Producing a successful seasonal flu vaccine requires a bit of fortune-telling about the upcoming season's most popular strains. Each vaccine can target only up to four different flu viruses, of which there are many. If scientists’ predictions about the season’s predominant strains turn out to be wrong, a lot of time and money is wasted—not to mention that the public may be left unprotected from the flu, which can be dangerous even to the young and healthy.
But thanks to mRNA technology, scientists may be one step closer to developing a long-sought universal flu vaccine. In the results of a study published Nov. 24 in Science, a team led by researchers from Perelman School of Medicine at UPenn reported that they had developed an mRNA-based vaccine capable of targeting all 20 known subtypes of the A and B flu virus. Rodents that were immunized with the vaccine produced antibodies to all 20 lineages and were protected from death when exposed to flu strains from each of the different subtypes.
Instead of looking for a novel target, the scientists in the Penn study used mRNA to generate an antibody response to old ones: Hemaglutinin, or HA, proteins, spike-shaped viral proteins that jut out from the surface of the virus and help it infect host cells. Each of the 20 lineages of the A and B flu viruses, the most common types to infect humans, has its own HA protein. press release.
Split virion protein vaccines generate antibodies against HA proteins too, and some of the most promising work on a universal flu vaccine has involved targeting a specific region of the HA protein known as the stalk, which is found in all flu viruses. In this case, the researchers targeted all 20 different HA proteins at once.
The vaccine utilizes the same mechanism of action as the Pfizer and Moderna vaccines against COVID-19. The mRNA serves as blueprints that tell the body’s cells how to produce the HA proteins. When the vaccine is administered, the cells take up the mRNA and begin churning the proteins out. The immune system produces flu antibodies in response, training it to recognize and attack foreign invaders that contain those same proteins.
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