In vivo-induction of Candida albicans morphogenesis

描述（由申请人提供）：白色念珠菌是人类的主要真菌病原体，是发病率和死亡率的重要原因，特别是在免疫功能低下的宿主中。与大多数病原体不同，白色念珠菌能够感染体内几乎所有的解剖部位，并且除了温血动物外没有已知的宿主。在单细胞（酵母）和丝状形式之间可逆切换的能力对入侵和致病过程有重要贡献。因此，理解酵母-细丝-酵母开关的信号和调控途径是一个很大的推动力。然而，检查这一过程的大多数研究都是在体外进行的，使用的条件是试图模仿宿主样的刺激。我们实验室最近的研究表明，在体外“锁定”酵母生长模式的“菌丝缺陷”突变体能够在体内粘膜组织侵袭期间形成细丝。其他数据表明，形态发生是由宿主在特定组织部位产生的信号触发的。此外，这些信号激活了体外沉默的形态发生途径。基于这些观察结果，我们假设白色念珠菌具有一种宿主环境感知机制，在体内粘膜细胞接触时刺激丝状生长。在这篇R21提案中，我们将利用新兴技术研究感染粘膜组织的白色念珠菌细胞的整体转录谱，并鉴定与宿主诱导的形态发生相关的基因。我们建议：1)鉴定在体内宿主-病原体相互作用过程中表达的白色念珠菌基因；2)鉴定在粘膜诱导的形态发生过程中特异性表达的白色念珠菌基因子集；3)验证全局表达数据集，4)评估敲除菌株在体外和体内进行形态发生的能力。据我们所知，这一提议将是第一个：1)确定白色念珠菌细胞在体内粘膜表面的转录特征，2)阐明新的分子靶点和途径，这些靶点和途径独立于主要的体外形态调节因子。这些研究将对理解宿主-真菌病原体相互作用产生重要的见解，并允许开发针对形态发生和侵袭过程的新的抗真菌策略。我们的研究结果将通过确定可能针对预防和治疗干预的毒力因素来影响当前的治疗策略。这些知识将加速我们诊断、治疗和控制人类头号真菌病原体的能力。

DESCRIPTION (provided by applicant): Candida albicans is the major fungal pathogen of humans, and is a significant cause of morbidity and mortality especially in immunocompromised hosts. Unlike most pathogens, C. albicans is capable of infecting virtually every anatomical site within the body and has no known reservoir outside of warm-blooded animals. The ability to reversibly switch between the unicellular (yeast) and filamentous form contributes significantly to the invasion and pathogenic process. Thus, there is a great impetus to understand the signals and regulatory pathways that govern the yeast-filament-yeast switch. The majority of studies examining this process, however, have been performed in vitro using conditions that attempt to mimic host-like stimuli. Recent studies in our laboratory have shown that `hyphal defective' mutants `locked' in the yeast mode of growth in vitro are capable of forming filaments during invasion of mucosal tissue in vivo. Additional data suggests that morphogenesis is triggered by host-derived signals at specific tissue sites. Furthermore, these signals activate a morphogenetic pathway that is silent in vitro. Based on these observations, we HYPOTHESIZE that C. albicans possesses a host environment-sensing mechanism that stimulates filamentous growth in response to in vivo mucosal cell contact. In this R21 proposal, we will use emerging technologies to investigate the global transcript profile of C. albicans cells infecting mucosal tissue in vivo and identify genes associated with host-induced morphogenesis. We propose to: 1) identify C. albicans genes expressed during the in vivo host-pathogen interaction; 2) identify a subset of C. albicans genes expressed specifically during mucosal-induced morphogenesis; 3) validate global expression datasets, and 4) assess the ability of knockout strains to undergo morphogenesis in vitro and in vivo. To our knowledge, this proposal will be the first to: 1) identify the transcriptional signature of C. albicans cells at the in vivo mucosal surface, and 2) elucidate new molecular targets and pathways that are independent of the major in vitro morphological regulators. These studies will generate significant insight into understanding the host-fungal pathogen interaction and allow the development of new antifungal strategies targeting the morphogenetic- and invasive-processes. PUBLIC HEALTH RELEVANCE Our findings will impact current treatment strategies by identifying virulence factors that may be targeted for prophylactic and therapeutic intervention. Such knowledge should accelerate our ability to diagnose, treat, and control the number one fungal pathogen of humans.