Caspase Activity and Virulence of Aspergillus Fumigatus

描述(由申请人提供)：机会霉菌病原体烟曲霉的感染继续增加，主要是由于器官移植的增加和更积极的免疫抑制方案的使用。尽管在抗真菌治疗方面取得了一些进展，但侵袭性曲霉病的预后仍然很差，死亡率接近90%，这强调了对这种微生物需要新的和更有效的治疗靶点。 Caspase依赖的程序性细胞死亡(PCD)是高等真核生物中一种高度保守的应激反应，其凋亡信号机制的组成部分被认为是最有前途的抗癌靶点之一。最近的研究表明，发芽酵母具有一种在PCD中起作用的不同的caspase，这表明真菌caspase也可能是潜在的治疗靶点。然而，caspase活性对烟曲霉菌生长和毒力的贡献尚不清楚。我们的初步数据表明，环境胁迫诱导了烟曲霉中caspase的活性，并且在烟曲霉菌基因组中同时缺失这两个caspase基因的突变体对氧化胁迫具有抗性。本研究的目的是确定这些半胱氨酸氨基转移酶对烟曲霉菌生长和毒力的贡献。利用caspase活性解除调控的烟曲霉突变体，我们建议检验以下假设： 1.caspase活性是菌丝最佳生长所必需的，特别是在体内可能遇到的胁迫条件下。 2.在播散性侵袭性曲霉病小鼠模型中，caspase活性是表达野生型毒力所必需的。

DESCRIPTION (provided by the applicant): Infections with the opportunistic mould pathogen Aspergillus fumigatus are continuing to increase, primarily as a consequence of the rise in organ transplantation and the use of more aggressive immunosuppressive regimens. Despite some advances in antifungal therapy the prognosis for invasive aspergillosis remains poor, with mortality rates approaching 90%, emphasizing the need for new and more effective therapeutic targets for this organism. Caspase-dependent programmed cell death (PCD) is a highly conserved stress response in higher eukaryotes, and components of the apoptosis signaling machinery are considered to be among the most promising anti-cancer targets. Recent studies have shown that budding yeast have a divergent caspase that has a role in PCD, suggesting that fungal caspases may also represent potential therapeutic targets. However, the contribution of caspase activity to growth and virulence of A. fumigatus is unknown. Our preliminary data indicate that caspase activity is induced in A. fumigatus by environmental stress, and that a mutant lacking both of the caspase genes in the A. fumigatus genome is resistant to oxidative stress. The aim of this proposal is to determine the contribution of these caspase to the growth and virulence of A. fumigatus. Using mutants of A. fumigatus with deregulated caspase activity we propose to test the following hypotheses: 1. That caspase activity is required for optimal mycelial growth, particularly under conditions of stress that would be encountered in vivo. 2. That caspase activity is required for the expression of wild type virulence in a mouse model of disseminated invasive aspergillosis.