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

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.

Airway gene therapy and cystic fibrosis

Airway disease in cystic fibrosis (CF) is the major cause of death and is presently inadequately treatable, but genetic therapies offer the hope that such life-long disease will be curable, or at least satisfactorily treated. Normal pathogen defences that have evolved on airway surfaces also prevent the various gene vectors now available from producing effective gene transfer. Nevertheless, findings from basic research and human clinical trials are revealing how these barriers might be overcome or circumvented, with benefits to therapeutic efficacy and patient safety. Though progress is slower than expected or desired, the therapeutic rewards will be great when safe and effective gene therapy for CF airway disease becomes a clinical reality.

Aerosol delivery of an enhanced helper-dependent adenovirus formulation to rabbit lung using an intratracheal catheter

BACKGROUND

Poor transduction of the ciliated airway epithelium and inefficient airway delivery of viral vectors are common difficulties encountered in lung gene therapy trials with large animals and humans.

METHODS

We delivered a helper-dependent adenovirus vector, incorporating a human epithelial cell-specific expression cassette, to rabbit lung. An intratracheal device was used to aerosolize a moderate dose of virus (5 x 10(11) particles), mixed with the enhancing agent LPC (L-alpha-lysophosphatidylcholine), directly into the airways. Lung mechanics, body weight and temperature, transgene expression and histopathology were studied at day 5.

RESULTS

Transgene expression was seen in the epithelium of large and small airways, from trachea to terminal bronchioles, with a strong tendency toward the right lung. All cell types of the surface epithelium were transduced. Extensive transduction of the epithelium (66% of cells in trachea) was obtained using virus formulated in isotonic 0.1% LPC, while virus formulated in 0.01% LPC transduced fewer cells (24% in trachea). A transient decrease in dynamic lung compliance was observed immediately following aerosol delivery. Fever and mild-to-moderate patchy pneumonia without edema were also observed.

CONCLUSION

These data demonstrate a strategy for efficient and effective transduction of airway epithelium in a large animal.

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.

Adenoviral Vectors for Gene Replacement Therapy

Adenovirus-based vectors are promising vehicles for gene replacement therapy due to their ability to efficiently transduce a wide variety of proliferating and non-proliferating cells. Over the past decade, different versions of adenoviral vectors (Ads) have been developed. These vectors can be classified into two major categories, based on whether the viral coding sequences are partially (first or second-generation Ads) or completely deleted (helper-dependent or gutted Ads). Both types of Ads have been tested in a variety of gene delivery studies, and major obstacles to their clinical application have been identified. Currently, innate and adaptive host immune responses to Ads remain major challenges, limiting both the initial viral dose and the effectiveness of subsequent administrations. Recent developments in vector design and delivery methods have improved the potential of Ads for successful gene therapy application.

Enhancing adenovirus-mediated gene transfer in vitro and in vivo by addition of protamine and hydrocortisone

BACKGROUND

Inclusion of positively charged polymers such as protamine in adenovector formulations has been reported to improve the efficiency of adenovirus-mediated gene transfer in vitro and in vivo. On the other hand, corticosteroids are known to inhibit inflammation and thus might be useful in minimizing vector-related toxicity. In this study, we evaluated the combined effect of protamine sulfate and hydrocortisone on the efficiency of adenovirus-mediated gene transfer in vitro and in vivo.

METHODS

Protamine and hydrocortisone at different concentrations were added to adenovector formulations. In vitro transgene expression with or without inclusion of protamine and hydrocortisone was evaluated in the breast cancer cell lines MDA-MB-231 and MCF7 and the lung cancer cell lines A549 and H460. In vivo transgene expression in the mouse lung was determined after aerosolized vector delivery.

RESULTS

The combination of 2 micro g/ml protamine and 125 ng/ml hydrocortisone significantly increased transgene expression in vitro in all the cell lines tested. Protamine is only effective when it is added to cells before or together with adenovectors, whereas hydrocortisone is effective when it is added to cells before, together with, or after adenovectors. Inclusion of protamine and hydrocortisone also augmented apoptosis induction caused by adenovectors expressing proapoptotic genes in cancer cells. Moreover, protamine and hydrocortisone dramatically enhanced transgene expression in the mouse lung after aerosolized vector delivery.

CONCLUSIONS

Inclusion of protamine and hydrocortisone in adenovector formulations can improve adenovector-mediated gene expression and may be useful for clinical applications of current adenovirus-mediated gene therapy.

Repeated Adeno-Associated Virus Serotype 2 Aerosol-Mediated Cystic Fibrosis Transmembrane Regulator Gene Transfer to the Lungs of Patients With Cystic Fibrosis

STUDY OBJECTIVES

The primary objective was to determine the safety and tolerability of repeated doses of aerosolized adeno-associated serotype 2 vector containing cystic fibrosis transmembrane conductance regulator (CFTR) complementary DNA (cDNA) [tgAAVCF], an adeno-associated virus (AAV) vector encoding the complete human CFTR cDNA. Secondary objectives included evaluation of pulmonary function assessed by spirometry, lung abnormalities by high-resolution CT (HRCT), airway cytokines, vector shedding, serum neutralizing antibody to AAV serotype 2 (AAV2), and gene transfer and expression in a subset of subjects undergoing bronchoscopy with bronchial brushings.

DESIGN

Randomized, double-blind, placebo-controlled, phase II trial.

SETTING

Eight cystic fibrosis (CF) centers in the United States.

SUBJECTS

CF patients with mild lung disease, defined as FEV(1) > or =60% predicted.

INTERVENTIONS

Subjects were randomized to inhale three aerosolized doses of 1 x 10(13) deoxyribonuclease-resistant particles of tgAAVCF or matching placebo at 30-day intervals using the Pari LC Plus nebulizer (PARI; Richmond, VA).

MEASUREMENTS AND RESULTS

Of 42 subjects randomized, 20 subjects received at least one dose of tgAAVCF and 17 subjects received placebo. No difference in the pattern of adverse events or laboratory abnormalities was noted between the two treatment groups. Improvements in induced-sputum interleukin-8 (p = 0.03) and FEV(1) (p = 0.04) were observed at day 14 and day 30, respectively, in the group receiving tgAAVCF when compared to those receiving placebo. No significant differences in HRCT scans were noted. Vector shedding in sputum was observed at low levels up to 90 days after the third dose of vector. All subjects receiving tgAAVCF exhibited an increase (by at least fourfold) in serum AAV2-neutralizing antibodies and detectable levels in BAL fluid from five of six treated subjects undergoing BAL. Gene transfer but not gene expression was detected in a subset of six tgAAVCF subjects who underwent bronchoscopy.

CONCLUSIONS

Repeat doses of aerosolized tgAAVCF were safe and well tolerated, and resulted in encouraging trends in improvement in pulmonary function in patients with CF and mild lung disease.

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.

Combination of TRAIL gene therapy and chemotherapy enhances antitumor and antimetastasis effects in chemosensitive and chemoresistant breast cancers

We recently found that breast cancer cell lines that are resistant to chemotherapy or to the recombinant TRAIL protein are susceptible to TRAIL gene therapy. However, it is unclear whether a combination of TRAIL gene therapy and chemotherapy will have enhanced antitumor activity or can be used for the treatment of metastasis. In this study, we investigated the combined effect of TRAIL gene therapy and chemotherapeutic agents, including doxorubicin, paclitaxel, vinorelbine, gemcitabine, irinotecan, and floxuridine, in different breast cancer cell lines. In all the cell lines tested, including a breast cancer cell line that is resistant to chemotherapy, the combination of TRAIL gene therapy and cytotoxic agents had either a synergistic or an additive effect. An in vivo study showed that aerosolized administration of an adenovector expressing the GFP-TRAIL fusion protein from the human telomerase reverse transcriptase promoter (designated Ad/gTRAIL) also decreased the number of lung metastases from both doxorubicin-sensitive and doxorubicin-resistant breast cancer cell lines. The combination of TRAIL gene therapy and chemotherapy resulted in a further reduction of lung metastatic nodules with minimal toxicity. These results suggest that a combination of TRAIL gene therapy and chemotherapy is effective in the treatment of metastatic diseases.

Pharmacogenetic heterogeneity of transgene expression in muscle and tumours

BACKGROUND

Recombinant adenoviruses are employed to deliver a therapeutic transgene in the liver, muscle or tumour tissue. However, to rationalise this delivery approach, the factors of variation between individuals need to be identified. It is assumed that differences between inbred strains of laboratory animals are considered to reflect differences between patients. Previously we showed that transgene expression in the liver of different rat strains was dependent on the transcription efficiency of the transgene. In the present paper we investigated if transfection of muscle and tumour tissue were also subject to such variations.

METHODS

Variation, in transgene expression, after intramuscular gene delivery was determined in different rodent strains and gene expression in tumours was investigated in different human and rodent cell lines as well as in subcutaneously implanted rodent tumours. The molecular mechanisms involved in transgene expression were dissected using an adenovirus encoding luciferase. The luciferase activity, the viral DNA copies and the luciferase transcripts were assessed in cultured cells as well as in the tissues.

RESULTS

Large differences of luciferase activity, up to 2 logs, were observed between different rodent strains after intramuscular injection of Ad Luciferase. This inter-strain variation of transgene expression was due to a difference in transcription efficiency. The transgene expression level in tumour cell lines of different tissue origin could be explained largely by the difference of infectibility to the adenovirus. In contrast, the main step responsible for luciferase activity variation, between six human breast cancer cell lines with similar phenotype, was at the transcriptional level.

CONCLUSION

Difference in transcriptional efficiency in muscles as observed between different inbred strains and between human breast cancer cell lines may be expected to occur between individual patients. This might have important consequences for clinical gene therapy. The variation between tumour types and tissues within a species are mainly at the levels of infectivity.

Safety and efficiency of modulating paracellular permeability to enhance airway epithelial gene transfer in vivo

We evaluated the safety of agents that enhance gene transfer by modulating paracellular permeability. Lactate dehydrogenase (LDH) and cytokine release were measured in polarized primary human airway epithelial (HAE) cells after lumenal application of vehicle, ethyleneglycol-bis-(beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA), sodium caprate (C10), or sodium laurate (C12). Lung toxicity was assessed after tracheobronchial instillation to murine airways and the relative ability of these agents to enhance in vivo adenoviral gene transfer was evaluated. Lumenal C12 increased LDH release in vitro, but C10 and EGTA did not. Increased levels of interleukin 8 (IL-8) were secreted from EGTA-pretreated cystic fibrosis HAE cells after apical application of Pseudomonas aeruginosa (10(8) CFU/ml), whereas IL-8 secretion from C10- and C12-pretreated cells was not different from controls. In vivo toxicity studies demonstrated no effect of EGTA, C10, or C12 on weight gain, lung edema, or bronchoalveolar lavage fluid (BALF) albumin. EGTA increased BALF cell counts, neutrophils, and murine (m) macrophage inflammatory protein 2, mKC, mIL-6, and mIL-1 beta levels. C10 had no effect on BALF cell counts or LDH, but increased murine tumor necrosis factor alpha. C12 increased BALF LDH, neutrophils, and mIL-6 levels. Histopathological analysis revealed mild focal lung inflammation more frequently in the EGTA, C10, and C12 groups than in vehicle controls, with greater intensity in the C12 group relative to the other groups. C10 and C12 also increased airway responsiveness to methacholine challenge compared with control and EGTA groups. Adenoviral gene transfer to murine trachea in vivo was enhanced more efficiently by C10 than by C12 or EGTA. Thus, the different toxicities may permit the selection of agents that enhance gene transfer with minimal adverse effects.

Gene therapy for cystic fibrosis by means of aerosol

Gene therapy by aerosol is an attractive approach for the treatment of cystic fibrosis (CF). Clinical trials with aerosols in CF patients have been conducted by five different groups, three using adenoviral vectors and two using cationic liposomes carrying the coding sequence for the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR). These trials revealed that gene transfer from the lumen to the respiratory epithelium can currently be achieved in vivo, but only with low efficiency and for limited duration. Some of the many hurdles on the way to successful gene therapy for this disease will be discussed in this review. Innovative strategies need to be developed to reach this tantalizing goal.

Systemic interleukin-6 responses following administration of adenovirus gene transfer vectors to humans by different routes

Administration of adenovirus (Ad) vectors to animals induces innate immune responses, typified by elevated interleukin-6 (IL-6). To assess innate responses to Ad vectors in humans, we evaluated serum IL-6 following administration of E1(-) E3(-) Ad vectors to different human hosts and the relationship among peak IL-6 and peak anti-Ad neutralizing antibodies. We administered: 1) Ad(GV)CFTR.10, a vector carrying the normal human CFTR cDNA (3 x 10(7) to 2 x 10(10) particle units (pu)) to airways of individuals with cystic fibrosis (CF); 2) Ad(GV)VEGF121.10, a vector carrying the normal human vascular endothelial growth factor (VEGF)121 cDNA, to the myocardium (4 x 10(8) to 4 x 10(10) pu) of individuals with coronary artery disease (CAD) and to lower extremity muscles (4 x 10(8) to 4 x 10(9.5) pu) of individuals with peripheral vascular disease (PVD); and 3) Ad(GV)CD.10, a vector carrying the Escherichia coli cytosine deaminase gene to skin (7 x 10(7) to 7 x 10(9) pu) and airways (7 x 10(8) to 7 x 10(10) pu) of normal individuals and to liver metastasis (4 x 10(8) to 4 x 10(9) pu) of individuals with colon carcinoma. IL-6 increased mildly (up to 220 pg/ml) following vector administration to skin and lung airways of normal individuals and of individuals with CF, and to muscle and liver metastasis of individuals with PVD and colon cancer, respectively. IL-6 responses were higher (up to 1100 pg/ml) following myocardial administration. Control individuals who had chest surgery and bronchoscopy, but no vector administration, had comparable IL-6 increases. Thus, both administration of Ad vectors of humans up to 10(10) pu and the procedures used to administer the vectors elicit systemic IL-6 responses. There was no correlation among peak IL-6 and peak anti-Ad antibodies. These observations indicate that the innate host responses following administration of Ad vectors to humans may result from the procedures used to administer the vector, and from the vector per se.

Thixotropic solutions enhance viral-mediated gene transfer to airway epithelia

Adenovirus-mediated gene transfer to airway epithelia is inefficient in part because its receptor is absent on the apical surface of the airways. Targeting adenovirus to other receptors, increasing the viral concentration, and even prolonging the incubation time with adenovirus vectors can partially overcome the lack of receptors and facilitate gene transfer. Unfortunately, mucociliary clearance would prevent prolonged incubation time in vivo. Thixotropic solutions (TS) are gels that upon a vigorous shearing force reversibly become liquid. We hypothesized that formulating recombinant adenoviruses in TS would decrease virus clearance and thus enhance gene transfer to the airway epithelia. We found that clearance of virus-sized fluorescent beads by human airway epithelia in vitro and by monkey trachea in vivo were markedly decreased when the beads were formulated in TS compared with phosphate-buffered saline (PBS). Adenovirus formulated in TS significantly increased adenovirus-mediated gene transfer of a reporter gene in human airway epithelia in vitro and in murine airway epithelia in vivo. Furthermore, an adenovirus encoding the cystic fibrosis transmembrane regulator (CFTR) gene (AdCFTR) formulated in TS was more efficient in correcting the chloride transport defect in cystic fibrosis airway epithelia than AdCFTR formulated in PBS. These data indicate a novel strategy to augment the efficiency of gene transfer to the airways that may be applicable to a number of different gene transfer vectors and could be of value in gene transfer to cystic fibrosis (CF) airway epithelia in vivo.

Visualization of the transgene distribution according to the administration route allows prediction of the transfection efficacy and validation of the results obtained

Gene transfer to the lung can be achieved via a systemic, that targets the endothelium, or local, that targets the epithelium, delivery route. In the present study, we followed the distribution of a plasmid after transfection using some of our phosphonolipids, which have previously shown their efficiency in transfecting mouse lungs. The plasmid was radiolabeled and varying combinations of plasmid/phosphonolipid were administered by intravenous injection, or by endotracheal spray. The distribution of radioactive labeling was observed over a time course using a gamma-camera. These images were then correlated with the results for luciferase expression levels in the lungs. In each case, lungs were well targeted. However, whereas an intravenous injection reaches all of the lung immediately, progressive diffusion occurs when the plasmid/phosphonolipid is administered via an aerosol. Elimination of the radioactivity associated with plasmid occurs via the urinary tract after intravenous injections, and via the feces using the aerosol delivery approach. The radioactivity detected in the lungs correlated strongly with transgene expression. Thus, such an imaging technique is a powerful strategy to predict the formulation that will generate the best transfection efficiency. This study reveals that scintigraphic imaging permits both validation of the administration method and the results obtained for each animal, thereby reducing the statistical variability of in vivo experiments.

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.

Aerosol and lobar administration of a recombinant adenovirus to individuals with cystic fibrosis. II. Transfection efficiency in airway epithelium

A phase I clinical trial was conducted in which recombinant adenovirus containing the cystic fibrosis trans-membrane regulator (CFTR) (Ad2/CFTR) was administered by bronchoscopic instillation or aerosolization to the lungs of cystic fibrosis (CF) patients. In this paper, we evaluate the efficiency of Ad2/CFTR-mediated transduction of bronchial airway cells. The ability of an Ad2/CFTR vector to transduce airway cells was first evaluated in patients to whom the vector was administered by bronchoscopic instillation. Cells at the administration site were collected 2 days after treatment by bronchoscopic brushing. Ad2-specific CFTR DNA was detected in four of five individuals by PCR, and Ad2-specific CFTR RNA was detected in three of five individuals by RT-PCR. Ad2/CFTR-mediated transduction of airway epithelial cells was then determined in CF individuals receiving this vector by aerosol inhalation. Ad2-specific CFTR DNA was detected in 13 of 13 individuals 2 days after aerosolization, and in 3 of 5 individuals 7 days after aerosolization. Ad2-specific RNA was detected in 4 of 13 individuals on day 2, but was not detected in the 5 individuals tested on day 7. The percentage of airway epithelial cells containing nuclear-localized vector DNA was < or =2.4% as determined by fluorescence in situ hybridization (FISH). However, in some cases, a high percentage of nonepithelial mononuclear cells or squamous metaplastic epithelial cells was infected with the adenoviral vector. In conclusion, aerosol administration is a feasible means to distribute adenoviral vectors throughout the conducting airways, but improvements in adenovirus-mediated transduction of airway epithelial cells are necessary before gene therapy for CF will be effective.