Researchers Make a Bird Flu Vaccine From Human Cold Virus

Pennsylvania researchers have produced a bird flu vaccine made from a genetically engineered human cold virus and shown that it protected 100% of vaccinated mice and chickens.

Production of a conventional flu vaccine requires months of work and large numbers of fertilized chicken eggs, but the researchers reported Thursday that they prepared their vaccine in 36 days, growing it in a laboratory dish.

The ability to produce a new vaccine so quickly could give public health officials a powerful tool to combat the H5N1 bird flu virus if it should mutate and begin infecting humans widely.

The team is working with the Food and Drug Administration to begin preliminary human tests of the vaccine, said Dr. Andrea Gambotto of the University of Pittsburgh Medical Center, who led the team. He said those trials could begin within weeks.

Gambotto was optimistic that the vaccine would be effective in humans because it is based on a human virus.

His research, conducted in conjunction with scientists from the Centers for Disease Control and Prevention, is scheduled to be published in the Feb. 15 issue of the Journal of Virology and was made available early online.

The Pittsburgh team worked with a human cold virus, called an adenovirus, that had been stripped of the genes that cause a respiratory infection.

Using genetic data from the CDC, they constructed the gene for a bird flu protein called hemagglutinin in the laboratory and added it to the adenovirus. The hemagglutinin protein allows the bird flu virus to bind to cells that it infects and enter them.

The process took 36 days from the time the researchers received the DNA sequence information, Gambotto said.

Mice injected with the vaccine were 100% protected against the bird flu virus, the team reported, and those injected with an unaltered adenovirus died within a few days of being exposed to the bird flu virus.

Studying the mice, the team found that the vaccine produced two types of immunity -- antibodies that block the hemagglutinin and prevent it from binding to cells, and T-cells that attack the invading virus.

“This means that this recombinant vaccine can stimulate several lines of defense against the H5N1 virus, giving it greater therapeutic value,” said microbiologist Simon Barratt-Boyes of the University of Pittsburgh Graduate School of Public Health and a member of the team.

“More importantly, it suggests that even if H5N1 mutates, the vaccine is still likely to be effective against it.”

When the vaccine was given to chickens as a nasal mist, about half the birds were protected from the flu. But when they were injected with the vaccine, they were 100% protected.

“This is a very potent vaccine,” Gambotto said. “The results of this animal trial are very promising.”

The team is not sure why the intranasal administration was not as protective, he added.

So far, the bird flu virus has infected mostly birds, although 152 humans have contracted it and at least 80 have died, according to the World Health Organization. Experts fear the virus will mutate slightly, allowing it to infect humans more easily and leading to a pandemic.

The virus originated in Southeast Asia but has now spread to other areas, including Turkey, Siberia and Kazakhstan.