Angelova Assia, Pierrard Kristina, Detje Claudia N, Santiago Estelle, Grewenig Annabel, Nüesch Jürg P F, Kalinke Ulrich, Ungerechts Guy, Rommelaere Jean, Daeffler Laurent
Program Infection, Inflammation and Cancer, Clinical Cooperation Unit Virotherapy (F230), German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany.
Program Infection, Inflammation and Cancer, Division Viral Transformation Mechanisms (F030), German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany.
Pathogens. 2023 Apr 17;12(4):607. doi: 10.3390/pathogens12040607.
The oncolytic rodent protoparvoviruses (PVs) minute virus of mice (MVMp) and H-1 parvovirus (H-1PV) are promising cancer viro-immunotherapy candidates capable of both exhibiting direct oncolytic activities and inducing anticancer immune responses (AIRs). Type-I interferon (IFN) production is instrumental for the activation of an efficient AIR. The present study aims at characterizing the molecular mechanisms underlying PV modulation of IFN induction in host cells. MVMp and H-1PV triggered IFN production in semi-permissive normal mouse embryonic fibroblasts (MEFs) and human peripheral blood mononuclear cells (PBMCs), but not in permissive transformed/tumor cells. IFN production triggered by MVMp in primary MEFs required PV replication and was independent of the pattern recognition receptors (PRRs) Toll-like (TLR) and RIG-like (RLR) receptors. PV infection of (semi-)permissive cells, whether transformed or not, led to nuclear translocation of the transcription factors NFĸB and IRF3, hallmarks of PRR signaling activation. Further evidence showed that PV replication in (semi-)permissive cells resulted in nuclear accumulation of dsRNAs capable of activating mitochondrial antiviral signaling (MAVS)-dependent cytosolic RLR signaling upon transfection into naïve cells. This PRR signaling was aborted in PV-infected neoplastic cells, in which no IFN production was detected. Furthermore, MEF immortalization was sufficient to strongly reduce PV-induced IFN production. Pre-infection of transformed/tumor but not of normal cells with MVMp or H-1PV prevented IFN production by classical RLR ligands. Altogether, our data indicate that natural rodent PVs regulate the antiviral innate immune machinery in infected host cells through a complex mechanism. In particular, while rodent PV replication in (semi-)permissive cells engages a TLR-/RLR-independent PRR pathway, in transformed/tumor cells this process is arrested prior to IFN production. This virus-triggered evasion mechanism involves a viral factor(s), which exert(s) an inhibitory action on IFN production, particularly in transformed/tumor cells. These findings pave the way for the development of second-generation PVs that are defective in this evasion mechanism and therefore endowed with increased immunostimulatory potential through their ability to induce IFN production in infected tumor cells.
溶瘤啮齿动物细小病毒（PVs）——小鼠微小病毒（MVMp）和H-1细小病毒（H-1PV）是很有前景的癌症病毒免疫治疗候选药物，它们既能展现直接的溶瘤活性，又能诱导抗癌免疫反应（AIRs）。I型干扰素（IFN）的产生对激活有效的AIR至关重要。本研究旨在阐明PV调节宿主细胞中IFN诱导的分子机制。MVMp和H-1PV在半允许性正常小鼠胚胎成纤维细胞（MEFs）和人外周血单个核细胞（PBMCs）中触发IFN产生，但在允许性转化/肿瘤细胞中则不会。MVMp在原代MEFs中触发的IFN产生需要PV复制，且独立于模式识别受体（PRRs）——Toll样（TLR）受体和视黄酸诱导基因样（RLR）受体。（半）允许性细胞（无论是否转化）的PV感染导致转录因子NFĸB和IRF3的核转位，这是PRR信号激活的标志。进一步的证据表明，（半）允许性细胞中的PV复制导致双链RNA（dsRNAs）在细胞核中积累，将其转染到未感染的细胞中时能够激活依赖线粒体抗病毒信号（MAVS）的胞质RLR信号。这种PRR信号在PV感染的肿瘤细胞中被阻断，在这些细胞中未检测到IFN产生。此外，MEF永生化足以显著降低PV诱导的IFN产生。用MVMp或H-IPV对转化/肿瘤细胞而非正常细胞进行预感染可阻止经典RLR配体诱导的IFN产生。总之，我们的数据表明天然啮齿动物PVs通过一种复杂机制调节受感染宿主细胞中的抗病毒固有免疫机制。特别是，虽然啮齿动物PV在（半）允许性细胞中的复制参与了一条不依赖TLR/RLR的PRR途径，但在转化/肿瘤细胞中，这一过程在IFN产生之前就被阻断了。这种病毒触发的逃避机制涉及一种病毒因子，它对IFN产生具有抑制作用，尤其是在转化/肿瘤细胞中。这些发现为开发第二代PVs铺平了道路，这些第二代PVs在这种逃避机制中存在缺陷，因此通过它们在受感染肿瘤细胞中诱导IFN产生的能力而具有增强的免疫刺激潜力。
