A new type of experimental vaccine – administered by a simple nasal spray – protects mice against a wide range of respiratory threats: viruses, bacteria and even allergens. This new form of vaccine, called “GLA-3M-052-LS+OVA”, is unlike anything being done today in vaccinology and could, ultimately, pave the way for a “universal” spray against colds, flu, Covid-19 and other infections, summarizes an IFL Science article.
The basic principle of vaccines has remained the same since their creation: to present a fragment of an infectious agent to the immune system so that it learns to recognize it and react more quickly to future exposure. Whether attenuated viruses, purified proteins or messenger RNA vaccines, they are all based on this idea of targeting a very specific pathogen. “It has been the paradigm of vaccinology for the last 230 years”summarizes Bali Pulendran, professor of microbiology and immunology at Stanford, in a press release.
For diseases like measles, mumps or rubella, this strategy works remarkably well: two doses of MMR vaccine are enough to provide lasting protection. But some viruses, such as influenza or SARS-CoV-2, mutate quickly and modify the antigens present on their surface, making existing vaccines less effective over time – hence the need for regular booster shots against these infections.
One vaccine to rule them all
The idea of “universal” or broad-spectrum vaccines is not entirely new: we know, for example, that the BCG vaccine against tuberculosis or certain oral vaccines against polio sometimes confer indirect protection against other diseases. In 2023, Pulendran’s team showed that BCG could trigger both an innate and adaptive response in mice, lasting enough to also protect against Covid-19. This observation led them to imagine a synthetic vaccine capable of reproducing this mechanism without depending on a particular microbe.
The new vaccine therefore does not contain a fragment of influenza virus or coronavirus, but a mixture of molecules which activate innate immunity receptors, these “sensors” which trigger the body’s first defenses. Added to this is a harmless antigen, ovalbumin, an egg protein, which serves here as a lure to recruit T cells and maintain the response over time. In other words, the vaccine does not target a specific pathogen: it reprograms the local immune ecosystem, particularly in the lungs.
Harnessing the power of innate immunity
Normally, innate immunity intervenes very early during an infection, with a rapid but not very specific response, before handing over to adaptive immunity, which is more targeted but slower to take hold. Conventional vaccines rely almost exclusively on this second branch, which explains why it often takes one to two weeks to achieve optimal protection. “What is remarkable about the innate system is that it can protect against a wide range of different microbes”emphasizes Pulendran, provided you manage to keep it active longer than usual.
In the study published in the journal Science, mice were given up to four doses of GLA-3M-052-LS+OVA nasally, one week apart. Three doses were enough to protect them for at least three months against coronaviruses, including SARS-CoV-2 and others responsible for common colds. The researchers observed a 700-fold reduction in the quantity of virus in the lungs, a sign that a very robust innate barrier was being established there, supplemented by the adaptive response to neutralize residual infectious agents.
With these results, the team wondered what this vaccine couldn’t do – and the list is short. Vaccinated mice were found to be protected not only against viruses, but also against two difficult-to-treat respiratory bacteria, Staphylococcus aureus And Acinetobacter baumannii. Even more surprising, when they were exposed to an allergen from house dust mites, they did not trigger the allergic reaction usually observed.
“I think we have a universal vaccine against various respiratory threats”says Pulendran, while recognizing that the transition from mouse to human is still far away. In the most optimistic scenario, it will be another five to seven years before we see a nasal spray of this type reach the clinic, if clinical trials go as planned. Still, imagining a single device capable of protecting us for several months against Covid-19, the flu, colds, certain bacterial infections and even household allergens is already enough to galvanize the scientific community.
