Mucosal immune responses to live attenuated influenza vaccine in young adults

Compared to intramuscular vaccines, nasally administered vaccines have the advantage of inducing local mucosal immune responses that may block infection and interrupt transmission of respiratory pathogens1. Live attenuated influenza vaccine (LAIV) is commonly used in children2, but its effectiveness declines with age3. This may be attributed to the gradual accumulation of homo- or hetero-subtypic immunity that blocks vaccine replication necessary to induce protective responses3, 4. Despite its demonstrable efficacy against influenza in children, correlates of protection for LAIV remain elusive5. Studying young adult volunteers we found that LAIV induced distinct, compartmentalized, antibody responses in the mucosa and blood. LAIV also induced mucosal IL-33 release in the first 8 hours post-inoculation and distinct CD8+ and cTfh T cell activation profiles. Mucosal antibodies are induced separately from blood antibodies and may provide a simple and novel correlate of protection for mucosal vaccination. Overall design: 40 adult volunteers were inoculted with live attenuated influenza vaccine, and nasal inferior turbinate samples collected by nasal curettage using RhinoPro curettes at baseline (up to 7 days prior to inoculation) and 72 hours post inoculation.