BioEd Online

Virologists in the United Kingdom have begun working on samples of the swine flu virus — influenza A (H1N1) — to understand how it may mutate in the coming weeks. The research will be crucial in developing effective vaccines, they say.

Samples of the virus that had been taken from a swine flu patient in the United States arrived yesterday at the National Institute for Medical Research (NIMR), based in London. Scientists have already started to grow the virus in culture to provide enough material for a battery of tests.

"We don't know yet what features of this virus are enabling human-to-human spread," says John McCauley, an influenza virologist at the NIMR. He points out that, so far, the H1N1 virus seems to be less virulent than the avian flu virus, H5N1.

Scientists have not yet identified anything within the H1N1 virus's genetic makeup that suggests it could mutate into a more virulent form, McCauley says, but "that is not to say it will not emerge".

The researchers are looking for evidence of changes in the proteins on the surface of the virus, known as antigenic drift, as it passes between hosts. Such changes could impact the virus's susceptibility to drugs and could have an impact on the suitability of vaccines that will be developed to tackle it. Patients are currently being treated with the antiviral medicines oseltamivir (Tamiflu) and zanamivir (Relenza).

Alan Hay, director of the World Health Organization's World Influenza Centre at the NIMR, who is leading the work, says that it will be "some months" before a vaccine is available.

"We need to monitor for changes in its sensitivity to antiviral medicines," he adds, "and also see whether, like seasonal human influenza viruses, the virus changes such that any vaccine has to be updated."

Hay says that the UK's National Institute for Biological Standards and Control (NIBSC) in South Mimms has also received samples of the virus and has begun developing a "seed" virus that can be distributed to manufacturers to produce a vaccine.

The NIMR is also preparing reagents that will be used by other labs to detect and diagnose infection. As the lab receives more samples from around the world, it will begin to analyze differences in the viruses from various locations to understand how it changes during human-to-human transmission.