Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820, Merelbeke, Belgium.
Environ Microbiol Rep. 2013 Dec;5(6):819-24. doi: 10.1111/1758-2229.12082. Epub 2013 Jul 22.
Aspergillus fumigatus and free-living amoebae are common inhabitants of soil. Mechanisms of A. fumigatus to circumvent the amoeba's digestion may facilitate overcoming the vertebrate macrophage defence mechanisms. We performed co-culture experiments using A. fumigatus conidia and the amoeba Acanthamoeba castellanii. Approximately 25% of the amoebae ingested A. fumigatus conidia after 1 h of contact. During intra-amoebal passage, part of the ingested conidia was able to escape the food vacuole and to germinate inside the cytoplasm of A. castellanii. Fungal release into the extra-protozoan environment by exocytosis of conidia or by germination was observed with light and transmission electron microscopy. These processes resulted in structural changes in A. castellanii, leading to amoebal permeabilization without cell lysis. In conclusion, A. castellanii internalizes A. fumigatus conidia, resulting in fungal intracellular germination and subsequent amoebal death. As such, this interaction highly resembles that of A. fumigatus with mammalian and avian macrophages. This suggests that A. fumigatus virulence mechanisms to evade macrophage killing may be acquired by co-evolutionary interactions among A. fumigatus and environmental amoebae.
烟曲霉和自由生活的阿米巴原虫是土壤中常见的居民。烟曲霉规避阿米巴消化的机制可能有助于克服脊椎动物巨噬细胞防御机制。我们使用烟曲霉分生孢子和阿米巴原虫棘阿米巴属进行了共培养实验。接触 1 小时后，大约 25%的阿米巴原虫摄入了烟曲霉分生孢子。在细胞内传递过程中，部分摄入的分生孢子能够从吞噬体中逃脱，并在棘阿米巴属的细胞质内发芽。通过出芽或发芽，用荧光和透射电子显微镜观察到分生孢子从细胞内到细胞外环境的释放。这些过程导致棘阿米巴属发生结构变化，导致阿米巴原虫通透性增加而不发生细胞裂解。总之，棘阿米巴属内化烟曲霉分生孢子，导致真菌细胞内发芽和随后的阿米巴原虫死亡。因此，这种相互作用非常类似于烟曲霉与哺乳动物和禽类巨噬细胞的相互作用。这表明，烟曲霉逃避巨噬细胞杀伤的毒力机制可能是通过烟曲霉与环境阿米巴之间的共同进化相互作用获得的。
