Common vaccines, such as the flu shot and COVID-19 vaccine, are typically administered through an injection, and work by triggering a full system-wide immune response against the target pathogen. Although these vaccines are effective in building up protective antibodies, they work through the entire immune system rather than specific areas of infection, such as the respiratory system, which produces its own local immunoglobulin A (IgA) antibodies on mucosal surfaces. Researchers at Yale University are now testing a new vaccine that is administered intranasally in order to locally jumpstart the respiratory immune system and potentially offer better protection against viral variants.
Mucous membranes such as those inside the nose, mouth, lungs and stomach can provide a natural barrier against airborne and foodborne pathogens by producing B cells that secrete locally-working IgA antibodies. Previous work has demonstrated the protective effect that these IgA-producing cells have against intestinal pathogens. Building on this previous knowledge, the researchers designed a protein-based vaccine that would trigger an IgA immune response and administered it either intranasally or through an injection to laboratory mice.
When the vaccinated mice were exposed to various strains of influenza viruses, the researchers found that those that received the nasal vaccine were better protected against the respiratory virus than those that received injections. Furthermore, the nasal vaccine proved to be more effective than injections against a variety of flu strains rather than just the strain the vaccine was meant to protect against. The researchers showed that the vaccine established IgA-secreting cells in the lungs of mice that received the nasal vaccine, but not in the lungs of those that received the vaccine through injection. This study was published in the journal Science Immunology.
“The best immune defense happens at the gate, guarding against the viruses trying to enter,” said Akiko Iwasaki, the senior author on the paper.
Iwasaki added that if the vaccine were proven to be safe and effective in humans, it could be used in conjunction with current mRNA vaccines in order to provide added immune system reinforcements against SARS-CoV-2 and variants such as Delta and Omicron.