Scientists are working on a "universal" vaccine that could provide broad protection against numerous influenza strains, including those that could cause future pandemics.
The reason researchers change the vaccine every year is that they want to specifically match the vaccine to the particular viruses that are circulating, such as H1N1. If the vaccine is just a little bit different to the target virus, it is not expected to offer much protection, said principal investigator of the study Jeffery Taubenberger, MD, PhD, at National Institute of Allergy and Infectious Diseases (NIAID).
What they had done was design a strategy where people didn't have to think about matching the vaccine antigen to the virus at all, he added.
In the new study, researchers at the NIAID used a virus-like particle vaccine cocktail that expressed a handful of different subtypes of a key surface protein of the influenza virus: hemagglutinin H1, H3, H5 and H7.
Taubenberger said that the hypothesis was that the presentation of these different viral proteins would stimulate the development of cross-protective immunity that would provide broader protection against multiple subtypes.
The researchers picked the H1 and H3 subtypes because they have been the major cause of human seasonal flu outbreaks since 1918. They chose the H5 and H7 subtypes because they have been the cause of recent bird flu outbreaks and have pandemic potential. This selection also provided a broad representation of hemagglutinins across the phylogenetic tree.
In a series of experiments, they found that 95 percent of mice vaccinated with the investigational cocktail were protected against a lethal challenge with eight different influenza strains expressing seven different influenza A subtypes, compared to only 5 percent of mice who received mock vaccinations.
Additional experiments showed that the vaccine was durable, effective for at least 6 months, and that it worked well in older mice.
The positive initial findings suggest a promising and practical strategy for developing a vaccine with amazing, broad protection, said Taubenberger.
The study appears in the online open-access journal of the American Society for Microbiology, mBio.
