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During an experimental infection, chickens immunized with the vaccine developed by professors Steve Bourgault and Denis Archambault ― respectively from the departments of chemistry and biological sciences at UQAM ― and their colleagues were 100% protected, with no clinical signs of the disease, no viral shedding and no pathological lesions.
“These are impactful results and we didn’t necessarily expect that,” admitted Mr. Bourgault.
The new vaccine preparation tested by the researchers was designed using nanoparticles that contained an amino acid sequence conserved between viral strains, called M2e, in addition to a recombinant protein, the globular HA1 part of the HA protein.
The result was an immunity that researchers call “sterilizing,” meaning that viral transmission from one individual to another is completely annihilated given the absence of viral shedding.
What is more, the new vaccine is practically “universal”, since the strain of H5N1 that was used to infect the chickens was very far, from a phylogenetically point of view, from that which was used to prepare part of the vaccine material.
It can therefore be assumed that the vaccine would be able to counter any variant of the H5N1 influenza virus, even if it has obviously not yet been tested against dozens of different variants.
In slightly clearer terms, the vaccine developed in left field proved effective against an infection that came straight out of right field.
“That’s really the difficulty we have with influenza,” recalled Steve Bourgault. “It’s a virus that mutates a lot, that changes regularly. Often the immune systems are directed against the parts of the virus that change a lot.”
The best example, he added, is the annual flu vaccine in humans. “It’s a prediction: we take three or four strains that we predict will be the most present, we hope to have targeted well, but if we’re even a little wrong, the vaccine could be much less effective,” Bourgault recalled.
The formulation of the new vaccine also uses portions of the virus that change a lot, but combines them with portions that hardly change and that the immune system can therefore recognize during each new infection.
One of the advantages of our formulation is the ability to induce a strong response against the component [du virus] which generally induces a lesser response.
Steve Bourgault, professor and researcher
The H5N1 virus is a regular headline-grabber. Over the years, it has required the destruction of millions of poultry, both here and around the world, to slow its spread. It has recently been detected in domestic animals such as cats and dogs, but also in seals, walruses and even cows.
Human infections remain exceedingly rare and usually occur in individuals who have been in contact with carrier animals. The case fatality rate in infected humans varies between 52% and 62%.
That being said, a first human infection without apparent animal contact was discovered in recent days in Missouri. Several scientists warn that it is now only a matter of time before the virus acquires the ability to jump from one human to another.
“The vaccine has been tested in mice and chickens, so we can’t really extrapolate to other species,” warned Steve Bourgault. “For the moment, it’s really a veterinary vaccine and not a human one.”
The researchers remain convinced, however, that they have found a very important piece of the H5N1 puzzle, and only the next few years will tell us how far their discovery will take us.
“Now we understand a little better how we can neutralize the secretion of the virus than before it spread,” said Bourgault. “What are the key elements of a robust and protective immune response? There are obviously veterinary applications in the short term, but in the long term it could provide solutions for human vaccines.”
Researchers from the National Centre for Foreign Animal Diseases in Winnipeg and the Institut national de recherche pour l’agriculture, l’alimentation et l’environnement in France also participated in the work. The scientists were supported by grants from the International Development Research Centre and the Bill & Melinda Gates Foundation.
The findings of this study were published in the scientific journal NPJ Vaccines-Nature.
