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

Chitosans for delivery of nucleic acids

Alternatives to efficient viral vectors in gene therapy are desired because of their poor safety profiles. Chitosan is a promising non-viral nucleotide delivery vector because of its biocompatibility, biodegradability, low immunogenicity and ease of manufacturing. Since the transfection efficiency of chitosan polyplexes is relatively low compared to viral counterparts, there is an impetus to gain a better understanding of the structure-performance relationship. Recent progress in preparation and characterisation has enabled coupling analysis of chitosans structural parameters that has led to increased TE by tailoring of chitosan's structure. In this review, we summarize the recent advances that have lead to a more rational design of chitosan polyplexes. We present an integrated review of all major areas of chitosan-based transfection, including preparation, chitosan and polyplexes physicochemical characterisation, in vitro and in vivo assessment. In each, we present the obstacles to efficient transfection and the strategies adopted over time to surmount these impediments.

Nanotechnological Approaches for Genetic Immunization

Genetic immunization is one of the important findings that provide multifaceted immunological response against infectious diseases. With the advent of r-DNA technology, it is possible to construct vector with immunologically active genes against specific pathogens. Nevertheless, site-specific delivery of constructed genetic material is an important contributory factor for eliciting specific cellular and humoral immune response. Nanotechnology has demonstrated immense potential for the site-specific delivery of biomolecules. Several polymeric and lipidic nanocarriers have been utilized for the delivery of genetic materials. These systems seem to have better compatibility, low toxicity, economical and capable to delivering biomolecules to intracellular site for the better expression of desired antigens. Further, surface engineering of nanocarriers and targeting approaches have an ability to offer better presentation of antigenic material to immunological cells. This chapter gives an overview of existing and emerging nanotechnological approaches for the delivery of genetic materials.

Alginate-chitosan-PLGA composite microspheres enabling single-shot hepatitis B vaccination

Hepatitis B vaccination typically requires a multi-dose administration protocol over a course of 3-6 months. Aiming at developing a single-shot formulation for hepatitis B vaccine (hepatitis B surface antigen (HBsAg)), a novel vaccine delivery system, the composite microspheres of alginate-chitosan-poly(lactic-co-glycolic acid) (PLGA), was synthesized by a two-step preparation. The composite microspheres showed distinct advantages over the conventional PLGA microspheres in aspects of the high loading capacity and the elimination of lyophilizing process. The loading capacity of the composite microspheres was about seven times higher than those in the conventional PLGA microspheres, due to the protein-friendly microenvironment created by the hydrophilic alginate-chitosan cores of the composite microspheres. This vaccine delivery system was shown to be able to induce robust immune responses by single injection and display no significant difference in HBsAg-specific antibody levels compared to the double-injection method.

Oral Plasmid DNA Delivery Systems for Genetic Immunisation

The use and optimisation of plasmid DNA delivery systems for the purposes of eliciting transgene specific immune responses to orally administered DNA encoded antigen represents a significant challenge. Here, we have outlined a multicomponent polymer modified liposomal delivery system that offers potential for oral administration of plasmid DNA. It is shown that the polymer/liposome formulated DNA is able to elicit markedly enhanced transgene specific cytokine production following in vitro restimulation of splenocytes with recombinant antigen. This is discussed with reference to recent publications and the potential of plasmid DNA delivery systems for the purposes of genetic immunisation, as reported in selected literature, is assessed.

Surface modified liposomes for nasal delivery of DNA vaccine

The aim of the present work was to investigate the potential utility of glycol chitosan coated liposomes as nasal vaccine delivery vehicle for eliciting viral specific humoral mucosal and cellular immune responses. Plasmid pRc/CMV-HBs(S) encapsulated liposomes were prepared by dehydration-rehydration method and subsequently coated with glycol chitosan by simple incubation method. Liposomes were then characterized for their size, surface charge, entrapment efficiency, and ability to protect encapsulated DNA against nuclease digestion and for their mucoadhesiveness. The liposomes were then administered to mice in order to study their feasibility as nasal vaccine carriers. The developed liposomes possessed +9.8 mV zeta potential and an average vesicle size less than 1 microm and entrapment efficiency of approximately 53%. Following intranasal administration, glycol chitosan coated liposomes elicited humoral mucosal and cellular immune responses that were significant as compared to naked DNA justifying the potential advantage of mucosal vaccination in the production of local antibodies at the sites where pathogens enters the body.

Comparison of vesicle based antigen delivery systems for delivery of hepatitis B surface antigen

There is a clinical need for a more effective vaccine against hepatitis B, and in particular vaccines that may be suitable for therapeutic administration. This study assesses the potential of cationic surfactant vesicle based formulations using two agents; the cationic amine containing [N-(N',N'-dimethylaminoethane)-carbamoyl] cholesterol (DC-Chol) or dimethyl dioctadecylammonium bromide (DDA) with hepatitis B surface antigen (HBsAg). Synthetic mycobacterial cord factor, trehalose 6,6'-dibehenate (TDB) has been used as an adjuvant and the addition of 1-monopalmitoyl glycerol (C16:0) (MP) and cholesterol (Chol) to DDA-TDB is assessed for its potential to facilitate formation of dehydration-rehydration vesicles (DRV) at room temperature, and the effect of this on immune responses. A DRV formulation is directly compared to an adsorbed formulation of the same composition and preparation protocol (MP:dioleoyl phosphoethanolamine (DOPE):Chol:DC-Chol) and the direct substitution of MP with phosphatidylcholine (PC) is also compared in DRV antigen-entrapped formulations. MP and Chol were shown to facilitate the use of DDA-TDB in DRV formulations prepared at room temperature, whilst there was marginal alteration of immunogenicity (a reduction in HBsAg-specific IL-2). The HBsAg adsorbed DRV formulation was not significantly different from the HBsAg entrapped DRV formulation. Overall, DDA formulations incorporating TDB showed markedly increased antigen specific splenocyte proliferation and elicited cytokine production concomitant with a strong T cell driven response, delineating formulations that may be useful for further evaluation of their clinical potential.

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.

Diphtheria toxoid loaded poly-(epsilon-caprolactone) nanoparticles as mucosal vaccine delivery systems

Poly-(epsilon-caprolactone) (PCL), a poly(lactide-co-glycolide) (PLGA)-PCL blend and co-polymer nanoparticles encapsulating diphtheria toxoid (DT) were investigated for their potential as a mucosal vaccine delivery system. The nanoparticles, prepared using a water-in-oil-in-water (w/o/w) double emulsion solvent evaporation method, demonstrated release profiles which were dependent on the properties of the polymers. An in vitro experiment using Caco-2 cells showed significantly higher uptake of PCL nanoparticles in comparison to polymeric PLGA, the PLGA-PCL blend and co-polymer nanoparticles. The highest uptake mediated by the most hydrophobic nanoparticles using Caco-2 cells was mirrored in the in vivo studies following nasal administration. PCL nanoparticles induced DT serum specific IgG antibody responses significantly higher than PLGA. A significant positive correlation between hydrophobicity of the nanoparticles and the immune response was observed following intramuscular administration. The positive correlation between hydrophobicity of the nanoparticles and serum DT specific IgG antibody response was also observed after intranasal administration of the nanoparticles. The cytokine assays showed that the serum IgG antibody response induced is different according to the route of administration, indicated by the differential levels of IL-6 and IFN-gamma. The nanoparticles eliciting the highest IgG antibody response did not necessarily elicit the highest levels of the cytokines IL-6 and IFN-gamma.

Strategies for DNA vaccine delivery

Strategies for gene delivery comprise a diverse range of live and synthetic approaches; DNA delivery for the purposes of immunisation in turn comprises a large part of this research. This review mainly discusses synthetic systems for application in the delivery of plasmid DNA vaccines, outlining polylactide-co-glycolide, liposome, chitosan and complex combination delivery systems. Areas of promise for DNA vaccine candidates include immune modulation of allergic responses and veterinarian application. The potential for realistic consideration of DNA vaccines as an alternative to existing approaches is dependent on the development of efficient DNA vaccine vectors and improved systems for DNA vaccine delivery. DNA vaccine technology may yet prove to be an important asset in an environment where there is a critical need for therapeutic and prophylactic strategies to combat a wide range of disease states.

DNA vaccines for biodefence

The advantages associated with DNA vaccines include the speed with which they may be constructed and produced at large-scale, the ability to produce a broad spectrum of immune responses, and the ability for delivery using non-invasive means. In addition, DNA vaccines may be manipulated to express multiple antigens and may be tailored for the induction of appropriate immune responses. These advantages make DNA vaccination a promising approach for the development of vaccines for biodefence. In this review, the potential of DNA vaccines for biodefence is discussed.

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

To modulate the immune responses of DNA vaccine, it is very important to control the disposition and gene expression of plasmid DNA (pDNA) after local administration. We chose methylated bovine serum albumin (mBSA), a cationic macromolecule, as a carrier of pDNA. We examined the effects of complexation of pDNA with mBSA on the disposition and gene expression in mice after intramuscular administration. The elimination from injection site was retarded and the accumulation to lymph nodes was increased at the positively charged mBSA/pDNA complexes. As the charge ratios of mBSA/pDNA complexes were higher, the levels of gene expression were reduced. Antigen specific immune responses were evaluated using pDNA encoding ovalbumin (OVA), pCMV-OVA, as a model antigen-expressing pDNA. However, significant levels of production of anti-ovalbumin IgG antibody were obtained in mice immunized with a positively charged complex, mBSA/pCMV-OVA (8:1) (weight ratio). In vitro experiments using DC2.4 cells, a murine dendritic cell line, demonstrated that the levels of gene expression and cytokine release were increased by complexation. These results suggest that the immune responses might be manipulated by complexation presumably due to the altered disposition and gene expression of pDNA.

VP22 enhances antibody responses from DNA vaccines but not by intercellular spread

In some species DNA vaccines elicit potent humoral and cellular immune responses. However, their performance in humans and non-human primates is less impressive. There are suggestions in the literature that an increase in the intercellular distribution of protein expressed from a DNA vaccine may enhance immunogenicity. We incorporated the Herpes Simplex Virus type 1 (HSV) VP22 gene, which encodes a protein that has been described as promoting intercellular spread, into a DNA vector in which it was fused to enhanced green fluorescent protein (EGFP). Following transfection of the plasmid DNA into mammalian cells, distribution of the fusion protein VP22-EGFP was not increased compared to EGFP alone. Furthermore, we found no evidence to suggest that VP22 was capable of mediating intercellular spread. However, when these constructs were used as DNA vaccines to immunise mice, antibody levels specific to EGFP were significantly enhanced when EGFP was fused to VP22. These data suggest that amplification of the immune response may occur via mechanisms other than VP22-mediated intercellular spread of antigen.

Anti-HBV effect of liposome-encapsulated matrine in vitro and in vivo

AIM

To study the anti-HBV effect of liposome-encapsulated matrine (Lip-M) in vitro and in vivo.

METHODS

2.2.15 cell line was cultured in vitro to observe the effect of Lip-M and matrine on the secretion of HBsAg and HBeAg. The toxicity of Lip-M and matrine to 2.2.15 cell line was also studied by MTT method. In in vivo study, drug treatment experiment was carried out on the 13th day after ducks were infected with duck hepatitis B virus (DHBV). The ducks were randomly divided into 4 groups with 5-6 ducks in each group. Lip-M and matrine were given to DHBV-infected ducks respectively by gastric perfusion. Four groups were observed: group of Lip-M (20 mg/kg), group of Lip-M (10 mg/kg), group of matrine (20 mg/kg) and group of blank model. The drug was given once daily for 20 d continuously, and normal saline was used as control. The blood was drawn from the posterior tibial vein of all ducks before treatment (T(0)), after the medication for 5 (T5), 10 (T10), 15 (T15), 20 (T20) d and withdrawl of the drug for 3 d (P3). The serum samples were separated and stored at -70 degrees, DHBV-DNA was detected by the dot-blot hybridization.

RESULTS

After addition of Lip-M and matrine to 2.2.15 cell line for eleven d, the median toxic concentration (TC50) of Lip-M and matrine was 7.29 mg/mL and 1.33 mg/mL respectively. The median concentration (IC50) of Lip-M to inhibit HBsAg and HBeAg expression was 0.078 mg/mL and 3.35 mg/mL respectively. The treatment index (TI) value of Lip-M for HBsAg and HBeAg was 93.46 and 2.17 respectively, better than that of matrine. The DHBV-infected duck model treatment test showed that the duck serum DHBV-DNA levels were markedly reduced in the group of Lip-M (20 mg/kg) after treated by gastric perfusion for 10, 15 and 20 d (0.43+/-0.22 vs 0.95+/-0.18, t = 4.70, P = 0.001<0.01.0.40+/-0.12 vs 0.95+/-0.18, t = 6.34, P = 0.000<0.01. 0.22+/-0.10 vs 0.95+/-0.18, t = 8.30, P = 0.000<0.01), compared to the group of matrine (20 mg/kg) (0.43+/-0.22 vs 0.79+/-0.19, t = 3.17, P = 0.01<0.05. 0.40+/-0.12 vs 0.73+/-0.24, t = 3.21, P = 0.009<0.05. 0.22+/-0.10 vs 0.55+/-0.32, t = 2.27, P = 0.046<0.05.), and the control(0.43+/-0.22 vs 0.98+/-0.29, t = 3.68, P = 0.005<0.01. 0.40+/-0.12 vs 0.97+/-0.30, t = 4.26, P = 0.002<0.01. 0.22+/-0.10 vs 0.95+/-0.27, t = 5.76, P = 0.000<0.01). After the treatment for 20 d and withdrawl of the drug for 3 d, duck serum DHBV-DNA level in the group of Lip-M (10 mg/kg) markedly reduced (0.56+/-0.26 vs 0.95+/-0.38, t = 5.26, P = 0.003<0.05. 0.55+/-0.25 vs 0.95+/-0.38, t = 5.52, P = 0.003<0.05), and the difference was significant as compared with the control (0.56+/-0.26 vs 0.95+/-0.27, t = 2.37, P = 0.042<0.05. 0.55+/-0.25 vs 0.89+/-0.18, t = 2.55, P = 0.031<0.05), but not significant as compared with the group of matrine (20 mg/kg). After withdrawl of the drug for 3 d, the levels of DHBV-DNA did not relapse in both groups of Lip-M.

CONCLUSION

Lip-M can evidently inhibit the replication of hepatitis B virus in vitro and in vivo; its anti-HBV effect is better than that of matrine.