Cytomegalovirus-based Immunotherapy for Prostate Cancer

 描述(由申请人提供)： 前列腺癌是退伍军人管理局医疗保健系统中的一个非常普遍的问题。患有前列腺癌以外的男性的治疗方法很少；这些男性最需要治疗，因为他们死于这种疾病的风险最高。该项目将开发一种使用重组巨细胞病毒(CMV)的前列腺癌疫苗疗法。CMV载体是一种根本不同的疫苗，而不仅仅是另一种载体，因为a)它们是唯一提供持续免疫刺激的载体系统，b)反载体免疫是无关的，c)它们诱导针对非传统表位的更广泛的T细胞反应，d)它们即使在传播缺陷的情况下也能发挥作用。最后，这是第一个能够诱导免疫反应的载体系统，能够控制甚至是清晰的、高毒力的猿猴免疫缺陷病毒(SIV)。没有任何其他针对这种SIV的试验显示出任何类似的效果。含有人类免疫缺陷病毒序列的重组CMV正在与传播缺陷的HCMV/HIV载体进行临床开发，预计将于2016年在健康成年人身上进行I期临床试验。这项建议将探索使用基于CMV的病毒载体表达各种形式的前列腺特异性抗原(PSA)作为治疗小鼠前列腺癌的方法。很明显，PSA是一种抗原；它是免疫系统攻击正常前列腺的自身免疫性前列腺炎患者的主要抗原。这项研究将利用转基因小鼠前列腺癌(TRAMP)癌细胞(TRAMP)表达PSA(TRAMP-PSA)。用TRAMP-PSA癌细胞建立了前列腺癌的“人源化”小鼠模型。巨细胞病毒具有很强的种属特异性；实验需要小鼠巨细胞病毒(MCMV)。初步数据显示，表达PSA的小鼠CMV病毒构建物在TRAMP-PSA攻击的小鼠中诱导了保护性抗肿瘤免疫反应，这表明该方法是有希望的。人类巨细胞病毒在人类中造成终生感染，并且高度流行。超过一半的美国人口已经感染了CMV。虽然巨细胞病毒很少在健康的人身上引起疾病，但该病毒会在免疫抑制的患者中引起疾病。该病毒还有可能从接种疫苗的患者传播到环境中。这些特性对将CMV-PSA疫苗转化为临床应用构成了重大障碍。最近几个实验室的发现表明，完全的病毒复制可能不是诱导和维持针对CMV的强大免疫反应所必需的。这种病毒可以很容易地被改造成完全具有传染性，但不能繁殖后代。这种传播缺陷的载体对人类的使用更具可译性。目前建议的目的是确定编码PSA的MCMV载体的传播缺陷版本诱导的免疫水平是否足以维持其野生型MCMV对应物的抗肿瘤效果。这项研究还将确定MCMV-PSA疫苗是否是一种有效的治疗方法，当小鼠的肿瘤开始发展为更接近于模拟人类前列腺癌的模型时，通过在动物身上开始治疗，MCMV-PSA疫苗是否是一种有效的治疗方法。最后，CMV将与免疫检查点抑制剂抗CTLA4一起进行测试，以评估抗肿瘤效果的增强。本研究包括四个目的：1)检测MCMV-PSA载体与抗CTLA-4抗体的联合作用；2)在模拟人类疾病的自发性TRAMP小鼠模型中检测CMV-PSA载体；3)鉴定MCMV-PSA诱导的PSA特异性CD8和CD4T细胞的表型和功能；4)构建扩散缺陷的MCMV-PSA并检测其在转基因小鼠前列腺癌模型中的抗肿瘤作用。这项研究将产生最终的临床前数据，以推动创造一种有前景的男性前列腺癌治疗方法。

 DESCRIPTION (provided by applicant): Prostate cancer is a highly prevalent problem in the VA health care system. There are few therapies for men with cancer outside of the prostate; these are the men most in need of treatment because they are at the highest risk of death from the disease. This project will develop a vaccine therapy for prostate cancer using recombinant cytomegalovirus (CMV). CMV vectors are fundamentally different kind of vaccine, not just another vector because a) they are the only vector system providing persistent immune stimulation, b) anti-vector immunity is irrelevant, c) they induce a much broader T cell response directed against unconventional epitopes, d) they work even if they are spread-deficient. Finally, this is the first vector system that was able to induce an immune response that was able to control, even clear, highly virulent Simian Immunodeficiency Virus (SIV). Nothing else ever tried against this SIV has shown any similar efficacy. Recombinant CMV containing Human Immunodeficiency Virus sequences are in clinical development with spread-deficient HCMV/HIV vectors and expect to be in phase I clinical trials in 2016 in healthy adults. This proposal will explore the use of CMV-based viral vectors expressing various forms of Prostate Specific Antigen (PSA) as a therapy for prostate cancer in mice. It is clear that PSA is an antigen; it is a dominant antigen in men with autoimmune prostatitis where the immune system attacks the normal prostate. The study will utilize Transgenic Mouse Adenocarcinoma of the Prostate (TRAMP) cancer cells engineered to express PSA (TRAMP-PSA). A "humanized" mouse model of prostate cancer has been developed using TRAMP-PSA cancer cells. CMV has strong species specificity; the experiments require murine CMV (mCMV). Preliminary data showed that a murine CMV viral construct expressing PSA induced a protective anti-tumor immune response in mice challenged with TRAMP-PSA showing promise for the approach. Human CMV causes life-long infection in humans and is highly prevalent. More than half of the U.S population has been infected with CMV. While CMV rarely causes disease in healthy individuals, the virus can cause disease in immunosuppressed patients. The virus also has the potential of spreading into the environment from vaccinated patients. These characteristics present substantial hurdles to translation of a CMV-PSA vaccine into clinical use. Recent findings from several laboratories suggested that complete virus replication may not be necessary for induction and maintenance of the strong immune response against CMV. The virus can be readily engineered to be fully infectious but unable to make progeny. Such spread- deficient vectors are much more translatable to human use. The goal of current proposal is to determine whether the level of immunity induced by a spread- deficient version of the mCMV vector encoding PSA is sufficient to maintain the anti-tumor effect observed for its wild-type mCMV counterpart. The study will also determine whether the mCMV-PSA vaccine is an effective treatment for mice spontaneously developing the TRAMP tumor by starting treatment in the animals when their tumor has started to develop more closely modeling human prostate cancer. Finally, CMV will be tested in combination with the immune checkpoint inhibitor anti-CTLA4 to assess augmentation of the anti- tumor effect. The study consists of four aims: 1) To test the mCMV-PSA vectors in combination with anti- CTLA-4, 2) To test the CMV-PSA vectors in the spontaneous TRAMP mouse model more closely mimicking the human disease, 3) To characterize phenotype and function of PSA-specific CD8 and CD4 T cells induced by mCMV-PSA and, 4) To construct a spread-deficient version of mCMV-PSA and test its anti-tumor effect in transgenic mouse models of prostate cancer. The study will produce the final pre-clinical data needed to move forward with the creation of a promising therapy for prostate cancer in men.