对两种致病真菌马儿尼菲青霉菌和烟曲霉的致病机理研究

Penicillium marneffei and Aspergillus fumigatus are pathogenic fungi belonging to two closely related genera. P. marneffei is the most important thermal dimorphic fungus causing respiratory, skin and systemic mycosis in HIV positive patients in China and Southeast Asia. A. fumigatus is the cause of invasive aspergillosis, the most globally important and fatal mold infections in immune-compromised patients with cancer, AIDS, borne marrow and solid organ transplant. Despite of their medical importance, little is known about the pathogenesis of these two pathogens. The diagnosis and prevention of P. marneffei and A. fumigatus infections are difficult and the mortality of their infections is as high as 50%. During the search for a suitable diagnosis method, a cell wall protein Mp1p was identified in all life states of P. marneffei which is now used as a diagnosis marker for P. marneffei infection. Subsequently, the homologue proteins in A. fumigatus (AFMP) were also identified and were used in serological diagnosis, too. Furthermore, MP1p based DNA vaccine and knock-down of AFMP can protect mice challenged with P. marneffei and A. fumigatus, respectively, indicating that Mp1p and AFMP might be the virulence factors for these two pathogens and thus a potential drug target for treatment. Our preliminary data show that both Mp1p and its homologue AFMP can bind arachidonic acid, the precursor of several lipid mediators for initiating local inflammatory reactions, indicating that these two pathogens may reduce hosts' immune defense through depletion of the pro-inflammatory lipid by secretion of lipid binding proteins. To further characterize the virulence potential of Mp1p and AFMP, we propose to study the interactions between the proteins and pro-inflammatory lipids through biochemical, biophysical, structural and cellular assays.

马尔尼菲青霉菌和烟曲霉是两种致病真菌，能够引起呼吸系统，皮肤以及系统性的真菌病，在全球范围内都是免疫力低下病人重要的感染源。尽管这两种真菌在医学上占有重要地位，对于它们的致病机理却知之甚少，对这两种真菌感染的诊断和预防也比较困难，感染的致死率高达50%。最近的研究发现，这两种真菌分泌的一类细胞壁蛋白不仅可以用作诊断的标签，而且，基于此类蛋白的核酸疫苗和基因敲除能够保护感染了这两种真菌的实验小鼠，暗示此类胞壁蛋白可能是这两种真菌的致病因子和潜在的治疗靶点。我们的初步分析显示此类蛋白能够结合花生四烯酸，而花生四烯酸是几种重要的激发局部免疫反应的脂类分子的前体。这就暗示这两种病原菌可能通过分泌此类蛋白来清除激发免疫反应的脂类分子，从而抑制宿主的免疫反应。为了进一步研究这两种真菌的致病机制，我们将通过生物化学，生物物理，结构生物学以及细胞生物学的方法来研究这类胞壁蛋白与脂类免疫激活分子的相互作用。

马尔尼菲青霉菌和烟曲霉是两种致病真菌，能够引起呼吸系统，皮肤以及系统性的真菌病，在全球范围内都是免疫力低下病人重要的感染源。尽管这两种真菌在医学上占有重要地位，对于它们的致病机理却知之甚少，对这两种真菌感染的诊断和预防也比较困难，感染的致死率高达50%。最近的研究发现，这两种真菌分泌的一类细胞壁蛋白不仅可以用作诊断的标签，而且，基于此类蛋白的核酸疫苗和基因敲除能够保护感染了这两种真菌的实验小鼠，暗示此类胞壁蛋白可能是这两种真菌的致病因子和潜在的治疗靶点。我们的分析显示此类蛋白能够结合花生四烯酸，而花生四烯酸是几种重要的激发局部免疫反应的脂类分子的前体。这就暗示这两种病原菌可能通过分泌此类蛋白来清除激发免疫反应的脂类分子，从而抑制宿主的免疫反应。我们通过生物化学，生物物理，结构生物学以及细胞生物学的方法来研究这类胞壁蛋白与脂类免疫激活分子的相互作用。我们发现，作为毒力因子的分泌型甘露糖蛋白Mp1p是通过经由LBD2结构域中发现的长疏水中心腔来高度结合花生四烯酸，从而隔离了重要的促炎症信号脂质。并且我们发现，在马尔尼菲青霉感染的J774巨噬细胞中，花生四烯酸的下游代谢物和细胞因子白细胞介素-6和肿瘤坏死因子α有所下调。鉴于Mp1p-LBD2同系物在其他真菌病原体中被鉴定，我们预计这种新型的脂肪酸结合蛋白螯合关键促炎脂质介质。在关于烟曲霉如何侵染宿主细胞并且得以存活的机制研究中发现，一种分泌性蛋白叫做Afmp4p是通过形成具有长疏水性中心腔的五螺旋束单体结构来高度结合花生四烯酸。核磁共振滴定分析，等温滴定量热分析，X射线晶体结构，下拉和免疫沉淀分析等一系列实验都支持该结论；并且细胞因子IL-6和TNF-α均在烟曲霉感染的J774巨噬细胞中下调。因此与Mp1p类似，Afmp4p应该是靶向关键促炎信号脂质以逃避宿主先天免疫防御的新型脂质结合蛋白之一。