mRNA-nanoparticles to enhance and track dendritic cell migration.

72 Background: Despite aggressive clinical interventions, glioblastoma (GBM) remains almost universally fatal. In a pilot, randomized, and blinded clinical trial, we recently demonstrated that administration of RNA-loaded dendritic cell (DC) vaccines was associated with significantly improved progression-free and overall survival in patients with GBM (Mitchell et al, Nature 2015). Furthermore, clinical outcomes correlated with migration of Indium-111-labeled DCs to vaccine-site draining lymph nodes (LNs) measured by SPECT/CT imaging. While these studies demonstrated that DC migration may be an important clinical biomarker for response to DC vaccination, the complexity and regulatory requirements associated with nuclear labeling to track DC migration limits widespread application of this technique. We have therefore developed RNA-loaded magnetic nanoparticles (RNA-NPs) to enhance DC migration to LNs and track that migration with a widely available imaging modality (i.e. MRI). Methods: Cationic liposomes were loaded with iron oxide nanoparticles with or without cholesterol modification. The resulting nanoparticles were complexed with RNA and used to transfect DCs ex vivo. RNA-NP-loaded DsRed+ DCs were then injected intradermally into mice and tracked noninvasively with T-weighted 11T MRI before excision and quantification with flow cytometry. Results: In vitro experiments demonstrate that iron oxide loading does not reduce RNA-NP-mediated transfection of DCs. Additionally, replacement of cationic lipids with cholesterol increased RNA-NP transfection of the DC2.4 cell line and enhanced the T cell stimulatory capacity of treated bone marrow-derived dendritic cells (BMDCs). Compared to electroporation, RNA-NPs enhanced DC migration to lymph nodes and reduced T MRI intensity in DC-bearing lymph nodes. Conclusions: This data suggests that iron oxide-loaded RNA-NPs enable noninvasive cell tracking with MRI and enhance DC migration to lymph nodes. We have further shown that inclusion of cholesterol in RNA-NPs augments the stimulatory capacity of transfected DCs. Future work will consider effects of RNA-NPs on antitumor immune responses and the utility of MRI-detected DC migration as a biomarker of vaccine efficacy.

Duke Scholars

Author Tyler Wildes