Mechanisms of viral pathogenesis. Distinct forms of reoviruses and their roles during replication in cells and host.

Recent years have seen a resurgent interest in mechanisms by which viruses cause disease, or viral pathogenesis. Studies of viral pathogenesis often address the capacity ofa virus to cause injuries to cells and tissues; yet, injuries are secondary consequences ofmany fundamental interactions that occur between virus and single cells, as well as between virus and host organism, during infection. For example the tropism ofa virus, or its capacity to grow within particular cells in the host, reflects several of these interactions. Studies ofmore basic aspects of viral infection are therefore critical for understanding viral pathogenesis. We begin this perspective by introducing some general concepts in regard to the replication and structure of animal viruses. Infections with mammalian reoviruses provide useful models for characterizing mechanisms of viral pathogenesis (reviewed in references 1 and 2). Mammalian reoviruses (reoviruses for short) are medium-sized nonenveloped viruses that have a genome consisting of 10 segments of double-stranded (ds)' RNA. In humans, reoviruses are not linked definitively with any disease more severe than a mild enteric or respiratory illness, but in mice and rats they cause a number of disease syndromes involving major organs like brain (3) and heart (4). Studies with reoviruses demonstrate that facts obtained at multiple levels ofinquiry can be integrated in the attempt to understand viral pathogenesis (1, 2). In the major part ofthis perspective, we describe how the structure ofreoviruses relates to their strategy for replication in cells and host organisms and discuss several similarities in this regard between reoviruses and other animal viruses.