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

Highlights • First report on a new member in the family Mesoniviridae in Hubei, China. • The newly named Yichang virus appears as a spherical particle with a diameter of ∼80 nm and large club-shaped projections. • The Yichang virus can reach titers up to 107 PFU/ml and produce moderate cytopathic effects (CPE) in C6/36 cells. • Genome and phylogenetic analyses provide evidence of the new isolate being distantly related to other members of Mesoniviridae..
A new insect nidovirus (named Yichang virus) from the family Mesoniviridae was isolated, identified, and characterized from Culex mosquitoes in Hubei, China. Results showed a high number of viral RNA copies (up to 1011 copies/ml) within 48 h in C6/36 cells. In addition, the titers of the Yichang virus reached maximal levels of 107 PFU/mL at 6 d post-infection (dpi). The virus produced moderate cytopathic effects when the multiplicity of infection ranged from 0.001–0.1 at 6 dpi, but did not replicate in mammalian cells. Under electron microscopy, the virion of the Yichang virus appeared as spherical particles with diameters of ∼80 nm and large club-shaped projections. Although subsequent genomic sequence analysis revealed that the Yichang virus had similar protein patterns as those of other mesoniviruses, the nucleotide acids shared less than 20% BLAST query coverage with known viruses in the family Mesoniviridae, and showed a maximum sequence identity of 67% for RNA-dependent RNA polymerase (RdRp). The putative protein sequences showed slightly higher identity (28%–68%), and the most conserved domain was RdRp. Based on the phylogenetic and pairwise evolutionary distance analyses, the Yichang virus should be considered a new species belonging to a currently unassigned genus within the family Mesoniviridae.