Carbohydrate functionalization modulates the mucosal transport and immunological activity of chitosan nanoparticles.

Mucosal vaccination represents an attractive strategy for preventing respiratory infections by establishing immune protection at the site of pathogen entry. However, the development of intranasal vaccines remains challenging due to limited epithelial transport, rapid mucociliary clearance, and the tolerogenic nature of the mucosal immune environment. Here, we report glycoengineered chitosan nanoparticles (NPs) functionalized with lactobionic acid, gluconic acid, and mannose as a platform to enhance mucosal vaccine delivery and immune activation. Carbohydrate functionalization preserved the mucoadhesive properties of chitosan while improving nanoparticle transport across the nasal epithelium, as demonstrated in human nasal epithelial models and confirmed ex vivo using rabbit nasal tissue. Mechanistic studies revealed receptor-mediated uptake of functionalized NPs by human macrophages, resulting in cellular internalization and polarization toward a pro-inflammatory M1 phenotype. Among the formulations evaluated, mannosylated NPs demonstrated a particularly pronounced immunostimulatory profile and promoted robust antigen-specific mucosal and systemic immune responses following intranasal administration, including elevated secretory IgA production, T-cell memory differentiation, and a balanced Th1/Th2/Th17 cytokine profile. Collectively, these findings demonstrate that glycoengineering of chitosan nanoparticles enhances both epithelial transport and immune activation through targeted nano-bio interactions. This work establishes carbohydrate-functionalized chitosan nanocarriers as a platform for effective intranasal vaccines against respiratory pathogens, including SARS-CoV-2.