Viruses–exploiters or dependants of the host?

Abstract

Viruses are frequently referred to as the supreme parasites and yet it is now more than 20 years since any paper on this topic was published inParasitology. This deficiency probably reflects the great emphasis placed during the last two decades on those aspects of virology christened by Sir Christopher Andrewes ‘dream virology’ (Andrewes, 1973), namely the molecular and genetic properties of viruses, in contrast to the more clinical and biological aspects of ‘steam’ virology. Many modern virologists select a virus as a convenient model system with which to investigate such things as genetic organization or control of transcription, with little regard for the interaction with the host cell that supports its replication. Paradoxically, it is this very emphasis on the detailed molecular mechanisms of virus replication that has now put us in a better position to understand the relationships between these highly specialized parasites and their host systems than for any other type of parasite. Recent advances in cell biology coupled with an understanding of the molecular basis of viral replicative mechanisms mean that new insight is possible into the interactions of a virus with its host. For example, we are just beginning to appreciate why a virus should infect one individual and not another, or why it should multiply only in certain tissues at certain stages of development of a multicellular organism. Indeed, study of such tropisms may frequently tell us as much about the host cell as about the virus.