A Biomaterial Approach to Attenuate Rejection of Skin Allografts

描述(由申请人提供)：在美国，每年有超过45万名烧伤患者在专门的烧伤中心接受治疗，其中近30,000人住院治疗。人体同种异体皮肤移植通常用于严重烧伤患者的临时伤口闭合，以促进快速愈合。然而，同种异体皮肤的强烈抗原性驱动着强大的抗移植物免疫反应。皮肤引流淋巴结中供者和受者白细胞之间的细胞间相互作用决定了排斥的程度。通过给予移植受者免疫抑制剂，可以延长同种异体皮肤移植物的存活时间。但接触这些药物的患者机会性感染的风险很高。未得到满足的需求是一种有效的策略，可以在不需要高剂量免疫抑制剂的情况下抑制同种异体皮肤移植的排斥反应。在这个项目中，我们建议通过利用供受者细胞之间不同的II类主要组织相容性复合体(MHC)分子来设计选择性免疫抑制。为了实现这一点，我们将使用一种新的生物材料系统，通过该系统，供体白细胞被滞留在宿主-移植物界面。因为只有供体细胞是靶向的，所以这种干预是一种靶向免疫疗法。中心假设是，我们开发的抗供体MHC注射系统将通过阻止供体白细胞运输到受体淋巴结来减轻同种异体皮肤移植的排斥反应。该系统需要两亲多肽(“EAK16-II”及其组化类似物“EAKIIH6”)和连接蛋白(抗H6抗体和蛋白A/G)的低粘度混合物。通过将组分拴在组氨酸标记的(EAK16-II/EAKIIH6)膜上，抗体被定位和定向(Biomaterals，2011，32：249)。来自供体皮肤的白细胞通过与抗供体MHC-II抗体相互作用滞留在膜上。减少的贩运预计将延长皮肤移植物的存活时间，在烧伤治疗中具有足够的意义。我们有证据表明，该系统在体内是稳定的。膜定位抗体在注射部位至少保留6天，其浓度显著高于生理盐水注射的抗体(分子药学，2013，10：1035)。此外，初步研究表明，在移植物-宿主界面放置抗供体MHC-II膜可显著减少供体白细胞在受体淋巴结中的积聚。这种干预导致同一只小鼠的T细胞激活减弱。这些已公布的和初步的数据支持中心假设。将实现三个目标，以在具有良好特征的小鼠皮肤移植模型中推进这一战略。目标1将用于在体外细胞捕获方面优化抗MHC-II抗体的密度和膜上的间距。在目标2中，我们将验证阻止供体细胞体内转运的机制。在目标3中，我们将测试该系统的免疫终点，通过该终点与主要的免疫抑制剂进行比较。研究人员有合作活动的记录，在高分子药物输送(Meng)、表面化学(Gawalt)、免疫分析(Giannoukakis)和细胞跟踪(Waggoner)方面具有综合专业知识。对公众健康的影响在于利用一种使能技术，通过这种技术可以减轻皮肤移植患者的急性排斥反应和严重感染。这项研究将是 免疫调节领域的一个重要影响，因为一个相关的动物模型被用来测试一个原始概念，以克服烧伤伤口护理中的一个主要障碍。创新之处在于通过环境响应性多肽联合组装展示抗体的能力。该平台是通用的；可以展示针对其他表面免疫分子的抗体，从而增加了调节的范围。

DESCRIPTION (provided by applicant): Each year in the United States more than 450,000 patients are treated for burn injuries with close to 30,000 hospitalizations in specialized burn centers. Human skin allografts are commonly used for temporary wound closure in severely burned victims to promote rapid healing. However, the intense antigenicity of skin allografts drives powerful anti-graft immune responses. Cell-to-cell interactions between donor and recipient leukocytes in skin-draining lymph nodes dictate the magnitude of rejection. Survival of skin allografts can be prolonged by giving transplant recipients immunosuppressants. But patients exposed to these drugs are at high risk for opportunistic infections. An unmet need is an effective strategy to suppress rejection of skin allografts without the need for high doses of immunosuppressants. In this project we propose to engineer selective immuosuppression by exploiting the different class II major histocompatibility complex (MHC) molecules between donor and recipient cells. To accomplish this, we will use a novel biomaterial system by which donor leukocytes are detained at the host-graft interface. Because only donor cells are targeted, the intervention is a form of targeted immunotherapy. The central hypothesis is that the anti-donor MHC injectable system we developed will attenuate rejection of skin allografts by impeding donor leukocytes trafficking to recipient lymph nodes. The system entails a low viscosity mixture of amphiphilic peptides ("EAK16-II" and its histidinylated analogue "EAKIIH6") and linker proteins (anti-H6 antibody and protein A/G). By tethering the components onto the His-tagged (EAK16-II/EAKIIH6) membrane antibodies are localized and oriented (Biomaterials, 2011, 32:249). Leukocytes emigrating from donor skins are detained on the membrane through interactions with anti-donor MHC-II antibodies. The reduced trafficking is expected to prolong survival of the skin graft sufficiently meaningful in burn treatment. We have evidence to show that the system is stable in vivo. Membrane-localized antibodies remain at injection site for at least 6 days, at concentrations significantly superior to antibodies injected in saline (Molecular Pharmaceutics, 2013, 10:1035). In addition, preliminary studies show that placing anti-donor MHC-II membranes at the graft-host interface significantly reduced donor leukocytes accumulation in recipient lymph nodes. This intervention resulted in attenuated T cell activation in the same mice. These published and preliminary data support the central hypothesis. Three aims will be carried out to advance the strategy in a well-characterized mouse skin transplant model. Aim 1 will serve to optimize anti-MHC-II antibody density and spacing on membrane with respect to cell capture in vitro. In aim 2 we will validate the mechanism of impeding donor cell trafficking in vivo. In aim 3 we will test the system for immunological endpoints by which comparison against a mainstay immunosuppressant will be made. The investigators have a track record of collaborative activities with combined expertise in macromolecule drug delivery (Meng), surface chemistry (Gawalt), immune analytics (Giannoukakis), and cell tracking (Waggoner). The public heath impact lies in leveraging an enabling technology by which acute rejection and serious infections in skin transplant patients can be mitigated. The research will be an important influence in the field of immune modulation because a pertinent animal model is used to test an original concept to overcome a major obstacle in burn wound care. The innovation lies in the ability to display antibodies through environmentally-responsive peptide co-assemblies. The platform is versatile; antibodies targeting other surface immune molecules can be displayed, thereby increasing the scope of the modulation.