Injectable, Pore-Forming Hydrogels for In Vivo Enrichment of Immature Dendritic Cells

Biomaterials-based vaccines have emerged as a powerful method to evoke potent immune responses directly in vivo, without the need for ex vivo cell manipulation, and modulating dendritic cell (DC) responses in a noninflammatory context could enable the development of tolerogenic vaccines to treat autoimmunity. This study describes the development of a noninflammatory, injectable hydrogel system to locally enrich DCs in vivo without inducing their maturation or activation, as a first step toward this goal. Alginate hydrogels that form pores in situ are characterized and used as a physical scaffold for cell infiltration. These gels are also adapted to control the release of granulocyte-macrophage colony stimulating factor (GM-CSF), a potent inducer of DC recruitment and proliferation. In vivo, sustained release of GM-CSF from the pore-forming gels leads to the accumulation of millions of cells in the material. These cells are highly enriched in CD11b(+) CD11c(+) DCs, and further analysis of cell surface marker expression indicates these DCs are immature. This study demonstrates that a polymeric delivery system can mediate the accumulation of a high number and percentage of immature DCs, and may provide the basis for further development of materials-based, therapeutic vaccines.