Etude des interactions hôte-parasite dans le cadre d'infections par des microsporidies, un groupe de champignons parasites intracellulaires obligatoires

摘要

Within the host-parasite interaction, the parasite need to cross the same barriers whatever the host considered. First, the parasite has to meet its host and to escape its defense systems. For this purpose, the parasites have developed, during coevolution, molecular strategies allowing them to hijack the host networks, leading to the set-up of a real molecular crosstalk. Microsporidia, which are obligate intracellular parasites, have probably developed very sophisticated strategies to hijack their host cell functions as they are strongly dependent to their hosts. The objective of this thesis was to pave the way to the deciphering of the molecular dialogue that takes place during the interaction between a microsporidia and its host, at two different integration levels. At the cellular level, the study of the proteome response of human fibroblast cells to the infection by Anncaliia algerae allowed us to suggest the existence of a lure strategy used by A. algerae to bypass the host response. At the tissue level, the study of the midgut proteome response of honeybees infected by Nosema ceranae revealed a disturbance of the intestinal homeostasis. These results lead us to the hypothesis of a negative impact of the infection on the midgut epithelium renewal rates. This assumption was confirmed by a monitoring of the multiplication rate of intestinal stem cells during a kinetics of infection and of the expression of genes implicated in the signaling pathways controlling this renewal. However, the underlying mechanisms allowing microsporidia to develop in hosts are not known and deserve to be explored.