Researchers show promising approach to avian flu vaccine

specific for almost any another influenza virus,” Perez said.

Most currently used vaccines offer protection for a specific animal species against a small range of virus strains. These vaccines take a long time to make (about six months for a vaccine tailored for humans) and they generally cannot be shared between species.

The added difficulty of dealing with avian flu 

Avian flu viruses are so lethal to humans because they are structurally different from human strains. The human immune system does not recognize these viruses and therefore cannot defend the body against them. Because there is little natural immunity to these strains of viruses in humans, a pandemic would likely result if one of these avian flu viruses mutated to spread easily among humans. Because of increased international travel, such a virus would likely spread more easily and quickly than in past influenza pandemics.

Some avian influenza strains, including the H5N1 and H9N2 strains, have shown a limited ability to infect humans who have direct contact with birds, but these virus strains cannot be easily transmitted from human to human. Fifty percent of humans recently infected with the H5N1 strain have died, however, sparking growing concern among world health officials about the potential for this strain to cause a human pandemic.

The Centers for Disease Control and Prevention (CDC) says another strain of bird flu virus could mutate and become easily transmissible between humans, causing another pandemic. No one knows, however, which influenza strain will undergo such a mutation. The H5N1 avian flu virus has recently caused an influenza pandemic in wild and domestic birds in Eurasian and African countries, and may be a likely candidate. “In case of pandemic influenza, we will need a vaccine, but we cannot tell ahead of time what the virus is going to look like,” Perez said. “We may prepare a vaccine before the pandemic occurs, but we don’t know if that vaccine is going to be good enough.”

A universal backbone that could immunize many different animal species, like the one that Dr. Perez has proposed, could be modified quickly to create a vaccine for a specific virus. “A vaccine from this backbone could be deployed much faster than one specifically tailored to humans, because the vaccine would be already available for other animals. All we would have to do is modify it, grow it, and use it in humans. We would not have to remake it from scratch,” he said.

Perez and his team have already shown that a vaccine consisting of a weakened form of the H9N2 virus is capable of protecting chickens, their eggs, and mice against two other lethal forms of the flu virus, including the highly lethal H5N1 avian flu. This vaccine could be administered to immunize wild and domestic birds against avian flu to minimize spread to humans.

Next they will test the vaccine in other mammals like pigs and ferrets, good models for the human immune system. It may be several years before scientists like Perez create an effective vaccine to protect humans against lethal H5N1 or other lethal avian bird flu strains, but the universal influenza backbone will make the eventual creation of that vaccine much easier.