Immunotherapy to enhance anti-HIV-1 responses against viral brain infection

项目摘要/摘要 针对程序性细胞死亡蛋白-1共抑制免疫的免疫治疗方法 Checkpoint已经彻底改变了几种晚期癌症的治疗方法。然而，病毒的易感性 特定的细胞类型仍然是高度可变的，很难预测。我们发现这两种小胶质细胞 星形胶质细胞通过上调PD-L1的表达来调控脑内浸润性抗病毒T细胞的活动 以努力限制破坏性脑炎反应。同样，我们发现CD4(+)调节性T细胞 (Tregs)通过抑制CD8(+)细胞毒性T淋巴细胞的扩增和活性来限制病毒性脑炎。 虽然大脑中的这些抗炎反应无疑对宿主有利，但防止 免疫介导的对这一重要器官的损害，建立一个长期的抗炎环境也可能 导致病毒清除方面的缺陷。接受CART成功的患者在两种情况下都受到病毒抑制 血浆和脑脊液，但持续的HIV-1储存库被认为是导致无法完全治愈的原因 感染。HIV特异的CD8(+)T细胞反应对于抑制大脑内的急性病毒感染至关重要， 但最终它们无法完全根除病毒。目前尚不清楚神经胶质细胞是否具有细胞活性。 免疫检查点封锁或Treg调制的目标。这里提出的研究旨在填补这一点 在我们对免疫抑制、神经保护的大脑微环境如何理解方面的关键空白 使病毒感染的完全清除复杂化。在我们以前的研究基础上，我们开发了一种 创新的小鼠实验模型，其中CD8(+)T细胞反应强烈，为免疫显性 HIV-1 Gag表位是通过异种Prime-Boost免疫在小鼠脑内产生的 表达p24衣壳蛋白的重组腺病毒载体(rAd5-p24) Pr55Gag/Env病毒样颗粒(HIVLP)。这一新的方法使我们能够研究 免疫疗法对一种强大、方便和廉价的小动物的病毒清除作用 模特。拟议中的研究将首先确定神经胶质细胞是否抑制T细胞介导的病毒清除 感染通过PD-1：PD-L1阴性免疫检查点。在目标#2中提出的实验将继续 确定PD-1：PD-L1轴的丢失或阻断是否会促进抗HIV-1T细胞介导的病毒 从大脑中清除。最后，在特定的目标#3中，我们将确定Treg细胞活性的调节 与免疫检查点封锁相结合将进一步刺激抗HIV-1 T细胞促进病毒 通行证。免疫检查点封锁和Treg调制的潜在协同组合是 目前是治疗各种免疫抑制癌症的密集研究领域。其中一个 当代HIV-1研究的首要任务是确定实现功能性治愈的策略，其中 在没有抗逆转录病毒治疗的情况下，病毒载量在很长一段时间内被完全抑制。这些研究将 确定免疫疗法是否可以用来逆转针对病毒脑储存库的免疫衰竭。

PROJECT SUMMARY/ABSTRACT Immunotherapeutic approaches which target the programmed cell death protein (PD)-1 co-inhibitory immune checkpoint have revolutionized treatment of several types of advanced cancer. However, the susceptibility of particular cell types remains highly variable and difficult to predict. We have found that both microglial cells and astrocytes govern the activity of brain-infiltrating antiviral T-cells through upregulation of PD-L1 expression in an effort to limit damaging encephalitic responses. Likewise, we have found that CD4(+) regulatory T-cells (Tregs) limit viral encephalitis through restraining expansion and activity of CD8(+) cytotoxic T-lymphocytes. While these anti-inflammatory responses within the brain are undoubtedly beneficial to the host, preventing immune-mediated damage to this vital organ, establishment of a prolonged anti-inflammatory milieu may also lead to deficiencies in viral clearance. Patients undergoing successful cART are viremically suppressed in both plasma and CSF, but persisting HIV-1 reservoirs are believed to contribute to the inability to completely cure infection. HIV-specific CD8(+) T-cell responses are critical in suppressing acute viral infection within the brain, but ultimately fail in their ability to fully eradicate virus. It is currently unknown whether glia are viable cellular targets for immune checkpoint blockade or Treg modulation. Studies proposed here are intended to fill this critical void in our understanding of how the immunosuppressive, neuroprotective brain microenvironment complicates complete clearance of viral infection. Building on our previous studies, we have developed an innovative experimental murine model in which strong CD8(+) T-cell responses specific for immunodominant HIV-1 Gag epitopes are generated within the brains of mice via heterologous prime-boost immunization with recombinant adenovirus vectors expressing the p24 capsid protein (rAd5-p24), followed by a CNS boost using Pr55Gag/Env virus-like particles (HIVLPs). This novel approach allows us to investigate the effects of immunotherapy on viral clearance from the brain in a powerful, yet convenient and inexpensive small animal model. The proposed studies will first determine whether glial cells restrain T-cell-mediated clearance of viral infection through the PD-1: PD-L1 negative immune checkpoint. Experiments proposed in Aim #2 will go on to determine whether loss or blockade of the PD-1: PD-L1 axis will facilitate anti-HIV-1 T-cell-mediated viral clearance from the brain. Finally, in Specific Aim #3 we will determine whether modulation of Treg cell activity in combination with immune checkpoint blockade will further stimulate anti-HIV-1 T-cells to promote viral clearance. The potentially synergistic combination of immune checkpoint blockade and Treg modulation is currently an area of intense investigation for treatment of a variety of immunosuppressive cancers. One of the highest priorities in contemporary HIV-1 research is to identify strategies to effect a functional cure, in which viral load is fully suppressed for extended periods in the absence of antiretroviral therapy. These studies will determine whether immunotherapy can be used to reverse immune exhaustion against the viral brain reservoir.