Dual antigen-sampling sites support early mucosal antigen uptake in the porcine nasal cavity

Intranasal vaccination is a promising strategy for preventing respiratory infections. However, the anatomical and cellular pathways responsible for antigen sampling in the porcine nasal cavity remain incompletely understood. Here, we identified and characterized two spatially distinct antigen-sampling sites in the porcine nasal cavity: the anterior respiratory mucosa (RM) and the posterior nasopharynx-associated lymphoid tissue (NALT). Following intranasal administration of ovalbumin (OVA), a subset of OVA⁺ epithelial cells at both sites was labeled by Ulex europaeus agglutinin I (UEA-1) and NKM 16-2-4, indicating that these cells might exhibit an M-cell-like phenotype. In RM, OVA was initially localized to the epithelium and was subsequently detected in the lamina propria by 6 h and in CD11c⁺ cells (a population that might include dendritic cells) at 24 h. By contrast, OVA reached the underlying lymphoid follicles in NALT as early as 2 h. OVA⁺ cells were also detected in mandibular draining lymph nodes at 6 h. Moreover, an air-liquid interface co-culture model showed apical-to-basolateral OVA transport across differentiated nasal epithelial cultures and subsequent OVA acquisition by underlying differentiated bone marrow cells (dBMCs). Together, these findings identify anterior RM and posterior NALT as two antigen-sampling sites with distinct temporal dynamics and define early cellular events that might contribute to mucosal immune induction in pigs.