of the amoebic invasive process. This will enable the formulation of innovative strategies for a specific diagnosis and treatment of amoebiasis.

Keywords: Amoebiasis, Entamoeba, motility, phagocytosis, microarrays, proteomics