MODELS OF P CARINII INFECTION: SP-A AND SP-D NULL MICE

尽管在诊断、治疗和预防方面取得了进展，但卡氏肺孢子虫肺炎(PCP)仍然是HIV感染患者发病率和死亡率的主要原因。这种疾病是由一种神秘的病原体引起的，由于难以在体外培养这种生物，其基本生物学仍然知之甚少。因此，动物模型仍然是研究PCP发病机制的主要方法。尽管在对卡氏肺孢子虫感染的即时反应中保护性免疫的定义已经取得了进展，但关于这种感染的发病机制的研究仍然存在一个极其重要的差距，其核心是无法量化体内致病的各个步骤。表面活性蛋白A(SP-A)和表面活性蛋白D(SP-D)是胶原样凝集素，在远端呼吸道和肺泡中高表达。这两种蛋白都被证明与卡氏肺孢子虫结合并介导其与肺泡巨噬细胞的附着，并调节T细胞群的细胞因子分泌。近年来，SP-A和SP-D基因敲除小鼠的研究进展表明，这些蛋白在肺局部宿主防御和调节肺炎性反应中发挥重要作用。我们假设SP-A和SP-D：a)增加卡氏肺孢子虫从肺泡腔的清除；b)在PCP过程中调节促炎和抗炎反应之间的平衡。我们建议利用最近发展起来的SP-A和SP-D基因敲除小鼠作为卡氏肺孢子虫感染的新模型，以确定集合素在宿主防御PCP中的作用。其具体目的是：1)利用SP-A和SP-D基因敲除小鼠，确定肺集合素(SP-A和SP-D)在体内卡氏肺吸虫感染建立和清除中的作用；2)在SP-A和SP-D缺陷模型中表征宿主对卡氏肺孢子虫的免疫反应；3)表征表面活性蛋白基因敲除小鼠肺炎发生发展过程中表面活性物质组成和功能的变化；4)确定外源SP-A和/或SP-D替代对卡氏肺孢子虫感染的清除作用。该项目将结合几个已建立的专题研究计划的要素，以产生一项全面的调查建议，其中包括：1)一名具有表面活性物质生物学所有主要方面专业知识的首席调查员；2)公认为免疫缺陷小鼠PCP模型和表面活性蛋白基因敲除小鼠的权威的顾问。这些研究结果将扩大我们对卡氏肺孢子虫感染发病机制的理解。

Despite advances in diagnosis, therapy, and prophylaxis, Pneumocystis carinii pneumonia (PCP) remains a leading cause of morbidity and mortality in patients with HIV infection. The disease is caused by an enigmatic pathogen whose basic biology remains poorly understood because of difficulty in culturing the organism in vitro. Thus, animal models remain a mainstay of investigation into the pathogenesis of PCP. Although progress has been made in the definition of protective immunity in the immediate response to P carinii infection, an extremely important gap remains related to studies of the pathogenesis of this infection which centers around an inability to quantify various steps in pathogenesis in vivo. Surfactant protein A (SP-A) and surfactant protein D (SP-D) are collagen like lectins (collectins) which are highly expressed in the distal airways and alveolus. Both proteins have been shown to bind to and mediate the attachment of P carinii to the alveolar macrophage and to modulate cytokine elaboration by T-cell populations. Recent development of both SP-A and SP-D knockout mice has begun to implicate important roles for these proteins in local lung host defense and in modulation of the pulmonary inflammatory response. We hypothesize that SP-A and SP-D: a) Augment clearance of P. carinii from the alveolar space; b) Moderate a balance between pro- and anti-inflammatory responses which occurs during PCP. We propose to utilize the recently developed SP-A and SP-D knockout mice as new models of P. carinii infection to define the role of the collectins in host defense against PCP. The specific aims are: 1) Using SP-A and SP-D knockout mice, determine the role of the lung collectins (SP-A, SP-D) in the establishment and clearance of P. carinii infection in vivo; 2) Characterize the host immune response to P. carinii in SP-A and SP-D deficient models.; 3) Characterize changes in surfactant composition and function during development and progression of PC pneumonia in surfactant protein knockout mice; 4) Determine the effect of exogenous replacement of SP-A and/or SP-D on the clearance of P. carinii infection. The project will combine elements of several established thematic research programs to yield a comprehensive investigative proposal including: 1) A Principal Investigator with expertise in all major aspects of surfactant biology 2) Consultants recognized as authorities on immunocompromised mouse models of PCP and in generation of surfactant protein knockout mice. Results from these studies will extend our understanding of the pathogenesis of P. carinii infection.