Targeting of liver tumors by viroimmunotherapy and molecular retargeting of virus-neutralizing antibodies

溶瘤病毒在促进肿瘤抗原的释放和交叉递呈，以及免疫激活肿瘤以抑制随后的检查点方面具有很好的前景。然而，溶瘤病毒是中和抗体的有效诱导者，这严重限制了病毒的传播和治疗效果。在以前的工作中，我们已经开发了一种分子策略来重新定向这些抗病毒抗体来对抗肿瘤，以充分发挥病毒诱导的免疫治疗潜力。为了实现这种中和抗体的重定向(NAB重定向)，我们建立了双功能适配器分子，与腺病毒特异性抗体结合，并促进它们与肿瘤细胞表面的分子靶点的结合。在腺病毒预攻击的荷瘤小鼠中，系统应用这些双特异性接头分子可以抑制肿瘤生长和延长生存期。NAB重定向结合PD-1/PD-L1检查点抑制可增强病毒治疗的抗肿瘤效果，促进长期治愈。此外，在电穿孔诱导的转基因肝癌小鼠模型中，NAB重定向显著延长了生存时间。基于这些先前的结果，我们希望在本项目中研究NAB重定向在肝癌中的分子机制，并希望评估这种干预措施通过给予检查点抑制剂来免疫激活肝肿瘤的可能性。在病毒治疗和NAB重定向的适配器蛋白治疗后，将在皮下和电穿孔诱导的肝癌模型中分析肿瘤组织中的免疫细胞成分(TIL、NK细胞、巨噬细胞和其他髓系细胞)。接下来，我们想将病毒治疗和NAB重定向与重复应用病毒治疗作为当前临床研究的标准方案进行比较。我们将分析肿瘤微环境对这些治疗的适应性及其对抗肿瘤/抗病毒免疫反应平衡的影响。此外，我们想要研究病毒治疗和NAB重定向在β-连环蛋白介导的免疫功能障碍的肝肿瘤中对抗原交叉提呈和T细胞启动的影响。最后，我们希望评估病毒治疗和NAB重定向以及已建立的和新的替代检查点靶点，如TIGIT或CD96在免疫抑制肝纤维化的肿瘤中的作用。这些研究将揭示病毒治疗和NAB重定向有效免疫激活肝癌以抑制检查点的治疗潜力。

Oncolytic viruses are promising agents to promote the release and cross-presentation of tumor antigens, as well as to immune-activate tumors for subsequent checkpoint inhibition. However, oncolytic viruses are potent inducers of neutralizing antibodies which severely limit viral spread and therapeutic efficacy. In previous works, we have developed a molecular strategy to redirect these antiviral antibodies against tumors to fully exploit this virus-induced immunotherapeutic potential. To achieve such retargeting of neutralizing antibodies (nAb-retargeting) we established bispecific adapter molecules which bind adenovirus-specific antibodies and facilitate their binding to a molecular target on the surface of tumor cells. In adenovirus pre-challenged, tumor-bearing mice, systemic application of these bispecific adapter molecules inhibited tumor growth and prolonged survival. nAb-retargeting enhanced the antitumor effect of virotherapy and facilitated long-term cure when combined with PD-1/PD-L1 checkpoint inhibition. Moreover, nAb-retargeting significantly prolonged survival in a murine model with electroporation-induced, transgenic liver cancer. Based on these previous results, we want to study in the present project the molecular mechanisms of nAb-retargeting in liver cancer and want to evaluate the potential of this intervention to immunoactivate liver tumors for administration of checkpoint inhibitors. After treatment with virotherapy and adapter proteins for nAb-retargeting, the immune cell composition (TILs, NK cells, macrophages and other myeloid cells) in tumor tissue will be analysed in subcutaneous and electroporation-induced models of liver cancer. Next, we want to compare virotherapy and nAb-retargeting with repeated application of virotherapy as the current standard protocol in clinical studies. We will analyse the adaptation of the tumor microenvironment to these treatments and its consequences on the balance of antitumoral/antiviral immune responses. Furthermore, we want to investigate the effect of virotherapy and nAb-retargeting on antigen cross presentation and T cell priming in liver tumors with β-catenin-mediated immune dysfunction. Finally, we want to assess virotherapy and nAb-retargeting together with established and novel, alternative checkpoint targets such as TIGIT or CD96 in tumors in the immunosuppressive context of liver fibrosis. These studies will reveal the therapeutic potential of virotherapy and nAb-retargeting to effectively immunoactivate liver cancer for checkpoint inhibition.