Detailed analysis of structures and formulations of cationic lipids for efficient gene transfer to the lung

Intratumoral delivery of p2CMVmIL-12 using water-soluble lipopolymers

Our objective was to design a water-soluble lipopolymer (WSLP) and an interleukin-12 (IL-12) expression plasmid for enhanced delivery of the IL-12 gene. We synthesized WSLP using branched polyethylenimine (PEI) of 1800 Da and cholesteryl chloroformate, and constructed p2CMVmIL-12, encoding the IL-12 subunits p35 and p40, each under the transcriptional control of a separate cytomegalovirus (CMV) promoter. The percentage of cholesterol conjugated to PEI was about 47% and the average molecular weight of WSLP was approximately 2000 Da. The mean particle size of WSLP/p2CMVmIL-12 complexes formulated in 5% glucose was 26 to 62 nm and xi potential was 8 to 60 mV. The WSLP/p2CMVmIL-12 complexes were nontoxic to CT-26 colon carcinoma cells at the N/P ratio (nitrogen atoms of WSLP/phosphate of plasmid DNA) of 20 and below; PEI25000/pDNA complexes were highly toxic. WSLP/p2CMVmIL-12 complexes demonstrated higher transfection in CT-26 cells compared with the DNA formulations prepared using PEI of molecular weights 1800, 10,000 and 25,000 Da. Transfection efficiency increased with an increase in N/P ratios from 5 to 15, then there was no significant increase in transfection up to the N/P ratio of 30/1. There was an increase in the level of IL-12 when free or complexed p2CMVmIL-12 was compared with free or complexed pIRESmIL-12 in which the p35 and p40 subunits were linked to the internal ribosome entry sites (IRES). At 48 hours post-injection of WSLP/p2CMVmIL-12 complexes into BALB/c mice bearing CT-26 subcutaneous tumors, the levels of IL-12, IFN-gamma, and nitric oxide (NO) in the supernatant of the cultured tumors were higher for the WSLP/p2CMVmIL-12 complexes than for the naked p2CMVmIL-12, WSLP, and 5% glucose injected groups. There was a significant improvement in the survival rate and the inhibition of tumor growth after a single injection of WSLP/p2CMVmIL-12 complexes. We have designed an effective, nontoxic WSLP and an IL-12 expression plasmid with two CMV promoters.

Chitosan as a nonviral gene delivery system. Structure-property relationships and characteristics compared with polyethylenimine in vitro and after lung administration in vivo

Chitosan is a natural cationic linear polymer that has recently emerged as an alternative nonviral gene delivery system. We have established the relationships between the structure and the properties of chitosan-pDNA polyplexes in vitro. Further, we have compared polyplexes of ultrapure chitosan (UPC) of preferred molecular structure with those of optimised polyethylenimine (PEI) polyplexes in vitro and after intratracheal administration to mice in vivo. Chitosans in which over two out of three monomer units carried a primary amino group formed stable colloidal polyplexes with pDNA. Optimized UPC and PEI polyplexes protected the pDNA from serum degradation to approximately the same degree, and they gave a comparable maximal transgene expression in 293 cells. In contrast to PEI, UPC was non toxic at escalating doses. After intratracheal administration, both polyplexes distributed to the mid-airways, where transgene expression was observed in virtually every epithelial cell, using a sensitive pLacZ reporter containing a translational enhancer element. However, the kinetics of gene expression differed - PEI polyplexes induced a more rapid onset of gene expression than UPC. This was attributed to a more rapid endosomal escape of the PEI polyplexes. Although this resulted in a more efficient gene expression with PEI polyplexes, UPC had an efficiency comparable to that of commonly used cationic lipids. In conclusion, this study provides insights into the use of chitosan as a gene delivery system. It emphasises that chitosan is a nontoxic alternative to other cationic polymers and it forms a platform for further studies of chitosan-based gene delivery systems.

High and sustained transgene expression in vivo from plasmid vectors containing a hybrid ubiquitin promoter

Sustained transgene expression will be required for the successful treatment of most genetic diseases being considered for gene therapy. The initially high levels of expression attained with plasmid DNA (pDNA) vectors containing viral promoters, such as that from cytomegalovirus (CMV), decline precipitously to near-background levels within two to three weeks. Here we constructed pDNA vectors containing the human cellular UBB (encoding ubiquitin B; Ub) promoter and evaluated their expression in the mouse lung. Cationic lipid-pDNA complexes were instilled intranasally (IN) or injected intravenously (IV) into immunodeficient BALB/c mice. Chloramphenicol acetyltransferase (CAT) reporter gene expression from the UBB promoter was initially very low at day 2 post-administration, but by day 35 exceeded the level of expression attained from a CMV promoter vector by four- to ninefold. Appending a portion of the CMV enhancer 5' of the UBB promoter (CMV-Ub) increased CAT expression to nearly that of the CMV promoter and expression persisted in the lung for at least 3 months, with 50% of day 2 levels remaining at day 84. In the liver, expression from the CMV-Ub hybrid promoter was sustained for 42 days. As previous studies have shown that eliminating immunostimulatory CpG motifs in pDNA vectors reduces their toxicity, we constructed a CpG-deficient version of the CMV-Ub vector expressing alpha-galactosidase A, the enzyme deficient in Fabry disease, a lysosomal storage disorder. After IN or IV administration, levels of alpha-galactosidase A from this vector were not only undiminished but increased 500% to 1500% by day 35. Our results indicate that CpG-reduced plasmid vectors containing a CMV-Ub hybrid promoter may provide the long-term expression required for a practical gene therapeutic.

Efficiency and toxicity of liposome-mediated gene transfer to corneal endothelial cells

Gene transfer to corneal endothelial cells could be an important advance to modulate functions of these critical cells and is a field of current investigations. The development of gene transfer methods is a prerequisite for gene therapy to realize its full potential. We attempted to investigate and optimize the efficacy and safety of cationic liposome mediated gene transfer into corneal endothelial cells using different lipid formulations. Mono- and polycationic lipids and the neutral helper lipid dioleolphosphotidyl-ethanolamine (DOPE) were used for preparation of cationic liposomes. Six liposomal formulations containing DAC/DOPE 30/70 (DAC 30), DOSGA/DOPE 30/70 (DOSGA 30), DOSGA 100, DMRIE/DOPE 50/50 (DMRIE 50) and SP/DOPE 20/80 (SP 20) were complexed with the pUT 651-plasmid, encoding the E. coli beta-galactosidase gene. Subconfluent primary and passaged bovine corneal endothelial cells (BCEC) were transfected with different amounts of liposomes and DNA or uncomplexed free DNA as control. Quantitative expression of beta-galactosidase was measured using a colorimetric assay. In order to assess the effects on cell viability and growth, a modified acidic phosphatase assay was employed. Differences were detected using these various liposome preparations. Transfection experiments demonstrated the highest gene expression using SP 20> DMRIE 50 ranging at approximately 3 mU per beta-gal per well. Low expression of beta-galactosidase was achieved using DAC 30, DOSGA 30 and DOSGA 100. No beta-galactosidase expression was found in control dishes. There was no difference seen following transfection of primary or subsequent passages of BCEC. As indicated by the acid phosphatase assay, no significant toxicity was detected for the most efficient lipids used. Of the preparations studied, SP 20 appeared as the optimal vehicle for plasmid-mediated transfection of BCEC. The ability to deliver genes to BCEC via liposomes could be valuable, since the use of other vectors for transfection may be limited by undesired effects.

Lipid-mediated ex vivo gene transfer of viral interleukin 10 in rat lung allotransplantation

BACKGROUND

Recent studies suggest that viral interleukin 10 suppresses alloimmune response in transplantation and that cationic lipids are one of the most promising nonviral vehicles for gene therapy. The aim of this study was to examine the effect of ex vivo lipid-mediated viral IL10 gene transfer into rat lung allografts on subsequent rejection.

METHODS

Male F344 rats (RT1lvl) underwent left lung transplantation with allografts from Brown Norway rats (RT1n). Allografts were transvascularly transfected 15 minutes after harvest with 5 mL of 1:20-diluted (group 1, n = 7) or 1:40-diluted (group 2, n = 6) GL67-pCMVievIL-10 complex. Group 3 (n = 7), serving as the control group, received 1:40-diluted GL67-pCF1-chloramphenicol acetyltransferase complex. All allografts were preserved for 3 hours at 10 degrees C before transplantation. In all groups recipients were killed on postoperative day 5. Transgene expression of viral interleukin 10 was assessed by means of both reverse transcriptase-polymerase chain reaction and immunohistochemistry. Histologic rejection score, allograft gas exchange, exhaled nitric oxide level, and allograft cytokine mRNA expression were also assessed.

RESULTS

Dose-dependent transgene expression of viral interleukin 10 was detected by means of both reverse transcriptase-polymerase chain reaction and immunohistochemistry. Allograft gas exchange (PaO2) in groups 1 (114.06 +/- 61.1 mm Hg) and 2 (108.58 +/- 35.7 mm Hg) was significantly better than that in group 3 (66.4 +/- 8.22 mm Hg; P =.020 and P =.023, respectively). The vascular rejection score in group 1 was significantly lower than that in group 3 (P =.032, Kruskal-Wallis test). Exhaled nitric oxide levels in group 2 (5.150 +/- 6.38 ppb) were significantly lower than those in group 3 (13.517 +/- 10.4 ppb; P =.039). Allograft interleukin 2 mRNA expression levels in group 1 (1.123 +/- 0.23 relative units) were significantly lower than those in group 3 (1.753 +/- 0.71 relative units; P =.038 vs group 3).

CONCLUSIONS

Lipid-mediated ex vivo viral IL10 gene transfer into rat lung allografts improved graft gas exchange, reduced histologic rejection scores, downregulated graft interleukin 2 mRNA expression, and reduced exhaled nitric oxide levels by postoperative day 5. These results suggest a therapeutic potential of graft viral IL10 gene transfer as an effective immunosuppressive strategy against lung allograft rejection.

Synthesis of a novel series of cationic lipids that can act as efficient gene delivery vehicles through systematic heterocyclic substitution of cholesterol derivatives

The synthesis of a series of novel cationic lipids through the systematic substitution of cholesterol derivatives that could greatly enhance the delivery and expression of plasmid DNA in vitro and in vivo is described. Two of the newly synthesized lipids, designated as NCC4 and NCC10, were chosen to be studied in detail and gave much higher levels of gene expression than that which could be obtained with some of the conventional cationic polymers and cationic liposomes. In vivo studies with both NCC4 and NCC10 also showed better ability in delivering the reporter gene to the target cells through intrasplenic injection. In addition, by varying the DNA/lipid charge ratios, NCC4 and NCC10 can withstand serum inactivation in vitro. However, this does not correlate with the corresponding increase in the level of gene expression following systemic gene delivery with NCC4 and NCC10 in vivo.

Mitochondria transfection by oligonucleotides containing a signal peptide and vectorized by cationic liposomes

The progress of research in gene therapy allows hope for treatment of mitochondrial genetic disorders provided that efficient methods for gene transfer into mitochondria can be found. In this work, we have used an oligonucleotide coupled covalently to a mitochondria-targeted peptide at one end and a cationic liposome prepared from trimethyl aminoethane carbamoyl cholesterol iodide (TMAEC-Chol) to carry it in living cells. With a fluorescent probe to label the oligonucleotide at the other end and by means of confocal microscopy, we show that such modified oligonucleotides complexed to liposomes enter into the cytoplasm of human fibroblasts in primary culture, and then, after dissociation from the complexes, they penetrate into the mitochondria. The fluorescence was still observed after 8 days, suggesting the continued presence of oligonucleotides. At the concentrations used for this study, the cationic liposomes have practically no effect on cell growth, as revealed by the MTT assay.

Interaction between DNA-cationic liposome complexes and erythrocytes is an important factor in systemic gene transfer via the intravenous route in mice: the role of the neutral helper lipid

Recent studies have indicated that there are many barriers to successful systemic gene delivery via cationic lipid vectors using the intravenous route. The purpose of this study was to investigate the effect of binding and interaction between erythrocytes, a major constituent of blood cells, and the complexes, in relation to the role of the helper lipid, on the in vivo gene delivery to the lung following intravenous injection. We used three types of cationic lipid vectors, DNA-DOTMA/Chol liposome complexes, DNA-DOTMA liposome complexes, and DNA-DOTMA/DOPE liposome complexes. Although the three types of vectors bind to murine blood cells in vivo and in vitro, DOTMA/Chol and DOTMA complexes with a higher in vivo transfection activity do not induce fusion between erythrocytes, whereas DOTMA/DOPE complexes, a less efficient vector in vivo, induce fusion between the erythrocytes after a short incubation period. Pre-incubation of DOTMA/DOPE complexes with erythrocytes significantly reduced the transfection efficiency while DOTMA/Chol- and DOTMA complexes were more resistant to such treatment. The differences in the physicochemical and structural properties of these complexes could explain the differences in interaction with erythrocytes and subsequent gene expression. Lipids in DOTMA/Chol and DOTMA complexes have a stable lamellar structure. However, lipids in DOTMA/DOPE complexes have a highly curved structure with high fluidity. These results indicate that the interaction with erythrocytes depends on the properties of the cationic lipid vectors and this is an important factor for intravenous gene delivery using cationic lipid vectors.

A clinical inflammatory syndrome attributable to aerosolized lipid-DNA administration in cystic fibrosis

Immunologic reactivity to lipid-DNA conjugates has traditionally been viewed as less of an issue than with viral vectors. We performed a dose escalation safety trial of aerosolized cystic fibrosis transmembrane conductance regulator (CFTR) cDNA to the lower airways of eight adult cystic fibrosis patients, and monitored expression by RT-PCR. The cDNA was complexed to a cationic lipid amphiphile (GL-67) consisting of a cholesterol anchor linked to a spermine head group. CFTR transgene was detected in three patients at 2-7 days after gene administration. Four of the eight patients developed a pronounced clinical syndrome of fever (maximum of 103.3EF), myalgias, and arthralgia beginning within 6 hr of gene administration. Serum IL-6 but not levels of IL-8, IL-1, TNF-alpha, or IFN-gamma became elevated within 1-3 hr of gene administration. No antibodies to the cationic liposome or plasmid DNA were detected. We found that plasmid DNA by itself elicited minimal proliferation of peripheral blood mononuclear cells taken from study patients, but led to brisk immune cell proliferation when complexed to a cationic lipid. Lipid and DNA were synergistic in causing this response. Cellular proliferation was also seen with eukaryotic DNA, suggesting that at least part of the immunologic response to lipid-DNA conjugates is independent of unmethylated (E. coli-derived) CpG sequences that have previously been associated with innate inflammatory changes in the lung.

Cationic liposome-mediated gene delivery to the liver and to hepatocellular carcinomas in mice

The potential of cationic liposomes as nonviral vectors for in vivo gene delivery to the liver and to intrahepatic hepatocellular carcinoma (HCC) was investigated. Mice were injected via the tail vein or portal vein with a cationic lipid complexed to plasmid DNA (pDNA) encoding the chloramphenicol acetyltransferase (CAT) reporter gene at various cationic lipid:pDNA molar ratios to analyze the efficiency of gene delivery after intravenous administration. Tail vein injection resulted in high CAT expression levels in lung and spleen and low levels in the liver. Portal vein injection, by comparison, significantly enhanced hepatic reporter gene expression but also resulted in pronounced hepatic toxicity. Gene delivery to intrahepatic tumors produced by intrahepatic injection of human HCC cells was analyzed in nude mice. Tail vein injection as well as portal vein injection resulted in low levels of gene expression in intrahepatic tumors. By comparison, high levels of gene expression were achieved by direct, intratumoral injection of liposome-pDNA complexes, with only minimal expression in the surrounding normal liver. Therefore, direct liposome-pDNA complex injection appears far superior to systemic or portal intravenous administration for gene therapy of localized intrahepatic tumors, and may be a useful adjunct in the treatment of human HCCs.

Cationic lipid-DNA complexes in gene delivery: from biophysics to biological applications

Great expectations from the application of gene therapy approaches to human disease have been impaired by the unsatisfactory clinical progress observed. Among others, the use of an efficient carrier for nucleic acid-based medicines is considered to be a determinant factor for the successful application of this promising therapeutic strategy. The drawbacks associated with the use of viral vectors, namely those related with safety problems, have prompted investigators to develop alternative methods for gene delivery, cationic lipid-based systems being the most representative. This review focuses on the various parameters that are considered to be crucial to optimize the use of cationic lipid-DNA complexes for gene therapy purposes. Particular emphasis is devoted to the analysis of the different stages involved in the transfection process, from the biophysical aspects underlying the formation of the complexes to the different biological barriers that need to be surpassed for gene expression to occur.

Endobronchial transfection of naked viral interleukin-10 gene in rat lung allotransplantation

BACKGROUND

Recent studies suggest that viral interleukin-10 (vIL-10) suppresses alloimmune response in transplantation. Tissue mRNA expression of inducible nitric oxide synthase (iNOS) and exhaled nitric oxide (NO) levels have been observed to increase in lung allograft rejection. The aims of this study were to examine the feasibility of vIL-10 gene transfer into rat lung allografts and to investigate its effect on subsequent allograft rejection.

METHODS

Male Lewis rats (RT1l) underwent left lung transplantation with allografts from Brown Norway rats (RT1n). The donor rats were endobronchially transfected 2 minutes before harvest with 400 microg (group I, n = 5), 600 microg (group II, n = 5), or 800 microg (group III, n = 5) of naked pCMVievIL-10. Group IV (n = 5) animals, serving as control, received 400 microg of naked pCF1-CAT. All recipients were sacrificed on postoperative day 5. Transgene expression of vIL-10 was assessed by both reverse transcriptase-polymerase chain reaction and immunohistochemistry. Allograft gas exchange, exhaled NO level, histologic rejection score, and mRNA expression of graft cyokines were also assessed.

RESULTS

Transgene expression of lung graft vIL-10 was detected by both reverse transcriptase-polymerase chain reaction and immunohistochemistry. The iNOS mRNA expression in groups I, II, and III was significantly lower than that of group IV (p < 0.05, analysis of variance). Exhaled NO levels in groups I, II, and III were significantly lower than in group IV (p < 0.01, analysis of variance). There was no significant difference between groups with respect to gas exchange, peak airway pressure, or histologic rejection score.

CONCLUSIONS

It appears that endobronchial transfection of naked vIL-10 plasmid in a rat lung allotransplant model is feasible and suppresses lung iNOS mRNA expression and exhaled NO levels. An association between iNOS upregulation and high exhaled NO levels in lung allograft resection was also noted.

Key issues in non-viral gene delivery

The future of non-viral gene therapy depends on a detailed understanding of the barriers to delivery of polynucleotides. These include physicomechanical barriers, which limit the design of delivery devices, physicochemical barriers that influence self-assembly of colloidal particulate formulations, and biological barriers that compromise delivery of the DNA to its target site. It is important that realistic delivery strategies are adopted for early clinical trials in non-viral gene therapy. In the longer term, it should be possible to improve the efficiency of gene delivery by learning from the attributes which viruses have evolved; attributes that enable translocation of viral components across biological membranes. Assembly of stable, organized virus-like particles will require a higher level of control than current practice. Here, we summarize present knowledge of the biodistribution and cellular interactions of gene delivery systems and consider how improvements in gene delivery will be accomplished in the future.

The thermotropic phase behavior of cationic lipids: calorimetric, infrared spectroscopic and X-ray diffraction studies of lipid bilayer membranes composed of 1,2-di-O-myristoyl-3-N,N,N-trimethylaminopropane (DM-TAP)

The thermotropic phase behavior of lipid bilayer model membranes composed of the cationic lipid 1,2-di-O-myristoyl-3-N,N,N-trimethylaminopropane (DM-TAP) was examined by differential scanning calorimetry, infrared spectroscopy and X-ray diffraction. Aqueous dispersions of this lipid exhibit a highly energetic endothermic transition at 38.4 degrees C upon heating and two exothermic transitions between 20 and 30 degrees C upon cooling. These transitions are accompanied by enthalpy changes that are considerably greater than normally observed with typical gel/liquid--crystalline phase transitions and have been assigned to interconversions between lamellar crystalline and lamellar liquid--crystalline forms of this lipid. Both infrared spectroscopy and X-ray diffraction indicate that the lamellar crystalline phase is a highly ordered, substantially dehydrated structure in which the hydrocarbon chains are essentially immobilized in a distorted orthorhombic subcell. Upon heating to temperatures near 38.4 degrees C, this structure converts to a liquid-crystalline phase in which there is excessive swelling of the aqueous interlamellar spaces owing to charge repulsion between, and undulations of, the positively charged lipid surfaces. The polar/apolar interfaces of liquid--crystalline DM-TAP bilayers are not as well hydrated as those formed by other classes of phospho- and glycolipids. Such differences are attributed to the relatively small size of the polar headgroup and its limited capacity for interaction with moieties in the bilayer polar/apolar interface.

Enhancement of gene delivery by an analogue of alpha-MSH in a receptor-independent fashion

In order to transfect melanoma specifically by receptor-mediated endocytosis we prepared dioctadecyl aminoglycylspermine (lipospermine)--DNA complexes with [Nle(4),D-Phe(7)]-alpha-MSH(4--10), a pseudo-peptide analogue of alpha-melanocyte stimulating hormone (alpha-MSH) linked to a thiol-reactive phospholipid. With these complexes we obtained an up to 70-fold increase of transfection with B16-F1 melanoma cells. However when B16-G4F, an alpha-MSH receptor negative melanoma cell line was transfected, an up to 700-fold increased transfection efficiency was observed. The peptide hormone analogue was equally efficient when it was only mixed with lipospermine--DNA complexes without covalent coupling. In addition to melanoma cells we also obtained up to 30-fold increased transfection with BN cells (embryonic liver cells). Our data show that an alpha-MSH analogue increased transfection independently of the MSH receptor expression but reaches efficiencies approaching those obtained with peptides derived from viral fusion proteins. The absence of targeting of constructs containing [Nle(4),D-Phe(7)]-alpha-MSH(4-10) can probably be attributed due to the relatively modest number of MSH receptors at the surface of melanoma. We suggest, however, that the peptide hormone analogue used in this study has membrane-active properties and could be of interest as helper agent to enhance non-viral gene delivery presumably by endosomal-destabilizing properties.

Gene medicine : a new field of molecular medicine

Gene therapy has emerged as a new concept of therapeutic strategies to treat diseases which do not respond to the conventional therapies. The principle of gene therapy is to introduce genetic materials into patient cells to produce therapeutic proteins in these cells. Gene therapy is now at the stage where a number of dinical trials have been carried out to patients with gene-deficiency disease or cancer. Genetic materials for gene therapy are generally composed of gene expression system and gene delivery system. For the dinical application of gene therapy in a way which conventional drugs are used, researches have been focused on the design of gene delivery system which can offer high transfection efficiency with minimal toxicity. Currently, viral delivery systems generally provide higher transfection efficiency compared with non-viral delivery systems while non-viral delivery systems are less toxic, less immunogenic and manufacturable in large scale compared with viral systems. Recently, novel strategies towards the design of new non-viral delivery system, combination of viral and non-viral delivery systems and targeted delivery system have been extensively studied. The continued effort in this area will lead us to develop gene medicine as 'gene as a drug' in the near future.

Comprehensive analysis of the acute toxicities induced by systemic administration of cationic lipid:plasmid DNA complexes in mice

A major limitation associated with systemic administration of cationic lipid:plasmid DNA (pDNA) complexes is the vector toxicity at the doses necessary to produce therapeutically relevant levels of transgene expression. Systematic evaluation of these toxicities has revealed that mice injected intravenously with cationic lipid:pDNA complexes develop significant, dose-dependent hematologic and serologic changes typified by profound leukopenia, thrombocytopenia, and elevated levels of serum transaminases indicative of hepatocellular necrosis. Vector administration also induced a potent inflammatory response characterized by complement activation and the induction of the cytokines IFN-gamma, TNF-alpha, IL-6, and IL-12. These toxicities were found to be transient, resolving with different kinetics to pretreatment levels by 14 days posttreatment. The toxic syndrome observed was independent of the cationic lipid:pDNA ratio, the cationic lipid species, and the level of transgene expression attained. Mechanistic studies determined that neither the complement cascade nor TNF-alpha were key mediators in the development of these characteristic toxicities. Administration of equivalent doses of the individual vector components revealed that cationic liposomes or pDNA alone did not generate the toxic responses observed with cationic lipid:pDNA complexes. Only moderate leukopenia was associated with administration of cationic liposomes or pDNA alone, while only mild thrombocytopenia was noted in pDNA-treated animals. These results establish a panel of objective parameters that can be used to quantify the acute toxicities resulting from systemic administration of cationic lipid:pDNA complexes, which in turn provides a means to compare the therapeutic indices of these vectors.

Inhibition of endotoxin-induced lung inflammation by interleukin-10 gene transfer in mice

Interleukin (IL)-10 is an anti-inflammatory cytokine that has great potential for use in the treatment of inflammatory and immune illnesses. In this study, gene transfer was used to induce IL-10 transgene expression in murine lungs for treatment of endotoxin-induced lung inflammation. Gene transfer was performed with a cytomegalovirus (CMV)-IL-10 plasmid with the aid of the liposomal agents LipofectAMINE and N-[1-(2,3-dioleoyl)propyl]-N,N, N-trimethylammonium methylsulfate (DOTAP). Administration of the endotoxin caused a marked increase in lung inflammation as indicated by increased tumor necrosis factor (TNF)-alpha release and neutrophil count. Pretreatment of the mice with IL-10 plasmid with and without LipofectAMINE had no inhibitory effect on lung inflammation and IL-10 transgene expression. LipofectAMINE by itself induced lung inflammation, an effect that was not observed with DOTAP. IL-10 plasmid when codelivered with DOTAP expressed biologically active IL-10 protein and caused a reduction in endotoxin-induced inflammation. Transgene expression was observed as early as 3 h after administration, peaked at 12 h, and declined thereafter. We conclude that IL-10 gene transfer is a feasible approach for the treatment of lung inflammation.

Introduction of the human growth hormone gene into the guinea pig mammary gland by in vivo transfection promotes sustained expression of human growth hormone in the milk throughout lactation

We tested the feasibility of transfecting mammary tissue in vivo with an expression plasmid encoding the human growth hormone (hGH) gene, under the control of the cytomegalovirus promoter. Guinea pig mammary glands were transfected with plasmid DNA infused through the nipple canal and expression was monitored in control and transfected glands by radioimmunoassay of milk samples for hGH. Sustained expression of hGH throughout lactation was attained with a polyion transfection complex shown to be optimal for the transfection of bovine mammary cells, in vitro. However, contrary to expectations, hGH expression was consistently 5- to 10-fold higher when DEAE-dextran was used alone for transfection. Thus polyion complexes which are optimal for the transfection of cells in vitro may not be optimal in vivo. The highest concentrations of hGH in milk were obtained when glands were transfected within 3 days before parturition. This method may have application for studying the biological role or physical properties of recombinant proteins expressed in low quantities, or for investigating the regulation of gene promoters without the need to construct viral vectors or produce transgenic animals.

Characteristics and biodistribution of cationic liposomes and their DNA complexes

We have developed some novel liposome formulations for gene transfection. The formulations consisting of O,O'-ditetradecanoyl-N-(alpha-trimethyl ammonio acetyl) diethanolamine chloride (DC-6-14) as a cationic lipid, phospholipid and cholesterol showed effective gene transfection activity in cultured cells with serum and in vivo, i.e., intraperitoneal injection in mice. In this report, the physicochemical characteristics and biodistribution of the liposomes containing DC-6-14 (DC-6-14 liposomes) as a drug (gene) carrier for gene therapy were investigated in vitro and in vivo. DC-6-14 liposome-DNA complexes were usually thought to have positive surface charge. However, depending on the ratio of DNA to liposomes, zeta-potential of the complexes became negative. The diameter of the complexes also depended on the DNA-liposome ratio, and showed a maximum when their surface potential was neutral. When biodistribution of the complexes was determined after intravenous injection, positively charged complexes showed an immediate lung accumulation. On the other hand, negatively charged complexes did not show lung accumulation. These results have suggested that biodistribution of the DNA-liposome complexes, prepared with DC-6-14 liposomes, depends on their surface charge. Therefore, some surface modification of DC-6-14 liposomes may improve the biodistribution and hence the targetability of their DNA complexes.

Delivery and pathway in MCF7 cells of DNA vectorized by cationic liposomes derived from cholesterol

We have investigated the delivery and the pathway in tumoral MCF7 cells of DNA carried by liposomes prepared from (trimethyl aminoethane carbamoyl cholesterol iodide (TMAE-Chol), a cholesterol-based cationic lipid with a quaternary ammonium on the polar head. The structure of DNA-liposome complexes depends on the length of DNA and on the lipid-DNA charge ratio X. Spherical beads constitute fine structures of the observed complexes even when they appear as aggregates. For oligonucleotide transfer, dissociation from liposomes after transfection, penetration of the oligonucleotides into nuclei, and a long resident time were observed. For plasmid transfer, a correlation between the variation in the transfection level and the ultrastructure of complexes was demonstrated. The results showed a cellular route of lipid/plasmid complexes from the beginning by endocytosis, entrapped into endosomes, released by the latter until entry in the perinuclear area, and then penetration of plasmids inside the nuclei resulting in the observed expression of the beta-galactosidase gene.

Gene transfection activities of amphiphilic steroid-polyamine conjugates

The design and evaluation of a novel potent class of DNA delivery agents based on steroid-polyamine conjugates bearing a flexible linker are reported. The hydrophobic regions are based on steroids, i.e. chlolestane and lithocholic acid motifs. The linker, which couples a hydrophobic steroid and a hydrophilic polyamine, in this study can be regarded as a two-atom extension of the conventional carbamate linker. We found that the gene transfection activity of the steroid-polyamine conjugates is influenced by the polyamine chain length and steroid structure. Molecular modeling of the relevant amphiphilic molecules revealed low-energy structures in which the polyamine chains are folded rather than stretched. This work suggests a significant effect of space-filling, i.e. the shape and orientation of the hydrophilic and hydrophobic regions, upon the efficiency of gene transfection.

Efficient gene transfer to airway epithelium using recombinant Sendai virus

Clinical studies of gene therapy for cystic fibrosis (CF) suggest that the key problem is the efficiency of gene transfer to the airway epithelium. The availability of relevant vector receptors, the transient contact time between vector and epithelium, and the barrier function of airway mucus contribute significantly to this problem. We have recently developed recombinant Sendai virus (SeV) as a new gene transfer agent. Here we show that SeV produces efficient transfection throughout the respiratory tract of both mice and ferrets in vivo, as well as in freshly obtained human nasal epithelial cells in vitro. Gene transfer efficiency was several log orders greater than with cationic liposomes or adenovirus. Even very brief contact time was sufficient to produce this effect, and levels of expression were not significantly reduced by airway mucus. Our investigations suggest that SeV may provide a useful new vector for airway gene transfer.

Lipoplex formation under equilibrium conditions reveals a three-step mechanism

Cellular transfection can be accomplished by the use of synthetic amphiphiles as gene carrier system. To understand the mechanism and hence to improve the efficiency of transfection, insight into the assembly and properties of the amphiphile/gene complex is crucial. Here, we have studied the interaction between a plasmid and cationic amphiphiles, using a monolayer technique, and have examined complex assembly by atomic force microscopy. The data reveal a three-step mechanism for complex formation. In a first step, the plasmids, interacting with the monolayer, display a strong tendency of orientational ordering. Subsequently, individual plasmids enwrap themselves with amphiphile molecules in a multilamellar fashion. The size of the complex formed is determined by the supercoiled size of the plasmid, and calculations reveal that the plasmid can be surrounded by 3 to 5 bilayers of the amphiphile. The eventual size of the transfecting complex is finally governed by fusion events between individually wrapped amphiphile/DNA complexes. In bulk phase, where complex assembly is triggered by mixing amphiphilic vesicles and plasmids, a similar wrapping process is observed. However, in this case, imperfections in this process may give rise to a partial exposure of plasmids, i.e., part of the plasmid is not covered with a layer of amphiphile. We suggest that these exposed sites may act as nucleation sites for massive lipoplex clustering, which in turn may affect transfection efficiency.

Enhanced gene expression in mouse lung after PEI-DNA aerosol delivery

Aerosol gene delivery to the pulmonary system has vast potential for many diseases, including cystic fibrosis and lung cancer. We recently reported that polyethyleneimine (PEI), a cationic polymer, holds promise as a gene delivery vector for transfection in lung by aerosol. To further optimize the gene expression in the lung by aerosol, we utilized 5% CO(2) in air for the nebulization of PEI-DNA complexes. Five percent CO(2)-in-air gave a threefold higher gene expression compared to normal air using the chloramphenicol acetyl transferase (CAT) reporter gene delivered by Aerotech II nebulizer. The delivery of DNA by PEI was dose dependent with the highest expression obtained when 2 mg of DNA in 10 ml was nebulized at a PEI nitrogen:DNA phosphate (N:P) ratio of 10:1. The optimal N:P ratio for lung transfection was found to be between 10:1 and 20:1 using the CAT and luciferase reporter genes. The time-course studies showed the highest expression at 24 h after aerosol delivery and 40-50% of peak level was detectable even after a week. Tissue distribution indicates the expression to be specific to the lung with no detectable expression in any other tissue examined. Histological and biochemical analysis of lungs revealed no evidence of acute inflammation.

Intravascular and endobronchial DNA delivery to murine lung tissue using a novel, nonviral vector

Gene transfer to the lung can be achieved via either the airway or the pulmonary vasculature. We evaluated gene transfer and expression by intravascular and endobronchial routes, using DNA complexed with G9 PAMAM dendrimer or naked plasmid DNA. Intravascular tail vein delivery of dendrimer-complexed pCF1CAT plasmid resulted in high levels of transgene expression in the lung at 12 and 24 hr, followed by a second peak of expression 3 to 5 days after administration. After intravenous administration of the complexes, CAT expression was never observed in organs other than the lung. There were only minimal levels of CAT protein expressed in the lung after intravenous administration of naked plasmid DNA. Repeated intravascular doses of the dendrimer-complexed plasmid, administered four times at 4-day intervals, maintained expression at 15-25% of peak concentrations achieved after the initial dose. Endobronchial delivery of naked pCF1CAT plasmid produced significant amounts of CAT protein in the lung. Comparison of intratracheal and intranasal routes resulted in similar expression levels of CAT in the lung and trachea. However, in juxtaposition to vascular delivery, intranasal delivery of dendrimer-complexed plasmid DNA gave lower levels of CAT expression than that observed with naked plasmid DNA. In situ localization of CAT enzymatic activity suggested that vascular administration seemed to achieve expression in the lung parenchyma, mainly within the alveoli, while endobronchial administration primarily targeted bronchial epithelium. Our results show that intravenously administered G9 dendrimer is an effective vector for pulmonary gene transfer and that transgene expression can be prolonged by repeated administration of dendrimer-complexed DNA.

Gene therapy for cystic fibrosis

The gene for cystic fibrosis was identified in 1989 and this together with the emerging technology of gene therapy heralded a new dawn for the treatment of genetic disease. The initial optimism however gave way to the realisation that gene therapy for cystic fibrosis was unlikely to be straightforward. The lung was considered an ideal organ to target due to ease of access, but subsequent research has shown that the airway surface provides an efficient barrier to topically applied gene transfer agents. A number of Phase I clinical safety trials were carried out through the 1990s and provided proof of concept evidence that delivery of DNA by either viral or non-viral means was safe though not clinically efficacious. Current research is now focusing more on the barriers faced by delivery agents, with the aim that more efficient gene delivery will lead to a gene therapeutic for cystic fibrosis.

Synthesis and biological properties of new glycosidic cationic lipids for DNA delivery

Lipidic glycosides with amino alkyl pendent groups were synthesized and evaluated for in vitro DNA transfection activity. The first representative of this new class of cationic lipids showed good gene delivery and low toxicity to HeLa and 3T3 cells.

Cationic lipid structure and formulation considerations for optimal gene transfection of the lung

Enhanced gene transduction to the lung using cationic lipids could be attained through optimization of the structure of the lipids and the formulation of the cationic lipid:plasmid DNA (pDNA) complexes. We have expanded on our earlier observation of the importance of the structural orientation of the cationic lipid headgroup. Through the synthesis of a number of matched pairs of cationic lipids differing only in the configuration of their headgroup, we confirmed that those harboring a T-shape headgroup are more active than their linear counterparts, at least when tested in the lungs of BALB/c mice. Additionally, we demonstrated that not only are the structural considerations of these cationic lipids important, but also their protonation state, the free base being invariably more active than its salt counterpart. The salt forms of cationic lipids bound pDNA with greater avidity, which may have affected their subsequent intracellular dissolution and transit of the pDNA to the nucleus. Inclusion of a number of frequently used solutes in the vehicle severely inhibited the gene transfection activity of the cationic lipids. The selection of neutral co-lipids was also an important factor for overall transfection activity of the formulation, with significant gains in transfection activity realized when diphytanoylphosphatidylethanolamine or dilinoleoylphosphatidylethanolamine were used in lieu of dioleoylphosphatidylethanolamine. Finally, we showed that a transacylation reaction could occur between the cationic lipid and neutral co-lipid which reduced the transfection activity of the complexes. It is the hope that as our understanding of the many factors that influence the activity of these cationic lipid:pDNA complexes improves, formulations with much greater potency can be realized for use in the treatment of pulmonary diseases.

Pretreatment with cationic lipid-mediated transfer of the Na+K+-ATPase pump in a mouse model in vivo augments resolution of high permeability pulmonary oedema

Resolution of pulmonary oedema is mediated by active absorption of liquid across the alveolar epithelium. A key component of this process is the sodium-potassium ATPase (Na+K+-ATPase) enzyme located on the basolateral surface of epithelial cells and up-regulated during oedema resolution. We hypothesised that lung liquid clearance could be further up-regulated by lipid-mediated transfer and expression of exogenous Na+K+-ATPase cDNA. We demonstrate proof of this principle in a model of high permeability pulmonary oedema induced by intraperitoneal injection of thiourea (2.5 mg/kg) in C57/BL6 mice. Pretreatment of mice (24 h before thiourea) by nasal sniffing of cationic liposome (lipid #67)-DNA complexes encoding the alpha and beta subunits of Na+K+-ATPase (160 microg per mouse), significantly (P<0.01) decreased the wet:dry weight ratios measured 2 h after thiourea injection compared with control animals, pretreated with an equivalent dose of an irrelevant gene. Whole lung Na+K+-ATPase activity was significantly (P<0.05) increased in mice pretreated with Na+K+-ATPase cDNA compared both with untreated control animals as well as animals pretreated with the irrelevant gene. Nested RT-PCR on whole lung homogenates confirmed gene transfer by detection of vector-specific mRNA in three of four mice studied 24 h after gene transfer. This demonstration of a significant reduction in pulmonary oedema following in vivo gene transfer raises the possibility of gene therapy as a novel, localised approach for pulmonary oedema in clinical settings such as ARDS and lung transplantation.

Nature of linkage between the cationic headgroup and cholesteryl skeleton controls gene transfection efficiency

Three novel cationic cholesterol derivatives with different modes of linkage between the cationic headgroup and the cholesteryl backbone have been synthesized and used as mixtures with 1, 2-dioleoyl-L-alpha-glycero-3-phosphatidyl ethanolamine (DOPE) for liposome-mediated gene transfection. A pronounced improvement in gene transfer efficiency was observed when the cationic center was appended to the cholesteryl backbone using an ether linkage as opposed to when the linkages were based on either ester or urethane groups. Amphiphiles with ether links such as cholest-5-en-3beta-oxyethane-N,N,N-trimethyl ammonium bromide (2) and cholest-5-en-3beta-oxyethane-N,N-dimethyl-N-2-hydroxyethyl ammonium bromide (3) showed transfection efficiencies considerably greater than commercially available gene transfer reagents. Notably, the transfection ability of 2 with DOPE in the presence of serum was significantly greater than Lipofectamine((R)) and Lipofectin((R)). Interestingly, 3 did not require the helper lipid DOPE for transfection. This suggests that these newly described cholesterol-based amphiphiles should be very promising in liposome-mediated gene transfection. The advantage that the ether linkage possesses would be important in the design of newer, more efficient cholesterol-based delivery reagents.

Toxicity of cationic liposome-DNA complex in lung isografts

BACKGROUND

Cationic lipids have been successfully employed as vectors for gene transfer in lung grafts, yet those lipid vectors have potential toxicity. Furthermore, the optimal concentration of cationic lipids for gene transfection to lung grafts has not been determined. We evaluated liposome concentration/toxicity relationships in an in vivo rat lung transplantation model.

METHODS

Left lungs were harvested and infused via the pulmonary artery with chloramphenicol acetyl-transferase (CAT)-DNA/lipid 67 (cationic lipid)/dioleoylphosphatidylethanolamine complex (4:1:2 in a final concentration ratio). Donor lungs were allocated into six groups according to lipid 67 concentration: group 1, 0 microM (control); group 2, 10 microM; group 3, 50 microM; group 4, 100 microM; group 5, 250 microM; group 6, 500 microM. Forty-eight hours after orthotopic transplantation, the recipient contralateral right main pulmonary artery and bronchus were ligated. The graft was ventilated with 100% oxygen for 5 min. Arterial blood gas analysis (PaO2, PaCO2), peak airway pressure (PAP), and CAT activity of the grafts were measured.

RESULTS

Recipient survival, and PaO2, PAP, and CAT levels correlated with the lipid-DNA complex concentration. The grafts in groups 4-6 were more injured as evidenced by decreased PaO2 and increased PAP levels in comparison to the control group. CAT level was significantly lower in group 2 than in groups 3-6.

CONCLUSIONS

The pulmonary toxicity of cationic lipid is dose-dependent. The balance between lung graft function and transgene expression is optimal at a lipid 67 concentration of 50 microM.

Intravesical liposome-mediated interleukin-2 gene therapy in orthotopic murine bladder cancer model

Using a novel orthotopic MBT-2 murine bladder tumor model, we evaluated the feasibility of intravesical gene therapy utilizing a cationic liposome, DMRIE/DOPE. Superficial bladder tumors were consistently established by intravesical instillation of 5x10(5) MBT-2 cells in syngeneic C3H female mice. In situ gene transfer to bladder tumors was accomplished via intravesical instillation of plasmid DNA/DMRIE/DOPE lipoplex. Beta-Galactosidase (beta-gal) gene expression was preferentially evident in bladder tumors and was present for at least 7 days after a single 30 min in situ transfection. Murine interleukin-2 (IL-2) gene was used for treatment of 3-day-old pre-established bladder tumors. Forty percent of animals treated with IL-2 gene were completely free of tumors by 60 days following the initial tumor implantation, while all control groups treated with beta-gal gene died. Those animals initially cured of pre-established tumors were completely resistant to a subsequent tumor re-challenge and their splenocyte-derived cytotoxic T lymphocytes were shown to be specific to MBT-2 cells, indicating that immunological memory against MBT-2 tumors was elicited by the treatment. These results demonstrate the possibility of an effective clinical application of this in situ intravesical IL-2 gene delivery system to high-risk superficial bladder tumors, obviating a need for tumor procurement and ex vivo gene transfer.

Transforming growth factor-beta1 gene transfer ameliorates acute lung allograft rejection

BACKGROUND

The aim of the current work was to study the feasibility of functional gene transfer using the gene encoding for transforming growth factor-beta1, a known immunosuppressive cytokine, on rat lung allograft function in the setting of acute rejection.

METHODS

The rat left lung transplant technique was used in all experiments, with Brown Norway donor rats and Fischer recipient rats. After harvest, left lungs were transfected ex vivo with either sense or antisense transforming growth factor-beta1 constructs complexed to cationic lipids, then implanted into recipients. On postoperative days 2, 5, and 7, animals were put to death, arterial oxygenation measured, and acute rejection graded histologically.

RESULTS

On postoperative day 2, there were no differences in acute rejection or lung function between animals treated with transforming growth factor-beta1 and control animals. On postoperative day 5, oxygenation was significantly improved in grafts transfected with the transforming growth factor-beta1 sense construct compared with antisense controls (arterial oxygen tension = 411 +/- 198 vs 103 +/- 85 mm Hg, respectively; P =.002). Acute rejection scores from lung allografts were also significantly improved, corresponding to decreases in both vascular and airway rejection (vascular rejection scores: 2.0 +/- 0. 5 vs 2.8 +/- 0.6; P =.04; airway rejection scores: 1.3 +/- 0.7 vs 2. 3 +/- 0.8, respectively; P =.02). The amelioration of acute rejection was temporary and decreased by postoperative day 7.

CONCLUSIONS

The feasibility of using gene transfer techniques to introduce novel functional genes in the setting of lung transplantation is demonstrated. In this model of rat lung allograft rejection, gene transfer of transforming growth factor-beta1 resulted in temporary but significant improvements in lung allograft function and acute rejection pathology.

Structural basis of DOTMA for its high intravenous transfection activity in mouse

Eleven structural analogues of two known cationic lipids, N-[1-(2, 3-dioleyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTMA) and N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTAP) were synthesized and utilized to evaluate the structural characteristics of DOTMA for its high intravenous transfection activity. Using a CMV-driven expression system and luciferase gene as a reporter, the transfection activity of these analogues was evaluated in mice using tail vein injection. Results concerning the structure-activity relationship with regard to the influence of the backbone, relative position between head group and the hydrophobic chains on the backbone, linkage bonds, as well as the composition of the aliphatic chains revealed that cationic lipids which give a higher in vivo transfection activity share the following structural characteristics: (1) cationic head group and its neighboring aliphatic chain being in a 1,2-relationship on the backbone; (2) ether bond for bridging the aliphatic chains to the backbone; and (3) paired oleyl chains as the hydrophobic anchor. Cationic lipids without these structural features had lower in vivo transfection activity. These structural characteristics, however, did not significantly influence their in vitro transfection activity. The contribution that cationic lipids make to the overall in vivo transfection activity is likely to be determined by the structure of DNA/lipid complexes and by the outcome of the interaction between the DNA/lipid complexes and blood components upon intravenous administration.

Synthesis and evaluation of vitamin D-based cationic lipids for gene delivery in vitro

A new panel of steroidal cationic lipids has been synthesized for gene delivery. Using commercially available vitamin D2 (calciferol) or vitamin D3 (cholecalciferol) as hydrophobic motifs and a variety of cationic head groups as binding sites for negatively charged phosphate groups in DNA, we demonstrated that the transfection activity of the synthetic vitamin D-based cationic lipids 1d, 2d formulated with dioleoylphosphatidylethanolamine (DOPE) as a co-lipid is comparable to that of 3-(-[N-N',N'-dimethylaminoethane)carbamoyl]cholesterol (DC-Chol). These synthetic lipids are effective in transfecting a variety of cell lines. These results suggest that vitamin D-based cationic lipids are useful transfection reagents for in vitro gene transfer studies.

Synthesis and transfection properties of novel non-toxic monocationic lipids. Variation of lipid anchor, spacer and head group structure

This report describes the synthesis and the transfection properties of novel monocationic non-toxic lipids. We have carried out structural variations in all three units of the transfection lipid, the lipid anchor, the spacer moiety and the positively charged head group. Our results lead to the conclusion that systematic modification of structural subunits is a promising way to enhance the transfection efficiency.

Physical stability and in-vitro gene expression efficiency of nebulised lipid-peptide-DNA complexes

The lower respiratory tract provides a number of disease targets for gene therapy. Nebulisation is the most practical system for the aerosolisation of non-viral gene delivery systems. The aerosolisation process represents a significant challenge to the maintenance of the physical stability and biological activity of the gene vector. In this study we investigate the role of a condensing polycationic peptide on the stability and efficiency of nebulised lipid-DNA complexes. Complexes prepared from the cationic lipid 1, 2-dioleoyl-3-trimethylammonium propane (DOTAP) and plasmid DNA (pDNA) at mass (w/w) ratios of 12:1, 6:1 and 3:1, and complexes prepared from DOTAP, the polycationic peptide, protamine, and pDNA (LPD) at 3:2:1 w/w ratio were nebulised using a Pari LC Plus jet nebuliser. Samples from the nebuliser reservoir (pre- and post-nebulisation) and from the aerosol mist were collected and investigated for changes, including: particle diameter, retention of in-vitro transfection activity and the relative concentration and nature of the complexed pDNA remaining after the nebulisation procedure. The process of jet nebulisation adversely affected the physical stability of lipid:pDNA complexes with only those formulated at 12:1 w/w DOTAP:pDNA able to maintain their pre-nebulisation particle size distribution (145+/-3 nm pre-nebulisation vs. 142+/-2 nm aerosol mist) and preserve significant pDNA integrity in the reservoir (35% of pre-nebulisation pDNA band intensity). The LPD complexes were smaller (102+/-1 nm pre-nebulisation vs. 113+/-2 nm aerosol mist) with considerably greater retention of pDNA integrity in the reservoir (90% of pre-nebulisation pDNA band intensity). In contrast the concentration of pDNA in the aerosol mist for both the 12:1 w/w DOTAP:pDNA and LPD complexes were significantly reduced (10 and 12% of pre-nebulised values, respectively). Despite reduced pDNA concentration the transfection (% cells transfected) mediated by aerosol mist for the nebulised complexes was comparatively efficient (LPD aerosol mist 26 vs. 40% for pre-nebulised complex; the respective values for 12: 1 w/w DOTAP:pDNA were 12 vs. 28%). The physical stability and biological activity of nebulised lipid:pDNA complexes can be improved by inclusion of a condensing polycationic peptide such as protamine. The incorporation of the peptide precludes the use of potentially toxic excesses of lipid and charge and may act as a platform for the covalent attachment of peptide signals mediating sub-cellular targetting.

Systemic administration of cationic phosphonolipids/DNA complexes and the relationship between formulation and lung transfection efficiency

Performances of cationic lipid formulations for intravenous gene delivery to mouse lungs have been previously reported. We report in this study that cationic phosphonolipids, when appropriately formulated, can be good synthetic vectors for gene delivery to lung after intravenous administration. One of our reagents, GLB43, was capable of mediating a 500-fold higher expression in the lungs of mice than could be obtained with free pDNA alone (P=0.018). We demonstrate that the most important parameters for cationic phosphonolipid transfection activity after systemic administration are the chemical structure of the cationic phosphonolipid, the lipid to DNA charge ratio and the inclusion of co-lipid in the formulation. We report using a luciferase reporter gene that transfection activity in vivo 24 h after cationic phosphonolipid systemic administration could not be predicted from in vitro analysis. In contrast to in vitro studies, cationic phosphonolipids including the oleyl acyl chains (GLB43) were more effective than its analogue with the myristyl acyl chains (GLB73). Using pathological analysis of animal livers, we demonstrate that the toxicity level was correlated with the lipoplex formulation and the lipid to DNA ratio.

Factors governing the assembly of cationic phospholipid-DNA complexes

The interaction of DNA with a novel cationic phospholipid transfection reagent, 1,2-dioleoyl-sn-glycero-3-ethylphosphocholine (EDOPC), was investigated by monitoring thermal effects, particle size, vesicle rupture, and lipid mixing. By isothermal titration calorimetry, the heat of interaction between large unilamellar EDOPC vesicles and plasmid DNA was endothermic at both physiological and low ionic strength, although the heat absorbed was slightly larger at the higher ionic strength. The energetic driving force for DNA-EDOPC association is thus an increase in entropy, presumably due to release of counterions and water. The estimated minimum entropy gain per released counterion was 1.4 cal/mole- degrees K (about 0.7 kT), consistent with previous theoretical predictions. All experimental approaches revealed significant differences in the DNA-lipid particle, depending upon whether complexes were formed by the addition of DNA to lipid or vice versa. When EDOPC vesicles were titrated with DNA at physiological ionic strength, particle size increased, vesicles ruptured, and membrane lipids became mixed as the amount of DNA was added up to a 1.6:1 (+:-) charge ratio. This charge ratio also corresponded to the calorimetric end point. In contrast, when lipid was added to DNA, vesicles remained separate and intact until a charge ratio of 1:1 (+:-) was exceeded. Under such conditions, the calorimetric end point was 3:1 (+:-). Thus it is clear that fundamental differences in DNA-cationic lipid complexes exist, depending upon their mode of formation. A model is proposed to explain the major differences between these two situations. Significant effects of ionic strength were observed; these are rationalized in terms of the model. The implications of the analysis are that considerable control can be exerted over the structure of the complex by exploiting vectorial preparation methods and manipulating ionic strength.

Immunogene therapy for murine melanoma using recombinant adenoviral vectors expressing melanoma-associated antigens

Adenoviral vectors expressing tumor-associated antigens can be used to evoke a specific immune response and inhibit tumor growth. In this study, we tested the efficacy of adenoviral vectors encoding human gp100 (Ad2/hugp100), murine gp100 (Ad2/mugp100), or murine TRP-2 (Ad2/muTRP-2) for their ability to elicit a specific cellular immune response and inhibit the growth of B16 melanoma tumor cells in the mouse. C57BL/6 mice were immunized with Ad2/hugp100, Ad2/mugp100, or Ad2/muTRP-2 either 2 weeks prior to B16-F10 tumor challenge (prophylactic treatment) or 3 days after tumor challenge (active treatment). Ad2/hugp100 and Ad2/muTRP-2 administered to two or more intradermal (i.d.) sites inhibited subsequent subcutaneous tumor growth in > or = 80% of the mice and elicited an antigen-specific cytotoxic T lymphocyte response, whereas other administration routes were not as effective. Ad2/mugp100 administered to two i.d. sites did not inhibit tumor growth or provoke cellular immunity. Immunization was less effective with active treatment where tumor growth was not significantly inhibited by a single dose of either Ad2/muTRP-2 or Ad2/hugp100. However, increasing the number of intradermal immunization sites and the number of doses resulted in progressive improvements in protection from tumor growth in the active treatment model. In conclusion, breaking host tolerance to elicit protective immunity by using adenoviral vectors expressing melanoma-associated antigens is dependent upon the choice of antigen, the site of administration, and the number of doses. These observations provide insights into the clinical applicability of adenoviral vaccines for immunotherapy of malignant diseases.

Reduced inflammatory response to plasmid DNA vectors by elimination and inhibition of immunostimulatory CpG motifs

An inflammatory response is invariably associated with administration of gene transfer complexes composed of cationic lipids and plasmid DNA (pDNA). In the lung, an influx of neutrophils and elevated levels of several proinflammatory cytokines such as TNF-alpha, IFN-gamma, IL-6, and IL-12 characterize this dose-dependent response. The induction of these cytokines was shown previously to be due in part to the presence of unmethylated CpG dinucleotides in the bacterially derived pDNA. We have eliminated 270 of 526 CpG dinucleotides in a reporter plasmid (pCFA-CAT) and tested the inflammatory response to cationic lipid:pDNA complexes containing the modified vector (pGZA-CAT) after intravenous (i.v.) or intranasal (i.n.) delivery into BALB/c mice. Compared to the unmodified vector, the CpG-reduced pGZA-CAT was found to be significantly less immunostimulatory, as the levels of IL-12, IFN-gamma, and IL-6 in the serum 24 h after i.v. delivery were reduced by 40 to 75%. Similar reductions in cytokine levels were also observed in the bronchoalveolar lavage fluids (BALF) after i.n. administration, while the levels of reporter gene expression were not affected by the modifications. We have also investigated known inhibitors of the CpG signaling pathways in order to decrease the inflammatory response. Two such inhibitors, chloroquine and quinacrine, greatly reduced the induction of IL-12 from mouse spleen cells in vitro and inhibited cytokine production in the lung by approximately 50% without affecting gene expression. These results illustrate that use of a less immunostimulatory pDNA vector or inhibitors of CpG immunostimulation can reduce significantly the toxicity associated with cationic lipid:pDNA complexes thereby increasing the therapeutic index of this synthetic gene transfer vector.

Anti-inflammatory gene therapy directed at the airway epithelium

Cystic fibrosis (CF) is characterised by chronic airway inflammation. Pro-inflammatory mediators in the lung are regulated by the transcription factor nuclear factor kappa B (NFkappaB). We have assessed the effect of adenovirus and liposome-mediated overexpression of the NFkappaB inhibitor IkappaBalpha, as well as liposome-mediated transfection with oligonucleotides resembling NFkappaB consensus binding sites (decoys) in a cystic fibrosis airway epithelial cell line (CFTE). Electrophoretic mobility shift assays (EMSA) were used to assess NFkappaB activity and secretion of the pro-inflammatory cytokine interleukin-8 (IL-8) was measured by ELISA. At a MOI of 30, Ad-IkappaBalpha significantly decreased IL-8 secretion to 60% and 43% of control unstimulated and TNF-alpha stimulated cells, respectively. At this MOI, approximately 70% of cells are transduced. EMSA showed an approximately 50% decrease in NFkappaB activation. Liposome-mediated transfection of IkappaBalpha did not reduce IL-8 secretion, probably due to low transfection efficiency (approximately 5% of cells). Liposome-mediated transfection of CFTE cells with rhodamine-labeled decoy oligonucleotides indicated a transfection efficiency close to 100%. TNF-alpha stimulated IL-8 secretion was reduced by approximately 40% using this approach. EMSA confirmed a significant decrease of NFkappaB activation. Decoy oligonucleotides may be a promising approach for reduction of NFkappaB-mediated pulmonary inflammation. Gene Therapy (2000) 7, 306-313.

Cationic lipid-mediated gene transfer to the growing murine and human airway

Gene therapy in patients with cystic fibrosis may need to be commenced before the onset of lung disease which may be evident as early as 4 weeks after birth. We assessed the efficacy of cationic lipid-mediated transfer of a reporter gene, chloramphenicol acetyltransferase, in the growing murine and human respiratory tract. Gene expression was greater in adult mice (greater than 8 weeks old) compared with 9- and 16-day-old animals, despite a relatively greater proportion of complex delivered to the younger mice. Subsequent experiments compared 16-day-old and adult mice. Whilst higher gene expression occurred in the parenchyma compared with conducting airways in both groups, significantly greater expression was seen in the conducting airway of adult mice compared with 16-day-old animals. This expression persisted beyond 18 days in the adults but was undetectable in the younger group at this time-point. In an ex vivo model there was no difference in gene expression between the two groups. Further, no differences were observed in gene expression between growing (age 5 weeks to 14 years 8 months) and adult human lung tissue in either parenchyma or conducting airway. These data suggest age-dependent differences in gene transfer in vivo, which are not seen in an ex vivo setting. Proof-of-principle has been demonstrated for cationic-lipid mediated gene transfer to the growing human lung. Gene Therapy (2000) 7, 273-278.

Biodistribution and feasibility of non-viral IGF-I gene transfers in thermally injured skin

Gene therapy using cationic liposomes containing cDNA is a relatively new approach with great potential; however, little is known about the mechanisms of dermal gene transfer, its biodistribution, systemic transfection, and cellular uptake. This study identifies mechanisms, transfection rates, and biodistribution of liposomal gene transfers in the skin of thermally injured rats using cDNA gene constructs coding for insulin-like growth factor-I (IGF-I) and Lac Z. Male Sprague-Dawley rats (350 to 375 g) were given a 60% total body surface area full-thickness scald burn that was followed by weekly subcutaneous injections of normal saline (control, n = 10), liposomes plus 0.2 microg Lac Z cDNA construct driven by a cytomegalovirus (CMV) promoter (vehicle, n = 10), or liposomes containing 2.2 microg cDNA coding for IGF-I plus 0.2 microg Lac Z cDNA construct driven by a CMV promoter (IGF-I cDNA, n = 10). Gene transfection was determined by histochemical and luminescent beta-galactosidase assays of blood, skin, liver, spleen, and kidney. Transcription of IGF-I cDNA to IGF-I mRNA was determined in skin cells by Northern blot analyses. Levels of IGF-I protein in blood, skin, liver, spleen, and kidney were measured by radioimmunoassay. The biological activity of the translated IGF-I was evaluated by the mitogenic activity in dermal cells and the rate of re-epithelization. Gene transfection was observed only in skin cells. The expression of IGF-I mRNA increased in skin cells of burned rats receiving liposomes containing the IGF-I cDNA construct compared with liposomes without the construct or normal saline. IGF-I protein levels in the skin of rats receiving the IGF-I cDNA was 176 +/- 4 ng/ml compared with 105 +/- 6 ng/ml for liposomes alone or 90 +/-3 ng/ml for saline (p < 0.05). The translated IGF-I protein was found biologically active in the skin by increasing skin cell proliferation and accelerating re-epithelization 33 days after thermal injury (p < 0.05). No systemic transfection could be detected. Skin cells transfected with liposomes encapsulating the IGF-I cDNA constructs increased the expression of IGF-I mRNA transcript and the expression of a biologically active IGF-I protein. Liposomes containing the cDNA coding for IGF-I present an effective approach to gene therapy in the skin.