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Our previous study demonstrated that a selected β-lactoglobulin-derived peptide (BLG-Pep) loaded in poly(lactic-co-glycolic acid) (PLGA) nanoparticles protected mice against cow's milk allergy development. However, the mechanism(s) responsible for the interaction of the peptide-loaded PLGA nanoparticles with dendritic cells (DCs) and their intracellular fate was/were elusive. Förster resonance energy transfer (FRET), a distance-dependent non-radioactive energy transfer process mediated from a donor to an acceptor fluorochrome, was used to investigate these processes. The ratio of the donor (Cyanine-3)-conjugated peptide and acceptor (Cyanine-5) labeled PLGA nanocarrier was fine-tuned for optimal (87%) FRET efficiency. The colloidal stability and FRET emission of prepared NPs were maintained upon 144 h incubation in PBS buffer and 6 h incubation in biorelevant simulated gastric fluid at 37 °C. A total of 73% of Pep-Cy3 NP was internalized by DCs as quantified using flow cytometry and confirmed using confocal fluorescence microscopy. By real-time monitoring of the change in the FRET signal of the internalized peptide-loaded nanoparticles, we observed prolonged retention (for 96 h) of the nanoparticles-encapsulated peptide as compared to 24 h retention of the free peptide in the DCs. The prolonged retention and intracellular antigen release of the BLG-Pep loaded in PLGA nanoparticles in murine DCs might facilitate antigen-specific tolerance induction. [ABSTRACT FROM AUTHOR]

The current treatment of autoimmune and chronic inflammatory diseases entails systemic immune suppression, which is associated with increased susceptibility to infections. To restore immune tolerance and reduce systemic side effects, a targeted approach using tolerogenic dendritic cells (tolDCs) is being explored. tolDCs are characterized by the expression of CD11c, the major histocompatibility complex (MHC)II and low levels of co-stimulatory molecules CD40 and CD86. In this study, tolDCs were generated using a human-proteoglycan-derived peptide (hPG) and all-trans retinoic acid (RA). RA-tolDCs not only display a tolerogenic phenotype but also can induce an antigen-specific regulatory T cell (Treg) response in vitro. However, further analysis showed that RA-tolDCs make up a heterogeneous population of DCs, with only a small proportion being antigen-associated tolDCs. To increase the homogeneity of this population, 1,2-distearoyl-sn-glycero-3-phosphoglycerol (DSPG)-containing liposomes were used to encapsulate the relevant antigen together with RA. These liposomes greatly enhanced the proportion of antigen-associated tolDCs in culture. In addition, in mice, we showed that the liposomal co-delivery of antigen and RA can be a more targeted approach to induce antigen-specific tolerance compared to the injection of RA-tolDCs, and that these liposomes can stimulate the generation of antigen-specific Tregs. This work highlights the importance of the co-delivery of an antigen and immunomodulator to minimize off-target effects and systemic side effects and provides new insights in the use of RA for antigen-specific immunotherapy for autoimmune and chronic inflammatory diseases. [ABSTRACT FROM AUTHOR]

Despite promising progress in cancer vaccination, therapeutic effectiveness is often insufficient. Cancer vaccine effectiveness could be enhanced by targeting vaccine antigens to antigen-presenting cells, thereby increasing T-cell activation. CD169-expressing splenic macrophages efficiently capture particulate antigens from the blood and transfer these antigens to dendritic cells for the activation of CD8+ T cells. In this study, we incorporated a physiological ligand for CD169, the ganglioside GM3, into liposomes to enhance liposome uptake by CD169+ macrophages. We assessed how variation in the amount of GM3, surface-attached PEG and liposomal size affected the binding to, and uptake by, CD169+ macrophages in vitro and in vivo. As a proof of concept, we prepared GM3-targeted liposomes containing a long synthetic ovalbumin peptide and tested the capacity of these liposomes to induce CD8+ and CD4+ T-cell responses compared to control liposomes or soluble peptide. The data indicate that the delivery of liposomes to splenic CD169+ macrophages can be optimized by the selection of liposomal constituents and liposomal size. Moreover, optimized GM3-mediated liposomal targeting to CD169+ macrophages induces potent immune responses and therefore presents as an interesting delivery strategy for cancer vaccination. [ABSTRACT FROM AUTHOR]