Small interfering RNA (siRNA) as antiviral therapeutics

RNA interference (RNAi) is a phenomenon of post-transcriptional gene silencing in which dicer cleaves large dsRNA into discrete 21–23 nucleotides double stranded RNA fragments called small interfering RNAs (siRNAs) which join a multinuclease complex called RNA induced silencing complex (RISC) and further degrades the homologous mRNA in sequence specific manner. The dsRNA of several origins including dsRNA intermediates arising from viruses as well as other aberrant RNAs are known to initiate RNAi. siRNA can degrade the mRNA of the virus alone and thus clear viral infection without causing any visible harm to the infected cell. The inhibition of viral replication is extremely sequence specific. Therefore, siRNAs have important therapeutic application as a powerful tool in controlling virus replication. Several reports have so far demonstrated that treatment of cells with siRNAs pre- or post-infection can interfere with virus replication. siRNA has been observed to be effective against RNA viruses with linear or fragmented genomes of either negative or positive polarity as well as DNA viruses.