The dream-like goal of having universal, timely influenza vaccines has come a step closer, with the discovery that some immune cells can fight the three strains of influenza – perhaps permanently, or for at least several years.
At present, the different types of influenza viruses – strains A, B and C – are introduced into the annual vaccine at different speeds each year to stay ahead of the mutated versions of the virus. If our immune system could fight them all, we would not need to continue vaccinating us so often.
An earlier analysis of people exposed to the H7N9 (bird flu) virus in 2013 had highlighted the potential of some immune cells to care for all three influenza strains. People who had a strong CD8 + T cell response were much more likely to recover.
These CD8 + T cells are often called "killer cells" because of the way they fight threats, as a security force that monitors the doors of our body.
"Our team has been fascinated by killer cells for a long time," said Katherine Kedzierska, principal investigator at the University of Melbourne in Australia. "Our next step was therefore to find out how their protective mechanism worked and if it had potential for an influenza vaccine."
This is where the new research comes in. Mass spectrometry analysis was used to examine 67,000 viral sequences, looking for specific peptides or chemical bonds common to all three strains of influenza in humans.
Special combinations known as epitopes can act as indicators on CT8 + T cells, telling them that a virus has arrived and initiating the order to kill it.
"We have identified the parts of the virus that are shared by all influenza strains and sub-strains capable of infecting humans," said one of the team members, Marios Koutsakos. from the University of Melbourne.
In tests on mice, the team then used these parts of the virus to immunize animals against the flu, and it worked – the levels of infection and inflammation were "remarkably reduced ", according to the researchers.
However, there is still a long way to go before using a ready-to-use all-in-one influenza vaccine. According to the team's estimates, about 54% of the world's population has in its body the type of CT8 + T cells that is suitable for triggering this protective immune response.
That said, this is an important step forward in finding ways to develop better tools for fighting the flu – by having our killer cells detect all incoming strains, instead annual dance around the stumps that we think are most likely to hit.
Strain A is generally associated with influenza pandemics (widely spread in several countries), while strains A and B are associated with annual epidemics (notable increases in a smaller geographical area). Strain C is less common but can cause serious illness in children.
It is important to note that these strains frequently mutate, rapidly passing from sub-strain to sub-strain, which means that even getting a jab every year is not always effective.
A stroke to protect us from all strains at once could prevent thousands of deaths a year. And if this option does not work, we have more to explore: last year, scientists used antibodies found in camelids – camelids, alpacas and llamas – to protect against A strains. and B in the mouse.
"These works highlight the underlying power and versatility of the mass spectrometry approach and we are excited about the future potential of these epitopes for the development of universal vaccines," said one of the researchers, Anthony Purcell of the Monash Biomedicine Discovery Institute in Australia.
The search was published in Immunology of nature.