Critical Factors Influencing Echinocandin Resistance in Candidaglabrata

侵袭性真菌感染是全球发病率和死亡率的主要原因，占近1.4 每年有数百万人死亡。血流真菌感染，主要由念珠菌属的酵母引起， 与高死亡率(45%-75%)有关，并对免疫功能受损的人构成严重威胁， 包括癌症患者、器官移植受者、早产儿和艾滋病患者。棘球绦虫 药物于2001年首次获准临床使用，是我们有限的抗真菌药物医疗机构的重要组成部分。 对假丝酵母菌有广泛的抗药性。这些药物阻止真菌葡聚糖合成酶，一种酶 催化β-1，3葡聚糖的生物合成，这是真菌细胞壁的主要结构成分。棘球绦虫 导致临床失败的耐药性是由于基因FKS1和FKS2的“热点”区域突变而产生的， 编码β-1，3葡聚糖合成酶亚基。而大多数假丝酵母菌。一直保持在最低水平 棘球绦虫耐药的频率(1-3%)，光滑假丝酵母菌是一个例外，有一些移植 研究中心报告光滑棘球绦虫对棘球绦虫的耐药率为10-15%。棘球绦虫耐药性总是会出现 在治疗期间，随着越来越多的患者接触到抗真菌药物，预计这一数字将进一步增加 预防用药和棘球菌素类药物变得通用。此外，光肩星天牛的发病率已被 它现在是北美仅次于白色念珠菌的第二大真菌病原体， 欧洲。因此，迫切需要更好地了解导致出现 光肩星天牛对棘球菌素的抗性。这一建议基于最近的研究，围绕这一假说展开。 由我们的实验室和其他人发表的研究表明，抵抗的出现之前有两个阶段：耐受，即 多种细胞因素在药物暴露期间稳定光滑毛囊线虫，并在对棘球绦虫耐药的地方逃逸 FKS突变发生在耐药细胞中。我们建议找出导致这两种情况的因素 通过以下补充方法进行分期：(1)测试候选基因在药物耐受中的作用 和体外抗性(逃逸)的发展和体内验证，以及(2)鉴定基因 在我们广泛收集的光滑念珠菌临床分离株中影响药物耐受性和逃逸的多态 (约1000个菌株)来自美国和全球各地的不同地理位置。对于每种方法， 我们将利用我们定义良好的体外测试和最近开发的与临床相关的胃肠道 在人类中出现的模拟耐药性的定植和腹内脓肿模型。加在一起，这些 方法将定义重要真菌病原体的潜在生物学的关键特征，并确定 可以提高治疗成功率和防止耐药性发展的靶点。此外， 了解临床光滑念珠菌耐药和耐药的决定因素将导致潜在的 追踪高威胁菌株的分子流行病学的诊断分析。

Invasive fungal infections are a major cause of global morbidity and mortality, accounting for nearly 1.4 million deaths a year. Bloodstream fungal infections, largely caused by yeasts of the Candida genus, are associated with high mortality rates (45-75%) and pose a serious threat to immunocompromised individuals, including cancer patients, organ transplant recipients, premature infants, and AIDS patients. The echinocandin drugs, first approved for clinical use in 2001, are an essential part of our limited antifungal drug armamentarium and are broadly active against Candida species. These drugs block fungal glucan synthase, an enzyme catalysing the biosynthesis of β-1,3 glucan, a major structural component of the fungal cell wall. Echinocandin resistance resulting in clinical failures arises due to mutations in the “hot spot” regions of genes FKS1 and FKS2, which encode β-1,3 glucans synthase subunits. While most Candida spp. have shown a consistently low frequency of echinocandin resistance (1-3%), Candida glabrata has been an exception, with some transplant centers reporting C. glabrata echinocandin resistance rates of 10-15%. Echinocandin resistance always arises during therapy and is expected to increase further, as expanding numbers of patients are exposed to antifungal prophylaxis and echinocandin class drugs become generic. Furthermore, C. glabrata incidence has been increasing and it now is the second most prevalent fungal pathogen after C. albicans in North America and Europe. Thus, there is an urgent need to better understand the factors that contribute to emergence of echinocandin resistance in C. glabrata. This proposal centers around the hypothesis, based on recent studies published by our lab and others, that emergence of resistance is preceded by two stages: tolerance, where multiple cellular factors stabilize C. glabrata during drug exposure, and escape, where echinocandin-resistant fks mutations develop in the drug-tolerant cells. We propose to identify factors contributing to both of these stages by the following complementary approaches: (1) testing the roles of candidate genes in drug tolerance and development of resistance (escape) in vitro and validating them in vivo, and (2) identifying genetic polymorphisms that influence drug tolerance and escape in our extensive collection of C. glabrata clinical isolates (~1000 strains) derived from diverse geographical locations in the U.S. and around the globe. For each approach, we will utilize our well-defined in vitro assays and recently developed clinically-relevant gastrointestinal colonization and intraabdominal abscess models that mimic resistance emergence in humans. Together, these approaches will define critical features of the underlying biology of an important fungal pathogen and identify targets that can improve therapeutic success and prevent development of resistance. Furthermore, understanding determinants of tolerance and resistance in clinical C. glabrata strains will lead to potential diagnostic assays to track the molecular epidemiology of high-threat strains.