[CHIBA, JAPAN] South African scientists have developed a new approach that could potentially lead to a powerful medicine to treat the Hepatitis B virus.

Hepatitis B (HBV) is a major threat in poor countries that cannot afford to buy the HBV vaccine. Each year about 1 million people with chronic HBV die from cirrhosis of the liver or liver cancer, according to the World Health Organization.

Traditionally, HBV is treated with anti-viral drugs, but this approach only reduces the amount of virus in the body, rather than eliminating it.

Sergio Carmona and colleagues from the University of Witwatersrand in South Africa have explored a gene therapy to fight HBV.

The scientists reported their results at the 2006 conference of International Society for Cell & Gene Therapy of Cancer, held in Chiba, Japan last week (13-15 October).

Previous studies have developed a technology called RNA interference (RNAi), where a molecule or group of molecules stops viruses or tumour cells replicating themselves and spreading infection.

Carmona and colleagues genetically modified a virus called adenovirus, which naturally exists in human bodies and is commonly harmless, to make it carry some RNAi compounds.

The modified adenoviruses can infect the particular site of the liver cells where HBV replicates, but the adenoviruses themselves do not replicate. Upon infecting the liver cells, the RNAi compounds on the adenoviruses stop HBV replication.

The researchers found that this approach can prevent up to 90 per cent of HBV replication in mice.

The team is now preparing for human clinical trials of the RNAi-based approach.

"The RNAi method offers exciting promise as a therapeutic means of inhibiting HBV replication either alone or in combination with therapies that are already licensed," Carmona says.

Liu Yanxin, a senior molecular biologist from Beijing-based Peking Union Medical College, agrees the approach has potential for inhibiting virus replication.

"But more research on the safety of the method as well as its efficiency in various subtypes of HBV infections are needed," Liu told SciDev.Net.