title: PKSP-dependent reduction of phagolysosome fusion and intracellular kill of Aspergillus fumigatus conidia by human monocyte-derived macrophages.
abstract: Previously, we described the isolation of an Aspergillus fumigatus mutant producing non-pigmented conidia, as a result of a defective polyketide synthase gene, pksP (polyketide synthase involved in pigment biosynthesis). The virulence of the pksP mutant was attenuated in a murine animal infection model and its conidia showed enhanced susceptibility towards damage by monocytes in vitro. Because macrophage-mediated killing is critical for host resistance to aspergillosis, the interaction of both grey-green wild-type conidia and white pksP mutant conidia with human monocyte-derived macrophages (MDM) was studied with respect to intracellular processing of ingested conidia. After phagocytosis, the percentage of wild-type conidia residing in an acidic environment was approximately fivefold lower than that observed for non-pigmented pksP mutant conidia. The phagolysosome formation, as assessed by co-localization of LAMP-1 and cathepsin D with ingested conidia, was significantly lower for wild-type conidia compared with pksP mutant conidia. Furthermore, the intracellular kill of pksP mutant conidia was significantly higher than of wild-type conidia, which was markedly increased by chloroquine, a known enhancer of phagolysosome fusion. Taken together, these findings suggest that the presence of a functional pksP gene in A. fumigatus conidia is associated with an inhibition of phagolysosome fusion in human MDM. These data show for the first time that a fungus has the capability to inhibit the fusion of the phagosome with the lysosome. This finding might help explain the attenuated virulence of pksP mutant strains in a murine animal model and provides a conceptual frame to understand the virulence of A. fumigatus.
authors.affiliation: Institut für Medizinische Mikrobiologie und Hygiene, Johannes Gutenberg-Universität Mainz, Hochhaus am Augustusplatz, D-55101 Mainz, Germany. bjahn@mail.uni-mainz.de
authors.forename: Bernhard
authors.initials: B
authors.lastname: Jahn
authors.forename: Kim
authors.initials: K
authors.lastname: Langfelder
authors.forename: Ulrike
authors.initials: U
authors.lastname: Schneider
authors.forename: Christine
authors.initials: C
authors.lastname: Schindel
authors.forename: Axel A
authors.initials: AA
authors.lastname: Brakhage
mesh_terms: D000165:Acridine Orange; D001228:Aspergillosis / Q000382:microbiology; D001232:Aspergillus fumigatus / Q000201:enzymology / Q000254:growth & development* / Q000472:pathogenicity*; D002459:Cell Fusion; D002478:Cells, Cultured; D006801:Humans; D008264:Macrophages / Q000276:immunology / Q000382:microbiology*; D009000:Monocytes / Q000382:microbiology; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism; D010587:Phagocytosis; D010588:Phagosomes / Q000473:pathology* / Q000502:physiology
chemical_list: D009097:Multienzyme Complexes; D000165:Acridine Orange