Identification and RNAi Profile of a Novel Iflavirus Infecting Senegalese Aedes vexans arabiensis Mosquitoes

Abstract

The inland floodwater mosquito Aedes vexans (Meigen, 1830) is a competent vector of numerous arthropod-borne viruses such as Rift Valley fever virus (Phenuiviridae) and Zika virus (Flaviviridae). Aedes vexans spp. have widespread Afrotropical distribution and are common European cosmopolitan mosquitoes. We examined the virome of Ae. vexans arabiensis samples from Barkédji village, Senegal, with small RNA sequencing, bioinformatic analysis, and RT-PCR screening. We identified a novel 9494 nt iflavirus (Picornaviridae) designated here as Aedes vexans iflavirus (AvIFV). Annotation of the AvIFV genome reveals a 2782 amino acid polyprotein with iflavirus protein domain architecture and typical iflavirus 5’ internal ribosomal entry site and 3’ poly-A tail. Aedes vexans iflavirus is most closely related to a partial virus sequence from Venturia canescens (a parasitoid wasp) with 56.77% pairwise amino acid identity. Analysis of AvIFV-derived small RNAs suggests that AvIFV is targeted by the exogenous RNA interference pathway but not the PIWI-interacting RNA response, as ~60% of AvIFV reads corresponded to 21 nt Dicer-2 virus-derived small RNAs and the 24–29 nt AvIFV read population did not exhibit a “ping-pong” signature. The RT-PCR screens of archival and current (circa 2011–2020) Ae. vexans arabiensis laboratory samples and wild-caught mosquitoes from Barkédji suggest that AvIFV is ubiquitous in these mosquitoes. Further, we screened wild-caught European Ae. vexans samples from Germany, the United Kingdom, Italy, and Sweden, all of which tested negative for AvIFV RNA. This report provides insight into the diversity of commensal Aedes viruses and the host RNAi response towards iflaviruses.

Mosquito-Associated Viruses and Their Related Mosquitoes in West Africa

“…Regarding the nonpathogenic MSVs, the most classified ones (e.g., Gouleako and Nounane virus) were identified in Côte d’Ivoire. However, Odorna virus and Aedes vexans iflavirus were recently identified in Ghana and Senegal respectively [ 136 , 149 ].…”

“…They have a monopartite, linear, ssRNA(+) genome of about 9.7–12 kb [ 147 ]. These viruses can be divided into three main groups: those that are maintained in an arthropod–vertebrate cycle and strictly depend on each other are called dual-host flaviviruses [ 148 ]; those that are limited to vertebrates with an unknown arthropod relationship are known as vertebrate-specific flavivirus [ 149 ]; and those that replicate only in insect cell lines are termed insect-specific flaviviruses [ 148 , 150 , 151 ]. Flaviviruses and flavivirus-specific antibodies detected in West Africa are shown in Figure 2 .…”

“…This explains why mesoniviruses are said to have a broad host range and geographical distribution. Another recent and novel mosquito-specific iflavirus isolated from Aedes vexans mosquitoes in Senegal is Aedes vexans iflavirus [ 149 ]. Ae.…”

Uncovering the Worldwide Diversity and Evolution of the Virome of the Mosquitoes Aedes aegypti and Aedes albopictus

“…For examination of the viral RNAi response, we used a previously described pipeline [ 47 ]. Briefly, adapter and quality trimmed fastq files (>18 nt) from small RNA datasets were mapped to virus genomes using Bowtie2 (Galaxy Version 2.3.4.3) [ 48 ] and coverage calculated as above.…”

Prevalence of a Novel Bunyavirus in Tea Tussock Moth Euproctis pseudoconspersa (Lepidoptera: Lymantriidae)

“…RNA viruses are increasingly reported in various invertebrate species ( Shi et al 2016 , Niu et al 2019 , Zhang et al 2019 ). Some viruses can not cause pathology that are isolated from asymptomatic insect hosts, which have been reported to be beneficial to their hosts ( Xu et al 2014 , Parry et al 2020 ).…”