Dynamics of Orthoflavivirus Reproduction and Cytokine Responses in the A549ACE2 and HEK-293T Cells

Orthoflaviviruses circulating in the Russian Federation that include the tick-borne encephalitis virus (TBEV), the Powassan virus (POWV), the Omsk hemorrhagic fever virus (OHFV), and the West Nile virus (WNV) are of significant concern. Development of a suitable in vitro model is crucial for studying mechanisms of viral replication and immune response to the infection. In the present study, A549ACE2 and HEK-293T cells widely employed in biotechnology and biomedicine were used. Dynamics of the infectious and non-infectious viral particle accumulation and production kinetics of the IFN-α, IFN-γ, TNF-α, IL-6, IL-8, IL-10, IL-4, and IL-18 cytokines in these cells at different infectious doses of the viruses were studied. Notably, only WNV caused a cytopathic effect in the cells, which was observed starting 48 h postinfection with a high dose of the virus. The cells showed similar dynamics of multiplication of the studied orthoflaviviruses, which depended on the dose of infectious virus. As expected, the HEK-293T cells exhibited deficiency in the immune response: production of only a low level of IFN-α was observed in response to the WNV infection and decrease in the IL-8 level was detected in response to infection with all studied orthoflaviviruses. In contrast, the A549ACE2 cells demonstrated presence of the IFN-α, TNF-α, IL-6, IL-18, and anti-inflammatory IL-4 cytokines after infection. Furthermore, the detected levels and timing of cytokine production depended on both the virus and the viral dose.