Characterization of Dak Nong virus, an insect nidovirus isolated from Culex mosquitoes in Vietnam

Abstract

In this study, we isolated and characterized an insect nidovirus from the mosquito Culex tritaeniorhynchus Giles (Diptera: Culicidae) in Vietnam, as an additional member of the new family Mesoniviridae in the order Nidovirales. The virus, designated "Dak Nong virus (DKNV)," shared many characteristics with Cavally virus and Nam Dinh virus, which have also been discovered recently in mosquitoes, and these viruses should be considered members of a single virus species, Alphamesonivirus 1. DKNV grew in cultured mosquito cells but could not replicate in the cultured vertebrate cells tested. N-terminal sequencing of the DKNV structural proteins revealed two posttranslational cleavage sites in the spike glycoprotein precursor. DKNV is assumed to be a new member of the species Alphamesonivirus 1, and the current study provides further understanding of viruses belonging to the new family Mesoniviridae.

Isolation and characterization of a novel mesonivirus from Culex mosquitoes in China

“…In addition, replicase domains identified in other viruses in the family (Nga et al, 2011;Vasilakis et al, 2013;Zirkel et al, 2013;Warrilow et al, 2014;Lehmann et al, 2015;Kuwata et al, 2013) were also predicted in the Yichang virus ( Fig. 1a, Table 3).…”

“…As shown in Fig. 4, the titers of the Yichang virus were slightly lower than those of the CavV, Hana, Nse, and Meno viruses calculated by TCID50 (Zirkel et al, 2013), and considerably lower than that of the Dak Nong virus (up to 10 11 PFU/mL) measured by plaque assay (Kuwata et, al., 2013) (Table S2). The viral RNA copies in the infected cells were detected by real-time PCR.…”

“…Our study showed that the Yichang virus has the largest genome size in the family Mesoniviridae. Detailed analysis and comparisons of genome organization revealed some notable differences, such as the presence of block insertions of up to 390 nt (130 aa) in the 5′ terminal quadrant of ORF1a compared with the CavV, Hana, Houston, Meno, (Vasilakis et al, 2014;Kuwata et al, 2013), but share low amino acid similarities. For example, the common sequence "SKRKGK" has been detected in BTaV, KsaV, and KPhV at both the N-and C-terminuses and in DKNV on the N-terminus, but only partially ("KGK") found at the N-terminus in the Yichang virus, and not located in the Meno virus at all.…”

“…Nidoviruses consist of approximately 80 virus species with a wide variety of hosts, ranging from crustaceans to mammals (Adams et al, 2016;Cowley and W.P., 2008;De Groot et al, 2012;Siddell et al, 2005). Members of Mesoniviridae have been isolated from various mosquito species in Africa (Côte d'Ivoire), Asia (Vietnam, Thailand, Korea, Indonesia, and China), Australia (Northern Territory), and North America (USA) (Hang et al, 2016;Kuwata et al, 2013;Liu et al, 2013;Nga et al, 2011;Thuy et al, 2013;Vasilakis et al, 2014;Warrilow et al, 2014;Zirkel et al, 2011;Zirkel et al, 2013), thus suggesting a wide geographic distribution. To date, however, only one mesonivirus, the Nam Dinh virus (NDiV), has been reported in China (Zhou et al, 2017).…”

Insect-Specific Viruses

“…Alphamesonivirus-6 is also an independent isolate from Indonesia called Karang Sari virus (KSaV), while Alphamesonivirus-7 was isolated in Thailand and has been described as Kamphaeng Phet virus (KPhV) (Vasilakis and Tesh, 2015;Vasilakis et al, 2014). Currently, three known ISVs have yet to be assigned to species; the unculturable MoumoV, a presumed serotype of Alphamesonivirus-1 isolated in Vietnam called Dak Nong virus (DKNV) (Kuwata et al, 2013), and finally an isolate known as Casuarina virus (CASV) (Warrilow et al, 2014). CASV was isolated in 2010 during mosquito surveillance in Northern Australia, in the Darwin suburb known as Casuarina from a pool of Coquillettidia xanthogaster.…”