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Full Abstracts – IMMUNITY AND PATHOGENESIS
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A model for intracellular parasitism in Drosophila.
Dominique X. Ferrandon, Sebastian Niehus, Adrien Franchet, Marie-Céline Lafarge, David
Giacomini. IBMC, CNRS UPR 9022, Université de Strasbourg, France.
While much is known about
Drosophila
host defense against extracellular bacterial and fungal pathogens, intracellular host defenses not mediated by
autophagy remain a mystery. Also, no
Drosophila
model with a natural obligate intracellular eukaryotic parasite has been developed so far. Here, we report
on the development of such a model using the microsporidium
Tubulinosema ratisbonensis
, which sometimes contaminates laboratory stocks, and which, if
not kept in check, can eradicate Drosophila cultures. Microsporidia are highly derived intracellular fungi, which infect orally their fly host through spores.
Spores infect host cells through a unique mechanism that involves the evagination of a polar tube through which the spore cytoplasm and nuclei are
transferred directly into the host cells.
We have developed an adult infection model in which flies succumb to
T. ratisbonensis
proliferation in a temperature and dose-sensitive manner. Host
defenses include the cellular and humoral systemic immune responses. We have also developed cell culture models. Some cell lines are resistant to the
infection while others are permissive. We find that host cell invasion is an active process, which involves both the parasite and the host through
phagocytosis. Strikingly, infected cells become multinuclear giant cells within three days and are reminiscent of xenomas described in other systems by
classical authors about a century ago. New spores are produced within 9-12 days. We have performed transcriptomics and metabolomics analyses and,
surprisingly, find that the parasite takes control of its host cell very early on during the infection.
This novel model will allow us to study host-parasite relationships at multiple levels and should yield an unprecedented insight into the molecular bases of
parasitism. Finally, we have established methods for prophylaxis and protocols to cure microsporidia-infected stocks from the parasites.