Robust expansion of dendritic cells in vivo by hydrodynamic FLT3L-FC gene transfer

• We engineered a novel FLT3L-immunoglobulin FC fusion construct.
• The FC-domain improved the plasma pharmacokinetics profile of FLT3L.
• Hydrodynamic gene transfer using FLT3L-FC DNA induced robust DC expansion in vivo.
• FLT3L-FC protein produced in vivo spontaneously dimerized to enable FLT3 signaling.
• Splenomegaly is an effective pharmacodynamic readout for FLT3L action in vivo.

Due to low numbers of endogenous dendritic cells (DCs) in vivo, exogenous DC-poietin Fms-like tyrosine kinase 3-ligand (FLT3L) is routinely used to generate DC for subsequent studies. We engineered a novel FLT3L-FC DNA construct that, when combined with hydrodynamic gene transfer (HDT), induced robust DC expansion in mice. DC generated in vivo by FLT3L-FC HDT produced cytokines in response to stimulation by an array of TLR agonists and promoted T cell proliferation. The FLT3L-FC protein produced in vivo spontaneously homodimerized to enable effective FLT signaling and the FC-domain enhanced its plasma half-life, providing an improved reagent and method to boost DC numbers.