In vivo and in vitro characterization a new isolate of Oya virus from Culicoides spp. and its seroprevalence in domestic animals in Yunnan, China

Author summaryCulicoides are an important component of arbovirus ecology and should be studied and watched over in order to the potential spread of emerging and re-emerging viruses. A novel OYAV isolate (SZC50), isolated from midge samples was sequenced in this study, and the virus's putative host tropism was also tested in vitro, and cell lines derived from pig showed a highly susceptible to OYAV SZC50. Notably, high prevalence of OYAV SZC50 neutralization antibody was found in Yunnan pig serum samples. Moreover, the pathogenicity of OYAV SZC50 in animal models was first shown using mice and chicken embryos. Adult C57BL/6 and suckling mice were shown to be extremely sensitive to OYAV SZC50 infection, in contrast to adult Kunming mice, who can survive following infection. The maximum fatality rate of chicken embryos was 37.5%. In summary, regarding the potential infection risk of OYAV to animal or human, systematic investigation of OYAV, its vector and reservoir in nature should be conducted. Biting midges are one of the most common hematophagous insects. They are capable of transmitting a wide range of arboviruses and have a significant impact on public health and veterinary medicine. Herein, from midge samples collected in 2013 in Yunnan, China, one sample induced a cell cytopathic effect (CPE) in BHK-21, MA104, and PK15 cell lines. Next-generation sequencing data, RACE and PCR determined the genome sequence of the sample and designated as an Oya virus (OYAV) isolate SZC50. Phylogenetic analysis of the sample revealed that it was cluster into viruses from species Orthobunyavirus catqueense. The open reading frames of S, M, and L segment of OYAV SZC50 were closest to those of OYAV SC0806. Moreover, 831 serum samples (736 pigs, 45 cattle, and 50 sheep) were gathered from 13 cities in Yunnan Province to detect neutralizing antibody of OYAV SZC50. A significant proportion of OYAV SZC50 antibody (more than 30%) was found in Yunnan pig populations, with the positive rate of OYAV SZC50 antibody in pigs from Malipo reaching 95%. To determine the pathogenicity of OYAV SZC50, we chose three animal models: specific pathogen-free Kunming mice, C57BL/6 mice lacking the interferon alpha/beta receptor, and chicken embryos. At 5, 6, and 7 days post-infection, all adult and suckling C57BL/6 mice, and specific pathogen-free suckling Kunming mice were dead. Our finding was expanding the knowledge about the infection and pathogenic risk of the neglected virus in the Orthobunyavirus.

Automated summary

A novel Oya virus (OYAV) isolate SZC50 was sequenced from midge samples and its host tropism was tested in vitro, showing high susceptibility in pig-derived cell lines. High prevalence of OYAV SZC50 neutralization antibody was found in Yunnan pig serum samples. Pathogenicity of OYAV SZC50 was demonstrated in animal models, with adult and suckling mice being extremely susceptible and chicken embryos showing a fatality rate of 37.5%.