The T cell immune response to cytomegalovirus across the adult lifecourse

巨细胞病毒（CMV）是人类疱疹病毒之一，感染超过80%的人。一旦一个人感染了CMV，病毒就永远无法从体内清除，我们的免疫系统需要不断地“对抗”病毒，以阻止它分裂并造成组织损伤。这种平衡是相当微妙的，CMV是免疫系统受到抑制的患者的主要问题，例如那些接受移植的患者。也许是因为病毒和免疫系统之间的这种“消耗战”，血液中针对CMV的T细胞免疫应答是针对任何病原体的最大记录。此外，对人群的研究表明，这种大的免疫反应可能与某些人的健康问题有关，如老年人或肾病患者。在这项补助金中，我们建议扩展我们几年来所做的工作，以确切了解T细胞如何对抗CMV，并开发在其成为健康风险的情况下控制免疫反应的方法。这项工作有4个部分。在第一部分中，我们将研究如何在所有年龄段的人群中建立和维持对CMV的免疫应答的幅度和组成。我们将评估它是否与人们首次感染时接触的病毒水平有关，以及人们在血液或肝脏慢性感染期间携带的“病毒载量”水平是否也是一个关键因素。我们还将研究淋巴细胞通过一种称为HLA-C的分子杀死CMV感染细胞的重要性。我们已经证明，这些T细胞在一生中积累，使它们在老年人中变得非常普遍。这些细胞是感染细胞的高效“杀手”，除了研究它们如何发展外，我们还将评估它们在CMV感染免疫治疗中的潜在用途。 在第二部分中，我们将利用CMV的独特功能和强大技术的发展，研究CD 4+和CD 8 + T细胞对CMV应答的分化的细节。在这里，我们将使用HLA-肽四聚体从组织样本中分离病毒特异性细胞，并立即使用称为CyTOF的技术对其表型进行详细评估。此外，我们将确定细胞的转录组（“RNA谱”），并评估其表观遗传状态。这将使我们第一次看到基因组调控如何定义人类抗原特异性T细胞反应的发展。一个重要的比较将是年轻人和老年人的结果，因为有证据表明，这些细胞的“干细胞样”潜力在衰老过程中下降。此外，我们希望这项工作的全面性将有助于理解对癌症等疾病的免疫反应。第3部分将讨论一个重要的“免疫检查点受体（ICR）”蛋白家族如PD-1在CMV感染中的作用。这些分子的作用是“抑制”T细胞功能，阻断其活性的抗体在癌症治疗中非常重要。在这里，我们将利用CMV模型来了解ICR蛋白在健康供体和接受PD-1阻断治疗的患者中的功能。最后，当CMV对健康构成威胁时，我们使用抗病毒药物来控制它。我们已经在供体和患者中进行了两项这样的研究，发现这确实抑制了体内CMV的水平。在这项工作中，我们将详细分析治疗如何影响对CMV的免疫反应。我们的目标是指导抗病毒治疗在可能有益的患者群体中的引入，例如老年人。这项工作是关于我们的白色细胞如何对CMV做出反应的最全面的研究之一，我们相信这将有助于大幅改善CMV感染和其他疾病的健康结果。

Cytomegalovirus (CMV) is one of the human herpesviruses and infects over 80% of people. Once a person has been infected with CMV the virus can never be cleared from the body and our immune system needs to constantly 'fight' the virus to stop it dividing and causing tissue damage. This balance is quite finely set and CMV is a major problem in patients whose immune system is suppressed, such as those undergoing transplantation.Perhaps because of this 'war of attrition' between the virus and immune system, the T cell immune response that develops against CMV in the blood is the largest that has been recorded against any pathogen. Moreover, studies in populations have shown that this large immune response can be associated with health problems in certain people, such as the elderly or those with kidney disease. In this grant we propose to extend work that we have undertaken over several years to understand exactly how T cells fight CMV and to develop approaches to control the immune response in situations where it becomes a health risk.The work has 4 sections. In the first part we will investigate how the magnitude and composition of the immune response to CMV is established and maintained in people of all ages. We will assess if it is related to the level of virus that people are exposed to when they are first infected and if the level of the 'viral load' that people carry during chronic infection within the blood or liver is also a critical factor. We will also investigate the importance of lymphocytes that kill CMV-infected cells by acting through a molecule called HLA-C. We have shown that these T cells accumulate over the lifetime such that they become extremely common in older people. These cells are highly effective 'killers' of infected cells and, as well as investigating how they develop, we will also assess their potential use for the immunotherapy of CMV infection. In the second part we will exploit the unique features of CMV, and development of powerful technologies, to study fine details of the differentiation of the CD4+ and CD8+ T cell response to CMV. Here we will use HLA-peptide tetramers to isolate virus-specific cells from tissue samples and immediately undertake a detailed assessment of their phenotype using a technology called CyTOF. Moreover, we will determine the transcriptome ('RNA profile') of the cells and also assess their epigenetic status. This will allow us, for the first time, to see how genomic regulation defines how human antigen-specific T cell responses develop. An important comparison will be between the results in younger and older people as there is evidence that the 'stem cell like' potential of these cells decreases during ageing. In addition, we hope that the comprehensive nature of this work will help understanding of the immune response to diseases such as cancer. Part 3 will address how an important family of 'immune checkpoint receptor (ICR)' proteins such as PD-1 operate in CMV infection. These molecules act to 'suppress' T cell function and antibodies that block their activity are very important in cancer therapy. Here we will take advantage of the CMV model to understand the function of the ICR proteins, in both healthy donors and patients on PD-1 blocking therapy.Finally, we are using anti-viral drugs to control CMV when it becomes a danger to health. We have undertaken two such studies in donors and patients and find that this does indeed suppress the level of CMV in the body. In this work we will undertake a detailed analysis of how treatment influenced the immune response to CMV. The aim here is that this will guide the introduction of anti-viral treatment for patient groups where it may be beneficial, such as the elderly.The work represents one of the most comprehensive studies of how our white cells respond to CMV and we are confident that this will contribute to substantially improving health outcomes, both within CMV infection and beyond.