Immunomodulation by viruses: the myxoma virus story

Myxoma virus is a poxvirus pathogen of rabbits that has evolved to replicat e successfully in the presence of an active immune response by an infected host. To accomplish this, the virus has developed a variety of strategies t o avoid detection by or obstruct specific aspects of the antiviral response whose consolidated action is antagonistic to virus survival. We describe t wo distinct viral strategies carried out by viral proteins with which myxom a virus subverts the host immune response. The first strategy is the produc tion of virus-encoded proteins known as viroceptors or virokines that mimic host receptors or cytokines. These seek to actively block extracellular im mune signals required for effective virus clearance and produce a local env ironment in the infected tissue that is "virus friendly". The second strate gy carried out by intracellular viral proteins, seeks to retard the innate antiviral responses such as apoptosis, and kinder attempts by the infected cell to communicate with the cellular arm of the immune system. By studying these viral strategies of immune evasion, the myxoma system can provide in sights into virus-host interactions and also provide new insights into the complex immune system.