Humoral and cellular immunity in polyomavirus-linked Merkel cell carcinoma

描述(申请人提供)：默克尔细胞癌(MCC)是一种经常致命的皮肤癌，据报道，在美国，其发病率在过去20年中翻了两番，达到每年约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需要病毒T抗原(T-Ag)癌蛋白的持续表达才能生长，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，但由于艾滋病毒、慢性白血病或免疫抑制药物而导致T细胞功能障碍的人MCC风险增加了10到30倍。这一建议建立在我们的发现基础上，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性。与其他已知的人类多瘤病毒类似，MCPyV感染在普通人群中很普遍(53%的成年人有抗MCPyV衣壳蛋白抗体)。与之形成鲜明对比的是，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患者中普遍存在(约50%)。此外，抗T-Ag抗体滴度在MCC患者中是动态的，并随着肿瘤负担的增加而增加，在某些情况下允许在患者或医生识别之前检测到疾病进展。在目标1中，我们建议进一步确定抗T-Ag抗体的特征，并测试它们作为MCC复发的特异性生物标志物的临床应用价值。我们还发现细胞免疫(瘤内CD8+T细胞浸润)与良好的MCC预后有关。因此，在目标2中，我们将与David Koelle博士合作，全面绘制MCPyV癌蛋白的T细胞表位/MHC限制图，开发多肽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小鼠MCC模型来确定未来可能进行的人类MCC试验的三种免疫刺激疗法的潜在疗效。这些研究将与Thomas Blankenstein博士和Gerald Willimsky博士密切合作，利用他们现有的、特征良好的自发性多瘤病毒诱发癌症的小鼠模型进行，该模型在生物学、临床和免疫学上与MCC有显著的相似之处。这项建议结合了研究人员的专业知识，他们各自在三个协同领域拥有超过十年的有据可查的生产力：MCC的临床和翻译研究(Nghiem)，对人类皮肤相关病毒的细胞免疫反应的全面表征(Koelle)，以及对多瘤病毒驱动的小鼠散发性癌症的体液和细胞免疫反应的表征(Blankenstein/Willimsky)。由于可以跟踪对MCC中表达的病毒蛋白的抗原特异性细胞和体液反应，这些研究将为更广泛地了解癌症的免疫反应提供重要的生物学见解，并直接适用于MCC患者的预后和治疗。

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.