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

项目总结/摘要 靶向程序性细胞死亡蛋白（PD）-1共抑制免疫的免疫方法 检查点已经彻底改变了几种类型的晚期癌症的治疗。然而， 特定的细胞类型仍然是高度可变的并且难以预测。我们发现小胶质细胞 星形胶质细胞通过上调PD-L1表达来控制脑浸润性抗病毒T细胞的活性 以限制损害性脑炎反应。同样，我们发现CD 4（+）调节性T细胞 （THBE）通过抑制CD 8（+）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益，但防止 免疫介导的对这一重要器官的损害，建立长期的抗炎环境也可能 导致病毒清除不足。接受成功cART的患者在两种情况下都受到病毒抑制， 血浆和CSF，但持续存在的HIV-1储库被认为是无法完全治愈的原因 感染HIV特异性CD 8（+）T细胞应答在抑制脑内急性病毒感染方面至关重要， 但最终无法完全根除病毒。目前尚不清楚胶质细胞是否是可存活的细胞， 免疫检查点阻断或Treg调节的靶点。这里提出的研究旨在填补这一空白。 我们对免疫抑制、神经保护的大脑微环境 使病毒感染的完全清除复杂化。在我们以前研究的基础上，我们开发了一个 创新的实验小鼠模型，其中对免疫显性免疫特异性的强CD 8（+）T细胞应答 HIV-1 Gag表位通过异源初免-加强免疫在小鼠脑内产生， 表达p24衣壳蛋白的重组腺病毒载体（rAd 5-p24），随后使用 Pr 55 Gag/Env病毒样颗粒（HIVLPs）。这种新颖的方法使我们能够研究 免疫治疗对病毒清除从大脑中的一个强大的，但方便和廉价的小动物 模型拟议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。 通过PD-1：PD-L1阴性免疫检查点感染。目标2中提出的实验将继续进行， 确定PD-1：PD-L1轴的缺失或阻断是否会促进抗HIV-1 T细胞介导的病毒 从大脑中清除最后，在具体目标#3中，我们将确定调节Treg细胞活性是否 结合免疫检查点阻断将进一步刺激抗HIV-1 T细胞， 间隙免疫检查点阻断和Treg调节的潜在协同组合是 目前是治疗多种免疫抑制性癌症的深入研究领域。之一 当代HIV-1研究的最高优先事项是确定实现功能性治疗的策略，其中 在没有抗逆转录病毒疗法的情况下，病毒载量被长时间完全抑制。这些研究将 确定是否可以使用免疫疗法来逆转针对病毒脑储库的免疫耗竭。

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.