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One hepatitis virus could help treat infection by another, say Chinese researchers.

In a paper published last month in Virus Research, they demonstrate how the hepatitis delta virus can be made into a 'factory' for agents that prevent the hepatitis B virus from replicating.

Stopping the replication of hepatitis B, which affects most people in developing countries in childhood, effectively cures the infection.

The team of researchers, led by Fuhua Yang at Wuhan University, China, modified hepatitis delta to carry 'molecular scissors' that cut into the genetic material of hepatitis B.

Giving hepatitis B patients the modified hepatitis delta virus reduced levels of the virus in their blood by nearly 90 per cent.

By using a related hepatitis virus, which targets only the liver, the researchers ensured that treatment would be specific to the site of infection.

Recently, another team showed that injecting the 'molecular scissors' alone into the bloodstream of hepatitis B patients helped treat the infection (see Hope for hepatitis B treatment).

However, this method means that if patients are re-infected with hepatitis B, they need another injection.

Yang's team say the modified hepatitis delta acts like a factory for producing the molecular scissors. The virus is modified to contain the DNA code that allows it to produce the molecule whenever a patient is infected with hepatitis B.

Thus, if a patient is re-infected, the factory switches on and produces molecules to stem the new infection.

"This is a very interesting approach for delivering antiviral therapy," says Mark Thursz of the British Association for the Study of the Liver.

"The major hurdle for using [such] therapies is our inability to deliver the [molecule] to infected cells in living animals. Using a modified delta virus is an ingenious approach as the virus will only replicate in the liver cells infected with [hepatitis B virus]."

He cautioned, however, that these results were based on laboratory tests and still need to be confirmed in animals.

Hepatitis B is the most common serious cause of liver infection and a leading cause of liver cancer.

Speaking to SciDev.Net, Abdallah Daar, co-director of the Canadian Programme on Genomic and Global Health, said that this work paves the way for the development of effective and safe antiviral treatment.

Daar added that this method of delivering treatment could be developed for other pathogenic viruses, especially the HIV and hepatitis C viruses.

Reference: Virus Research doi: 10.1016/J.virusres.2005.06.005 (2005)

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