Targeting DEC-205-DCIR2+ dendritic cells promotes immunological tolerance in proteolipid protein-induced experimental autoimmune encephalomyelitis.

BACKGROUND: Dendritic cells (DC) induce adaptive responses against foreign antigens, and play an essential role in maintaining peripheral tolerance to self-antigens. Therefore they are involved in preventing fatal autoimmunity. Selective delivery of antigens to immature DC via the endocytic DEC-205 receptor on their surface promotes antigen-specific T cell tolerance, both by recessive and dominant mechanisms. We provide evidence that the induction of antigen-specific T cell tolerance is not a unique property of CD11c+CD8+DEC-205+ DCs. METHODS: We employed a fusion between αDCIR2 antibodies and the highly encephalitogenic peptide 139-151 of myelin-derived proteolipid protein (PLP139-151), to target CD11c +CD8- DCs with a DEC-205-DCIR2+ phenotype in vivo, and to substantially improve clinical symptoms in the PLP139-151-induced model of experimental autoimmune encephalomyelitis (EAE). RESULTS: Consistent with previous studies targeting other cell surface receptors, EAE protection mediated by αDCIR2-PLP139-151 fusion antibody (Ab) depended on an immature state of targeted DCIR2+ DCs. The mechanism of αDCIR2-PLP139-151 mAb function included the deletion of IL-17- and IFN-γ-producing pathogenic T cells, as well as the enhancement of regulatory T (Treg) cell activity. In contrast to the effect of αDEC-205+ fusion antibodies, which involves extrathymic induction of a Foxp3+ Treg cell phenotype in naïve CD4+Foxp3- T cells, treatment of animals with DCIR2+ fusion antibodies resulted in antigen-specific activation and proliferative expansion of natural Foxp3+ Treg cells. CONCLUSIONS: These results suggest that multiple mechanisms can lead to the expansion of the Treg population, depending on the DC subset and receptor targeted.

Advancing drug delivery systems for the treatment of multiple sclerosis.

Multiple sclerosis (MS) is a chronic inflammatory autoimmune disease of the central nervous system. It is characterized by demyelination of neurons and loss of neuronal axons and oligodendrocytes. In MS, auto-reactive T cells and B cells cross the blood-brain barrier (BBB), causing perivenous demyelinating lesions that form multiple discrete inflammatory demyelinated plaques located primarily in the white matter. In chronic MS, cortical demyelination and progressive axonal transections develop. Treatment for MS can be stratified into disease-modifying therapies (DMTs) and symptomatic therapy. DMTs aim to decrease circulating immune cells or to prevent these cells from crossing the BBB and reduce the inflammatory response. There are currently 10 DMTs approved for the relapsing forms of MS; these vary with regard to their efficacy, route and frequency of administration, adverse effects, and toxicity profile. Better drug delivery systems are being developed in order to decrease adverse effects, increase drug efficacy, and increase patient compliance through the direct targeting of pathologic cells. Here, we address the uses and benefits of advanced drug delivery systems, including nanoparticles, microparticles, fusion antibodies, and liposomal formulations. By altering the properties of therapeutic particles and enhancing targeting, breakthrough drug delivery technologies potentially applicable to multiple disease treatments may rapidly emerge.

Effect of pore structure of macroporous poly(lactide-co-glycolide) scaffolds on the in vivo enrichment of dendritic cells.

The in vivo enrichment of dendritic cells (DCs) in implanted macroporous scaffolds is an emerging strategy to modulate the adaptive immune system. The pore architecture is potentially one of the key factors in controlling enrichment of DCs. However, there have been few studies examining the effects of scaffold pore structure on in vivo DC enrichment. Here we present the effects of surface porosity, pore size, and pore volume of macroporous poly(lactide-co-glycolide) (PLG) scaffolds encapsulating granulocyte macrophage colony-stimulating factor (GM-CSF), an inflammatory chemoattractant, on the in vivo enrichment of DCs. Although in vitro cell seeding studies using PLG scaffolds without GM-CSF showed higher cell infiltration in scaffolds with higher surface porosity, in vivo results revealed higher DC enrichment in GM-CSF loaded PLG scaffolds with lower surface porosity despite a similar level of GM-CSF released. The diminished compressive modulus of high surface porosity scaffolds compared to low surface porosity scaffolds lead to the significant shrinkage of these scaffolds in vivo, suggesting that the mechanical strength of scaffolds was critical to maintain a porous structure in vivo for accumulating DCs. The pore volume was also found to be important in total number of recruited cells and DCs in vivo. Varying the pore size significantly impacted the total number of cells, but similar numbers of DCs were found as long as the pore size was above 10-32 µm. Collectively, these results suggested that one can modulate in vivo enrichment of DCs by altering the pore architecture and mechanical properties of PLG scaffolds.