Identification and genetic analysis of a totivirus isolated from the Culex tritaeniorhynchus in northern China.

Totiviridae, a viral family of double-stranded RNA (dsRNA) viruses, contain a single dsRNA genome 4.6-7.0 kb in length. Totiviridae were initially only known to infect fungi and other eukaryotes as well as plants, but an increase in totiviruses has been detected in insects, mosquitoes, and bats. Here, we describe the isolation and characterization of a strain belonging to the family Totiviridae isolated from Culex tritaeniorhynchus in Kenli, China, in 2016. We isolated a totivirus from field-collected mosquitoes in China by cell culture in Aedes albopictus C6/36 cells, identified the virus by morphological observation and complete genome sequencing, and characterized it by phylogenetic analysis. Transmission electron microscopy identified icosahedral, non-enveloped virus particles with a mean diameter of 35-40 nm. The genome was 7612 bp in length, including two open reading frames (ORFs). ORF1 (5058 nt) encodes the capsid protein, while ORF2 (2216 nt) encodes the viral RNA-dependent RNA polymerase (RdRp). Nucleotide and amino acid homology analysis of isolate showed higher levels of sequence identity with isolate CTV_NJ2 (China, 2010) with 94.87% nucleic acid identity and 97.32% amino acid identity. The isolate was designated C. tritaeniorhynchus totivirus KL (CTV-KL). This is the first identification of a totivirus in a C. tritaeniorhynchus in northern China. Analysis of the virus's morphology, characteristic and genome organization will further enrich our understanding of the molecular and biological characteristics of dsRNA Totiviridae viruses.