DNA-based vaccination against hepatitis B virus

Micro- and nanoparticle-based vaccines for hepatitis B

The incredible success of vaccinations in contributing to public health is undeniable. In fact, vaccines are the most cost-effective public health tool for disease prevention because their cost is less than the combined costs of treatment, hospitalization, and time loss from work. However, despite the availability of vaccines, cost per dose is a factor limiting the success of global vaccination campaigns, as are the limitations imposed by the need of delivering multiple vaccine doses. A number of approaches are being tested particularly for the delivery of subunit vaccines, and in recent years, a number of groups have devoted their efforts to develop nano/microparticles prepared from biodegradable and biocompatible polymers as vaccine delivery systems with the goal of inducing both humoral and cellular immune responses. Some important properties of biodegradable polymers are their documented safety history, biocompatibility, and an ability to provide controlled time/rate of antigen release and polymer degradation. The most extensively studied polymer used for encapsulating vaccine antigens is poly (lactide-co-glycolide acid) (PLGA). This chapter deals in brief with efforts targeting the use of PLGA micro-and nanoparticles for the delivery of hepatitis B surface antigen.

Mannosylated niosomes as adjuvant–carrier system for oral genetic immunization against Hepatitis B

Aim of the present study was to develop mannosylated niosomes as oral DNA vaccine carriers for the induction of humoral, cellular and mucosal immunity. Niosomes composed of span 60, cholesterol and stearylamine as constitutive lipids were prepared by reverse phase evaporation method and were coated with a modified polysaccharide o-palmitoyl mannan (OPM) in order to protect them from bile salt caused dissolution and enzymatic degradation in the gastrointestinal tract and to enhance their affinity towards the antigen presenting cells of Peyer's patches. Prepared niosomes were characterized in vitro for their size, shape, entrapment efficiency, ligand binding specificity and stability in simulated gastric fluid and simulated intestinal fluid. OPM coated niosomes were found to better stable in simulated GIT conditions. The immune stimulating activity was studied by measuring serum anti-HBsAg titer, secretory IgA level in intestinal and salivary secretions and cyokines level (IL-2 and IFN-gamma) in spleen homogenates following oral administration of niosomal formulations in Balb/c mice and compared with naked DNA as well as pure recombinant HBsAg injected intramuscularly. The serum anti-HBsAg titer obtained after oral administration of OPM coated niosomal formulations was although less as compared to that elicited by naked DNA and pure HBsAg administered intramuscularly, but the mice were seroprotective within 2 weeks and antibody level far above the clinically protective limit for humans was achieved. Intramuscular naked DNA and recombinant HBsAg did not elicited sIgA titer in mucosal secretions that was induced by oral administration of OPM coated niosomes. Similarly, cellular response (cytokines level) was absent in pure HBsAg treated animals. OPM coated niosomes produced humoral (both systemic and mucosal) and cellular immune response upon oral administration. The study signifies the potential of OPM coated niosomes as DNA vaccine carrier and adjuvant for effective oral immunization.

Liposome/DNA complexes coated with biodegradable PLA improve immune responses to plasmid encoding hepatitis B surface antigen

We hypothesized that the addition of polymer to the surface of liposome/DNA complexes may potentially enhance in vivo delivery of plasmid DNA to antigen-presenting cells and thereby facilitate enhanced immune responses to encoded protein. BALB/c mice were immunized subcutaneously or intramuscularly three times with a total of 50 microg of the plasmid pRc/CMV-HBs(S) (ayw subtype) encoding for the hepatitis B surface antigen. We measured transgene-specific total immunoglobulin G (IgG), IgG2a, IgG2b and IgG1 antibody responses as well as splenocyte and T-cell proliferation and cytokine production upon re-stimulation following immunization. Modification of lipid/DNA complexes by the polymer precipitation method used here for the addition of poly(d,l-lactic acid) was found to be consistently and significantly more effective than either unmodified liposomal DNA or naked DNA in eliciting transgene-specific immune responses to plasmid-encoded antigen when administered by the subcutaneous route. In addition, the polymer-modified formulations delivered by this route were more effective than naked DNA delivered by the intramuscular route in inducing antibody responses (n=5, P<0.03). Our observations provide 'proof of principle' for the use of these multicomponent formulations, which offer potential for manipulation and increased transfection efficiency in vivo for the purposes of genetic immunization.

Manufacturing and quality control of plasmid-based gene expression systems

DNA plasmid-based gene expression systems are being widely investigated for the potential treatment of genetic and acquired disease and for DNA-based vaccination. A number of human clinical trials are in progress using plasmid-based drugs. The regulatory framework that has been applied to biologicals such as recombinant DNA-derived proteins has proven to be generally applicable for regulating plasmid-based drugs as well. This was recently emphasized by the inclusion of therapeutic DNA plasmid products in the U.S. Food and Drug Administration's list of well-characterized biotechnology products. Present techniques for manufacturing and characterizing plasmids have been adapted from large-scale protein purification and from traditional molecular biology. Production of multi-gram quantities of plasmid, at purities of 95% or more, is currently possible, but further development of both manufacturing and analytical techniques is required. This review describes the approaches and methods currently used to manufacture and characterize DNA plasmids for pharmaceutical use, as well as recent changes in the regulatory environment that will impact future development and marketing of plasmids as human drugs.