In a new study from Yale, researchers report a new coronavirus vaccine that guards one body part especially vulnerable to infection: the nose.
Made only of coronavirus spike protein, the vaccine is part of a one-two punch that could one day protect people from infection.
Dubbed “Prime and Spike,” the strategy relies on an mRNA coronavirus vaccine injection that primes the immune system to recognize SARS-CoV-2, followed by a nasal spray vaccine that shores up defenses at the mucus membranes.
Such a strategy might offer a way to counter the waning effectiveness of current mRNA coronavirus vaccines.
Until now, scientists had not tested nasal vaccines on animals that already had some pre-existing immunity.
This study shows that the intranasal booster induces a really good immune response in the nose and the lungs.
Though current mRNA vaccines work well at preventing severe disease in most people, they weren’t designed to prevent infection, so the virus can still skip from person to person.
In the study, the team focused on the wet, mucus-producing tissue lining the nose and lungs.
A nasal spray vaccine, they thought, could beef up immune security at these sites of viral entry in people who already have immune memory cells due to vaccines or infections.
These “guardians at the gates” could banish any would-be viral invaders before they begin multiplying in the body. That would stop an individual’s infection and prevent the virus from spreading to others.
The team injected mice with one dose of the mRNA vaccine Comirnaty (the Pfizer-BioNTech COVID-19 vaccine). Two weeks later, the researchers squirted the spike protein vaccine into the animals’ noses.
That spray rallied protective antibodies and immune cells to stand guard at the mucus membranes.
The strategy protected the animals from the original SARS-CoV-2 strain, which causes COVID-19.
Roughly 80 percent of mice that received only an injected vaccine containing SARS-CoV-2 spike mRNA died in the two weeks following coronavirus exposure.
In contrast, all the mice that received both the injected vaccine and the nasal booster survived.
Not only do they survive, but their lungs are just so clean. Under the microscope, the scientists saw healthy lung tissue, which looks like a bunch of overinflated balloons.
The team also tested the second type of nasal booster, made with mRNA sheathed in biodegradable polymers. That worked as well as the spike protein vaccine, illustrating the new strategy’s versatility.
A nasal booster may even work in unvaccinated people previously infected with the coronavirus. Iwasaki thinks it’s possible that an infection could effectively prime the immune system.
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The study is posted on bioRxiv.org and was conducted by Akiko Iwasaki et al.
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