Pathogenicity analysis of a Chinese Genogroup II Akabane virus strain (TJ2016) in mouse models.

Background: Akabane virus (AKAV) is divided into five genogroups (I to V), and strains of different genogroups exhibit marked differences in pathogenicity. We isolated a genogroup II AKAV strain, TJ2016, in China in 2016, but its virulence remains unknown. The pathogenic potential of other genogroup II strains isolated in China also remains uncharacterized. The objectives of this study were to determine the pathogenicity of TJ2016.

Methods: Kunming or Balb/c mice at 7 days or 8 weeks of age were inoculated with TJ2016 by intracerebral (IC), intraperitoneal (IP), subcutaneous (SC), or intramuscular (IM) routes. Clinical signs, pathological alterations, and AKAV distributions in the inoculated mice were monitored and analyzed.

Results: Virus inoculations by the IC route resulted in 75% ~ 100% mortality of the inoculated mice regardless of the mouse strains or ages. Virus inoculations by the IP route killed 75% to 100% of the suckling mice but killed no adult mice. All the mice inoculated via SC and IM routes survived until the end of the trial. AKAV was detected only in the brains of the mice that died or were euthanized before the end of the experiment. The AKAV antigens were only identifiable within neuronal cells. Brain lesions such as proliferation and infiltration of microglial cells, perivascular cuffing (PVC) of lymphocytes and macrophages, neuronal degeneration/necrosis, vascular dilatation and congestion, etc., were observed only in the mice that died or were euthanized before the end of the experiment.

Conclusions: We characterized the virulence of TJ2016 by inoculating suckling and adult mice via different routes and established experimental mouse models, which holds significant implications for vaccine/drug development and further research on viral pathogenesis.