Department of Biomedical Engineering, University at Buffalo, State University of New York, Buffalo, New York.
Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada.
Cancer Immunol Res. 2022 Mar 1;10(3):314-326. doi: 10.1158/2326-6066.CIR-21-0332.
Tumor-associated self-antigens are potential cancer vaccine targets but suffer from limited immunogenicity. There are examples of mutated, short self-peptides inducing epitope-specific CD8+ T cells more efficiently than the wild-type epitope, but current approaches cannot yet reliably identify such epitopes, which are referred to as enhanced mimotopes ("e-mimotopes"). Here, we present a generalized strategy to develop e-mimotopes, using the tyrosinase-related protein 2 (Trp2) peptide Trp2180-188, which is a murine MHC class I (MHC-I) epitope, as a test case. Using a vaccine adjuvant that induces peptide particle formation and strong cellular responses with nanogram antigen doses, a two-step method systematically identified e-mimotope candidates with murine immunization. First, position-scanning peptide microlibraries were generated in which each position of the wild-type epitope sequence was randomized. Randomization of only one specific residue of the Trp2 epitope increased antitumor immunogenicity. Second, all 20 amino acids were individually substituted and tested at that position, enabling the identification of two e-mimotopes with single amino acid mutations. Despite similar MHC-I affinity compared with the wild-type epitope, e-mimotope immunization elicited improved Trp2-specific cytotoxic T-cell phenotypes and improved T-cell receptor affinity for both the e-mimotopes and the native epitope, resulting in better outcomes in multiple prophylactic and therapeutic tumor models. The screening method was also applied to other targets with other murine MHC-I restriction elements, including epitopes within glycoprotein 70 and Wilms' Tumor Gene 1, to identify additional e-mimotopes with enhanced potency.
肿瘤相关的自身抗原是潜在的癌症疫苗靶点，但它们的免疫原性有限。有一些例子表明，突变的短自身肽比野生型表位更有效地诱导抗原特异性 CD8+T 细胞，但目前的方法还不能可靠地识别这些表位，这些表位被称为增强模拟表位（“e-mimotopes”）。在这里，我们提出了一种开发 e-mimotopes 的通用策略，使用酪氨酸酶相关蛋白 2（Trp2）肽 Trp2180-188作为测试案例，该肽是一种小鼠 MHC 类 I（MHC-I）表位。使用一种疫苗佐剂，该佐剂诱导肽颗粒形成和纳米抗原剂量的强烈细胞反应，我们通过两步法系统地识别了具有小鼠免疫原性的 e-mimotope 候选物。首先，生成了随机化野生型表位序列中每个位置的位置扫描肽微文库。仅随机化 Trp2 表位的一个特定残基就增加了抗肿瘤免疫原性。其次，我们逐个替换了所有 20 个氨基酸，并在该位置进行了测试，从而鉴定出两个具有单个氨基酸突变的 e-mimotopes。尽管与野生型表位相比，e-mimotope 的 MHC-I 亲和力相似，但 e-mimotope 免疫可诱导改善的 Trp2 特异性细胞毒性 T 细胞表型，并提高了 T 细胞受体对 e-mimotopes 和天然表位的亲和力，从而在多种预防性和治疗性肿瘤模型中取得了更好的结果。该筛选方法还应用于其他具有其他小鼠 MHC-I 限制元件的靶标，包括糖蛋白 70 和 Wilms 肿瘤基因 1 内的表位，以鉴定具有增强效力的其他 e-mimotopes。
