A step closer to a polyvalent vaccine against …

With SARS-CoV-2 responsible COVID-19We are dealing with a constantly evolving virus whose variants evade the immune defenses we develop after the first infection or vaccination. This possibility of escape obliges us to re-strengthen our immunity by administering booster vaccines, if they can be adapted to the circulating variants.

Other viruses are known for the frequency and significance of their mutations, and these are mutants flu. It infects many animals, making up a huge stock of different viral genomes, and the nature of these genomes, composed of RNA segments, facilitates their evolution, by mutagenesis or by exchange of RNA fragments (recombination). Each year, viruses with altered antigenic characteristics can be put into circulation, and they can infect millions of individuals who have already been vaccinated against previously emerged strains. Thus, protecting the population requires an annual adaptation of the composition of the vaccines, which is carried out before the virus circulation season by WHO experts. The alternation of these seasons between the northern and southern hemispheres makes it possible to identify viral species likely to be responsible for the next pandemic and to include them in vaccines.

For years, research has been done to identify and develop a flu vaccine whose formulation would be stable and capable of protecting against all influenza viruses responsible for epidemics in humans, and which might not have to be re-administered every year.

in a News of December 16, 2020, we present the first encouraging results obtained from a candidate vaccine containing a modified surface protein of the virus, hemagglutinin (HA), which induced an immune response against a portion of this protein, conserved in different viruses. However, the antibodies produced in the trial participants only recognized hemagglutinins belonging to the same group of antigens, indicating the need to further expand the composition of the vaccine to other antigens.

This extension of vaccine composition for all subtypes of the same virus is made possible using messenger RNA technology. Combinations of these molecules encoding slightly different protein fragments are relatively easy to synthesize in order to provide the immune system with all known variations of these antigens. That’s what Scott Hensley and his team did to create a vaccine that delivers antigens to 20 subtypes of influenza A and B virus. The vaccinated mice and rodents produced antibodies against all of the antigens in the formulation. They were protected against infection with the corresponding viruses but also against viruses belonging to other subspecies.

A multivalent influenza vaccine may not be forthcoming, but this work provides a proof of concept: An RNA vaccine could provide protection against viruses with large antigenic disparities by inducing a simultaneous response to multiple antigens.

Besides the question of the true efficacy of such vaccines, which has not yet been answered and which may be difficult to establish in humans if the viruses against which they are developed do not circulate effectively, their acceptability will arise, while they are also intended to protect against infections that remain. virtual.

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