Background

The mold Aspergillus fumigatus spreads through dispersion of its asexual spores, called conidia. When inhaled, these conidia are efficiently eliminated by innate immune defenses. But, in immunocompromised patients, conidia escape killing to germinate into hyphae which invade host cells and proliferate in blood vessels, often disseminating to other organs. lnvasive aspergillosis (lA) occurs in up to 15 % of Canadian patients with acute leukemia or undergoing allogenic stem cell transplantation, and the mortality rate of IA remains greater than 50%, despite the use of new antifungal agents. Novel approaches to modify the natural history of this illness are urgently needed. A fumigatus is an opportunistic pathogen with relatively low intrinsic virulence. As a result the growth rate of the organism plays a crucial role in its ability to cause disease, and strains with reductions in hyphal growth rate exhibit reduced or no virulence. Efficient hyphal growth is favored by the fact that during invasive aspergillosis there is no conidiation allowing the organism to direct its energy towards vegetative growth. Conversely, work from our group and others has demonstrate