RNA Interference Functions as an Antiviral Immunity Mechanism in Mammals

Viral Defenses In plants and invertebrates, RNA interference (RNAi) functions as an innate antiviral defense mechanism. Viruses that infect plants and invertebrates have evolved viral suppressors of RNAi (VSRs) that disable the RNAi pathway. Whether mammals use RNAi as a defense against viruses has been less clear (see the Perspective by Sagan and Sarnow ). Li et al. (p. 231 ) and Maillard et al. (p. 235 ) studied mammalian cell lines and baby mice productively infected with RNA viruses and observed the production of virus-derived small RNAs (vsRNAs). When the putative VSR proteins of the infecting viruses were disabled, host RNAi-derived vsRNAs were much increased and the viruses were rapidly cleared and unable to mount a full-blown infection. Thus, RNAi also has an innate antiviral function in mammals.