Jahn Bernhard, Langfelder Kim, Schneider Ulrike, Schindel Christine, Brakhage Axel A
Institut für Medizinische Mikrobiologie und Hygiene, Johannes Gutenberg-Universität Mainz, Hochhaus am Augustusplatz, D-55101 Mainz, Germany.
Cell Microbiol. 2002 Dec;4(12):793-803. doi: 10.1046/j.1462-5822.2002.00228.x.
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.
此前，我们描述了一株烟曲霉突变体的分离情况，该突变体由于聚酮合酶基因pksP（参与色素生物合成的聚酮合酶）存在缺陷而产生无色素分生孢子。在小鼠动物感染模型中，pksP突变体的毒力减弱，其分生孢子在体外对单核细胞损伤的敏感性增强。由于巨噬细胞介导的杀伤作用对宿主抵抗曲霉病至关重要，因此针对摄入的分生孢子的细胞内加工过程，研究了灰绿色野生型分生孢子和白色pksP突变体分生孢子与人单核细胞衍生巨噬细胞（MDM）的相互作用。吞噬作用后，处于酸性环境中的野生型分生孢子的百分比比无色素的pksP突变体分生孢子低约五倍。通过LAMP-1和组织蛋白酶D与摄入的分生孢子的共定位评估，野生型分生孢子的吞噬溶酶体形成明显低于pksP突变体分生孢子。此外，pksP突变体分生孢子的细胞内杀伤率明显高于野生型分生孢子，氯喹（一种已知的吞噬溶酶体融合增强剂）可显著提高其杀伤率。综上所述，这些发现表明烟曲霉分生孢子中功能性pksP基因的存在与人类MDM中吞噬溶酶体融合的抑制有关。这些数据首次表明真菌具有抑制吞噬体与溶酶体融合的能力。这一发现可能有助于解释pksP突变体菌株在小鼠动物模型中毒力减弱的原因，并为理解烟曲霉毒力提供一个概念框架。
