Department of Biology and Biotechnology, University of Pavia, via Ferrata, 27100 Pavia, Italy.
Arbovirus and Insect Vectors Unit, Department of Virology, Institut Pasteur, 25-28 Rue du Dr Roux, 75015 Paris, France.
Viruses. 2021 Mar 25;13(4):553. doi: 10.3390/v13040553.
The Asian tiger mosquito is contributing to the (re)-emergence of Chikungunya virus (CHIKV). To gain insights into the molecular underpinning of viral persistence, which renders a mosquito a life-long vector, we coupled small RNA and whole genome sequencing approaches on carcasses and ovaries of mosquitoes sampled 14 days post CHIKV infection and investigated the profile of small RNAs and the presence of vDNA fragments. Since genomes harbor nonretroviral Endogenous Viral Elements (nrEVEs) which confers tolerance to cognate viral infections in ovaries, we also tested whether nrEVEs are formed after CHIKV infection. We show that while small interfering (si)RNAs are evenly distributed along the full viral genome, PIWI-interacting (pi)RNAs mostly arise from a ~1000 bp window, from which a unique vDNA fragment is identified. CHIKV infection does not result in the formation of new nrEVEs, but piRNAs derived from existing nrEVEs correlate with differential expression of an endogenous transcript. These results demonstrate that all three RNAi pathways contribute to the homeostasis during the late stage of CHIKV infection, but in different ways, ranging from directly targeting the viral sequence to regulating the expression of mosquito transcripts and expand the role of nrEVEs beyond immunity against cognate viruses.
亚洲虎蚊是基孔肯雅热病毒（CHIKV）再次出现的原因之一。为了深入了解使蚊子成为终身传播媒介的病毒持续存在的分子基础，我们结合了小 RNA 和全基因组测序方法，对感染 CHIKV 14 天后的蚊子尸体和卵巢进行了采样，并研究了小 RNA 的特征和 vDNA 片段的存在。由于基因组中含有非逆转录病毒内源性病毒元件（nrEVEs），这使得卵巢对同源病毒感染具有耐受性，我们还测试了 CHIKV 感染后是否会形成 nrEVEs。我们表明，虽然小干扰（si）RNAs 均匀分布在整个病毒基因组中，但 PIWI 相互作用（pi）RNAs 主要来源于约 1000bp 的窗口，从中鉴定出一个独特的 vDNA 片段。CHIKV 感染不会导致新的 nrEVEs 的形成，但来自现有 nrEVEs 的 piRNAs 与内源性转录本的差异表达相关。这些结果表明，所有三种 RNAi 途径都有助于 CHIKV 感染后期的体内平衡，但方式不同，从直接靶向病毒序列到调节蚊子转录本的表达，扩展了 nrEVEs 的作用范围，超出了对同源病毒的免疫作用。
