Antiviral defense against filovirus infections: targets and evasion mechanisms

Filoviruses include a number of serious human pathogens, infections with which result in the development of hemorrhagic fevers with high case fatality rates. As for other RNA viruses, viral replication generates both protein and RNA species that can serve as danger signals, leading to the activation of antiviral defense pathways. However, in order to be able to efficiently infect humans these viruses have developed mechanisms that allow them to evade diverse host antiviral defense mechanisms. Consequently, in addition to their functions within the viral lifecycle many filovirus proteins have been shown to have accessory functions involved in the regulation of diverse host pathways. These include those of the type-I interferon response, other pathways involved in dsRNA-sensing, as well as the selective inhibition of interferon stimulated gene activities. Further, filoviruses have developed mechanisms to subvert recognition of infected cells and the generation of neutralizing antibodies. This review focuses on bringing together the evidence to date supporting the existence of diverse mechanisms aimed at regulating these pathways as well as providing details of the mechanisms involved.