Critical Factors Influencing Echinocandin Resistance in Candida glabrata

总结 由念珠菌属引起的侵袭性真菌感染是发病率和死亡率的主要原因。 及时诊断和适当的抗真菌治疗是患者管理的关键。 不幸的是，可用于治疗的药物种类相对较少， 被抗药性所破坏棘白菌素类是重要的抗真菌药物， 治疗念珠菌感染的患者。然而，治疗失败越来越多地被 特别报道了C. glabrata，其是播散性念珠菌病的主要原因。的 虽然是念珠菌属的主要菌种，但棘白菌素耐药性仍然相对罕见。但这并不是 C的情况。glabrata，在某些高风险中心，耐药性现在超过13%。很好- 确定临床棘白菌素耐药性导致治疗失败是由于氨基 在葡聚糖合酶的Fks亚基的高度保守的热点区域中的酸取代。那里 是一个关键需要了解的细胞因子的出现，FKS介导的 棘白菌素抗性在这项提议中探索的新假设是棘白菌素 C.抗性glabrata是由细胞因子促进的，细胞因子通过以下方式稳定细胞对药物的反应： 产生了一个意料之外的耐药细胞群，最终逃脱药物的作用， 特征性FKS突变的形成。药效学研究支持这一假设 在小鼠中，表明棘白菌素药物治疗在标准剂量（人类等效剂量）下导致 耐药或持久的细胞群。这种行为与棘白菌素药物不一致， 推测为杀真菌剂。相反，体内数据表明，棘白菌素药物的行为， 标准剂量的抑真菌剂。据推测，体内细胞暂时成为药物- 通过诱导多种细胞补偿机制来响应细胞壁应激， 棘白菌素的作用。细胞和遗传因素促进了耐药变异体的选择， 来自耐药持久细胞的高负荷群体的FKS基因突变。更好地 了解棘白菌素在C. glabrata，一系列细胞因子将在 体外和体内模型，用于其在Fks介导的棘白菌素抗性出现中的作用。 具体来说，补偿性细胞壁应激反应的重要性，减少DNA修复，唑 抗性、血清和潜在的新基因/途径将使用适当的突变体进行评估， 沿着这些途径的已知抑制剂。这项工作将利用工程等基因突变体 菌株和一系列基因匹配的敏感和fks耐药临床 分离的C.光滑的这些分离株将被分析基因组的变化， 转录组首次评估已知机制的重要性，并阐明 潜在的新基因激发潜在的抗性出现。我们详细的分子研究 在过去的十年中，临床分离株的棘白菌素耐药性为 更好地理解棘白菌素耐药性出现的分子基础。 光滑的预计这些信息将提供重要的新见解和潜力， 干预策略，以克服和/或预防棘白菌素耐药性的出现。

SUMMARY 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 in 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.