Antiviral Immunity: Origin and Evolution in Vertebrates

Antiviral innate responses constitute the first line of defense against viruses until adaptive specific immune responses are mounted. The interferon (IFN) system, which is thought to have originated in early vertebrates, is the hallmark of the innate antiviral mechanisms in vertebrates. This system includes a group of relatively conserved receptors dedicated to the recognition of common viral features. These receptors signal through intermediate signaling molecules, mostly shared among the vertebrate lineage, to induce a wide diversity of IFN molecules that provoke the translation of inducible effector molecules that can directly interfere with viral replication. Despite the high genetic diversity of IFN molecules among vertebrate species, reflecting an evolutionary process in response to the different pathogenic experiences, there is a high degree of conservation in effector molecules, suggesting that the mechanisms to interfere with viral replication at the cellular level are somehow restricted. In the chapter, we provide an overview of what is known in different vertebrate groups about the presence of different molecules and their functionality along the different steps of this complex antiviral network.