Critical Factors Influencing Echinocandin Resistance in Candida glabrata

描述(由申请人提供)：由念珠菌引起的侵袭性真菌感染是发病率和死亡率的主要原因。及时的诊断和适当的抗真菌治疗是患者处理的关键。不幸的是，可用于治疗的药物种类相对较少，而且它们正受到耐药性的影响。棘球菌素类药物是治疗念珠菌感染的重要抗真菌药物。然而，治疗失败的报道越来越多，尤其是光滑念珠菌，它是播散性念珠菌病的主要原因。在主要念珠菌中，棘球菌素耐药仍然相对少见。然而，光肩星天牛的情况并非如此，在某些高危中心，其耐药性现在超过了13%。众所周知，临床上导致治疗失败的棘球绦虫耐药性是由于 葡聚糖合成酶FKS亚基高度保守的热点区域。迫切需要了解FKS介导的棘球绦虫耐药发生的细胞因素。在这项提议中探索的新假设是，光肩星天牛棘球绦虫抗药性是由细胞因子促进的，这些细胞因子通过产生 一个意想不到的耐药细胞群，最终通过形成特有的FKS突变来逃避药物作用。这一假设得到了小鼠药效学研究的支持，这些研究表明，标准剂量(人体当量)的棘球绦虫药物治疗会导致药物耐受或持久的细胞群。这种行为与棘球菌素类药物作为推定的杀菌剂不一致。相反，体内数据表明，棘球菌素药物在标准剂量下起到了抑菌剂的作用。假设体内细胞通过诱导多种细胞代偿机制来应对棘球绦虫作用引起的细胞壁压力，从而获得暂时的药物耐受性。细胞和遗传因素促进从耐药持久细胞的高负荷群体中选择具有FKS基因突变的耐药变异体。为了更好地了解光滑棘球绦虫对棘球绦虫的耐药性，将在体外和体内模型中检测一系列细胞因子在FKS介导的棘球绦虫耐药性出现中的作用。具体地说，将使用适当的突变体和已知的这些途径的抑制剂来评估代偿性细胞壁应激反应、DNA修复减少、唑类耐药性、血清和潜在的新基因/途径的重要性。这项工作将利用工程等基因突变株和独特的系列遗传匹配的敏感和对FKS抗性的光肩星毛虫临床分离株。这些菌株将首次被描述基因组和转录组的变化，以评估已知机制的重要性，并阐明潜在的新的遗传刺激因素，潜在的抗药性出现。我们在过去十年中对临床分离株的棘球绦虫耐药性进行了详细的分子研究，为更好地理解光滑棘球绦虫产生棘球绦虫耐药性的分子基础奠定了坚实的基础。预计这些信息将提供重要的新见解和潜在的干预策略，以克服和/或防止棘球绦虫耐药性的出现。

DESCRIPTION (provided by applicant): Invasive fungal infections due to Candida species are a major cause of morbidity and mortality. Timely diagnosis and appropriate antifungal therapy are critical for patient management. Unfortunately, there are relatively few drug classes available for therapy and they are being compromised by drug resistance. The echinocandins are important antifungal agents for the treatment of patients with Candida infections. However, therapeutic failures are increasingly being reported especially with C. glabrata, which is a leading cause of disseminated candidiasis. Of the major Candida species, echinocandin resistance remains relatively uncommon. Yet, this is not the case for C. glabrata, where resistance now exceeds 13% in certain high-risk centers. It is well- established that clinical echinocandin drug resistance resulting in therapeutic failure is due to amino acid substitutions in highly conserved hot-spot regions of the Fks subunits of glucan synthase. There is a critical need to understand the cellular factors underlying the emergence of Fks-mediated echinocandin resistance. The novel hypothesis being explored in this proposal is that echinocandin resistance in C. glabrata is promoted by cellular factors that stabilize cells in response to drug by creating an unanticipated drug tolerant cell population, which ultimately escapes drug action by the formation of characteristic fks mutations. This hypothesis is supported by pharmacodynamic studies in mice indicating that echinocandin drug therapy at a standard dosage (human equivalent) results in drug tolerant or persistent cell populations. Such behavior is inconsistent with echinocandin drugs as presumed fungicidal agents. Rather, the in vivo data suggests that the echinocandin drugs behave as fungistatic agents at a standard dosage. It is hypothesized that in vivo cells become temporally drug- tolerant by inducing a variety of cellular compensatory mechanisms in response to cell wall stress due to echinocandin action. Cellular and genetic factors promote selection of drug resistant variants with mutations in FKS genes from high burden populations of drug tolerant persistor cells. To better understand echinocandin resistance in C. glabrata, a range of cellular factors will be examined in in vitro and in vivo models for their role in emergence of Fks-mediated echinocandin resistance. Specifically, the importance of compensatory cell wall stress responses, decreased DNA repair, azole resistance, serum, and potential novel genes/pathways will be evaluated using appropriate mutants, along with known inhibitors of these pathways. This work will exploit engineered isogenic mutant strains and a unique collection of serial genetically-matched susceptible and fks-resistant clinical isolates of C. glabrata. These latter isolates will be profiled for changes n the genome and transcriptome for the first time to assess the importance of known mechanisms and elucidate potential new genetic incites underlying resistance emergence. Our detailed molecular studies of echinocandin resistance with clinical isolates over the past decade provide a strong foundation to better understand the molecular basis underlying the emergence of echinocandin resistance in C. glabrata. It is anticipated that this information will provide important new insights and potential intervention strategies to overcome and/or prevent the emergence of echinocandin resistance.