Researchers at The Jackson Laboratory in the US state of Connecticut have developed a promising antibody “cocktail” that could serve as the basis for a universal therapy against the influenza A virus (IAV).

This family of viruses causes seasonal epidemics on a regular basis and is associated with the risk of pandemics, especially during the spread of bird flu strains.

The findings off the study were published in the medical journal Science Advances.

Traditional flu vaccines are created taking into account the most likely strains and are based on neutralizing antibodies. But the flu virus is extremely variable, and its mutations quickly make vaccines less effective.

The new approach, however, uses neutralizing antibodies that target a stable region of the virus, the M2e proton channel. Such element of the virus remains virtually unchanged in various strains. These antibodies do not directly block the virus, but help the immune system activate defense mechanisms and destroy infected cells.

As part of the study, researchers tested three different antibodies. They were used separately, in pairs, and all together as a “cocktail.” Tests on mice with various strains of flu, including the deadly avian variant H7N9, showed impressive results: when this “cocktail” was injected, all the mice survived even if the treatment was not started immediately, but a day or two after infection. With a delayed injection, the effectiveness remained very high—about 80 percent.

Separately, the resistance of the therapy to the emergence of "escape mutants"—viral variants that usually bypass the defenses of the immune system. This makes the strategy particularly promising, because it is the virus’ ability to rapidly evolve that makes flu such a difficult problem.

The researchers tested this “cocktail” also on mice with weakened immune systems. The results were comparable, which enable to use this therapy in immunocompromised people, for whom flu is a particular threat.

At this phase, the study is limited to animal tests. But the researchers emphasize that if clinical trials are successful, this new antibody “cocktail: could complement—or even partially replace—seasonal flu vaccines.