STRUCTURE AND EXPRESSION OF PNEUMOCYSTIS ANTIGEN GENES

提出的工作重点是MSG，它是致病真菌P.carinii的一组可变表面抗原。像味精这样的表面抗原是最有意义的，因为它们在宿主-病原体界面起作用。某些原生动物和细菌利用复杂的遗传系统在其表面产生多样性，说明了这种界面对病原微生物的重要性。卡氏假单胞菌的味精基因似乎赋予了这种真菌类似的改变其表面的能力。这项研究提出的长期目标是描述卡氏肺孢子虫的抗原变异，了解控制它的遗传机制，并研究抗原变异与宿主-病原体相互作用之间的关系。实验主要集中在大鼠卡氏肺孢子虫上，因为它很容易驯服。对人卡氏肺孢子虫的研究也提出了建议。有待检验的假设包括：(I)卡氏肺孢子虫利用DNA重组改变附着在一个独特表达部位的味精基因。(Ii)改变这一基因会导致细胞表面的味精发生变化。(Iii)感染人类的卡氏肺孢子虫的味精表达系统与感染老鼠的卡氏肺孢子虫的味精表达系统相似。本研究有以下四个具体目的：1.确定抗原变异的遗传基础。2.分析大鼠接种模型后谷氨酰胺变化的动态和本质。3：确定宿主免疫反应是否影响抗原变异的频率或性质。4.对人卡氏肺孢子虫的味精系统进行分析。这些目标将通过自然感染的大鼠和接种了低剂量卡氏肺孢子虫的大鼠来实现。人类卡氏肺孢子虫将从患者那里获得。分子遗传学和免疫组织化学工具将用于研究味精基因和蛋白质的表达。

The work proposed is focused on MSG, which is a group of variable surface antigens of the pathogenic fungus, P. carinii. Surface antigens such as MSG are of fundamental interest because they function at the host-pathogen interface. The importance of this interface to pathogenic microbes is illustrated by the complex genetic systems used by certain protozoa and bacteria to generate diversity on their surface. P. carinii MSG genes appear to endow this fungus with a similar capacity to vary its surface. The broad, long-term objectives of the research proposed are to characterize antigenic variation in P. carinii, to understand the genetic mechanism that controls it, and to study the relationship between antigenic variation and host-pathogen interactions. The experiments focus primarily on rat P. carinii because it is tractable. Studies on human P. carinii are also proposed. Hypotheses to be tested include (i) P. carinii use DNA recombination to change the MSG gene that is attached to a unique expression site. (ii) Changing this gene leads to a change in the MSG on the cell surface. (iii) P. carinii that infects humans has an MSG expression system similar to that in P.carinii that infects rats. The proposed research has the following four Specific Aims: 1. Determine the genetic basis for antigenic variation. 2. Analyze the dynamics and nature of MSG variation in the inoculated rat model. 3: Determine if the host immune response influences the frequency or nature of antigenic variation. 4. Analyze the MSG system in human P. carinii. These Aims will be addressed using rats that are naturally infected, and rats that have been inoculated with a low dose of P. carinii. Human P. carinii will be obtained from patients. Molecular genetic and immunohistochemical tools will be used to study expression of MSG genes and proteins.