Intracellular DNA sensors regulate innate immunity and can provide a bridge to adaptive immunogenicity. However, the activation of the sensors in antigen-presenting cells (APCs) by natural agonists such as double-stranded DNAs or cyclic nucleotides is impeded by poor intracellular delivery, serum stability, enzymatic degradation and rapid systemic clearance. Here we show that the hydrophobicity, electrostatic charge and secondary conformation of helical polypeptides can be optimized to stimulate innate immune pathways via endoplasmic reticulum stress in APCs. One of the three polypeptides that we engineered activated two major intracellular DNA-sensing pathways (cGAS–STING (for cyclic guanosine monophosphate–adenosine monophosphate synthase–stimulator of interferon genes) and Toll-like receptor 9) preferentially in APCs by promoting the release of mitochondrial DNA, which led to the efficient priming of effector T cells. In syngeneic mouse models of locally advanced and metastatic breast cancers, the polypeptides led to potent DNA-sensor-mediated antitumour responses when intravenously given as monotherapy or with immune checkpoint inhibitors. The activation of multiple innate immune pathways via engineered cationic polypeptides may offer therapeutic advantages in the generation of antitumour immune responses.

细胞内 DNA 传感器调节先天免疫，并可以为适应性免疫原性提供桥梁。然而，双链 DNA 或环核苷酸等天然激动剂对抗原呈递细胞 (APC) 中传感器的激活受到细胞内递送不良、血清稳定性、酶促降解和快速全身清除的阻碍。在这里，我们证明螺旋多肽的疏水性、静电荷和二级构象可以被优化，以通过 APC 中的内质网应激来刺激先天免疫途径。我们设计的三种多肽中的一种通过促进 APC 释放线粒体 DNA，导致效应 T 细胞的有效启动。在局部晚期和转移性乳腺癌的同基因小鼠模型中，当作为单一疗法或与免疫检查点抑制剂一起静脉注射时，这些多肽会产生有效的 DNA 传感器介导的抗肿瘤反应。通过工程化的阳离子多肽激活多种先天免疫途径可能在产生抗肿瘤免疫反应方面提供治疗优势。