Babesiosis: An Emerging Infectious Threat to Transfusion Medicine

描述(申请人提供)：巴贝斯虫病是一种人畜共患病，一种通过动物传染给人的疾病。啮齿动物寄生虫微小巴贝斯虫和牛的病原体分歧巴贝斯虫是迄今为止全球报告的大多数人类感染的原因。从血液安全的角度来看，涉及巴贝斯虫的输血传播感染。在美国变得越来越有问题，每年都有越来越多的报告。因此，对这种血液传播寄生虫的研究应被视为输血医学的优先事项。我们的目的是了解分枝杆菌入侵人类红细胞的过程，最终目的是利用被发现在入侵中发挥关键作用的寄生虫分子作为诊断和血液筛查工具。我们用来研究分枝杆菌入侵人类红细胞的体外系统，允许使用分枝杆菌的活性裂殖子直接探索与寄生虫入侵人类红细胞相关的事件。寄生虫表面的分子和顶端细胞器分泌的分子在宿主/寄生虫的界面上发挥作用，如果我们要确定入侵机制中的步骤和确定新的治疗靶点，我们需要鉴定它们并确定它们的相互作用和功能。我们已经确定了这样一个假定的RBC结合配体，BD30，我们项目的重点是研究它在寄生虫入侵期间与RBC，特别是血糖素的相互作用。本研究的目的有三个：(1)鉴定血糖蛋白A(GPA)和血糖蛋白B(GPB)作为裂殖子侵袭的RBC受体；(2)确认bd30是血糖素A(GPA)和/或血糖蛋白B(GPB)结合血糖蛋白A(GPA)和/或血糖蛋白B(GPB)的BD30配基，并鉴定BD30在寄生虫中的功能；(3)评价GPA和/或GPB和BD17相互作用在裂殖子侵袭中的功能意义。提出的方法包括用特定的酶处理RBC、缺乏确定的RBC抗原的突变细胞和使用抗体和竞争肽来抑制侵袭试验；在侵袭试验中使用天然和重组的bd30配体蛋白和抗bd30的抗体进行红细胞结合分析，以及建议的基因缺失来研究其功能。因此，该项目的主要目标是阐明分枝杆菌裂殖子进入红细胞的分子机制。预计本提案中详细介绍的研究将产生诊断、流行病学以及治疗和预防人类巴贝斯虫病的试剂，并协助开发筛查血液产品的产品。 公共卫生相关性：巴贝斯虫病是一种人畜共患病，是一种通过动物传染给人的疾病，也是一种重要的血液传播的人类寄生虫病。人与人之间的寄生虫传播被公认为是通过输血发生的。尽管它对输血安全构成了重大威胁，但它的研究在很大程度上被忽视了。本建议的长期目标是对分枝杆菌寄生虫的红细胞入侵进行详细的机制了解，以便开发治疗感染的新疗法和筛查献血者巴贝斯虫感染的有效策略。我们正在专门研究红细胞受体、血糖素A和B与结合它们的巴贝斯虫分子之间的相互作用，以便我们能够定义入侵机制中的步骤。认识到巴贝斯虫病是一个日益严重的血液安全威胁，我们有兴趣开发可行的干预措施，以检测和阻止这些病原体通过输血传播。

DESCRIPTION (provided by applicant): Babesiosis is a zoonosis, a disease communicable from animals to man. The rodent parasite, Babesia microti and the bovine pathogen, Babesia divergens are responsible for most of the human infections that have been reported to date, globally. From a blood safety perspective, transfusion-transmitted infections involving Babesia spp. have become increasingly problematic in the USA, with progressively more reported each year. Therefore the study of this blood-borne parasite should be considered as a priority for transfusion medicine. Our purpose is to understand the invasion process of B. divergens into the human red blood cell (RBC), with the ultimate aim of exploiting parasite molecules found to play key roles in invasion as diagnostic and blood screening tools. The in-vitro system that we use for studying invasion of the human red cell by B. divergens, permits direct exploration of the events associated with parasite invasion of the human RBC, using viable merozoites of B. divergens. Molecules on the surface of the parasite and those secreted by apical organelles function at the host/parasite interface, and we need to identify them and determine their interactions and function, if we are to define the steps in the invasion mechanism and identify new therapeutic targets. We have identified one such putative RBC binding ligand, Bd30 and the focus of our project is the study of its interaction with the RBC, specifically the glycophorins, during parasite invasion. There are three specific aims in this proposal (1) To characterize glycophorin A (GPA) and glycophorin B (GPB) as RBC receptors for B. divergens invasion (2) To validate Bd30 as the B. divergens ligand that binds glycophorin A (GPA) and/or glycophorin B (GPB) and to characterize Bd30 in the parasite and (3) To evaluate the functional significance of the interaction between GPA and/or GPB and Bd17 in merozoite invasion. Methodology that is proposed includes inhibition of invasion assays using specific enzyme treatments of the RBC, mutant cells lacking defined RBC antigens and the use of antibodies and competitor peptides; erythrocyte binding assays using native and recombinant Bd30 ligand protein and antibodies against Bd30 in invasion assays, as well as proposed gene deletion to study its function. Thus, the major goal of the project is to elucidate the molecular mechanisms involved in the entry of B. divergens merozoites into the erythrocyte. It is anticipated that studies detailed in this proposal will result in reagents for diagnosis, epidemiology and treatment and prevention of human babesiosis, and assist in developing products to screen blood products. PUBLIC HEALTH RELEVANCE: Babesiosis is a zoonosis, a disease communicable from animals to man and an important blood-borne human parasitic infection. Human to human transmission of the parasite is well recognized to occur through blood transfusion. Despite being a significant threat to the safety of blood transfusions, its study has largely been neglected. The long term objective of the present proposal is to develop a detailed mechanistic understanding of the erythrocytic invasion of the B. divergens parasite in order to develop novel therapies for treating the infection and effective strategies for screening of blood donors for babesia infection. We are specifically looking at interactions between the RBC receptors, glycophorins A and B and the Babesia molecules that bind to them so that we can define the steps in the invasion mechanism. Recognizing that Babesia is an expanding blood safety threat we are interested in the development of viable interventions to detect and halt transmission of these pathogens via blood transfusions.