Ken Ishii’s University of Tokyo researchers develop nasal immune adjuvant providing months-Long protection against respiratory viruses

University of Tokyo Researchers Develop Nasal Immune Adjuvant Protecting Mice Against Respiratory Viruses

A nanosized nasal immune adjuvant designated K3-SPG protects mice against respiratory viral infections for months, according to a study scheduled for publication in Science Advances on October 9, 2026. The research, led by Professor Ken Ishii at The Institute of Medical Science, The University of Tokyo, demonstrates that a single nasal dose can trigger innate immune responses providing prolonged cross-protection against pathogens like influenza A and SARS-CoV-2.

In Plain English: The Clinical Takeaway

• Nasal Adjuvant Delivery: K3-SPG is administered directly through the nose, which proved significantly more effective than injections given under the skin or directly into the bloodstream.
• Trained Immunity Mechanism: Rather than attacking a single specific virus, the treatment stimulates the body’s innate immune system—its frontline defense—leaving immune cells primed to respond to multiple threats over time.
• Tolerance Over Replication Block: The treatment helps lung tissue tolerate infection and limits organ damage rather than directly stopping viruses from multiplying inside the body.
• Months-Long Protection: Laboratory tests showed detectable protection in subjects up to 100 days following a single administration, though the defensive response gradually waned over time.

Advanced Analytical Approaches Reveal Immune Response Mechanism

The research team investigated how this prolonged protection develops by utilizing advanced analytical approaches, including single-cell RNA sequencing. Their findings reveal a distinct two-stage cellular response within the respiratory tract. Macrophages drive the early phase of defense, while innate lymphoid cells take over during the later stages.

Certain innate lymphoid cells exhibited alterations down to the chromatin level—the complex DNA-protein structure governing gene activity—pointing to lasting functional changes in cellular behavior. This entire mechanism relies on Toll-like receptor 9 (TLR9), an immune sensor activated by the K3-SPG compound, alongside the inflammatory signaling molecule TNF-α. K3-SPG itself merges a short synthetic DNA fragment known as a CpG oligodeoxynucleotide with a beta-glucan called schizophyllan.

Parameter	Observed Finding
Administration Route	Nasal delivery; superior to subcutaneous or intravenous routes.
Duration of Effect	Protection detectable up to 100 days post-treatment.
Target Pathogens Tested	Influenza A virus and SARS-CoV-2.
Key Receptors & Molecules	TLR9 and TNF-alpha signaling pathways.

Global Pandemic Preparedness and Future Human Clinical Hurdles

The study was co-authored by Asuka Joy Tobuse, a PhD candidate at The University of Tokyo, and Associate Project Scientist Kouji Kobiyama of the University of California San Diego. Commenting on the broader implications of the findings, Professor Ken Ishii stated, “Our research has identified unique mechanisms by which vaccine adjuvants can induce protective innate immunity against respiratory viral infections, suggesting that adjuvants may have potential applications beyond their traditional role in enhancing vaccine responses.”

Because an adjuvant-based preventive strategy does not require prior knowledge of an emerging pathogen’s specific genetic sequence, it could serve as a valuable stopgap during the critical window before pathogen-specific vaccines are manufactured. Professor Ishii noted that such an approach “could potentially provide an additional layer of protection while pathogen-specific vaccines are being developed and manufactured,” aligning with global initiatives like the 100 Days Mission.

Contraindications & When to Consult a Doctor

The study authors caution that these results were demonstrated strictly in animal models and do not establish that K3-SPG can protect humans from respiratory viral infections. Substantial hurdles remain before clinical evaluation can begin, including differences in human TLR9 biology and respiratory drug delivery systems.

References

• The Institute of Medical Science, The University of Tokyo. Research release on K3-SPG nasal adjuvant.
• Science Advances, DOI: 10.1126/sciadv.aeh6480.