RNA interference as a new strategy against viral hepatitis.

Hepatitis viruses are the leading cause of liver cirrhosis and hepatocellular carcinoma worldwide. Since currently available treatment options against these viruses are limited, there is a need for development of alternative therapies. In this minireview, we concentrate on three hepatitis viruses--hepatitis C virus, hepatitis B virus, and hepatitis delta virus and discuss how RNA interference (RNAi) has been utilized against them. RNAi is a process by which small double-stranded RNA can effectively target a homologous RNA sequence for degradation by cellular ribonucleases. Though RNAi was exploited in the beginning for down-regulating cellular genes, it has recently been demonstrated that this process is equally effective against many types of human and animal viruses including the hepatitis viruses. Both synthetic small-interfering RNAs (siRNAs) and plasmid-based siRNA expression systems have been useful in suppressing the hepatitis viruses. Though this new approach looks promising, problems of nonspecific effects and delivery may need to be addressed before the full therapeutic potential of RNAi against viral infections in patients is realized.