Juliette Bougon, University of Alberta

Juliette Bougon1, Julia May1, Adil Mohamed1, Tim Footz1, Lindsay Maslin1, Janet Wu1, Janelle Nordin1, Dirk Taal1, Ryan Noyce1, Maya Shmulevitz1, Troy Baldwin1 and V3P consortium 1: University of Alberta – Department of Medical Microbiology and Immunology (MMI)

Fighting & Responding

Respiratory viral pandemics have accelerated vaccine development, yet questions remain about how administration routes shape protective immunity. Limited effectiveness of many intramuscular influenza vaccines has renewed interest in intranasal strategies. In this study, we compare vaccination routes using a novel HA/NP–expressing Poxviridae platform to define shared and distinct protective mechanisms. Mice (C57BL/6 and BALB/c) were immunized intranasally (IN) or intramuscularly (IM) and subsequently challenged with an H5-expressing PR8 strain to assess protection efficacy. Vaccine-induced immune responses were characterized by spectral flow cytometry profiling myeloid, T, and B cell populations. In parallel, pulmonary and splenic cells were stimulated ex vivo with NP and a newly identified HA immunodominant peptide to quantify CD8⁺ T cell cytokine production. Preliminary findings suggest that IN vaccination provides superior protection compared with IM delivery. This improved survival correlates with enhanced pulmonary immunity, including increased lung-resident T cells and greater tissue infiltration. Conversely, IM vaccination elicited stronger systemic responses, with higher circulating T cells, granzyme B–expressing cells, and memory B cells. Interestingly, ex vivo stimulation is stronger for IM CD8⁺ T cells, with higher TNFα and IFNγ production; however, IN vaccination may induce lung-resident T cells mediating site-specific pulmonary immunity and potentially driving early protection, a hypothesis to be explored in future studies. Taken together, these results suggest that this novel platform may shape immune localization and functional quality in a route-dependent manner. In particular, intranasal delivery promotes pulmonary immunity, translating into early survival and informing next-generation vaccine design against respiratory viral threats.