RNA Technology For A Potential Universal Flu Vaccine
Katalin Karikó and Drew Weissman (University of Pennsylvania) may have discovered a potential universal flu vaccine using RNA technology. They came up with the idea of harnessing messenger RNA to introduce genetic instructions into cells. Tests on mice show that it protects against all known versions of the virus by using the same technique that has already been successful against COVID.
So, How Did They Achieve This?
What they have done is to target all influenza virus subtypes at the same time. They have relied on messenger RNA technology already used in two of the most successful coronavirus vaccines. In essence, this technique introduces the genetic instructions into nanospheres so that the host cell itself manufactures the haemagglutinin (which itself has no viral load). This resulted in 20 vaccines in one. Before putting them all together in one formulation, they tested each nanocapsule separately, to make sure it was effective. The next step was to test them in several groups of mice, hoping that they would all maintain their potency and not cross-react. This is the first time mRNA has been used in the search for a universal vaccine candidate.
As posted in the journal Science, trials in mice showed that they had generated antibodies against all 20 flus and the immunisation lasted at least 4 months. 28 days after vaccination, the scientists infected several groups of these animals with two different subtypes of influenza A. All mice injected with a placebo instead of the vaccine formulation died. However, those actually vaccinated and exposed to the homologous virus did not die and did not even lose weight. Scientists also found no viral load in their lungs. Meanwhile, those immunised and exposed to the rarer virus all became ill and lost weight. However, after seven or eight days most of them recovered, with only 20% dying.
And What Does This Development Mean?
These results mean two things: their vaccine is not sterilising, i.e. it does not protect against infection. But, as with coronavirus vaccines, it protects against the tougher version of the disease. Even against viral strains whose antigen was not included in the flu vaccine.
In short, the key to the success of this universal flu vaccine is that it engages multiple weapons of the immune system. In particular, this flu vaccine elicits different types of antibodies with various functions. Moreover, it also generates different types of T-lymphocyte responses which kill infected cells and activate macrophages to stimulate the action of other immune system cells. Now, current flu vaccines do not protect against flu viruses with pandemic potential. Nevertheless, this vaccine, if it works well in people, would do that.