Structure and Expression of Pneumocystis Antigen Genes

描述(申请人提供)：肺孢子虫肺炎是艾滋病患者和其他免疫功能受损的人的严重问题。这种疾病是由一种不寻常的真菌引起的，这种真菌在人外几乎不会繁殖。因此，对肺孢子虫生物学的研究主要依赖于卡氏肺孢子虫和小鼠肺孢子虫，它们分别生活在大鼠和小鼠身上。在对卡氏肺孢子虫和穆里纳肺孢子虫的研究中，至少有一个基因家族(MSG)与抗原性变异有关。在这一应用中，我们建议对啮齿动物肺孢子虫的基因家族(MSG、PRT、MSR)进行结构和功能研究。这些研究的总体目标是确定肺孢子虫基因家族是否起作用，使该属的成员能够寄生具有免疫能力的宿主。目标1将使用来自卡氏肺孢子虫的基因组数据来确定基因家族编码的蛋白质在哪里发生变化，以及这种变化是如何演变的。演绎进化模式将使我们能够推断出一般的功能。目的2将利用基因组信息来研究卡氏肺孢子虫MSG家族的表达，这一过程需要在唯一的表达部位进行重组，从而导致表达基因的序列发生变化。大量证据表明，基因转换会导致味精表达拷贝的变异。目标2将研究这种可能性和其他可能性。目标3将确定在P.Murina的DC基因座上发生重组的频率。这些研究将建立小鼠作为研究肺孢子虫抗原变异的模型，并为目标4中描述的研究奠定基础，该研究将检验适应性免疫反应可以影响驻留在表达部位的味精基因序列的变异程度的想法。

DESCRIPTION (provided by applicant): Pneumocystis pneumonia is a serious problem for AIDS patients and other immunocompromised individuals. This illness is caused by an unusual fungus (Pneumocystis jirovecii) that proliferates little when outside of a human being. Therefore, studies on the biology of Pneumocystis have relied principally upon P. carinii and P. murina, which inhabit rats and mice, respectively. Human Pneumocystis has at least one gene family (MSG) that has been implicated in antigenic variation in studies on P. carinii and P. murina. In this application, we propose structural and functional studies on gene families (MSG, PRT, MSR) in rodent Pneumocystis species. The overall goal of these studies is to determine if Pneumocystis gene families function to allow members of this genus to parasitize an immunocompetent host. Aim 1 will employ genomic data from P. carinii to determine where the proteins encoded by a gene family vary, and how this variability evolved. Deducing the mode of evolution will allow us to infer general function. Aim 2 will use genomic information to investigate expression of the P. carinii MSG family, a process that entails recombination at a unique expression site to cause a change in the sequence of the expressed gene. The bulk of the evidence suggests that gene conversion creates variation in the expressed copy of MSG. Aim 2 will examine this and other possibilities. Aim 3 will determine how often recombination occurs at the DCS locus of P. murina. These studies will both establish mice as a model for studying antigen variation in Pneumocystis, and set the stage for studies described in Aim 4, which will test the idea that the adaptive immune response can influence the degree of variation in MSG gene sequences residing at the expression site.