Constitutive and high gene expression in the diaminopimelate pathway accelerates ε-poly-L-lysine production in Streptomyces albulus

Streptomyces albulus NBRC14147 produces a homopoly(amino acid), ε-poly-L-lysine (ε-PL). Due to its antibiotic activity, thermostability, biodegradability, and non-toxicity to humans, ε-PL is used as a food preservative. In this study, homology searches of diaminopimelate (DAP) pathway genes (dapB and dapE), in an S. albulus genome database, were shown to encode predicted enzymes using dapB or dapE in Escherichia coli strain complementation assays. We observed that dapB and dapE transcriptional levels were weak during ε-PL production stages. Therefore, we strengthened this expression using an ermE constitutive promoter. Engineered strains generated faster growth and ε-PL production rates when compared with the control strain. Moreover, maximum ε-PL yields in S. albulus, where dapB was constitutively expressed, were approximately 14% higher when compared with the control strain. These findings showed that enhanced lysine biosynthetic gene expression generated faster and higher ε-PL production levels.

Antibacterial activity of epsilon-poly-l-lysine produced by Stenotrophomonas maltophilia HS4 and Paenibacillus polymyxa HS5, alone and in combination with bacteriophages

Over the past decades, antibiotic resistance has become a major clinical problem, and searching for new therapeutic strategies seems to be necessary. Using novel natural compounds, antimicrobial peptides, and bacteriophages is the most promising solution. In this study, various cationic metabolite-producer bacteria were isolated from different soil samples. Two isolates were identified as Stenotrophomonas maltophilia HS4 (accession number: MW791428) and Paenibacillus polymyxa HS5 (accession number: MW791430) based on biochemical characteristics and phylogenetic analysis using 16S rRNA gene sequences. The cationic compound in the fermentation broth was precipitated and purified with sodium tetraphenylborate salt. The purified cationic peptide was confirmed to be epsilon-poly-l-lysine by structural and molecular analysis using High-Performance Liquid Chromatography, Sodium dodecyl-sulfate-polyacrylamide gel electrophoresis, and Fourier-transform infrared spectroscopy. The antibacterial activity of epsilon-poly-l-lysine was evaluated against Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, Enterococcus faecalis ATCC 29212, Serratia marcescens ATCC 13880, and Klebsiella pneumoniae ATCC 13883 by microdilution method. Furthermore, the antibacterial effects of purified epsilon-poly-l-lysine in combination with two long non-contractile tail bacteriophages against vancomycin-resistant Enterococcus faecalis and colistin-resistant Klebsiella pneumoniae were investigated. The results indicated great antibacterial activity of epsilon-poly-l-lysine which was produced by two novel bacteria. The epsilon-poly-l-lysine as a potent cationic antimicrobial peptide is demonstrated to possess great antimicrobial activity against pathogenic and also antibiotic-resistant bacteria.

PolyICLC Exerts Pro- and Anti-HIV Effects on the DC-T Cell Milieu In Vitro and In Vivo

Myeloid dendritic cells (mDCs) contribute to both HIV pathogenesis and elicitation of antiviral immunity. Understanding how mDC responses to stimuli shape HIV infection outcomes will inform HIV prevention and treatment strategies. The long double-stranded RNA (dsRNA) viral mimic, polyinosinic polycytidylic acid (polyIC, PIC) potently stimulates DCs to focus Th1 responses, triggers direct antiviral activity in vitro, and boosts anti-HIV responses in vivo. Stabilized polyICLC (PICLC) is being developed for vaccine adjuvant applications in humans, making it critical to understand how mDC sensing of PICLC influences HIV infection. Using the monocyte-derived DC (moDC) model, we sought to describe how PICLC (vs. other dsRNAs) impacts HIV infection within DCs and DC-T cell mixtures. We extended this work to in vivo macaque rectal transmission studies by administering PICLC with or before rectal SIVmac239 (SIVwt) or SIVmac239ΔNef (SIVΔNef) challenge. Like PIC, PICLC activated DCs and T cells, increased expression of α₄β₇ and CD169, and induced type I IFN responses in vitro. The type of dsRNA and timing of dsRNA exposure differentially impacted in vitro DC-driven HIV infection. Rectal PICLC treatment similarly induced DC and T cell activation and pro- and anti-HIV factors locally and systemically. Importantly, this did not enhance SIV transmission in vivo. Instead, SIV acquisition was marginally reduced after a single high dose challenge. Interestingly, in the PICLC-treated, SIVΔNef-infected animals, SIVΔNef viremia was higher, in line with the importance of DC and T cell activation in SIVΔNef replication. In the right combination anti-HIV strategy, PICLC has the potential to limit HIV infection and boost HIV immunity.

Targeting caspase-3 as dual therapeutic benefits by RNAi facilitating brain-targeted nanoparticles in a rat model of Parkinson's disease

The activation of caspase-3 is an important hallmark in Parkinson’s disease. It could induce neuron death by apoptosis and microglia activation by inflammation. As a result, inhibition the activation of caspase-3 would exert synergistic dual effect in brain in order to prevent the progress of Parkinson’s disease. Silencing caspase-3 genes by RNA interference could inhibit the activation of caspase-3. We developed a brain-targeted gene delivery system based on non-viral gene vector, dendrigraft poly-L-lysines. A rabies virus glycoprotein peptide with 29 amino-acid linked to dendrigraft poly-L-lysines could render gene vectors the ability to get across the blood brain barrier by specific receptor mediated transcytosis. The resultant brain-targeted vector was complexed with caspase-3 short hairpin RNA coding plasmid DNA, yielding nanoparticles. In vivo imaging analysis indicated the targeted nanoparticles could accumulate in brain more efficiently than non-targeted ones. A multiple dosing regimen by weekly intravenous administration of the nanoparticles could reduce activated casapse-3 levels, significantly improve locomotor activity and rescue dopaminergic neuronal loss and in Parkinson’s disease rats’ brain. These results indicated the rabies virus glycoprotein peptide modified brain-targeted nanoparticles were promising gene delivery system for RNA interference to achieve anti-apoptotic and anti-inflammation synergistic therapeutic effects by down-regulation the expression and activation of caspase-3.

IgE-mediated allergen gene vaccine platform targeting human antigen-presenting cells through the high-affinity IgE receptor

BACKGROUND

Treatment of IgE-mediated food allergy with standard protein-based allergen immunotherapy has proved both unsuccessful and hazardous. Allergen gene vaccination represents a promising alternative, but difficulties in gene targeting and expression in antigen-presenting cells represent a major limitation for efficient gene vaccination.

OBJECTIVE

We sought to construct a genetically engineered human epsilon-polylysine (EPL) fusion protein that binds allergen gene expression systems and targets the gene vaccine complex to antigen-presenting cells through the interaction of EPL and the high-affinity receptor for IgE for efficient allergen gene vaccination.

METHODS

Genetic engineering was used to design and produce the EPL fusion gene, consisting of the human CHepsilon2-4 linked to 55 lysine residues, and the conventional approaches were used to characterize the biologic features of EPL.

RESULTS

EPL was assembled as functional dimers and capable of binding DNA plasmids in both an EPL protein and plasmid DNA concentration-dependent manner. EPL targeted plasmid DNA to the high-affinity receptor for IgE on cell surfaces and increased the model gene uptake/expression. The EPL-DNA complexes were shown not to trigger mast cell degranulation.

CONCLUSION

EPL is able to function as a gene carrier system to target allergen gene to the high-affinity receptor for IgE-expressing cells through ligand receptor-mediated interactions.

Polyglutamine expansion mutation yields a pathological epitope linked to nucleation of protein aggregate: determinant of Huntington's disease onset

Polyglutamine (polyQ) expansion mutation causes conformational, neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases. These diseases are characterized by the aggregation of misfolded proteins, such as amyloid fibrils, which are toxic to cells. Amyloid fibrils are formed by a nucleated growth polymerization reaction. Unexpectedly, the critical nucleus of polyQ aggregation was found to be a monomer, suggesting that the rate-limiting nucleation process of polyQ aggregation involves the folding of mutated protein monomers. The monoclonal antibody 1C2 selectively recognizes expanded pathogenic and aggregate-prone glutamine repeats in polyQ diseases, including Huntington's disease (HD), as well as binding to polyleucine. We have therefore assayed the in vitro and in vivo aggregation kinetics of these monomeric proteins. We found that the repeat-length-dependent differences in aggregation lag times of variable lengths of polyQ and polyleucine tracts were consistently related to the integration of the length-dependent intensity of anti-1C2 signal on soluble monomers of these proteins. Surprisingly, the correlation between the aggregation lag times of polyQ tracts and the intensity of anti-1C2 signal on soluble monomers of huntingtin precisely reflected the repeat-length dependent age-of-onset of HD patients. These data suggest that the alterations in protein surface structure due to polyQ expansion mutation in soluble monomers of the mutated proteins act as an amyloid-precursor epitope. This, in turn, leads to nucleation, a key process in protein aggregation, thereby determining HD onset. These findings provide new insight into the gain-of-function mechanisms of polyQ diseases, in which polyQ expansion leads to nucleation rather than having toxic effects on the cells.

Identification of Secretory Granule Phosphatidylinositol 4,5-Bisphosphate-interacting Proteins Using an Affinity Pulldown Strategy

Phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) synthesis is required for calcium-dependent exocytosis in neurosecretory cells. We developed a PtdIns(4,5)P2 bead pulldown strategy combined with subcellular fractionation to identify endogenous chromaffin granule proteins that interact with PtdIns(4,5)P2. We identified two synaptotagmin isoforms, synaptotagmins 1 and 7; spectrin; alpha-adaptin; and synaptotagmin-like protein 4 (granuphilin) by mass spectrometry and Western blotting. The interaction between synaptotagmin 7 and PtdIns(4,5)P2 and its functional relevance was investigated. The 45-kDa isoform of synaptotagmin 7 was found to be highly expressed in adrenal chromaffin cells compared with PC12 cells and to mainly localize to secretory granules by subcellular fractionation, immunoisolation, and immunocytochemistry. We demonstrated that synaptotagmin 7 binds PtdIns(4,5)P2 via the C2B domain in the absence of calcium and via both the C2A and C2B domains in the presence of calcium. We mutated the polylysine stretch in synaptotagmin 7 C2B and demonstrated that this mutant domain lacks the calcium-independent PtdIns(4,5)P2 binding. Synaptotagmin 7 C2B domain inhibited catecholamine release from digitonin-permeabilized chromaffin cells, and this inhibition was abrogated with the C2B polylysine mutant. These data indicate that synaptotagmin 7 C2B-effector interactions, which occur via the polylysine stretch, including calcium-independent PtdIns(4,5)P2 binding, are important for chromaffin granule exocytosis.

Translation of the poly(A) tail plays crucial roles in nonstop mRNA surveillance via translation repression and protein destabilization by proteasome in yeast

mRNA surveillance system represses the expression of nonstop mRNA by rapid mRNA degradation and translation repression. Here we show that the level of protein product of nonstop mRNA containing a poly(A) tail was reduced 100-fold, and this reduction was due to rapid mRNA degradation, translation repression, and protein destabilization, at least in part, by the proteasome. Insertion of a poly(A) tract upstream of a termination codon resulted in translation repression and protein destabilization, but not rapid mRNA decay. We propose that translation of the poly(A) tail plays crucial roles in nonstop mRNA surveillance via translation repression and protein destabilization.

Cardiomyocyte preparation, culture, and gene transfer

Neonatal rat ventricular myocytes (NRVMs) cultured in vitro have been used as a model system for easily recreating and studying several cardiac molecular conditions, such as hypertrophy, oxygen deprivation, and gene expression. However, low efficiency of gene transfer has often represented one of the major limitations of this technique. In this chapter we describe in detail how to isolate NRVMs from neonatal rat heart and the optimal conditions for their long-term culture. Different cardiomyocyte transfection methodologies, based on viral or viral/chemical delivery carriers, are also discussed.

Cardiomyocyte preparation, culture, and gene transfer

Neonatal rat ventricular myocytes (NRVMs) cultured in vitro have been used as a model system for easily recreating and studying several cardiac molecular conditions, such as hypertrophy, oxygen deprivation, and gene expression. However, low efficiency of gene transfer has often represented one of the major limitations of this technique. In this chapter we describe in detail how to isolate NRVMs from neonatal rat heart and the optimal conditions for their long-term culture. Different cardiomyocyte transfection methodologies, based on viral or viral/chemical delivery carriers, are also discussed.

Poly (ethylenimine)-grafted-poly [(aspartic acid)-co-lysine], a potential non-viral vector for DNA delivery

A potential non-viral gene-transfer vector, poly(ethylenimine)-grafted-poly[(aspartic acid)-co-lysine] (PSL), has been developed by thermal polycondensation of aspartic acid and lysine under reduced pressure. Low-molecular-mass branch poly(ethylenimine) (PEI600) was conjugated to the backbone. The chemical structure of the resulting co-polymer was identified by 1H-NMR, FT-IR, TGA and X-ray diffraction. The results of the MTT assay showed that at concentration up to 4000 nmol/l of the vector cell viability was over 80% and showed low toxicity. Electrophoretic retardation and ethidum bromide assay showed that at N/P ratios 12-15 (w/w) the DNA could be condensed and neutralized. Using the zeta potential assay we discovered that it had a high positive charge on its surface of the particle (over 30 mV). The particle sizes of the co-polymer/DNA complexes were 150-170 nm, as measured by DLS and AFM. Compared with PEI600, co-polymer/DNA complexes showed a significant enhancement of transfection activity in the absence and presence of serum in NT2 and COS7 cell lines. This means that the PEI600-PSL co-polymer is a promising candidate for gene delivery.

A new biodegradable poly-amino acid: alpha,beta-poly[(N-hydroxypropyl/aminoethyl)-DL-aspartamide-co-L-lysine], a potential nonviral vector for gene delivery

A new class of biodegradable poly-amino acid, alpha,beta-poly[(N-hydroxypropyl/aminoethyl)-DL-Aspartamide-co-L-Lysine] (PHAAL), was synthesized by ring-opening of poly[succinimide-co-lysine](PSL) with n-propanolamine and ethylene diamine after thermal copolycondensation of DL-Aspartic acid and L-lysine under reduced pressure. Different ratio feeds of PSL were obtained and characterized by 1H-NMR, Fourier transformed infrared spectroscopy, X-ray, thermogravimetric analysis and gel permeation chromatography experiments. As one of the polycationic materials, performed for gene delivery carrier, the PHAAL degradation experiment was carried out in PBS (10 mM, pH =7.4) and enzyme (papain, trypsine 1 mg/ml, 37 +/- 0.1 degree C) solution. PHAAL had lower cytotoxicity than polyethylenimine (25KDa) and poly-L-Lysine (30 KDa), in Hela, E.C.V.-304, Bcap 37 cell lines. Particle size and zeta, potential of PHAAL/DNA complexes were measured. Sizes ranged from 300-500 nm and zeta potentials were at -20 to 2,5 mV. The condensation ability of PHAAL for DNA was evaluated by agarose gel electrophoresis. The PHAAL could completely neutralize DNA at N/P ratio (w/w) 150:1.

Copolymers of poly-L-lysine with serine and tryptophan form stable DNA vectors: implications for receptor-mediated gene transfer

Inefficient gene transfer and poor stability in physiological medium are important shortcomings for receptor-mediated gene transfer vectors. Here, we evaluate vectors formulated with random copolymers of L-lysine/L-serine (3:1) and L-lysine/L-tryptophan (4:1), focusing on both their biophysical and functional characterization. By means of dynamic light scattering (DLS) and transmission electron microscopy (TEM), we demonstrate that poly-L-lysine (pK), poly-L-lysine-L-tryptophan (pKW) and poly-L-lysine-L-serine (pKS) are able to form compacted, small particles when mixed with plasmid DNA in the absence of salt. Upon dilution in physiological medium, copolymers of both lys/ser and lys/trp do not aggregate, in contrast with poly-L-lysine DNA complexes as determined by scattering, DLS and TEM measurements. Tight packing, as demonstrated by resistance to heparin, SDS and trypsin treatments, is also featured in tryptophan-containing complexes. Successful receptor-mediated endocytosis gene transfer using galactosylated copolymers into cells expressing the asiagloglycoprotein receptor correlated with lack of aggregation. Particles obtained using galactosylated poly-L-lysine-L-tryptophan (Gal-pKW) copolymer demonstrated specific receptor-mediated gene transfer since reporter gene activity dropped in the presence of an excess ligand in the culture medium during transfection. Although copolymers of galactosylated poly-L-lysine-L-serine (Gal-pKS) do not aggregate in the presence of salt, they are not able to internalize in a specific receptor-mediated endocytosis fashion. The introduction of bulky aromatic/hydrophobic (tryptophan) or hydrophillic (serine) moieties into the positively charged vectors allows the compacted particles to disperse into salt-containing medium avoiding salt-induced aggregation. Moreover, tryptophan-containing particles are able to mediate specific gene transfer via receptor-mediated endocytosis.

Comparison of the efficiency of transduction of leukemic cells by fiber-modified adenoviruses

Efficient gene transfer with adenoviral type 5 (Ad5) vectors depends on the initial attachment of their fiber, which binds the coxsackie-adenovirus receptor (CAR), and their subsequent internalization, mediated by the interaction of viral penton base with target cell alphav integrins. We previously demonstrated that human leukemic cells lack these receptors and are therefore resistant to Ad5 transduction, limiting efforts to genetically modify these cells. Human leukemic blasts are, however, susceptible to transduction with an adenovector made CAR independent by substitution of a chimeric Ad5/35 fiber [Yotnda et al. (2001). Gene Ther. 8, 930-937]. Other receptors can also be targeted with recombinant ligand moieties incorporated into adenovirus fiber. We have determined which of these fiber-modified adenovectors is most effective at modifying human primary leukemia cells, and lines. We used a replication-incompetent Ad5-beta-gal vector, in which the Ad5 fiber was replaced with fiber from various adenovirus serotypes (Ad35 and Ad11), or modified either with variable length polylysine (K4, K7, K21) or RGD-4C peptide. All the modified fiber vectors transduced primary leukemia cells and cell lines more efficiently than Ad5. Polylysine-substituted Ad5F/K21 and peptide-modified Ad5F/RGD vectors were most effective overall (up to 100% efficiency), whereas Ad5F/RGD was the most effective at transducing B cell acute lymphoblastic leukemia cells (90% efficiency). Ad5F/K21 and Ad5F/RGD should be of value for the genetic modification of human primary leukemia cells.

A multiprong approach to cancer gene therapy by coencapsulated cells

Immune-isolation of nonautologous cells with microencapsulation protects these cells from graft rejection, thus allowing the same recombinant therapeutic cell line to be implanted in different recipients. This approach was successful in treating HER2/neu-expressing tumors in mice by delivering an interleukin-2 fusion protein (sFvIL-2), or angiostatin. However, treatment with interleukin-2 led to profuse inflammation, while angiostatin delivery did not result in long-term tumor suppression, in part due to endothelial cell-independent neovascularization (vascular mimicry). We hypothesize that coencapsulating the two producer cells in the same microcapsules may enhance the efficacy and ameliorate the above side effects. Hence, B16-F0/neu tumor-bearing mice were implanted with sFvIL-2- and angiostatin-secreting cells coencapsulated in the same alginate-poly-L-lysine-alginate microcapsules. However, this protocol only produced an incremental but not synergistic improvement, as measured with greater tumor suppression and improved survival. Compared to the single sFvIL-2 treatment, the coencapsulation protocol showed improved efficacy associated with: mobilization of sFvIL-2 from the spleen; a higher level of cytokine delivery systemically and to the tumors; increased tumor and tumor-associated endothelial cell apoptosis; and a reduced host inflammatory response. However, compared to the single angiostatin treatment, the efficacy was reduced, primarily due to a "bystander" effect in which the angiostatin-secreting cells suffered similar transgene silencing as the coencapsulated cytokine-secreting cells. Nevertheless, the level of "vascular mimicry" of the single angiostatin treatment was significantly reduced. Hence, while there was no synergy in efficacy, an incremental improvement and some reduction in undesirable side effects of inflammation and vascular mimicry were achieved over the single treatments.

Photochemical enhancement of gene delivery to glioblastoma cells is dependent on the vector applied

BACKGROUND

Photodynamic therapy (PDT) and gene therapy protocols are separately under clinical evaluation for treatment of brain malignancies. Here, the potential of a novel combination technique, photo-induced delivery of macromolecules and genes to glioblastoma cells, is evaluated.

MATERIALS AND METHODS

The photochemical effect on survival of GaMg and U-87Mg cells after incubation with the protein toxin gelonin, on transfection with a plasmid complexed to poly-L-lysine (PLL), and on transduction with adenovirus serotype 5 (Ad5) and adeno-associated virus type 5 (AAV5) vectors, were studied.

RESULTS

Cytotoxicity of gelonin and gene transfer from plasmid/PLL complexes were considerably improved by photochemical treatment in both cell lines, while the light-inducible effect on Ad5 transduction was most pronounced in U-87Mg. For the first time, photochemical enhancement of AAV transduction is shown. A 4-fold increase in percentage positive cells was detected after photochemical treatment of AAV5-infected GaMg cells. However, in contrast to Ad5, AAV5 transduction of U-87Mg remained unaffected by light treatment, independently of viral dose, light dose and timing of the light treatment relative to the transduction period.

CONCLUSION

Photochemical treatment is a versatile tool for macromolecular delivery to glioblastoma cells, however, the photochemical effect on gene transfer by viral vectors is highly dependent on the cell line and vector applied.

Biological properties of photocrosslinked alginate microcapsules

An alternative form of gene therapy using recombinant cell lines delivering therapeutic products encapsulated in alginate hydrogel has proven effective in treating many murine models. The lack of long-term capsule stability has led to a new strategy to reinforce the microcapsules with a photopolymerized interpenetrating covalent network of N-vinylpyrrolidone (NVP) and sodium acrylate. Here the properties for potential application in gene therapy are reported. In assessing potential toxicity of the unpolymerized residues, HPLC showed that even after 1 week of washing, no toxic monomers could be detected. Their ability to sustain cell growth was monitored with growth of the encapsulated cells in vitro and in vivo. Although the initial photopolymerization caused significant cell damage, the cells were able to recover normal growth rates thereafter. After implanting into mice, the NVP-modified capsules showed a high level of biocompatibility as measured by hematological and biochemical functional tests. There was also no difference in the amount and type of plasma proteins adsorbing to the NVP-modified and the classical alginate capsules, thus indicating their similar biological compatibility. Both in vitro and in vivo tests confirmed that the NVP-modified capsules were more resistant to osmotic stress than the alginate microcapsules. Furthermore, when applied to the treatment of a murine model of human cancer by delivering encapsulated cells secreting angiostatin, the NVP-modified microcapsules suppressed tumor growth as successfully as the regular alginate microcapsules. In conclusion, the covalently modified microcapsules have shown a high level of biocompatibility, safety, increase in stability, and clinical efficacy for use as immunoisolation devices in gene therapy.

Effect of Terplex/VEGF-165 gene therapy on left ventricular function and structure following myocardial infarction. VEGF gene therapy for myocardial infarction

BACKGROUND

We used a novel lipopolymeric gene delivery system, TeplexDNA, to transfect myocardium with plasmid vascular endothelial growth factor-165 (pVEGF) and evaluated the ability of pVEGF to preserve left ventricular function and structure after coronary ligation in a rabbit model.

METHODS

New Zealand white rabbits underwent circumflex coronary ligation after direct intramyocardial injection of either Terplex alone or Terplex + 50 microg pVEGF-165. Serial echocardiography and histologic studies were performed (n = 12/group). Mortality did not differ between groups. The data is reported as the mean +/- standard deviation.

RESULTS

Over the 21 days following coronary ligation, pVEGF-165-treated animals demonstrated significant improvement in fractional shortening (20-25%, p = 0.02), long axis two-dimensional ejection fraction (42-51%, p=0.02) and short axis m-mode ejection fraction (46-54%, p = 0.02). No significant improvements were noted in the control group. VEGF-treated animals had a 50% increase in peri-infarct vessel density and a trend towards a smaller infarct size (20% vs. 29%, p = 0.10). In animals receiving pVEGF-165, the diastolic ventricular area increased from 1.87 +/- 0.24 cm2 prior to ligation to 2.19 +/- 0.23 cm2 at 21 days following ligation, compared to an increase from 1.84 +/- 0.38 to 2.54 +/- 0.55 cm2 over the same period in control animals (p = 0.03). Similarly, the systolic ventricular area in VEGF-165 animals increased from 1.06 +/- 0.26 cm2 prior to ligation to 1.50 +/- 0.29 cm2 at 21 days following ligation, compared to an increase from 1.16 +/- 0.30 to 1.86 +/- 0.43 cm2 over the same period in the control animals (p = 0.04).

CONCLUSION

TerplexDNA mediated delivery of plasmid VEGF administered at the time of coronary occlusion improves left ventricular function and reduces left ventricular dilation following myocardial infarction.

Gene transfer into human hepatoma cells by receptor-associated protein/polylysine conjugates

Receptor-associated protein (RAP) is a ligand for all members of low-density lipoprotein (LDL) receptor families. RAP is internalized into cells via receptor-mediated endocytic trafficking, making it an attractive mechanism for efficient gene delivery. In this study, we have developed a gene delivery system using RAP as a targeting ligand. A RAP cDNA lacking a C-terminal heparin-binding domain was amplified by polymerase chain reaction (PCR) from a human liver cDNA library and was reamplified by using a primer containing a cysteine codon at its carboxyl end to facilitate its conjugation to polylysine (polyK). RAP was purified using a bacterial expression system and coupled to poly-D-lysine (PDL) or poly-L-lysine (PLL) of average MW 50 kDa via the heterobifunctional cross-linker SPDP. Using fluorescence-labeled RAP ligand, cellular uptake of the transfection complexes into HepG2 cells was shown to be highly efficient and more specific to PDL-conjugated RAP compared with PLL-conjugated one. Plasmid DNA containing a luciferase reporter gene was condensed with either RAP-PDL or RAP-PLL. In vitro transfection into HepG2 cells with RAP-PDL conjugate resulted in significantly higher luciferase expression levels in comparison to either nonconjugated PDL, or RAP-PLL, or LipofecAMINE/DNA complexes in the presence of 10% fetal bovine serum. Luciferase expression was inhibited by the addition of excess RAP. Treatment of the cells with Lovastatin, which inhibits HMG-Co reductase and increases expression of LDL receptor, stimulates luciferase expression, suggesting that the gene delivery is specifically mediated by LDL receptor. Thus, RAP-PDL conjugates have the potential to be used as a new nonviral gene delivery vector.

Fusion of HIV-1 Tat protein transduction domain to poly-lysine as a new DNA delivery tool

Effective gene therapy depends on the efficient transfer of therapeutic genes to target cells. None of the current technologies, however, satisfy all of the requirements necessary for gene therapy, because the plasma and nuclear membranes of mammalian cells are tight barriers against gene transfer using synthetic delivery systems. The protein transduction domain (PTD) of human immunodeficiency virus type 1 (HIV-1) Tat protein greatly facilitates protein transfer via membrane destabilisation. We synthesised polylysine peptides containing Tat PTD (TAT-pK), or other sequences, and investigated their potential as agents for gene transfer. The synthesised polypeptide TAT-pK retains DNA binding function and mediates delivery of a reporter gene to cultured cells. RGD motif binds with low affinity to alpha integrins which induce cell activation. Two control polypeptides, GGG-pK and RGD-pK, were synthesised and tested, but their gene transfer abilities were weaker than those of TAT-pK. TAT-pK-mediated gene transfer was enhanced in the presence of chloroquine or ammonium chloride, to a greater extent than that of cationic lipid-mediated gene transfer in most cancer cell lines tested. These data suggest that TAT-pK may be a potent candidate delivery vehicle that promotes gene transfer, dependent on the endocytic pathway. We conclude that the TAT-pK/DNA complex is useful as a minimal unit to package therapeutic genes and to transduce them into mammalian cells.

CTb targeted non-viral cDNA delivery enhances transgene expression in neurons

BACKGROUND

Efficient neuronal gene therapy is a goal for the long-term repair and regeneration of the injured central nervous system (CNS). We investigated whether targeting cDNA to neurons with cholera toxin b chain conjugated non-viral polyplexes led to increased efficiency of non-viral gene transfer in the CNS. Here, we illustrate the potential for this strategy by demonstrating enhanced transfection of a differentiated neuronal cell type, PC12.

METHODS

In vitro transfection efficiency of a cholera toxin b chain-poly(D-lysine) molecular conjugate (CTb-K(100)) was compared by fluorescence-activated cell sorting (FACS) analysis of green fluorescent protein (GFP) expression and luminometric measurement of beta-galactosidase (beta-gal) expression, to untargeted poly(D-lysine) (K(100)) in undifferentiated and NGF-differentiated PC12 cells.

RESULTS

Transfection of undifferentiated PC12 cells with CTb-K(100) polyplexes resulted in a 36-fold increase in levels of pCMV-DNA(LacZ) expression and a 20-fold increase in the frequency of transduction with pCMV-DNA(GFP), compared with untargeted K(100) polyplexes. Treatment of PC12 cells with 50 ng/ml/day of NGF for 14 days led to differentiation to a neuronal phenotype. Transfection of NGF-differentiated cells with CTb-K(100) polyplexes resulted in a 133-fold increase in levels of pCMV-DNA(LacZ) expression and a 11-fold increase in the percentage of cells transduced with pCMV-DNA(GFP), compared with untargeted K(100) polyplexes. Transfection was dependent on CTb, with CTb-K(100)-mediated transfections competitively inhibited with free CTb in both PC12 phenotypes.

CONCLUSIONS

Non-viral systems for gene transfer in damaged CNS show superior toxicological profiles to most viruses but are limited by inefficient and non-selective gene expression in target tissue. Cholera toxin is known to interact preferentially with neuronal cells of the central and peripheral nervous systems, mediating binding through the b subunit, CTb, and the pentasaccharide moiety of the gangliosaccharide, GM1, which is present at high levels on the neuronal cell surface. Here, we show that a molecular conjugate of the CTb subunit, covalently linked to poly(D-lysine), is able to successfully target and significantly enhance transfection of a neuronal cell type, NGF-differentiated rat PC12 pheochromocytoma cells. This observation encourages the further development of non-viral strategies for the delivery of therapeutic genes to neurons.

Preclinical evaluation of a class of infectivity-enhanced adenoviral vectors in ovarian cancer gene therapy

Ovarian carcinoma cells are often infected inefficiently by adenoviruses (Ad) due to low expression of coxsackie-adenovirus receptors (CAR), hindering the application of adenovirus-mediated gene therapy in ovarian cancer. In this study, we explored a class of infectivity-enhanced Ad vectors, which contain CAR-independent targeting motifs RGD (Ad5.RGD), polylysine (Ad5.pK7), or both (Ad5.RGD.pK7), for their utility in ovarian cancer gene therapy using in vitro and in vivo model systems. We found that these vectors infected established ovarian carcinoma cell lines and primary ovarian cancer cells with significantly enhanced infectivity. Among them, Ad5.RGD.pK7 appeared to be most efficient. Further, we evaluated their gene delivery efficiency using two different ovarian cancer mouse models--subcutaneous and intraperitoneal human ovarian cancer xenografts. All of the modified vectors appeared to be more efficient than the unmodified Ad5 vector in both models, although some of the differences are not statistically significant. Of these, Ad5.RGD.pK7 exhibited the highest efficacy in the subcutaneous tumor model, while Ad5.pK7 worked most efficiently in the intraperitoneal tumor model. These preclinical results suggest that Ad5.RGD.pK7 and Ad5.pK7 may be very useful in ovarian cancer gene therapy.

Use of ADME studies to confirm the safety of epsilon-polylysine as a preservative in food

Epsilon-polylysine is a homopolymer of L-lysine, containing approximately 30 L-lysine subunits, as synthesized in aerobic bacterial fermentation by Streptomyces albulus. epsilon -Polylysine is approved for food use in Japan as an antimicrobial preservative. A series of pharmacokinetic and metabolic profile studies on epsilon -polylysine have been conducted in rats in order to provide a better understanding of the reason for its lack of toxicological effects in subchronic and chronic feeding bioassays using relatively high concentrations in the diet up to 50000 ppm. As reported in this article, epsilon -polylysine was practically non-toxic in an acute oral toxicity study in rats, with no mortality up to 5 g/kg and was not mutagenic in bacterial reversion assays. Absorption, distribution, metabolism and excretion (ADME) studies on 14C-radiolabeled epsilon -polylysine, given in a single dose to fasted male rats at 100mg/kg, revealed low absorption from the gastrointestinal tract. All but trace amounts of the dosed radioactivity was eliminated by excretion within 168 h and over 97% was accounted for in urine (1.2%), feces (92.9%), or expired air (3%) by 48 h. The sum of the cumulative excretion with routes associated with absorption in urine, expired air and carcass was 6.4% of total recovered radioactivity; approximately 94% of the dose of epsilon -polylysine passed unabsorbed through the gastrointestinal tract in the feces. Whole body autoradiography did not show concentration of absorbed epsilon -polylysine in any tissue or organ. Excretion half-lives of epsilon -polylysine equivalents in blood and plasma were 20 and 3.9 days, likely prolonged by the incorporation into protein of cleaved L-lysine. Metabolic profiles by HPLC analysis of plasma samples suggest that L-lysine is the predominant early metabolic by-product, likely from protease activity in the upper GI tract; only 0.2% of the administered parent compound was found in plasma. At 8-72 h, HPLC profiles show diminishing levels of epsilon -polylysine and L-lysine in plasma, accompanied by a shift to larger peaks of homopolymer fragments of varying subunit length, presumably from microbial degradation of epsilon -polylysine in the lower gut. HPLC profiles of urine and feces collected from 0 to 24 h post-dosing revealed three distinct peaks in urine, the first peak likely to be epsilon -polylysine and epsilon -polylysine less a few amino acid subunits, and the second, L-lysine and the third, a metabolite of L-lysine. Radiolabeled L-lysine was reduced from 67.2% of the radioactivity in plasma at 30 min to 7.5% at 4 h, indicating that L-lysine is readily removed from plasma from essential amino acid incorporation into protein. Based on the findings of the ADME studies and lack of toxicity in safety studies, the proposed use of epsilon -polylysine as a preservative in foods is considered to be safe.

Histidine containing peptides and polypeptides as nucleic acid vectors

Nucleic acid transfer in mammalian cels is drastically improved with devices which increase their delivery in the cytosol upon endocytosis. In this chapter, we describe the effect on plasmid DNA (pDNA) and oligonucleotide (ODN) transfer, of an histidine-rich peptide (H5WYG), histidylated oligolysine (HoK), and histidylated polylysine (HpK) designed on the basis of the membrane destabilization capacity of poly-L-histidine at a pH dose to that of the endosomes. We report that H5WYG, which permeabilizes the cell membrane at pH 6.4, favors the transfection mediated by lactosylated polylysine/pDNA complexes and, by lowering the pH of extracellular medium, allows the loading of the cytosol and the cell nucleus with ODN. We show that HoK forms small cationic spherical particles of 35 nm with ODN and HpK rod or toroid cationic particles of 100 nm with pDNA. PEGylation stabilizes these particles at physiological salt concentration. We also show that (i) HoK/ODN complexes yield a more than 20-fold increase of the biological activity of antisense ODN towards the inhibition of transient as well as constitutive gene expression and (ii) HpK/pDNA complexes yield a transfection efficiency of 3-4.5 order of magnitude higher than do polylysine/pDNA complexes. We also provide evidence that the effect of these polyhistidylated molecules is mediated by imidazole protonation in endosomes. Overall our data show that polyhistidylated molecules constitute interesting devices for an efficient cytosolic delivery of nucleic acids, and that ionic complexes between histidylated polylysine and a pDNA are attractive for developing a nonviral gene delivery system.

Double modification of adenovirus fiber with RGD and polylysine motifs improves coxsackievirus-adenovirus receptor-independent gene transfer efficiency

Adenoviral vectors based on serotype 5 (Ad5) have been widely used to deliver therapeutic genes to different organs and tissues. However, many tissues are poorly infected with Ad5 because of low-level expression of its primary receptor, coxsackievirus-adenovirus receptor (CAR). Two motifs, RGD and polylysine (pK7), have been shown to enhance Ad5 infection via CAR-independent pathways when incorporated into fiber separately. Because the two motifs bind to different cell surface proteins (RGD motif binds to integrins, and pK7 binds to heparan sulfate-containing receptors), we hypothesized that the two motifs function additively to improve gene transfer efficiency. In this study, we sought to improve infectivity of Ad5 by incorporating both RGD and pK7 motifs into fiber. We created an Ad5 vector containing an RGD motif in the HI loop and a pK7 motif at the C terminus of fiber (Ad5.RGD.pK7). Compared with unmodified and singly modified Ad5 vectors Ad5.RGD and Ad5.pK7, the doubly modified Ad5 demonstrated the highest infectivity in both CAR-positive and CAR-negative cells. The enhanced infectivity appeared to be mediated by additive effects of the two motifs. More importantly, Ad5.RGD.pK7 lost the natural CAR-dependent pathway while employing novel targeting mechanisms. This strategy thus may be used to overcome CAR deficiency and to achieve vector retargeting.

In vitro gene transfection using dendritic poly(L-lysine)

Monodispersed dendritic poly(L-lysine)s (DPKs) of several generations were synthesized, and their characteristics as a gene transfection reagent were then investigated. The agarose gel shift and ethidium bromide titration assay proved that the DPKs of the third generation and higher could form a complex with a plasmid DNA, and the degree of compaction of the DNA was increased by the increasing number of the generation. The DPKs of the fifth and sixth generation, which have 64 and 128 amine groups on the surface of the molecule, respectively, showed efficient gene transfection ability into several cultivated cell lines without significant cytotoxity. In addition, the transfection efficiency of the DPK of the sixth generation was not seriously reduced even if serum was added at 50% of the final concentration into the transfection medium. Because we can strictly synthesize various DPK derivatives, which have several types of branch units, terminal cationic groups, and so on, they are expected to be a good object of study regarding the basic information on the detailed mechanism of gene transfection into cells. We also expect to be able to easily construct DPK-based functional gene carriers, e.g., DPKs modified by ligands such as a sugar chain, which can enable advanced gene delivery in vivo.

9-polylysine protein transduction domain: enhanced penetration efficiency of superoxide dismutase into mammalian cells and skin

Antioxidant enzymes, such as superoxide dismutase (SOD) and catalase (CAT), have been considered to have a beneficial effect against various diseases that are mediated by the reactive oxygen species (ROS). Although a variety of modified recombinant antioxidant enzymes have been generated to protect against oxidative stresses, the lack of their transduction ability into cells resulted in a limited ability to detoxify intracellular ROS. To render the SOD enzyme capable of detoxifying intracellular ROS when added extracellularly, cell-permeable recombinant SOD proteins were generated. A human Cu,Zn-superoxide dismutase (Cu,Zn-SOD) gene was fused with a gene fragment that encodes the 9 amino acids Tat protein transduction domain (RKKRRQRRR) of HIV-1 and lysine rich peptide (KKKKKKKKK) in a bacterial expression vector in order to produce a genetic in-frame Tat-SOD and 9Lys-SOD fusion protein, respectively. The expressed and purified Tat-SOD and 9Lys-SOD fusion proteins can transduce into human fibroblast cells, and they were enzymatically active and stable for 24 h. The cell viability of the fibroblast cells that were treated with paraquat, an intracellular superoxide anion generator, was increased by the transduced Tat-SOD or 9Lys-SOD. The transduction efficacy of 9Lys-SOD was more efficient than that of Tat-SOD. We evaluated the ability of the SOD fusion pmteins to transduce into animal skin. This analysis showed that Tat-SOD and 9Lys-SOD fusion proteins efficiently penetrated into the epidermis as well as the dermis of the subcutaneous layer, when sprayed on mice skin (judged by the immunohistochemistry and specific enzyme activities). The enzymatic activity of the transduced 9Lys-SOD was higher than that of Tat-SOD, indicating that the penetration of 9Lys-SOD was more efficient when put into the skin. These results suggest Tat-SOD and 9Lys-SOD fusion proteins can be used as anti-aging cosmetics, or in protein therapy, for various disorders that are related to this antioxidant enzyme and ROS.

HIV-1 nucleocapsid protein zinc finger structures induce tRNA(Lys,3) structural changes but are not critical for primer/template annealing

Retroviral reverse transcriptases use host cellular tRNAs as primers to initiate reverse transcription. In the case of human immunodeficiency virus type 1 (HIV-1), the 3' 18 nucleotides of human tRNA(Lys,3) are annealed to a complementary sequence on the RNA genome known as the primer binding site (PBS). The HIV-1 nucleocapsid protein (NC) facilitates this annealing. To understand the structural changes that are induced upon NC binding to the tRNA alone, we employed a chemical probing method using the lanthanide metal terbium. At low concentrations of NC, the strong terbium cleavage observed in the core region of the tRNA is significantly attenuated. Thus, NC binding first results in disruption of the tRNA's metal binding pockets, including those that stabilize the D-TPsiC tertiary interaction. When NC concentrations approach the amount needed for complete primer/template annealing, NC further destabilizes the tRNA acceptor-TPsiC stem minihelix, as evidenced by increased terbium cleavage in this domain. A mutant form of NC (SSHS NC), which lacks the zinc finger structures, is able to anneal tRNA(Lys,3) efficiently to the PBS, and to destabilize the tRNA tertiary core, albeit less effectively than wild-type NC. This mutant form of NC does not affect cleavage significantly in the helical regions, even when bound at high concentrations. These results, as well as experiments conducted in the presence of polyLys, suggest that in the absence of the zinc finger structures, NC acts as a polycation, neutralizing the highly negative phosphodiester backbone. The presence of an effective multivalent cationic peptide is sufficient for efficient tRNA primer annealing to the PBS.

Potential tumor-targeting peptide vector of histidylated oligolysine conjugated to a tumor-homing RGD motif

We have developed a potential tumor-targeting peptide vector (cRGD-hK) that is intended to be systemically and repeatedly administered to patients with advanced solid tumors. The peptide vector of 36 l-amino acid residues, CRGDCF(K[H-]KKK)6, comprises a tumor-homing RGD motif, a DNA-binding oligolysine, and histidyl residues to facilitate the delivery into the cytosol. Using cytomegalovirus-driven luciferase expression plasmids as a reporter, we tested the transfection efficiency of cRGD-hK in hepatoma and pancreatic cancer cell lines. Transfection with the cRGD-hK/plasmid complexes (molar ratio 4000:1) was inhibited by 50 nM bafilomycin A1, an inhibitor of the vacuolar ATPase endosomal proton pump, or 10 microM cycloRGDfV, an integrin alphavbeta3 antagonist, indicating that the three elements of cRGD-hK could function as expected, at least in vitro. In nude mice bearing tumors created by subcutaneous inoculation, luciferase activity in the tumor tissues 48 hours after the injection of the cRGD-hK/plasmid complexes through the tail vein (20 microg plasmids per mouse) was significantly higher than that in the lung, kidney, and spleen, but only slightly higher than that in the liver. Although the latter difference was small, we propose a potential nonviral gene therapy for advanced solid tumors through use of the tumor-targeting peptide vector.

[Inhibition of HBV gene expression by antisense oligonucleotides using galactosylated poly (L-lysine) as a hepatotropic carrier]

OBJECTIVE

To study the specific inhibition of HBV gene expression by antisense oligonucleotide (ASON) targeted by galactosylated poly (L-lysine) (Gal-PLL).

METHODS

According to the results of direct sequencing of PCR amplified products, a 16 mer phosphorthioate analogue of the antisense oligonucleotide (PS-ASON) directed against the HBV U5-like region was synthesized and then linked with one liver-targeting ligand, the Gal-PLL. Using the 2.2.15 cells compared the effect of them on the expression of HBV gene.

RESULTS

We identified that HBV DNA in the 2.2.15 cells was from HBV with surface antigen subtype ayw2 by sequencing. The fluorescent histochemistry test indicted that Gal-PLL had a selective affinity to the rat liver tissues. A 2:1 molar ratio of the Gal-PLL to DNA optimized the complex formation. In the same experimental conditions, the inhibitory effects of HBsAg and HBeAg by PS-ASON were 70% and 58%, respectively at a concentration of 10 mumol/L, while by ligand-PS-ASON were 96% and 82%, respectively, and the amount of HBV DNA in culture supernatant and cells was depressed significantly. An unrelated sequence oligonucleotide showed no effectiveness. All the oligonucleotide had no cytotoxicity.

CONCLUSION

Antisense oligonucleotides complex with the liver-targeting ligand can be targeted to cells via asialoglycoprotein receptors resulting in specific inhibition of HBV gene expression and replication.

A small, synthetic peptide for gene delivery via the serpin-enzyme complex receptor

BACKGROUND

The serpin-enzyme complex receptor (SECR) has previously been successfully targeted for gene delivery using synthetic peptide ligands covalently linked in fluid phase to commercially available polylysine preparations (approximately 10-54kDa). The objective of the present study was to improve this approach by the use of small, bifunctional, and easily standardised synthetic peptides.

METHODS

Two synthetic peptides designated polylysine antitrypsin 1 (PAT1) (K16 FNKPFVFLI) and PAT2 (K16 CSIPPEVKFNKPFVFLI) were evaluated for gene delivery to the HUH7 human hepatocyte cell line. The K16 moiety binds DNA electrostatically, while the FVFLM motif of human alpha1-antitrypsin targets the SECR.

RESULTS

Both PAT1 and PAT2 bind to and condense DNA into small particles as shown by laser scattering techniques. However, only PAT2 is effective for gene delivery, presumably on account of the greater distance between the K16 chain and the FVFLM motif. Gene delivery by PAT2/DNA complexes is chloroquine-dependent, can be blocked completely by free ligand (CSIPPEVKFNKPFVFLI), and is highly efficient (e.g. approximately five-fold more effective than lipofectamine). At physiological salt concentrations, PAT2/DNA complexes formed at 4 microg/ml DNA are approximately 350 nm in diameter and highly effective for gene transfer, but at 100 microg/ml DNA the complexes are aggregated (diameter > 4 microm) and inactive.

CONCLUSIONS

A small (33 amino acid), bifunctional, synthetic peptide represents a highly efficient and readily standardised DNA vector for the SECR. The effectiveness of this peptide depends on the distance of the K16 moiety from the targeting ligand. High salt concentrations are not required to form effective vector/DNA complexes.

Augmentation of myocardial transfection using TerplexDNA: a novel gene delivery system

Gene therapy is a potential new strategy for the treatment of cardiovascular disease. The most efficacious method of gene delivery remains a key hurdle to effective gene therapy. We present the application of a novel, nonviral gene delivery system (TerplexDNA) to augment myocardial transfection. The hearts of New Zealand white rabbits were injected with reporter genes, luciferase cDNA or beta-galactosidase cDNA, either as naked plasmid DNA or plasmid DNA complexed with stearyl-poly(L-lysine)-low density lipoprotein (TerplexDNA). Three day left heart myocardial cell lysates produced 44571 +/- 8730 RLU (RLU = total light units/mg protein) for the TerplexDNA luciferase rabbits versus 1638 +/- 567 RLU for the naked luciferase rabbits (P = 0.002). Thirty days after injection, myocardial lysates produced 677 +/- 52 RLU for the TerplexDNA luciferase hearts versus 18 +/- 3 RLU for the naked luciferase hearts (P = 0.002). Histologic analysis of the hearts transfected with beta-galactosidase showed that TerplexDNA increased the area and depth of transfection compared with the naked plasmid DNA alone. The hearts of Sprague-Dawley rats were injected in a similar fashion and analyzed at 1, 3, 5, 10, 15, 25 and 30 days after injection. The naked luciferase injected hearts showed transient elevation of luciferase activity to day 5 but fell back to baseline levels after that time-point. The TerplexDNA luciferase injected hearts had significantly elevated luciferase activity to 30 days. The Terplex gene delivery system significantly augments myocardial transfection compared with a naked plasmid DNA system alone. The advantage in transfection efficiency appears to be related to the unique properties of the TerplexDNA carrier molecule. The TerplexDNA delivery system represents a novel means to augment transfection of the myocardium.

Connexin 26 enhances the bystander effect in HSVtk/GCV gene therapy for human bladder cancer by adenovirus/PLL/DNA gene delivery

Herpes simplex thymidine kinase/ganciclovir (HSVtk/GCV) gene therapy has been used for the treatment of a variety of cancers. Its efficacy is enhanced by the bystander effect that helps overcome the delivery problems commonly observed in current gene therapy. Connexins encode proteins that produce gap junctions, which enable intercellular communication and the bystander effect. We previously demonstrated that decreased Cx 26 expression and loss of gap junctional intercellular communication were associated with human bladder cancer. To investigate the efficacy of the bystander effect in HSVtk/GCV gene therapy, the Cx 26 gene was introduced into UM-UC-3 and UM-UC-14 bladder cancer cell lines by an adenovirus poly-L-lysine conjugate using a multigenic expression plasmid that expressed both the HSVtk and Cx 26 genes. We found significantly increased cytotoxicity in HSVtk/GCV gene therapy after introduction of the HSVtk and Cx 26 genes together compared with the cytotoxicity seen after introduction of the HSVtk gene and LacZ genes in vitro and in vivo. Cytotoxicity correlated with Cx 26 expression and the induction of functional gap junctions. This study indicates that combination gene therapy with co-expression of the HSVtk and Cx 26 genes potentiates HSVtk/GCV gene therapy through the bystander effect.

Efficient gene delivery to vascular smooth muscle cells using a nontoxic, synthetic peptide vector system targeted to membrane integrins: a first step toward the gene therapy of chronic rejection

BACKGROUND

Chronic rejection is now the major cause of allograft failure. A prominent characteristic of the histopathology is extensive intimal proliferation of vascular smooth muscle cells. Targeting vascular smooth muscle cells by gene therapy techniques offers a possible avenue for arresting or reversing chronic rejection. Defining suitable non-viral DNA vectors for this application is the objective of this study.

METHODS

A 31 amino acid synthetic peptide has been evaluated as a DNA vector for primary cultures of vascular smooth muscle cells of man, rabbit, and rat. The vector comprises a 15 amino acid integrin-binding domain and a chain of 16 lysines for electrostatic binding of DNA. Three agents known to promote exit of vector/DNA complexes from endocytic vesicles were studied systematically to define optimal, non-toxic conditions for gene delivery.

RESULTS

Initial binding studies on frozen sections showed that the integrin-binding domain binds strongly to vascular smooth muscle cells in all three species, thereby establishing vascular smooth muscle cells as a potential target for this receptor-targeted DNA vector system. Primary cultures of vascular smooth muscle were therefore studied. The use of chloroquine to assist endocytic exit, which works well on immortalized cell lines, was of little value because of toxicity to the primary vascular smooth muscle cells. The addition of cationic lipids to polylysine-molossin/DNA conjugates gave excellent reporter gene expression, but required mildly toxic doses of cationic lipid, and resulted in some loss of integrin specificity of the vector system. The optimal system involved the use of the amino terminal 20 amino acids of the hemagglutinin of the influenza virus. This peptide, when added to polylysine-molossin/DNA complexes at an optimal w/w ratio of 5:1:2 (polylysine-molossin/DNA/fusogenic peptide) resulted in 25-30% transfection of vascular smooth muscle cells with good levels of gene expression and no toxicity.

CONCLUSION

This represents an effective and safe DNA vector, comprised entirely of small synthetic peptides, and therefore readily standardized for clinical and experimental application.

DNA transfection and transfected cell viability using amphipathic asymmetric dendrimers

Amphipathic asymmetric dendrimers have been investigated for use in delivery of genes into cells, with the objective of optimising transfection efficiency and maintaining cell viability. We have synthesised amphipathic asymmetric dendrimers by solid phase methods. The ability of two of these to transfect BHK cells in culture with beta-galactosidase gene was determined by X-gal staining. Cell viability was measured by the MTT assay for BHK cells, and by spectroscopy for lysis of erythrocytes. Interactions between dendrimer and DNA were investigated by agarose gel electrophoresis. BHK cells were optimally transfected at 5:1 +/- charge ratio yielding 20% cells receiving at least one copy of the plasmid. Cell viability decreased when the dendrimer to DNA ratio exceeded 5:1. Raising the pH significantly affected the electrophoretic mobility of complexes of dendrimer and DNA. We conclude that amphipathic asymmetric dendrimers enable efficient plasmid DNA uptake into BHK cells. Cell viability is maintained at high concentrations of dendrimer when complexed with DNA at a 5:1 +/- charge ratio. Efficiency of transfection and cell viability suggest the system may be suitable for gene delivery in vivo.

Supramolecular structure and nuclear targeting efficiency determine the enhancement of transfection by modified polylysines

Polylysine (pLy) has been used as a DNA carrier in nonviral gene delivery systems because it forms complexes with plasmid DNA via charge interaction, and condenses it into a compact structure. We have recently shown that cross-linking nuclear localization sequences (NLSs) to pLy can enhance transfection by conferring specific recognition by the cellular nuclear import 'receptor', the NLS-binding importin alpha/beta heterodimer. The present study examines and correlates for the first time the effect of the lysine/nucleotide (Ly/Nu) ratio on transfection, recognition by importin alpha/beta, and structure as determined using electron microscopy (EM) and atomic force microscopy (AFM), for pLy-DNA complexes with and without NLSs or mutant versions thereof. Intriguingly, we observed two distinct peaks of transfection enhancement at Ly/Nu ratios of 0.4 and 4.0, attributable to specific NLS recognition by importins and DNA compaction, respectively. The results indicate a clear correlation between the pLy-DNA structure, importin alpha/beta recognition, and gene transfer efficiency, thus underlining the importance of using pLy-DNA at the optimal Ly/Nu ratio.

Gene delivery via polyomavirus major capsid protein VP(1), isolated from recombinant Escherichia coli

In this study we attempted to investigate the feasibility of transferring exogenous DNA into the recipient host via polyomavirus major capsid protein VP(1) pseudocapsids generated from recombinant Escherichia coli, designated PyVP(1,E), both in vitro and in vivo. NIH-3T3 and FR3T3 cells were transfected with pCMV beta and pPyMT-1 plasmid DNA, respectively. In vitro DNA transfection was carried out via Pseudofect- and PyVP(1,E)-mediated methods, or by co-precipitation with calcium phosphate. Expression of beta-galactosidase and PyMT reporter genes was examined by Western-blot analysis. Parallel experiments were performed in vivo by direct injection of pCMV beta and pPyMT-1 plasmid DNA, complexed with PyVP(1,E), into the livers of Wistar rats, followed by Western-blot analysis and histochemical staining. The results obtained from in vitro transfection experiments showed that expression of the reporter genes can be detected in the recipient cells at 48 h post-transfection. PyVP(1,E) was shown to exhibit similarly efficient in vitro DNA transfection properties to Pseudofect, which was obtained from recombinant baculovirus.

Specific gene transfer mediated by galactosylated poly-L-lysine into hepatoma cells

Plasmid DNA/galactosylated poly-L-lysine(GalPLL) complex was used to transfer luciferase reporter gene in vitro into human hepatoma cells by a receptor-mediated endocytosis process. DNA was combined with galPLL via charge interaction (DNA:GalPLL:fusogenic peptide, 1:0.4:5, w/w/w) and the resulting complex was characterized by dynamic light scattering, gel retardation assay and zeta potential analyzer to determine the particle size, electrostatic charge interaction, and apparent surface charge. The complex was tested for the efficiency of gene transfer in cultured human hepatoblastoma cell line Hep G2 and fibroblast cells NIH/3T3 in vitro. The mean diameter of the complex (DNA:GalPLL=1:0.4, w/w) was 256+/-34.8 nm, and at this ratio, it was positively charged (zeta potential of this complex was 10.1 mV). Hep G2 cells, which express a galactose specific membrane lectin, were efficiently and selectively transfected with the RSV Luc/GalPLL complex in a sugar-dependent manner. NIH/3T3 cells, which do not express the galactose-specific membrane lectin, showed only a marginal level of gene expression. The transfection efficiency of GalPLL-conjugated DNA complex into Hep G2 cells was greatly enhanced in the presence of fusogenic peptide that can disrupt endosomes, where the GalPLL-DNA complex is entrapped with the fusogenic peptide. With the fusogenic peptide KALA, the luciferase activity in Hep G2 cells was ten-fold higher than that of cells transfected in the absence of the fusogenic peptide. Our gene transfer formulation may find potential application for the gene therapy of liver diseases.

Selective targeting of gene transfer to vascular endothelial cells by use of peptides isolated by phage display

BACKGROUND

Gene transfer to vascular cells is a highly inefficient and nonselective process, defined by the lack of specific cell-surface receptors for both nonviral and viral gene delivery vectors.

METHODS AND RESULTS

We used filamentous phage display to isolate a panel of peptides that have the ability to bind selectively and efficiently to quiescent human umbilical vein endothelial cells (HUVECs) with reduced or negligible binding to nonendothelial cells, including vascular smooth muscle cells and hepatocytes. By direct biopanning on HUVECs and a second approach involving preclearing steps before panning on HUVECs, we isolated and sequenced 140 individual phages and identified 59 peptides. We selected 7 candidates for further investigation by secondary screening of homogeneous phages on a panel of cell types. Using adenovirus-mediated gene transfer as a model gene delivery system, we cloned the peptide SIGYPLP and the positive control peptide KKKKKKK upstream of the S11e single-chain Fv ("adenobody") directed against the knob domain of the adenovirus to create fusion proteins. Adenovirus-mediated gene transfer via fiber-dependent infection was blocked with S11e, whereas inclusion of the KKKKKKK peptide retargeted gene transfer. The peptide SIGYPLP, however, retargeted gene delivery specifically to endothelial cells with a significantly enhanced efficiency over nontargeted adenovirus and without transduction of nontarget cells.

CONCLUSIONS

Our study demonstrates the feasibility of using small, novel peptides isolated via phage display to target gene delivery specifically and efficiently to HUVECs and highlights their use for retargeting both viral and nonviral gene transfer to vascular endothelial cells for future clinical applications.

Biodegradable polyester, poly[alpha-(4-aminobutyl)-L-glycolic acid], as a non-toxic gene carrier

PURPOSE

The aim of this study was to develop a non-toxic polymeric gene carrier. For this purpose, biodegradable cationic polymer, poly[alpha-(4-aminobutyl)-L-glycolic acid] (PAGA) was synthesized. PAGA was designed to have ester linkage because polyesters usually show biodegradability.

METHODS

Degradation of PAGA in an aqueous solution was followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). PAGA/DNA complexes were characterized by gel electrophoresis, atomic force microscopy (AFM), dynamic light scattering (DLS). The transfection was measured by using the beta-galactosidase reporter gene.

RESULTS

PAGA was degraded in aqueous solution very quickly and the final degradation product was a monomer (L-oxylysine). Formation of self-assembling biodegradable complexes between PAGA and DNA at a charge ratio 1:1 (+/-) was confirmed by gel band shift assay and AFM. In these studies, controlled release of DNA from the complexes could be seen. The complexes showed about 2-fold higher transfection efficiency than DNA complexes of poly-L-lysine (PLL), a structural analogue of PAGA, which is the most commonly used poly-cation for gene delivery. The polymer did not show cytotoxicity, possibly because of its degradability and the biocompatibility of the monomer.

CONCLUSIONS

The use of the biodegradable poly-cation, PAGA, as a DNA condensing agent will be useful in safe gene delivery.

Photochemical transfection: a new technology for light-induced, site-directed gene delivery

The development of methods for specific delivery of therapeutic genes into target tissues is an important issue for the further progress of in vivo gene therapy. In this article we report on a novel technology, named photochemical transfection, to use light to direct a precise delivery of therapeutic genes to a desired location. The technology makes use of photosensitizing compounds that localize mainly in the membranes of endosomes and lysosomes. On illumination these membrane structures will be destroyed, releasing endocytosed DNA into the cell cytosol. Using a green fluorescent protein gene as a model we show that illumination of photosensitizer-treated cells induces a substantial increase in the efficiency of transfection by DNA-poly-L-lysine complexes. Thus, in a human melanoma cell line the light treatment can increase the transfection efficiency more than 20-fold, reaching transfection levels of about 50% of the surviving cells. In this article various parameters of importance for the use of this technology are examined, and the potential use of the technology in gene therapy is discussed.

Glomerular filtration is required for transfection of proximal tubular cells in the rat kidney following injection of DNA complexes into the renal artery

Gene transfer to the kidney can be achieved with various DNA vectors, resulting in transgene expression in glomerular or tubular districts. Controlling transgene destination is desirable for targeting defined renal cells for specific therapeutic purposes. We previously showed that injection of polyplexes into the rat renal artery resulted in transfection of proximal tubular cells. To investigate whether this process involves glomerular filtration of the DNA-containing particles, fluorescent polyethylenimine polyplexes were prepared, containing fluoresceinated poly-L-lysine. This allowed visualization of the route of the particles into the kidney. Our polyplexes were filtered through the glomerulus, since fluorescent proximal tubuli were observed. Conversely, fluorescent lipopolyplexes containing the cationic lipid DOTAP were never observed in tubular cells. Size measurements by laser light scattering showed that the mean diameter of polyplexes (93 nm) was smaller than that of lipopolyplexes (160 nm). The size of the transfecting particles is therefore a key parameter in this process, as expected by the constraints imposed by the glomerular filtration barrier. This information is relevant, in view of modulating the physico-chemical properties of DNA complexes for optimal transgene expression in tubular cells. Gene Therapy (2000) 7, 279-285.

Metabolic stability of glutaraldehyde cross-linked peptide DNA condensates

The stability of peptide DNA condensates was examined after introducing glutaraldehyde to cross-link surface amine groups. A 20 amino acid peptide (CWK(18)) was used to condense DNA into small (70 nm) condensates. The reaction between glutaraldehyde and peptide DNA condensates was indirectly monitored using a fluorescence-based assay to establish reaction completion in 4-5 h when using glutaraldehyde-to-peptide ratios of 1 to 4 mol equiv. Higher levels of glutaraldehyde cross-linking led to significant increases in particle size. The improved stability imparted by glutaraldehyde cross-linking was demonstrated by the increased resistance of DNA condensates to shear stress induced fragmentation. The cross-linked condensates were also significantly more resistant to in vitro metabolism by serum endonucleases. A decrease in the magnitude of transient gene expression was determined for cross-linked DNA condensates which also resulted in a 10-day steady-state expression when cross-linking with 4 mol equiv of glutaraldehyde. The results suggest that cross-linking DNA condensates may provide a means to alter the time course of transient gene expression by inhibiting DNA metabolism.

Secretion of lysine in a broth medium by lactic bacteria and yeasts associated with garri production using a synthetic gene

Although cassava is an important food in the tropics, it has two major deficiencies which are carried over into those foods made from it: its content of toxic cyanogenic glucosides and its low content of protein and amino acids. Garri, a fermented cassava food, has previously been ameliorated using organisms which simultaneously secrete linamarase (to reduce the residual cyanide in the food), amylase (to contribute to the growth of fermenting organisms and increase the flavour) and lysine (to improve the amino-acid content of the food). Some of the organisms fermenting cassava for garri production produce appreciable quantities of linamarase and amylase, but they are low in lysine production. It was therefore decided to improve these organisms by transforming them with a synthetic lysine gene coding for an 8-lysine peptide cloned in pBluescript II SK phagemid vector under the control of lac promoter. The synthetic lysine polypeptide gene was successfully introduced into Escherichia coli DH5 alpha and several strains of Lactobacillus spp. and Saccharomyces spp. There was a dramatic increase in lysine secretion in the organisms, ranging from about 2.5 to sixfold, following transformation with the synthetic gene.

Efficient gene transfer by histidylated polylysine/pDNA complexes

Plasmid/polylysine complexes, which are used to transfect mammalian cells, increase the uptake of DNA, but plasmid molecules are sequestered into vesicles where they cannot escape to reach the nuclear machinery. However, the transfection efficiency increases when membrane-disrupting reagents such as chloroquine or fusogenic peptides, are used to disrupt endosomal membranes and to favor the delivery of plasmid into the cytosol. We designed a cationic polymer that forms complexes with a plasmid DNA (pDNA) and mediates the transfection of various cell lines in the absence of chloroquine or fusogenic peptides. This polymer is a polylysine (average degree of polymerization of 190) partially substituted with histidyl residues which become cationic upon protonation of the imidazole groups at pH below 6.0. The transfection efficiency was optimal with a polylysine having 38 +/- 5% of the epsilon-amino groups substituted with histidyl residues; it was not significantly impaired in the presence of serum in the culture medium. The transfection was drastically inhibited in the presence of bafilomycin A1, indicating that the protonation of the imidazole groups in the endosome lumen might favor the delivery of pDNA into the cytosol.

Lactose-poly(ethylene glycol)-grafted poly-L-lysine as hepatoma cell-tapgeted gene carrier

To investigate the delivery of DNA into cells, lactose-poly(ethylene glycol)-grafted poly-L-lysine (Lac-PEG-PLL) polymers were synthesized as polymeric gene carriers. The new synthetic carriers, varying the substitution ratio of lactose-poly(ethylene glycol) (lactose-PEG), were characterized by NMR spectroscopy and size-exclusion chromatography. Electrophoretic mobility assay confirmed that the new gene carrier makes a complex with plasmid DNA. The attached poly(ethylene glycol) gives better solubility properties to gene/carrier complex. Transfection experiments showed that Lac-PEG-PLL efficiently delivers DNA to a hepatoma cell line in vitro; the best efficiency was achieved at a 1:3 weight ratio of DNA to carrier. As the lactose-PEG substitution content increased up to 30%, the transfection efficiency increased, which demonstrates that the lactose serves as a targeting moiety. No considerable cytotoxicity was observed due to Lac-PEG-PLL or its complex with DNA within the concentration range for this experiment. The use of chloroquine increased transfection efficiency that indicates the involvement of hydrolytic degradation of the system in lysosome. It is likely that plasmid DNA/Lac-PEG-PLL complexes enter the cells through a receptor-mediated endocytosis mechanism. These results show that Lac-PEG-PLL can form a complex with plasmid DNA and serve as an efficient gene delivery carrier with lower cytotoxicity compared to that of poly-L-lysine. Therefore, it is expected that our Lac-PEG-PLL carrier can be used as an in vivo gene delivery vector.

Novel vectors for gene delivery formed by self-assembly of DNA with poly(L-lysine) grafted with hydrophilic polymers

Complexes formed between DNA and cationic polymers are attracting increasing attention as novel synthetic vectors for delivery of genes. We are trying to improve biological properties of such complexes by oriented self-assembly of DNA with cationic-hydrophilic block copolymers, designed to enshroud the complex within a protective hydrophilic polymer corona. Poly(L-lysine) (pLL) grafted with range of hydrophilic polymer blocks, including poly(ethylene glycol) (pEG), dextran and poly[N-(2-hydroxypropyl)methacrylamide] (pHPMA), shows efficient binding to DNA and mediates particle self-assembly and inhibition of ethidium bromide/DNA fluorescence. The complexes formed are discrete and typically about 100 nm diameter, viewed by atomic force microscopy. Surface charges are slightly shielded by the presence of the hydrophilic polymer, and complexes generally show decreased cytotoxicity compared with simple pLL/DNA complexes. pEG-containing complexes show increased transfection activity against cells in vitro. Complexes formed with all polymer conjugates showed greater aqueous solubility than simple pLL/DNA complexes, particularly at charge neutrality. These materials appear to have the ability to regulate the physicochemical and biological properties of polycation/DNA complexes, and should find important applications in packaging of nucleic acids for specific biological applications.

Chloroquine and amphipathic peptide helices show synergistic transfection in vitro

A pH-responsive peptide fragment modelled on the influenza virus haemagglutinin (INF7-SGSC) can promote the transfectional activity of poly(L)-lysine (pLL)/DNA complexes against 293 cells. Chloroquine also promotes transfection, but the combination of INF7-SGSC and chloroquine gives an increased, synergistic, transfectional activity. This was unexpected since the supposed modes of action of these two agents are expected to be incompatible. Microinjection of pLL/DNA complexes into the cytoplasm of Xenopus oocytes produced greater gene expression than microinjection of free DNA, possibly reflecting nuclear-homing or protection from degradation by cytoplasmic nucleases. However, pretreatment of complexes with INF7-SGSC (but not chloroquine) before cytoplasmic microinjection promoted gene expression still further. When pLL/DNA complexes were injected directly into the nucleus, INF7-SGSC again increased gene expression. The mechanism of post-endosomal action of INF7-SGSC is unknown, but could reflect its polyanionic nature, possibly enhancing intranuclear dissociation of the complexes. Whatever the mechanism, it appears that INF7-SGSC mediates two effects-one probably endosomal and the second post-endosomal, the latter showing a synergistic transfection interaction with chloroquine.

Gene transfer into hepatoma cell lines via the serpin enzyme complex receptor

The serpin enzyme complex receptor (SECR) expressed on hepatocytes binds to a conserved sequence in alpha 1-antitrypain (alpha 1-AT) and other serpins. A molecular conjugate consisting of a synthetic peptide (C1315) based on the SECR binding motif of human alpha 1-AT covalently coupled to poly-L-lysine was used to introduce reporter genes into hepatoma cell lines in culture. This conjugate condensed DNA into spheroidal particles 18-25 nm in diameter. When transfected with the SECR-directed complex containing pGL3, Hep G2 cells that express the receptor, but not Hep G2 cells that do not, expressed a peak luciferase activity of 538,731 +/- 144,346 integrated light units/mg protein 4 days after transfection. Free peptide inhibited uptake and expression in a dose-dependent manner. Complexes of DNA condensed with polylysine or LC-sulfo-N-succinimidyl-3-(2-pyridyldithio)propionate-substituted polylysine were ineffective. Transfection with a plasmid encoding human factor IX produced expression in Hep G2 (high) and HuH7 cells that express SECR but not Hep G2 (low) cells that lack the receptor. Fluorescein-labeled C1315 peptide labeled 9-31% of Hep G2 (high), 10-14% of HuH7, and 0.6-3.4% of Hep G2 (low) cells, and when the lac Z gene was transfected, only these cells expressed beta-galactosidase. SECR-mediated gene transfer gives efficient, specific uptake and high-level expression of three reporter genes, and the system merits further study for gene therapy.

Gene delivery into malignant cells in vivo by a conjugated adenovirus/DNA complex

Current viral delivery systems suffer from disadvantages that may limit the rate at which therapeutic gene expressing constructs can be tested both in vitro and in vivo. In this study, our focus was to develop a simple gene delivery system for the rapid and reproducible testing of therapeutic genes in cancer cells both in vitro and in vivo. We report here that a delivery system based on using a conjugated adenovirus in complex from with a DNA plasmid can be used for not only delivering genes in vitro but also for efficient and reproducible delivery in vivo. Replication defective adenoviral particles were chemically modified by covalent attachment of poly-L-lysine (PLL) to the viral capsid, allowing for direct interaction with DNA. The adenovirus/PLL conjugate (Adv/PLL) was used to deliver the plasmid pCMV/beta-gal to several different cancer cell lines (i.e., lung, cervical) in vitro and resulted in transduction efficiencies as high as 52% as determined by histochemical staining. On direct intralesional injection of the Adv/PLL/DNA complex into subcutaneous tumors, transduction efficiencies greater than 35% could also be achieved. As a result, this system provides a simple method for delivering and testing therapeutic genes in cells both in vitro and in vivo, prior to the further development of gene therapy vectors for both malignant and benign disease.