A single vaccine could be used to protect chickens, cats and humans against deadly flu pandemics, US researchers have indicated.
Based on a bird flu virus, the vaccine provides protection to birds and mammals against different flu strains and can even be given to birds while they are still in their eggs, allowing the mass vaccination of wild birds.
"The world is experiencing a pandemic of influenza in birds caused by an H5N1 virus. The H5N1 virus also has an unusual expanded host range: not only birds and humans have been infected but also cats, which are usually resistant to influenza. To prepare for a pandemic, it would be ideal to have a vaccine that could be used in multiple animal species," said Professor Daniel Perez from the University of Maryland, USA.
The researchers found that the central genes or 'backbone' of the H9N2 virus that infects guinea fowl can protect birds and mice against highly pathogenic strains of influenza.
They modified the virus to make it less pathogenic and then used it to vaccinate mice. Three weeks after being vaccinated, the mice were infected with the potentially lethal H1N1 virus - the same virus that caused the 1918 Spanish flu pandemic.
All the vaccinated mice survived with no signs of disease. Vaccinated mice also survived infection with the deadly H5N1 bird flu virus, again showing no signs of disease.
"Our results show that the H9N2 backbone vaccine can be used to protect mice against two different, highly pathogenic strains of influenza. We chose genes from H9N2 influenza for the vaccine because the virus can infect many different animals, including chickens, mice and pigs," said Perez.
"A very important limitation in the current design of flu vaccines is that they are usually species specific. Our approach involves a universal backbone that can be used in several different species, including humans," Perez added.
The researchers also found that this live attenuated virus provided effective protection when it was administered to birds before they had hatched.
"By vaccinating eggs against influenza, we could protect wild bird species as well as domestic chickens against pandemic flu strains, limiting the spread of disease to humans," said Perez.
The study is published in the November issue of the Journal of General Virology.