STAGE SPECIFIC GENE EXPRESSION IN TOXOPLASMA GONDII

原生动物病原体弓形虫是一种重要的疾病原因 在人类和家畜中。T.弓形虫可引起急性， 接受免疫抑制治疗的患者中的致命机会性感染 疗法 先前潜伏感染的艾滋病患者可能会发展为 弓形体脑炎是发病的重要原因， mortality. IN中间寄主T.弓形虫有两种形式， 速殖子和缓殖子。在感染的急性期， 侵入性速殖子形式占主导地位， 杀伤性 速殖子转变为包裹在 组织囊肿，持续在潜伏感染，即使在健康的 正在接受当前抗弓形虫药物治疗的个体和患者。 囊肿破裂导致的先前潜伏感染的再激活 会导致速殖子重新出现 弓形虫病是艾滋病中活动性弓形虫病的主要原因 患者 由于组织囊肿参与维持潜伏的 感染和寄生虫的来源，在重新激活，这是重要的 研究速殖子与 缓殖子期 为了研究阶段特异性基因的调控， 在转化过程中表达，克隆了几个阶段特异性基因 包括两个与乳酸脱氢酶（LDH）具有很强同源性的， 其他物种。 一个LDH基因是缓殖子特异性的，另一个是 玻璃陨石特有的。 研究阶段特异性的机制， 调节这些LDH基因，将采取以下方法：（1） 将在培养期间研究LDH多肽的表达谱。 使用体外模型的缓殖子和速殖子的相互转化 分化，（2）LDH 2基因的转录活性将是 在阶段转换期间研究，（3）启动子和DNA序列结构域 负责发育转录激活和调节 将通过缺失和突变分析来鉴定LDH 2基因， （4）缓殖子特异性的功能意义 将通过基因突变产生无效突变体来检查表达的LDH同工型 更换. 缓殖子LDH基因的基因置换研究将 以确定其对囊肿发育的重要性。 LDH启动子中DNA调控结构域的表征 参与其发展。 DNA调控的表征 LDH启动子中参与其发育表达的结构域 可能会导致这些结构域结合因子的分离。 这些 阶段特异性基因表达的研究可能会导致鉴定 旨在阻断囊肿的抗弓形虫药物设计的潜在目标 发展或复苏。

The protozoan pathogen Toxoplasma gondii is a significant cause of disease in humans and in domestic animals. T. gondii can cause acute and often fatal opportunistic infection in patients undergoing immunosuppressive therapy. AIDS patients with a previously latent infection may develop toxoplasmic encephalitis which is a significant cause of morbidity and mortality. IN intermediate host, T. gondii exists in two forms, the tachyzoite and the bradyzoite. During the acute phase of infection, the invasive tachyzoite form predominates and is responsible for tissue destruction. Tachyzoites switch to the bradyzoite form enclosed within tissue cysts which persist during the latent infection even in healthy individuals and patients undergoing current anti-T gondii drug therapies. Reactivation of a previously latent infection resulting from cyst rupture in the brain or other tissue leads to the reemergence of the tachyzoite form and is thought to be the major cause of active toxoplasmosis in AIDS patients. Since tissue cysts are involved in the maintenance of the latent infection and are the source of parasites in reactivation, it is important to study the mechanisms of interconversion between the tachyzoite and bradyzoite stages. In order to study the regulation of stage specific gene expression during conversion, several stage-specific genes were cloned including two with strong homology to lactate dehydrogenase (LDH) from other species. One LDH gene is bradyzoite specific and the other is tachzoite specific. TO study the mechanisms of the stage-specific regulation of these LDH genes, the following approaches will be taken : (1) The profiles of expression of LDH polypeptide will be studied during interconversion of bradyzoites and tachyzoites using in vitro models of differentiation, (2) the transcriptional activity of the LDH2 gene will be studied during stage conversion, (3) the promoter and DNA sequence domains responsible for the developmental transcriptional activation and regulation of the LDH2 gene will be identified by deletional and mutational analysis, and (4) the functional significance of the bradyzoite-specifically expressed LDH isoform will be examined by generating null mutants by gene replacement. Gene replacement studies of the bradyzoite LDH gene will performed to determine its importance to cyst development. Characterization of the DNA regulatory domains in the LDH promoters involved in their development. Characterization of the DNA regulatory domains in the LDH promoters involved in their developmental expression might lead to the isolation of the factors that bind these domains. These studies of stage-specific gene expression might lead to the identification of potential target for anti-T gondii drug design aimed at blocking cyst development or reactivation.