Helminth Infection Reactivates Latent γ-herpesvirus Via Cytokine Competition at a Viral Promoter

Mammals are co-infected by multiple pathogens that interact through unknown mechanisms. We found that helminth infection, characterized by the induction of the cytokine interleukin-4 (IL-4) and the activation of the transcription factor Stat6, reactivated murine gammaherpesvirus infection in vivo. IL-4 promoted viral replication and blocked the antiviral effects of interferon-g (IFNg) by inducing Stat6 binding to the promoter for an important viral transcriptional transactivator. IL-4 also reactivated human Kaposi's sarcoma associated herpesvirus from latency in cultured cells. Exogenous IL-4 plus blockade of IFNg reactivated latent murine gammaherpesvirus infection in vivo, suggesting a ‘two-signal’ model for viral reactivation. Thus chronic herpesvirus infection, a component of the mammalian virome, is regulated by the counterpoised actions of multiple cytokines on viral promoters that have evolved to sense host immune status. All of the RNA from virus-pos cells and 50 ng of RNA from virus-neg cells was prepared for RNA-seq using ScriptSeq v2 RNA-seq library preparation kit (Epicentre). Index Primers (Epicentre) were added and samples underwent Duplex-Specific thermostable nuclease (DSN) (Evrogen) treatment to remove ribosomal RNA. Samples were pooled and sequenced on HiSeq.

哺乳动物可同时被多种病原体共感染，各类病原体间通过尚未阐明的机制发生相互作用。本研究结果显示，以诱导细胞因子白细胞介素4（interleukin-4，IL-4）并激活转录因子Stat6为特征的蠕虫感染，可在体内重新激活鼠γ疱疹病毒感染。IL-4可促进病毒复制，并通过诱导Stat6结合至某关键病毒转录反式激活因子的启动子区域，阻断γ干扰素（IFN-γ）的抗病毒作用。IL-4同样可在培养细胞中，将潜伏状态的人卡波西肉瘤相关疱疹病毒重新激活。外源性IL-4联合IFN-γ阻断处理，可在体内重新激活潜伏的鼠γ疱疹病毒感染，这提示病毒重新激活存在“双信号”模型。因此，作为哺乳动物病毒组组成部分的慢性疱疹病毒感染，可通过多种细胞因子对病毒启动子的拮抗作用进行调控——这些病毒启动子已进化出感知宿主免疫状态的功能。本研究对病毒阳性细胞的全部RNA，以及病毒阴性细胞的50 ng RNA，均采用ScriptSeq v2 RNA测序文库制备试剂盒（Epicentre公司）进行RNA测序（RNA-seq）文库构建。随后添加索引引物（Epicentre公司），并对样本进行双链特异性热稳定核酸酶（DSN，Evrogen公司）处理以去除核糖体RNA。将所有样本混合后，在HiSeq测序平台上完成测序。