Abstract Rationale Tissue-resident memory T (TRM) and B (BRM) cells in the lung are essential for long-term protection against respiratory pathogens. However, the mechanisms by which the lung microbiome influences the development and maintenance of these populations following mucosal vaccination remain poorly defined. Methods We utilized an intranasal adenovirus-based influenza nucleoprotein (Ad-NP) vaccine and analyzed TRM/BRM responses in the lung at 35 days post-vaccination. To evaluate the fluctuation of local microbiota, 16S rRNA sequencing of lung and fecal samples was performed following intranasal (i.n.) or intramuscular (i.m.) vaccination. Antibiotics (Abx) were administered via intratracheal (i.t.) or oral (o.g.) routes either early (days 14-20) or late (days 28-34) following i.n. vaccination to modulate microbiome composition. Lung TRM frequency, cytokine profiles, and influenza-specific antibody responses were subsequently evaluated. Results Intranasal Ad-NP vaccination induced robust and sustained lung TRM cells with elevated IFN-γ production and increased TGF-β expression in total lung cells. 16S sequencing revealed distinct microbiome signatures in both lung and feces after i.n. vaccination. Abx treatment confirmed compartment-specific microbiome disruption; i.t. Abx altered lung but not fecal microbiota, whereas o.g. Abx affected only the gut. Remarkably, late i.t. Abx treatment enhanced lung TRM and memory B-cell populations, and increased influenza NP-specific antibody titers from bronchoalveolar lavage fluid (BALF). However, o.g. Abx showed no influences to lung TRM and memory B cell responses. These mice demonstrated improved survival and faster weight recovery following lethal influenza challenge. Conclusions Temporal modulation of the lung microbiome profoundly influences mucosal vaccine-induced tissue-resident immunity. Our findings suggest that targeting the pulmonary microbiome could represent a novel approach to enhance respiratory vaccine efficacy. This abstract is funded by: National Research Foundation of Korea grant funded by Korea Government (Ministry of Science and ICT) Grants (RS-2023- 00213232)
Son et al. (Fri,) studied this question.