Translational Immunotherapy/Targeted Therapy Teams, The Institute of Cancer Research, London, UK.
Imperial College London, London, UK.
J Immunother Cancer. 2022 Mar;10(3). doi: 10.1136/jitc-2021-004410.
Combination herpes simplex virus (HSV) oncolytic virotherapy and BRAF inhibitors (BRAFi) represent promising immunogenic treatments for BRAF mutant melanoma, but an improved understanding of the immunobiology of combinations is needed to improve on the benefit of immune checkpoint inhibitors (ICI).
Using a BRAF-driven murine melanoma model, we tested the immunogenicity of HSV/BRAFi in immunocompetent C57BL mice. In addition to standard FACS analysis, we used the 'Timer of Cell Kinetics and Activity' system, which can analyze the temporal dynamics of different T cell subsets. This immune data was used to inform the selection of ICI for triple combination therapy, the effects of which were then further characterized using transcriptomics.
Adding BRAFi treatment to HSV improved anti-tumor effects in vivo but not in vitro. Immune characterization showed HSV or dual therapy led to fewer intratumoral Treg, although with a more activated phenotype, together with more effector CD8 +T cells. Tocky analysis further showed that HSV/BRAFi dual treatment reduced the Tocky signal (reflecting engagement with cognate antigen), in both Treg and conventional subsets of CD4+, but not in CD8 +cells. However, a higher percentage of Treg than of conventional CD4 +maintained frequent engagement with antigens on treatment, reflecting a predominance of suppressive over effector function within the CD4 +compartment. The only T cell subset which correlated with a reduction in tumor growth was within Tocky signal positive conventional CD4+, supporting their therapeutic role. Targeting CD25 high, antigen-engaged Treg with a depleting anti-CD25 ICI, achieved complete cures in 100% of mice with triple therapy. Transcriptomic analysis confirmed reduction in Foxp3 on addition of anti-CD25 to HSV/BRAFi, as well as increases in expression of genes reflecting interferon signaling and cytotoxic activity.
Combination HSV/BRAFi is an immunogenic therapy for BRAF mutant melanoma, but cannot fully control tumors. Dual therapy results in changes in T cell dynamics within tumors, with relatively maintained antigen signaling in Treg compared with conv CD4+. Antigen-engaged CD4 +effectors correlate with tumor growth control, and depletion of Treg by addition of an anti-CD25 ICI, releasing suppression of conventional CD4 +effectors by Treg, enhances survival and activates immune signaling within tumors.
单纯疱疹病毒（HSV）溶瘤病毒联合 BRAF 抑制剂（BRAFi）治疗 BRAF 突变黑色素瘤具有潜在的免疫原性，但为了提高免疫检查点抑制剂（ICI）的疗效，需要进一步了解联合治疗的免疫生物学。
我们使用 BRAF 驱动的小鼠黑色素瘤模型，在免疫功能正常的 C57BL 小鼠中测试 HSV/BRAFi 的免疫原性。除了标准的 FACS 分析外，我们还使用了“细胞动力学和活性计时器”系统，该系统可以分析不同 T 细胞亚群的时间动态。这些免疫数据用于指导选择 ICI 进行三联组合治疗，然后进一步使用转录组学来描述其作用。
BRAFi 治疗联合 HSV 可提高体内抗肿瘤作用，但体外无此作用。免疫特征表明，HSV 或双重治疗可导致肿瘤内 Treg 减少，尽管其表型更活跃，同时伴有更多的效应性 CD8 +T 细胞。Tocky 分析进一步表明，HSV/BRAFi 双重治疗可降低 Treg 和 CD4 +的传统亚群中 Tocky 信号（反映与同源抗原的结合），但在 CD8 +细胞中无此作用。然而，在治疗过程中，与肿瘤生长相关的 Treg 比例高于 CD4 +的传统亚群，这反映了 CD4 +亚群中抑制功能优于效应功能。唯一与肿瘤生长减少相关的 T 细胞亚群是 Tocky 信号阳性的传统 CD4 +细胞，支持其治疗作用。用耗竭性抗 CD25 ICI 靶向 CD25 高、抗原结合的 Treg，可使三联治疗的 100%小鼠完全治愈。转录组学分析证实，加入抗 CD25 后，HSV/BRAFi 可降低 Foxp3 的表达，并增加反映干扰素信号和细胞毒性活性的基因表达。
HSV/BRAFi 联合治疗是一种针对 BRAF 突变黑色素瘤的免疫原性疗法，但不能完全控制肿瘤。双重治疗会导致肿瘤内 T 细胞动力学发生变化，与传统 CD4 +相比，Treg 中的抗原信号相对保持不变。与肿瘤生长控制相关的是抗原结合的 CD4 +效应物，通过添加抗 CD25 ICI 耗尽 Treg，可释放 Treg 对传统 CD4 +效应物的抑制作用，从而增强肿瘤内的存活和激活免疫信号。
