Nesbitt Jason R, Steves Elizabeth Y, Schonhofer Cole R, Cait Alissa, Manku Sukhbir S, Yeung Juliana H F, Bennet Andrew J, McNagny Kelly M, Choy Jonathan C, Hughes Michael R, Moore Margo M
Department of Biological Sciences and the Centre for Cell Biology, Development and Disease, Simon Fraser University, Burnaby, BC, Canada.
Biomedical Research Centre, The University of British Columbia, Vancouver, BC, Canada.
Front Microbiol. 2018 Jan 18;8:2706. doi: 10.3389/fmicb.2017.02706. eCollection 2017.
is a filamentous fungus that can cause a life-threatening invasive pulmonary aspergillosis (IPA) in immunocompromised individuals. We previously characterized an -sialidase from that prefers the sialic acid substrate, 2-keto-3-deoxy-D--D--nononic acid (Kdn); hence it is a Kdnase. Sialidases are known virulence factors in other pathogens; therefore, the goal of our study was to evaluate the importance of Kdnase in . A knockout strain () was unable to grow on medium containing Kdn and displayed reduced growth and abnormal morphology. was more sensitive than wild type to hyperosmotic conditions and the antifungal agent, amphotericin B. In contrast, had increased resistance to nikkomycin, Congo Red and Calcofluor White indicating activation of compensatory cell wall chitin deposition. Increased cell wall thickness and chitin content in were confirmed by electron and immunofluorescence microscopy. In a neutropenic mouse model of invasive aspergillosis, the strain had attenuated virulence and a significantly lower lung fungal burden but only in animals that received liposomal amphotericin B after spore exposure. Macrophage numbers were almost twofold higher in lung sections from mice that received the strain, possibly related to higher survival of macrophages that internalized the conidia. Thus, Kdnase is important for fungal cell wall integrity and virulence, and because Kdnase is not present in the host, it may represent a potential target for the development of novel antifungal agents.
是一种丝状真菌，可在免疫功能低下的个体中引起危及生命的侵袭性肺曲霉病（IPA）。我们之前鉴定了一种来自的唾液酸酶，它更喜欢唾液酸底物2-酮-3-脱氧-D- -D- -壬糖酸（Kdn）；因此它是一种Kdn酶。唾液酸酶在其他病原体中是已知的毒力因子；因此，我们研究的目的是评估Kdn酶在中的重要性。一个基因敲除菌株（）无法在含有Kdn的培养基上生长，并且生长减少且形态异常。与野生型相比，对高渗条件和抗真菌剂两性霉素B更敏感。相反，对多氧霉素、刚果红和荧光增白剂具有更高的抗性，表明补偿性细胞壁几丁质沉积被激活。通过电子显微镜和免疫荧光显微镜证实了中细胞壁厚度和几丁质含量增加。在侵袭性曲霉病的中性粒细胞减少小鼠模型中，菌株的毒力减弱，肺部真菌负荷显著降低，但仅在孢子暴露后接受脂质体两性霉素B的动物中如此。接受菌株的小鼠肺切片中的巨噬细胞数量几乎高出两倍，这可能与内化分生孢子的巨噬细胞更高的存活率有关。因此，Kdn酶对于真菌细胞壁完整性和毒力很重要，并且由于宿主中不存在Kdn酶，它可能代表新型抗真菌剂开发的潜在靶点。
