Defective interfering genomes and the full-length viral genome trigger RIG-I after infection with vesicular stomatitis virus in a replication dependent manner

Replication compentent vesicular stomatitis virus (VSV) is the basis of a vaccine against Ebola and VSV strains are developed as oncolytic viruses. Both functions depend on the ability of VSV to induce adequate amounts of type-I-interferon. It is therefore important to understand how VSV triggers interferon responses. VSV activates innate immunity via retinoic acid-inducible gene I (RIG-I) a sensor for viral RNA. Our results show that VSV needs to replicate for a robust interferon response. Analysis of RIG-I-associated RNA identified a 4719 nt copy-back defective-interfering (DI) genome and full-length viral genomes as main trigger of RIG-I. VSV stocks depleted of DI genomes lost most of their interferon-stimulating activity. The remaining full-length genome and leader-N-read-through sequences, however, still triggered RIG-I. Awareness for DI genomes as trigger of innate immune responses will help to standardize DI genome content and to purposefully deplete or use DI genomes as natural adjuvants in VSV-based therapeutics.

具备复制能力的水泡性口炎病毒（vesicular stomatitis virus, VSV）是埃博拉病毒疫苗的研发基础，同时VSV毒株也被开发为溶瘤病毒。这两类应用均依赖VSV诱导足量I型干扰素（type-I-interferon）的能力，因此解析VSV触发干扰素应答的机制具有重要意义。VSV通过作为病毒RNA传感器的视黄酸诱导基因I（retinoic acid-inducible gene I, RIG-I）激活固有免疫应答。本研究结果表明，VSV需完成复制过程才能引发强效的干扰素应答。对RIG-I结合RNA的分析显示，4719 nt的回截型缺陷干扰（copy-back defective-interfering, DI）基因组与全长病毒基因组是激活RIG-I的主要触发因素。去除DI基因组的VSV原液，其干扰素刺激活性大幅丧失；但剩余的全长基因组及先导区-N通读序列仍可激活RIG-I。将DI基因组作为固有免疫应答触发因子的认知，将有助于标准化VSV制剂中的DI基因组含量，并有目的地将DI基因组作为天然佐剂应用于基于VSV的治疗方案中。