Humoral and cellular immunity in polyomavirus-linked Merkel cell carcinoma

描述（由申请人提供）：默克尔细胞癌（MCC）是一种通常致命的皮肤癌，据报道，在过去的20年里，美国的发病率翻了两倍，达到每年1600例。2008年，默克尔细胞多瘤病毒（MCPyV）被发现整合在约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，这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导致T细胞功能障碍的患者MCC风险增加10- 30倍。这一建议建立在我们的发现之上，即对T-Ag的体液免疫反应与MCC进展有关，而细胞免疫反应似乎具有保护作用。与其他已知的人类多瘤病毒类似，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，在某些情况下，可以在患者或医生确诊之前检测到疾病进展。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复发特异性生物标志物的临床应用。我们还发现细胞介导的免疫（肿瘤内CD8+ T细胞浸润）与MCC的良好预后相关。因此，与David Koelle博士合作，在Aim 2中，我们将全面绘制MCPyV癌蛋白的T细胞表位/MHC限制图，开发肽MHC试剂，并使用它们表征MCPyV特异性T细胞在MCC患者血液和肿瘤中的频率和功能。在Aim 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在未来可能的人类MCC试验中的潜在功效。这些研究将与博士密切合作进行。Thomas Blankenstein和Gerald Willimsky使用他们现有的、具有良好特征的自发性多瘤病毒诱导的癌症小鼠模型，该模型在生物学、临床和免疫学上与MCC有着惊人的相似性。该提议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综合表征（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）。由于对MCC中表达的病毒蛋白的抗原特异性细胞和体液反应可以被追踪，这些研究将为更普遍的癌症免疫反应提供重要的生物学见解，对MCC患者具有直接适用的预后和治疗意义。

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.