Manipulation of local disposition and gene expression characteristics of plasmid DNA following intramuscular administration by complexation with cationic macromolecule

Biopolymer-based Carriers for DNA Vaccine Design

Over the last 30 years, genetically engineered DNA has been tested as novel vaccination strategy against various diseases, including human immunodeficiency virus (HIV), hepatitis B, several parasites, and cancers. However, the clinical breakthrough of the technique is confined by the low transfection efficacy and immunogenicity of the employed vaccines. Therefore, carrier materials were designed to prevent the rapid degradation and systemic clearance of DNA in the body. In this context, biopolymers are a particularly promising DNA vaccine carrier platform due to their beneficial biochemical and physical characteristics, including biocompatibility, stability, and low toxicity. This article reviews the applications, fabrication, and modification of biopolymers as carrier medium for genetic vaccines.

Tissue-specific Calibration of Real-time PCR Facilitates Absolute Quantification of Plasmid DNA in Biodistribution Studies

Analysis of the tissue distribution of plasmid DNA after administration of nonviral gene delivery systems is best accomplished using quantitative real-time polymerase chain reaction (qPCR), although published strategies do not allow determination of the absolute mass of plasmid delivered to different tissues. Generally, data is expressed as the mass of plasmid relative to the mass of genomic DNA (gDNA) in the sample. This strategy is adequate for comparisons of efficiency of delivery to a single site but it does not allow direct comparison of delivery to multiple tissues, as the mass of gDNA extracted per unit mass of each tissue is different. We show here that by constructing qPCR standard curves for each tissue it is possible to determine the dose of intact plasmid remaining in each tissue, which is a more useful parameter when comparing the fates of different formulations of DNA. We exemplify the use of this tissue-specific qPCR method by comparing the delivery of naked DNA, cationic DNA complexes, and neutral PEGylated DNA complexes after intramuscular injection. Generally, larger masses of intact plasmid were present 24 hours after injection of DNA complexes, and neutral complexes resulted in delivery of a larger mass of intact plasmid to the spleen.

Unique cytokine production profile following stimulation with DNA in macrophages from NZB/W F1 mice

Nucleosome is the major autoantigen in systemic lupus erythematosus (SLE). Professional antigen-presenting cells (APCs), such as macrophages (M Phis) and dendritic cells (DCs), play the central roles in the acquisition of Ag-specific immune responses and activation of such APCs is required for the efficient Ag-presentation. Therefore, adjuvant activity of DNA in nucleosomes would cause the prominent effects on the production of anti-nucleosome antibodies. In this study, we report that elicited peritoneal M Phis from New Zealand Black/White F1 (NZB/W) mice showed a unique cytokine production profile following stimulation with DNA. M Phis from 5-week old NZB/W mice produced a higher amount of IL-6 and about a half amount of TNF-alpha after stimulation with DNA complexed with cationic liposomes compared with those from control ICR mice. These results suggest that M Phis of NZB/W mice have altered responsiveness to DNA and this might elevate the antigenicity of nucleosomes to induce the production of anti-nucleosome antibodies.

[Development of heat shock proteins with controlled distribution properties and their application to vaccine delivery]

Antigen delivery to antigen-presenting cells (APCs) is a key issue in developing effective cancer vaccines. Controlling the tissue distribution of antigens, which are administered in a peptide/protein or DNA form, can increase antigen-specific immune responses, including the induction of cytotoxic T lymphocytes. Heat-shock protein 70 (Hsp70), a member of a highly conserved family of molecular chaperones, forms complexes with a variety of tumor-related antigens via its polypeptide binding domain. Because Hsp70 is taken up by APCs through the recognition by Hsp receptors, such as CD91 and LOX-1, its application to antigen delivery systems has been examined both in experimental and clinical settings. A tissue distribution study revealed that Hsp70 is mainly taken up by the liver, especially by hepatocytes, after intravenous injection in mice. A significant amount of Hsp70 was also delivered to regional lymph nodes when it was injected subcutaneously, supporting the hypothesis that Hsp70 is a natural targeting system to APCs. Model antigens were complexed with or conjugated to Hsp70, by which greater antigen-specific immune responses were achieved. Cytoplasmic delivery of Hsp70-antigen further increased the efficacy of the Hsp70-based vaccines. These findings indicate that effective cancer therapy can be achieved by developing Hsp70-based anticancer vaccines when their tissue and intracellular distribution is properly controlled.

Enhanced antigen-specific antibody production following polyplex-based DNA vaccination via the intradermal route in mice

DNA vaccination is an attractive approach with various advantages over conventional vaccination. The present study was undertaken to examine whether polyplex-based DNA vaccination could be used to modulate immune responses by plasmid DNA (pDNA). Methylated bovine serum albumin (mBSA) was used as a model of a cationic macromolecular carrier of pDNA encoding obalbumin (OVA) and the effects of polyplex formation of pDNA with mBSA on the antigen-specific immune responses were examined. Anti-OVA IgG antibody production was significantly increased following intradermal immunization with the polyplex compared with naked pDNA, although the induction of cytotoxic T lymphocyte activity was lowered by polyplex formation. We also demonstrated that the disposition and gene expression of pDNA following intradermal injection could be manipulated by polyplex formation. Intriguingly, we also found that the migration of dendritic cells to the injected site could be induced by polyplex formation probably due to a high level of tumor necrosis factor alpha production from the keratinocytes treated with mBSA/pDNA complexeses. Thus, the present study has demonstrated that the immune responses could be biased towards a Th2-type response by polyplex-based DNA vaccination through manipulation of not only pDNA disposition but also dendritic cell migration.