US researchers developing faster, tougher bird flu vaccine
(AFP)
Updated: 2005-10-12 14:04

US researchers say they have come one step closer to developing a tougher, more flexible bird flu vaccine that could be produced significantly faster than traditional vaccines and would also protect against future virus mutations.

The vaccine would be delivered by a harmless virus that could be developed in tissue cultures rather than chicken eggs.

This would guard against concern that eggs could become scarce during a pandemic and also allows for significantly faster and larger production cycles, said lead researcher Suresh Mittal at Purdue University in Indiana.

"Traditional egg-based vaccines take about six months," Mittal said in a telephone interview. "Typically the cell-based vaccine can be produced in large quantities in a couple of months."

Mittal said his research will be ready to be sent for peer review by the end of the month. Given heightened concerns about a possible pandemic he expects it could be published by November, allowing for clinical trials to begin shortly thereafter.

That may not be soon enough, warned Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota.

"The problem is they're a long way off," he said, adding that there are simply not enough facilities in the world to produce the volume of vaccines required if the virus crosses with human flu strains to become a lethal and highly contagious new disease.

The H5N1 avian flu virus has been found mainly in 10 Southeast Asian countries and has so far infected 112 people, of whom 60 have died, according to the World Health Organization.

So far it has only spread from birds to humans, but health officials warn that human-to-human infection may not be far off.

Strains of the virus appear to have spread to birds as far as Turkey and Colombia and the WHO warns that a pandemic could sweep across the globe in a matter of months, killing millions of people.

While there is at least one vaccine which has proven successful in early clinical trials, Mittal said his cell-based vaccine could be more effective because it would be able to adapt to mutations, which occur frequently in flu viruses. That means health officials won't have to wait months before a new vaccine is available.

"One advantage is speed. The other advantage is the immune response - the body is reacting to the virus in a more natural fashion," he said. "The third advantage is this type of vaccine might provide better protection."

The harmless virus - called an adenovirus - carries a modified virus gene which causes cells to produce similar proteins to those they would produce if they were infected. The body then reacts by producing antibodies that attack such foreign proteins.

This response is generally stronger than that produced by a vaccine with a "killed" virus that does not infect cells, he said.

The adenoviruses do not require as long of an incubation period as traditional vaccines and systems already exist to produce large quantities of adenoviruses because they are used in clinical trials for gene therapy, Mittal said.