PATHOGENESIS OF ACANTHAMOEBA KERATITIS

阿米巴角膜炎是一种使角膜衰弱的感染。目前，该疾病的诊断并不简单，治疗也存在问题，包括每小时、昼夜不停地局部应用药物组合持续很长一段时间。 尽管积极治疗，复发可能发生。 鉴于该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风险中的个体，并为他们提供合理设计的策略来保护免受感染。寄生虫与宿主细胞的粘附是感染发病机制中关键的第一步。 在之前的资助期间，我们证明了阿米巴原虫表达一种甘露糖受体，该受体介导阿米巴原虫与角膜上皮细胞的粘附。 为了理解阿米巴对宿主细胞的甘露糖介导的粘附触发最终杀死宿主细胞的事件的机制，在目的1中，我们将克隆编码阿米巴甘露糖受体的cDNA，并将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，我们将确定用阿米巴甘露糖受体的特异性碳水化合物识别结构域口服免疫仓鼠是否导致其泪液中抗体水平升高，如果是，免疫应答是否提供针对感染的保护。 我们最近表明，继甘露糖介导的阿米巴粘附到宿主细胞，一个特定的蛋白酶，P3，分泌到共培养基。 目的3中提出的研究是为了检验一个假设，即P3可能是阿米巴诱导的角膜上皮细胞溶解中涉及的接触依赖性事件级联中的重要参与者。希望这项研究将有助于更好地了解阿米巴角膜炎的分子基础，并最终改善预防这种疾病的前景。 此外，这项研究将有助于对一般感染的致病机制和细胞生物学的基本了解，因此，有利于未来的研究人员预防其他病原体引起的眼部感染。

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.