The cellular response to virus infection is initiated by
recognition of the invading pathogen and subsequent changes in gene expression
mediated by both transcriptional and translational mechanisms. In addition to
well-established means of regulating antiviral gene expression, it has been
demonstrated that RNA interference (RNAi) can play an important role in
antiviral responses. Virus-derived small interfering RNA (siRNA) is a primary
antiviral response exploited by plants and invertebrate animals, and
host-encoded microRNA (miRNA) species have been clearly implicated in the
regulation of innate and adaptive immune responses in mammals and other
vertebrates.