 The role of RNA interference in mammalian innate immunity is poorly understood , and relatively little data is available . However , the existence of viruses that encode genes able to suppress the RNAi response in mammalian cells may be evidence in favour of an RNAi @-@ dependent mammalian immune response , although this hypothesis has been challenged as poorly substantiated . Maillard et al. and Li et al. provide evidence for the existence of a functional antiviral RNAi pathway in mammalian cells . Other functions for RNAi in mammalian viruses also exist , such as miRNAs expressed by the herpes virus that may act as heterochromatin organization triggers to mediate viral latency . 
