Two methods for quantifying DNA extracted from poly(lactide-co-glycolide) microspheres

Robust mucosal and systemic responses against HTLV-1 by delivery of multi-epitope vaccine in PLGA nanoparticles

In this investigation, the immunogenicity of HTLV-1 fusion epitope-loaded PLGA nanoparticles (NPs) was assessed in the absence or presence of co-encapsulated CpG ODN adjuvant, in a mice model. For this purpose, the multi-epitope chimera including Tax, env, and gag immunodominant HTLV-1 epitopes was encapsulated in biodegradable PLGA NPs with or without CpG adjuvant. PLGA nanospheres produced by a double emulsion method had a size of <200 nm, and encapsulation efficiency of chimera antigen was 85%. The release profile of radiolabeled chimera indicated that only 17.4% and 20.1% of chimera were released from PLGA NPs without or with co-encapsulated CPG ODN during one month, respectively. The PLGA formulations significantly elevated titers of IgG1, IgG2a, and sIgA antibodies, as well as IL-10, and IFN-γ cytokines and also reduced the amount of TGF-β1 production relative to the other vaccines. Additionally, co-delivery of chimera and CpG ODN in PLGA NPs significantly promoted cellular and mucosal responses compared to the incorporation of CpG and chimera antigen. In summary, these results revealed that the sustained release of chimera from PLGA as an efficient polymeric system elicited potent cell-mediated and mucosal immunity without inflammatory responses against HTLV-1. Therefore, the proper design of vaccine formulation and immunization strategy are crucial factors to construct an efficient vaccine.

Chitosan-HPMC-blended microspheres as a vaccine carrier for the delivery of tetanus toxoid

The purpose of this research was to develop a suitable and alternate adjuvant for the tetanus toxoid (TT) vaccine that induces long term immunity after a single-dose immunization. In our study, the preformulation studies were carried out by using different ratios (7/3, 8/2, and 9/1) of chitosan-hydroxypropyl methylcellulose (HPMC)-blended empty microspheres. Moreover, TT was stabilized with heparin (at heparin concentrations of 1%, 2%, 3%, and 4% w/v) and encapsulated in ideal chitosan - HPMC (CHBMS) microspheres, by the water-in-oil-in-water (W/O/W) multiple emulsion method. The vaccine entrapment and the in vitro release efficiency of the CHBMS was evaluated for a period of 90 days. The release of antigens from the microspheres was determined by ELISA. Antigen integrity was investigated by SDS-PAGE. From the optimization studies, it was found that a chitosan/HPMC ratio of 8/2 produced a good yield, with microspheres that were spherical, regular and uniformly-sized. In the CHBMS, a heparin concentration of 3% w/v resulted in well-sustained antigen delivery for a period of 90 days. It was found that the characteristics of initial release could be observed in 2 days, followed by a constant release, and an almost 100% complete release in 90 days. From the in vitro release characteristics, the ideal batch of CHBMS (3% w/v heparin) was evaluated for in vivo studies by the antibody induction method. The antibody levels were measured for different combinations for the period of 9 months, and finally, with a second booster dose after 1 year. In conclusion, it was observed that CHBMS (combination-1) resulted in the antibody level of 4.5 IU/mL of guinea pig serum, and the level was 3.5 IU/mL for the Central Research Institute's alum-adsorbed tetanus toxoid (CRITT) (combination 2), after 1 year, with a second booster dose. This novel approach of using CHBMS may have potential advantages for single-step immunization with vaccines.

Preparation and in vitro characterisation of Ehrlichia ruminantium plasmid DNA and proteins encapsulated into and DNA adsorbed onto biodegradable microparticles

Four E. ruminantium 1H12 open reading frames and their proteins known to protect sheep against heartwater needle challenge were encapsulated into, or adsorbed onto poly(d,l-lactide-co-glycolide) microparticles. Microspheres with smooth surface and smaller than 5 μm diameters were produced, with high adsorption and encapsulation efficiencies. Gel electrophoresis showed that neither encapsulation nor adsorption affected the stability of the DNA or proteins. Cationic microparticles released ∼40% of plasmid DNA on day 1 while PLGA 50:50-COOH microparticles co-encapsulating plasmid DNA and polyvinyl alcohol only started to release from days 12-28. Recombinant proteins were released from PLGA 85:15 and homopolymer R 203 S microparticles in a biphasic manner with a high initial burst release (∼45-80%). In contrast, PLGA 50:50 microparticles had low (15-65%) initial burst release followed by (25-80%) release by days (days 28-42). A cocktail of these microparticles could therefore be used as single-dose auto-booster vaccine.

Alginate microspheres encapsulated with autoclaved Leishmania major (ALM) and CpG-ODN induced partial protection and enhanced immune response against murine model of leishmaniasis

A suitable adjuvant and delivery system are needed to enhance efficacy of vaccines against leishmaniasis. In this study, alginate microspheres as an antigen delivery system and CpG-ODN as an immunoadjuvant were used to enhance immune response and induce protection against an experimental autoclaved Leishmania major (ALM) vaccine. Alginate microspheres were prepared by an emulsification technique and the characteristics of the preparation such as size, encapsulation efficiency and release profile of encapsulates were studied. Mean diameter of microspheres was determined using SEM (Scanning Electron Microscopy) and particle size analyzer. The encapsulation efficiency was determined using Lowry protein assay method. The integrity of ALM antigens was assessed using SDS-PAGE. Mean diameter of microspheres was 1.8±1.0μm. BALB/c mice were immunized three times in 3-weeks intervals with ALM+CpG-ODN loaded microspheres [(ALM+CpG)(ALG)], ALM encapsulated alginate microspheres [(ALM)(ALG)], (ALM)(ALG)+CpG, ALM+CpG, ALM alone or PBS. The intensity of infection induced by L. major challenge was assessed by measuring size of footpad swelling. The strongest protection was observed in group of mice immunized with (ALM+CpG)(ALG). The groups of mice received (ALM+CpG)(ALG), (ALM)(ALG)+CpG, (ALM)(ALG) and ALM+CpG were also showed a significantly (P<0.05) smaller footpad swelling compared with the group that received either ALM alone or PBS. The mice immunized with (ALM+CpG)(ALG) or ALM+CpG showed the significantly (P<0.05) highest IgG2a/IgG1 ratio. The IFN-γ level was significantly (P<0.0001) highest in group of mice immunized with either (ALM)(ALG)+CpG or ALM+CpG. It is concluded that alginate microspheres and CpG-ODN adjuvant when are used simultaneously induced protection and enhanced immune response against ALM antigen.

Immunization against leishmaniasis by PLGA nanospheres encapsulated with autoclaved Leishmania major (ALM) and CpG-ODN

Various adjuvants and delivery systems have been evaluated for increasing the protective immune responses against leishmaniasis and mostly have been shown not to be effective enough. In this study, poly(D,L-lactide-co-glycolide) (PLGA) nanospheres as an antigen delivery system and CpG-ODN as an immunoadjuvant have been used for the first time to enhance the immune response against autoclaved Leishmania major (ALM). PLGA nanospheres were prepared by a double-emulsion (W/O/W) technique. Particulate characteristics were studied by scanning electron microscopy and particle size analysis. Mean diameter of ALM + CpG-ODN-loaded nanospheres was 300 ± 128 nm. BALB/c mice were immunized three times in 3-week intervals using ALM plus CpG-ODN-loaded nanospheres [(ALM + CpG-ODN)(PLGA)], ALM encapsulated PLGA nanospheres [(ALM)(PLGA)], (ALM)(PLGA) + CpG, ALM + CpG, ALM alone, or phosphate buffer solution (PBS). The intensity of infection induced by L. major challenge was assessed by measuring size of footpad swelling. The strongest protection, showed by significantly (P<0.05) smaller footpad, was observed in mice immunized with (ALM + CpG-ODN)(PLGA). The (ALM)(PLGA), (ALM)(PLGA) + CpG, and ALM + CpG were also showed a significantly (P<0.05) smaller footpad swelling compared to the groups received either PBS or ALM alone. The mice immunized with (ALM + CpG-ODN)(PLGA), (ALM)(PLGA) + CpG, and ALM + CpG showed the highest IgG2a/IgG1 ratio, interferon-γ production, and lowest interleukin-4 production compared to the other groups. It is concluded that when both PLGA nanospheres and CpG-ODN adjuvants were used simultaneously, it induce stronger immune response and enhance protection rate against Leishmania infection.

Induction of cell-mediated immune responses to peptide antigens of P. vivax in microparticles using intranasal immunization

T-cells play a critical role in resistance to malaria, not only because they function as helper cells for an antibody response, but also because they serve as effector cells. Such cellular immunity is directly implicated in protection from sporozoites as well as from blood stage parasites. The aim of this study was to induce cell mediated immune responses to peptide antigens of Plasmodium vivax co-encapsulated with CpG oligodeoxynucleotide (ODN) in microparticles. In the present study, we have investigated the immunomodulatory effects of two CpG adjuvants, CpG 1826 and CpG 2006 to the five peptide antigens of Plasmodium vivax derived from circumsporozoite protein, merozoite surface protein-1, apical membrane antigen-1 and gametocyte surface antigen (Pvs24) in microparticle delivery. The T-cell proliferation response study of the cells collected from spleen, lamina propria and peyer's patches showed significantly high (p<0.001) stimulation index when primed with peptide antigens in microparticles co-encapsulating CpG ODN adjuvant as compared to peptide alone primed mice. The cytokine measurement profile of IFN-gamma, TNF-alpha, IL-2, IL-4 and IL-10 in culture supernatants of cells primed with peptide antigens in microparticles co-encapsulating CpG ODN showed higher levels of IFN- gamma followed by TNF-alpha and IL-2, with relatively low levels of IL-4 and IL-10.

Central nervous system delivery of large molecules: challenges and new frontiers for intrathecally administered therapeutics

IMPORTANCE OF THE FIELD

Therapeutic proteins and DNA constructs offer promise for the treatment of central nervous system disorders, yet significant biological barriers limit the ability of these molecules to reach the central nervous system from the bloodstream. Direct administrations to the cerebrospinal fluid (intrathecal administration) comprise an emerging field to facilitate the efficient delivery of these biological macromolecules to central nervous system tissues.

AREAS COVERED IN THIS REVIEW

Previous reports from 1990 to the present time describing the interactions and turnover of the cerebrospinal fluid within the intrathecal space, characterizations of the effects that therapeutic proteins and DNA have shown after intrathecal delivery through a lumbar route, and reports of emerging technologies to address the limitations of intrathecally administered macromolecules are reviewed.

WHAT THE READER WILL GAIN

This review provides an overview of the limitations that must be overcome for intrathecally administered biological macromolecules and the recent advances and promising approaches for surmounting these limitations.

TAKE HOME MESSAGE

Emerging approaches that stabilize and sustain the delivery of intrathecally administered biological macromolecules may enhance substantially the clinical relevance of promising therapeutic proteins and DNA constructs for the treatment of various central nervous system disorders.

Comparison of post-emulsification freeze drying or spray drying processes for the microencapsulation of plasmid DNA

In this work, methods used to microencapsulate plasmid DNA in a biodegradable polymer were compared for their effects on the physicochemical characteristics of DNA-loaded microparticles and on the release and integrity of encapsulated DNA. Microparticles were formulated by either w/o/w emulsification and freeze-drying (EFD) or by w/o/w emulsification and spray-drying (ESD). The influence of both manufacturing processes on particle morphology, charge, release characteristics and biological activity of encapsulated DNA was evaluated. Particles produced by emulsification/spray-drying exhibited more diversity in shape and size than those produced by emulsification/freeze-drying. These particles also exhibited higher plasmid DNA encapsulation efficiency than particles produced by emulsification/freeze-drying. The fractional DNA release rates were similar over the first 25 days for both formulations, release rate declining more rapidly at later times for the ESD product. Mammalian cell transfection assays confirmed the biological activity of encapsulated DNA extracted from both types of particles, with significantly higher transfection levels being observed for ESD particles. Application of a double emulsion (w/o/w) before spray drying resulted in higher encapsulation levels (&gt; 90%) relative to previous literature values, which used single (w/o) emulsions before spray drying. The emulsification/spray-drying technique described here appears to be a rapid and efficient method for the preparation of PLGA microparticles loaded with plasmid DNA.

Spray drying of siRNA-containing PLGA nanoparticles intended for inhalation

Local delivery of small interfering RNA (siRNA) to the lungs constitutes a promising new area in drug delivery. The present study evaluated parameters of importance for spray drying of siRNA-loaded poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles (NPs) into nanocomposite microparticles intended for inhalation. The spray drying process was optimised using a statistical design of experiment and by evaluating powder characteristics upon systematic variation of the formulation parameters. Concentration, carbohydrate excipient (trehalose, lactose and mannitol) and the ratio of NP to excipient were varied to monitor the effects on moisture content, particle morphology, particle size and powder yield. The identified optimum conditions were applied for spray drying of siRNA-loaded nanocomposite microparticles, resulting in a product with a low water content (0.78% w/w) and an aerodynamic particle diameter considered suitable for inhalation. The use of mannitol in the formulation allowed a significantly lower moisture content than trehalose and lactose. The inclusion of 50% (w/w) or higher amounts of NPs resulted in a marked change in the surface morphology of the spray-dried particles. Importantly, the integrity and biological activity of the siRNA were preserved during the spray drying process. In conclusion, the present results show that spray drying is a suitable technique for producing nanocomposite microparticles comprising siRNA-containing PLGA NPs for potential use in inhalation therapy.

Induction of mucosal and systemic humoral immune responses in murine system by intranasal immunization with peptide antigens of P. vivax and CpG oligodeoxynucleotide (ODN) in microparticle delivery

In the present study we have investigated the immunomodulatory effects of two adjuvants, CpG 1826 (two copies of CpG motifs) and CpG 2006 (three copies of CpG motifs) to the five peptide antigens of Plasmodium vivax derived from circumsporozoite protein (CSP), merozoite surface protein-1 (MSP1#1, MSP1#23), apical membrane antigen-1 (AMA-1) and gametocyte surface antigen (Pvs24) in alum and microparticle formulations, using intramuscular and intranasal routes of immunization. Alum formulation without CpG ODN generated low serum IgG and IgA antibody titers and the predominant IgG isotypes were IgG1 but with the addition of CpG ODN (1826 or 2006), the antibody titers were increased by four fold with the predominance of IgG2a/2b isotypes. The SIgA peak titers in lung and intestinal washes were significantly increased with the intranasal mode of administration. Specific activity measurement was done to calculate for the accurate amounts of total serum IgG, IgA and SIgA in washes and showed direct correlation between antibody titer and its concentration. High titer anti-Pvs24 antibodies have significant inhibitory effects on parasite development in the mosquito midgut when tested in membrane feeding assays. The immunofluorescence results show that the peptide specific antisera reacted with the air-dried parasite antigens isolated from P. vivax patients. The present study demonstrates that intranasal route of immunization appears to be an alternate mode of inducing protective immunity in P. vivax malaria.

Intranasal administration of peptide antigens of HIV with mucosal adjuvant CpG ODN coentrapped in microparticles enhances the mucosal and systemic immune responses

The mucosal immune system acts as a first line of defense against infection caused by luminal pathogens. Because HIV is transmitted primarily via mucosal associated tissues, particularly with sexual transmission, understanding antiviral immunity present at these sites is important. As most of the peptide antigens show poor immunogenicity when immunized alone but after incorporating the same peptide antigens along with adjuvant CpG ODN in microparticles has shown enhanced immunogenicity in the murine model. In the present study we have investigated the immunomodulatory effects of two adjuvants, CpG 1826 and CpG 2006 (Class B, Also known as type K) to the four peptide antigens of HIV such as envelope glycoproteins gp41 Leucine Zipper, gp41 fusion domain and gp120-C2 as well as regulatory protein (Nef) in microparticles, exploring nasal route with single immunization schedule. Peptide (s) alone in the microparticles elicited low peptide specific IgG and IgA peak titres in the sera, whereas the inclusion of CpG ODN with peptides in microparticles significantly enhanced peptide specific IgG and IgA peak titres and such responses were sustained for longer durations. Similarly higher SIgA response was achieved in the mucosal washes with CpG encapsulated in microparticles. Such presence of SIgA in washes was further correlated with the presence of secretory component (SC) in the respective washes. Both adjuvants induced excellent peptide specific IgG and IgA immune responses. Thus the overall study highlighted the importance of CpG ODNs as a mucosal adjuvant for weaker peptide antigens and thus can explore for developing peptide based vaccine against HIV.

Preparation and Characterization of Cationic PLA-PEG Nanoparticles for Delivery of Plasmid DNA

The purpose of the present work was to formulate and evaluate cationic poly(lactic acid)-poly(ethylene glycol) (PLA-PEG) nanoparticles as novel non-viral gene delivery nano-device. Cationic PLA-PEG nanoparticles were prepared by nanoprecipitation method. The gene loaded nanoparticles were obtained by incubating the report gene pEGFP with cationic PLA-PEG nanoparticles. The physicochemical properties (e.g., morphology, particle size, surface charge, DNA binding efficiency) and biological properties (e.g., integrity of the released DNA, protection from nuclease degradation, plasma stability, in vitro cytotoxicity, and in vitro transfection ability in Hela cells) of the gene loaded PLA-PEG nanoparticles were evaluated, respectively. The obtained cationic PLA-PEG nanoparticles and gene loaded nanoparticles were both spherical in shape with average particle size of 89.7 and 128.9 nm, polydispersity index of 0.185 and 0.161, zeta potentials of +28.9 and +16.8 mV, respectively. The obtained cationic PLA-PEG nanoparticles with high binding efficiency (>95%) could protect the loaded DNA from the degradation by nuclease and plasma. The nanoparticles displayed sustained-release properties in vitro and the released DNA maintained its structural and functional integrity. It also showed lower cytotoxicity than Lipofectamine 2000 and could successfully transfect gene into Hela cells even in presence of serum. It could be concluded that the established gene loaded cationic PLA-PEG nanoparticles with excellent properties were promising non-viral nano-device, which had potential to make cancer gene therapy achievable.

A freeze-dried formulation of bacteriophage encapsulated in biodegradable microspheres

With the emergence of widespread antibiotic resistance, there has been renewed interest in the use of bacteriophages. While their potency, safety and specificity have underpinned their clinical potential, to date, little work has been focussed on their formulation with respect to controlled release and/or passive targeting. Here, we show that bacteriophages selective for Staphylococcus aureus or Pseudomonas aeruginosa can be encapsulated into biodegradable polyester microspheres via a modified w/o/w double emulsion-solvent extraction protocol with only a partial loss of lytic activity. Loss of lytic activity could be attributed to the exposure of the bacteriophages to the water-dichloromethane interface, with the lyophilization process itself having little effect. The microspheres were engineered to have an appropriate size and density to facilitate inhalation via a dry-powder inhaler and fluorescently labeled bacteriophages were distributed entirely within the internal porous matrix. The release profile showed a burst release phase (55-63% release within 30 min), followed by a sustained release till around 6h, as appropriate for pulmonary delivery. Despite the poor shelf-life of the formulation, the work is proof-of-concept for the formulation and controlled delivery of bacteriophages, as suitable for the treatment of bacterial lung infections.

Prime-boost Vaccination based on DNA and Protein-loaded Microspheres for Tuberculosis Prevention

We evaluated the use of a vaccine formulation based on a mixture of two different PLGA microspheres, composed by faster and slower release profiles, containing DNA encoding hsp65 and the recombinant hsp65 protein, respectively, aiming to DNA priming and protein boost after a single dose vaccination. The combination of PLGA50:50 microspheres containing DNA-hsp65 and trehalose dimycolate (TDM) with PLGA75:25 microspheres containing recombinant hsp65 (prime-boost Me) was able to induce high levels of anti-hsp65 specific antibodies. The serum levels of these specific antibodies remained high during 90 days after vaccination, whereas the DNA Me formulation based only in DNA-hsp65 plus TDM-loaded microspheres was not able to sustain the high antibody levels during the same period. Production of IFN-gamma was significant in animals vaccinated with both formulations, while the prime-boost Me vaccinated mice sustained higher levels of this cytokine during all the evaluation period. Thus, prime-boost strategy by using biodegradable microspheres seems to be a promising strategy to stimulate long-lasting immune response.

An effective method of DNA extraction for bioleaching bacteria from acid mine drainage

An effective and versatile method for microorganism lysis and direct extraction of DNA from bioleaching bacteria was developed using pure cultures and an acid mine drainage (AMD) sediment sample. In the described method, microorganisms are treated at three different incubation temperatures: boiling water incubation for 6-10 min, followed by 60 +/- 5 degrees C for 30 min, then 72 degrees C for 30 min. The extracted DNA is purified using a phenol/chloroform/alcohol mixture and precipitated in absolute alcohol. The 16S ribosomal RNA (rRNA) and gyrB genes of the pure cultures were amplified using the polymerase chain reaction (PCR) and differentiated using repetitive intergenic DNA sequences amplification (Rep-PCR). For the AMD sediment sample, the 16S rRNA and gyrB genes of the amplicons were digested with Hin6I and MspI, and the restriction fragment length polymorphism analysis patterns were used as a fingerprint to discern community diversity. The results indicated that this method is a versatile, reproducible, effective, and rapid technique for routine DNA extraction from bioleaching bacteria. The low cost of this method also makes it attractive for large-scale studies.

High loading efficiency and tunable release of plasmid DNA encapsulated in submicron particles fabricated from PLGA conjugated with poly-L-lysine

Poly(lactic-co-glycolic acid) (PLGA) particles have been widely explored as vehicles for delivery of plasmid DNA to mammalian cells both in vitro and in vivo. Achieving high incorporation efficiencies and control over release kinetics are significant challenges in encapsulating hydrophilic molecules such as DNA within submicron particles fabricated from PLGA. This study explored two modifications in the preparation of submicron particles to specifically address these challenges. Firstly, we compared homogenization and sonication as energy sources for emulsification. It was demonstrated that particles prepared with homogenization resulted in higher encapsulation efficiency and a linear release profile of DNA as compared to particles prepared with sonication, which exhibited lower encapsulation efficiency and a burst release. Also investigated was conjugation of poly-L-lysine to PLGA (PLGA-PLL) to create an electrostatically favorable interaction between the carrier material and the DNA. Particles fabricated with high weight percentages of PLGA-PLL/PLGA resulted in remarkably increased loading (>90%). Additionally, the release profile could be dictated by the quantity of PLGA-PLL incorporated into the particles. Particles incubated in vitro on COS-7 cells were able to transfect cells. These results demonstrated that DNA encapsulation and release were modulated by the method of fabrication.

Tissue distribution of DNA-Hsp65/TDM-loaded PLGA microspheres and uptake by phagocytic cells

This study aimed to demonstrate that microspheres, used as delivery vehicle of DNA-Hsp65/TDM [plasmid DNA encoding heat shock protein 65 (Hsp65) coencapsulated with trehalose dimycolate (TDM) into PLGA microspheres], are widely spread among several organs after intramuscular administration in BALB/c mice. In general, we showed that these particles were phagocytosed by antigen presenting cells, such as macrophages and dendritic cells. Besides, it was demonstrated herein that draining lymph node cells presented a significant increase in the number of cells expressing costimulatory molecules (CD80 and CD86) and MHC class II, and also that the administration of the DNA-Hsp65/TDM and vector/TDM formulations resulted in the up-regulation of CD80, CD86 and MHC class II expression when compared to control formulations (vector/TDM and empty). Regarding the intracellular trafficking we observed that following phagocytosis, the microspheres were not found in the late endosomes and/or lysosomes, until 15 days after internalization, and we suggest that these constructions were hydrolysed in early compartments. Overall, these data expand our knowledge on PLGA [poly (lactic-co- glycolic acid)] microspheres as gene carriers in vaccination strategies, as well as open perspectives for their potential use in clinical practice.

Characterization of particles fabricated with poly(D, L-lactic-co-glycolic acid) and an ornithine-histidine peptide as carriers of oligodeoxynucleotide for delivery into primary dendritic cells

We report the formulation of particles to deliver oligodeoxynucleotides (ODN) into primary murine dendritic cells (DCs), the most potent antigen-presenting cells (APCs) known, using poly(D,L-lactic-co-glycolic acid) (PLGA) and a small cationic peptide. PLGA polymer and the ODN were fabricated into nano-sized spherical particles with the aid of O10H6 (O = ornithine, H = histidine). We have previously determined that O10H6 condenses DNA and is less toxic to DCs than a similar lysine-based peptide. The colloidal particles are stabilized by negative surface potentials. The peptide and the ODN can be detected in the fabricated particles with reflectance infrared spectroscopy. Significant ODN uptake can be observed in DCs exposed to the particles. Confocal imaging studies reveal that ODN can be internalized and escape from lysosomes in DCs. Taken together, these data suggest that combining PLGA and O10H6 is a feasible method to generate ODN-containing nano-sized particles for applications in DCs.

Chemical adjuvants for plasmid DNA vaccines

Plasmid DNA vaccines are a promising modality for immunization against a variety of human pathogens. Immunization via multiple routes with plasmid DNA can elicit potent cellular immune responses, and these immunogens can be administered repeatedly without inducing anti-vector immunity. Nonetheless, the immunogenicity of plasmid DNA vaccines has been limited by problems associated with delivery. A number of adjuvants have been designed to improve plasmid DNA immunogenicity, either by directly stimulating the immune system or by enhancing plasmid DNA expression. Chemical adjuvants for enhancing plasmid DNA expression include liposomes, polymers, and microparticles, all of which have shown promise for enhancing the expression and immunogenicity of plasmid DNA vaccines in animal models. Micro- and nanoparticles have not been shown to enhance immune responses to plasmid DNA vaccines. However, formulation of plasmid DNA with some non-particulate polymeric adjuvants has led to a statistically significant enhancement of immune responses. Further development of these technologies will significantly improve the utility of plasmid DNA vaccination.

Comparison of different delivery systems of DNA vaccination for the induction of protection against tuberculosis in mice and guinea pigs

The great challenges for researchers working in the field of vaccinology are optimizing DNA vaccines for use in humans or large animals and creating effective single-dose vaccines using appropriated controlled delivery systems. Plasmid DNA encoding the heat-shock protein 65 (hsp65) (DNAhsp65) has been shown to induce protective and therapeutic immune responses in a murine model of tuberculosis (TB). Despite the success of naked DNAhsp65-based vaccine to protect mice against TB, it requires multiple doses of high amounts of DNA for effective immunization. In order to optimize this DNA vaccine and simplify the vaccination schedule, we coencapsulated DNAhsp65 and the adjuvant trehalose dimycolate (TDM) into biodegradable poly (DL-lactide-co-glycolide) (PLGA) microspheres for a single dose administration. Moreover, a single-shot prime-boost vaccine formulation based on a mixture of two different PLGA microspheres, presenting faster and slower release of, respectively, DNAhsp65 and the recombinant hsp65 protein was also developed. These formulations were tested in mice as well as in guinea pigs by comparison with the efficacy and toxicity induced by the naked DNA preparation or BCG. The single-shot prime-boost formulation clearly presented good efficacy and diminished lung pathology in both mice and guinea pigs.

Poly(D,L-lactide-co-glycolide acid) nanoparticles for DNA delivery: Waiving preparation complexity and increasing efficiency

When designing a nonviral gene delivery system based on polymeric nanoparticles (NPs), it is important to keep in mind obstacles associated with future clinical applications. Simplifying the procedure of NPs production and taking toxicity into account are the most important issues that need to be addressed. Toxicity concerns in clinical trials may be raised when using additives such as cationic polymers/lipids, buffering reagents, and proteins. Therefore, the aim of this study was to simplify the formulation of poly (lactide-co-glycolide) acid NPs by shortening steps such as sonication time and by avoiding the use of additives while preserving its efficiency. NPs (300 nm) were formulated using a modified w/o/w technique with DNA entrapment efficiency of 80%. Once achieving such NPs, formulation parameters such as DNA loading, release kinetics, DNA integrity and bioactivity, uptake by cells, and toxicity were addressed. The NPs were readily taken by several cell lines and were localized mostly in their endo-lysosomal compartments. The NPs did not affect cells viability. Most importantly, transfection studies in COS-7 and Cf2th cells resulted with a 250-fold protein expression levels when compared with the control. These expression levels are higher than ones achieved with more complicated NPs systems, demonstrating the efficiency of our simplified NPs for gene delivery.

PLGA microcapsules with novel dimpled surfaces for pulmonary delivery of DNA

We describe the fabrication of DNA-loaded poly(lactic-co-glycolic acid) (PLGA) microcapsules with novel surface morphologies that will be of use in pulmonary delivery. Our approach was to examine surface morphology and DNA encapsulation efficiency as a function of primary emulsion stability; using two surfactant series based on hydrophile-lipophile balance and hydrophobe molecular weight. Hydrophilic non-ionic surfactants yielded the most stable water-in-dichloromethane emulsions (HLB values >8). These surfactants normally favor convex (o/w) interfacial curvatures and therefore this atypical behavior suggested a relatively high surfactant solvation in the dichloromethane 'oil' phase. This was consistent with the large fall in the glass transition temperature for microspheres prepared with Tween 20, which therefore efficiently penetrated the PLGA matrix and acted as a plasiticizer. Blends of Pluronic triblock copolymers performed poorly as water-in-dichloromethane emulsifiers, and were therefore used to generate hollow microspheres ('microcapsules') with low densities (0.24 g/cm(3)). Although the Pluronic-stabilized emulsions resulted in lower DNA loading (15-28%), microspheres (approximately 8 microm) with novel dimpled surfaces were fabricated. The depth and definition of the dimples was greatest for triblock copolymers with high MW hydrophobe blocks. By cascade impaction, the geometric mean weight diameter of the microcapsules was 3.43 microm, suggesting that they will be of interest as biodegradable pulmonary delivery vehicles.

Microemulsion and diafiltration approaches: An attempt to maximize the global yield of DNA-loaded nanospheres

The yield of DNA-loaded nanospheres in its widest definition includes encapsulation efficiency and the integrity of the loaded molecules plus the production yield of fabricated nanospheres. The former aspect could be considerably improved by adopting the microemulsion concept to enhance the stability of the primary emulsion during the preparation of nanospheres by the double emulsion solvent-removal method. The droplet size of the mentioned emulsion was monitored by means of photon electron correlation spectroscopy and could serve as an index for emulsion fineness and stability. DNA stability as a function of applied mechanical stress was monitored by horizontal agarose gel electrophoresis. The impact of the primary emulsion on nanosphere porosity was assessed as well. Regarding the second aspect of the global yield of nanospheres, i.e. production yield, a modified diafiltration technique was adopted for the washing and recovery processes in comparison with the traditional and for the conservation of particle size characteristics of the recovered nanospheres.

In vitro release of plasmid DNA from oligo(poly(ethylene glycol) fumarate) hydrogels

This research investigates the release of plasmid DNA in vitro from novel, injectable hydrogels based on the polymer oligo(poly(ethylene glycol) fumarate) (OPF). These biodegradable hydrogels can be crosslinked under physiological conditions to physically entrap plasmid DNA. The DNA release kinetics were characterized fluorescently with the PicoGreen and OliGreen Reagents as well as through the use of radiolabeled plasmid. Further, the ability of the released DNA to be expressed was assessed through bacterial transformations. It was found that plasmid DNA can be released in a sustained, linear fashion over the course of 45-62 days, with the release kinetics depending upon the molecular weight of the poly(ethylene glycol) from which the OPF was synthesized. Two formulations of OPF were synthesized from poly(ethylene glycol) of a nominal molecular weight of either 3.35K (termed OPF 3K) or 10K (termed OPF 10K). By the time the gels had completely degraded, 97.8+/-0.3% of the initially loaded DNA was recovered from OPF 3K hydrogels, with 80.8+/-1.9% of the initial DNA retaining its double-stranded form. Likewise, for OPF 10K gels, 92.1+/-4.3% of the initially loaded DNA was recovered upon complete degradation of the gels, with 81.6+/-3.8% of the initial DNA retaining double-stranded form. Experiments suggest that the release of plasmid DNA from OPF hydrogels is dominated by the degradation of the gels. Bacterial transformation results indicated that the DNA retained bioactivity over the course of 42 days of release. Thus, these studies demonstrate the potential of OPF hydrogels in controlled gene delivery applications.

The Challenge to Measure Cell Proliferation in Two and Three Dimensions

Various assays, using different strategies, are available for assessing cultured cell proliferation. These include measurement of metabolic activity (tetrazolium salts and alamarBlue), DNA quantification using fluorophores (Hoechst 33258 and PicoGreen), uptake of radioactively-labeled DNA precursors such as [3H]thymidine, and physical counting (hemocytometer). These assays are well established in characterizing cell proliferation in two-dimensional (2D), monolayer cultures of low cell densities. However, increasing interest in 3D cultures has prompted the need to evaluate the effectiveness of using these assays in high cell density or 3D cultures. We show here that typical cell proliferation assays do not necessarily correlate linearly with increasing cell densities or between 2D and 3D cultures, and are either not suitable or only rough approximations in quantifying actual cell numbers in a culture. Prudent choice of techniques and careful interpretation of data are therefore recommended when measuring cell proliferation in high cell density and 3D cultures.

Formulations containing poly(lactide-co-glycolide) and plasmid DNA expression vectors

DNA expression vectors have the potential to be useful therapeutics for a wide variety of applications. However, development has been hindered by the lack of systems that provide protection from nuclease-based attack, enable cell or tissue localisation, promote adequate gene expression or provide for controlled release. At least one synthetic polymer, poly(lactide-co-glycolide) (PLG), may provide benefit in this regard. This polymer has a history of safe use in humans, has been demonstrated effective as a delivery system, its use is not hindered by composition patents, and Good Manufacturing Practices grade material is readily available from commercial sources. Safety and applicability to clinical medicine have been proven by use of the polymer as a microparticle delivery vehicle for peptides (luteinizing hormone releasing hormone agonist peptides; Lupron Depot [TAP Pharmaceuticals]; Zoladex [AstraZeneca]) and proteins (human growth hormone recombinant protein, Nutropin Depot [Genentech]). This report focuses on the expanding field of PLG-based DNA delivery and provides a review on research and clinical experience with PLG-plasmid formulations.

Poly (D, L-lactide-co-glycolide)/DNA microspheres to facilitate prolonged transgene expression in airway epithelium in vitro, ex vivo and in vivo

Repeat administration of gene therapy for cystic fibrosis is likely to be essential for long-term clinical efficacy. This may be minimized by the use of slow-release gene transfer preparations with more prolonged expression and longer dosing intervals for the patient. Poly(D-L-lactide-co-glycolide) (PLG) is a biodegradable and biocompatible polymer that has been used to encapsulate plasmid DNA. PLG-DNA microspheres were generated and characterized with respect to morphology, size (80% of particles <5.2 microm), and encapsulation efficiency (50.7+/-2.3%, n=6). Gel electrophoresis of DNA re-extracted from the microspheres confirmed that despite a decrease in the proportion of supercoiled conformation, it had not been degraded by the preparation process. Gene transfer efficiency was tested using microspheres encapsulating the reporter gene beta-galactosidase in vitro on Cos 7 cells and a CF airway epithelial line (CFTEo approximately ) and ex vivo in a sheep tracheal (s.t.) model. In both cases, transgene expression was significantly (P<0.01) lower at the first time point tested (24 h in vitro, 48 h ex vivo) compared to lipid-#67-mediated gene transfer. However, PLG-mediated expression in vitro was sustained at 48 h, while lipid #67-mediated expression levels had dropped significantly (P<0.05) to 50.3+/-13.7 and 38.2+/-2.7% (Cos 7 and CFTEo approximately cells, respectively) of the 24-h level. This pattern was also seen in the s.t. model where at 72 h, PLG-mediated expression was 125.4+/-7.2% of the 48-h level demonstrating significantly (P<0.05) better retention of transfection efficiency than lipid #67, where levels had fallen to approximately half the 48 h level. By 96 h, expression was still retained in the PLG-transfected group (87.3+/-12.5% of 48 h expression) but was undetectable in the lipid -#67-transfected s.t. Finally, PLG microspheres, encapsulating the reporter gene chloramphenicol transferase (CAT, 80 microg) were instilled intranasally into Balb/C mice. Compared to lipid-#67-mediated delivery, where whole lung CAT expression was highest at 48 h (13.7 x 10(3)+/-0.05 CAT U/microg protein, n=6) and then not detectable at further time points, CAT expression was not detectable in PLG-transfected mice at 48 h, but was detectable at 7, 14 and 21 days after transfection. These data demonstrate that PLG-mediated gene transfer can produce prolonged gene expression in airway epithelia. However, gene transfer efficiency still requires significant improvement.

Loading of plasmid DNA into PLGA microparticles using TROMS (Total Recirculation One-Machine System): evaluation of its integrity and controlled release properties

Loading plasmid DNA into poly(ester) microparticles usually involves the formation of a multiple emulsion, using homogenisation techniques such as sonication or Ultra-Turrax. These procedures may negatively affect the integrity of the macromolecule and consequently its activity. The aim of this study was to prepare and evaluate DNA-loaded microparticles by TROMS (Total Recirculation One-Machine System), a new procedure that is based on the formation of a multiple emulsion by the injection of the phases under a turbulent regime. Microparticles were prepared with either Resomer) RG 502 (MP 502) or RG 756 (MP 756) and DNA loading was quantified fluorimetrically. DNA loading in MP 756 was almost twice as high as in MP 502 (510 vs. 285 ng/mg, respectively). Under both formulations, the loaded plasmid was released while maintaining its integrity for at least 24 days (MP 502) and 40 days (MP 756). Finally, the transfection efficiency was studied after injection of the microparticles (MP 502) into rat skeletal muscle and compared with naked DNA injection. Injection of naked DNA (150 microg DNA per muscle) achieved higher but variable expression levels that decreased after 3 weeks. In contrast, the muscles injected with microparticles (6.8 microg DNA per muscle) showed lower but homogeneous expression values, which were maintained for at least 3 weeks.