Nanoparticle Therapy for Targeted Drug Delivery in Organ Transplantation

 说明(申请人提供)：器官移植是治疗各种终末期器官疾病的公认疗法。需要全身免疫抑制来预防同种异体移植的免疫排斥反应。然而，感染、癌症和代谢紊乱等副作用是器官移植受者在接受必要的器官保存免疫抑制药物治疗时遭受的并发症之一。虽然在新的免疫抑制药物的设计和疗效方面取得了重大进展，但许多药物具有更高的系统性风险特征。尤其是雷帕霉素，已被证明是一种有效的免疫抑制剂，但会增加感染、伤口愈合问题和代谢副作用的风险。最近的研究表明，使用亚治疗剂量的雷帕霉素(不足以抑制移植物排斥反应)，结合全身增加体外扩增、过继转移的调节性T细胞(Treg)，可以防止移植物排斥反应2。这些开创性的研究表明，将小剂量雷帕霉素与标准免疫抑制护理相结合，可以通过诱导受者的免疫系统“自我免疫抑制”来延长移植物的存活时间。进一步规避雷帕霉素全身副作用的一种潜在方法是开发专门将雷帕霉素直接输送到移植组织的策略。许多导致同种异体免疫反应发展的启动事件已被证明发生在移植物3的水平上。因此，虽然目前的实践利用全身免疫抑制来调节宿主免疫，但人们越来越认识到，移植物水平的免疫抑制可能会对同种异体免疫产生更深远的影响，同时避免受体发生全身免疫抑制的并发症。在这里，我们建议使用新型的移植物靶向自组装胶束纳米颗粒来减轻急性和慢性排斥反应。为方便打击贪污，我们会 将这些靶向雷帕霉素胶束(TRAM)连接到可溶性重组补体受体2(CR2)上，CR2是我们广泛表征的靶向部分。CR2与补体蛋白C3(iC3b、C3dg和C3d)的长寿命裂解片段结合，我们已经证明这些片段在移植后早期沉积在心脏移植物中，作为对缺血-再灌注损伤的反应，这在所有实体器官移植中都是不可避免的。除了雷帕霉素负载和CR2靶向部分涂层外，胶束还将包含用于寻的和跟踪成像研究的近红外(NIR)荧光团。以前已经证明了CR2介导的靶向的可行性，并利用该靶向部分成功地传递了补体调节蛋白6。通过利用CR2的新靶向能力，我们将能够将雷帕霉素直接输送到移植器官。我们假设雷帕霉素可能被包装在生物惰性纳米颗粒中，在移植的同种异体移植物水平上被跟踪、靶向和释放，作为一种药物输送和局部免疫抑制的手段。

 DESCRIPTION (provided by applicant): Organ transplantation is an accepted therapy for various end-stage organ diseases. Systemic immunosuppression is required to prevent immunologic rejection in transplanted allografts. However, side- effects such as infections, cancers, and metabolic derangements are among the list of complications that organ transplant recipients suffer while on the necessary organ saving immunosuppressant medication. While significant advancements have been made with the design and efficacy of newer immunosuppressive medications, many carry heightened systemic risk profiles. In particular, rapamycin, has been shown to be an effective immunosuppressant, but carries an increased risk of infection, wound healing problems and metabolic side-effects1. Recent studies have shown that utilization of sub-therapeutic doses of rapamycin (insufficient to inhibit graft rejectin) combined with a systemic increase in ex-vivo expanded, adoptively transferred regulatory T cells (Treg) may prevent graft rejection2. These seminal studies suggest that combined low dose rapamycin with standard immunosuppressive care may prolong graft survival by inducing the recipient's immune system to `self-immunosuppress'. A potential way to further circumvent the systemic side-effects of rapamycin administration is to develop strategies to specifically deliver rapamycin directly to the grafted tissues. Many of the priming events that lead to the development of an alloimmune response have been shown to occur at the level of the graft3. Thus, while current practice utilizes systemic immunosuppression to modulate host immunity there is a growing appreciation that immune suppression at the graft level may have more profound effects on alloimmunity whilst sparing the recipient from the complications of systemic immunosuppression. Here, we propose to use novel graft targeting self-assembling micelle nanoparticles to attenuate both acute and chronic rejection. To facilitate graft targeting, we will conjugate these Targeted Rapamycin Micelles (TRaM) to soluble recombinant complement receptor 2 (CR2), a targeting moiety we have extensively characterized4. CR2 binds to long lived cleavage fragments of complement protein C3 (iC3b, C3dg, and C3d), which we have shown to deposit in cardiac allografts early post-transplantation as a response to ischemia- reperfusion injury, an unavoidable event in all solid organ transplants5. In addition to rapamycin loading and CR2 targeting moiety coating, micelles will contain near infrared (NIR) fluorophores for homing and tracking imaging studies. The feasibility of CR2 mediated targeting has previously been demonstrated and successful delivery of complement regulatory proteins utilizing this targeting moiety has been achieved6. By utilizing the novel targeting capabilities o CR2 we will be able to deliver rapamycin directly to the grafted organ. We hypothesize that rapamycin may be packaged within a biologically inert nanoparticle, tracked, targeted to, and released at the level of a transplanted allograft as a means for drug delivery and local immunosuppression.