Humoral and cellular immunity in polyomavirus-linked Merkel cell carcinoma

描述（由申请方提供）：默克尔细胞癌（MCC）是一种常见的致死性皮肤癌，在美国，报告的发病率在过去20年中翻了两番，达到约1，600例/年。2008年，发现默克尔细胞多瘤病毒（MCPyV）整合在约80%的MCC肿瘤中。MCC需要持续表达病毒T抗原（T-Ag）癌蛋白才能生长，为合理的免疫治疗提供了靶点。虽然大多数MCC患者没有明显的免疫缺陷，但由于HIV，慢性白血病或免疫抑制药物而导致T细胞功能障碍的人有10至30倍的MCC风险。这一提议建立在我们的发现基础上，即对T-Ag的体液免疫应答与MCC进展有关，而细胞免疫应答似乎具有保护性。 与其他已知的人多瘤病毒类似，MCPyV感染在一般人群中普遍存在（53%的成年人具有抗MCPyV衣壳蛋白抗体）。与此形成鲜明对比的是，我们发现MCPyV T-Ag癌蛋白抗体在人群对照中很少见（1%），但在新诊断的MCC患者中很普遍（约50%）。此外，抗T-Ag抗体滴度在MCC患者中是动态的，并且与肿瘤负荷平行增加，从而允许在某些情况下在患者或医生鉴定之前检测疾病进展。在目标1中，我们建议进一步表征抗T-Ag抗体并测试其作为MCC复发的特异性生物标志物的临床效用。我们还发现细胞介导的免疫（肿瘤内CD 8 + T细胞浸润）与MCC预后良好相关。因此，与大卫Koelle博士合作，在目标2中，我们将全面绘制MCPyV癌蛋白的T细胞表位/MHC限制，开发肽-MHC试剂，并使用它们来表征MCC患者血液和肿瘤中MCPyV特异性T细胞的频率和功能。在目标3中，我们将使用人类肿瘤样本和MCC小鼠模型来确定三种免疫刺激疗法的潜在疗效，用于未来可能的人类MCC试验。这些研究将与托马斯布兰肯斯坦博士和杰拉尔德威利姆斯基博士密切合作，使用他们现有的、充分表征的自发性多瘤病毒诱导的癌症小鼠模型进行，该模型与MCC具有惊人的生物学、临床和免疫学相似性。 该提案结合了研究人员的专业知识，他们在三个协同领域都有超过十年的生产力记录：MCC的临床和转化研究（Nghiem），对人类皮肤相关病毒的细胞免疫反应的全面表征（Koelle）以及对小鼠模型中多瘤病毒驱动的散发性癌症的体液和细胞免疫反应的表征（Blankenstein/Willimsky）。由于抗原特异性的细胞和体液反应，在MCC中表达的病毒蛋白可以跟踪，这些研究将提供显着的生物学洞察到免疫反应的癌症更普遍，直接适用的预后和治疗MCC患者的影响。

DESCRIPTION (provided by applicant): Merkel cell carcinoma (MCC) is an often-lethal skin cancer with a reported incidence that has quadrupled in the past 20 years to ~1,600 cases/year in the US. In 2008, the Merkel cell polyomavirus (MCPyV) was discovered to be integrated in ~80% of MCC tumors. MCCs require persistent expression of the viral T antigen (T-Ag) oncoprotein for growth, providing a target for rational immune therapy. Although most MCC patients have no apparent immune defect, persons with T cell dysfunction due to HIV, chronic leukemia or immunosuppressive drugs have a 10- to 30-fold increased MCC risk. This proposal builds on our findings that humoral immune responses to T-Ag are linked to MCC progression while cellular immune responses appear to be protective. Similar to the other known human polyomaviruses, MCPyV infection is prevalent in the general population (53% of adults have anti-MCPyV capsid protein antibodies). In marked contrast, we have found that antibodies to MCPyV T-Ag oncoproteins are rare in population controls (1%) but are prevalent among newly diagnosed MCC patients (~50%). Moreover, anti-T-Ag antibody titers are dynamic in MCC patients and increase in parallel to tumor burden, allowing detection of disease progression in some cases before identification by the patient or physician. In Aim 1, we propose to further characterize anti-T-Ag antibodies and to test their clinical utility as a specific biomarker for MCC recurrence. We have also found that cell-mediated immunity (intratumoral CD8+ T cell infiltration) is associated with excellent MCC prognosis. Therefore, in collaboration with Dr. David Koelle, in Aim 2 we will comprehensively map T cell epitopes/MHC restriction for MCPyV oncoproteins, develop peptide-MHC reagents, and use them to characterize the frequency and function of MCPyV-specific T cells in the blood and tumors of MCC patients. In Aim 3, we will use human tumor samples and a mouse model of MCC to determine the potential efficacy of three immune stimulating therapies for possible future human MCC trials. These studies will be performed in close collaboration with Drs. Thomas Blankenstein and Gerald Willimsky using their existing, well-characterized mouse model of spontaneous polyomavirus-induced cancer that shares striking biologic, clinical, and immunologic similarities with MCC. This proposal combines the expertise of investigators who each have over ten years of documented productivity in three synergistic areas: clinical and translational research in MCC (Nghiem), comprehensive characterization of the cellular immune response to human skin-associated viruses (Koelle) and characterization of the humoral and cellular immune responses to polyomavirus-driven sporadic cancer in mouse models (Blankenstein/Willimsky). Because antigen-specific cellular and humoral responses to viral proteins expressed in MCC can be tracked, these studies will provide significant biological insight into the immune response to cancer more generally, with directly applicable prognostic and therapeutic implications for MCC patients.