Yellow Fever Virus Down-Regulates mRNA Expression of SOCS1 in the Initial Phase of Infection in Human Cell Lines.

Flaviviruses are constantly evolving diverse immune evasion strategies, and the exploitation of the functions of suppressors of cytokine signalling (SOCS) and protein inhibitors of activated STATs (PIAS) to favour virus replication has been described for Dengue and Japanese encephalitis viruses but not for yellow fever virus (YFV), which is still of global importance despite the existence of an effective vaccine. Some mechanisms that YFV employs to evade host immune defence has been reported, but the expression patterns ofSOCSandPIASin infected cells is yet to be determined. Here, we show thatSOCS1is down-regulated early in YFV-infected HeLa and HEK 293T cells, whileSOCS3andSOCS5are not significantly altered, andPIASmRNA expression appears to follow a rise-dip pattern akin to circadian-controlled genes. We also demonstrate that YFV evades interferon-beta application to produce comparable viral titres. This report provides initial insight into the in vitro expression dynamics ofSOCSandPIASupon YFV infection and a basis for further investigation intoSOCS/PIASexpression and how these modulate the immune response in animal models.