Aerosol delivery of a beta-galactosidase adenoviral vector to the lungs of rodents

Emerging Therapeutic Approaches for Cystic Fibrosis. From Gene Editing to Personalized Medicine

An improved understanding of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) protein structure and the consequences of CFTR gene mutations have allowed the development of novel therapies targeting specific defects underlying CF. Some strategies are mutation specific and have already reached clinical development; some strategies include a read-through of the specific premature termination codons (read-through therapies, nonsense mediated decay pathway inhibitors for Class I mutations); correction of CFTR folding and trafficking to the apical plasma membrane (correctors for Class II mutations); and an increase in the function of CFTR channel (potentiators therapy for Class III mutations and any mutant with a residual function located at the membrane). Other therapies that are in preclinical development are not mutation specific and include gene therapy to edit the genome and stem cell therapy to repair the airway tissue. These strategies that are directed at the basic CF defects are now revolutionizing the treatment for patients and should positively impact their survival rates.

Understanding Gene Therapy in Acute Respiratory Distress Syndrome

Acute Respiratory Distress Syndrome (ARDS) and its complications remain lifethreatening conditions for critically ill patients. The present therapeutic strategies such as prone positioning ventilation strategies, nitric oxide inhalation, restrictive intravenous fluid management, and extracorporeal membrane oxygenation (ECMO) do not contribute much to improving the mortality of ARDS. The advanced understanding of the pathophysiology of acute respiratory distress syndrome suggests that gene-based therapy may be an innovative method for this disease. Many scientists have made beneficial attempts to regulate the immune response genes of ARDS, maintain the normal functions of alveolar epithelial cells and endothelial cells, and inhibit the fibrosis and proliferation of ARDS. Limitations to effective pulmonary gene therapy still exist, including the security of viral vectors and the pulmonary defense mechanisms against inhaled particles. Here, we summarize and review the mechanism of gene therapy for acute respiratory distress syndrome and its application.

Aerosol delivery of DNA/liposomes to the lung for cystic fibrosis gene therapy

Abstract Lung gene therapy is being evaluated for a range of acute and chronic diseases, including cystic fibrosis (CF). As these therapies approach clinical realization, it is becoming increasingly clear that the ability to efficiently deliver gene transfer agents (GTAs) to target cell populations within the lung may prove just as critical as the gene therapy formulation itself in terms of generating positive clinical outcomes. Key to the success of any aerosol gene therapy is the interaction between the GTA and nebulization device. We evaluated the effects of aerosolization on our preferred formulation, plasmid DNA (pDNA) complexed with the cationic liposome GL67A (pDNA/GL67A) using commercially available nebulizer devices. The relatively high viscosity (6.3±0.1 cP) and particulate nature of pDNA/GL67A formulations hindered stable aerosol generation in ultrasonic and vibrating mesh nebulizers but was not problematic in the jet nebulizers tested. Aerosol size characteristics varied significantly between devices, but the AeroEclipse II nebulizer operating at 50 psi generated stable pDNA/GL67A aerosols suitable for delivery to the CF lung (mass median aerodynamic diameter 3.4±0.1 μm). Importantly, biological function of pDNA/GL67A formulations was retained after nebulization, and although aerosol delivery rate was lower than that of other devices (0.17±0.01 ml/min), the breath-actuated AeroEclipse II nebulizer generated aerosol only during the inspiratory phase and as such was more efficient than other devices with 83±3% of generated aerosol available for patient inhalation. On the basis of these results, we have selected the AeroEclipse II nebulizer for the delivery of pDNA/GL67A formulations to the lungs of CF patients as part of phase IIa/b clinical studies.

Clinical review: gene-based therapies for ALI/ARDS: where are we now?

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) confer substantial morbidity and mortality, and have no specific therapy. The accessibility of the distal lung epithelium via the airway route, and the relatively transient nature of ALI/ARDS, suggest that the disease may be amenable to gene-based therapies. Ongoing advances in our understanding of the pathophysiology of ALI/ARDS have revealed multiple therapeutic targets for gene-based approaches. Strategies to enhance or restore lung epithelial and/or endothelial cell function, to strengthen lung defense mechanisms against injury, to speed clearance of infection and to enhance the repair process following ALI/ARDS have all demonstrated promise in preclinical models. Despite three decades of gene therapy research, however, the clinical potential for gene-based approaches to lung diseases including ALI/ARDS remains to be realized. Multiple barriers to effective pulmonary gene therapy exist, including the pulmonary architecture, pulmonary defense mechanisms against inhaled particles, the immunogenicity of viral vectors and the poor transfection efficiency of nonviral delivery methods. Deficits remain in our knowledge regarding the optimal molecular targets for gene-based approaches. Encouragingly, recent progress in overcoming these barriers offers hope for the successful translation of gene-based approaches for ALI/ARDS to the clinical setting.

Gene transfer to the mammalian reproductive tract

This review summarizes the results of research on gene transfer to the mammalian genital tract. Gene transfer experiments have been developed during the last 2 decades and have been applied using in vitro, ex vivo and in vivo procedures. (i) In vitro methods have been applied to the uterine epithelial cells with the principal purpose of analysing some pathological change occurring in the uterus. In the male tract, epididymal cell lines have been used to evaluate the expression of particular genes and the function of specific proteins. (ii) Ex vivo methods have been applied to both the uterus and the vas deferens in humans, and good transgene expression has been recorded. (iii) In vivo gene transfer in the female tract has been employed in the uterus and oviduct using gene injections or electroporation methods. The glandular epithelium of both organs can be transfected efficiently, and transfection efficiency depends on the hormonal stage of the animal. The best expression occurred during pseudopregnancy and meta-estrus periods, when high progesterone and low estradiol concentrations occur. In the male tract, in vivo methods have been applied to mouse vas deferens and epididymis. In both organs, patches of epithelial regions appeared to express the transgenes. Furthermore, the secretions of both organs were also modified using gene constructions that led to the expression of some secretory proteins. In summary, gene modifications in the epithelium of the mammalian reproductive tract have been successful employing different technologies. Further improvements in transfection efficiency would help provide new insights into the physiology of these reproductive organs. Furthermore, the use of these methods could also be used to modify the fertility of mammals.

In-vivo gene transfer induces transgene expression in cells and secretions of the mouse cauda epididymis

Mouse cauda epididymis were in-vivo transfected using the lipid FuGENE 6 as gene vector. Two gene constructions were employed: the p-GeneGRIP which codifies for the Green Fluorescent Protein (GFP) and the pSEAP-control that expresses an alkaline phosphatase as a secretion. Transfection was detected by fluorescence and appeared in the nucleus and cytoplasm of epithelial cells. Transfection was observed in 39.70% of cells after 2 days and in 31.77% after 7 days, and then diminished progressively. Moreover, the presence of the transgene in the DNA isolated from treated epididymides was observed by polymerase chain reaction. GFP gene expression appeared in large areas of the cauda epididymis and it was observed exclusively in the cytoplasm of epithelial cells. GFP gene expression occurred during 2 weeks after gene injection and occupied 32.24, 29.98 and 22.37% of the area of the tubules when analyzed 2, 7 and 15 days after gene injection. The cauda was also analyzed in toto and showed similar results. The use of the pSEAP-control gene showed that cauda epididymis secretions can also be modified by the transfection procedure. A significant increase of alkaline phosphatase activity appeared in the epididymal fluids 7 days after gene injection. These results indicate that transfection procedures could be an important tool in the future to study epididymal physiology or to change the fertilizing ability of spermatozoa.

Gene transfer to the lung: lessons learned from more than 2 decades of CF gene therapy

Gene therapy is currently being developed for a wide range of acute and chronic lung diseases. The target cells, and to a degree the extra and intra-cellular barriers, are disease-specific and over the past decade the gene therapy community has recognized that no one vector is good for all applications, but that the gene transfer agent (GTA) has to be carefully matched to the specific disease target. Gene therapy is particularly attractive for diseases that currently do not have satisfactory treatment options and probably easier for monogenic disorders than for complex diseases. Cystic fibrosis (CF) fulfils these criteria and is, therefore, a good candidate for gene therapy-based treatment. This review will focus on CF as an example for lung gene therapy, but lessons learned may be applicable to other target diseases.

Lung-directed gene therapy in mice using the nonviral Sleeping Beauty transposon system

The Sleeping Beauty (SB) transposon is an integrative nonviral plasmid system. Here, we describe a protocol for SB-mediated transgene delivery using DNA/polyethyleneimine (PEI) complexes for long-term expression in mouse lungs. This protocol can be used for delivery of any plasmid-based vector system to mouse lungs, although long-term transgene expression will be obtained only when using the SB transposon or other integrating vector systems. The stages of this protocol are preparation of DNA-PEI complexes and injection of the complexes into the lateral tail vein of mice. We also provide protocols for assessing transgene expression using in vivo bioluminescence imaging and enzymatic assay of lung homogenates. The procedure can be completed within 24 h, starting from preparation of DNA-PEI complexes to analysis of transient transgene expression.

Bioregulators as prototypic nontraditional threat agents

Bioregulators are naturally occurring organic compounds that regulate a multitude of biologic processes. Under natural circumstances, bioregulators are synthesized in minute quantities in a variety of living organisms and are essential for physiologic homeostasis. In the wrong hands, these compounds have the capability to be used as nontraditional threat agents that are covered by the prohibitions of the Chemical Weapons Convention and the Biological and Toxin Weapons Convention. Unlike traditional biowarfare/bioterrorism agents that have a latency period of hours to days,the onset of action of bioregulators may occur within minutes after host exposure. Concerns regarding the potential misuse of bioregulators for nefarious purposes relate to the ability of these nontraditional agents to induce profound physiologic effects.

The therapeutic potential of the human cystic fibrosis transmembrane conductance regulator gene

The cloning of the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR), mutations of which are responsible for the clinical onset of cystic fibrosis (CF), along with progress in understanding the interplay between CFTR functions and the CF cellular phenotype have prompted many investigators to explore the therapeutic potential of CFTR gene delivery to airway cells in CF patients. In the last four years, a large number of Phase I clinical trials have been started. The results from the very first trials, although mixed, showed that it was possible to transfer and express the CFTR gene, and in certain cases restore the functional electrophysiological properties of the diseased CF cells. These initial trials have been fundamental in encouraging more basic research on vector design to improve the safety and efficiency of persistent CFTR gene transfer, and to introduce novel ways of administration and new techniques to assess the potential therapeutic efficacy of functional gene expression. New Phase I clinical trials based on novel protocol design were therefore initiated.

Intraoviductal introduction of plasmid DNA and subsequent electroporation for efficient in vivo gene transfer to murine oviductal epithelium

Various growth factors and proteins produced by oviductal cells have been demonstrated to interact with developing embryos. However, little is known concerning the function of mammalian oviducts at the molecular biological level. This may be partly due to lack of efficient gene transfer to oviductal cells. In this study, we developed an efficient method for transfection of oviductal epithelium using in vivo electroporation (EP) in mice. One microliter of solution containing enhanced green fluorescent protein (EGFP) expression plasmid (0.5 microg) and 0.05% trypan blue (TB) were directly introduced into the ampulla of the eCG-hCG-treated B6C3F1 females at embryonic day (E) 0.6 of pregnancy (corresponding to 14:00-15:00 of the day the plug was recognized). The entire oviduct was then electroporated using tweezer-type electrodes attached to a T820 electroporator (BTX Genetronics, Inc., San Diego, CA) with eight square-wave pulses, 50 V in strength and 50 msec in duration. On E 3.4, embryos at morula/early blastocyst stages were collected and their number, morphology, and EGFP-derived fluorescence recorded. Fluorescence in oviducts was also examined. In some cases, these fluorescent oviducts were subjected to cryostat sectioning. Strong fluorescence was observed in some of the oviductal epithelia, with a maximum level of 36%. Neither the number nor morphology of the collected embryos was affected by EP. Some embryos possessed fluorescence in the blastocoel, but not cytoplasm, suggesting incorporation of EGFP present in the oviductal luminal fluid. This system may enable development of new factors regulating development of preimplantation embryos and offers the prospect of a new approach to understanding oviductal function.

A miniaturized nebulization catheter for improved gene delivery to the mouse lung

BACKGROUND

The available methods for administration of gene delivery systems to the lungs of small animals via nebulization have several drawbacks. These include lack of control over the delivered dose and a negative impact on the stability of the formulation. This paper describes a new nebulization catheter device for the administration of plasmid-based gene delivery systems (polyplexes) as aerosols to the mouse lung in vivo.

METHODS

The physical stability of naked pDNA and polyplexes formulated with chitosan oligomers and PEI was examined following nebulization with the catheter device. We also examined the in vitro transfection efficiency of the polyplexes recovered after nebulization. Lung distribution and gene expression after administration of the selected gene delivery systems to the mouse lung were also investigated.

RESULTS

In contrast to previously described nebulization methods, the structural integrity of the unprotected naked pDNA was maintained following nebulization by the catheter device, which indicates relatively mild nebulization conditions. In addition, the nebulization procedure did not affect the physical stability of the formulated polyplexes. Small volumes of the pDNA aerosol (10-20 microl) were delivered in a highly controlled and reproducible manner. The aerosol droplet size varied with the molecular weight of the polycations. Aerosol delivery via this method resulted in improved lung distribution of pDNA polyplexes and a six-fold increase in the efficiency of gene delivery in vivo over that seen with the commonly used intratracheal instillation method.

CONCLUSION

The use of the nebulization catheter device provides a promising alternative for aerosol gene delivery to the mouse lung.

Gene therapy for cystic fibrosis: an example for lung gene therapy

Gene therapy is currently being evaluated for a wide range of acute and chronic lung diseases. The requirement of gene transfer into the individual cell types of the complex lung structure will very much depend on the target disease. Over the last decade, the gene therapy community has recognized that there is not even one vector that is good for all applications, but that the gene transfer agent has to be carefully chosen. Gene therapy is particularly attractive for diseases that currently do not have satisfactory treatment options and probably easier for monogenic disorders than for complex diseases. Cystic fibrosis (CF) fulfills these criteria and is therefore a good candidate for gene therapy-based treatment. This review will focus on CF as an example for lung gene therapy and discuss the progress made in this field over the last couple of years.

In vitro transfection of the human vas deferens using DNA-liposome and DNA-neutral lipid complexes

OBJECTIVE

To transfect the human vas deferens in vitro.

DESIGN

Prospective study, description of a procedure.

SETTING

Research center and university hospital.

PATIENT(S)

Seven fertile men undergoing vasectomies or vasovasostomies.

INTERVENTION(S)

Human vas deferens pieces were transfected in vitro using the p-GeneGrip gene construction, which codifies for the green fluorescent protein (GFP). Lipofectamine or GenePorter were employed as gene vectors.

MAIN OUTCOME MEASURE(S)

After vas deferens epithelium transfection, we described the vas deferens foreign gene expression. Maximum transfection occurred in 14.7% of the vas deferens epithelial cells. After using GenePorter, we observed green fluorescent protein gene expression in 40% of samples, which occupied 9.86% of the epithelial area. After Lipofectamine treatment, transgene expression occurred in 33% of the samples and occupied 9.05% of the epithelial area.

CONCLUSION(S)

The human vas deferens epithelium has the potential to be modified by gene transfection.

Reduced inflammation and improved airway expression using helper-dependent adenoviral vectors with a K18 promoter

Efforts have been made to deliver transgenes to the airway epithelia of laboratory animals and humans to develop gene therapy for cystic fibrosis. These investigations have been disappointing due to combinations of transient and low-level gene expression, acute toxicity, and inflammation. We have developed new helper-dependent adenoviral vectors to deliver an epithelial cell-specific keratin 18 expression cassette driving the beta-galactosidase (beta-gal) or human alpha-fetoprotein (AFP) reporter genes. Following intranasal administration to mice, we found that the reporter genes were widely expressed in airway epithelial and submucosal cells, and secreted human AFP was also detectable in serum. In contrast to a first-generation adenoviral vector, inflammation was negligible at doses providing efficient transduction, and expression lasted longer than typically reported-up to 28 days with beta-gal and up to 15 weeks with human AFP. These results suggest that delivery to the airway of helper-dependent adenoviral vectors utilizing a tissue-specific promoter could be a significant advance in the development of gene therapy for cystic fibrosis.

Aerosol gene therapy

Gene therapy is a novel field of medicine that holds tremendous therapeutic potential for a variety of human diseases. Targeting of therapeutic gene delivery vectors to the lungs can be beneficial for treatment of various pulmonary diseases such as lung cancer, cystic fibrosis, pulmonary hypertension, alpha-1 antitrypsin deficiency, and asthma. Inhalation therapy using formulations delivered as aerosols targets the lungs through the pulmonary airways. The instant access and the high ratio of the drug deposited within the lungs noninvasively are the major advantages of aerosol delivery over other routes of administration. Delivery of gene formulations via aerosols is a relatively new field, which is less than a decade old. However, in this short period of time significant developments in aerosol delivery systems and vectors have resulted in major advances toward potential applications for various pulmonary diseases. This article will review these advances and the potential future applications of aerosol gene therapy technology.

Pharmaceutical and biotechnological aerosols for cystic fibrosis therapy

This review addresses different aerosol therapies used to treat the underlying cause and symptoms of cystic fibrosis (CF) during the past two decades. A summary of the current methods of aerosol delivery and suggestions that may improve the efficacy of the current treatments are provided.

In vivo transfection of the mouse vas deferens

To explore the possibility that specific characteristics of the epithelium of the male tract can be modified, transfections of the mouse vas deferens have been performed using in vivo injections of cationic DNA/liposome complexes. Gene transfer was done employing the reporter genes pEGFP-C1 encoding Green Fluorescent Protein (GFP) and pCMV-nls-beta encoding the nuclear beta-Galactosidase (beta-Gal). Foreign gene expression reached a maximum of 6.8% in the epithelial cells of the vas after treatment with the nuclear beta-Gal gene construction and of 13.3% after employing the GFP gene construction. Expression of the GFP gene appeared from one week up to three months following injection, and it appeared as patches of modified cells along the epithelium. Results from immunocytochemistry and Western Blotting support the conclusion that transfection of epithelial cells was achieved. We have also transfected the vas using gene constructions that express secretory proteins--specifically, the reporter system pSEAP-control that expresses a secretory form of human placental alkaline phosphatase, and the pGFP-Ctk-37 that expresses a secretion form of GFP. In both cases, the fluids expressed from the transfected vas showed a significant increase of alkaline phosphatase activity after pSEAP transfection and the presence of GFP protein when pGFP-Ctk-37 gene construction was employed. Our results indicate that the vas can be transfected in vivo using liposomes as vectors of foreign genes and that the vas fluid contents can be modified.

Comparison of surfactant and perfluorochemical liquid enhanced adenovirus-mediated gene transfer in normal rat lung

Both surfactant- and perfluorochemical (PFC)-based vehicles enhance adenovirus-mediated gene transfer in the lung. To compare the relative effects of surfactant and PFC liquid, we infected orotracheally intubated Sprague-Dawley rats with 4 x 10(9) pfu of an E1a(-)/E3(-) adenovirus expressing either an Escherichia coli lacZ (AdlacZ) mini-gene or no cDNA (Adnull). Surfactant-mediated delivery was achieved via instillation of four, 200-microl aliquots of virus suspended in a 50% surfactant (Survanta) vehicle over a 15-minute period. PFC rats received virus in 100 microl of saline followed by instillation of the PFC liquid FC-75 (10 cc/kg body weight) over a 2- to 3- minute period. Lungs were collected 3 days later for measurement of beta-galactosidase (beta-gal) expression and indices of inflammation. Both PFC liquid and surfactant-based vehicles produced widespread beta-gal expression and increased total beta-gal activity over that observed with instillation of vector alone. Both vehicles comparably increased bronchoalveolar lavage fluid (BALF), total cell counts, neutrophils, total protein, and IFN(gamma). FC-75 was also associated with increased BALF IL1beta. In conclusion, surfactant and FC-75 are similarly effective vehicles for adenovirus-mediated gene transfer to the lung.

Use of Perfluorochemical Liquid Allows Earlier Detection of Gene Expression and Use of Less Vector in Normal Lung and Enhances Gene Expression in Acutely Injured Lung

One of the obstacles to successful lung gene transfer is effective delivery of vector to lung, particularly injured or diseased lung. We have previously demonstrated that intratracheal instillation of perfluorochemical (PFC) liquids along with instillation of recombinant adenovirus and adeno-associated virus vectors, or with cationic liposome vectors, increased total lung gene expression and enhanced distribution of gene expression throughout the lung. To further explore the potential benefits of PFC liquid use, we evaluated the effect of PFC liquid instillation on several other aspects of adenovirus-mediated gene expression in lung. Use of PFC liquid resulted in earlier detection of gene expression and allowed the use of less vector to achieve expression comparable to that observed with the use of higher amounts of vector alone. Using PFC liquid also enhanced gene expression in a rodent model of acute lung injury. PFC liquid did cause a transient inflammation when instilled into normal lungs but did not cause any additional inflammation when instilled alone or with adenovirus vector into acutely injured lungs. Thus, PFC liquid may be a useful adjunct for clinical lung gene transfer, particularly for injured or diseased lungs.

Closed-circuit organ perfusion technique for gene transfer into the lungs. An experimental trial on farm pigs

In an attempt to develop gene therapy for lung diseases, we have explored a closed-circuit surgical perfusion method for gene transfer into the lung. For gene transfer we used a replication defective type 5 adenovirus carrying the E. coli beta-galactosidase gene as a reporter gene. The middle lobe of the right lung of eight young farm pigs was perfused in vivo via thoracotomy for up to 60 min with the viral solution. The gene transfer was performed using a closed-circuit organ perfusion method in vivo. The efficiency of gene transfer was assessed visually by analysis of histologic sections after X-gal, PAS and immunohistochemical stainings. The lung perfusion resulted in transgene expression in the alveolar epithelial cells, capillary endothelial cells, airway epithelial cells and alveolar macrophages of the lung examined seven days after perfusion. The present results suggest that operatively performed closed-circuit warm lung perfusion method may be used for gene transfer in treatment of diseases that have pulmonary manifestations.

Ultrasonic nebulization of cationic lipid-based gene delivery systems for airway administration

PURPOSE

This study relates to the development of gene therapies for the treatment of lung diseases. It describes for the first time the use of ultrasonic nebulization for administration of plasmid/lipid complexes to the lungs to transfect lung epithelial cells.

METHODS

Plasmid complexed to cationic liposomes at a specific stoichiometric ratio was nebulized using an ultrasonic nebulizer. We assessed: (i) the stability of plasmid and plasmid/lipid complexes to ultrasonic nebulization, (ii) the in vitro activity of plasmid in previously nebulized plasmid/lipid complex, (iii) the in vivo transgene expression in lungs following intratracheal instillation of nebulized plasmid/lipid formulations compared to un-nebulized complexes, (iv) the emitted dose from an ultrasonic nebulizer using plasmid/lipid complexes of different size, and (v) the transgene expression in lungs following oral inhalation of aerosolized plasmid/lipid complex generated using an ultrasonic nebulizer.

RESULTS

Integrity of plasmid formulated with cationic lipids, and colloidal stability of the plasmid/lipid complex were maintained during nebulization. In contrast, plasmid alone formulated in 10% lactose was fragmented during nebulization. The efficiency of transfection of the complex before and after nebulization was comparable. Nebulization produced respirable aerosol particles. Oral exposure of rodents for 10 minutes to aerosol produced from the ultrasonic nebulizer resulted in transgene expression in lungs in vivo.

CONCLUSIONS

The performance characteristics of the ultrasonic nebulizer with our optimized plasmid/lipid formulations suggests that this device can potentially be used for administering gene medicines to the airways in clinical settings for the treatment of respiratory disorders.

Effective treatment of early endobronchial cancer with regional administration of liposome-p53 complexes

BACKGROUND

Lung cancer originates in a diffusely damaged bronchial epithelium as a result of sequential and cumulative genetic alterations. We investigated the feasibility of in vivo gene replacement in endobronchial precancerous and cancerous cells by a regionally administered nonviral delivery system.

METHODS

After evaluating the in vitro transfection efficiency and cytotoxicity of a variety of cationic liposome-p53 formulations, a specific formulation, DP3-p53, was selected for further in vitro and in vivo evaluation. The ability of DP3-p53 to introduce the p53 gene in the normal bronchial epithelium was studied in transgenic mice that lack the p53 gene. The therapeutic effect of DP3-p53 administered intratracheally was studied in two nude mouse models of endobronchial human lung cancer by use of H358 (p53-null) and H322 (p53-mutant) cells.

RESULTS

DP3-p53 was able to effectively introduce and express the p53 gene and induce G1 arrest and apoptosis in H358 cells in vitro and to introduce and transcribe the p53 gene in the bronchial epithelium of transgenic mice that lack the p53 gene in vivo. In therapeutic experiments using groups of four or five mice each, administration of five intratracheal doses of DP3-p53 (2 microg or 8 microg DNA per dose) on days 4, 8, 12, 16, and 20 after intratracheal tumor inoculation significantly inhibited lung tumor formation and prolonged by approximately twofold the survival of mice bearing H358 or H322 endobronchial tumor cells in contrast to the survival among untreated mice and mice treated with the DP3-empty vector (P = .007 [two-sided logrank test] for mice bearing H358 cells and P = .008 [two-sided logrank test] for those bearing H322 cells).

CONCLUSIONS/IMPLICATIONS

Liposome-based p53 delivery through the airways is a potentially effective strategy for the treatment of early endobronchial cancer. These results have important implications for the gene therapy and prevention of human lung cancer.

Gene therapy for oxidant injury-related diseases: adenovirus-mediated transfer of superoxide dismutase and catalase cDNAs protects against hyperoxia but not against ischemia-reperfusion lung injury

Hyperoxia and ischemia-reperfusion cause profound lung cellular damage mediated, in part, by generation of oxygen radicals. We hypothesized that gene therapy can be used to overcome oxidant injury by augmenting intracellular antioxidant enzymes. Adult rats were injected intratracheally with an adenovirus (Ad) vector encoding human superoxide dismutase (CuZn-SOD) or catalase cDNA, a mixture of both Ad vectors, or a control Ad vector containing no exogenous gene. Expression of human catalase and CuZn-SOD was demonstrated 3 days later in distal lung epithelial cells and alveolar macrophages, using ELISA and immunochemistry. After exposure to 100% O2 for 62 hr, survival was greater in rats injected with the catalase and/or SOD Ad vectors than in control rats. Ischemia-reperfusion injury was evaluated in the isolated perfused lung model. Overexpression of SOD worsened ischemia-reperfusion injury. Interestingly, concomitant overexpression of catalase prevented this adverse effect, but did not protect against ischemia-reperfusion injury. We conclude that Ad-mediated transfer to lungs of both catalase and SOD cDNAs protects from pulmonary O2 toxicity. Absence of protection against ischemia-reperfusion using intratracheal Ad injections may be related to the lack of endothelial protection, despite epithelial expression of catalase and SOD.

Successful gene transfer to the porcine liver in vivo with an adenoviral vector

In vivo gene transfer to the porcine liver was tested with adenoviral vector to achieve molecular biological graft modulation. In adult female pigs immunosuppressed with cyclophosphamide, cyclosporine, and prednisolone, the liver was surgically isolated and flushed out with cold lactate Ringer solution (4 degrees C), by means of a pump-controlled bypass of the portal vein and the inferior vena cava in Groups A and D. In Group A (n = 4), 2 x 1011 pfu of the adenoviral vectors (pAdexCALacZ) were injected through the left hepatic artery during cold ischemia. In Group (n = 4), 2 x 1011 pfu of adenovirus vectors were injected through the auricular vein in a one-shot manner without a laparotomy. In Group C (n = 4), 2 x 1011 pfu/ml of adenoviral vectors were injected through the hepatic artery in a one-shot manner, without a surgical isolation of the liver. Group D (n = 4) animals received the same protocol as Group A except for the fact that they did not receive the immunosuppressive regimen. In a polymerase chain reaction, a transfected LacZ sequence was detected until POD 28 in Group A, but not in the other groups. In 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside (X-gal) staining, only the Group A animals revealed apparent staining predominantly in the portal area at POD 2, which then continued to be recognized until POD 28. The in situ perfusion of the liver combined with immunosuppression is thought to provide an ideal environment for the liver-directed adenovirus-mediated gene transfer to the porcine liver, by enabling a long contact with a high titer of the adenoviral vector.

Recombinant adenovirus-mediated gene transfer into the adult rat retina

PURPOSE

The present study was designed to evaluate the feasibility of gene transfer into the retina of adult rats, using a recombinant replication-defective adenovirus vector expressing a reporter gene.

METHODS

Purified recombinant adenovirus expressing beta-galactosidase (lacZ) (Ad5.hCMV.lacZ) at doses ranging from 1.4 x 10(2) to 1.4 x 10(6) plaque-forming units (pfu) were injected into the subretinal space of adult Lewis rats. The presence of lacZ was determined by histochemical assay and reverse transcription and polymerase chain reaction analysis (RT PCR) of total RNA extracted from eyes injected with recombinant adenovirus expressing lacZ.

RESULTS

As assessed by biomicroscopy, the expression of lacZ was highest in the retinal pigment epithelium in a localized area corresponding to the site of injection. The level of lacZ expression was correlated with the amount of virus delivered to the subretinal space. Persistent but decreasing expression of lacZ was noted over time. RT PCR revealed the expression of messenger RNA for at least sixty days.

CONCLUSIONS

The results of this study demonstrate that efficient and stable transfer of genetic material into the subretinal space of adult rats may be achieved using a recombinant adenoviral vector. The use of such vectors should prove useful in developing novel applications and approaches to the study of recombinant protein expression in vivo.

Evaluation of gene therapy for citrullinaemia using murine and bovine models

Citrullinaemia is an autosomal recessive disorder caused by the deficiency of argininosuccinate synthase. The deficiency of this enzyme results in an interruption in the urea cycle and the inability to dispose of excess ammonia derived from the metabolism of protein. The only treatment for this disorder has been dietary restriction of protein and supplementation with medications allowing for alternative excretion of excess nitrogen. Gene therapy offers the possibility of a long-term cure for disorders like citrullinaemia by expressing the deficient gene in the target organ. We have explored the use of adenoviral vectors as a treatment modality for citrullinaemia in two animal models, a naturally occurring bovine model and a murine model created by molecular mutagenesis. Mice treated with adenoviral vectors expressing argininosuccinate synthase lived significantly longer than untreated animals (11 days vs 1 day; however, the animals did not exhibit normal weight gain during the experiment, indicating that the therapeutic effectiveness of the transducing virus was suboptimal. It is speculated that part of the failure to observe better clinical outcome might be due to the deficiency of arginine. In the bovine model, the use of adenoviral vectors did not result in any change in the clinical condition of the animals or in the level of plasma ammonia. However, the use of 15N isotopic ammonia allowed us to assess the flux of nitrogen through the urea cycle during the experiment. These studies revealed a significant increase in the flux through the urea cycle following administration of adenoviral vectors expressing argininosuccinate synthase. We conclude that the use of adenoviral vectors in the treatment of citrullinaemia is a viable approach to therapy but that it will be necessary to increase the level of transduction and to increase the level of enzyme produced from the recombinant viral vector. Future experiments will be designed to address these issues.

Enhanced distribution of adenovirus-mediated gene transfer to lung parenchyma by perfluorochemical liquid

Although gene therapy holds great promise for the treatment of inherited and acquired diseases of the lung, a number of issues including efficient delivery and distribution of genes to pulmonary target cells must still be addressed. In this study we evaluated the use of perfluorochemical (PFC) liquid as a vehicle for delivery of recombinant adenovirus (AdCBlacZ) to lungs of juvenile rabbits. Virus was instilled into trachea of rabbits, and 4 days later the lungs were removed, cut into multiple pieces, and assayed for beta-galactosidase (beta-Gal) activity. Total lung expression of the beta-Gal reporter gene was increased two- to three-fold by instillation of the virus (10(11) particles/kg body weight) in saline (1.5 ml/kg) simultaneously with perflubron liquid (15 ml/kg) compared to virus+saline alone (control). Uniformity of beta-Gal activity between lobes was significantly improved by the PFC liquid. In perflubron-treated lungs approximately 45% of the lung pieces had beta-Gal-specific activity values within 50-150% of the mean specific activity for the total lung, compared to only approximately 15% of the pieces in control lungs. More of total lobar beta-Gal activity was recovered in the distal lung tissue (approximately two-fold greater than controls, p < 0.05). Morphological assessment of X-Gal-stained, fresh-frozen lung sections showed increased levels and more complete staining of alveolar wall cells in the PFC group. These data indicate that the PFC liquid perflubron enhances distribution of virus-mediated gene expression to the lung parenchyma in healthy rabbits. PFC liquid may be a useful treatment vehicle for accessing distal spaces of the damaged or diseased lung.

Safety of airway gene transfer with Ad2/CFTR2: aerosol administration in the nonhuman primate

In this study, the safety and efficacy of aerosol delivery to non-human primates of an adenoviral vector encoding the cystic fibrosis transmembrane conductance regulator protein (CFTR) were evaluated. The technique of concurrent flow spirometry was used to determine the deposited dose of Ad2/CFTR-2, which ranged from 3 to 8 x 10(10) I.U. Transgene DNA was detected by the polymerase chain reaction (PCR) in lung tissue from all treated animals, and human CFTR mRNA was detected on days 3, 7, and 21 post-exposure. The treatment was well tolerated, with no evidence of respiratory distress. Histologic changes in the lungs from Ad2/CFTR-2-treated animals were mild and, overall, indistinguishable from animals exposed to aerosolized vehicle. One vector-treated animal demonstrated an increase in lavage lymphocyte numbers 3 days after treatment and another had an abnormal chest radiograph 14 days after treatment. A third vector-treated animal had histologic evidence of a bronchointerstitial pneumonia 7 days after aerosol treatment that resolved by day 21. This study demonstrated that Ad2/CFTR-2 can effectively be delivered to the lungs of nonhuman primates and result in minimal adverse effects.

Exogenous surfactant enhances the delivery of recombinant adenoviral vectors to the lung

Somatic gene therapy for pulmonary diseases must be accomplished in vivo, requiring the spread of a gene transfer vector across a vast expanse of respiratory epithelium. Surfactant, a naturally occurring protein and lipid mixture used to treat the respiratory distress syndrome of prematurity, disperses rapidly and evenly throughout the lung. We employed exogenous bovine surfactant (Survanta beractant) as a carrier vehicle for pulmonary delivery of a recombinant adenovirus expressing beta-galactosidase (beta-Gal). Rats treated with an adenovirus-beractant mixture demonstrated more uniform lobar distribution of transgene expression than rats treated with the same amount of virus in saline. Tissue homogenates were examined for quantitative beta-Gal expression by reaction with o-nitrophenol beta-n-galactopyranoside (ONPG). The degree of beta-Gal activity was affected by both the volume and type of carrier used to deliver the virus. At low volumes (0.5 ml, 1.3 ml/kg), beractant-treated animals demonstrated significantly greater pulmonary beta-Gal activity than saline-treated animals (p < 0.002) and untreated controls. At high volume (1.2 ml, 4 ml/kg), average beta-Gal activity was similar between groups treated with beractant or saline, but was more variable within the saline treated group. Higher volumes of delivery medium were associated with increased levels of beta-Gal expression regardless of the carrier used. Survanta was well tolerated by the animals and did not affect the duration of transgene expression. Exogenous beractant provides a useful medium for delivering recombinant adenoviruses to the lung when diffuse distribution of transgene expression is desired.

Characterization of factors involved in modulating persistence of transgene expression from recombinant adenovirus in the mouse lung

One potential limitation of adenovirus (Ad)-based vectors for the gene therapy of cystic fibrosis (CF) and other genetic diseases is the transience of expression observed in most in vivo systems. In this study, the influence of various factors on persistence of transgene expression in the lung was investigated. In the absence of immune pressure, such as in the nude mouse, the genomic structure of the vector was found to be predominant in determining the persistence of expression; Ad vector constructs with an E1-E3+E4ORF6+ backbone encoding beta-galactosidase (beta-Gal) or the cystic fibrosis transmembrane conductance regulator (CFTR) produced declining levels of expression while an Ad/CMV beta Gal vector with an E1-E3+E4+ backbone gave rise to sustained, long-term reporter gene expression. The ability of the latter vector to persist was in turn limited in part by the presence of cytotoxic T lymphocytes (CTLs). Adoptive transfer experiments indicated that CTLs directed against either viral proteins or the beta-Gal reporter gene product were able to reduce expression in nude C57BL/6 mice stably expressing beta-Gal from the E4+ vector. Finally, the specificity and strength of the CTL response elicited by Ad vector was found to vary considerably depending on mouse strain haplotype. These results indicate that persistence of transgene expression in a given system is determined by the interplay between several factors including genomic structure of the vector, host background, and immune response.

Efficient adenovirus-mediated gene transfer to basal but not columnar cells of cartilaginous airway epithelia

Adenoviral vectors (AdV) developed for treatment of the pulmonary manifestations of cystic fibrosis (CF) can deliver, with high efficiency, transgenes to respiratory epithelial cells grown in culture. This study investigated the efficiency of AdV-mediated gene transfer to murine and human respiratory epithelium in vivo and concluded that the epithelial cells facing the lumen of the respiratory cartilaginous airways (columnar cells) are poorly transduced with AdV. Mechanical injury to the epithelium, however, leads to efficient in vivo gene transfer by exposing a susceptible epithelial subtype (basal cells). Increased gene transfer efficiency in vivo after injury is not a nonspecific response because the proliferative status of the epithelium after injury was shown not to correlate temporally to the increased transduction susceptibility of the epithelium. Although basal cells were the cell type transduced at the time of vector delivery, with time, basal cell differentiation to columnar cells occurred with maintenance of transgene expression. Collectively, these results show that murine and human cartilaginous airways are poorly transduced by AdV. To correct the cartilaginous airway CF bioelectrical defect in vivo, efforts should be directed to increase the tropism of AdV to the columnar airway epithelial cells.