Project 3: Adaptive immunity to MCPyV in Merkel cell carcinoma

摘要：项目3 默克尔细胞多瘤病毒（MCPyV）阳性的默克尔细胞癌（MCC）表现出显著的和及时的 有机会解决肿瘤免疫学的基本问题。在人类癌症中几乎是独一无二的， 病毒阳性MCC（VP-MCC），a）细胞转化需要非自身病毒抗原，B）这些 癌蛋白很小并且具有很少的多态性，c）肿瘤突变负荷非常低，d）检测到 病毒癌蛋白特异性CD 4和CD 8 T细胞和B细胞是非常常见的，和e）活检， 通常获得。我们对MCPyV T抗原（T-Ag）的T细胞应答的研究提供了以下基本原理： 抗PD-1治疗的试验。这些最近FDA批准的疗法改善了许多人的结果 患有晚期疾病项目3的重点是患有当地或区域疾病的人，他们集体患有 在当前标准治疗后18个月时复发的可能性为37%。 项目3由一位经验丰富的病毒免疫学家和P01团队成员领导。我们的医疗中心 是MCC的一个完善的转诊中心，因此， 每年招募70-80名新患者。仔细剖析 针对MCPyV特异性获得性免疫及其结果，我们提出三个目的。目标1将决定 T-Ag特异性CD 8 T细胞表型（包括功能障碍和亲和力）与临床 早期MCPyV（+）MCC患者的结局。目标2将进行类似的研究， CD 4 T细胞，包括在细胞和分子水平上定量测量肿瘤CD 4浸润，以及 CD 4 T辅助细胞表型的测量。T细胞研究将集中在TIL和血液，这两个网站 严重的肿瘤抗原特异性T细胞定位和功能障碍。结果将与 抑制性肿瘤微环境的免疫组织化学研究。目标3针对抗体 对T-Ag的反应，其在MCPyV（+）MCC患者中随着肿瘤负荷而增加和减少。血清升高 抗T-Ag IgG预示肿瘤复发，系列检测被纳入2018年NCCN MCC护理指南。T型 将使用新型四聚体试剂检测血液中的Ag特异性B细胞，并通过IgG测序进行研究， 详细的免疫表型分析我们的小组已经检测到验证的T细胞IgG基因的体细胞高突变， Ag特异性B细胞，表明这些细胞已经穿过生发中心，但未能分化为 长寿命的抗体分泌细胞，一种非常不寻常的模式项目3的基本前提是， 我们将在VP-MCC中提供关于获得性免疫的信息， 因为他们的肿瘤抗原在病人中很少是保守的。

Summary: Project 3 Merkel cell polyomavirus (MCPyV)-positive Merkel cell carcinoma (MCC) presents a significant and timely opportunity to address basic questions in tumor immunology. Almost uniquely amongst human cancers, in virus-positive MCC (VP-MCC), a) a non-self, viral antigen is required for cell transformation, b) these oncoproteins are small and have few polymorphisms, c) the tumor mutation burden is very low, d) detection of viral oncoprotein-specific CD4 and CD8 T- and B-cells is very frequently possible, and e) biopsies are commonly obtained. Our studies of T-cell responses to the MCPyV T-antigen (T-Ag) provided the rationale for trials of anti-PD-1 therapy. These recently FDA-approved therapies have improved outcomes for many persons with advanced disease. Project 3 focuses on persons with local or regional disease, who collectively have a 37% chance of recurrence at 18 months after current standard therapy. Project 3 is led by an experienced viral immunologist and member with the P01 team. Our medical center is a well-established referral center for MCC, such that archived specimens from patients with known outcomes are available and 70-80 new patients are enrolled annually. To closely dissect the relationship between MCPyV-specific acquired immunity and outcomes, we propose three Aims. Aim 1 will determine the relationship between T-Ag-specific CD8 T-cell phenotype including dysfunction and avidity, with clinical outcomes, in persons with early-stage MCPyV (+) MCC. Aim 2 will conduct similar studies of the T-Ag-specific CD4 T-cells, including quantitative measures of tumor CD4 infiltration at the cell and molecular levels, and measurement of CD4 T helper phenotype. T-cell studies will focus on both TIL and blood, the site of both profound tumor-antigen specific T-cell localization and dysfunction. Results will be correlated with immunohistochemical studies of the suppressive tumor microenvironment. Aim 3 addresses the antibody response to T-Ag, which waxes and wanes with tumor burden in persons with MCPyV (+) MCC. Rising serum anti-T-Ag IgG presages tumor relapse and serial testing is included in 2018 NCCN guidelines for MCC care. T- Ag-specific B cells will be detected in blood using novel tetramer reagents and studied by IgG sequencing and detailed immunophenotyping. Our group has detected somatic hypermutation in the IgG genes of validated T- Ag-specific B-cells, indicating that these cells have traversed the germinal center, yet fail to differentiate into long-lived antibody secreting cells, a very unusual pattern. The underlying Premise of Project 3 is that insights we will deliver regarding adaptive immunity in VP-MCC will be generally applicable to malignancies that are harder to study because their tumor antigens are seldom conserved among patients.