Dianke virus: A new mesonivirus species isolated from mosquitoes in Eastern Senegal

Abstract

An increasing number of insect-specific viruses are found around the world. Very recently, a new group of insect-specific viruses, the Mesoniviridae family, was discovered in Africa, Asia, North America and Australia. Here we report the first detection and isolation of a new virus belonging to Mesonivirus genus in Senegal, West Africa. The so-called Dianke virus was detected in 21 species of arthropods trapped in the eastern part of the country. Male individuals were also infected, supporting vertical transmission assertion of insect specific viruses. As described for other mesoniviruses, no viral replication was observed after inoculation of mammalian cells. Viral replication in mosquito cells was blocked at a temperature of 37 °C, highlighting the importance of thermal conditions in Mesonivirus host restriction. Similar to our study, where a diverse range of arthropod vectors were found infected by the new virus, several studies have detected mesonivirus infection in mosquitoes with concerns for human health. It has been shown that dual infections in mosquito can alter viral infectivity. Due to their extensive geographic distribution and host range, as well as their use as potential disease control agents in vector populations, more studies should be done for a better knowledge of arthropod-restricted viruses prevalence and diversity.

Keywords: Eastern Senegal; Insect-Specific virus; Mesonivirus; Mosquito.

Fig. 1

Maximum likelihood tree of the full-length genome of Dianke virus and other mesoniviruses. Scale bar indicate nucleotide substitutions/site.

Fig. 2

Maximum-likelihood tree obtained from amino acid analysis of concatenated conserved protein domains of ORF1ab: 3CLpro-RdRp-HEL1. (Position on Dianke virus genome: 3CLpro: 4167nt-5072nt; RdRp: 9023nt-10387nt; HEL1: 11825nt-12853nt.) Scale bar indicate amino acid substitutions/site.

Fig. 3

Ultrastructure of Dianke virus in C6/36 cells. Bars in all pictures =100 nm. A- Virus particles with smooth surface 55–60 nm in diameter inside cytoplasmic vacuoles (arrowheads). Arrows indicate vesicles 120–250 nm in diameter inside vacuoles, presumably of granular endoplasmic reticulum origin. B- Virus particles with smooth surface 55–60 nm in diameter inside multiple cytoplasmic vacuoles (arrowheads). C- Three particles with smooth surface 55–60 nm in diameter inside small cytoplasmic vacuole (arrowhead) and smaller (40–45 nm in diameter) enveloped particles with dark core inside huge vacuole (star). D- Two types of virus particles inside vacuoles: smooth surfaced 55–60 nm in diameter inside small smooth surfaced vacuole s (arrowheads) and particles ∼ 65 nm in diameter with spikes ∼5 nm long inside an expanded cistern of granular endoplasmic reticulum (asterisk). E- Smooth surfaced virus particles 55–60 nm in diameter inside smooth surfaced cytoplasmic vacuoles (arrowheads) and vesicles 140–160 nm in diameter inside a cistern of granular endoplasmic reticulum (arrow). Cytoplasm contains multiple vesicles 25–30 nm in diameter.

Fig. 4

Maximum likelihood tree of 303bp of the ORF1ab of Dianke virus, the mesoniviruses detected in mosquito pools from the same areas and others published ones. The tree is rooted with CoB76 (Bovine Coronavirus). The sequences from Dianke virus and mosquito isolates from Senegal form a common cluster (99%–100% nucleotide identity) different to the others strains.

Fig. 5

Dianke virus (DKV) in vitro infections in different thermal conditions (blue: 28 °C, orange: 33 °C and grey (37 °C) on Hep-G2 cells (A), RD cells (B), PS cells (C), Vero cells (D) and C6/6 cells (E). The kinetics were prematurely stopped for C6/36 cells at 28 °C and 33 °C as a strong depletion was observed at day 2 and day 3 post-infection respectively.