Functional Studies of Toxoplasma gondii AMA1 and AMA2

描述（由申请方提供）：顶复门寄生虫，如弓形虫病的病原体刚地弓形虫和严重人类疟疾的病原体恶性疟原虫，是专性细胞内病原体。宿主细胞侵入、寄生虫增殖和宿主细胞裂解的重复循环是这些病原体致病性的核心。 寄生虫，但对宿主细胞入侵的机制或介导这一过程的寄生虫蛋白知之甚少。其中一种蛋白质是AMA1。AMA1在顶复门中是保守的，疟原虫AMA1是领先的疟疾疫苗候选者。AMA1在与宿主细胞相互作用期间释放到寄生虫表面上，在那里它被认为在宿主细胞入侵中发挥重要作用，尽管尚未确定。霸王弓形虫AMA1的同源基因TgAMA1最近已被鉴定，并在弓形虫中建立了一个新的条件基因表达系统。刚地弓形虫已经能够产生其中可以实验性地操纵TgAMA1表达的寄生虫系。这些寄生虫中TgAMAl表达的降低导致其侵袭性的显著降低。条件性敲除寄生虫为研究模型AMA1蛋白的功能提供了前所未有的机会。具体目标1将使用条件性敲低寄生虫和丰富的试验，可在T。以确定TgAMA1在弓形虫入侵中所起的特异性作用。特异性目的2将探索在入侵期间从寄生虫表面蛋白水解切割和释放TgAMAl的功能意义。特异性目标3将表征和确定TgAMA2的功能，TgAMA2是一种AMA1样序列，也在T.弓形虫速殖子 T.弓形虫在先天性感染的胎儿和免疫功能低下的人中引起危及生命的疾病，包括患有AIDS或霍奇金斯病的人，以及正在接受免疫抑制或癌症化疗的人。鉴于AMA1在侵袭中的明显重要性以及侵袭在发病机制中的中心作用，更好地理解AMA1和AMA1相关蛋白的功能可能有助于开发新的基于疫苗或化疗的方法来预防或控制T.弓形虫和其他顶复门寄生虫。

DESCRIPTION (provided by the applicant): Apicomplexan parasites such as Toxoplasma gondii, the causative agent of toxoplasmosis, and Plasmodium falciparum, the causative agent of severe human malaria, are obligate intracellular pathogens. Repeated cycles of host cell invasion, parasite multiplication and host cell lysis are central to the pathogenicity of these parasites, yet little is known about the mechanisms of host cell invasion or the parasite proteins that mediate the process. One protein that has been the focus of intense interest is AMA1. AMA1 is conserved among apicomplexans, and Plasmodium AMA1 is a leading malaria vaccine candidate. AMA1 is released onto the parasite surface during interaction with host cells, where it is thought to play an essential - though still undefined - role in host cell invasion. The T. gondii homolog of AMA1 (TgAMAl) has recently been identified, and a new system for conditional gene expression in T. gondii has enabled the creation of a parasite line in which expression of TgAMAl can be experimentally manipulated. A decrease in TgAMAl expression in these parasites causes a significant decrease in their invasiveness. The conditional knockdown parasites provide an unprecedented opportunity to study the function of a model AMA1 protein. Specific Aim 1 will use the conditional knockdown parasites and the wealth of assays available in T. gondii to deter mine the specific role played by TgAMAl in invasion. Specific Aim 2 will explore the functional significance of proteolytic cleavage and release of TgAMAl from the parasite surface during invasion. Specific Aim 3 will characterize and determine the function of TgAMA2, an AMAl-like sequence that is also expressed in T. gondii tachyzoites. T. gondii causes life-threatening disease in the congenitally-infected fetus and in immunocompromised persons, including those with AIDS or Hodgkins' disease, and those undergoing immunosuppressive or cancer chemotherapy. Given the apparent importance of AMA1 in invasion and the central role invasion plays in pathogenesis, a greater understanding of the function of AMA1 and AMA1-related proteins will likely contribute to the development of new vaccine-based or chemotherapeutic approaches to preventing or controlling infection by T. gondii and other apicomplexan parasites.