Restoring the Immune Climate: Glycan-Functionalized Nanoparticles for Dendritic Cell Modulation in Cancer Therapy

Cancer immunotherapy has greatly advanced over the past decade, yet many patients still do not benefit due to insufficient priming of tumor-specific immune responses. Dendritic cells (DCs) are essential for initiating adaptive immunity, making them promising targets for vaccination. Nanoparticle-based vaccines, particularly liposomes, are well suited to combine antigens, adjuvants, and targeting moieties in a single formulation. In this thesis, we focused on targeting the C-type lectin receptor DC-SIGN, which is expressed on human DCs and certain macrophage subsets, and investigated its potential to enhance antigen delivery and T-cell activation through liposomal vaccine formulations. Chapter 1 introduces the role of DCs in anti-tumor immunity, highlighting their central position in activating adaptive immune responses. It discusses why efficient DC activation is essential for successful vaccination and provides the rationale for nanoparticle-based approaches that combine antigen, adjuvant, and targeting ligands within one formulation. Chapter 2 reviews C-type lectin receptors, and the potential as targets for DC targeting vaccination. These receptors, including DC-SIGN, Langerin, and MGL, recognize specific glycan structures and mediate antigen uptake. The chapter outlines how glycan-decorated nanoparticles can be use d to target these receptors to deliver antigens selectively to DC subsets, placing DC-SIGN targeting in the broader context of lectin-based vaccination strategies. In Chapter 3, we designed liposomal nanoparticles functionalized with the Lewis Y (LeY) glycan to target DC-SIGN, and co-formulated them with the glycolipid adjuvant α-Galactosylceramide (αGC). In vitro studies using human DCs and T cells showed that DC-SIGN–targeted liposomes were efficiently taken up and that the combination with αGC strongly enhanced invariant NKT (iNKT) cell activation and CD8⁺ T-cell activation. These results demonstrated that liposomal vaccines can be engineered to integrate DC targeting with adjuvant delivery, resulting in effective immune stimulation. In Chapter 4, we evaluated the targeted liposomal vaccines in vivo using a human DC-SIGN transgenic mouse model in which expression is driven by the CD11c promoter (DC-SIGNCD11c). Vaccination induced detectable antigen-specific immune responses, but CD8⁺ T-cell activation was not consistently stronger after DC-SIGN targeting compared to untargeted controls. Nevertheless, therapeutic tumor challenge experiments showed that targeted and untargeted formulations achieved similar tumor control, suggesting that enhanced uptake via DC-SIGN does not necessarily translate into superior T-cell immunity in this model. The DC-SIGNCD11c mouse model used in Chapter 4 expresses DC-SIGN primarily on DC, but not on macrophages, indicating that this model does not fully represent the identical expression pattern of DC-SIGN as found in humans. For this reason we introduced a second transgenic mouse line in Chapter 5 in which human DC-SIGN is expressed under its endogenous promoter (DC-SIGNEDNO). This model provided a more physiological distribution of DC-SIGN, predominantly on cDC2s, moDCs, and macrophages, and absent from cDC1s. Using this model, we demonstrated that subcutaneous administration of DC-SIGN–targeted antigens resulted in efficient uptake and presentation, leading to CD8⁺ T cell activation. In contrast, intravenous delivery was less effective. These findings highlight the importance of both receptor distribution and vaccination route in determining the outcome of targeted vaccination. Finally, in Chapter 6, we discussed the broader implications of these findings. We concluded that while DC-SIGN targeting can improve antigen delivery, its impact on immunogenicity depends on model context, antigen formulation, and adjuvant choice. The chapter also looks beyond scientific results. It reflects on the importance of prevention in healthcare, and on how lifestyle and environmental factors, including climate change, affect cancer risk. It also addresses the responsibility of the scientific community to adopt more sustainable research practices in order to reduce the environmental footprint of science.