In vitro, ex vivo and in vivo evaluation of polyelectrolyte nanogels for mucosal vaccines.

Nasal administration is investigated as an effective mucosal site suitable for non-invasive vaccine delivery and able to elicit both systemic and mucosal immunity. Delivery of proteins across the epithelial barrier is a key point to induce an immune response. In this framework, nanogels are properly designed to present the delivered antigen to the immune system, promoting their targeting to specific immune populations. Nanogels for nasal administration based on dextran sulfate and ϵ-poly-L-lysine have been prepared by polyelectrolyte complexation. To unlock the potential of mucosal vaccination, we evaluated nanogel for their ability to enhance antigen delivery across mucus barriers and promote immune activation. Using fluorescein-labelled ovalbumin as a model antigen, we investigated how nanogel governs antigen transport, cellular uptake, and presentation. Produced results showed that nanogel combines favourable physicochemical properties with mucoadhesive behaviour, enabling efficient interaction with the mucus layer. This translates into enhanced uptake and controlled intracellular trafficking in murine Bone Marrow-derived-Dendritic Cells, ultimately promoting effective antigen cross-presentation. Importantly, intranasal administration in vivo revealed prolonged antigen retention within the airway mucosa compared to the free antigen, indicating sustained local antigen availability. In addition, studies in human monocyte-derived macrophages provided preliminary information on the inflammatory response and intracellular fate of the nanogels in a human-relevant system. Together, these findings contribute to the preliminary preclinical characterization of the nanogel platform, while further studies are required to establish its immunogenicity and vaccine efficacy.