Lentiviral vectors for the delivery of DNA into mammalian cells

Vectors derived from oncoretroviruses, represented by the prototype Moloney murine leukemia virus (MMLV), are powerful tools for gene transfer into mammalian cells. Vectors derived from such viruses are able to carry an insert of up to 6.5 kb. Because Retroviridae and derived vectors insert their genome into the host chromosome, the transgene delivered by these viruses are stably expressed in the infected cells. From a safety standpoint, the vectors are designed to eliminate any need to carry viral genes or associated toxicities into the host cell. This also substantially reduces their potential immunogenicity. Finally, the titers achieved with these vectors can be very high, yielding efficient infection in a broad range of cell types.

Delivery of DNA to lung airway epithelium

Delivering exogenous DNA or genes directly to the lung airways offers a unique and appealing opportunity for specifically targeting gene expression to airway and alveolar epithelium. A large body of literature and experience supports the feasibility of this approach. However, airway-directed gene delivery is not as simple as was originally anticipated. The lung has evolved both physical and immunologic barriers that can hinder effective transduction of epithelial cells (1-3). Much current work in lung gene therapy is directed toward overcoming the inflammatory and immune responses provoked by gene-transfer vectors while simultaneously maximizing vector delivery and subsequent gene expression.

Gene delivery to cells in culture using retroviruses

Moloney leukemia virus-based vectors can be generated in cells that express the products of three retroviral genes, gag, pol, and env. There are a number of cell lines such as PG13 and FLYA13 (2), known as packaging cells, that have been established that stably express these genes. When these cells are transfected with vector DNA, they will generate retroviral transducing particles in the supernatant of the cells. The transducing particles can be produced by transient transfection of the packaging cells or from cells that have stably integrated the vector DNA into the packaging cell line. This is particularly useful if the vector will be required in large amounts for an extended period of time. The titer that can be achieved from transient transfection of DNA will be proportional to the transfection efficiency. In this respect, cells derived from the human embryonic kidney cell line 293 (3) are particularly useful because they can be transfected very efficiently (typically 90-99%) (4-7). Here I outline a method to generate vector transiently. Methods to generate stable packaging cell lines can be found elsewhere (8).

Delivery of adenoviral DNA to mouse liver

The liver represents a major target organ for gene delivery owing to its high biosynthetic capacity and access to the bloodstream. Adenoviral vectors are highly efficient gene-transfer vehicles, making them among the most promising systems for in vivo gene transfer to the liver. Following intravenous administration of adenoviral vectors to a variety of mammalian models, including mice, dogs, and monkeys, hepatocytes are efficiently transduced. Several delivery methods to the liver have been described, including portal vein (2-4), hepatic artery (3,5), and peripheral vein infusions (6). This chapter describes the simple, nonsurgical method of intravenous (iv) administration of adenoviral vectors in mice, and an immunohistochemical method to qualitatively evaluate liver transduction efficiency following delivery of an adenoviral vector encoding a bgalactosidase (beta-gal) marker gene. Additionally, several alternative methods to verify efficient liver transduction are introduced.

Delivery of DNA to tumor cells in vivo using adeno-associated virus

The number of published studies on transduction of tumor cells in vivo using recombinant adeno-associated virus (rAAV) vectors is very limited compared with those that have been published on targeting normal cells. A major reason for this can be attributed to the biology of the vector itself. AAV, being a nonpathogenic vector capable of providing transgene integration and long-term expression, is ideally suited for the correction of metabolic defects either to replace a defective protein/enzyme or to elevate their otherwise suboptimal levels in the system. However, increased understanding of both the biology of tumor progression and potential utility of AAV-based vectors suggests that this vector can also be wisely used for cancer gene therapy.

Delivery of DNA to pulmonary endothelium using adenoviral vectors

Delivery of genes to the pulmonary vascular endothelium is a rational approach for the investigation and potential therapy of pulmonary vascular diseases. Furthermore, in view of the exposure of this vascular bed to the entire cardiac output, this technique could be used as an efficient basis to achieve systemic delivery of secreted factors. The attraction of direct gene delivery to endothelium for the therapy of vascular disease has been especially heightened in the last couple of years in view of the new discoveries concerning the genetic basis of primary pulmonary hypertension (PPH). In brief, mutations in the bone morphogenetic protein receptor type 2 (BMPR2, a member of the transforming growth factor-beta [TGF-beta] family of receptors) gene have been found in many patients with familial PPH. Subsequent in vitro studies have confirmed an association between BMPR2 mutations and abnormal proliferative responses in pulmonary endothelial and smooth-muscle cells (2). Other TGF-beta signaling pathways may also be involved in this process, and the mechanisms involved may also have relevance for the more common cases of pulmonary vascular disease secondarily associated with chronic airways obstruction, connective tissue diseases, and perhaps HIV infection. Additionally, new evidence is emerging concerning the role of the vasculature in the pathogenesis of emphysema.

Activity of chlormethiazole at human recombinant GABA(A) and NMDA receptors

1. Investigation into the modulatory effects of chlormethiazole at human recombinant gamma-aminobutyric acid A receptor (GABAA) and N-methyl-d-aspartate (NMDA) receptors was undertaken to gain insight into its mechanism of action and determine if the drug exhibited any subtype-selective activity. 2. Despite a structural similarity to the beta-subunit-selective compound loreclezole, chlormethiazole did not show any difference in maximum efficacy and only a slight difference in EC50 in its potentiating action at alpha1beta1gamma2 and alpha1beta2gamma2 GABAA receptor subtypes with preference for alpha1beta1gamma2. 3. Similar to the previously reported subtype-dependent activity of pentobarbital, chlormethiazole elicited a significantly greater degree of maximum potentiation on receptors lacking a gamma2 subunit, and also those receptors containing an alpha4 or alpha6 subunit. This also demonstrates that chlormethiazole does not act via the benzodiazepine binding site. 4. Unlike pentobarbital and propofol, chlormethiazole elicited only a slight direct GABAA receptor activation at concentrations up to 1 mm. In addition, the drug did not potentiate anaesthetic-mediated currents elicited by pentobarbital or propofol, suggesting that chlormethiazole may be acting via an anaesthetic binding site. 5. Chlormethiazole produced weak nonselective inhibition of human NMDA NR1a+NR2A and NR1a+NR2B receptors. IC50's were approximately 500 microm that likely exceed the therapeutic dose range for chlormethiazole, indicating that the primary mechanism of the compounds in vivo activity is via GABAA receptors.

The role of organ vascularization and lipoplex-serum initial contact in intravenous murine lipofection

Following intravenous administration of cationic lipid-DNA complexes (lipoplexes) into mice, transfection (lipofection) occurs predominantly in the lungs. This was attributed to high entrapment of lipoplexes in the extended lung vascular tree. To determine whether lipofection in other organs could be enhanced by increasing the degree of vascularization, we used a transgenic mouse model with tissue-specific angiogenesis in liver. Tail vein injection of N-(1-(2,3-dioleoyloxy)propyl)-N,N,N-trimethylammonium chloride (DOTAP)/cholesterol lipoplexes resulted in increased lipoplex entrapment in hypervascularized liver but did not boost luciferase expression, suggesting that lipoplex delivery is not a sufficient condition for efficient organ lipofection. Because the intravenously injected lipoplexes migrated within seconds to lungs, we checked whether the effects of immediate contact with serum correlate with lung lipofection efficiency of different DOTAP-based formulations. Under conditions mimicking the injection environment, the lipoplex-serum interaction was strongly dependent on helper lipid and ionic strength: lipoplexes prepared in 150 mM NaCl or lipoplexes with high (>33 mol%) cholesterol were found to aggregate immediately. This aggregation process was irreversible and was inversely correlated with the percentage of lung cells that took up lipoplexes and with the efficiency of lipofection. No other structural changes in serum were observed for cholesterol-based lipoplexes. Dioleoyl phosphatidylethanolamine-based lipoplexes were found to give low expression, apparently because of an immediate loss of integrity in serum, without lipid-DNA dissociation. Our study suggests that efficient in vivo lipofection is the result of cross-talk between lipoplex composition, interaction with serum, hemodynamics, and target tissue "susceptibility" to transfection.

Effect of serine residue on the effectiveness of cationic polypeptide-based gene delivery

Poly-L-lysine(pL) was chemically modified based on two essential features which we recently reported and subjected to the gene-transfer experiment in vitro. Introduction of 25 mol% serine residue to pL slightly enhanced the gene expression level, while trimethylation of epsilon-ammonium groups of lysine did not. Only when pL was modified in both way, giving N2-trimethyl poly(lysine-co-serine), markedly enhanced gene expression was observed. The cellular uptake and localization of DNA in the cells were similar for each cationic polypeptide. DNA forming complex with the polypeptides containing serine residue was found to be well transcribed in in vitro transcription/translation system, suggesting the hydrophilic nature may allow polypeptide/DNA complexes to be recognized by the transcriptional factors and lead the subsequent effective gene expression.

Sustained expression in mammalian cells with DNA complexed with chitosan nanoparticles

This work investigates the preparation and in vitro efficiency of chitosan gene transfection systems. Chitosan was used to prepare nanoparticles with a size range of 40-200 nm as determined using photon correlation spectroscopy (PCS) and 40-80 nm as determined using transmission electron microscopy (TEM). The ability of particles to complex DNA was investigated using gel retardation. Plasmid DNA pGL3-Control encoding firefly luciferase and pCH110 encoding beta-galactosidase were used as reporter genes. For transfection 293 human embryonal kidney cells and Chinese hamster ovary (CHO-K1) cells were used. The expression of luciferase was assayed and expressed as relative light units per milligram of protein (RLU/mg protein). Results showed that these chitosan particles have potential as vectors for the transfer of DNA into mammalian cells. Cellular transfection by the chitosan-pGL3-Control particles showed a sustained expression of the luciferase gene for about 10 days. Commercial transfection reagents, SuperFect and Lipofectin were also used. In contrast to chitosan particles, the duration of expression for both SuperFect and Lipofectin was only about 2 days. Agarose gel electrophoresis and displacement experiments using polyaspartic acid indicated a probable multiple interaction between DNA and chitosan whilst the interaction between DNA and the polyamidoamine dendrimer appears to be only ionic interaction. No toxic effect on the mammalian cells was seen with chitosan. SuperFect and Lipofectin however, were observed to engender marked cytotoxicity. Poly-D,L-lactide (PLA) nanoparticles (40-80 nm) and poly-L-lactide (PLLA) lamellae (2-6 microm) were also used to load DNA by an adsorption procedure, but these failed to give good expression data.

Contribution of Poly(Amino Acids) to Advances in Pharmaceutical Biotechnology

Recently, protein biotechnology generates tremendous impacts in therapeutic products. These products include enzymes, antibodies, hormones, blood factors, growth factors and regulatory factors. Protein, vaccine and gene therapy drugs could be formulated with suitable biomaterials to deliver active agents to their target sites at the right time and maintain therapeutic effects for proper durations. In this review article, we focus on poly(amino acids) or polymerized amino acids for their applications in drug delivery systems, vaccines, and gene therapy. The nomenclatures of poly(amino acids) are briefly introduced to systematically express synthetic polypeptides. In drug delivery systems, we introduce two applications of poly(amino acids) in pharmaceutical biotechnology, either as carriers to facilitate drug delivery, or as biomaterials to be formulated as suitable delivery systems for application in tissue engineering. Many short polypeptides are mapped from antigen motifs and used for vaccination. These poly(amino acids) provide protective effects in animal challenge tests and potential application in vaccine development to be briefly introduced. Finally, some reports related to new developed poly(amino acids) as DNA carriers for achieving gene delivery are also described in the text.

Instruction of naive CD4+ T cells by polarized CD4+ T cells within dendritic cell clusters

Cooperation between CD4(+) T cells can enhance the response and modulate the cytokine profile, and defining these parameters has become a major issue for multivalent-vaccine strategies. We explored cooperation using adoptive transfer of two populations of TCR transgenic T cells of different specificity. One was transferred without prior activation, whereas the second was activated for five days by antigen stimulation under polarizing culture conditions. Both populations were transferred into a single adoptive host and then primed by particle-mediated DNA delivery. Polarized Th1 cells (inducers) raised the frequency of IFN-gamma(+) cells within a naive (target) population, whereas Th2 inducers raised the frequency of IL-4(+) and reduced that of IL-2(+) cells. These effects were obtained when the genes for both antigens were on the same particle, favoring presentation by the same dendritic cell, but not when on different particles delivered to different dendritic cells. Autonomy of DC clusters allows linked sets of antigens (e.g. from a single pathogen) to maintain cytokine bias, but allows other independent responses, each with their own set of autonomous clusters.

Genetic heterogeneity in response to adenovirus gene therapy

BACKGROUND

After intravenous delivery of the adenoviral vector into rats or mice, 95-99% of the encoded protein is produced in the hepatocytes. We observed, as have others, that the early expression levels of the vector encoded protein vary, greatly, within a species, from one animal strain to another. This study was initiated to determine the molecular mechanism causing the difference: hepatic transfection, transcription or translation. For this purpose different doses of Ad5 luciferase and Ad5 LacZ were intravenously injected into Brown Norway rats and Wag/Rij rats, two strains that differ by a factor of 10 in encoded protein levels. The proportion of LacZ positive hepatocytes, the adenoviral DNA, specific transgenic RNA and luciferase protein were compared in the two strains.

RESULTS

The number of transduced hepatocytes and the amounts of Ad5 DNA in the livers was similar in both strains, whereas the Brown Norway rats produced 8 to 10 times more of both vector encoded proteins and of transgene mRNA than the Wag/Rij rats.

CONCLUSIONS

It is concluded that the difference between strains in vector encoded protein expression is due to different transcriptional events. No evidence was obtained to suggest that the differences are related to liver damage influenced by vector toxicity or immune reactions.

Combination of IL-12 and IL-18 of electro-gene therapy synergistically inhibits tumor growth

BACKGROUND

We previously showed that IL-12 electro-gene therapy (EGT) induces significant antitumor immunity. However, because interleukin (IL)-18 acts synergistically with IL-12 to augment Th1 responses and interferon (IFN)-gamma, we designed an EGT protocol using IL-12 + IL-18 with the aim of enhancing the antitumor effects obtained with IL-12 alone.

MATERIALS AND METHODS

Expression plasmids harboring the gene for IL-12 or IL-18 were cotransferred to subcutaneous murine CT26 tumors. Subsequent expression of IFN-gamma and the presence of CD8+ T cells within treated tumors were analyzed by semiquantitative RT-PCR.

RESULTS

IL-12 + IL-18 EGT inhibited tumor growth significantly better than IL-12 EGT, which was consistent with significantly higher intratumoral levels of IFN-gamma. Enhanced infiltration of tumor tissues by CD8+ T cells was confirmed with both IL-12 and IL-12 + IL-18 EGT. Finally, IL-12 + IL-18 EGT, but not IL-12 EGT, significantly suppressed untreated contralateral tumors.

CONCLUSION

EGT with IL-12 and IL-18 is potentially an effective antitumor gene therapy.

Engineering crops, a deserving venture

Plant transformation has had a deep impact on several aspects of basic and applied research. Genetic transformation has offered new opportunities compared to traditional breeding practises since it allows the integration into a host genome of specific sequences leading to a strong reduction of the casualness of gene transfer. One of the first target areas was plant protection against pests, pathogens and environmental stresses while the recent plant engineering programs are aimed at increasing food quality, in particular at increasing nutritional characteristics of food crops. Moreover, transgenic plants, tissue or cell cultures represent an attractive biological system for producing heterologous proteins since they offer economic and qualitative benefits. High yield production can be obtained and large-scale commercial production will take advantage of the existing infrastructure for crop cultivation, processing and storage. There are also qualitative benefits since protein synthesis secretion and post-translational modifications are similar in plants and animal cells. There are no human viral pathogens harboured by plants: thus, especially for pharmaceuticals, plants represent the safer production system. Plant transformation has become an essential instrument also for basic research, in particular for the functional characterisation of genes identified by sequencing of whole genomes. Large collections of insertion mutants have been obtained in the model plant Arabidopsis to provide a high level of genome saturation that means 95% chance of inactivating any gene at least once. To instil greater public confidence in modern plant biotechnology recent advances have already been made to overcome the potential risks for human health and environment.

[Preliminary study on hens immunized with recombinant human testis prostaglandin D synthase DNA]

OBJECTIVES

In order to identify whether the hens immunized with recombinant human testis prostaglandin D synthase (rhtL-PGDS) DNA can produce anti-L-PGDS antibody.

METHODS

The serum were got from the hens immunized with recombinant plasmid pGEX-2T/htL-PGDS DNA (100 micrograms) every 2 weeks for 2 times. The exist of anti-L-PGDS antibody and its titer were tested with agarose dual immunodiffusion and ELISA with rhtL-PGDS as antigen.

RESULTS

The serum anti-L-PGDS antibody in hen immunized with pGEX-2T/htL-PGDS DNA were confirmed and its titer tested by ELISA was 1:2,048.

CONCLUSIONS

It is feasible to produce anti-L-PGDS antibody by immunizing hens with recombinant pGEX-2T/htL-PGES DNA.

Nonviral and viral gene transfer into different subsets of human dendritic cells yield comparable efficiency of transfection

Among the many promising cancer immunotherapeutic strategies, dendritic cells (DC) have become of particular interest. This study aims to optimize a clinical grade protocol for culture and transfection of human DC. Monocytes and CD34(+) hematopoietic stem cells (HSC) from same donor were differentiated under serum-free conditions and analyzed for their susceptibility to several recently described nonviral transfection methods as compared with established virally mediated gene transfer. Nonviral gene transfer methods studied were square-wave electroporation, lipofection, and particle-mediated transfer of plasmid DNA or in vitro transcribed mRNA. We conclude that DNA is not suitable for transduction of DC using nonviral methods. In contrast, mRNA and square-wave electroporation reproducibly yields 60% and 50% transfected monocyte- and CD34(+)-derived DC, respectively, measured at protein level, without affecting the cell viability. Thus, the transfection efficiency of this method is comparable with the 40-90% transgene expression obtained using retroviral (RV) or adenoviral (AdV) vectors in CD34(+)- and monocyte-derived DC, respectively. In monocyte-derived DC, however, the amount of protein expressed per-cell basis was higher after AdV (MOI = 1000) compared with mRNA electroporation-mediated transfer. This is the first study directly demonstrating side-by-side that mRNA electroporation into DC of different origin indeed results in a comparable number of transduced cells as when using virus-mediated gene transfer.

Possible mechanism of gene transfer into early to mid-gestational mouse fetuses by tail vein injection

Our aim is to develop a simple gene transfer method into egg cylinder and mid-gestational murine embryos. We examined whether plasmid/lipid complexes injected into the tail veins of pregnant transgenic mice can be transferred to fetuses at E 4.5-13.5. When pregnant CETZ-17 mice carrying a transgene consisting of a ubiquitous promoter, floxed EGFP/CAT and the LacZ gene, were injected with a Cre expression vector DNA/lipid complex, Cre-mediated excision of the transgenes, as evaluated by X-gal staining, occurred in 10-50% of fetuses treated at E 11.5-13.5. Although younger embryos remained unstained, PCR analysis revealed low levels of the Cre vector DNA and recombined transgene. To examine the fate of a solution given intravenously, we injected trypan blue or fluorescence-labeled plasmid DNA/lipid complexes into females at E 5.5-11.5 and E 6.5, respectively. Both collected in the visceral endoderm (VE) lineage, but were undetectable in the embryo proper. These findings suggest that substances in maternal blood are delivered to post-implantation embryos via cells of the VE lineage and placenta, but that most are trapped in the VE. If significantly improved, gene transfer to fetuses by injection into the maternal circulation may become a promising tool in fetal gene therapy and embryological studies.

A nonionic amphiphile agent promotes gene delivery in vivo to skeletal and cardiac muscles

Direct injection of naked DNA into skeletal or cardiac muscle induces detectable gene expression. Although this provides a practical system for transgene expression, the reported efficacy is too low to confer a therapeutic benefit. By following a rational strategy based on the supramolecular structures adopted by active complexes, we have discovered a novel nonionic amphiphile synthetic agent [poly(ethyleneoxide)(13)-poly(propyleneoxide)(30)-poly(ethyleneoxide)(13) block copolymer; PE6400] that enables gene expression in up to 35% of muscle fibers from mouse tibial cranial muscle. PE6400 abolishes the ceiling effect on transgene expression of increasing amounts of naked DNA and permits long-term expression of the beta-galactosidase reporter gene in immunologically tolerant transgenic rats. This improvement in gene expression over naked DNA was observed irrespective of the reporter gene, ranging from 0.7 to 3.4 kb, and of the animal model used. In skeletal muscle, the PE6400 formulation led to a level of transfection efficiency similar to that obtained by electrotransfer. PE6400 also promotes high transgene expression in cardiac muscle. In contrast, PE6400-DNA formulations were inefficient in vitro in established cell lines and in isolated cardiomyocytes. When microinjected into the cell cytoplasm, PE6400 promotes DNA trafficking into the nucleus and induces gene expression. PE6400 provides a simple gene delivery system for skeletal and myocardial gene transfer. We propose that the PE6400 formulation could serve for the treatment of diseases primarily affecting muscle or for the expression of therapeutic proteins for local or systemic benefit.

The role of non-ionic surfactants on cationic lipid mediated gene transfer

Cationic lipid carriers were made of 1,2-dioleoyl-sn-glycero-3-trimethylammoniumpropane (DOTAP), squalene and different amounts of non-ionic surfactants. Various non-ionic surfactants were selected to elucidate the role of Tween 80 in the cationic lipid mediated gene delivery. They had a similar structure to Tween 80 such as various poly(ethyleneglycol) (PEG) chain lengths and acyl chain with different headgroups. For comparison, lipid carriers were also prepared with 1,2-dioleoyl-sn-glycero-3-trimethylammoniumpropane (DOTAP) and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE). Addition of non-ionic surfactants decreased the emulsion-DNA interaction and affected the transfection activity depending on the chain length and the content of PEG in the surfactant. Among the surfactants, Tween 80 yielded the best transgene expression without showing toxicity in COS-1 cells. The delivery mechanism of the complex was investigated by measuring the effects of endocytosis inhibitors (chloroquine and wortmannin). The emulsion-DNA complex seems to be taken up by the cells via endocytosis.

Gene gun bombardment with gold particles displays a particular Th2-promoting signal that over-rules the Th1-inducing effect of immunostimulatory CpG motifs in DNA vaccines

The mode of administering a DNA vaccine can influence the type of immune response induced by the vaccine. For instance, application of a DNA vaccine by gene gun typically induces a Th2-type reaction, whereas needle inoculation triggers a Th1 response. It has been proposed that the approximately 100-fold difference in the amount of DNA administered by these two methods is the critical factor determining whether a Th1 or a Th2 response is made. To test this hypothesis, BALB/c mice were immunized with two plasmid DNA constructs encoding different proteins (OspC/ZS7 of Borrelia burgdorferi and Bet v 1a, the major birch pollen allergen). Both vaccines were applied by needle and/or by gene gun immunization at the same and at different sites of injection. An analysis of the IgG subclass distribution and measurement of IFN-gamma after antigen-specific lymphoproliferation does not support the widely accepted view that Th2-type immunity induced by gene gun application is solely due to the low amount of injected plasmid DNA thus falling below the critical concentration of CpG motifs necessary for Th1-induction. Furthermore, the data also indicate a strong and even systemic adjuvant effect of the gene gun shot itself.

Generation of transgenic mice by transfection of pronuclear embryos using lipid-DNA complexes

We had previously developed a methodology to introduce foreign DNA into mouse eggs and embryos using cationic lipids as vectors. In this report we use this technique to produce transgenic animals. Mouse embryos at the pronuclear stage were transfected using a mixture of a plasmid DNA, encoding for a nuclear form of beta-galactosidase, and a commercial lipid transfection reagent. Embryos were washed and incubated overnight. Those that cleaved and develop to the 2-cell stage of normal appearance were transferred to the Fallopian tubes of pseudopregnant foster mothers. We analysed a total of 158 offspring and found two, a female and a male, to be transgenic (1.27% of the total). Integration of the foreign DNA in the female was showed by Southern blot. Both animals expressed the lacz in several organs, but none of them either displayed expression in the germ cells or transmitted the transgene to their offspring. Taken together our results show that lipid transfection can generate transgenic mice, but the efficiency needs to be improved for this method to be widely applied.