黑色素瘤抗原基因（MAGE）型抗原是癌症免疫治疗的有希望的靶标，因为它们在癌细胞中表达，但在正常组织中不表达（雄性生殖细胞除外）。小鼠 P1A 抗原具有这种 MAGE 型表达模式，并已被用作临床前肿瘤模型的靶抗原，旨在诱导抗肿瘤 CD8 T 细胞反应。然而，迄今为止，仅鉴定出一个 MHC I 限制性 P1A 表位。它由 H-2Ld 在 H-2d 遗传背景（例如 DBA/2 和 BALB/c）的小鼠中呈递。鉴于 C57BL/6 背景下存在多种基因改变小鼠品系，定义 H-2b 单倍型呈现的 P1A T 细胞表位将很有用，以促进更精细的机制研究。我们采用了异源初免-加强基于黑猩猩腺病毒 (ChAdOx1) 和编码 P1A 的改良痘苗安卡拉 (MVA) 的疫苗接种策略，可在 C57BL/6 小鼠中诱导 P1A 特异性 T 细胞反应。通过细胞内细胞因子染色和多参数流式细胞术测量疫苗诱导的反应。我们绘制了免疫原性 CD8 表位，并克隆了同源 T 细胞受体 (TCR)，用于过继细胞疗法。ChAdOx1/MVA-P1A 疫苗接种可在 C57BL/6 小鼠中诱导强烈的 P1A 特异性 CD8 T 细胞反应。该反应针对单个 9 氨基酸肽，其序列为 FAVVTTSFL，对应于 P1A 氨基酸 43-51。它由 H-2Db 提出。 P1A 疫苗接种，尤其是肌内注射 ChAdOx1 和静脉注射 MVA，可以保护小鼠免受表达 P1A 的 EL4 (EL4.P1A) 肿瘤细胞的攻击。我们鉴定并克隆了 4 个对 H-2Db 限制性 P1A43-51 肽具有特异性的 TCR。用这些 TCR 转导的 T 细胞识别 EL4.P1A，但不识别 MC38.P1A 和 B16F10.P1A 肿瘤细胞，可能是由于这些细胞中存在的蛋白酶体亚型存在差异。将这些 T 细胞过继转移到携带 EL4.P1A 肿瘤的小鼠中，可减少肿瘤生长并提高存活率。我们鉴定了 H-2b 背景中存在的 MAGE 型 P1A 肿瘤抗原的第一个 CD8 T 细胞表位。这为剖析 MAGE 型特异性抗肿瘤免疫的机制研究开辟了新的视角，利用了 C57BL/6 背景中丰富的基因改造小鼠品系。这应该有助于特定癌症免疫疗法的进步。©作者（或其雇主）2024。根据 CC BY-NC 允许重复使用。禁止商业再利用。请参阅权利和权限。英国医学杂志出版。

Melanoma antigen gene (MAGE)-type antigens are promising targets for cancer immunotherapy as they are expressed in cancer cells but not in normal tissues, except for male germline cells. The mouse P1A antigen shares this MAGE-type expression pattern and has been used as a target antigen in preclinical tumor models aiming to induce antitumor CD8+ T-cell responses. However, so far only one MHC I-restricted P1A epitope has been identified. It is presented by H-2Ld in mice of the H-2d genetic background such as DBA/2 and BALB/c. Given the availability of multiple genetically altered strains of mice in the C57BL/6 background, it would be useful to define P1A T-cell epitopes presented by the H-2b haplotype, to facilitate more refined mechanistic studies.We employed a heterologous prime-boost vaccination strategy based on a chimpanzee adenovirus (ChAdOx1) and a modified vaccinia Ankara (MVA) encoding P1A, to induce P1A-specific T-cell responses in C57BL/6 mice. Vaccine-induced responses were measured by intracellular cytokine staining and multiparameter flow cytometry. We mapped the immunogenic CD8 epitope and cloned the cognate T-cell receptor (TCR), which we used for adoptive cell therapy.ChAdOx1/MVA-P1A vaccination induces a strong P1A-specific CD8+ T-cell response in C57BL/6 mice. This response is directed against a single 9-amino acid peptide with sequence FAVVTTSFL, corresponding to P1A amino acids 43-51. It is presented by H-2Db. P1A vaccination, especially with ChAdOx1 administered intramuscularly and MVA delivered intravenously, protected mice against P1A-expressing EL4 (EL4.P1A) tumor cell challenge. We identified and cloned four TCRs that are specific for the H-2Db-restricted P1A43-51 peptide. T cells transduced with these TCRs recognized EL4.P1A but not MC38.P1A and B16F10.P1A tumor cells, likely due to differences in the proteasome subtypes present in these cells. Adoptive transfer of these T cells in mice bearing EL4.P1A tumors reduced tumor growth and increased survival.We identified the first CD8+ T-cell epitope of the MAGE-type P1A tumor antigen presented in the H-2b background. This opens new perspectives for mechanistic studies dissecting MAGE-type specific antitumor immunity, making use of the wealth of genetically altered mouse strains available in the C57BL/6 background. This should facilitate the advancement of specific cancer immunotherapies.© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.