Evasion and disruption of innate immune signalling by hepatitis C and West Nile viruses

Signalling pathways leading to type I interferon production are the first line of defence employed by the host to combat viruses, and represent a barrier that an invading virus must overcome in order to establish infection. In this review we highlight the ability of two members of the Flaviviridae, a globally distributed family of RNA viruses that represent a significant public health concern, to disrupt and evade these defences. Hepatitis C virus is a hepatotropic virus, infecting greater than 170 million people worldwide, while West Nile virus is a neurotropic virus that causes encephalitis in humans and horses. While these viruses cause distinct disease phenotypes, the ability of pathogenic strains to modulate the innate immune response is a key factor in influencing disease outcome. Both viruses have evolved unique strategies to target various aspects of type I interferon induction and signalling in order to prevent viral clearance and to promote virus replication.