Whole-Genome Sequencing and Structure Study of Three Biting-Insect-Associated Viruses (Yunnan Orbivirus, Guangxi Orbivirus, and Yongshan Totivirus) Isolated in Yunnan, China.

Yunnan Province is an area in China with a major prevalence of biting arthropods (including mosquitos, ticks, and Culicoides) and arboviruses including dengue virus (DENV), bluetongue virus (BTV), and epizootic hemorrhagic disease virus (EHDV). Therefore, attempts to isolate and detect arboviruses are frequently conducted in Yunnan during the past decades. In this study, a total of three viral strains/isolates (LF6-4, LF3-1, and LF6C2) previously isolated from cattle, goat, and Culicoides in Lufeng County, Yunnan Province, between 2022 and 2023 were used for whole-genome sequencing, phylogenetic analysis, and electron microscopic analysis. As a result, these viruses were completely sequenced. Strain LF6-4 isolated from cattle was identified as a putative Serotype 1 Yunnan orbivirus (YUOV). Strain LF3-1 isolated from goats was identified as Guangxi orbivirus (GXOV), and it is the first GXOV strain isolated from this animal. Isolate LF6C2 represented the first totivirus strain isolated from Culicoides. The viral particles of all three isolates collected from the infected C6/36 cells were all icosahedral particles with a diameter of approximately 45 nm. However, MDBK cells yielded YUOV and GXOV particles with diameters of approximately 75 nm. This difference may be caused by different viral proliferation/package modes in the different types of host cells.