Teams of French and Chinese scientists have discovered the intricate structure of an important component of the H5N1 virus — a move they hope will provide a new approach for developing antiviral drugs.

Two papers published in Nature describe the structure of a part of RNA polymerase, an important H5N1 virus enzyme that is responsible for virus replication in host cells.

Both use a technique called X-ray crystallography — which reveals how atoms are arranged in a structure — to determine the exact structure of a section of the enzyme called PA. This section could be an important target for new drugs as the inhibition of PA's activity will stop the virus from replicating.

Stephen Cusack, a senior scientist at the European Molecular Biology Laboratory and lead researcher of the French team, told SciDev.Net that knowing the structure of PA will make it easier to find and improve agents to inhibit the region.

And the resulting drugs could be better than current drugs because the region they would target on PA doesn't mutate as fast as those targeted by drugs such as oseltamivir, say the Chinese researchers, led by Rao Zihe of the Laboratory of Structural Biology at Tsinghua University, China.

Before these studies, it was difficult to find an effective way of inhibiting the H5N1 virus because it mutates so rapidly, says Dongli Pan, a research fellow at the US-based Harvard Medical School.

"Little was known about which part of the enzyme is responsible for the process, let alone the exact active site of the process," he adds.

Scientists in Hong Kong recently revealed that Yuzhu, a traditional Chinese medicine, could inhibit the activity of H5N1 virus (see Anti-H5N1 rice could protect poultry, say scientists), which suggests that the antiviral structures may exist in nature.

But new drugs could take years to develop since they would need toxicity and animal testing and human clinical trials before they could enter the market.

Source: SciDev Net
Date: 02 March 2009