| Pluronic block copolymers, consisting of hydrophilic ethylene oxide (EO) and hydrophobic propylene oxide (PO) blocks, attracted considerable attention as promising polymer excipients for gene delivery applications. The current work examined use of Pluronics as (1) gene expression enhancing agents for DNA in ischemic muscle; and (2) dual function DNA vaccine adjuvants, capable of simultaneous boost of gene expression and immune response. The following results were obtained:;First, potential use of a Pluronic composition SP1017 in the formulation was shown for gene therapy of muscle ischemic conditions. Using the hindlimb ischemic mouse model we demonstrated that co-administration of SP1017 with a DNA greatly increases and prolongs expression of a transgene in muscle. Furthermore, this formulation, at the optimal dose, produced greater gene expression in ischemic muscle compared to non-ischemic muscle. The levels of plasmid DNA and its coded RNA in the ischemic muscle were increased with the SP1017/DNA formulation. Gene expression in muscle is localized in myocytes, endothelial cells and keratinocytes.;Second, we explored Pluronics as potential DNA vaccine adjuvants. It was shown that co-administration of a plasmid DNA with P85 in a skeletal muscle greatly increases expression not only in the local site but also in distant organs, especially, draining lymph nodes and spleen. Colocalization studies after co-administration of DNA and P85 have shown that the reporter gene (GFP) and therapeutic gene (MUC4) are expressed in myocytes and keratinocytes (muscle) as well as dendritic cells and macrophages (muscles, lymph nodes, spleen). Furthermore, in the case of MUC4 and P85 formulations the transgene was co-localized with T-cell markers in muscles, lymph nodes and spleen. The reporter gene formulated with P85 induced increased local and systemic expansion of DC, local expansion macrophages and natural killer cell populations, and maturation of local DC. Interestingly, the therapeutic gene delivered with a formulation containing P85 produced local and systemic expansion of cytotoxic and helper T-cell populations but had no effect on DC.;In conclusion, the results suggest that Pluronics are promising agents for gene therapy applications, which may be used as enhancers of gene expression and DNA vaccine adjuvants. |
