Association of metabolic gene polymorphisms with alcohol consumption in controls

The objectives were to study the association between metabolic genes involved in alcohol metabolism (CYP2E1 RsaI, CYP2E1 DraI, ADH1C, NQO1) and alcohol consumption in a large sample of healthy controls. Healthy subjects were selected from the International Collaborative Study on Genetic Susceptibility to Environmental Carcinogens (GSEC). Subjects with information on both alcohol consumption and at least one of the studied polymorphisms were included in the analysis (n=2224). Information on the amount of alcohol consumption was available for a subset of subjects (n=844). None of the studied genes was significantly associated with drinking habits. A significant heterogeneity with age was observed when studying the association between CYP2E1 RsaI and alcohol drinking. CYP2E1 RsaI polymorphism was significantly associated with being a never drinker at older ages (odds ratio [OR] 2.4, 95% confidence interval [CI] 1.2-4.8; at ages above 68 years), while the association was reversed at ages below 47 years (OR 0.5, 95% CI 0.2-1.4). For subjects with detailed information on alcohol intake, no association between alcohol quantity and polymorphisms in metabolic genes was observed; subjects carrying the NQO1 polymorphism tended to drink more than subjects carrying the wild-type alleles. Therefore, no significant association between CYP2E1 RsaI, CYP2E1 DraI, ADH1C, NQO1 polymorphisms and alcohol consumption was observed in healthy controls.

Persistent episomal transgene expression in liver following delivery of a scaffold/matrix attachment region containing non-viral vector

An ideal gene therapy vector should enable persistent transgene expression without limitations of safety and reproducibility. Here we report the development of a non-viral episomal plasmid DNA (pDNA) vector that appears to fulfil these criteria. This pDNA vector combines a scaffold/matrix attachment region (S/MAR) with a human liver-specific promoter (alpha1-antitrypsin (AAT)) in such a way that long-term expression is enabled in murine liver following hydrodynamic injection. Long-term expression is demonstrated by monitoring the longitudinal luciferase expression profile for up to 6 months by means of in situ bioluminescent imaging. All relevant control pDNA constructs expressing luciferase are unable to sustain significant transgene expression beyond 1 week post-administration. We establish that this shutdown of expression is due to promoter methylation. In contrast, the S/MAR element appears to inhibit methylation of the AAT promoter thereby preventing transgene silencing. Although this vector appears to be maintained as an episome throughout, we have no evidence for its establishment as a replicating entity. We conclude that the combination of a mammalian, tissue-specific promoter with the S/MAR element is sufficient to drive long-term episomal pDNA expression of genes in vivo.

Clinically applicable procedure for gene delivery to fetal gut by ultrasound-guided gastric injection: toward prenatal prevention of early-onset intestinal diseases

Targeting gene therapy vectors to the fetal intestinal tract could provide a novel means toward prevention of the early postnatal intestinal pathology of cystic fibrosis and other conditions, such as congenital enteropathy, that cause intestinal failure. Among these conditions, cystic fibrosis is by far the most common lethal genetic disease. It is caused by a functional absence or deficiency of the cystic fibrosis transmembrane conductance regulator and manifests in the gut as meconium ileus. Prenatal treatment of genetic disease may avoid early-onset tissue damage and immune sensitization, and may target cells that are less accessible in the adult. We investigated gene transfer to the fetal gut, using a minimally invasive injection technique. First-generation replication-deficient adenoviral vectors encoding the beta-galactosidase gene and transduction-enhancing agents were injected into the stomach of early-gestation fetal sheep (n = 8, 60 days of gestation; term, 145 days) under ultrasound guidance. Reporter gene expression was observed 2 days after injection in the villi of the gastrointestinal epithelia after 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside staining and beta-galactosidase immunohistochemistry of fetal tissues. Expression of beta-galactosidase, as measured by enzyme-linked immunosorbent assay, was enhanced after pretreatment of the fetal gut with sodium caprate, which opens tight junctions, and after adenovirus complexation with DEAE-dextran, which confers a positive charge to the virus. Instillation of the fluorocarbon perflubron after virus delivery resulted in tissue transduction from the fetal stomach to the colon. Using a clinically relevant technique, we have demonstrated widespread gene transfer to the fetal gastrointestinal epithelia.

Ultrasound-guided injection and occlusion of the trachea in fetal sheep

OBJECTIVES

To access the fetal sheep trachea by ultrasound-guided transthoracic injection in order to deliver gene therapy vectors or occlude the trachea with a detachable balloon.

METHODS

Fetal sheep were operated on at a mean gestational age of 102 (range, 81-116) days (term = 145 days). Under ultrasound guidance, either a 20-G spinal (for vector delivery) or a 16-G Kellett (for placement of an occlusive balloon) needle was inserted via the fetal thorax into the fetal trachea.

RESULTS

Using the 20-G spinal needle the trachea was accessed successfully in 33/36 fetuses, with 97% survival. Failure to inject was related to fetal position and gestational age. Blood vessel damage causing significant morbidity occurred in two fetuses (6%). Tracheal occlusion was achieved by puncturing the trachea with the 16-G needle and advancing an endoluminal balloon in three out of five attempts in a mean time of 17 (range, 16-19) min, with 100% survival. In one case, the balloon became sited within the accessory lobe bronchus and was not inflated. At postmortem examination 21 days later, all balloons remained inflated and occluded the trachea, and the lung-to-body weight ratio and airways morphometric indices were consistent with relative pulmonary hyperplasia in the obstructed lungs.

CONCLUSIONS

Ultrasound-guided transthoracic tracheal puncture is a reliable technique in fetal sheep, with low morbidity and mortality. Using this technique, a detachable endotracheal balloon can be placed to provoke pulmonary growth. Advances in needle design and balloon size may improve the success rate.

Gene therapy progress and prospects: fetal gene therapy--first proofs of concept--some adverse effects

Somatic gene delivery in utero is a novel approach to gene therapy for genetic disease based on the hypothesis that prenatal intervention may avoid the development of severe manifestations of early-onset disease, allow targeting of otherwise inaccessible tissues including expanding stem cell populations, induce tolerance against the therapeutic transgenic protein and thereby provide permanent somatic gene correction. This approach is particularly relevant in relation to prenatal screening programmes for severe genetic diseases as it could offer prevention as a third option to families faced with the prenatal diagnosis of a genetically affected child. Most investigations towards in utero gene therapy have been performed on mice and sheep fetuses as model animals for human disease and for the application of clinically relevant intervention techniques such as vector delivery by minimally invasive ultrasound guidance. Other animals such as dogs may serve as particular disease models and primates have to be considered in immediate preparation for clinical trials. Proof of principle for the hypothesis of fetal gene therapy has been provided during the last 2 years in mouse models for Crigler Najjar Disease, Leber's congenital amaurosis, Pompe's disease and haemophilia B showing long-term postnatal therapeutic effects and tolerance of the transgenic protein after in utero gene delivery. However, recently we have also observed a high incidence of liver tumours after in utero application of an early form of third-generation equine infectious anaemia virus vectors with SIN configuration. These findings highlight the need for more investigations into the safety and the ethical aspects of in utero gene therapy as well as for science-based public information on risks and benefits of this preventive gene therapy approach before application in humans can be contemplated.

Factors influencing adenovirus-mediated airway transduction in fetal mice

Intra-amniotic injection of adenovirus allows transduction of the fetal airways following natural fetal breathing movements. This administration method is promising for use in gene therapy for cystic fibrosis and other diseases for which the main target for exogenous gene expression is the lung. Here we have investigated factors that may affect the efficacy of gene transfer to the murine fetal lung. We examined marker compound distribution and transgene expression (from a first-generation adenoviral vector) at different stages of development. This demonstrated that fetal breathing movements at 15-16 days of gestation are of sufficient intensity to carry marker/vector into the fetal lungs. These movements can be significantly stimulated by the combination of intra-amniotic theophylline administration and postoperative exposure of the dam to elevated CO(2) levels. However, the most important factor for efficient and consistent pulmonary transgene delivery is the dose of adenoviral vector used, as both the degree of transduction and the percentage of lungs transduced increases with escalating viral dose.

Permanent partial phenotypic correction and tolerance in a mouse model of hemophilia B by stem cell gene delivery of human factor IX

Immune responses against an introduced transgenic protein are a potential risk in many gene replacement strategies to treat genetic disease. We have developed a gene delivery approach for hemophilia B based on lentiviral expression of human factor IX in purified hematopoietic stem cells. In both normal C57Bl/6J and hemophilic 129/Sv recipient mice, we observed the production of therapeutic levels of human factor IX, persisting for at least a year with tolerance to human factor IX antigen. Secondary and tertiary recipients also demonstrate long-term production of therapeutic levels of human factor IX and tolerance, even at very low levels of donor chimerism. Furthermore, in hemophilic mice, partial functional correction of treated mice and phenotypic rescue is achieved. These data show the potential of a stem cell approach to gene delivery to tolerize recipients to a secreted foreign transgenic protein and, with appropriate modification, may be of use in developing treatments for other genetic disorders.

Fetal and neonatal gene therapy: benefits and pitfalls

The current approaches to gene therapy of monogenetic diseases into mature organisms are confronted with several problems including the following: (1) the underlying genetic defect may have already caused irreversible pathological changes; (2) the level of sufficient protein expression to ameliorate or prevent the disease requires prohibitively large amounts of gene delivery vector; (3) adult tissues may be poorly infected by conventional vector systems dependent upon cellular proliferation for optimal infection, for example, oncoretrovirus vectors; (4) immune responses, either pre-existing or developing following vector delivery, may rapidly eliminate transgenic protein expression and prevent future effective intervention. Early gene transfer, in the neonatal or even fetal period, may overcome some or all of these obstacles. The mammalian fetus enjoys a uniquely protected environment in the womb, bathed in a biochemically and physically supportive fluid devoid of myriad extra-uterine pathogens. Strong physical and chemical barriers to infection might, perhaps, impede the frenetic cell division. The physical support and the biochemical support provided by the fetal-maternal placental interface may, therefore, minimize the onset of genetic diseases manifest early in life. The fetal organism must prepare itself for birth, but lacking a mature adaptive immune system may depend upon more primordial immune defences. It is the nature of these defences, and the vulnerabilities they protect, that are poorly understood in the context of gene therapy and might provide useful information for approaches to gene therapy in the young, as well as perhaps the mature organism.

Risk factors in alcohol associated breast cancer: alcohol dehydrogenase polymorphism and estrogens

Chronic alcohol consumption is associated with an increased risk for breast cancer, even if consumed in moderate doses. Since acetaldehyde is a carcinogenic factor associated with chronic alcohol consumption, individuals with the alcohol dehydrogenase 1C*1 allele (ADH1C*1 allele) seem to be at particular risk, since this allele encodes for a rapidly ethanol metabolizing enzyme leading to increased acetaldehyde levels. Since recent epidemiological studies demonstrated an increased risk for breast cancer for individuals with the ADH1C*1 allele, we have investigated here ADH1C genotypes in moderate alcohol consumers. Furthermore, estradiols are also known risk factors for breast cancer and acute alcohol ingestion in high doses results in increased serum estradiol concentrations. Thus, in the present study, we tested the effect of low ethanol doses on estrogen serum concentrations. We analyzed the ADH1C genotype in 117 moderate alcohol consumers with breast cancer and in 111 age-matched women with alcohol associated diseases without cancer (74 cirrhotics, 22 patients with pancreatitis and 15 alcohol dependent patients). In addition, 107 healthy controls were studied. Genotyping of the ADH1C-locus was performed using polymerase chain reaction-based restriction fragment length polymorphism methods on leukocyte DNA. To study the effects of ethanol on estradiol levels, ethanol in a dose of 0.225 g/kg body weight was given orally to 8 premenopausal women at various time points of their menstrual cycle. Thereafter estradiol serum concentrations were measured over time. The allele frequency of the ADH1C*1 allele was found to be significantly increased in moderate alcohol consumers with breast cancer as compared to age-matched alcoholic controls without cancer (62% vs. 41.9%, p=0.0035). Women with the ADH1C*1,1 genotype were found to be 1.8 times more at risk for breast cancer than those with another genotype (95% CI 1.431-2.330, p<0.001). Oral ethanol increased serum estradiol levels significantly by 27-38%. The data demonstrate that moderate alcohol consumers with the ADH1C*1 allele have an increased risk to develop breast cancer and even small amounts of alcohol increase serum estradiol levels significantly in premenopausal women especially in the midphase of the menstrual cycle.

Highly efficient EIAV-mediated in utero gene transfer and expression in the major muscle groups affected by Duchenne muscular dystrophy

Gene therapy for Duchenne muscular dystrophy has so far not been successful because of the difficulty in achieving efficient and permanent gene transfer to the large number of affected muscles and the development of immune reactions against vector and transgenic protein. In addition, the prenatal onset of disease complicates postnatal gene therapy. We have therefore proposed a fetal approach to overcome these barriers. We have applied beta-galactosidase expressing equine infectious anaemia virus (EIAV) lentiviruses pseudotyped with VSV-G by single or combined injection via different routes to the MF1 mouse fetus on day 15 of gestation and describe substantial gene delivery to the musculature. Highly efficient gene transfer to skeletal muscles, including the diaphragm and intercostal muscles, as well as to cardiac myocytes was observed and gene expression persisted for at least 15 months after administration of this integrating vector. These findings support the concept of in utero gene delivery for therapeutic and long-term prevention/correction of muscular dystrophies and pave the way for a future application in the clinic.

Widespread and efficient marker gene expression in the airway epithelia of fetal sheep after minimally invasive tracheal application of recombinant adenovirus in utero

Cystic fibrosis is a common lethal genetic disease caused by functional absence of the cystic fibrosis transmembrane conductance regulator (CFTR). Although a candidate disease for in utero gene therapy, demonstration of potentially therapeutic levels of transgene expression in the fetal airways after minimally invasive gene delivery is a mandatory prerequisite before application of this approach in humans can be considered. We report here on the delivery of a beta-galactosidase expressing adenovirus directly to the airways of fetal sheep in utero using ultrasound-guided percutaneous injection of the trachea in the fetal chest. Injection of adenoviral particles to the fetal airways was not associated with mortality and resulted in low-level expression in the peripheral airways. However, complexation of the virus with DEAE dextran, which confers a positive charge to the virus, and pretreatment of the airways with Na-caprate, which opens tight junctions, increased transgene expression, and a combination of these two enhancers resulted in widespread and efficient gene transfer of the fetal trachea and bronchial tree. Using a percutaneous ultrasound-guided injection technique, we have clearly demonstrated proof of principle for substantial transgene delivery to the fetal airways providing levels of gene expression that could be relevant for a therapeutic application of CFTR expressing vectors.

Reduced toxicity of F-deficient Sendai virus vector in the mouse fetus

Current concerns over insertional mutagenesis by retroviral vectors mitigate investigations into alternative, potentially persistent gene therapy vector systems not dependent on genomic integration, such as Sendai virus vectors (SeVV). Prenatal gene therapy requires efficient gene delivery to several tissues, which may not be achievable by somatic gene transfer to the adult. Initially, to test the potential and tropism of the SeVV for gene delivery to fetal tissues, first-generation (replication- and propagation-competent) recombinant SeVV, expressing beta-galactosidase was introduced into late gestation immunocompetent mice via the amniotic and peritoneal cavities and the yolk sac vessels. At 2 days, this resulted in very high levels of expression particularly in the airway epithelium, mesothelium and vascular endothelium, respectively. However, as expected, substantial vector toxicity was observed. The efficiency of gene transfer and the level of gene expression were then examined using a second-generation SeVV. The second generation was developed to be still capable of cytoplasmic RNA replication and therefore high-level gene expression, but incapable of vector spread due to lack of the gene for viral F-protein. Vector was introduced into the fetal amniotic and peritoneal cavities, intravascularly, intramuscularly and intraspinally; at 2 days, expression was observed in the airway epithelia, peritoneal mesothelia, unidentified cells in the gut wall, locally at the site of muscle injection and in the dorsal root ganglia, respectively. Mortality was dramatically diminished compared with the first-generation vector.

The Hopes and Fears of In Utero Gene Therapy for Genetic Disease—A Review

Somatic gene delivery in utero is a novel approach to gene therapy for genetic disease. It is based on the concept that application of gene therapy vectors to the fetus in utero may prevent the development of early disease related tissue damage, may allow targeting of otherwise inaccessible organs, tissues and still expanding stem cell populations and may also provide postnatal tolerance against the therapeutic transgenic protein. This review outlines the hypothesis and scientific background of in utero gene therapy and addresses some of the frequently expressed concerns raised by this still experimental, potentially preventive gene therapy approach. We describe and discuss the choice of vectors, of animal models and routes of administration to the fetus. We address potential risk factors of prenatal gene therapy such as vector toxicity, inadvertent germ line modification, developmental aberration and oncogenesis as well as specific risks of this procedure for the fetus and mother and discuss their ethical implications.

Mutational effects of retrovirus insertion on the genome of V79 cells by an attenuated retrovirus vector: implications for gene therapy

Attenuated retroviruses are currently the most widely used vectors in clinical gene therapy because of their potential to effect stable and permanent gene transfer. Since gene delivery is accompanied by random insertion of foreign genetic material into the recipient chromosomal DNA, the potential for insertional mutagenesis exists. In this study, we used a defective retrovirus vector containing a selectable marker, the hygromycin phosphotransferase gene, to investigate the mutagenic effects of vector integration on the mammalian genome. V79 Chinese hamster cells were infected with virus supernatants or by coculture with virus producer cells, and provirus insertion events occurred at low and high frequencies, respectively. The frequency of hprt mutagenesis was increased by a factor of 2.3 over the spontaneous hprt mutation frequency only following multiple provirus insertions/cell genome. Multiple provirus insertions (>3/genome) resulted in instability at the hprt locus in 63% of the virally induced hprt mutants, as indicated by rearrangements at the molecular level, whereas no rearrangements were found when the provirus copy number was 1-2/genome. To demonstrate direct proviral involvement in mutagenesis, the defective MLV vector was retrieved along with flanking genomic hprt sequences from one mutant, and localized within intron 5 of the hprt gene. These data suggest that provirus copy number is a key factor when considering the potential hazards of using retrovirus vectors for gene therapy.

Percutaneous ultrasound-guided injection of the trachea in fetal sheep: a novel technique to target the fetal airways

OBJECTIVE

To access the fetal airways percutaneously using ultrasound-guided injection of the fetal trachea in sheep.

METHODS

Adenoviral gene therapy vectors and transduction-enhancing agents were delivered to the trachea via a needle inserted through the thorax or the neck of late-gestation (0.9 term, n = 3) or mid-gestation (0.5-0.8 term, n = 18) fetal sheep using ultrasound guidance.

RESULTS

Injection of the trachea in the fetal thorax was successful in 16 out of 18 fetuses and achieved at the first attempt in 9 fetuses within 12 min [mean 7 min and 31 s +/- (SD) 3 min and 4 s]. Survival was 100%. Injecting the trachea in the neck was less successful.

CONCLUSIONS

The fetal trachea of the sheep can be safely accessed by percutaneous ultrasound-guided injection to deliver vectors directly to the fetal airways for gene therapy. It may also enable tracheal occlusion for the antenatal treatment of congenital diaphragmatic hernia without the need for endoscopy or open surgery.

Long-term transgene expression by administration of a lentivirus-based vector to the fetal circulation of immuno-competent mice

Inefficient gene transfer, inaccessibility of stem cell compartments, transient gene expression, and adverse immune and inflammatory reactions to vector and transgenic protein are major barriers to successful in vivo application of gene therapy for most genetic diseases. Prenatal gene therapy with integrating vectors may overcome these problems and prevent early irreparable organ damage. To this end, high-dose attenuated VSV-G pseudotyped equine infectious anaemia virus (EIAV) encoding beta-galactosidase under the CMV promoter was injected into the fetal circulation of immuno-competent MF1 mice. We saw prolonged, extensive gene expression in the liver, heart, brain and muscle, and to a lesser extent in the kidney and lung of postnatal mice. Progressive clustered hepatocyte staining suggests clonal expansion of cells stably transduced. We thus provide proof of principle for efficient gene delivery and persistent transgene expression after prenatal application of the EIAV vector and its potential for permanent correction of genetic diseases.

Gene transfer by adenovirus-mimetic peptides in the presence of a cationic lipid and/or adenovirus. Analysis of the contribution of the viral and nonviral components

Peptide and cationic lipid-based gene transfer vectors have shown promise for gene therapy but are still less efficient than viral gene transfer vectors. We have examined the mechanism of gene transfer of different adenovirus-mimetic peptides in the presence and absence of a cationic lipid, lipofectamine and/or adenovirus with the aim of improving the design of nonviral vectors for efficient gene transfer. Three polylysine-adenovirus-mimetic peptides were synthesised and examined for their efficacy for gene transfer. Transfection levels in four cell lines: adenovirus permissive human tracheal epithelial (56FHTE8o(-)), human lung carcinoma (A549), human colon carcinoma (Caco-2) cells, and adenovirus low-permissive Chinese hamster ovary (CHO) cells, were examined. The polylysine-adenovirus-mimetic peptides increased the level of transfection of a reporter transgene in all cell lines. Transfection was substantially increased when an adenovirus was added to cells after pre-incubation with the vector complexes. Formulation of the peptide vector complexes with lipofectamine increased their transfection efficacy and the subsequent addition of an adenovirus increased transfection levels even further but only in permissive cells. Pre-incubation of cells with lipofectamine-peptide vector complexes increased cell binding of the adenovirus but uptake was only increased in intermediate- or non-permissive cells. The addition of lipofectamine increased transgene expression of a recombinant adenovirus in non-permissive cells but not in permissive cells. Enhancement with an adenovirus of peptide vector gene transfer is probably due to more efficient endosome escape while enhancement of gene transfer by peptide vectors complexed to lipofectamine is due to an increase in cellular binding and/or internalisation of the adenovirus.

On the scientific and ethical issues of fetal somatic gene therapy

Fetal somatic gene therapy is often seen as an ethically particularly controversial field of gene therapy. This review outlines the hypothesis and scientific background of in utero gene therapy and addresses some of the frequently raised questions and concerns in relation to this still experimental, potentially preventive gene therapy approach. We discuss here the choice of vectors, of animal models and routes of administration to the fetus. We address the relation of fetal gene therapy to abortion, to post-implantation selection and postnatal gene therapy and the concerns of inadvertent germ-line modification. Our views on the specific risks of prenatal gene therapy and on the particular prerequisites that have to be met before human application can be considered are presented.

Characterisation of LMD virus-like nanoparticles self-assembled from cationic liposomes, adenovirus core peptide mu and plasmid DNA

Liposome:mu:DNA (LMD) is a ternary nucleic acid delivery system built around the mu peptide associated with the condensed core complex of the adenovirus. LMD is prepared by precondensing plasmid DNA (D) with mu peptide (M) in a 1:0.6 (w/w) ratio and then combining these mu:DNA (MD) complexes with extruded cationic liposomes (L) resulting in a final lipid:mu:DNA ratio of 12:0.6:1 (w/w/w). Correct buffer conditions, reagent concentrations and rates of mixing are all crucial to success. However, once optimal conditions are established, homogeneous LMD particles (120 +/- 30 nm) will result that each appear to comprise an MD particle encapsulated within a cationic bilammellar liposome. LMD particles can be formulated reproducibly, they are amenable to long-term storage (>1 month) at -80 degrees C and are stable to aggregation at a plasmid DNA concentration up to 5 mg/ml (15 mM nucleotide concentration). Furthermore, LMD transfections are significantly more time and dose efficient in vitro than cationic liposome-plasmid DNA (LD) transfections. Transfection times as short as 10 min and plasmid DNA doses as low as 0.001 microg/well result in significant gene expression. LMD transfections will also take place in the presence of biological fluids (eg up to 100% serum) giving 15-25% the level of gene expression observed in the absence of serum. Results from confocal microscopy experiments using fluorescent-labelled LMD particles suggest that endocytosis is not a significant barrier to LMD transfection, although the nuclear membrane still is. We also confirm that topical lung transfection in vivo by LMD is at least equal in absolute terms with transfection mediated by GL-67:DOPE:DMPE-PEG(5000) (1:2:0.05 m/m/m), an accepted 'gold-standard' non-viral vector system for topical lung transfection, and is in fact at least six-fold more dose efficient. All these features make LMD an important new non-viral vector platform system from which to derive tailor-made non-viral delivery systems by a process of systematic modular upgrading.

Perspectives on gene therapy for cystic fibrosis airway disease

Since the discovery of the cystic fibrosis transmembrane conductance regulator (CFTR) gene nearly 12 years ago, cystic fibrosis (CF) has become one of the most intensively investigated monogenetic disorders considered approachable by gene therapy. This has resulted in over 20 clinical trials currently under way, concluded or awaiting approval. Despite the initial promise of gene therapy for CF, and the demonstration of successful gene transfer to the nose and airways of individuals, it has not so far been as effective as initially projected. Here we discuss the rationale behind CF gene therapy and dissect the vast array of literature representing the work that ultimately brought about the current phase I/II clinical trials. In the context of human trials, we review the limitations of current vector systems for CF gene therapy. We come to the conclusion that at present none of the application methods and vector systems are able to achieve the level and persistence of CFTR gene expression in the affected epithelia of CF patients that is required for therapeutic success. We also outline the challenges that must be overcome and describe some of the novel approaches to be taken in order to attain the curative therapy that was originally envisaged for this disease.

Metabolic gene polymorphism frequencies in control populations

Using the International Project on Genetic Susceptibility to Environmental Carcinogens (GSEC) database containing information on over 15,000 control (noncancer) subjects, the allele and genotype frequencies for many of the more commonly studied metabolic genes (CYP1A1, CYP2E1, CYP2D6, GSTM1, GSTT1, NAT2, GSTP, and EPHX) in the human population were determined. Major and significant differences in these frequencies were observed between Caucasians (n = 12,525), Asians (n = 2,136), and Africans and African Americans (n = 996), and some, but much less, heterogeneity was observed within Caucasian populations from different countries. No differences in allele frequencies were seen by age, sex, or type of controls (hospital patients versus population controls). No examples of linkage disequilibrium between the different loci were detected based on comparison of observed and expected frequencies for combinations of specific alleles.

The nuclear pore complex is involved in nuclear transfer of plasmid DNA condensed with an oligolysine-RGD peptide containing nuclear localisation properties

One of the major barriers to efficient gene transfer and expression of nonviral vectors for gene therapy is passage across the nuclear envelope. We have previously shown that an oligolysine-RGD peptide that condenses plasmid DNA and binds to cell surface integrins can mediate increased internalisation of plasmid DNA into cells and synergistic enhancement of gene expression when complexed to a cationic lipid. In this report, we show that this enhancement is due to increased nuclear transfer of the plasmid DNA. We have applied the digitonin-permeabilised cell system that has been well established for the study of the nuclear transport of proteins to examine the nuclear transfer of plasmid DNA. Nuclear transfer of plasmid DNA complexed to an oligolysine-RGD peptide and lipofectamine appears to be an energy-dependent process involving the nuclear pore complex, since it is inhibited at 4 degrees C and by treatment with wheat germ agglutinin or with an antibody to the nuclear pore complex which all block nuclear protein import. In accordance with active nuclear transport, we have shown that all these treatments inhibit expression of a luciferase reporter plasmid in permeabilised cells. Nuclear transfer of pDNA is enhanced in mitotic cells, but cell division is not a prerequisite for transfer. We propose that the oligolysine-RGD peptide acts as a nuclear localisation signal and that the cationic lipid is more important for cell entry and endosome destabilisation than nuclear transfer.

An araC-controlled bacterial cre expression system to produce DNA minicircle vectors for nuclear and mitochondrial gene therapy

The presence of CpG motifs and their associated sequences in bacterial DNA causes an immunotoxic response following the delivery of these plasmid vectors into mammalian hosts. We describe a biotechnological approach to the elimination of this problem by the creation of a bacterial cre recombinase expression system, tightly controlled by the arabinose regulon. This permits the Cre-mediated and -directed excision of the entire bacterial vector sequences from plasmid constructs to create supercoiled gene expression minicircles for gene therapy. Minicircle yields using standard culture volumes are sufficient for most in vitro and in vivo applications whereas minicircle expression in vitro is significantly increased over standard plasmid transfection. By the simple expedient of removing the bacterial DNA complement, we significantly reduce the size and CpG content of these expression vectors, which should also reduce DNA-induced inflammatory responses in a dose-dependent manner. We further describe the generation of minicircle expression vectors for mammalian mitochondrial gene therapy, for which no other vector systems currently exist. The removal of bacterial vector sequences should permit appropriate transcription and correct transcriptional cleavage from the mitochondrial minicircle constructs in a mitochondrial environment and brings the realization of mitochondrial gene therapy a step closer.

A novel human suspension culture packaging cell line for production of high-titre retroviral vectors

Retroviruses are currently the most widely used vectors in clinical trials for gene therapy. These vectors are, however, limited by low titres partly due to the restrictive nature of monolayer cell culture. We have developed a stable suspension producer cell line derived from human lymphoblastoid cells (WIL-2) by electroporating these cells with the necessary trans components required for production of defective retrovirus particles which encode a nuclear localising beta-galactosidase gene. We show that this anchorage-independent cell line generates viruses at a titre of 7 x 10(5) iu/ml on NIH3T3 indicator cells which remains constant after at least 2 months in culture. The producer cells can be cultured at a density of 6 x 10(6) cells/ml with consistent virus titre production. WIL-2 can also be grown as single cells by rotation culture while maintaining virus production. By treating the cells with the transcriptional activator sodium butyrate titres above 1 x 10(6) i.u./ml are achieved. Concentrating viral supernatants by ultrafiltration can further increase virus titre to 5 x 10(8) i.u./ml. Even at these high titres no replication-competent virus was detected. Virus titre fell only slightly when cells were placed in serum-free media before harvest. The generation of this novel cell line provides proof-of-principle that large-scale production of retroviral vectors in serum-free growth conditions can be safely generated for use in gene therapy.

A novel peptide, THALWHT, for the targeting of human airway epithelia

Targeting gene vectors to human airway epithelial cells may help to overcome the current inefficiency of gene transfer as the major problem confronting cystic fibrosis gene therapy. To elucidate novel ligands targeting abundant, apically located receptors on airway epithelial cells, a phage display library was screened for peptides binding with high affinity to such cells. This screening yielded a selectively enriched amino acid sequence, Thr-His-Ala-Leu-Trp-His-Thr (THALWHT). Subsequent binding studies confirmed that THALWHT-displaying phages bound much stronger than phages displaying control peptides to human airway epithelial cells. In contrast, no significant binding differences were observed on a variety of non-airway-derived human cell lines suggesting selective binding of the THALWHT motif to airway epithelia. Confocal microscopy of such cells after exposure to labelled synthetic THALWHT peptide indicated that its binding is followed by specific internalisation via endocytosis. A synthetic peptide comprising a cyclic CTHALWHTC domain and a DNA binding moiety enabled efficient targeted gene delivery into human airway epithelial cells. Competition assays with free THALWHT peptide confirmed the specificity of gene delivery. Thus, the THALWHT motif may prove a useful targeting moiety for both non-viral and viral gene therapy vectors.

Retargeting of adenoviral vectors to neurons using the Hc fragment of tetanus toxin

The Hc fragment of tetanus toxin (Hc) retains the specific nerve cell binding and transport properties of the holotoxin, but lacks any toxicity. We are investigating the potential for utilising its neurotropism for targeted gene delivery to the central nervous system. Previously we reported the use of Hc-polylysine conjugates for selective gene transfer into neuronal cells in vitro. However, as attempts to apply these constructs in vivo were not successful, we have extended these studies to modification of the tropism of adenoviral vectors. Either Hc-polylysine conjugates or the Fab fragment of a neutralising anti-knob antibody covalently bound to Hc were attached to the virus. Infection of neuronal and non-neuronal cell lines with retargeted virus showed highly increased neuronal cell selectivity, but no significant enhancement of gene delivery into these cells. High concentrations of free Hc blocked the infectivity of the retargeted vector efficiently. Intramuscular injection of retargeted virus into mouse tongues resulted in selective gene transfer to the neurons of the hypoglossal nucleus, where no pathological changes were observed. As differentiated neurons do not undergo cell division, appropriate vectors carrying a thymidine kinase gene, which allows selective elimination of dividing cells, may be exploitable for the treatment of tumours of the central nervous system. The demonstrated suitability of the Hc fragment of tetanus toxin as targeting moiety for viral vectors also indicates a potential for gene therapy of inherited neurodegenerative diseases such as spinal muscular atrophy.

Role of alcohol dehydrogenase 3 and cytochrome P-4502E1 genotypes in susceptibility to cancers of the upper aerodigestive tract

Alcohol is a recognized risk factor for upper aerodigestive tract (UAT) cancers, but the mechanism by which alcohol causes cancer remains obscure. Ethanol is oxidized to acetaldehyde (the suspected carcinogenic agent in alcohol) by alcohol dehydrogenases (ADHs) and cytochrome P-4502E1 (CYP2E1), both of which exhibit great inter-individual variability in activity. The hypothesis that these polymorphisms influence susceptibility to alcohol-related cancers remains poorly documented. We investigated whether ADH(3) and CYP2E1 DraI and RsaI genotypes modified the risk of UAT cancers among 121 oral cavity/pharyngeal cancer patients, 129 laryngeal cancer patients, and 172 controls, all French Caucasians. Cancer risks and gene-alcohol interactions were analyzed by unconditional logistic regression, accounting for potential confounders. ADH(3) genotype was not associated with UAT cancer. In contrast, a 2-fold risk of oral cavity/pharyngeal (OR = 2.0, 95% CI 1.0-3.9) and laryngeal (OR = 1.8, 95% CI 1.0-3.5) cancers was observed for carriers of the CYP2E1 DraI C variant allele compared with other individuals. The risk associated with the CYP2E1 RsaI c2 variant allele also increased for oral cavity/pharyngeal cancer (OR = 2.6, 95% CI 1.0-6. 6). The effects of ADH(3) or CYP2E1 genotype and alcohol or tobacco were independent. The highest risk of oral cavity/pharyngeal cancer was observed among the heaviest drinkers (>80 g/day) with the CYP2E1 DraI C allele (OR = 5.8, 95% CI 1.9-18.2) or the CYP2E1 RsaI c2 allele (OR = 7.2, 95% CI 1.4-38.2) compared with lighter drinkers with other genotypes. Our study suggests that CYP2E1 genotype modifies the risk of UAT cancers, but due to the low frequency of CYP2E1 variant alleles, large-scale studies are needed to confirm our findings.

Haemoglobin interferes with the ex vivo luciferase luminescence assay: consequence for detection of luciferase reporter gene expression in vivo

The luciferase reporter gene is a useful tool for determining the efficacy of transfection of plasmid DNA and adenovirus-mediated gene transfer in vivo. However, we report here that the haemoglobin present in tissue samples can mask the detection of the luciferase activity and lead to underestimation of the luciferase levels. We evaluated the degree of interference in different organ samples of mice and investigated the possibilities for removal of haemoglobin from tissue samples by: (1) perfusion of the whole animal; (2) different hypotonic treatments lysing preferentially red blood cells; and (3) chromatographic separation. Removal of haemoglobin resulted in significantly improved detection of luciferase activity from tissue samples. The results indicate that the luciferase activity determined in tissue samples may not reflect the actual level of reporter gene expression, if contaminating blood is not taken into consideration.

Exploiting viral cell-targeting abilities in a single polypeptide, non-infectious, recombinant vehicle for integrin-mediated DNA delivery and gene expression

A recombinant, multifunctional protein has been designed for optimized, cell-targeted DNA delivery and gene expression in mammalian cells. This hybrid construct comprises a viral peptide ligand for integrin alpha(V)beta(3) binding, a DNA-condensing poly-L-lysine domain, and a complete, functional beta-galactosidase protein that serves simultaneously as purification tag and DNA-shielding agent. This recombinant protein is stable; it has been produced successfully in Escherichia coli and can be purified in a single step by affinity chromatography. At optimal molar ratios, mixtures of this vector and a luciferase-reporter plasmid form stable complexes that transfect cultured cells. After exposure to these cell-targeted complexes, steady levels of gene expression are observed for more than 3 days after transfection, representing between 20 and 40% of those achieved with untargeted, lipid-based DNA-condensing agents. The principle to include viral motifs for cell infection in single polypeptide recombinant proteins represents a promising approach towards the design of non-viral modular DNA transfer vectors that conserve the cell-target- ing specificity of native viruses and that do not need further processing after bioproduction in a recombinant host.

Tri-iodothyronine and a deleted form of hepatocyte growth factor act synergistically to enhance liver proliferation and enable in vivo retroviral gene transfer via the peripheral venous system

Retroviral vectors integrate into the target cell genome in a stable manner and therefore offer the potential for permanent correction of the genetic diseases that affect the liver. These vectors, however, usually require cell division to occur in order to allow provirus entry into the nucleus. We have explored clinically acceptable methods to improve the efficiency of retroviral gene transfer to the liver, which avoid the need for liver damage. Tri-iodothyronine (T3) and recombinant hepatocyte growth factor have previously been used to induce hepatocyte proliferation in rat livers and allow in vivo retroviral gene transfer. We investigated the combined effects of these growth factors, with their differing mechanisms of action, on hepatocyte proliferation in vivo and assessed their effectiveness in priming cells for retroviral gene transfer. During the phase of hepatocyte proliferation retrovirus was administered via either the portal or tail vein. Acting synergistically, T3 and a truncated form of recombinant hepatocyte growth factor (dHGF) induced 30% of hepatocytes in normal rat liver to enter DNA synthesis at 24 h. This increased proliferation enabled the liver to be transduced in vivo by retroviral vectors via either the portal or peripheral venous system, achieving transduction efficiencies of 6.9 +/- 1.6% and 4.3 +/- 0.4% respectively. Thus, the liver can be simply and conveniently transduced in vivo with integrating vectors, introduced via the peripheral venous system during a wave of growth factor-induced proliferation, pointing the way to clinically applicable gene transfer techniques.

Genetic polymorphism of alcohol dehydrogenase in europeans: the ADH2*2 allele decreases the risk for alcoholism and is associated with ADH3*1

Polymorphism at the ADH2 and ADH3 loci of alcohol dehydrogenase (ADH) has been shown to have an effect on the predisposition to alcoholism in Asian individuals. However, the results are not conclusive for white individuals. We have analyzed the ADH genotype of 876 white individuals from Spain (n = 251), France (n = 160), Germany (n = 184), Sweden (n = 88), and Poland (n = 193). Peripheral blood samples from healthy controls and groups of patients with viral cirrhosis and alcohol-induced cirrhosis, as well as alcoholics with no liver disease, were collected on filter paper. Genotyping of the ADH2 and ADH3 loci was performed using polymerase chain reaction-restriction fragment length polymorphism methods on white cell DNA. In healthy controls, ADH2*2 frequencies ranged from 0% (France) to 5.4% (Spain), whereas ADH3*1 frequencies ranged from 47. 6% (Germany) to 62.5% (Sweden). Statistically significant differences were not found, however, between controls from different countries, nor between patients with alcoholism and/or liver disease. When all individuals were grouped in nonalcoholics (n = 451) and alcoholics (n = 425), ADH2*2 frequency was higher in nonalcoholics (3.8%) than in alcoholics (1.3%) (P =.0016), whereas the ADH3 alleles did not show differences. Linkage disequilibrium was found between ADH2 and ADH3, resulting in an association of the alleles ADH2*2 and ADH3*1, both coding for the most active enzymatic forms. In conclusion, the ADH2*2 allele decreases the risk for alcoholism, whereas the ADH2*2 and ADH3*1 alleles are found to be associated in the European population.

Selective in vivo transfection of murine biliary epithelia using polycation-enhanced adenovirus

We have investigated the use of polycations to increase adenovirus-mediated expression of transgenic protein to the biliary epithelia with a view to gene therapy for hepatobiliary disease in CF. We have shown that adenovirus carrying the beta-galactosidase transgene transfect both human and mouse biliary epithelia in primary culture and that in both instances adenovirus transfection can be significantly increased by co-complexing with polycation. In vivo administration of 1 x 109 p.f.u. adenovirus co-complexed with the polyamine polyethyenimine (PEI) into the mouse biliary duct leads to >80% positively stained biliary epithelia while adenovirus alone at the same titre infected <5% biliary epithelia. We suggest that the use of low titre polycation enhanced adenoviral delivery to the biliary tree of CF patients could be of therapeutic significance. As a prelude to an extensive in vivo functional investigation in CF null mice we have shown that Ad5/polycation complexes deliver functional CFTR to non-CFTR expressing cells in vitro more efficiently than Ad5 alone.

Synergistic growth factors enhance rat liver proliferation and enable retroviral gene transfer via a peripheral vein

BACKGROUND & AIMS

Genetic diseases reflecting abnormal hepatocyte function are potentially curable through gene therapy. Retroviral vectors offer the potential for permanent correction of such conditions. These vectors generally require cell division to occur to allow provirus entry into the nucleus, initiated in many experimental protocols by partial hepatectomy. We have explored methods to improve the efficiency of retroviral gene transfer that avoid the need for liver damage.

METHODS

Triiodothyronine (T3) and keratinocyte growth factor (KGF) were used to induce hepatic proliferation in rats. The effects of intraportal and peripheral administration of a modified retrovirus that encoded the Lac Z gene during growth factor-induced liver hyperplasia were analyzed.

RESULTS

T3 initiated hepatocyte proliferation midzonally; after KGF, proliferation was more diffuse. Optimal concentrations of T3 and KGF acted synergistically to induce proliferation in 61% of hepatocytes in the intact liver. This enabled in vivo hepatocyte transduction, leading to gene expression by up to 7.3% of hepatocytes after intraportal retroviral vector administration and 7. 1% after peripheral venous administration.

CONCLUSIONS

T3 and KGF act synergistically to induce hepatocyte proliferation in undamaged liver. The liver can be simply transduced with integrating vectors via the peripheral venous system during a wave of growth factor-induced proliferation.

Introduction of chloramphenicol resistance into the modified mouse mitochondrial genome: cloning of unstable sequences by passage through yeast

Despite increasing awareness of the importance of the mitochondrial genome in human pathology, very few attempts have been made so far toward genetic engineering of mitochondrial DNA (mtDNA). One of the reasons for this slow progress is the difficulty of cloning mtDNA in Escherichia coli, a trait in common with repetitive or palindromic sequences, and some viral sequences. We have previously made a construct containing the entire mouse mitochondrial genome and a cDNA sequence coding for human ornithine transcarbamylase in a yeast/bacterial shuttle vector, which can be stably maintained in E. coli. We wished to modify this vector for mitochondrial gene therapy by the addition of mitochondrial chloramphenicol resistance, conferred by a point mutation in the 16S rRNA gene. Attempts to modify this construct by a straightforward cloning approach in E. coli proved unsuccessful. Two successful strategies for modification of large unstable constructs in both E. coli and the yeast Saccharomyces cerevisiae are compared here.

Cell delivery, intracellular trafficking and expression of an integrin-mediated gene transfer vector in tracheal epithelial cells

The mechanism of cell entry and intracellular fate of a gene transfer vector composed of a receptor-targeting, DNA-condensing peptide, RGD-oligolysine, a luciferase encoding plasmid DNA (pDNA) and a cationic liposome was examined. We demonstrate by confocal microscopy, electron microscopy and subcellular fractionation that the major mechanism of entry of the vector is endocytic. The vector complex rapidly (5 min) internalizes into early endosomes, then late endosomes and lysosomes. Entry involves, at least in part, clathrin-coated pit-mediated endocytosis since different conditions or drugs known to influence this pathway modify both uptake of pDNA and its expression. The observed increase in expression with addition of a lip some correlated with an increase in the rate of transfer of the pDNA to lysosomes, a decrease in intracellular recycling and exocytosis of the pDNA and an increase in the amount of pDNA in the nuclear fraction. Trafficking within the cell involved endosome fusion and the acid environment of the endosomes-lysosomes was beneficial for expression. After 30 min both the peptide and pDNA localized to the nucleus and the amount of intact pDNA in the nuclear fraction was highest with liposome and peptide. A better understanding of the cellular mechanisms by which vectors transfer to and traffic in cells should help design improved vectors.

Therapeutic plasma concentrations of human factor IX in mice after gene delivery into the amniotic cavity: a model for the prenatal treatment of haemophilia B

BACKGROUND

Several groups including our own have reported gene delivery to fetal organs by vector administration into the amniotic cavity. Based on these studies we hypothesised that the large surface of the fetal skin may be exploitable for high level production of systemically required gene products to be released into the fetal circulation.

METHODS

We administered E1/E3-deleted adenoviral vectors carrying a bacterial beta-galactosidase gene or the human coagulation factor IX gene into the amniotic cavities of mid- to late-gestation mouse fetuses. The concentrations of human factor IX in the plasma of fetal or new-born mice were determined by ELISA. Reverse transcription PCR was used to identify sites of transgene expression.

RESULTS

Application of 5 x 10(8) infectious units of the factor IX gene vector in utero resulted in plasma concentrations of human factor IX of up to 1.2 microg/ml without significant decrease in fetal survival. Transgenic protein was found to be produced in the fetal skin, mucosae and amniotic membranes and was shown to be present for several days after birth of healthy pups.

CONCLUSION

As ultrasound-guided amniocentesis in humans is a well-established diagnostic procedure, delivery of the factor IX gene into the amniotic cavity appears to be a safe route for prenatal treatment of haemophilia B and may prevent haemorrhagic complications such as intracranial bleeding during delivery. Our study allowed for the first time a quantification of the expression of a potentially therapeutic transgene in rodents after prenatal gene delivery. It thus provides a model for the prenatal treatment of haemophilia B, but may also serve as a pathfinder to gene therapy of inheritable skin disorders such as epidermolysis bullosa.

Targeted gene delivery into alpha9beta1-integrin-displaying cells by a synthetic peptide

We have investigated the usefulness of two small synthetic peptides comprising either a linear or a cyclic PLAEIDGIEL domain and a DNA-binding moiety of 16 lysine residues to mediate gene transfer selectively into alpha9beta1-integrin-displaying cells. Such specific gene delivery could only be achieved with the peptide containing the cyclic PLAEIDGIEL domain. However, inclusion of the cationic liposome Lipofect-AMINE into the peptide/DNA complexes resulted for both peptides in efficient gene transfer with significant targeting specificity. Naturally, the integrin alpha9beta1 is present only in a few highly specialised tissues and abundant throughout the human airway epithelia in vivo. Targeting gene vectors to this integrin therefore appears a useful approach to gene therapy of lung diseases such as cystic fibrosis. As the integrin alpha9beta1 is associated with tissue differentiation during foetal development and may cause resurgence of the foetal phenotype in colon cancers, such vectors may also be applicable for prenatal and cancer gene therapy.

Successful expression of beta-galactosidase and factor IX transgenes in fetal and neonatal sheep after ultrasound-guided percutaneous adenovirus vector administration into the umbilical vein

In utero somatic gene therapy in the later stages of pregnancy may allow targeting of organ systems which are difficult to reach later in life and to prevent the development of tissue damage otherwise caused by the early onset of inherited diseases. We report here on the percutaneous delivery of two adenoviral vectors, containing the beta-galactosidase reporter gene and the human Factor IX gene respectively, to the fetal liver and circulation by ultrasound-guided umbilical vein puncture similar to procedures used in human pregnancy. Vector spread, as detected by PCR analysis for the beta-galactosidase encoding vector, was found in almost all fetal and neonatal organs and in the maternal liver. Expression of the beta-galactosidase transgene was detected in many fetal tissues by RT-PCR. High beta-galactosidase production was shown by immuno-histochemistry predominantly in the liver, where about 30percent of the hepatocytes stained positive, and in the adrenal cortex. Production of factor IX was determined by ELISA in the plasma of treated fetuses and newborn lambs and reached at birth up to 80percent of the normal human plasma concentration. This demonstrates a very hopeful proof of principle for the development of prenatal treatment of many genetic diseases but also requires more detailed investigations with respect to the observed systemic spread of the vector.

Calcium ions as efficient cofactor of polycation-mediated gene transfer

We investigated the effect of calcium on the transfection of non-viral DNA transfer systems. Cationic proteins such as the nuclear protein H1, the polycation polylysine and a number of commercial transfection agents exhibited high transfection rates in the presence of Ca2+. Without Ca2+ H1 and HMG1 were inactive in transfection of the human permanent endothelial cell line ECV 304 while cationic liposomes such as Lipofectin and Lipofectamine did not show any Ca2+ dependence. More detailed experiments showed that Ca2+ was replaceable by the lysosomotropic agent chloroquine. Furthermore, it was possible to separate the transfection-enhancing role of Ca2+ from the actual transfection process by adding Ca2+ to the cells after the transfection period and still to obtain a significant transgene expression. This makes it possible to distinguish between cellular uptake of H1 (or mediator)-DNA complexes and endocytotic release. We also replaced soluble Ca2+ by Ca-phosphate precipitates not containing DNA and obtained similar transfection results. This allowed us to suggest that the addition of free Ca2+ to the transfection medium resulted in nascent Ca-phosphate microprecipitates. The known fusogenic and membranolytic activity of such microprecipitates could facilitate the transport through and the release of the transfecting complexes from the endosomal/lysosomal compartment.

Non-viral neuronal gene delivery mediated by the HC fragment of tetanus toxin

Many inherited neurological diseases and cancers could potentially benefit from efficient targeted gene delivery to neurons of the central nervous system. The nontoxic fragment C (HC) of tetanus toxin retains the specific nerve cell binding and transport properties of tetanus holotoxin. The HC fragment has previously been used to promote the uptake of attached proteins such as horseradish peroxidase, beta-galactosidase and superoxide dismutase into neuronal cells in vitro and in vivo. We report the use of purified recombinant HC fragment produced in yeast and covalently bound to polylysine [poly(K)] to enable binding of DNA. We demonstrate that when used to transfect cells, this construct results in nonviral gene delivery and marker gene expression in vitro in N18 RE 105 cells (a neuroblastoma x glioma mouse/rat hybrid cell line) and F98 (a glioma cell line). Transfection was dependent on HC and was neuronal cell type specific. HC may prove a useful targeting ligand for future neuronal gene therapy.

Liposomes enhance delivery and expression of an RGD-oligolysine gene transfer vector in human tracheal cells

Nonviral gene delivery systems consist predominantly of lipoplexes or receptor-targeting and nontargeting polyplexes. We examined integrin-mediated gene delivery using an Arg-Gly-Asp/oligo-L-lysine ([K]16RGD) cyclic peptide and investigated its gene transfer efficiency when associated with a cationic liposome. We demonstrated that human cystic fibrosis and noncystic fibrosis tracheal epithelial cells in culture express integrins that recognise the RGD integrin-binding motif. We found a 10-fold (P < 0.01) increased expression of a luciferase encoding plasmid in these cells when complexing the plasmid to the [K]16RGD peptide as compared with plasmid alone. This increase was specific to the [K]16RGD peptide since neither a [K]16RGE nor a [K]16 peptide gave a comparable increase. Expression was further enhanced 30-fold (P < 0.01) with lipofectamine and the ratio of DNA/peptide/lipofectamine was critical for specificity and expression. Fluorescence and radioactive labelling of the complex showed that the [K]16RGD peptide increased the endocytic uptake of DNA into cells. The cell association of both DNA and peptide increased even further with lipofectamine. Confocal microscopy showed that the [K]16RGD peptide and the DNA internalised together within 30 min and localised to vesicles in the perinuclear region. These results show that an integrin-binding ligand can deliver genetic material to airway cells and that a cationic liposome can enhance the efficacy of this nonviral vector system.

First pass metabolism of ethanol is strikingly influenced by the speed of gastric emptying

BACKGROUND

Ethanol undergoes a first pass metabolism (FPM) in the stomach and liver. Gastric FPM of ethanol primarily depends on the activity of gastric alcohol dehydrogenase (ADH). In addition, the speed of gastric emptying (GE) may modulate both gastric and hepatic FPM of ethanol.

AIMS

To study the effect of modulation of GE on FPM of ethanol in the stomach and liver.

METHODS

Sixteen volunteers (eight men and eight women) received ethanol (0.225 g/kg body weight) orally and intravenously, and the areas under the ethanol concentration time curves were determined to calculate FPM of ethanol. In seven of these subjects, FPM of ethanol was measured after the intravenous administration of 10 mg metoclopramide (MCP) and 20 mg N-butylscopolamine (NBS) in separate experiments to either accelerate or delay GE. GE was monitored sonographically by integration of the antral area of the stomach every five minutes for 90 minutes after oral ethanol intake. In addition, gastric biopsy specimens were taken to determine ADH activity and phenotype, as well as to evaluate gastric histology. Blood was also drawn for ADH genotyping.

RESULTS

GE time was significantly delayed by the administration of NBS as compared with controls (p<0.0001) and as compared with the administration of MCP (p<0.0001). This was associated with a significantly enhanced FPM of ethanol with NBS compared with MCP (p = 0.0004). A significant correlation was noted between GE time and FPM of ethanol (r = 0.43, p = 0.0407). Gastric ADH activity did not significantly correlate with FPM of ethanol.

CONCLUSION

FPM of ethanol is strikingly modulated by the speed of GE. Delayed GE increases the time of exposure of ethanol to gastric ADH and may therefore increase gastric FPM of ethanol. In addition, hepatic FPM of ethanol may also be enhanced as the result of slower absorption of ethanol from the small intestine. Thus a knowledge of GE time is a major prerequisite for studying FPM of ethanol in humans.

Enhanced in vitro and in vivo gene delivery using cationic agent complexed retrovirus vectors

Retroviruses are, at present, the most efficient integrative vectors available for gene delivery. However, these viruses are still limited by relatively low titres. Although several protocols exist to improve virus titre most of them are time-consuming and unable to provide sufficient virus for in vivo applications. Virus titre can be enhanced by polybrene and other cationic agents. By investigating a broad range of cationic agents for their ability to enhance virus infectivity we found that both ecotropic and amphotropic retrovirus infection could be increased. In particular, the lipopolyamine dioctadecylamidoglycylspermine (DOGS) gave up to one order of magnitude enhancement above polybrene-mediated infection without cytotoxicity. To increase virus infectivity further we combined the enhancing effect of DOGS on virus infectivity with concentration of virus particles by ultrafiltration to reach titres of 1 x 10(9) IU/ml. The in vivo transduction of regenerating rat liver, by an amphotropic retrovirus was increased approximately five-fold by the addition of DOGS compared with virus alone. There was no animal toxicity observed following the administration of DOGS. The improved transduction efficiency seen both in vitro and in vivo following the co-administration of DOGS/virus complexes may be useful for future gene therapy applications.

A cell adhesion peptide from foot-and-mouth disease virus can direct cell targeted delivery of a functional enzyme

The G-H loop of foot-and-mouth disease virus is a disordered protrusion of the VP1 protein exposed on the virion surface. This short stretch includes an arginine-glycine-aspartic acid tripeptide, a recognized integrin-binding motif, which is responsible for cell attachment and infection. Eight copies of a peptide reproducing the amino acid sequence of this FMDV ligand have been displayed in solvent-exposed regions on an enzymatically active recombinant beta-galactosidase. This viral peptide segment enables the chimeric enzyme to bind mammalian cell lines with different efficiencies, probably depending on the number of suitable cell receptors present on each of them. Moreover, it also promotes the internalization of the attached enzyme, which is transiently active inside the cells. These results suggest further exploration of the potential use of short adhesion peptides of viral origin as cell attachment tags to direct the targeted delivery of both genes and enzymes, instead of whole, infectious viruses.