Chinese scientists announced on Tuesday (Aug 22) that an international research team had made a breakthrough in the search for a SARS cure by identifying the "channel" through which the virus enters the human body.

The team, including scientists from the Chinese mainland, Hong Kong and Germany, had isolated the 3a protein that helped the entry and release of the severe acute respiratory syndrome-associated corona virus (SARS-CoV).

The protein functioned as an ion channel, which explained the highly pathogenic nature of the SARS virus, said team leader Sun Bing, a researcher with the Institute Pasteur of Shanghai, which is a Sino-French cooperative project under the Chinese Academy of Sciences.

The discovery of 3a protein's function could lead to the development of new methods to treat the pandemic disease.

The protein first helped the SARS virus enter uncontaminated, healthy cells and then helped release viruses reproduced inside the cells, Sun explained.

The 3a protein was the first ion channel confirmed to promote the entry of the SARS virus, but whether it was the only channel for the virus release remained unknown, Sun said.

Sun's team found the 3a protein forms a potassium sensitive channel, which can be efficiently inhibited by barium. After a SARS virus contaminates a cell, the protein is expressed. Once the expression of 3a protein is inhibited, the virus release will be weakened significantly and virus reproduction will be discontinued in contaminated cells.

Generally a virus entered a host cell and then disrupted genes inside and reproduced itself, Sun said. The reproduced virus was then released to contaminate more cells.

Given sufficient time to develop immunity, the human body could kill new viruses through its immune system. However, the SARS virus rapidly attacked the respiratory system and caused the failure of important organs before the immune system could counterattack.

The ion channel for virus entry and release would be an ideal target for medicines yet to be developed.

SARS first broke out in southern China's Guangdong Province in November 2002 and spread to 24 provinces, autonomous regions and municipalities on the Chinese mainland. The outbreak caused alarm around the world, with 32 nations and regions reporting cases.

It was reported that the infectious disease claimed more than 700 lives worldwide, including at least 349 on the Chinese mainland.

The World Health Organization has identified SARS-CoV as the causative agent for the disease. However, the development of the disease remains unclear, and medicines or vaccines have yet to be developed.

Sun said his team's research findings had been carried in the latest issue of the Proceedings of the National Academy of Science of the U.S., or PNAS.

Editor: Wing