Safety and efficacy of repetitive adenovirus-mediated transfer of CFTR cDNA to airway epithelia of primates and cotton rats

Gene therapy for cystic fibrosis: new tools for precision medicine

The discovery of the Cystic fibrosis (CF) gene in 1989 has paved the way for incredible progress in treating the disease such that the mean survival age of individuals living with CF is now ~58 years in Canada. Recent developments in gene targeting tools and new cell and animal models have re-ignited the search for a permanent genetic cure for all CF. In this review, we highlight some of the more recent gene therapy approaches as well as new models that will provide insight into personalized therapies for CF.

New Therapeutic Approaches in Cystic Fibrosis

Cystic fibrosis (CF) is a hereditary, multisystemic disease caused by different mutations in the CFTR gene encoding CF transmembrane conductance regulator. CF is mainly characterized by pulmonary dysfunction as a result of deterioration in the mucociliary clearance and anion transport of airways. Mortality is mostly caused by bronchiectasis, bronchiole obstruction, and progressive respiratory dysfunction in the early years of life. Over the last decade, new therapeutic strategies rather than symptomatic treatment have been proposed, such as the small molecule approach, ion channel therapy, and pulmonary gene therapy. Due to considerable progress in the treatment options, CF has become an adult disease rather than a pediatric disease in recent years. Pulmonary gene therapy has gained special attention due to its mutation type independent aspect, therefore being applicable to all CF patients. On the other hand, the major obstacle for CF treatment is to predict the drug response of patients due to genetic complexity and heterogeneity. The advancement of 3D culture systems has made it possible to extrapolate the disease modeling and individual drug response in vitro by producing mini adult organs called "organoids" obtained from rectal cell biopsies. In this review, we summarize the advances in the novel therapeutic approaches, clinical interventions, and precision medicine concept for CF.

Adenovirus vector-mediated YKL-40 shRNA attenuates eosinophil airway inflammation in a murine asthmatic model

Recent studies have revealed that YKL-40 is involved in the pathogenesis of asthma. However, its specific mechanism remains unclear. The present study aims to investigate the effect of adenovirus vector-mediated YKL-40 short hairpin RNA (shRNA) on regulation of airway inflammation in a murine asthmatic model. Mice were assessed for airway hyperresponsiveness (AHR), total leukocytes and the percentage of eosinophil cells in bronchoalveolar lavage fluid (BALF). YKL-40 mRNA and protein expression levels were detected using quantitative real-time PCR and western blot assays. Enzyme-linked immunosorbent assay (ELISA) was used to detect YKL-40 and eosinophil-related chemokine expression levels in BALF and serum. Lung histology analyses were performed to evaluate the degree of inflammatory cell infiltration around the airway and airway mucus secretion.YKL-40 shRNA significantly inhibited the YKL-40 gene expression in asthmatic mice. In addition, YKL-40 shRNA alleviated eosinophilic airway inflammation, AHR, airway mucus secretion and decreased the levels of YKL-40 in BALF and serum in a murine asthmatic model. The levels and mRNA expression of IL-5, IL-13 in asthmatic mice lung tissues, eotaxin, and GM-CSF in BALF and serum significantly decreased. Bone marrow signaling molecules including IL-5, eotaxin, and GM-CSF were correlated with decreased levels of YKL-40. The study reveals that YKL-40 could be involved in asthma inflammation by altering bone marrow signaling molecules. YKL-40 gene RNA interference could provide new therapeutic strategies for asthma.

Cystic Fibrosis Gene Therapy: Looking Back, Looking Forward

Cystic fibrosis (CF) is an autosomal recessive disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene that encodes a cAMP-regulated anion channel. Although CF is a multi-organ system disease, most people with CF die of progressive lung disease that begins early in childhood and is characterized by chronic bacterial infection and inflammation. Nearly 90% of people with CF have at least one copy of the ΔF508 mutation, but there are hundreds of CFTR mutations that result in a range of disease severities. A CFTR gene replacement approach would be efficacious regardless of the disease-causing mutation. After the discovery of the CFTR gene in 1989, the in vitro proof-of-concept for gene therapy for CF was quickly established in 1990. In 1993, the first of many gene therapy clinical trials attempted to rescue the CF defect in airway epithelia. Despite the initial enthusiasm, there is still no FDA-approved gene therapy for CF. Here we discuss the history of CF gene therapy, from the discovery of the CFTR gene to current state-of-the-art gene delivery vector designs. While implementation of CF gene therapy has proven more challenging than initially envisioned; thanks to continued innovation, it may yet become a reality.

Genetic Modification of the Lung Directed Toward Treatment of Human Disease

Genetic modification therapy is a promising therapeutic strategy for many diseases of the lung intractable to other treatments. Lung gene therapy has been the subject of numerous preclinical animal experiments and human clinical trials, for targets including genetic diseases such as cystic fibrosis and α1-antitrypsin deficiency, complex disorders such as asthma, allergy, and lung cancer, infections such as respiratory syncytial virus (RSV) and Pseudomonas, as well as pulmonary arterial hypertension, transplant rejection, and lung injury. A variety of viral and non-viral vectors have been employed to overcome the many physical barriers to gene transfer imposed by lung anatomy and natural defenses. Beyond the treatment of lung diseases, the lung has the potential to be used as a metabolic factory for generating proteins for delivery to the circulation for treatment of systemic diseases. Although much has been learned through a myriad of experiments about the development of genetic modification of the lung, more work is still needed to improve the delivery vehicles and to overcome challenges such as entry barriers, persistent expression, specific cell targeting, and circumventing host anti-vector responses.

Vascular endothelial growth factor promoter-based conditionally replicative adenoviruses effectively suppress growth of malignant pleural mesothelioma

Malignant mesothelioma (MM) incidence is increasing drastically worldwide as an occupational disease resulting from asbestos exposure. However, no curative treatment for MM of advanced stage is available. Thus, new therapeutic approaches for MM are required. Because malignant pleural mesothelioma (MPM) cells spread along the pleural surface in most patients, MPM can be targeted using intrapleural therapeutic approaches. In this study, we investigated the effectiveness of the intrapleural instillation of a replication‐competent adenovirus as an oncolytic agent against MPM. We constructed a vascular endothelial growth factor promoter‐based conditionally replicative adenovirus (VEGF‐CRAd) that replicates exclusively in VEGF‐expressing cells. All of the MM cell lines that we tested expressed VEGF mRNA, and VEGF‐CRAd selectively replicated in these MM cells and exerted a direct concentration‐dependent oncolytic effect in vitro. Furthermore, our in vivo studies showed that pre‐infection of MM cells with VEGF‐CRAd potently suppressed MPM tumor formation in nude mice, and that intrapleural instillation of VEGF‐CRAd prolonged the survival time of tumor‐bearing mice. Our results indicate that VEGF‐CRAd exerts an oncolytic effect on MM cells and that intrapleural instillation of VEGF‐CRAd is safe and might represent a promising therapeutic strategy for MPM.

Gene delivery to the airway

This unit describes generation of and gene transfer to several commonly used airway models. Isolation and transduction of primary airway epithelial cells are first described. Next, the preparation of polarized airway epithelial monolayers is outlined. Transduction of these polarized cells is also described. Methods are presented for generation of tracheal xenografts, as well as both ex vivo and in vivo gene transfer to these xenografts. Finally, a method for in vivo gene delivery to the lungs of rodents is included. Methods for evaluating transgene expression are given in the support protocols.

Adenoviral gene transfer corrects the ion transport defect in the sinus epithelia of a porcine CF model

Cystic fibrosis (CF) pigs spontaneously develop sinus and lung disease resembling human CF. The CF pig presents a unique opportunity to use gene transfer to test hypotheses to further understand the pathogenesis of CF sinus disease. In this study, we investigated the ion transport defect in the CF sinus and found that CF porcine sinus epithelia lack cyclic AMP (cAMP)-stimulated anion transport. We asked whether we could restore CF transmembrane conductance regulator gene (CFTR) current in the porcine CF sinus epithelia by gene transfer. We quantified CFTR transduction using an adenovirus expressing CFTR and green fluorescent protein (GFP). We found that as little as 7% of transduced cells restored 6% of CFTR current with 17-28% of transduced cells increasing CFTR current to 50% of non-CF levels. We also found that we could overcorrect cAMP-mediated current in non-CF epithelia. Our findings indicate that CF porcine sinus epithelia lack anion transport, and a relatively small number of cells expressing CFTR are required to rescue the ion transport phenotype. These studies support the use of the CF pig as a preclinical model for future gene therapy trials in CF sinusitis.

CD40-targeted adenoviral cancer vaccines: the long and winding road to the clinic

The ability of dendritic cells (DCs) to orchestrate innate and adaptive immune responses has been exploited to develop potent anti-cancer immunotherapies. Recent clinical trials exploring the efficacy of ex vivo modified autologous DC-based vaccines have reported some promising results. However, in vitro generation of autologous DCs for clinical administration, their loading with tumor associated antigens (TAAs) and their activation, is laborious and expensive, and, as a result of inter-individual variability in the personalized vaccines, remains poorly standardized. An attractive alternative approach is to load resident DCs in vivo by targeted delivery of TAAs, using viral vectors and activating them simultaneously. To this end, we have constructed genetically-modified adenoviral (Ad) vectors and bispecific adaptor molecules to retarget Ad vectors encoding TAAs to the CD40 receptor on DCs. Pre-clinical human and murine studies conducted so far have clearly demonstrated the suitability of a 'two-component' (i.e. Ad and adaptor molecule) configuration for targeted modification of DCs in vivo for cancer immunotherapy. This review summarizes recent progress in the development of CD40-targeted Ad-based cancer vaccines and highlights pre-clinical issues in the clinical translation of this approach.

Targeting the Wnt pathway in cancer: the emerging role of Dickkopf-3

Aberrant activation of the Wnt signaling pathway is a major trait of many human cancers. Due to its vast implications in tumorigenesis and progression, the Wnt pathway has attracted considerable attention at several molecular levels, also with respect to developing novel cancer therapeutics. Indeed, research in Wnt biology has recently provided numerous clues, and evidence is accumulating that the secreted Wnt antagonist Dickkopf-related protein 3 (Dkk-3) and its regulators may constitute interesting therapeutic targets in the most important human cancers. Based on the currently available literature, we here review the knowledge on the biological role of Dkk-3 as an antagonist of the Wnt signaling pathway, the involvement of Dkk-3 in several stages of tumor development, the genetic and epigenetic mechanisms disrupting DKK3 gene function in cancerous cells, and the potential clinical value of Dkk-3 expression/DKK3 promoter methylation as a biomarker and molecular target in cancer diseases. In conclusion, Dkk-3 rapidly emerges as a key player in human cancer with auspicious tumor suppressive capacities, most of all affecting apoptosis and proliferation. Its gene expression is frequently downregulated by promoter methylation in almost any solid and hematological tumor entity. Clinically, evidence is accumulating of Dkk-3 being both a potential tumor biomarker and effective anti-cancer agent. Although further research is needed, re-establishing Dkk-3 expression in cancer cells holds promise as novel targeted molecular tumor therapy.

Improvement of adenoviral vector-mediated gene transfer to airway epithelia by folate-modified anionic liposomes

Despite remarkable progress in the development of both viral and nonviral gene delivery vectors for airway disease treatment, poor gene transfer efficiency to the airway epithelium is a major obstacle in clinical application. To take advantage of the unique features of viral and nonviral vectors, we have developed complexes of adenovirus vector and anionic liposomes (AL-Ad5) by the calcium-induced phase change method. In the current study, based on the fact that there are overexpressed folate receptors on the surface of airway epithelia, we further modified the AL-Ad5 complexes with folate (F-AL-Ad5) to improve the transduction ability of Ad5 in airway epithelia. The transduction efficiencies of the obtained F-AL-Ad5 and AL-Ad5 complexes were assessed in primary-cultured airway epithelia in vitro. Our results indicated that compared with naked adenovirus vector, both AL-Ad5 and F-AL-Ad5 could significantly enhance the gene transduction efficiency of adenovirus vector in primary-cultured airway epithelial cells. Moreover, the enhancement mediated by F-AL-Ad5 was more dramatic than that by AL-Ad5. These results suggested that F-AL-Ad5 may be a useful strategy to deliver therapeutic genes to the airway epithelia and is promising in clinical application.

Engineered adenovirus serotypes for overcoming anti-vector immunity

Adenovirus (Ad)-based gene transfer has been successfully utilised in gene therapy and vaccine applications. To date, an increasing number of human clinical trials utilise recombinant Ad-based vectors as a gene transfer platform. In particular, progress has been made recently in utilising Ad-based vectors as a vaccine platform in HIV, cancer immunotherapy approaches and in vaccination for other infections. Despite these successes, the scientific and bio-industrial communities have recently recognised that innate and pre-existing immunity against Ad vectors can constitute a serious obstacle to the development and application of this technology. It is essential to overcome vector-mediated immune responses, such as production of inflammatory cytokines and pre-existing immunity to Ad, because the induction of these responses not only shortens the period of gene expression but also leads to serious side effects. This review focuses on the biology of Ad infection and the approaches that are being adopted to overcome immunity against the Ad-based vectors.

Adenovirus as a carrier for the development of influenza virus-free avian influenza vaccines

A long-sought goal during the battle against avian influenza is to develop a new generation of vaccines capable of mass immunizing humans as well as poultry (the major source of avian influenza for human infections) in a timely manner. Although administration of the currently licensed influenza vaccine is effective in eliciting protective immunity against seasonal influenza, this approach is associated with a number of insurmountable problems for preventing an avian influenza pandemic. Many of the hurdles may be eliminated by developing new avian influenza vaccines that do not require the propagation of an influenza virus during vaccine production. Replication-competent adenovirus-free adenovirus vectors hold promise as a carrier for influenza virus-free avian influenza vaccines owing to their safety profile and rapid manufacture using cultured suspension cells in a serum-free medium. Simple and efficient mass-immunization protocols, including nasal spray for people and automated in ovo vaccination for poultry, convey another advantage for this class of vaccines. In contrast to parenteral injection of adenovirus vector, the potency of adenovirus-vectored nasal vaccine is not appreciably interfered by pre-existing immunity to adenovirus.

Gene therapy for cystic fibrosis

Cystic Fibrosis (CF) is an autosomal recessive disorder due to mutations in the CF transmembrane conductance regulator (CFTR) gene that lead to defective ion transport in the conducting pulmonary airways and exocrine glands. Through a process that is not fully understood, CFTR defects predispose affected patients to chronic endobronchial infections with organisms such as Pseudomonas aeruginosa and Staphylococcus aureus. Following the discovery of the CFTR gene in 1989, CF became one of the primary targets for gene therapy research. Early enthusiasm surrounded the new field of gene therapy during most of the 1990s and it led academics and clinicians on a big effort to apply gene therapy for cystic fibrosis. Clinical studies have been pursued using recombinant adenovirus, recombinant adeno-associated virus, cationic liposomes, and cationic polymer vectors. Although to this date no dramatic therapeutic benefits have been observed, a lot of information has been gained from the pre-clinical and clinical studies that were performed. This learning curve has led to the optimization of vector technology and an appreciation of immune and mechanical barriers that have to be overcome for successful delivery.

Effective repetitive dystrophin gene transfer into skeletal muscle of adult mdx mice using a helper-dependent adenovirus vector expressing the coxsackievirus and adenovirus receptor (CAR) and dystrophin

BACKGROUND

The helper-dependent adenovirus (HDAd) vector is less immunogenic and has a larger cloning capacity of up to 37 kb enough to carry the full-length dystrophin cDNA. However, high and long-term expression of dystrophin transduced to mature muscle still remains difficult. One of the main reasons for this is that the expression of the coxsackievirus and adenovirus receptor (CAR) is very low in mature muscle.

METHODS

We have constructed two different HDAd vectors. One contains the LacZ and the murine full-length dystrophin expression cassette (HDAdLacZ-dys), and the other is a new, improved vector containing the CAR and the dystrophin expression cassette (HDAdCAR-dys).

RESULTS

We initially demonstrated high dystrophin expression and prevention of the dystrophic pathology in mdx muscle injected during the neonatal phase with HDAdLacZ-dys. Furthermore, we demonstrated that repeated injections of HDAdCAR-dys into mature muscle led to approximately nine times greater dystrophin-positive fibers in number than a single injection, thereby recovering the expression of dystrophin-associated proteins. This data has also shown that HDAdCAR-dys enabled administration of adenovirus (Ad) vector to the host with pre-existing immunity to the same serotype of Ad.

CONCLUSIONS

Repetitive injections of the HDAd vector containing the CAR and the dystrophin expression cassette could improve the efficiency of subsequent dystrophin gene transfer to mature mdx muscle. This result suggests that our new HDAd vector will provide a novel gene therapy strategy for Duchenne muscular dystrophy, raising the prospects for gene therapy of other hereditary myopathies.

Readministration of helper-dependent adenovirus to mouse lung

Adenovirus vectors (Ad) are widely used in gene therapy studies, including those aimed at treating cystic fibrosis lung disease. Various approaches have been investigated to blunt the host immune response to Ad, including development of helper-dependent (HD) Ad. The host cytotoxic T-cell response to HD-Ad is generally lower than to earlier-generation Ad. However, antibodies are formed which could inhibit the efficacy of HD-Ad readministration. In this first study of HD-Ad readministration to the lung, we found that a second administration of HD-Ad to mice was possible with minimal loss of transgene expression. In contrast, when first-generation (FG) Ad was administered initially, followed by HD-Ad or FG-Ad, transgene expression was reduced. Significantly lower concentrations of antibodies against Ad were found in lung lavage fluid and serum from mice that received two doses of HD-Ad (when the initial HD-Ad lacked a transgene), compared to mice that received FG-Ad followed by HD-Ad. These data suggest that readministration of HD-Ad for lung gene therapy may be feasible.

Fluorescently tagged canine adenovirus via modification with protein IX-enhanced green fluorescent protein

Canine adenovirus type 2 (CAV2) has become an attractive vector for gene therapy because of its non-pathogenicity and the lack of pre-existing neutralizing antibodies against this virus in the human population. Additionally, this vector has been proposed as a conditionally replicative adenovirus agent under the control of an osteocalcin promoter for evaluation in a syngeneic, immunocompetent canine model with spontaneous osteosarcoma. In this study, a CAV2 vector labelled with the fluorescent capsid fusion protein IX-enhanced green fluorescent protein (pIX-EGFP) was developed. Expression of the fluorescent fusion-protein label in infected cells with proper nuclear localization, and incorporation into virions, could be detected. The labelled virions could be visualized by fluorescence microscopy; this was applicable to the tracking of CAV2 infection, as well as localizing the distribution of the vector in tissues. Expression of pIX-EGFP could be exploited to detect the replication and spread of CAV2. These results indicate that pIX can serve as a platform for incorporation of heterologous proteins in the context of a canine adenovirus xenotype. It is believed that capsid-labelled CAV2 has utility for vector-development studies and for monitoring CAV2-based oncolytic adenovirus replication.

Immune responses to repetitive adenovirus-mediated gene transfer and restoration of gene expression by cyclophosphamide or etoposide

BACKGROUND

One major concern about adenoviral vectors for repetitive gene delivery is the induction of an immune response to the vector, thus impeding effective gene transduction.

METHODS

To assess the immune response to the adenoviral vector, repetitive gene dosing was performed into rhesus monkey cervix and C3H mouse skin using the adenoviral vector carrying the lacZ gene. Three repetitive intracervical injections of adenovirus-lacZ were done in the rhesus monkey at the intervals of 4 weeks. Gene expression on the second and third injection was completely suppressed.

RESULTS

Anti-adenovirus IgG levels and neutralizing antibody titers in the rhesus monkey significantly increased after the first injection of adenovirus. In the C3H mouse, neutralizing antibody titers significantly increased after the first injection of adenovirus-lacZ at more than 10(8) plaque-forming unit (PFU). The repetitive expression of lacZ gene in the mouse skin markedly decreased when the second injection is done more than 2 weeks after the first injection. Chronic low-dose treatment with cyclophosphamide or etoposide markedly suppressed neutralizing antibody titers in the mouse serum and restored the gene expression in the mouse skin on the second and third injection.

CONCLUSIONS

It is suggested that repetitive gene expression by adenovirus-mediated transfer may be reduced by circulating neutralizing antibodies and could be restored by chronic low-dose treatment with cyclophosphamide or etoposide.

Emerging drug treatments for cystic fibrosis

Cystic fibrosis (CF) is one of the most common life-shortening inherited disorders. Mutations in the cystic fibrosis transmembrane regulator (CFTR) gene disrupt the localisation and function of the cAMP-mediated chloride channel. Most of the morbidity and mortality arise from the lung disease which is characterised by excessive inflammation and chronic infection. Research into the mechanisms of wild-type and mutant CFTR biogenesis suggest that multiple drug targets can be identified. This review explores the current understanding of the nature of the different mutant CFTR forms and the potential for repair of the chloride channel defect. High-throughput screening, pharmacogenomics and proteomics bring recent technological advances to the field.

Immune responses against adenoviral vectors and their transgene products: a review of strategies for evasion

Human adenoviruses have been adopted as attractive vectors for in vivo gene therapy since they have a well-characterized genomic organization, can be grown to high titres and efficiently transduce a wide spectrum of dividing and non-dividing cells. However, the first-generation of adenoviral (Ad) vectors yielded only transient expression of the transgene in most immunocompetent mice. This constituted a major limitation of this early vector type. In contrast, persistent transgene expression can be established in immunodeficient mice. This suggests that the immunogenicity of adenoviral vectors limits the effective period of adenovirus-based gene therapy. Much effort has been put in devising strategies to circumvent the limitations imposed onto gene therapy by the immune system. Improvements in vector design have significantly improved the performance of the adenovirus vectors. Based on these results it is reasonable to anticipate that new modifications of the vectors will overcome some of the immunological barriers and will further expand the applicability of adenovirus-derived vectors.

Effect of Pseudomonas-induced chronic lung inflammation on specific cytotoxic T-cell responses to adenoviral vectors in mice

A mouse model of chronic Pseudomonas-induced bronchopulmonary inflammation that mimics chronic cystic fibrosis (CF) lung disease was employed to determine whether this inflammatory milieu influences immune responses to adenoviral vectors. Pseudomonas-infected and control mice were inoculated intranasally with a second-generation type 2 adenovirus (Ad2) vector (Ad2/betagal-2). After 3 weeks, serum and airway Ad2-specific antibodies and Ad2 vector-directed, cytotoxic T-lymphocyte (CTL) activity in splenocytes were measured. No differences in humoral immunity were observed between Pseudomonas-infected mice and controls. However, there was a two- to three-fold increase in Ad-specific CTL activity in the Pseudomonas-infected mice compared to control mice. MHC class I-dependent antigen presentation by antigen-presenting cells (APC) from lungs of Pseudomonas-infected mice was also significantly increased compared to APC from control mice, suggesting a mechanism that may contribute to increased Ad-specific CD8+ CTL responses. It was concluded that Ad-specific CTL activity is enhanced in the setting of pre-existing chronic Pseudomonas-induced lung inflammation similar to CF lung disease, and that increased antigen presentation via MHC class I in this setting may be one underlying mechanism. These findings underscore the importance of considering the influence of the disease milieu when evaluating modes of gene therapy for such diseases in animal models.

Gene therapy. Therapeutic approaches and implications

The present article is an overview of gene therapy with an emphasis on different approaches and its implications in the clinic. Genetic interventions have been applied to the diagnosis of and therapy for an array of human diseases. The initial concept of gene therapy was focused on the treatment of genetic diseases. Subsequently, the field of gene therapy has been expanded, with a major focus on cancer. Although the results of early gene therapy-based clinical trials have been encouraging, there is a need for gene delivery vectors that feature reduced immunogenicity and improved targeting ability. The results of phases I/II clinical trials have suggested the important role of gene therapy as a versatile and powerful treatment tool, especially for human cancers. One reasonable expectation is that performing gene therapy at an earlier stage in the disease process or for minimal residual disease may be more advantageous.

Protection of Cftr knockout mice from acute lung infection by a helper-dependent adenoviral vector expressing Cftr in airway epithelia

We developed a helper-dependent adenoviral vector for cystic fibrosis lung gene therapy. The vector expresses cystic fibrosis transmembrane conductance regulator (Cftr) using control elements from cytokeratin 18. The vector expressed properly localized CFTR in cultured cells and in the airway epithelia of mice. Cftr RNA and protein were present in whole lung and bronchioles, respectively, for 28 days after a vector dose. Acute inflammation was minimal to moderate. To test the therapeutic potential of the vector, we challenged mice with a clinical strain of Burkholderia cepacia complex (Bcc). Cftr knockout mice (but not Cftr+/+ littermates) challenged with Bcc developed severe lung histopathology and had high lung bacteria counts. Cftr knockout mice receiving gene therapy 7 days before Bcc challenge had less severe histopathology, and the number of lung bacteria was reduced to the level seen in Cftr+/+ littermates. These data suggest that gene therapy could benefit cystic fibrosis patients by reducing susceptibility to opportunistic pathogens.

Gene therapy for inherited lung disorders: an insight into pulmonary defence

This review summarizes the latest developments in viral and nonviral gene delivery systems to the lung, and the problems that have to be overcome. Gene delivery has the potential to offer effective treatment to patients with life-threatening lung diseases such as cystic fibrosis and alpha(1)-antitrypsin deficiency, and could modify gene-environment relationships in asthma and other respiratory diseases. Phase I clinical trials conducted in the early 1990s showed that in principle gene transfer to the lung was safe. Although the preliminary results gave encouraging laboratory data, gene expression from viral or nonviral gene delivery systems was too inefficient or transient to offer clinical benefit. Initial optimism gave way to the realization that gene therapy to the lung was unlikely to be straightforward. The host innate and acquired immune system, which protects against infection from inhaled bacteria and viruses, represents a major barrier to successful gene transfer to the lung. A better understanding of the immunological barriers which exist in the lung may allow the development of pharmacological and/or immunological agents that modulate the host immune system to allow for a more continuous and regulated level of gene expression following gene transfer.

Introduction to cancer gene therapy

Over the past decade, the unprecedented growth in science and technology has fueled the development of novel treatment strategies to combat disease. The creative and innovative efforts of scientists and clinicians to overcome the multitude of unforeseen obstacles to success is no better exemplified than in the field of cancer gene therapy. Since its inception, developers of cancer gene therapy have been charged with the challenge of altering basic tumor biology or, alternatively, the host responses for the purpose of tumor eradication and prevention. Several major therapeutic strategies have emerged from preclinical studies, and results from these early studies hold promise for altering the clinical outcome in a variety of malignancies. These strategies may be broadly subcategorized and range in intent from alteration of the tumor cell phenotype by replacement of defective cellular response genes (e.g., mutated or deleted tumor suppressor genes) to the enhancement of the immunological response to cancer (e.g., amplification of the cell surface antigen signature or modulation of the host response). Not surprisingly, the increasingly intricate nature of tumor biology revealed over the past several years has effectively raised the bar of success for those involved in the development of effective molecular and cancer gene therapy strategies. This, in turn, has led to the development of more complex therapies that frequently draw upon multiple disciplines in an effort to optimize treatment response.

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.

Infection of replication-deficient adenoviral vector enhances interleukin-8 production in small airway epithelial cells more than in large airway epithelial cells

OBJECTIVE

In clinical trials or experiments of gene therapy, airway administration of an adenoviral-based vector (E1A-deleted) elicits a dose-dependent inflammatory response with limitation in the duration of transgene expression. The purpose of this study was to evaluate the possibility that the adenoviral-based vector directly enhances IL-8 production independent of adenoviral E1A in normal human airway epithelial cells and to examine the different responses between primary human bronchial epithelial cells (HBE) and primary human small airway epithelial cells (HSAE) in production of IL-8 following exposure to an adenovirus vector.

METHODOLOGY

Interleukin (IL)-8 levels were evaluated in the culture medium from HBE and HSAE treated with increasing doses of E1A-deleted adenoviral vector contained the Escherichia coli LacZ reporter gene (AdCMVLacZ). To clarify the mechanism of enhancing IL-8 production in airway epithelial cells by infection with adenovirus vector, alphavbeta5 agonistic antibody as an analogue of adenoviral capsid and adenoviral capsid vector denatured by exposure to ultraviolet (UV) light were used in the present study.

RESULTS

Inoculation of HBE with AdCMVLacZ at a multiplicity of infection (MOI) of between 1 and 200 resulted in a dose-dependent expression of LacZ, and maximal expression was observed at a MOI of 100. In contrast, inoculation of HSAE with AdCMVLacZ resulted in maximum expression of LacZ at a MOI of 10. Interleukin-8 levels in culture media from the same experiments revealed significantly greater production of IL-8 in HSAE inoculated with AdCMVLacZ at a MOI of 50, compared to HBE under the same conditions. The capsid-denatured adenoviral vector did not enhance IL-8 production, and alphavbeta5 agonistic antibody induced IL-8 enhancement.

CONCLUSION

These results suggest that the adenoviral vector directly induces the expression of airway epithelial inflammatory cytokines in the pathogenesis of inflammation and that small airway cells have a greater affinity for adenovirus than other airway epithelial cells.

Human alpha-defensin 1 (HNP-1) inhibits adenoviral infection in vitro

Adenoviral gene transfer is a promising tool for direct treatment of cystic fibrosis by local application of the CFTR-gene via the airway. However, various host defense mechanisms reduce the adenoviral infectivity and hereby the success of adenoviral transduction. Twenty-eight of 62 BALs from various patients exerted strong inhibition of adenoviral infection of 293 cells. This soluble activity could be attributed to larger peptides rather than to small molecules. Beside immunoglobulins, certain epithelial cell-derived anti-microbial polypeptides called defensins might be involved. Therefore, we investigated the inhibitory potential of the defensins HNP-1 and HBD-2 on adenoviral infectivity. 293 cells infected with adenovirus-type 5 were treated with both peptides. Compared to control, HNP-1 reduced adenoviral infection by more than 95% if administered at 50 microg/ml, and the IC50-value was 15 microg/ml. In contrast, HBD-2 was much less efficient and did not block adenoviral infection at doses up to 50 microg/ml. Our data demonstrate that the presence of certain polypeptides in the BAL, i.e. the defensin HNP-1, might be the major obstacle for adenoviral gene transfer, particularly in patients with inflammatory diseases.

Non-invasive observation of repeated adenoviral GFP gene delivery to the anterior segment of the monkey eye in vivo

BACKGROUND

Glaucoma is a group of chronic eye diseases often associated with an elevated intraocular pressure (IOP). If not controlled, the condition leads to blindness. The eye tissue responsible for maintaining aqueous humor resistance and thus normal IOP is the trabecular meshwork (TM). Adenoviral vectors are capable of transducing the TM in several rodent species. Because of the relevance of the non-human primate model in the study of glaucoma, gene transfer to the eyes of cynomolgus monkeys was investigated.

METHODS

Four cynomolgus monkeys were injected with AdenoGFP into the anterior chamber: two monkeys received 10(9) pfu and the other two 10(7) pfu. One monkey received four consecutive injections into the same eye (10(7) pfu in each injection) over a 7-month period. In vivo gene transfer (fluorescence) and IOP were evaluated by standard clinical ophthalmic instruments (slit lamp biomicroscopy, gonioscopy and tonometry). Histopathology and cellular distribution were assessed postmortem.

RESULTS

The first injection of the lower viral dose resulted in marked TM-preferred gene transfer visible non-invasively by in vivo gonioscopy. The expression of the transgene lasted for 3-4 weeks with little or no signs of clinical inflammation. Gene transfer was achieved on three sequential occasions (3-4 weeks each) but failed and induced substantial, albeit reversible, corneal abnormalities on the fourth occasion.

CONCLUSIONS

Gene transfer to the TM and cornea can be monitored non-invasively in non-human primates, allowing correlation of gene transfer with physiological parameters. Because of ocular immune privilege, repeated anterior chamber administrations of adenoviral vectors expressing appropriate genes may have therapeutic potential for glaucoma.

Aerosol and lobar administration of a recombinant adenovirus to individuals with cystic fibrosis. I. Methods, safety, and clinical implications

Cystic fibrosis (CF), an autosomal recessive disorder resulting from mutations in the cystic fibrosis trans-membrane conductance regulator (CFTR) gene, is the most common lethal genetic illness in the Caucasian population. Gene transfer to airway epithelium, using adenoviruses containing normal CFTR cDNA, leads to transient production of CFTR mRNA and, in some studies, to correction of the airway epithelial ion transport defect caused by dysfunctional CFTR. Inflammatory responses to the adenoviral vector have been reported, particularly at high viral titers. We evaluated the effects of adenovirus-mediated CFTR gene transfer to airway epithelium in 36 subjects with CF (34 individuals, 2 of whom received two separate doses of vector), 20 by lobar instillation and 16 by aerosol administration. Doses ranged from 8 x 10(6) to 2.5 x 10(10) infective units (IU), in 0.5-log increments. After lobar administration of low doses there were occasional reports of cough, low-grade temperature, and myalgias. At the highest lobar dose (2.5 x 10(9) IU) two of three patients had transient myalgias, fever, and increased sputum production with obvious infiltrates on CT scan. After aerosol administration there were no significant systemic symptoms until the 2.5 x 10(10) IU dose, when both patients experienced myalgias and fever that resolved within 24 hr. There were no infiltrates seen on chest CT scans in any of the patients in the aerosol administration group. There were no consistent changes in pulmonary function tests or any significant rise in serum IgG or neutralizing antibodies in patients from either group. Serum, sputum, and nasal cytokines, measured before and after vector administration, showed no correlation with adenoviral dose. Gene transfer to lung cells was inefficient and expression was transient. Cells infected with the vector included mononuclear inflammatory cells as well as cuboidal and columnar epithelial cells. In summary, we found no consistent immune response, no evidence of viral shedding, and no consistent change in pulmonary function in response to adenovirus-mediated CFTR gene transfer. At higher doses there was a mild, nonspecific inflammatory response, as evidenced by fevers and myalgias. Overall, vector administration was tolerated but transfer of CFTR cDNA was inefficient and transgene expression was transient for the doses and method of administration used here.

Development of novel formulations that enhance adenoviral-mediated gene expression in the lung in vitro and in vivo

Despite remarkable progress in the development of both viral and non-viral gene delivery vectors for cystic fibrosis therapy, low efficiency of gene transfer to the airway epithelium is a major obstacle to clinical application. Here we develop formulations that enhance cellular absorption of adenoviral vectors. We selected excipients from a panel of pharmaceutically acceptable com-pounds known to enhance drug absorption. Transduction efficiency of the virus in the presence of each ingredient was assessed in vitro and in vivo. Mannitol and chitosan substantially enhanced transduction efficiency in vitro and augmented expression in vivo by 4 and 8 log units, respectively. The most successful formulation (a blend of sucrose, mannitol, and Pluronic F68) transduced 100% of an A549 cell population in vitro and produced areas of intense gene expression in both large and small airways in vivo with minimal toxicity. Dose response studies also indicate that when placed in this formulation, the viral dose can be lowered by 1/2 log while maintaining superior levels of transgene expression. This formulation also enhanced the physical stability of the virus. No significant loss in titer was detected from a lyophilized formulation after storage at 25 degrees C for 30 days.

Induction of stable prenatal tolerance to beta-galactosidase by in utero gene transfer into preimmune sheep fetuses

The successful transduction of hematopoietic stem cells and long-term (28 months) transgene expression within the hematopoietic system following the direct injection of high-titer retroviral vectors into preimmune fetal sheep was previously demonstrated. The present studies extended these analyses for 40 months postinjection and evaluated whether the longevity of transgene expression in this model system was the result of induction of prenatal tolerance to the transgene product. The intraperitoneal injection of retroviral vectors into preimmune sheep fetuses transduces thymic epithelial cells thought to present antigen and thus define self during immune system development. To directly demonstrate induction of tolerance, postnatal sheep were boosted with purified beta-galactosidase and showed that the peripheral blood lymphocytes from in utero-transduced sheep exhibited significantly lower stimulation indices to transduced autologous cells than did control animals and that the in utero-transduced sheep had a reduced ability to mount an antibody response to the vector-encoded beta-galactosidase protein compared with control sheep. Collectively, our results provide evidence that the direct injection of retroviral vectors into preimmune sheep fetuses induces cellular and humoral tolerance to the vector/transgene products and provide an explanation for the duration and stability of transgene expression seen in this model. These results also suggest that even relatively low levels of gene transfer in utero may render the recipient tolerant to the exogenous gene and thus potentially permit the successful postnatal treatment of the recipient. (Blood. 2001;97:3417-3423)

Remote adenoviral gene delivery to the spinal cord: contralateral delivery and reinjection

OBJECTIVE

This study characterizes the distribution of adenoviral genes in the spinal cord after viral vector injection into the sciatic nerve. It also evaluates the ability of repeated adenoviral sciatic nerve injections to prolong gene expression in the spinal cord.

METHODS

Rat sciatic nerves were unilaterally coinjected with the retrograde tracer Fluoro-Gold (Fluorochrome, Inc., Denver, CO) and the adenoviral vector Ad5RSVntLacZ. The distribution of adenoviral gene expression in the spinal cord was compared with that of Fluoro-Gold. Next, levels of gene expression in the sciatic nerve and spinal cord were compared after single and repeated injections of Ad5RSVntLacZ. Finally, remote spinal cord gene expression in naive animals was compared with expression in animals that had been pretreated with subcutaneous Ad5RSVntLacZ inoculation.

RESULTS

Viral gene expression was detected in all quadrants of the spinal cord gray matter, whereas Fluoro-Gold was detected only in the ipsilateral ventral horn (n = 5). This remote delivery was blocked by sciatic nerve transection (n = 10). Viral gene expression occurred in the sciatic nerve after both initial and repeated injections, whereas remote gene expression in the spinal cord was observed only after primary sciatic nerve injection (n = 24; P < 0.003). As with repeated sciatic nerve injections, subcutaneous inoculation with Ad5RSVntLacZ blocked subsequent remote spinal cord gene delivery (n = 8; P < 0.05).

CONCLUSION

Remote viral gene delivery occurs in neurons without direct sciatic nerve projections but is dependent on intact peripheral nerves. Repeated injections fail to boost spinal cord gene expression, because of immune recognition of reinjected virus.

Host responses and persistence of vector genome following intrabronchial administration of an E1(-)E3(-) adenovirus gene transfer vector to normal individuals

Adenovirus (Ad)-mediated gene transfer to the respiratory epithelium of experimental animals and to nasal and airway epithelium of individuals with cystic fibrosis is followed by transient gene expression. Extensive studies in experimental animals are consistent with the concept that local cellular host anti-vector immune responses account for this short-term expression, and systemic and local [lung epithelial lining fluid (ELF)] anti-Ad neutralizing antibodies are generated following Ad vector administration to the respiratory epithelial surface. To determine if this paradigm holds in normal humans, a first-generation Ad vector (Ad(GV)CD.10, an E1(-)E3(-) Ad serotype 5-based vector coding for the Escherichia coli cytosine deaminase gene) was sprayed locally in escalating doses (8 x 10(8)-8 x 10(10) particle units (pu), n = 2/group) into the lung airway epithelium of six normal individuals. Serum, ELF, and endobronchial biopsies were obtained at baseline and at various time points following vector administration. In contrast to the observations in experimental animals in which lung administration of first-generation Ad vectors is followed by strong systemic and local host response, bronchial spray administration of the Ad vector to normal humans showed: (1) minimal inflammation in bronchial biopsies, bronchial brushing, and bronchoalveolar lavage fluid; (2) no blood lymphocyte proliferation in five of six individuals in response to in vitro stimulation with Ad antigens; and (3) no significant increase from baseline in blood or lung ELF anti-Ad neutralizing antibodies. Despite this minimal normal human anti-Ad host response, dose-dependent levels of vector DNA in the airway epithelium were transient. Vector DNA in the targeted airway epithelial cells peaked in a dose-dependent fashion at 0.007 to 1.1 copies/cell at day 7 and declined thereafter, reducing to <10% of peak levels by 2 weeks. These observations demonstrate both the strengths and the limits of using experimental animals to predict human responses to gene transfer vectors. While the transient nature of Ad vector persistence in the airway epithelium is predicted by most experimental animal studies, respiratory epithelial administration of first-generation Ad vectors at doses up to 10(10) pu to airway epithelium of healthy individuals elicits minimal to no detectable systemic and mucosal humoral and cellular immune responses, an observation diametrically opposed to the host responses measured in experimental animals. These findings suggest that, while adaptive anti-Ad immune responses likely play some role in the disappearance of the vector DNA following vector administration to the human lung, other mechanisms may also be involved in the response of humans to Ad gene transfer vectors.

Anti-tumorigenic effect of a K-ras ribozyme against human lung cancer cell line heterotransplants in nude mice

Approximately 15-30% of human non-small cell lung cancers (NSCLC) carry K-ras mutations, among which point mutations at codon 12 are the most common. This study characterizes the anti-tumor effect of an anti-K-ras ribozyme adenoviral vector (KRbz-ADV; replication-deficient, E1-deleted Ad5 backbone) against NSCLC lines that express the relevant mutation (K-ras codon 12 GGT --> GTT; H441 and H1725). KRbz-ADV significantly inhibited tumor cell growth (38-94% reduction by 3H-thymidine uptake) in a time- and dose-dependent manner, but produced minimal growth inhibition on normal epithelial cells, or NSCLC H1650 cells that lack the relevant mutation. The in vivo anti-tumorigenic effect of KRbz-ADV treatment was characterized with cell line xenografts in nu/nu mice. Pre-treatment with KRbz-ADV (10 or 20 p.f.u. per cell) completely abrogated subcutaneous engraftment of H441 (n = 13) or H1725 cells (n = 8), as compared with a 100% tumor take and progressive tumor growth in animals that received untreated tumor cells, or control vector (luciferase-adenovirus/Luc-ADV)-treated tumor cells. Pre-treatment with a mutant anti-K-ras ribozyme adenoviral vector (mutKRbz-ADV), which has the same specificity as KRbz but lacks ribozyme catalytic activity, did not produce an anti-tumorigenic effect. The in vivo effect of KRbz-ADV treatment was further examined by initiating injections (2 x 10(9) p.f.u.) at 7 days after tumor induction. Pre-existing tumor growth was reduced by 39% by a single intratumoral injection. Repeat injections (three or five KRbz-ADV-intratumoral injections at 2 x 10(9) p.f.u. every other day) resulted in complete tumor regression in five of seven mice. In contrast, single or multiple injections of control vector Luc-ADV did not significantly alter tumor xenograft outcome. Ribozyme expression was confirmed in H441 cells that demonstrated reduced growth after KRbz-ADV treatment. Reduced growth corresponded to significantly lowered levels of K-ras mRNA, as defined by RT-PCR (51% of untreated level, n = 3) and RNase protection assay (56% of untreated level, n = 4) analyses. Further, 37.5% of KRbz-ADV-treated cells underwent apoptosis, as compared with 11.7%, and 19.0% in untreated and Luc-ADV-treated cultures, respectively. A significantly higher proportion of KRbz-ADV-treated H441 cells (58.2%) underwent apoptosis when maintained under anchor-independent conditions that simulate in vivo tumorigenesis ('anoikis'). This is the first report that demonstrates that KRbz-ADV can effectively inhibit in vivo tumorigenesis, and produces regression of pre-existing human lung tumor xenografts having the relevant K-ras mutation.

Adenoviral-mediated gene transfer in wound healing

The application of gene transfer strategies to wound healing is not an obvious use of this technology until one considers the important role of cytokines and growth factors in the normal wound healing response. Several gene transfer strategies have been proposed, from in vitro retroviral-mediated gene transfer with autologous transplantation, to in vivo plasmid based gene transfer as retroviral gene transfer. The limitations of these approaches have been efficiency of gene transfer, transgene expression and biologic response. Adenoviral-mediated gene transfer in wound healing is a relatively new application of this vector. The advantage of the adenovirus as a gene transfer vector lies in its ability to transduce nondividing cells of all types at very high efficiency without integration into the host cell's genome. The disadvantage of adenovirus as a vector is the relatively short duration of transgene expression and the inflammatory response it elicits. In the setting of wound healing brief duration of high levels of transgene may be all that is necessary to favorably influence wound healing. Secondly, as wound healing is fundamentally an inflammatory response, the inflammation elicited by the adenovirus may not be detrimental as long as the transgene is a growth factor with significant vulnerary effects such as platelet-derived growth factor-B. This review summarizes the current state of adenoviral-mediated gene transfer in experimental models of impaired wound healing which have laid the groundwork for proposed phase I clinical trials of adenoviral-mediated gene transfer of platelet-derived growth factor-B in chronic venous leg ulcers and chronic nonhealing diabetic foot ulcers. Adenoviral-mediated gene transfer is a useful tool in the study of the role of specific cytokines and growth factors in normal and impaired wound healing. Adenoviral-mediated gene transfer may hold significant promise for clinical application as a means of efficient growth factor delivery in correcting impaired wound healing.

Adenoviral vector expressing ICP47 inhibits adenovirus-specific cytotoxic T lymphocytes in nonhuman primates

Studies from several laboratories have shown that administration of E1-deleted Ad vectors results only in transient transgene expression in the lungs of immunocompetent animals. This is due, at least in part, to destruction of vector-transduced cells by host cellular immune responses (predominantly CD8(+) CTLs) directed against viral proteins and/or immunogenic transgene products. We have previously demonstrated that E1-deleted Ad vectors can lead to persistent expression of human cystic fibrosis transmembrane conductance regulator (hCFTR) in the lungs of several strains of immunocompetent mice, despite the presence of Ad-specific CTLs. However, we found that these same vectors gave rise only to transient hCFTR expression in the lungs of rhesus monkeys. We have constructed new Ad vectors that coexpress both hCFTR and the ICP47 gene from herpes simplex virus. ICP47 has been shown to inhibit the transporter associated with antigen presentation, thus blocking major histocompatibility antigen I (MHC class I)-mediated antigen presentation to CD8(+) T cells. The Ad/hCFTR/ICP47 vector decreased levels of cell-surface MHC class I molecules on infected monkey and human cell lines. Similar results were obtained with primary human cells and primary monkey airway epithelial cells. In vitro studies showed that the Ad/hCFTR/ICP47 vector decreased cytolysis by both monkey and human CTLs. When Ad/hCFTR/ICP47 was administered to the lungs of rhesus monkeys, it inhibited the generation of Ad-specific CTLs. However, natural killer cell activity was enhanced in monkeys treated with the Ad/hCFTR/ICP47 vector.

Internalization of adenovirus by alveolar macrophages initiates early proinflammatory signaling during acute respiratory tract infection

Adenovirus is a common respiratory pathogen which causes a broad range of distinct clinical syndromes and has recently received attention for its potential for in vivo gene delivery. Although adenovirus respiratory tract infection (ARTI) results in dose-dependent, local inflammation, the pathogenesis of this remains unclear. We hypothesized that alveolar macrophages (AMphi) rapidly internalize adenovirus following in vivo pulmonary administration and then initiate inflammatory signaling within the lung. To evaluate the role of AMphi in the induction of lung inflammation during ARTI in vivo, we directly assessed adenovirus uptake by murine AMphi and correlated uptake with the initiation of proinflammatory gene expression. Stimulation of cytokine (tumor necrosis factor alpha [TNF-alpha], interleukin-6 [IL-6], macrophage inflammatory protein-2 [MIP-2], and MIP-1alpha) expression in the lung was evaluated at the level of mRNA (by reverse transcription-PCR [RT-PCR]) and protein (by enzyme-linked immunosorbent assay) and by identification of cells expressing TNF-alpha and IL-6 mRNA in lung tissues (by in situ hybridization) and isolated lung lavage cells (by RT-PCR). Adenovirus, labeled with the fluorescent dye (Cy3), was rapidly and widely distributed on epithelial surfaces of airways and alveoli and was very rapidly ( approximately 1 min) localized within AMphi. At 30 min after infection AMphi but not airway epithelial or vascular endothelial cells expressed mRNA for TNF-alpha and IL-6, thus identifying AMphi as the cell source of initial cytokine signaling. IL-6, TNF-alpha, MIP-2, and MIP-1alpha levels progressively increased in bronchoalveolar lavage fluid after pulmonary adenovirus infection, and all were significantly elevated at 6 h (P < 0.05). To begin to define the molecular mechanism(s) by which adenovirus initiates the inflammatory signaling in macrophages, TNF-alpha expression from adenovirus-infected RAW264.7 macrophages was evaluated in vitro. TNF-alpha expression was readily detected in adenovirus-infected RAW cell supernatant with kinetics similar to AMphi during in vivo infection. Blockage of virus uptake at specific cellular sites, including internalization (by wortmannin), endosome acidification and/or lysis (by chloroquine) or by Ca(2+) chelation (by BAPTA) completely blocked TNF-alpha expression. In conclusion, results showed that during ARTI, (i) AMphi rapidly internalized adenovirus, (ii) expression of inflammatory mediators was initiated within AMphi and not airway epithelial or other cells, and (iii) the initiation of inflammatory signaling was linked to virion uptake by macrophages occurring at a point after vesicle acidification. These results have implications for our understanding of the role of the AMphi in the initiation of inflammation following adenovirus infection and adenovirus-mediated gene transfer to the lung.

Intravascular and endobronchial DNA delivery to murine lung tissue using a novel, nonviral vector

Gene transfer to the lung can be achieved via either the airway or the pulmonary vasculature. We evaluated gene transfer and expression by intravascular and endobronchial routes, using DNA complexed with G9 PAMAM dendrimer or naked plasmid DNA. Intravascular tail vein delivery of dendrimer-complexed pCF1CAT plasmid resulted in high levels of transgene expression in the lung at 12 and 24 hr, followed by a second peak of expression 3 to 5 days after administration. After intravenous administration of the complexes, CAT expression was never observed in organs other than the lung. There were only minimal levels of CAT protein expressed in the lung after intravenous administration of naked plasmid DNA. Repeated intravascular doses of the dendrimer-complexed plasmid, administered four times at 4-day intervals, maintained expression at 15-25% of peak concentrations achieved after the initial dose. Endobronchial delivery of naked pCF1CAT plasmid produced significant amounts of CAT protein in the lung. Comparison of intratracheal and intranasal routes resulted in similar expression levels of CAT in the lung and trachea. However, in juxtaposition to vascular delivery, intranasal delivery of dendrimer-complexed plasmid DNA gave lower levels of CAT expression than that observed with naked plasmid DNA. In situ localization of CAT enzymatic activity suggested that vascular administration seemed to achieve expression in the lung parenchyma, mainly within the alveoli, while endobronchial administration primarily targeted bronchial epithelium. Our results show that intravenously administered G9 dendrimer is an effective vector for pulmonary gene transfer and that transgene expression can be prolonged by repeated administration of dendrimer-complexed DNA.

Gene therapy for cystic fibrosis

The gene for cystic fibrosis was identified in 1989 and this together with the emerging technology of gene therapy heralded a new dawn for the treatment of genetic disease. The initial optimism however gave way to the realisation that gene therapy for cystic fibrosis was unlikely to be straightforward. The lung was considered an ideal organ to target due to ease of access, but subsequent research has shown that the airway surface provides an efficient barrier to topically applied gene transfer agents. A number of Phase I clinical safety trials were carried out through the 1990s and provided proof of concept evidence that delivery of DNA by either viral or non-viral means was safe though not clinically efficacious. Current research is now focusing more on the barriers faced by delivery agents, with the aim that more efficient gene delivery will lead to a gene therapeutic for cystic fibrosis.

Phosphonocationic lipids in protein delivery to mice lungs

Cationic liposomes constitute one of the main approaches currently investigated to introduce a gene with therapeutic properties into a cell. Another alternative consists in directly introducing the normal protein of concern to, for example, restore the deleted function. We report here on in vitro and in vivo results obtained with GLB73, one of the phosphonolipids investigated as gene transfer agents. In previous studies this cationic lipid had shown its DNA-transfer efficacy in vitro and in vivo. We also confirmed the feasibility of protein/cationic lipid delivery in epithelial cells of mice lungs after intratracheal administration by use of a reporter gene (beta-galactosidase). Two quantitative tests (i.e., a chemiluminescent assay and a flow cytometry assay) were used to determine the amount of beta-galactosidase found in the lungs and the percentage of transfected cells. They showed that 50% of the cells of mice lungs were still positive at day 4 after protein/GLB73 delivery. Immunohistochemistry and electron microscopy studies allowed us to determine the spatial distribution and visualize the penetration of our complex into the lungs.

Immune responses against replication-deficient adenovirus inhibit ovalbumin-specific allergic reactions in mice

Replication-deficient adenovirus vector (Ad) is one of the most efficient gene transfer vehicles for human gene therapy. However, Ad is antigenic, known to evoke prominent inflammatory responses in vivo, and there are concerns that using Ad in patients with immune-mediated disorders (allergy and autoimmune diseases) may affect the status of the diseases. To evaluate this concept in a manner close to clinical scenarios, a mouse model of airway eosinophilic inflammation was developed by administering intraperitoneal injections and inhalations of chicken ovalbumin (OA), with Ad administered intranasally 5 days after the OA sensitization. The administration of Ad resulted in a significant suppression of eosinophil counts in peripheral blood as well as in the bronchoalveolar lavage fluid (BALF), and a decrease in OA-specific IgE. The decrease in the number of eosinophils in BALF was associated with a marked upregulation of interferon gamma (IFN-gamma) expression. In contrast, the Ad-specific, delayed-type hypersensitivity response and efficacy of reporter gene expression mediated by Ad were only marginally affected in animals sensitized with OA. Together, these data support the idea that Ad administration in patients with Th2-mediated immune disorders does not exacerbate the parameters of ongoing inflammations or gene transfer efficiency, and with its ability to induce prominent type 1 immune response to the antigen in vivo, Ad could potentially be used as an efficient adjuvant to control immune disorders where Th2 cell-mediated mechanisms are involved.

In utero transfer and expression of exogenous genes in sheep

OBJECTIVE

We have previously reported that directly injecting low-titer retroviral vector supernatant into pre-immune sheep fetuses resulted in the transfer and long-term expression of the bacterial NeoR gene within the hematopoietic system of these animals for over 5 years. In the present studies, we investigated whether using a higher titer vector would enable more efficient transduction and expression of the transgenes within the hematopoetic cells in sheep injected in utero.

MATERIALS AND METHODS

Sixteen pre-immune sheep fetuses were injected intraperitoneally with the G1nBgSvNa8.1 helper-free retroviral vector supernatant encoding the bacterial NeoR and LacZ genes (titer: 1x10(7) cfu/mL).

RESULTS

Over the 2-year time course of these studies, the presence and expression of the NeoR and LacZ genes were demonstrated in 12 of the 14 animals evaluated by several immunological and biochemical methods. Seven of the 12 sheep examined by flow cytometric analysis contained > or =6% transduced peripheral blood lymphocytes. Vector distribution was widespread without any detectable pathology. Importantly, PCR analyses and breeding experiments demonstrated that the germ line was not altered.

CONCLUSIONS

These studies confirmed that direct injection of an engineered retrovirus is a feasible means of safely delivering foreign genes into a developing fetus and thus achieving long-term expression of the transgenes within the recipient's hematopoietic cells. Furthermore, expression of the NeoR gene from these studies was higher than that reported in our previous study in which a lower titer vector was used.

Canine adenovirus vectors: an alternative for adenovirus-mediated gene transfer

Preclinical studies have shown that gene transfer following readministration of viral vectors is often inefficient due to the presence of neutralizing antibodies. Vectors derived from ubiquitous human adenoviruses may have limited clinical use because preexisting humoral and cellular immunity is found in 90% of the population. Furthermore, risks associated with the use of human adenovirus vectors, such as the need to immunosuppress or tolerize patients to a potentially debilitating virus, are avoidable if efficient nonhuman adenovirus vectors are feasible. Plasmids containing recombinant canine adenovirus (CAV) vectors from which the E1 region had been deleted were generated and transfected into a CAV E1-transcomplementing cell line. Vector stocks, with titers greater than or equal to those obtained with human adenovirus vectors, were free of detectable levels of replication-competent CAV and had a low particle-to-transduction unit ratio. CAV vectors were replication defective in all cell lines tested, transduced human-derived cells at an efficiency similar to that of a comparable human adenovirus type 5 vector, and are amenable to in vivo use. Importantly, 49 of 50 serum samples from healthy individuals did not contain detectable levels of neutralizing CAV antibodies.

Adenoviral vector-mediated expression of physiologic levels of human factor VIII in nonhuman primates

An E1-, E2a-, E3-deleted adenoviral vector (Av3H82) encoding an epitope-tagged B domain-deleted human factor VIII cDNA (flagged FVIII) was evaluated in nonhuman primates. Twelve cynomolgus monkeys received intravenous administration of Av3H82; 6 monkeys received 6 x 10(11) particles/kg and another 6 received 3 x 10(12) particles/kg. Adenoviral vector transduction of the liver was efficient, reproducible, and linearly dose dependent. Physiologic levels of flagged FVIII were readily detected in plasma samples obtained from monkeys that received the higher dose of vector and human FVIII mRNA was detected in their livers. Expression of transgene mRNA was restricted to the liver by the albumin promoter. Although vector DNA was readily detected in the liver of monkeys that received the lower dose, neither human FVIII mRNA nor flagged FVIII protein could be detected. Vector distribution was widespread, with the highest levels observed in liver and spleen. Histopathology, hematology, and serum chemistry analysis identified the liver and blood as major sites of toxicity. Transient mild serum elevations of liver enzymes were observed, along with a dose-dependent inflammatory response in the liver. In addition, mild lymphoid hyperplasia was observed in the spleen. Mild anemia and a transient decrease in platelet count were observed, as was marrow hyperplasia and extramedullary hematopoiesis.