ABSTRACT
Cytokines are small proteins excreted by cells with the purpose of intercellular communication. Th ey are known to modulate a host’s immune response to infection, particularly viral infections, by recruiting immune cells to the site of infection and signaling defense mechanisms in both infected and un-infected cells. As such, cytokines are part of a strong antiviral defense mechanism by the host and represent a formidable obstacle to the virus surviving in the infected individual. Th ey can also be used by viruses to aid in the replication and persistence of the virus. As a result, while many viruses have evolved diff erent mechanisms to subvert the action of cytokines, others produce homologues of cytokines that assist in their replication and/or pathogenicity. In this chapter, we discuss these diff erent viral responses to cytokines. Hepatitis B and C and infl uenza viruses are used as examples to demonstrate the up-regulation of cytokine production by virus infection and ways in which the virus combats this response. Herpesviruses are used as examples of how expression of viral homologues of cytokines can infl uence the immune response, producing a diff erent response than their cellular counterparts. We review how viral cytokines can assist in fi ghting a host’s immune response as well as benefi t viral replication.
