Modeling the spectrum of HIT pathobiology

描述（由申请人提供）：这项小额资助申请的目的是为肝素诱导的血小板减少症（HIT）的研究开发一种研究方法。HIT是由对抗凝药物肝素的过敏反应引起的血栓前障碍。HIT是由针对血小板蛋白、血小板因子4（PF 4）和肝素（H）的抗体引起的。由于PF 4/H抗体可在患者中引发危及生命的血栓性并发症，因此疾病发病机制的实验研究依赖于动物模型。已经开发了两种不同的动物模型来研究HIT;一种模型研究HIT的血栓并发症（小鼠HIT模型），另一种是我们实验室开发的小鼠免疫模型，用于研究PF 4/H免疫反应。在此R 03申请中，我们建议开发一种用于研究人类HIT发病机制的综合小鼠模型。基于初步研究，我们假设PF 4/H抗体的致病性由三个因素的汇合决定，即循环抗原（PF 4/H复合物）、PF 4/H抗体和活化血小板Fc RIIA受体。我们建议使用依赖于Fc RIIA表达的存在（单转基因模型）和hPF 4表达或不表达（双转基因模型）的两种方法之一来测试该假设。在第一种方法中，我们将在单一转基因模型（表达hFc RIIA的小鼠）中诱导PF 4/H抗体，目的是检查抗原负荷、抗体滴度和Fc RII表达的影响。在第二种方法中，我们希望使用表达人（h）PF 4和hFc RIIA的双转基因小鼠开发“人源化”鼠模型，以检查hPF 4水平和hFcR表达对免疫应答和疾病表达的影响。在追求这一小笔研究经费，我们希望这些优化的小鼠模型将有助于未来的致病性HIT抗体的进化机制的调查。 公共卫生相关性：这些研究将研究最常见的药物引起的过敏，这与血液稀释剂药物肝素发生。这种过敏称为肝素诱导的血小板减少症，与危及生命的凝血并发症有关。我们建议开发模型来研究这种危及生命的过敏反应如何在人类中发生。

DESCRIPTION (provided by applicant): The goal of this small grant application is to develop a research methodology for studies of Heparin-Induced Thrombocytopenia (HIT). HIT is a prothrombotic disorder caused by an allergic response to the anticoagulant drug, heparin. HIT is caused by antibodies directed towards a platelet protein, Platelet Factor 4 (PF4) and heparin (H). Because PF4/H antibodies can elicit life-threatening thrombotic complications in patients, experimental studies of disease pathogenesis have relied on animal models. Two distinct animal models have been developed to study HIT; one model studies thrombotic complications of HIT (murine HIT model) and the other, a murine immunization model developed by our lab to study the PF4/H immune response. In this R03 application, we propose to develop an integrated murine model for studies of human HIT pathogenesis. Based on preliminary studies, we hypothesize that pathogenicity of PF4/H antibodies is determined by the confluence of three factors, circulating antigen (PF4/H complexes), PF4/H Abs and activating platelet Fc RIIA receptors. We propose to test this hypothesis using one of two approaches relying on the presence of Fc RIIA expression (single transgenic model) with or without expression of hPF4 (double transgenic model). In the first approach, we will induce PF4/H antibodies in a single transgenic model (mice expressing hFc RIIA) with the goal of examining effects of antigen load, antibody titer and Fc RII expression. In the second approach, we wish to develop a "humanized" murine model using double transgenic mice expressing human (h)PF4 and hFc RIIA to examine the effects of hPF4 levels and hFcR expression on the immune response and disease expression. In pursuing this small research grant, we hope that these optimized murine models will facilitate future investigations on the mechanisms underlying evolution of pathogenic HIT antibodies. PUBLIC HEALTH RELEVANCE: These studies will study the most common drug-induced allergy, which occur with the blood thinner medication heparin. This allergy, called Heparin-Induced Thrombocytopenia is associated with life-threatening clotting complications. We propose to develop models for studying how this life-threatening allergic reaction happens in humans.