Lipid Nanoparticle Delivery Alters the Adjuvanticity of the TLR9 Agonist CpG by Innate Immune Activation in Lymphoid Tissue

Pharmacological strategies to activate innate immune cells are of great relevance in the context of vaccine design and anticancer immune therapy, to mount broad immune responses able to clear infection and malignant cells. Synthetic CpG oligodeoxynucleotides (CpG‐ODNs) are short single‐stranded DNA molecules containing unmethylated CpG dinucleotides and a phosphorothioate backbone. Class B CpG ODNs activate robust innate immune responses through a TLR9‐dependent NF‐κB signaling pathway. This feature is attractive to exploit in the context of vaccine design and cancer immunotherapy. Soluble CpG‐ODNs cause hepatic toxicity, which reduces its therapeutic applicability. The formulation of class B CpG ODN1826 in lipid nanoparticles (LNPs) containing an ionizable cationic lipid that complexes CpG through electrostatic interaction is reported. Upon local administration, LNP‐formulated CpG drains to lymph nodes and triggers robust innate immune activation. Unformulated, soluble, CpG, by contrast, is unable to induce robust innate activation in draining lymph nodes and is distributed systemically. In a vaccination setting, LNP‐formulated CpG, admixed with a protein antigen, induces higher antigen‐specific antibody titers and T cell responses than antigen admixed with unformulated soluble CpG. This study explores the encapsulation of Class B CpG ODN1826 in lipid nanoparticles to mitigate systemic toxicity and enhance immune response. The formulated CpG, localized to lymph nodes, triggers robust innate immune activation, outperforming unformulated counterparts in vaccine settings by inducing elevated antigen‐specific antibody titers and T cell responses, thus demonstrating significant potential in vaccine design and cancer immunotherapy.