Le Gall Camille, Cammarata Anna, de Haas Lukas, Ramos-Tomillero Iván, Cuenca-Escalona Jorge, Schouren Kayleigh, Wijfjes Zacharias, Becker Anouk M D, Bödder Johanna, Dölen Yusuf, de Vries I Jolanda M, Figdor Carl G, Flórez-Grau Georgina, Verdoes Martijn
Department of Tumor Immunology, Radboudumc Radboud Institute for Molecular Life Sciences, Nijmegen, The Netherlands.
Department of Tumor Immunology, Oncode Institute, Nijmegen, The Netherlands.
J Immunother Cancer. 2022 Apr;10(4). doi: 10.1136/jitc-2021-004309.
Type 1 conventional dendritic cells (cDC1s) are characterized by their ability to induce potent CD8 T cell responses. In efforts to generate novel vaccination strategies, notably against cancer, human cDC1s emerge as an ideal target to deliver antigens. cDC1s uniquely express XCR1, a seven transmembrane G protein-coupled receptor. Due to its restricted expression and endocytic nature, XCR1 represents an attractive receptor to mediate antigen-delivery to human cDC1s.
To explore tumor antigen delivery to human cDC1s, we used an engineered version of XCR1-binding lymphotactin (XCL1), XCL1(CC3). Site-specific sortase-mediated transpeptidation was performed to conjugate XCL1(CC3) to an analog of the HLA-A*02:01 epitope of the cancer testis antigen New York Esophageal Squamous Cell Carcinoma-1 (NY-ESO-1). While poor epitope solubility prevented isolation of stable XCL1-antigen conjugates, incorporation of a single polyethylene glycol (PEG) chain upstream of the epitope-containing peptide enabled generation of soluble XCL1(CC3)-antigen fusion constructs. Binding and chemotactic characteristics of the XCL1-antigen conjugate, as well as its ability to induce antigen-specific CD8 T cell activation by cDC1s, was assessed.
PEGylated XCL1(CC3)-antigen conjugates retained binding to XCR1, and induced cDC1 chemoattraction in vitro. The model epitope was efficiently cross-presented by human cDC1s to activate NY-ESO-1-specific CD8 T cells. Importantly, vaccine activity was increased by targeting XCR1 at the surface of cDC1s.
Our results present a novel strategy for the generation of targeted vaccines fused to insoluble antigens. Moreover, our data emphasize the potential of targeting XCR1 at the surface of primary human cDC1s to induce potent CD8 T cell responses.
1型传统树突状细胞（cDC1）的特点是能够诱导强烈的CD8 T细胞反应。在努力开发新型疫苗接种策略，尤其是针对癌症的策略时，人cDC1成为递送抗原的理想靶点。cDC1独特地表达XCR1，一种七跨膜G蛋白偶联受体。由于其表达受限和内吞性质，XCR1是介导抗原递送至人cDC1的有吸引力的受体。
为了探索肿瘤抗原递送至人cDC1，我们使用了XCR1结合趋化因子（XCL1）的工程版本XCL1(CC3)。进行位点特异性分选酶介导的转肽反应，将XCL1(CC3)与癌胚抗原纽约食管鳞状细胞癌-1（NY-ESO-1）的HLA-A*02:01表位类似物偶联。虽然表位溶解性差妨碍了稳定的XCL1-抗原偶联物的分离，但在含表位肽的上游引入单个聚乙二醇（PEG）链能够生成可溶性XCL1(CC3)-抗原融合构建体。评估了XCL1-抗原偶联物的结合和趋化特性，以及其诱导cDC1激活抗原特异性CD8 T细胞的能力。
聚乙二醇化的XCL1(CC3)-抗原偶联物保留了与XCR1的结合，并在体外诱导cDC1趋化。该模型表位被人cDC1有效交叉呈递，以激活NY-ESO-1特异性CD8 T细胞。重要的是，通过靶向cDC1表面的XCR1提高了疫苗活性。
我们的结果提出了一种生成与不溶性抗原融合的靶向疫苗的新策略。此外，我们的数据强调了靶向原代人cDC1表面的XCR1以诱导强烈CD8 T细胞反应的潜力。
