(690d) Using Drug Loaded Liposomes to Induce Tolerogenic Antigen Presenting Cells

Autoimmune diseases are a growing problem in the western world and are particularly difficult to treat due to the wide range of disease pathogenesis and symptoms. As a result, treatments typically include broad immune suppression that leaves patients vulnerable for other infections. However, all autoimmune diseases originate with self-reactive antigens or self-reactive mimetics being uptaken and presented on antigen presenting cells (APC) and activating downstream adaptive immune cells leading to either a B or T cell or both. Under normal physiological conditions, this antigen presentation occurs in primary lymphoid organs and is accompanied with various inhibitory signals to generate a regulatory T cell (Treg) response that actively depletes any auto-reactive adaptive immune response to the self-antigen in question. This project focuses on delivering a combination of tolerance inducing drugs to APCs to drive a more tolerogenic phenotype to a particular antigen. Namely, three tolerogenic drugs, simvastatin, dexamethasone and SC-514, were loaded into a 200 nm liposome along with antigen protein and one of two toll-like-receptor agonists, GpG (for TLR9) or Flagellin (for TLR5). This strategy allowed for tolerogenic APCs to present either a model antigen (OVA) or MOG peptide (as a multiple sclerosis model antigen) and develop an antigen specific Treg response. We first screened a number of tolerance inducing drugs using bone marrow derived dendric cells (BMDCs) for IL-10/IL-6 and PD-L1/CD80 expression. After identifying three optimal candidates, we developed a liposomal formulation of the inhibitors, OVA and either CpG or FLA, to be injected on successive days to first “prime” APCs with the less activating FLA liposome, then the more active CpG liposome 24 hrs later. The liposome formulation was tested in vivo and triggered a two-fold increase in tolerogenic DCs (CD11c+, CD80-, PD-L1+) and a two-fold increase of OVA-specific Tregs (CD4+, CD25+, FoxP3+, OVA-Tetramer+). Furthermore, there was a complete reduction in any OVA specific antibodies or CD8 T cells when compared to non-inhibitor loaded controls. This is strong evidence that our liposome formulation can generate antigen specific T reg responses that can functionally reduce autoimmune responses. We are currently testing in an EAE model to further demonstrate the clinical relevance of this formulation as an autoimmune therapy.