MHC Class II Antigen Presentation In Melanoma: Impact on Immune Recognition

肿瘤特异性CD 4 T细胞应答的调节为改善癌症免疫治疗带来了巨大希望 免疫检查点抑制、癌症疫苗和过继性T细胞疗法。有效应对 免疫治疗需要T细胞识别来自癌细胞的突变肽表位，称为新抗原。 对免疫疗法的有效应答需要能够刺激CD 4和CD 8 T细胞的新抗原。 肿瘤特异性CD 4 T细胞识别由MHC II类呈递的新抗原。然而，实验或 用于鉴定免疫原性的MHC II类新抗原（引发T细胞免疫反应）的计算方法 （答案）没有得到很好的解决。虽然肿瘤特异性CD 4 T细胞表位是产生免疫应答所必需的， 有效的抗肿瘤T细胞对免疫疗法的反应，CD 4调节性T（Treg）细胞在免疫疗法中发育， 肿瘤抑制其它T细胞的增殖和功能。破坏CD 4 Treg细胞是一种有希望的 免疫学方法。然而，缺乏特异性靶向和破坏肿瘤特异性 CD 4 Treg细胞防止Treg细胞耗竭在癌症临床试验中进一步发展 免疫疗法肽-MHC四聚体可用于鉴定肿瘤特异性T细胞。然而，肽-MHC 许多已知会引发T细胞反应的肽抗原无法产生II类四聚体，因为 与MHC II类相互作用的肽的低亲和力或稳定性。该提案将推动该领域的 癌症免疫学通过解决三个知识空白：1）无法使用四聚体来识别大多数肿瘤- 特异性CD 4 T细胞，2）不能靶向肿瘤特异性Treg细胞进行破坏，和3）缺乏实验性免疫抑制剂。 和计算工具来优先考虑免疫原性MHC II类新抗原。该提案将利用一个新的， 仿生5-模块嵌合抗原受体（5 MCAR）的专利技术。5 MCAR由 与T细胞的跨膜和胞质结构域融合的肽-MHC II类的胞外域 受体，其促进与CD 3信号传导复合物的组装，以及由以下组成的替代辅助受体 与Src激酶Lck融合的CD 80。5 MCAR在细胞毒性T细胞上表达。通过5 MCAR发送信号 允许识别和杀死表达T细胞受体的CD 4 T细胞，而不是识别肽-MHC 5 MCAR的II类。中心假设是5 MCAR将有助于确定免疫原性MHC II类黑色素瘤新抗原，并通过破坏肿瘤特异性CD 4 Treg细胞。该提案的目的是鉴定免疫原性MHC II类新抗原并测试其功效。 在治疗黑素瘤中消耗新抗原特异性CD 4细胞， 小鼠黑素瘤模型。使用5 MCAR的基于细胞的试验将用于高通量筛选， 肽库，以鉴定诱导CD 4常规T细胞和调节性T细胞的MHC II类新抗原。 黑色素瘤的细胞反应。肿瘤特异性5 MCAR T细胞在治疗已建立的免疫缺陷综合征中的功效 通过单独的新抗原特异性Treg细胞的耗竭和与免疫调节剂的组合， 将评估抗PD-1的检查点抑制。使用生成的全面、公正的数据集 通过测试所有错义突变的免疫原性， 将创建并验证MHC II类新抗原。该提案的影响是：1）建立一个 与亚利桑那大学的Kuhns博士合作，一个西班牙裔服务机构，2）将一个新的 允许高通量筛选以鉴定免疫原性MHCII类的技术创新 新抗原，肿瘤特异性CD 4 Treg细胞的靶向破坏，以及改进的计算方法， 优先考虑免疫原性MHC II类新抗原，3）通过以下方式增加优异奖的影响： 解决当前知识中阻碍癌症免疫治疗进步的差距， 改善退伍军人的癌症护理，以及4）协助代表性不足的调查人员从事VA研究。

Regulation of tumor-specific CD4 T cell responses holds great promise for improving cancer immunotherapy with immune checkpoint inhibition, cancer vaccines, and adoptive T cell therapy. Effective response to immunotherapy requires T cell recognition of mutated peptide epitopes from cancer cells, called neoantigens. Effective response to immunotherapy requires neoantigens capable of stimulating both CD4 and CD8 T cells. Tumor-specific CD4 T cells recognize neoantigens presented by MHC class II. However, experimental or computational methods for identification of MHC class II neoantigens that are immunogenic (elicit a T cell response) have not been well-established. While tumor-specific CD4 T cell epitopes are necessary to generate effective anti-tumor T cell responses to immunotherapy, CD4 regulatory T (Treg) cells that develop within tumors suppress the proliferation and function of other T cells. Destroying CD4 Treg cells is a promising immunotherapeutic approach. However, the lack of a method to specifically target and destroy tumor-specific CD4 Treg cells prevents depletion of Treg cells from advancing further in clinical trials for cancer immunotherapy. Peptide-MHC tetramers can be used to identify tumor-specific T cells. However, peptide-MHC class II tetramers cannot be generated for many peptide antigens that are known to elicit T cell responses due to low affinity or stability of the peptide interaction with MHC class II. This proposal will advance the field of cancer immunology by addressing three gaps in knowledge: 1) inability to use tetramers to identify most tumor- specific CD4 T cells, 2) inability to target tumor-specific Treg cells for destruction, and 3) lack of experimental and computational tools to prioritize immunogenic MHC class II neoantigens. This proposal will utilize a new, patented technology of a biomimetic 5-module chimeric antigen receptor (5MCAR). The 5MCAR consists of the ectodomains of peptide-MHC class II fused to the transmembrane and cytoplasmic domains of the T cell receptor, which facilitates assembly with the CD3 signaling complex, and a surrogate coreceptor composed of CD80 fused to the Src kinase Lck. The 5MCAR is expressed on a cytotoxic T cell. Signaling through the 5MCAR allows identification and killing of CD4 T cells expressing a T cell receptor than recognizes the peptide-MHC class II of the 5MCAR. The central hypothesis is that 5MCAR will facilitate determination of immunogenic MHC class II melanoma neoantigens and effectively treat melanoma tumors by destruction of tumor-specific CD4 Treg cells. The aim of this proposal is to identify immunogenic MHC class II neoantigens and test the efficacy of depleting neoantigen-specific CD4 cells in treating melanoma, using a clinically relevant, immunogenic mouse melanoma model. A cell based assay with 5MCAR will be used in high throughput screening with a peptide library to identify the MHC class II neoantigens which elicit CD4 conventional T cell and regulatory T cell responses in melanoma tumors. The efficacy of tumor-specific 5MCAR T cells in treating established melanoma tumors through depletion of neoantigen-specific Treg cells alone and in combination with immune checkpoint inhibition with anti-PD-1 will be assessed. Using the comprehensive, unbiased dataset generated from testing the immunogenicity of all missense mutations, a computational model to predict immunogenic MHC class II neoantigens will be created and validated. The impact of this proposal is to 1) establish a collaboration with Dr. Kuhns at the University of Arizona, a Hispanic Serving Institution, 2) incorporate a new technological innovation to allow high throughput screening for identification of immunogenic MHC class II neoantigens, targeted destruction of tumor-specific CD4 Treg cells, and improved computational methods for prioritization of immunogenic MHC class II neoantigens, 3) increase the impact of the Merit award by addressing gaps in the current knowledge that prevent advancement of cancer immunotherapy and ultimately improve cancer care for Veterans, and 4) assist underrepresented investigators engage in VA Research.