Prophylactic anti-tumor effects in a B cell lymphoma model with DNA vaccines delivered on polyethylenimine (PEI)...

Idiotypic sequences, specific to the hypervariable regions of immunoglobulins expressed by malignant B cells offer a therapeutic target in B cell lymphoma. Efficient approaches have been described to clone a single chain fragment of the tumor immunoglobulin (Ig) comprising of heavy and light Ig chains (sFv) fused with proinflammatory chemokines. Tumor associated, poorly immunogenic self antigens encoded by plasmid DNA (pDNA) have been rendered immunogenic by chemokine fusion, thereby targeting to antigen presenting cells (APCs) which differentially express chemokine receptors. Here we present an injectable (parenteral) approach using synthetic polymer based cationic microparticle formulations for enhancing the potency of such chemokine/self antigen expressing plasmid construct. Branched and linear polyethyleneimine (PEI) were conjugated on poly (D, L lactide-co-glycolide) (PLGA) microparticles using carbodiimide chemistry followed by efficient loading of plasmid DNA. In addition to imparting significant buffering ability to these cationic microparticles, flow cytometry studies indicate that these DNA loaded microparticles significantly up regulate CD80 and MHC class II markers in phagocytic RAW264.7 cells, indicating intrinsic adjuvant effects. Intradermal injections in Balb/c mice with these formulations induced significant protection upon tumor challenge with 2.5 times the minimal lethal dose. Long term survival rates were significant (p < 0.05) in comparison with saline injected controls or blank microparticles. Further studies indicated that intramuscular delivery might provide better protection compared to intradermal injections and perform similar to gene gun mediated administration. We conclude, based on these promising in vivo results, that such surface-functionalized microparticles offer an attractive strategy to improve the potency of self antigen-based cancer DNA vaccines.