A link between mating pheromone sensing and virulence of Cryptococcus neoformans

描述（由申请人提供）：新型隐球菌是一种人类致病真菌，可在免疫功能低下的个体中引起危及生命的脑膜脑炎。隐球菌病的一个重要方面是新生隐球菌细胞穿越血脑屏障的能力。虽然在过去的几年中已经阐明了涉及中枢神经系统（CNS）渗透的过程，但新型C.诱导这些过程的方法尚不清楚。有趣的是，新物种有两种交配类型（a和a）；然而，绝大多数临床分离株是交配型。在a和a株同时感染时，最常见的致病性隐球菌品种的同源菌株在个体感染时没有观察到毒力差异，但a细胞在中枢神经系统中占主导地位。通过比较个体感染和共感染中的a和a细胞，我们有机会确定进入中枢神经系统所需要的毒力因子。由于新生C.虫的细胞利用信息素感知和回应异性交配伴侣的细胞，在初步实验中，我们破坏了a细胞和a细胞的信息素感知，发现a细胞被信息素信号抑制而无法进入大脑。我们假设信息素信号在新生线虫进入中枢神经系统的过程中起着核心作用，并且该信息素信号的下游靶点影响新生线虫与血脑屏障的相互作用。我们建议通过使用改变信息素感知或信息素产生的突变株干扰体内信息素信号来测试这些假设。这些突变株的毒力将在个体感染和共感染中进行检查，并通过微阵列分析用于帮助确定该信息素信号的下游目标。这些信息将用于检查影响中枢神经系统进入的细胞特征的变化。此外，将在感染过程中检查信息素水平，以确定信息素信号何时可能对毒性潜力很重要。这些研究将有助于识别隐球菌渗透中枢神经系统的关键成分，并为设计减少中枢神经系统渗透以减轻疾病症状的治疗策略提供基础，并允许增加抗真菌药物的暴露。

DESCRIPTION (provided by applicant): Cryptococcus neoformans is a human pathogenic fungus that causes life-threatening meningoencephalitis in immunocompromised individuals. One important aspect of cryptococcosis is the ability of C. neoformans cells to cross the blood-brain barrier. While the processes involved in central nervous system (CNS) penetration have been elucidated over the past few years, the methods by which C. neoformans induces these processes are unknown. Interestingly, C. neoformans has two mating types (a and a); however the vast majority of clinical isolates are a mating type. While no differences in virulence are observed in individual infections with congenic strains in the most commonly pathogenic variety of Cryptococcus during coinfection of a and a strains simultaneously, the a cells predominate in the CNS. By comparing the a and a cells in individual and coinfections we have the opportunity to identify virulence factors specifically required for entry into the CNS. Because C. neoformans cells sense and respond to cells of the opposite mating partner using pheromones, in preliminary experiments we disrupted pheromone sensing in both a and a cells and discovered that a cells are inhibited from entering the brain by pheromone signaling. We hypothesize that pheromone signaling plays a central role in C. neoformans entry into the CNS and that the downstream targets of this pheromone signaling affect the interaction of C. neoformans with the blood-brain barrier. We propose to test these hypotheses by perturbing in vivo pheromone signaling using mutant strains altered in either pheromone sensing or pheromone production. The virulence of these mutant strains will be examined in individual and coinfections and used to help identify the downstream targets of this pheromone signaling by microarray analysis. This information will then be used to examine changes in cellular traits that affect CNS entry. Furthermore, pheromone levels will be examined during the infectious process to define when pheromone signaling is likely to be important for virulence potential. These studies will allow the identification of key components of CNS penetration by Cryptococcus and provide a foundation for treatment strategies designed to reduce CNS penetration to alleviate disease symptoms and allow for increased exposure to antifungal drugs.