Innate antiviral responses against Shaan virus infection in HEK293, A549 and MARC-145 cells and limited role of viperin against Shaan virus replication.

The Shaan virus is a new paramyxovirus species recently isolated from an insectivorous bat. Therefore, its replication characteristics remain unclear. We used transcriptome analysis and molecular experiments to examine host cell responses in human A549, HEK293, and monkey MARC-145 cell lines infected with the Shaan virus (ShaV/B16-40). Transcriptome data showed that Shaan virus infection induced innate immune responses associated with defense mechanisms against viral infection in all infected host cells. In real-time RT-PCR, IFN-α, -β and -λ1 were significantly upregulated in response to infection with Shaan virus in A549 and HEK-293 cells. However, the expression of IFN-α and -λ1 did not change in MARC-145 infected cells, while IFN-β significantly increased compared to the control in all the infected cell lines. In DEG analysis, the viperin expression pattern by Shaan virus infection varied depending on the host cell types or their origins. Viperin was highly induced at the RNA level by Shaan virus infection, and viperin protein expression was detected by western blotting. Although viperin, an ISG, has broad inhibitory effects on a range of viral pathogens, viperin knockdown or knock-in in the infected cells indicated that this protein did not markedly affect Shaan virus replication. Interestingly, these effects were independent of CMPK2 expression, which is beneficial for the antiviral effects of viperin. Therefore, the present results suggest that Shaan virus might have a strategy to evade the antiviral effect of viperin or not be significantly affected by viperin.