METHODS: We investigated a novel form of allergen desensitization targeting dendritic cells (DCs) using allergenic epitopes encapsulated within biodegradable microspheres composed of poly-L-lactic-co-glycolic acid (PLGA) and containing the Th1 adjuvants monophosphoryl lipid A (MPLA) and CpG oligodeoxynucleotide. Bone marrow-derived dendritic cells (BMDC) were cultured from WT C57BL/6 mice with Fl3tL and GM-CSF for 15 days, then co-cultured with PLGA microspheres containing the OVA (SIINFEKL) epitope. We measured maturation and activation of the resulting cells by flow cytometry on day 21.
RESULTS: BMDC cultures showed maturation over the initial 15 day time course, with ~80% of DCs (defined as CD11c+ and MHC II+) expressing CD103 and ~20% expressing CD11b by day 15. Incubation for an additional seven days with microspheres encapsulating OVA peptide increased expression of MHC II, CD86, CCR4, and CCR7.
CONCLUSIONS: Microsphere-encapsulated epitope delivery is effective in activating BMDCs, in particular the pulmonary-resident but highly migratory population of CD103+ DCs. These cells travel to and from the lymph node and have long been implicated in the induction of strong, lasting immune responses. We hope to adapt this technology to an inhaled formulation in the future, targeted at each patients' specific allergen(s).
FUNDING: T32 HL007013 (SK)