Congenic strains of serotype A Cryptococcus neoformans

描述(申请人提供)：新生隐球菌是一种重要的人类真菌病原体，可引起危及生命的感染。感染本质上是机会主义的，通常发生在免疫功能低下的患者中，艾滋病患者面临的风险最大。隐球菌病通常表现为脑膜炎，在艾滋病患者中通常被视为无法治愈，可能需要终身抗真菌治疗。感染是世界性的，大约90%-95%的感染是由A型血清菌株引起的。这种真菌作为病原体的重要性导致了一项基因组测序项目的征集和资助。然而，选择的毒株是D型毒株，它引起的感染不到所有感染的10%。之所以选择这种菌株，是因为存在性别相容的菌株(命名为MATAlpha和Mata)，而由于没有可生育的Mata菌株，没有相容的A型血清菌株。在新生隐孢子虫中交配的另一个重要意义是，几乎所有的感染都是由一种交配型(MATAlpha)引起的。 我们最近发现了一株A型MATA菌株，该菌株具有生育能力，并与A型MATAlpha菌株有效杂交，包括H99菌株，该菌株是该血清型的标准实验室菌株。这种菌株的存在为研究新生葡萄球菌提供了一个强有力的工具，因为它将使传统的遗传研究能够在A型血清菌株中进行。这项提议包括三个目标。第一个目标是准备两对仅在交配类型上不同的同源菌株。遗传标记将被插入到这些菌株中，使它们成为未来遗传和分子研究的有用工具。第二个目标将测试交配型在毒力中的作用。通过在这些实验中使用同源菌株，交配型基因座上的信息在毒力中的作用可以独立于非交配型信息来测试。在最后一个目的中，将克隆和定位A型MATA交配型基因座以确定其大小。目前，新生隐孢子虫的四个交配型基因座中有三个是变种。新生杆菌(包括A型和D型)处于不同的特征阶段。分离A型MATA基因将完成这项研究，这一研究意义重大，因为交配型在毒力中扮演着重要角色。

DESCRIPTION (provided by applicant): Cryptococcus neoformans is an important human fungal pathogen that can cause life-threatening infections. Infections are opportunistic in nature and typically occur in immunocompromised patients, with AIDS patients being at greatest risk. Cryptococcosis is usually manifested as meningitis, which is often treated as incurable in AIDS patients and can require life-long antifungal therapy. Infections are worldwide with approximately 90- 95% of all infections being caused by serotype A strains. The importance of this fungus as a pathogen resulted in the solicitation and funding of a genome-sequencing project. The strain that was chosen, however, was a serotype D strain, which causes less than 10% of all infections. This strain was chosen because sexually compatible strains (designated MATalpha and MATa) exist, whereas compatible serotype A strains are not available due to the absence of a fertile MATa strain. An added significance of mating in C. neoformans is that virtually all infections are caused by one mating type (MATalpha). We have recently identified a serotype A MATa strain that is fertile and crosses efficiently with serotype A MATalpha strains, including strain H99, the standard laboratory strain for this serotype. The existence of this strain provides a powerful tool for studying C. neoformans because it will enable traditional genetic studies to be performed in serotype A strains. This proposal consists of three aims. The first aim will prepare two congenic pairs of strains that differ only in mating type. Genetic markers will be inserted into these strains to make them useful tools for future genetic and molecular studies. The second aim will test the role of mating type in virulence. By using congenic strains in these experiments, the role of information at the mating type locus in virulence can be tested independent of non mating-type information. In the last aim, the serotype A MATa mating type locus will be cloned and mapped to determine its size. Presently three out of the four mating type loci of C. neoformans var. neoformans (comprised of serotype A and D) are in various stages of characterization. Isolation of the serotype A MATa locus will complete this study, which is significant because of the role that mating type plays in virulence.