Interferon-gamma limits the effectiveness of peptide vaccines for cancer

描述(申请人提供)：开发有效的基于T细胞的癌症免疫疗法，无论是治疗性疫苗的形式还是过继T细胞疗法，仍然是肿瘤免疫学领域的主要研究领域之一。我们实验室最近设计了一种新的免疫策略(TriVax)，由CD8T细胞表位的合成肽、Poly-IC佐剂(一种Toll样受体激动剂)和免疫共刺激抗体组成。在小鼠恶性黑色素瘤模型中，我们观察到TriVax能够诱导大量抗原特异性的肿瘤反应性CD8T细胞反应，可达到总CD8T细胞的50%以上。在评估TriVax对已建立的B16黑色素瘤的治疗效果时，我们观察到，在没有干扰素-γ的情况下，抗肿瘤效果(肿瘤排斥反应和增加生存期)明显更好。这些观察结果是矛盾的，因为干扰素？长期以来一直被认为是一种效应性细胞因子，具有很强的抗肿瘤作用。进一步的体外实验表明，疫苗产生的CD8T细胞对B16黑色素瘤细胞的识别能力在干扰素？支持我们体内抗肿瘤的观察。这些结果令人费解，因为用干扰素治疗B16黑色素瘤细胞？显著增加MHC-I分子的表达，这应该会增强而不是降低肿瘤的T细胞抗原性。我们推测，经干扰素处理后，T细胞识别的特异性多肽/MHC-I复合体(同源MHC-I)并没有增加到与无关肽/MHC-I(非同源)复合体相同的程度，从而降低了肿瘤细胞的整体特异性表位密度，导致肿瘤细胞的抗原性降低。此外，我们假设肿瘤细胞上过多的非同源MHC-I通过降低CD8分子将LCK淋巴细胞特异性酪氨酸激酶招募到免疫突触中的能力来阻止T细胞的充分激活。此外，肿瘤暴露于干扰素？增强CD8 T细胞抑制受体(PD1和LAG3)的配体的表达，这也不利于TriVax免疫治疗的治疗反应。这项申请的两个主要目标将是澄清干扰素？对CD8 T细胞免疫治疗的疗效产生负面影响，并探讨克服这些障碍的方法，以期为已确立的恶性肿瘤制定更有效的治疗策略。为了验证我们的假设并实现这些目标，我们建议研究以下具体目标：1)研究干扰素？降低黑色素瘤对CD8T淋巴细胞的抗原性；2)评估干扰素的重要性？诱导肿瘤细胞表达PD1和LAG3配体对TriVax抗黑色素瘤疗效的影响3)通过克服干扰素的负面作用，探讨提高TriVax疗效的几种策略；以及4)评价干扰素的负面作用。在乳腺癌小鼠模型中使用TriVax。这些研究结果将有助于阐明干扰素？似乎在基于T细胞的肿瘤免疫治疗中发挥作用，并将使我们能够为已建立的癌症设计更有效的治疗策略。

DESCRIPTION (provided by applicant): The development of effective T cell based immunotherapy for cancer, either in the form of a therapeutic vaccine or as adoptive T cell therapy continues to be one of the major areas of research in the field of tumor immunology. Our laboratory has recently designed a novel immunization strategy (TriVax), consisting of synthetic peptides corresponding to CD8 T cell epitopes, Poly-IC adjuvant (a Toll-like receptor agonist) and immune costimulatory antibodies. Using a mouse model of malignant melanoma we observed that TriVax was capable of inducing large antigen-specific, tumor reactive CD8 T cell responses that can amount to more than 50% of the total CD8 T cells. When evaluating the therapeutic effects of TriVax against established B16 melanomas, we observed that the anti-tumor effects (tumor rejection and increased survival) were significantly better in the absence of interferon-gamma (IFN?). These observations are paradoxical since IFN? has long been considered to be an effector cytokine that provides strong anti-tumor effects. Further in vitro experiments have revealed that vaccine generated CD8 T cells were able to recognize B16 melanoma cells less effectively when the tumor cells were treated with IFN? supporting our in vivo anti-tumor observations. These results are puzzling since treatment of B16 melanoma cells with IFN? increases significantly the expression of MHC-I molecules, which should augment, not decrease the tumor's T cell antigenicity. We hypothesize that the specific peptide/MHC-I complexes (cognate MHC-I) recognized by the T cells are not increased to the same extent as the irrelevant peptide/MHC-I (non-cognate) complexes after treatment with IFN?, reducing the overall specific epitope density and leading to a decrease in the antigenicity of tumor cells. In addition, we hypothesize that excess of non-cognate MHC-I on tumor cells prevents the full activation of the T cells by reducing the ability of the CD8 molecules to recruit the Lck lymphocyte-specific tyrosine kinase into the immunological synapse. Furthermore, exposure of tumors to IFN? enhances the expression of ligands for CD8 T cell inhibitory receptors (PD1 and LAG3), which are also detrimental for the therapeutic response to TriVax immunotherapy. The two main objectives of this application will be to clarify the mechanisms by which IFN? exerts a negative effect in the therapeutic efficacy of CD8 T cell immunotherapy and to investigate means to overcome these obstacles in order to develop more effective therapeutic strategies for established malignancies. To test our hypotheses and fulfill these objectives we propose to study the following specific aims: 1) To investigate the mechanisms by which IFN? reduces the antigenicity of melanoma for CD8 T lymphocytes; 2) To assess the importance of the IFN? induced expression of PD1 and LAG3 ligands on tumor cells for the therapeutic efficacy of TriVax against melanoma. 3) To explore several strategies to enhance the therapeutic efficacy of TriVax by overcoming the negative effects of IFN?; and 4) To evaluate the negative effects of IFN? using TriVax in a mouse model of breast cancer. The results of these studies will help clarify the dual role that IFN? appears to play in T cell based tumor immunotherapy and will allow us to design more effective therapeutic strategies for established cancers.