The chitosan nanoparticle-based adjuvant CH-100 orchestrates multifaceted innate immune activation via STING-dependent and -independent pathways

Adjuvants enhance vaccine efficacy by activating innate immunity; yet, the mechanisms of nanoparticle-based adjuvants remain incompletely defined. Here, we characterize CH-100, a chitosan nanoparticle adjuvant, and its capacity to coordinate dendritic cell (DC) activation and promote adaptive immune responses. CH-100 enhances antigen uptake, upregulates co-stimulatory molecules, and elicits antigen-specific antibody and cytotoxic T lymphocytes (CTL) responses. Mechanistically, CH-100 induces mitochondrial reactive oxygen species (ROS), leading to NLRP3 inflammasome activation, although NLRP3 is not essential for the observed adaptive responses. In parallel, CH-100 triggers the STING-IRF3 pathway to induce type I interferons; STING-deficiency partially diminishes antibody and CTL responses, suggesting involvement of additional signaling. Transcriptomic analysis reveals STING-independent upregulation of genes related to Th17 differentiation, accompanied by activation of TBK1, NF-κB, and p38 pathways in DCs, ultimately promoting Th17-skewed immunity. These findings demonstrate how CH-100 engages both STING-dependent and -independent innate pathways to shape adaptive immunity, offering mechanistic insights into chitosan-based adjuvants for future vaccine development.