艾滋病合并新生隐球菌感染的研究进展

新生隐球菌感染是全世界艾滋病患者死亡的主要原因,尤其是在撒哈拉以南非洲地区发病率最高[1]。新生隐球菌除了容易感染HIV个体外,还易感染其他免疫功能低下的个体,如造血系统恶性肿瘤、器官移植后服用免疫抑制剂及免疫缺陷病患者。格特隐球菌主要侵犯免疫功能正常的个体,但也感染免疫功能低下患者如合并艾滋病毒的患者[2]。     

利用微卫星标记研究新生隐球菌分子流行病学

目的 研究国内隐球菌临床分离株的遗传多态性和分子流行病学.方法 选择与新生隐球菌遗传相关的9个微卫星标记,分析这9个位点从1993 ～2009年国内分离到的新生隐球菌临床株遗传背景、来源及变异程度.结果 116株被研究的隐球菌临床分离株,主要归属于3个微卫星复合物(MC2,MC3和MC12),其中大部分为MC2(103株).8株菌株属于目前为止未被国内外认识的新复合物(MC12).结论 利用微卫星DNA多态性研究新生隐球菌分子流行病学有较大的应用价值.     

新生隐球菌的生态学,流行病学,分子生物学及临床研究

在我国，对新生隐球菌已进行了较系统的研究，生态学方面，由鸽粪分离的环境株具有表型的多态性，包括新生变种的Ａ、Ｄ血清型及尿素酶阴性株，而这些多态性菌株均已在临床发现。分子生物学方面，Ｇ＋Ｃｍｏｌ％和核型已被进行分析。由ＰＦＧＥ分析所得到的有意义的信息是两个变种和５种血清型新生隐球菌株具有明显不同的核型谱。临床方面，研制的一种新的可同时检测酚氧化酶和尿素酶的培养基可用于该菌的临床鉴定。使用一种高渗培养     

新生隐球菌嗜中枢性感染机制的研究进展

新生隐球菌是临床上最重要的侵袭性病原真菌之一,可感染免疫抑制和免疫正常人群引发具有致命威胁的隐球菌性脑膜脑炎.近年来,隐球菌嗜中枢神经系统感染的机制研究取得了长足的进展,隐球菌参与侵袭中枢神经系统的相关毒力因子及多条宿主细胞应答信号通路相继被发现.     

新生隐球菌在巨噬细胞内寄生的机制

新生隐球菌是一种可以引起易感患者发生脑膜脑炎的真菌。最近的体内研究认为,新生隐球菌是一兼性的细胞内致病病原苗,这与体外研究结果是一致的。对新生隐球菌在巨噬细胞内寄生机制的研究,有助于理解它的致病机制,包括对其休眠和持续感染机制的认识,同时也有利于研究宿主有效防御反应和评价治疗药物的效果。     

新生隐球菌感染与细胞因子的相互关系

新生隐球菌是重要的条件致病真菌,可导致免疫抑制患者产生致命的新生隐球菌性脑膜炎;继而在脑部损伤部位有多种细胞因子的表达和炎症细胞的浸润,形成了一个细胞因子网络,介导一系列致病机制和防御机制的产生。为明确细胞因子与新生隐球菌在致病和防御过程中的相互作用,本文就新生隐球菌与细胞因子的关系进行综述。     

新生隐球菌的荚膜多糖合成研究进展

新生隐球菌是一重要的致病真菌,其细胞壁外层的多糖荚膜是第1个被公认的新生隐球菌毒性因子。本文总结了在荚膜生理和生化合成方面的研究进展,介绍了研究新生隐球菌荚膜合成的常用方法以及在新生隐球菌的荚膜代谢途径、生化合成酶、分泌、组装和调节这些广泛的研究领域存在的许多未解决的问题。     

肾移植与隐球菌感染

肾移植是目前开展最广泛的器官移植项目,由于免疫抑制剂及糖皮质激素的大量使用,肾移植术后的真菌感染已经成为一个重要医学课题。隐球菌病是器官移植患者常见的深部真菌感染,本文对肾移植术后发生隐球菌感染的易感因素、临床表现以及治疗和预防等方面做一论述。     

新生隐球菌毒性因子研究进展

新生隐球菌为环境中的真菌,是引起免疫损伤患者脑膜脑炎的主要病原体。新生隐球菌有毒株能够快速适应宿主环境的诸多变化,改变基因/蛋白的表达,利用多种策略在宿主防御和治疗药物的压力下可塑性地适应和生存,并在宿主不同的组织器官中顽强生存,某些免疫系统完好的宿主也不能幸免。新生隐球菌应用伪装躲避识别、逃避固有免疫和适应性免疫应答、改变细胞内转运等手段使病原体穿越天然屏障在脑中生长/持续感染。了解其中的毒性因子在持续感染中的作用,有助于揭示新生隐球菌的致病机理。     

新生隐球菌交配型的研究进展

新生隐球菌是担子菌类的真菌病原体,有明确的有性周期,有性生殖过程由两条等位基因MATα和MATa控制。MAT编码的产物包括信息素和信息素受体,丝裂原活化蛋白激酶信号级联放大系统的组成部分,还有一些在有性周期中没有明确功能的蛋白,这些蛋白都是其他真菌相应蛋白的同系物。     

Combatting the evolution of antifungal resistance in Cryptococcus neoformans

Fungal infections are a global concern and the evolution of intrinsic resistance to current antifungals presents an alarming problem. For Cryptococcus neoformans, a human fungal pathogen of primarily immunocompromised individuals, resistance toward treatment strategies demands alternative approaches. Given the prevalence of virulence factor production during cryptococcal infection, an emerging and important field of research encompasses the development of novel antivirulence therapies proposed to improve host immune responses and promote fungal clearance. To accomplish this task, information regarding the presence and role of virulence factors, the mechanisms of action within the host, and the ability to influence fungal susceptibility to antifungals is pertinent. Research into mechanisms of antifungal resistance for C. neoformans is limited but extrapolation from successful studies in other fungal species can improve our understanding of mechanisms employed by C. neoformans and suggest targeted strategies to enhance our ability to combat the pathogen. In this Review, we highlight antifungal therapy options against Cryptococcus, explore current knowledge of underlying mechanisms promoting resistance, and present new opportunities for novel and effective strategies to overcome fungal infections and reduce, or possibly even reverse, the effects of resistance evolution.     

An ectophosphatase activity in Cryptococcus neoformans

There is increasing evidence in the literature showing that fungal pathogens express biologically active ectoenzymes. The expression of surface phosphatases at the cell surface of Cryptococcus neoformans, the etiologic agent of cryptococcosis, was evaluated in the present study. Different isolates of C. neoformans express ectophosphatase activity, which is not influenced by capsule size or serotype. The cryptococcal enzyme is an acid phosphatase, inhibited by classic inhibitors of ectophosphatases, including ammonium molybdate and sodium salts of fluoride and orthovanadate. Only the inhibition of enzyme activity caused by sodium orthovanadate has been shown to be irreversible. The cryptococcal ectoenzyme is also inhibited by Zn2+ and inorganic phosphate, the final product of reactions catalyzed by phosphatases. The ectophosphatase from C. neoformans efficiently releases phosphate groups from different phosphorylated amino acids, giving a higher rate of phosphate removal when phosphothreonine is used as a substrate. Yeast cells with irreversibly inhibited ectophosphatases are less capable of adhering to animal epithelial cells than fungi fully expressing enzyme activity, suggesting that ectoenzyme expression can contribute to the pathogenesis of C. neoformans.     

中枢神经系统隐球菌感染动物模型的研究

目的 构建中枢神经系统隐球菌感染的动物模型。方法 给予小鼠脑内接种隐球菌构建中枢神经系统隐球菌感染的动物模型。小鼠被随机地分为实验组和对照组,给予实验组小鼠脑内接种隐球菌菌悬液,对照组小鼠脑内接种生理盐水。结果 从组织病理方面观察到,实验组小鼠脑组织中的蛛网膜下腔、软脑膜表面、脑实质内、侧脑室脉络丛组织内均可见隐球菌菌体,脑膜轻度增生,侧脑室轻度扩大,脉络丛血管轻度扩张充血。对照组小鼠脑组织可见侧脑室轻度扩大,蛛网膜下腔血管、脑实质内血管、脉络丛血管均有轻度扩张充血,而蛛网膜下腔、软脑膜表面、脑实质内及侧脑室和室旁均未见隐球菌浸润。从组织病理观察结果两组具有一定的对比性。结论 小鼠脑内接种隐球菌构建其中枢神经系统隐球菌感染的模型,为研究人中枢神经系统隐球菌病提供了一个工具。     

真菌miRNA的发现

microRNAs (miRNAs)在植物和动物中大量存在,但是否在真菌中存在一直是个未解之谜.本研究组在担子菌新型隐球酵母Cryptococcus neoformans中发现了miRNA.两个miRNA,miR1和miR2,长度分别是22nt和18nt,前体是70nt,和动物miRNA相近.通过报告基因,证实miRl/2具有沉默功能.真菌miRNA的发现为研究其进化、功能等提供有用知识.     

Recognition of cytoplasmic yeast antigens of Cryptococcus neoformans var. neoformans and Cryptococcus neoformans var. gattii by immune human sera

The humoral immune response of patients infected with Cryptococcus neoformans var. neoformans and C. neoformans var. gattii to cytoplasmic (non-capsular) antigens from the two varieties of Cryptococcus has been investigated. Cytoplasmic antigens from C. neoformans (one clinical isolate and one acapsular mutant of var. neoformans and two clinical isolates from var. gattii) were subject to isoelectric focusing, SDS-PAGE and Western blotting; patients sera was then used in the immunoenzyme development of the Western blots. The humoral response from the 20 patients (all HIV+) infected with var. neoformans against the var. neoformans antigens was predominantly IgG based, with a large number of bands recognised; the most commonly recognised bands were at 26, 52, 74, 100, 115 and 144 kDa. The IgM response was less pronounced and the IgA response was practically non-existent. The humoral response of the sera from the 15 patients (all but one HIV-) infected with var. gattii against var. gattii antigens was also predominantly IgG based with bands at 37, 55, 65, 74, 94 and 115 kDa being most commonly recognised. Periodate treatment of cytoplasmic antigens reduced the intensity of antigen recognition, though it did not absolutely destroy reactivity to any individual antigen. Comparison of immunodevelopment of cytoplasmic antigens from both varieties grown at 25°C and 37°C revealed that culture temperature made no differences in the number of bands recognised although there were differences in the intensity of recognition. This is the first report on the pattern of serological recognition of the non-capsular antigens from the two varieties of Cryptococcus and it identifies a number of major antigenic components.     

Unique hybrids between the fungal pathogens Cryptococcus neoformans and Cryptococcus gattii

Cryptococcus neoformans and Cryptococcus gattii are yeasts that cause meningoencephalitis, but that differ in host range and geographical distribution. Cryptococcus neoformans occurs world-wide and mostly infects immunocompromised patients, whereas C. gattii occurs mainly in (sub)tropical regions and infects healthy individuals. Anomalous C. neoformans strains were isolated from patients. These strains were found to be monokaryotic, and diploid or aneuploid. Amplified Fragment Length Polymorphism (AFLP) and sequence analyses indicated that AFLP genotypes 2 (C. neoformans) and 4 (C. gattii) were present. The strains were serologically BD. Mating- and serotype-specific PCR reactions showed that the strains were MATa-serotype D/MATalpha-serotype B. This study is the first to describe naturally occurring hybrids between C. neoformans and C. gattii.     

树突细胞与新生隐球菌

新生隐球菌( Cn) 是临床上重要的病原真菌, 树突细胞( DC) 则是最重要的抗原呈递细胞。作为宿主固有免疫和适应性免疫的联系枢纽,DC 对于识别病原、呈递抗原、诱导宿主免疫应答十分重要。许多研究证明,DC 可通过细胞表面的多种受体有效识别新生隐球菌抗原( CnAg) , 诱导宿主产生有效的细胞免疫应答。DC 本身也有一定的杀菌能力, 但DC 的不同亚群以及成熟状态对宿主的免疫防御功能有重要影响。另外, 隐球菌除具有甘露糖蛋白等主要免疫显性抗原外, 还有多种抑制机体保护性免疫应答的毒性因子。本文就近年来国内、外对两者之间复杂机制的研究进行概述。     

Cryptococcus neoformans capsule biosynthesis and regulation

The capsule is certainly the most prominent virulence factor in Cryptococcus neoformans: acapsular strains are avirulent, and capsular polysaccharides have a deleterious effect on the immune system. Until very recently, very few genes involved in capsule biosynthesis had been identified - and this despite the existence of a detailed body of work concerning the capsule's composition, structure and their regulation by environmental factors. The tremendous development of experimental tools and techniques suited to the study of C. neoformans biology together with the sequencing of three complete genomes have, over the last three years, enabled the identification of a number of proteins which participate directly in biosynthesis of the capsule or which regulate its size. Even though this knowledge is still preliminary, it gives us a clearer picture of the various events needed for biosynthesis of this fascinating structure.