T. Gondii: Pyrimidine Synthesis as a Chemo Target

描述(申请人提供)：弓形虫慢性感染大约30%的美国人口，并在艾滋病中引起严重威胁生命的弓形体脑炎感染。目前的药物治疗耐受性不佳，而且由于这些治疗方法对缓慢生长的缓殖子阶段几乎没有效果，潜伏的寄生虫仍然是艾滋病复发感染的来源。迫切需要针对速殖子和缓殖子阶段的更有效的治疗方法来治疗急性感染以及预防由复发的寄生虫引起的弓形虫病。我们的初步研究表明，在从头合成嘧啶的途径中，氨基甲酰磷酸合成酶II(CPSII)的中断会导致严重的尿嘧啶缺乏症，并相应地丧失寄生虫的生长和毒力。因此，嘧啶生物合成途径似乎是一个很好的干预靶点，对嘧啶获得的基础研究有可能识别新的靶点。由于所有生命阶段都需要尿苷一磷酸，我们推测，嘧啶的生物合成对于维持速殖子的快速复制以及组织囊内缓殖子的生存是必要的。我们建议结合遗传学、生物化学和细胞生物学的方法来更好地理解弓形虫从头合成嘧啶的基本生物学和挽救途径。将根据嘧啶营养缺乏症的筛选策略来确定嘧啶生物合成的抑制剂。我们研究中开发的信息和试剂将用于验证该途径中的重要药物靶点，以及验证该项目中确定的抑制剂的靶点(S)。这些研究将有助于开发治疗急性感染的新的治疗药物，并可能有助于开发能够清除慢性感染以消除艾滋病中重新激活的弓形体脑炎的第一种治疗药物。公共卫生相关性：这项研究项目将验证药物靶标，并使用基本的遗传学、生化和药物筛选方法确定弓形虫中嘧啶生物合成的抑制剂。因此，这项研究项目将加速发现新的疫苗和治疗方法，以应对艾滋病中毁灭性的机会性寄生虫感染。

DESCRIPTION (provided by applicant): Toxoplasma gondii chronically infects approximately 30% of the USA population and causes severe life-threatening Toxoplasmic encephalitis infections in AIDS. Current drug treatments are not well tolerated, and because these treatments have little effect on the slow growing bradyzoite stages, latent parasites remain as a source of recrudescing infection in AIDS. More effective therapies that can target both tachyzoite and bradyzoite stages are urgently needed to treat acute infections as well as to prevent the toxoplasmosis caused by recrudescing parasites. Our preliminary studies have demonstrated that disruption of carbamoyl phosphate synthetase II (CPSII) in the de novo pyrimidine synthesis pathway causes a severe uracil auxotrophy with a corresponding loss of parasite growth and virulence. Consequently the pyrimidine biosynthetic pathway appears to be an excellent target for intervention, and fundamental studies on pyrimidine acquisition have the potential to identify new targets. Due to the need for uridine monophosphate in all life stages, we hypothesize that pyrimidine biosynthesis is necessary to sustain rapid tachyzoite replication as well as the viability of bradyzoites within tissue cysts. We propose to use a combination of genetic, biochemical, and cell biological approaches to better understand the fundamental biology of de novo pyrimidine synthesis and salvage pathways in T. gondii. Inhibitors of pyrimidine biosynthesis will be identified based on a screening strategy of pyrimidine auxotrophy. The information and reagents developed in our studies will be used to validate significant drug targets in the pathway as well as to validate the target(s) of inhibitors identified in this project. These studies will contribute to the development of new therapeutic agents to treat acute infections and may contribute to the development of the first therapeutic agents capable of clearing chronic infection to eliminate reactivation Toxoplasmic encephalitis in AIDS. PUBLIC HEALTH RELEVANCE: This research project will validate drug targets and identify inhibitors of pyrimidine biosynthesis in Toxoplasma gondii using fundamental genetic, biochemical, and drug screening approaches. Consequently, this research project will accelerate the discovery of new vaccines and treatments for devastating opportunistic parasite infections in AIDS.