Dendritic cell targeting in lymph nodes with modular adapters boosts HAdV5 and HC-HAdV5 tumor vaccination by co-secretion of IL-2v and IL-21

Adenoviral vectors demonstrate encouraging clinical outcomes for B and T cell vaccines. With such approaches, multiple payloads can be delivered, beyond the antigen itself. Nevertheless, the human adenoviral vector serotype C5 (HAdV5) exhibits limited transduction efficiency to dendritic cells (DCs), therefore necessitating very high viral loads. Targeting antigen-presenting cells (APCs) has remained challenging. To solve this problem, we developed a versatile platform that employs modular retargeting adapters to enhance transduction of specific cell types, including challenging host cells. By rational design, we constructed a dual-adapter for DC-SIGN and CD11c and demonstrate successful targeting of HAdV5 to human and murine DCs. Our <i>in vivo</i> characterization highlights improved and specific transduction of DCs in draining lymph nodes. Moreover, a tumor vaccination study demonstrates the advantageous co-expression of T cell stimulatory cytokines (interleukin [IL]-2v or IL-21) locally in lymph nodes alongside a potent tumor antigen. Lymph node-directed gene therapy at significantly reduced vector loads may circumvent systemic toxicity of stimulating payloads. Our proposed low-dosage DC-targeted vaccine may offer an effective solution for patients and potentially minimize adenovirus-related side effects. The robust immunogenicity of HC-HAdV5, with its large coding capacity (37 kbp DNA), opens up exciting possibilities for future therapeutic combination strategies.