Sars patients can provide therapy

Sars is caused by a coronavirus

People infected with the Sars virus can be treated by taking antibodies from others who have recovered from the disease, research shows.

The Swiss researchers who have developed the technique believe it could be adapted for use against other infections too.

It may provide a fast method to combat emerging diseases, and, perhaps, biological attacks.

The research is published in the journal Nature Medicine.

Our approach produces protective antibodies that would provide immediate protection against the Sars virus. Dr Antonio Lanzavecchia

Sars emerged in China in 2002, and spread through many countries, killing about 800 people.

Scientists are currently working on a vaccine, but there is still no good treatment for the disease, which is caused by a virus related to those that cause flu.

The new approach, dubbed passive immune therapy, uses the immune cells of patients who have successfully fought off the disease.

A team from the Institute for Research in Biomedicine in Bellinzona, Switzerland, focused on a type of immune cell called a B cell.

These cells make the proteins, or antibodies, that target the Sars virus for attack by the immune system.

The researchers exposed the cells to cocktail containing the Epstein-Barr virus and a short stretch of synthetic DNA that mimics some of the DNA found in bacteria and viruses.

This not only triggered the cells to start dividing indefinitely, but also sped up the process, effectively creating a high-powered antibody factory.

Other researchers have also tried to produce antibodies, but they have tried to do this by cloning genes, rather than whole immune cells.

More potent

Lead researcher Dr Antonio Lanzavecchia told BBC News Online his method produced antibodies that were 1,000 times more potent. It also produced a range of 35 different antibodies, all able to attack the Sars virus.

A team from the US National Institute of Allergy and Infectious Diseases then tested the most effective of these antibodies in mice and found they prevented the virus from multiplying in the respiratory system.

Dr Lanzavecchia said: "At present there is no immunological treatment for Sars, and a vaccine may take several years to produce.

"Our approach produces protective antibodies that would provide immediate protection against the Sars virus.

"It could be used to protect people who have come into contact with the infection, such as health workers, and those who are about to go into areas where the virus has taken hold.

"We hope the same technique could be used against all infectious diseases and toxins."

Dr Lanzavecchia said he was particularly hopeful it could be applied to HIV, whose ability to generate many different variants poses a major problem for doctors.

A spokeswoman for the Health Protection Agency said: "We welcome this research, which is important in the incremental process of understanding how we can use an immune response to protect others from viral infections such as Sars.

"Further work is still needed and we will watch this area with interest."