Yale researchers have uncovered new insights into nasal vaccine boosters, showing their effectiveness in enhancing immune defenses in the respiratory tract without adjuvants. This novel approach could transform how we fight respiratory diseases.
Traditional vaccines targeting respiratory diseases are primarily administered through intramuscular injections, but a new study from Yale University suggests an innovative alternative: nasal vaccine boosters.
Yale researchers have discovered that nasal vaccine boosters can trigger robust immune responses in the respiratory tract without the need for adjuvants — ingredients often used to enhance immune responses but which can cause side effects like inflammation — enhancing the fight against diseases like COVID-19.
These findings, published in Nature Immunology, are poised to revolutionize vaccine development.
“Our study shows how a simple viral protein antigen can boost respiratory tract immune responses against viruses,” senior author Akiko Iwasaki, the Sterling Professor of Immunobiology at Yale School of Medicine (YSM), said in a news release. “These data imply that viral proteins in nasal spray may be used as a safe way to promote antiviral immunity at the site of viral entry.”
In their study, the research team first administered a traditional mRNA COVID-19 vaccine to mice via intramuscular injection. Following this, a nasal booster was given, which notably lacked adjuvants. The results were significant.
“We call this vaccine strategy ‘prime and spike,’ which is where the mice were intramuscularly primed with mRNA vaccines followed by a nasal boosting with unadjuvanted spike protein,” added first author Dong-il Kwon, a postdoctoral fellow in Yale’s Department of Immunobiology.
The “prime and spike” approach utilizes a traditional vaccine shot to stimulate initial immunity, followed by a nasal spray containing coronavirus-derived spike proteins. This strategy was found to be highly effective, prompting a local immune response exactly where it is most needed — the respiratory tract.
After the initial shot, immune cells were activated in the mice’s lymph nodes. Following the nasal booster, these cells relocated to the lungs, producing immunoglobulin A (IgA), a crucial antibody in defending the respiratory system from infections. The nasal booster also activated memory CD4+ helper T cells, which acted as natural adjuvants.
The study found that only the nasal booster induced a strong local immune response, unlike intramuscular boosters, which did not generate much IgA or activate significant immune protection in the lungs.
“These findings help explain why nasal boosters do not require adjuvant to induce robust mucosal immunity at the respiratory mucosa and can be used to design safe and effective vaccines against respiratory virus pathogens,” Kwon added.
Routine COVID-19 vaccines typically don’t induce sufficient IgA in the respiratory tract, meaning vaccinated individuals can still contract and transmit the virus.
The new Yale method, however, holds promise for more effective prevention of infection at the virus’s main entry point.
“Understanding how this safe and simple nasal booster promotes protective mucosal immunity will make it easier to develop this approach for human use in the near future,” Iwasaki added.
Source: Yale University