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.