PATHOGENESIS OF ACANTHAMOEBA KERATITIS

棘阿米巴角膜炎是一种使人虚弱的角膜感染。目前，该病的诊断并不简单，治疗也存在问题，包括每小时、全天候、局部联合用药较长时间。尽管进行了积极的治疗，但复发仍有可能发生。鉴于这种疾病的破坏性和与治疗相关的问题，我们的目标是找到一种方法来识别处于危险中的个人，并为他们提供合理设计的策略来预防感染。寄生虫与宿主细胞的黏附是感染发病机制的关键第一步。在之前的资助期间，我们证明棘阿米巴表达一种甘露糖受体，该受体介导阿米巴与角膜上皮细胞的黏附。为了了解甘露糖介导的阿米巴与宿主细胞的黏附触发最终杀死宿主细胞的事件的机制，在目标1中，我们将克隆编码阿米巴甘露糖受体的cDNA，并确定甘露糖受体是否是具有调节信号转导事件的潜力的跨膜蛋白。在目标2中，我们将确定口服免疫特定的阿米巴甘露糖受体的碳水化合物识别结构域是否会导致仓鼠泪液中的抗体水平升高，如果是的话，免疫反应是否提供了对感染的保护。我们最近已经证明，在甘露糖介导的阿米巴与宿主细胞的黏附之后，一种特殊的蛋白酶P3被分泌到共培养基中。目标3中提出的研究是为了验证一种假设，即P3可能在接触依赖性事件的级联反应中发挥重要作用，这些接触依赖事件涉及阿米巴诱导的角膜上皮细胞溶解。希望这项研究有助于更好地了解棘阿米巴角膜炎的分子基础，并最终改善预防该疾病的前景。此外，这项研究将有助于对感染的一般致病机制和细胞生物学的基本了解，并因此对未来寻求预防其他病原体引起的眼部感染的研究人员有所帮助。

Acanthamoeba keratitis is a debilitating infection of the cornea. At present, diagnosis of the disease is not straightforward and treatment is problematic, consisting of hourly, around the clock, topical application of a combination of drugs for an extended period of time. Despite the aggressive treatment, recrudescence may occur. In view of the devastating nature of the disease and the problems associated with the therapy, our goals are to find a means to identify individuals who are at risk and provide them with rationally designed strategies to protect against the infection. The adhesion of the parasite to the host cells is the critical first step in the pathogenesis of infection. During the previous funding period, we demonstrated that Acanthamoebae express a mannose receptor which mediates adhesion of the amoeba to corneal epithelial cells. For an understanding of the mechanism by which the mannose-mediated adhesion of the amoeba to host cells triggers events which ultimately kill the host cells, in Aim 1, we shall clone a cDNA encoding the amoeba mannose receptor and will establish whether the mannose receptor is a transmembrane protein with potential for modulating signal transduction events. In Aim 2, we shall determine whether oral immunization of hamsters with specifically the carbohydrate recognition domain of the amoeba mannose receptor leads to an elevated antibody level in their tears, and, if so, whether the immune response provides protection against the infection. We have recently shown that subsequent to the mannose-mediated adhesion of the amoeba to host cells, a specific proteinase, P3, is secreted into the co-culture media. Studies proposed in Aim 3 are to test a hypothesis that P3 may be an important player in the cascade of contact-dependent events involved in the amoeba-induced cytolysis of corneal epithelial cells. It is hoped that this study will contribute to a better understanding of the molecular basis of Acanthamoeba keratitis and will ultimately improve the prospects of preventing the disease. In addition, this study will contribute to the basic understanding of the pathogenic mechanisms and cell biology of infections in general and as such, benefit future investigators looking to prevent ocular infections caused by other pathogens.