Critical Factors Influencing Echinocandin Resistance in Candida glabrata

描述（由申请方提供）：念珠菌属引起的侵袭性真菌感染是发病和死亡的主要原因。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，并且它们正受到耐药性的影响。棘白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，特别是与C。glabrata，其是播散性念珠菌病的主要原因。在主要念珠菌属中，棘白菌素耐药仍然相对罕见。然而，这不是C的情况。glabrata，在某些高风险中心，耐药性现在超过13%。众所周知，导致治疗失败的临床棘白菌素耐药性是由于棘白菌素中的氨基酸取代。 葡聚糖合酶的Fks亚基的高度保守的热点区域。有一个关键的需要，以了解潜在的FKS介导的棘白菌素耐药性的出现的细胞因子。本研究中探索的新假设是，棘白菌素耐药性在C。glabrata是由细胞因子促进的，细胞因子通过产生 未预料到的耐药细胞群，其最终通过形成特征性FKS突变而逃避药物作用。这一假设得到了小鼠药效学研究的支持，表明标准剂量（人体等效剂量）的棘白菌素药物治疗可产生药物耐受性或持久性细胞群。这种行为与棘白菌素药物作为假定的杀真菌剂不一致。相反，体内数据表明棘白菌素药物在标准剂量下表现为抑真菌剂。假设体内细胞通过诱导多种细胞补偿机制响应于棘白菌素作用引起的细胞壁应激而变得暂时耐药。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基因突变的耐药变体。为了更好地了解棘白菌素耐药的C。glabrata，将在体外和体内模型中检查一系列细胞因子在Fks介导的棘白菌素抗性出现中的作用。具体而言，将使用适当的突变体，沿着这些途径的已知抑制剂，评价补偿性细胞壁应激反应、DNA修复减少、唑类耐药、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一系列基因匹配的敏感和fks耐药的临床分离株的独特集合。光滑的将首次对这些分离株的基因组和转录组变化进行分析，以评估已知机制的重要性，并阐明潜在的新的耐药基因。在过去的十年中，我们对临床分离株的棘白菌素耐药性进行了详细的分子研究，为更好地了解棘白菌素耐药性在C.光滑的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/或预防棘白菌素耐药性的出现。

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.