Induction and evasion of the type I interferon response by cytomegaloviruses

Cytomegaloviruses represent supreme pathogens in that they are capable of occupying healthy mammalian hosts for life in the face of constant antiviral immune reactions. The inability of the host to eliminate the virus likely results from numerous counteractive strategies employed to disrupt the immune response. The role of type I interferon in the antiviral response has been well documented although only recently have the pathways of induction of this powerful cytokine been described. Cytomegaloviruses have been shown to both induce and be sensitive to the effects of type I interferon. Yet these viruses also possess numerous and varied phenotypes capable of inhibiting not only interferon induction but also interferon signaling and interferon-induced antiviral processes. The balance between induction and evasion of type I interferon responses by cytomegaloviruses is discussed in this review.