A new vaccine strategy could make flu shots cheaper, safer, and easier to produce. Using synthetic messenger RNA instead of proteins purified from viruses, German scientists have shown they can protect mice, ferrets, and pigs against influenza. “This is a very interesting new approach,” says Hans-Dieter Klenk, a virologist at the University of Marburg in Germany who was not involved in the work.
Now, most flu vaccines consist of hemagglutinin and neuraminidase, the two proteins covering the surface of the virus. To produce these molecules, the three predominant influenza strains are cultured in fertilized chicken eggs or, increasingly, in cell culture. Virus is then harvested and broken up so that the two proteins can be purified.
How well a given strain grows in either eggs or cells is hard to predict, however, and producing enough virus for millions of vaccine doses takes many months every year.
Now, scientists at the Friedrich-Loeffler-Institute (Germany’s Federal Research Institute for Animal Health), and biotech company CureVac in Tübingen have developed a new approach. By injecting synthetic mRNA into the skin of mice, the researchers coaxed the animals’ cells into producing the virus protein themselves. This elicited an immune response that later protected the animals from infection with otherwise lethal doses of influenza virus.