Researchers have created a new 'universal' flu vaccine, which is directed against type A influenza viruses. It was created using portions of two important molecules generated by the H3N2 virus. These molecules, the extracellular domain of matrix 2 (M2e), and the stalk protein, have not changed much over time, while other parts of influenza type A viruses frequently evolve.
Reporting in npj Vaccines, researchers have used an adult mouse model to show that vaccination with the M2e-stalk protein created broad immunity against different strains of influenza type A. In this study, the animal model produced immunoglobulin G (IgG) antibodies against both the stalk and M2e portions. The animals were also able to clear a flu infection.
Until now, vaccination using portions of the stalk protein from H3 viruses has been challenging and ineffective. During the 2014–2015 flu season, there were many variants of H3N2, and vaccine efficacy against them was only six percent.
"The M2e-stalk protein, for the first time, could be easily produced in bacterial cell cultures at high yields and was found to confer protection against heterologous and heterosubtypic cross-group subtype viruses (H1N1, H5N1, H9N2, H3N2 and H7N9) at similar levels in adult and aged mice," said senior study author Dr. Sang-Moo Kang, a professor at the Institute for Biomedical Sciences at Georgia State. "These results provide evidence that M2e-stalk genetic fusion proteins can be produced in a large scale at low cost and developed as a universal influenza A virus vaccine candidate for young and aged populations."
There are two other types of flu that sicken people. Influenza type C only causes mild illnesses. The other, influenza type B, typically infects millions of people every year around the world. These type B viruses are classified differently, and there are not subtypes. Instead, they are grouped as lineages, either B/Yamagata or B/Victoria. New type B variants don't arise as often as new type A variants.
Influenza type A is the only type that causes pandemics, and type B has typically been thought to cause milder illness. So, most research and public health data has focused on influenza type A, so there aren't as many statistics for type B. However, studies have indicated that it type B is a substantial burden on public health.
Right now, the trivalent seasonal flu vaccine includes immunity against a lineage of type B flu. More work will be needed before we have a universal vaccine that is also effective against type B, and additional research will be needed to confirm this work in humans. It is also not yet known how long immunity from this new type of 'universal' vaccine would last in people.