Estanislao Nistal
Professor of Microbiology at the Faculty of Pharmacy
The study is interesting. It is a continuation of a line of work that these researchers have been developing since a paper they published in 2015. It represents a further step in the strategy to achieve a universal vaccine against influenza.
In this case, the researchers use as a vaccine an artificial protein containing a fragment of the ferritin protein from the bacterium Helicobacter pylori attached to the hemagglutinin stem of the influenza virus. The ferritin fragment organizes itself by assembling to form nanoparticles, which serve as a platform for the hemagglutinin stalk to be stable.
In previous work, the researchers have shown that this artificial protein can induce an effective response to infection in animals. In this work they go a step further and prove that this vaccine construct is able to induce the production of antibodies against different hemagglutinins of group 1 of influenza virus type A, such as hemagglutinins H1, H2 or H5, three very relevant hemagglutinins. H1 is a hemagglutinin present in current viruses. H2 is a hemagglutinin that gave rise to the "Asian flu" pandemic in 1957 and is not present in viruses currently circulating in humans, but has the potential to do so. Finally, hemagglutinin H5 is the hemagglutinin present in avian influenza, with latent pandemic potential. The data presented indicate that, potentially, the vaccine presented has the potential to protect against infection by inducing neutralizing antibodies in vaccinated individuals.
The researchers also present data on the safety and symptoms associated with vaccination, which appear as minor symptoms but with the presence of reactogenicity of different types in about 20% of vaccinated individuals.
The strategy employed uses proteins, it is neither a messenger RNA vaccine, nor an inactivated or attenuated virus vaccine, nor does it use viral vectors for vaccination. It is a vaccine that, in principle, has a very well-defined formulation and with a relative ease of quality control and reproducibility in the manufacture of batches, which may present problems with other types of vaccines. This vaccine tries to stimulate the production of antibodies against the most conserved area of the hemagglutinins of different influenza A viruses that belong to a common group, such as hemagglutinins H1, H2 and H5 or another that, although not tested, can also produce infections in humans, such as H9. Potentially, this vaccine can protect against different influenza viruses that have these hemagglutinins.
The presence of neutralizing antibodies to influenza viruses has traditionally been considered an effective marker of immunization to protect against the virus. However, stimulation of cellular immunity is also a component that is very effective in protecting against the disease. No cell-mediated immunity data are shown in this study. The type of antibodies produced and their production over a year suggests that at least CD4 T cells are stimulated, which assist B cells in their task of antibody production.
Another limitation that the researchers of this study will probably address in the future is to what extent immunization with this vaccine can protect a patient from becoming infected, how long that protection would last, and how many times a patient should be vaccinated to have good protection, as is the case with older people or other particularly susceptible groups, where the virus represents a higher risk.