Departments of NanoEngineering, University of California San Diego, La Jolla, California 92093, United States.
Department of Microbiology and Immunology, and Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth and Dartmouth Hitchcock Health, Lebanon, New Hampshire 03756, United States.
Mol Pharm. 2022 May 2;19(5):1573-1585. doi: 10.1021/acs.molpharmaceut.2c00058. Epub 2022 Mar 25.
In situ vaccination for cancer immunotherapy uses intratumoral administration of small molecules, proteins, nanoparticles, or viruses that activate pathogen recognition receptors (PRRs) to reprogram the tumor microenvironment and prime systemic antitumor immunity. Cowpea mosaic virus (CPMV) is a plant virus that─while noninfectious toward mammals─activates mammalian PRRs. Application of CPMV as in situ vaccine (ISV) results in a potent and durable efficacy in tumor mouse models and canine patients; data indicate that CPMV outperforms small molecule PRR agonists and other nonrelated plant viruses and virus-like particles (VLPs). In this work, we set out to compare the potency of CPMV versus other plant viruses from the Secoviridae. We developed protocols to produce and isolate cowpea severe mosaic virus (CPSMV) and tobacco ring spot virus (TRSV) from plants. CPSMV, like CPMV, is a comovirus with genome and protein homology, while TRSV lacks homology and is from the genus nepovirus. When applied as ISV in a mouse model of dermal melanoma (using B16F10 cells and C57Bl6J mice), CPMV outperformed CPSMV and TRSV─again highlighting the unique potency of CPMV. Mechanistically, the increased potency is related to increased signaling through toll-like receptors (TLRs)─in particular, CPMV signals through TLR2, 4, and 7. Using knockout (KO) mouse models, we demonstrate here that all three plant viruses signal through the adaptor molecule MyD88─with CPSMV and TRSV predominantly activating TLR2 and 4. CPMV induced significantly more interferon β (IFNβ) compared to TRSV and CPSMV; therefore, IFNβ released upon signaling through TLR7 may be a differentiator for the observed potency of CPMV-ISV. Additionally, CPMV induced a different temporal pattern of intratumoral cytokine generation characterized by significantly increased inflammatory cytokines 4 days after the second of 2 weekly treatments, as if CPMV induced a "memory response". This higher, longer-lasting induction of cytokines may be another key differentiator that explains the unique potency of CPMV-ISV.
原位疫苗接种用于癌症免疫治疗，使用小分子、蛋白质、纳米颗粒或病毒在肿瘤内给药，这些小分子、蛋白质、纳米颗粒或病毒激活病原体识别受体 (PRR) 以重新编程肿瘤微环境并引发全身抗肿瘤免疫。豇豆花叶病毒 (CPMV) 是一种植物病毒，虽然对哺乳动物无传染性，但能激活哺乳动物的 PRR。CPMV 作为原位疫苗 (ISV) 的应用在肿瘤小鼠模型和犬科患者中产生了强大而持久的疗效；数据表明，CPMV 优于小分子 PRR 激动剂和其他非相关植物病毒和病毒样颗粒 (VLPs)。在这项工作中，我们着手比较 CPMV 与来自 Secoviridae 的其他植物病毒的效力。我们开发了从植物中生产和分离豇豆斑驳病毒 (CPSMV) 和烟草环斑病毒 (TRSV) 的方案。CPSMV 与 CPMV 一样，是一种具有基因组和蛋白同源性的 Comovirus，而 TRSV 则缺乏同源性，属于 Nepovirus 属。当作为 ISV 在皮肤黑色素瘤的小鼠模型中应用时（使用 B16F10 细胞和 C57Bl6J 小鼠），CPMV 的效果优于 CPSMV 和 TRSV-再次突出了 CPMV 的独特效力。从机制上讲，这种效力的提高与通过 Toll 样受体 (TLR) 的信号转导增加有关-特别是，CPMV 通过 TLR2、4 和 7 进行信号转导。在这里，我们使用敲除 (KO) 小鼠模型证明，所有三种植物病毒都通过衔接分子 MyD88 进行信号转导-其中 CPSMV 和 TRSV 主要激活 TLR2 和 4。CPMV 诱导的 IFNβ 明显多于 TRSV 和 CPSMV；因此，通过 TLR7 信号转导释放的 IFNβ可能是观察到的 CPMV-ISV 效力的区别因素。此外，CPMV 诱导了肿瘤内细胞因子产生的不同时间模式，特征是在每周两次治疗的第二次后 4 天，炎症细胞因子显著增加，就好像 CPMV 诱导了“记忆反应”。这种更高、更持久的细胞因子诱导可能是另一个关键区别因素，解释了 CPMV-ISV 的独特效力。
