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Host-parasite interactions during the development of Trypanosoma brucei

Research project P4/09 (Research action P4)

Persons :

Description :

The project aims to characterise the molecular mechanisms involved in adaptation of the protozoan parasite Trypanosoma bruceito the different hosts where it develops in the course of its life-cycle, various mammals on one hand, the tsetse fly on the other. Existing data concerning surface receptors and endocytosis in these parasites have revealed original characteristics which highlight the interest of these studies. Moreover, this work should shed light on the origin of the mechanisms for cell signalling and differentiation in higher eukaryotes and should open new prospects for therapeutic or prophylactic treatment against trypanosomiases, major parasitic diseases in developing countries. This project exploits the unique and internationally recognised potential of Belgian scientists in molecular parasitology. The participating teams are among world leaders in the study of antigenic variation (ULB), glycolysis (UCL), receptors (UCL, ULB), and immunosuppression (VUB) in the African trypanosome T. brucei.

Research focuses on the different developmental stages of the parasite.

1. Developmental stages in the mammal:

-Control of the immune system by the parasite (VUB, ULB). Characterization of the parasite components that are involved in the induction of the synthesis of TNF-alpha by macrophages, as well as those causing immunosuppression. Previous results allow to orient the work on the glycolipid anchor of the VSG (glycosylphosphatidylinositol, or GPI) in the first case, whereas in the second case, the identification of factors responsible for immunosuppression involves a gene screening strategy based on the use of specific antibodies.

-Characterization of surface receptors of the parasite (ULB, UCL, VUB). The aim is to clone the genes for the trypanosome receptors of low and high density lipoproteins (LDL, HDL), TNF-alpha and IFN-gamma using a strategy of «biopanning» of COS cells expressing a T. brucei cDNA library. Moreover, a mini-library of genes encoding the different surface receptors of the parasite will be constructed by screening with antibodies raised against purified extracts of the flagellar pocket fraction of the parasite.

-Recognition and intracellular processing of host molecules (UCL, VUB, ULB). Study of the processes of binding, uptake and intracellular trafficking of host components involved in the trypanosome growth, namely transferrin, LDL, HDL, TNF-alpha and IFN- gamma .

-Signal transduction pathways (ULB, UCL). On the basis of previous results, the work will focus particularly on four topics: the regulation and role of the different adenylate cyclase isoforms, the regulation and role of the single known phospholipase C (GPI-PLC, or VSG lipase), the characterization of G-proteins and associated components, and the localization and role of actin.

2. Developmental stages in the tsetse fly (ULB):

-Interactions with host components. Construction of cDNA libraries from various organs of the fly and expression in COS cells to allow screening for clones interacting with the trypanosome. This panning strategy should lead to identifying fly components involved in cell signalling of the parasite.

-Identification of ligands for the adenylate cyclases of the parasite and of the role of the cyclase isoforms. Purification of fly components that stimulate adenylate cyclase activity in procyclic cells. Analysis of the function of the different cyclase isoforms during the development of the parasite in the fly.

3.Regulation of gene expression during cell differentiation from one developmental stage to the next (ULB):

The researches focus on co- and post-transcriptional controls (respectively transcriptional elongation and control of mRNA abundance). It has been demonstrated that these controls are influenced by environmental conditions and play a major role in cellular differentiation in trypanosomes. The work involves identifying proteins that interact with primary transcripts to determine their rate of processing and stability, and to study their modifications during the life-cycle of the parasite.

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