A Novel Hybrid Biological-Biomaterial Vector for Antigen Delivery and Human Dendritic Cell Maturation 2306812

Introduction The use of antigen (Ag) presenting dendritic cells (DC) strategy can prompt effective and personalized anti-tumor immune responses with little immune-mediated toxicity. However, current formulations have resulted in clinical objective responses amongst only a small subset of patients. Current strategies rely on cytokine-based maturation cocktails that result in heterogenous maturation of DCs as measured by costimulatory molecule expression. We propose a novel hybrid vector (HV) that utilizes a bacterial core encased in a polymeric shell to deliver plasmid DNA (pDNA)-encoded Ag, resulting in simultaneous delivery of maturation stimuli and target Ag to be durably expressed within DC. We hypothesize that this method will improve DC maturation and resultant Ag-specific T cell expansion, thereby improving antitumor responses. Methods To evaluate the effect of the HV, human monocytes isolated from whole blood were differentiated for 7 days with GM-CSF and IL-4 into monocyte-derived DC and subsequently co-cultured with HV constructs or a maturation cytokine cocktail of IL-1β, TNFα, IL-6, and PGE2. Following stimulation, DC were directly analyzed via flow cytometry or co-cultured with T cells before analysis. Results HV-conditioned DC showed a 1.9-fold increase in CD80 expression and a 2.7-fold increase in CD83 expression after 48 hours compared to standard DC differentiation protocols. Using plasmid-encoded fluorescent reporters, expression of pDNA-encoded protein was detected via imaging flow cytometry and fluorescent microscopy only in HV-conditioned DC, suggesting successful pDNA translocation and expression within DC. DC conditioned with the HV encoding MART-1 Ag promoted a 4-fold increase in the expansion of MART-1-specific T cells when co-cultured compared to a plasmid control. Conclusion The HV provides a novel and highly modifiable platform for both enhancing DC maturation and Ag presentation while also offering mechanistic insight into both DC biology and resultant immune responses. Funding Source NIH R01 CA270155 Topic Categories Vaccines and Immunotherapy (VAC)