ANCHOR MODIFIED PEPTIDES FOR IMMUNIZATION IN MELANOMA

最近的实验证据表明，针对某些恶性肿瘤的治疗性免疫是一种现实的方法。以抗原致敏的树突状细胞(DC)免疫荷瘤宿主为基础的临床前模型表明，已建立的肿瘤可以被诱导消退。肿瘤的消退依赖于完整的免疫系统，并由抗原特异性CD8+T淋巴细胞介导。这一建议建立在这样的前提下，即需要提供一种免疫原性多肽疫苗，并随后进行密集的免疫监测，以最佳地诱导能够根除残留肿瘤的有效T细胞反应。令人信服的证据表明，免疫原性与主要组织相容性复合体编码的分子的多肽结合亲和力有关。这项研究的主要目标是通过设计影响与HLAI类分子结合亲和力的关键(锚定)残基上修饰的多肽抗原，创造更好、更具免疫原性的黑色素瘤疫苗。黑色素瘤抗原gp100和MART-1锚定修饰的多肽将与DC一起用于临床免疫试验，旨在优化体内抗原特异性CD8+细胞毒性T淋巴细胞的生成。免疫学、病理学和放射学终点将被用来判断每种多肽的疗效。较新的方法，如T细胞受体β链分析和四色流式细胞术，将被纳入黑色素瘤疫苗试验，以实现更精确的监测。筛选出的多肽将用人类白细胞抗原转基因小鼠进行免疫原性验证。这一应用的具体目的是：1)创建由人类白细胞抗原-A2限制的gp100黑色素瘤抗原的锚定修饰多肽；2)鉴定gp100和MART-1的HLA-B7限制性表位；3)开发更好的策略来表征DC疫苗后人类T细胞的激活和募集。本申请中涉及的问题旨在更详细地了解细胞免疫、肿瘤消退和临床反应之间的关系。

Recent experimental evidence suggests that therapeutic immunization for certain malignancies is a realistic approach. Pre-clinical models based upon immunization of tumor-bearing hosts with antigen-pulsed dendritic cells (DC) demonstrate that regression of established tumors can be induced. Tumor regression is dependent upon an intact immune system and is mediated by antigen specific CD8+ T lymphocytes. This proposal is built upon the premise that delivery of an immunogenic peptide vaccine with subsequent intensive immunologic monitoring is required to optimally elicit an effective T cell response capable of eradicating residual tumor. Compelling evidence suggests that immunogenicity correlates with peptide binding affinity for molecules encoded by the major histocompatibility complex. The principal goal of this study is to create better, more immunogenic vaccines for melanoma by designing peptide antigens modified in crucial (anchor) residues that affect binding affinity for HLA class I molecules. Melanoma antigen gp100 and Mart-1 anchor modified peptides will be used with DC in clinical immunization trials designed to optimize the in vivo generation of antigen specific CD8+ cytotoxic T lymphocytes. Immunologic, pathologic, as well as radiologic endpoints will be used to judge the efficacy of each peptide. Newer methodologies such as T cell receptor beta chain repertoire analysis and four color flow cytometry will be incorporated into vaccine trials for melanoma to allow more precise monitoring. Immunogenicity of selected peptides will be validated using HLA transgenic mice. The specific aims of this application are: 1) to create anchor modified peptides of the gp100 melanoma antigen restricted by HLA-A2; 2) to identify HLA-B7 restricted epitopes of gp100 and Mart-1; 3) to develop better strategies to characterize human T cell activation and recruitment after DC vaccination. The issues addressed in this application are designed to provide a more detailed understanding of the relationship between cellular immunity, tumor regression, and clinical response.