Measures and countermeasures in the modulation of initiation factor activities by viruses

Animal viruses have co-evolved with their hosts for millions of years. During this time, the viruses have developed intricate mechanisms to utilize efficiently their host's metabolic pathways, especially those involving macromolecular synthesis, for virus propagation. In particular, many different viruses modulate and usurp their host's translational machinery for use in the synthesis of their own proteins. However, the infected hosts have developed or adapted cellular mechanisms to interdict virus infection. One of these mechanisms is the interferon response, which entails in part a translational regulatory activity that inhibits virus growth. Viruses, in turn, have devised strategies that act as countermeasures to some aspects of the interferon response. These complex virus-host interactions occur at the level of initiation of translation. Two initiation factors, eIF-2 and eIF-4F, play a significant role in a number of virus-host interactions. The recent advances in our understanding of the mode of action of these translation initiation factors have facilitated research on virus-cell interactions at the level of translation. This review is not intended to summarize the general knowledge in this field, but rather to limit the analysis to several examples of virus-host interactions and to speculate on the interplay between the molecular mechanisms involved in these phenomena.