The results of a recent experiment in monkeys, published in Nature, suggest that a multimeric nanoparticle vaccine could be effective against coronaviruses that bind to ACE2 receptors.
In a recent study published in the journal Nature, researchers explain how they developed a vaccine that is effective against all the coronaviruses that attach to our ACE2 receptors.
An overly ambitious publication
In their paper, the researchers suggest that their vaccine could be a “pan-coronavirus” vaccine, meaning that it works against all coronaviruses. This team has managed to develop a vaccine that contains a region of the coronavirus spike protein that binds to our ACE2 receptors. While this work represents a proof of concept for the development of a vaccine that protects against multiple coronaviruses, I find the term pan-coronavirus a bit presumptuous. For example, such a vaccine will not be useful against MERS-CoV, since it does not bind to ACE2 and has a different RBD region, nor against other coronaviruses that use different receptors to enter the cell.
A nanoparticle vaccine
Using ferritin in nanoparticles derived from a bacterium, the scientists were able to develop their vaccine, which contains a multimeric region of the spike protein with 200 amino acids. In addition, the vaccine contains agonists of certain key receptors of the innate immune system that are incorporated into aluminum. This vaccine is immunogenic because it stimulates the TL7 and 8 receptors, which will elicit a stronger overall immune response. However, the peptide region in the vaccine is short and remains specific for ACE2-binding coronaviruses.
Duration of immunity: the study’s blind spot
In the experiment, monkeys vaccinated with the nanoparticle vaccine developed significantly more neutralizing antibodies than monkeys vaccinated with RNA or patients with Covid-19. After intranasal or intratracheal infection with coronaviruses, viral genetic material and infectious virus in the lower and upper respiratory tract were absent in the nanoparticle-vaccinated group. Finally, histological analyses also showed a significantly lower accumulation of inflammatory cells in the lungs of this vaccine group.
However, the researchers did not examine one crucial element: the duration of immunity. The issue of duration of immunity remains a mixed one for Covid-19 vaccines. Here, the researchers are studying the immunity of monkeys only for ten weeks after the first injection of a vaccine. It would have been interesting to continue the study to better define the immune protection mediated by this vaccine.
An interesting study, but the results should be treated with caution
The team’s ambition can only be exciting. However, with the current pandemic, it has become very fashionable to exaggerate the results in the field of coronaviruses. Their platform for vaccine development is very interesting but this type of vaccine still needs to prove its efficacy in other tests before it can be approved for human clinical trials to see if it is more beneficial than vaccines already available or in development. Still, it is good that more studies are being done. The more studies we have, the more likely we are to find effective solutions against known and emerging viruses.