Protective role of interferon-induced Mx GTPases against influenza viruses

Mx proteins are interferon-induced large GTPases with antiviral activities. They inhibit a wide range of viruses by blocking early stages of the replication cycles. Importantly, Mx GTPases also suppress the growth of highly pathogenic influenza A viruses, such as currently circulating H5N1 viruses or the pandemic H1N1 virus strain of 1918. In this paper, the authors review the properties of Mx proteins and discuss their role in host defence against highly pathogenic viruses. The authors further suggest that mammalian Mx proteins may normally provide a barrier against zoonotic transmission of avian influenza A viruses and that acquired resistance to the antiviral action of human MxA may be one factor, among many others, that facilitates the spread of pandemic strains in human populations. The presently available evidence suggests that Mx proteins of domestic chickens lack the ability to efficiently combat avian influenza viruses known to cause devastating infections in this species. The deliberate introduction of an antivirally active Mx gene originating from resistant birds or mammals may confer some degree of protection and thus stop commercial birds from serving as amplifying hosts of potentially pandemic influenza virus strains.