Chromosome copy number variation and AIDS-associated cryptococcosis

描述（由申请人提供）：真菌病原体新型隐球菌（Cryptococcus neoformans）引起的危及生命的感染在艾滋病患者中发病率很高，导致脑膜炎，因此这种真菌是全球4000万艾滋病毒感染者的主要威胁。此外，最近出现了相关物种加蒂梭菌对免疫正常人群的威胁。这些真菌引起的感染很难治疗，因为病原体在体内持续存在，通常需要维持患者终身抗真菌治疗以防止复发。很可能病原体的持久性涉及对宿主环境的特定适应，这可能使真菌能够承受免疫反应并抵抗治疗干预。众所周知，感染过程中的病原体变异可通过影响毒力因子表达、耐药性和逃避免疫反应对疾病结局产生重大影响。我们已经发现了一种新的C.新生的基因组变异机制，可能有助于免疫功能低下的人的疾病结果。具体来说，我们发现从一名艾滋病患者身上分离出的临床新生芽孢杆菌显示出13号染色体的拷贝数变异，这与毒力因子黑色素的可变表达有关。也就是说，变体中黑色素产生的损失与13号染色体的拷贝数变异有关，我们假设拷贝数变异具有不同的毒力特性。我们提出探索性工作的第一个目的是通过在隐球菌病小鼠模型中检测变异，确定13号染色体拷贝数变异是否与新生隐球菌的毒力有关。我们还将确定病原体在宿主中的生长是否影响13号染色体拷贝数变化的频率。我们的第二个目标是通过检查来自艾滋病患者和环境来源的其他菌株，对所有染色体的拷贝数变异建立更彻底的了解。我们还将使用现有的样本来检测从感染艾滋病患者的脑脊液中直接分离的新型梭状细胞的DNA。这项工作的结果将提供在感染过程中对新生梭菌变异的更深入的了解，并有助于制定对抗真菌感染的新策略的长期目标。公共卫生相关性：该项目的相关性来自于控制因艾滋病或免疫抑制治疗导致免疫系统受损的人类真菌感染的迫切需要。4 000万或更多感染艾滋病毒的人特别容易患真菌病。拟议的研究将专门检查真菌病原体在感染过程中改变其遗传组成的能力。病原体变异可能导致感染期间的持续性和治疗失败。

DESCRIPTION (provided by applicant): The fungal pathogen Cryptococcus neoformans causes a high incidence of life-threatening infections leading to meningitis in AIDS patients, and this fungus is therefore a major threat to the > 40 million people worldwide who are infected with HIV. In addition, the related species C. gattii has recently emerged as threat to immunocompetent people. The infections caused by these fungi are difficult to treat because the pathogens persist in the body, and it is often necessary to maintain patients on life long antifungal therapy to prevent relapse. It is likely that pathogen persistence involves specific adaptations to the host environment that may allow the fungus to withstand the immune response and to resist therapeutic intervention. It is also known that pathogen variation during infection can have a major impact on disease outcome by influencing virulence factor expression, drug resistance and evasion of the immune response. We have discovered a novel mechanism of genomic variation in C. neoformans that may contribute to disease outcome in immunocompromised people. Specifically, we found that a clinical isolate of C. neoformans from an AIDS patient shows copy number variation for chromosome 13 that correlates with variable expression of the virulence factor melanin. That is, loss of melanin production in variants is associated with copy number variation for chromosome 13 and we hypothesize that copy number variants have different virulence properties. Our first aim for the proposed exploratory work is to determine whether copy number variation at chromosome 13 is relevant to the virulence of C. neoformans by testing variants in a mouse model of cryptococcosis. We will also determine whether growth of the pathogen in the host influences the frequency of copy number changes for chromosome 13. Our second aim is to establish a more thorough understanding of copy number variation for all of the chromosomes by examining additional strains from AIDS patients and from environmental sources. We will also use existing samples to examine DNA isolated directly from C. neoformans cells in the cerebral spinal fluid of infected AIDS patients. The results of this work will provide a deeper understanding of C. neoformans variation during infection and contribute to the long- term goal of developing new strategies to combat fungal infections. PUBLIC HEALTH RELEVANCE: The relevance of this project comes from the pressing need to control fungal infections in humans that have impaired immune systems due to AIDS or immunosuppressive therapy. The 40 million or more people infected with HIV are at particular risk of succumbing to fungal disease. The proposed research will specifically examine the ability of a fungal pathogen to vary its genetic make up during the infection process. Pathogen variation may contribute to persistence during infection and treatment failure.