Nanogel-Stabilized Squalene Emulsion Enhances Humoral Immunity via Antigen Delivery to Migratory and Lymph Node-Resident Cells

Abstract Squalene-based emulsion adjuvants are widely used in vaccines; however, conventional surfactant-stabilized formulations provide limited control over antigen delivery to antigen-presenting cells (APCs). Here, we developed a nanogel-stabilized squalene emulsion (NgSE) using amphiphilic pullulan–cholesterol nanogels as Pickering emulsifiers to integrate antigen delivery and adjuvant functions within a single platform. NgSE exhibited tunable particle sizes ranging from 250 nm to 1 μm, enabling efficient antigen complexation onto the emulsion interface through simple mixing. In vitro, NgSE enhanced antigen uptake by dendritic cells and macrophages compared to soluble antigens. In vivo, 250 nm NgSE promoted efficient antigen delivery to both migratory and lymph node-resident APCs, accompanied by increased immune cell recruitment and APC activation in the draining lymph nodes. These immunological effects translate into substantially enhanced antigen-specific antibody responses compared with soluble antigens. Collectively, these results demonstrate that nanogel-stabilized squalene emulsions can facilitate antigen delivery to multiple APC subsets while preserving the immunostimulatory properties of squalene emulsion adjuvants, highlighting their potential as APC-interactive vaccine delivery carriers.