'Universal' nasal-spray vaccine protects against viruses, bacteria and allergens in mice

What if a single vaccine could offer protection against a range of disease-causing bacteria, common allergens and respiratory viruses? A new mouse study highlights an experimental vaccine that could potentially offer that elusive "universal" protection.

As it's been tested only in lab animals, the vaccine must still pass a number of trials in people before it can be proven safe and effective.

The new study, published Thursday (Feb. 19) in the journal Science, describes a nasal-spray vaccine that works differently than most vaccines.

Conventionally, vaccines train the immune system to recognize a specific antigen, such as a protein on a virus's surface. The immune system then trains cells to remember and attack that antigen if they encounter it. This results in a robust, but fairly narrow immune defense — one which can be thwarted if the target antigen mutates over time.

Some scientists are working on vaccines that target antigens that are "highly conserved" between viral strains, meaning the antigen doesn't change much over time and looks similar from virus to virus. Such shots could potentially target many flu viruses or many coronaviruses at once, for example. But the scientists behind the new nasal-spray vaccine took a different approach: Rather than targeting only the "adaptive" immune system, which remembers specific antigens, it also revs up the innate immune system, a generic, first-line defense.

"What's remarkable about the innate system is that it can protect against a broad range of different microbes," senior study author Bali Pulendran, a professor of microbiology and immunology at the Stanford University School of Medicine, said in a statement.

The idea of a vaccine activating both innate and adaptive immunity is not completely new. It's well known that the tuberculosis vaccine, called Bacillus Calmette-Guérin (BCG), triggers this dual protection. In fact, because of that effect, scientists tested whether BCG could offer broad protection against COVID-19 in the early days of the pandemic.

Pulendran and colleagues had previously studied the BCG vaccine in mice and found that the shot caused immune cells in the lungs to spew specific signals. These signals prompted innate immune cells in the lungs to stay active for several months, rather than calming down after just days.

The new nasal-spray vaccine — called GLA-3M-052-LS+OVA — works by mimicking those special signals. It also contains a harmless egg-protein antigen that helps summon the right immune cells to the lungs. The team found that mice given three doses of the vaccine over three weeks were protected against SARS-CoV-2 (the virus that causes COVID-19) and other coronaviruses, the bacteria Staphylococcus aureus and Acinetobacter baumannii, and an allergen from house dust mites for at least three months afterward.

When exposed to these germs and the allergen, vaccinated mice were protected by the primed innate immune response and also quickly mounted an adaptive immune response against the insults. By comparison, unvaccinated mice fared much worse — in response to viruses and bacteria, they showed higher lung inflammation, weight loss and risk of death, and in response to allergens, they had more pronounced allergic reactions and mucus buildup.

"This is a really exciting piece of research," Daniela Ferreira, a professor of respiratory infection and vaccinology at the University of Oxford who was not involved in the study, told BBC News. It could "change how we protect people from common coughs, colds and other respiratory infections" if the results are confirmed in human studies, she said.

Pulendran also emphasized that, so far, the tests of the vaccine have been in lab animals and more work is required to translate the research to humans.

"If it ultimately proves safe and effective in humans, the potential impact could be transformative: simplifying seasonal vaccination and improving readiness for emerging respiratory threats," Pulendran told Genetic Engineering and Biotechnology News. Pulendran thinks two doses of the vaccine would likely be protective in people, according to the Stanford statement.