Pathogenic viruses: smart manipulators of the interferon system

Vertebrate cells are equipped with specialized receptors that sense the presence of viral nucleic acids and other conserved molecular signatures of infecting viruses. These sensing receptors are collectively called pattern recognition receptors (PRRs) and trigger the production of type I (alpha/beta) interferons (IFNs). IFNs are secreted and establish a local and systemic antiviral state in responsive cells. Viruses, in turn, have evolved multiple strategies to escape the IFN system. They try to avoid PRR activation, inhibit IFN synthesis, bind and inactivate secreted IFN molecules, block IFN-activated signaling, or disturb the action of IFN-induced antiviral proteins. Here, we summarize current knowledge in light of most recent findings on the intricate interactions of viruses with the IFN system.