Gene therapy for the respiratory manifestations of cystic fibrosis

Step into the Groove: Engineered Transcription Factors as Modulators of Gene Expression

Increasing knowledge about the influence of dysregulated gene expression in causing numerous diseases opens up new possibilities for the development of innovative therapeutics. In this chapter, we first describe different mechanisms of misregulated gene expression resulting in various pathophysiological conditions. Then, an overview is given of different technologies developed to readjust expression levels of genes. One of the most promising upcoming approaches in this respect is the development of engineered zinc-finger transcription factors. Results obtained from modulating endogenous gene expression using such engineered transcription factors are reviewed in depth. Finally, we address possible pitfalls of using such transcriptional targeting approaches at the "chromatin level." We describe aspects of studies at this level that influence successful DNA binding of engineered transcription factors, thereby affecting gene activity. Engineered transcription factors have great promise as potent therapeutics. Moreover, this technology is expected to yield fundamental knowledge about the organization and function of the genome.

Controlled inhalation of aerosolised therapeutics

With the advent of new, and often expensive, therapeutics designed for aerosol delivery to the lung, there is a need to improve the targeting and efficiency of their delivery. By controlling breathing patterns associated with inhaled aerosols, it has been shown that deposition in the lung can be both maximised and targeted to specific lung regions. A new commercially available device, the AKITA (Inamed GmbH) allows for individualised, controlled inhalation of aerosols produced by conventional nebulisers. Smart card technology is incorporated into the AKITA to both individualise breathing patterns as well as record compliance of therapy. So far, the use of this new device has provided maximal delivery of drug to the lung, with improved patient compliance and minimal waste of drug.

Targeting delivery of aerosols to different lung regions

With the increasing use of aerosolized drugs, there is a need to understand the means by which these drugs can most effectively be targeted to desired regions of the lung. Several attempts have been made at targeting aerosols in the lung by changing particle sizes and breathing patterns with varying degrees of success. Recent use of such techniques as shallow, aerosol bolus delivery and extremely slow inhalations of aerosols in diagnostic lung tests may also prove beneficial for targeting drug delivery to the conducting airways. This review discusses the potential for utilizing aerosol delivery techniques for selectively targeting aerosol deposition along both serial and parallel pathways in the lung. Based on a review of previous studies concerning factors that determine aerosol and gas distribution in the lung, the potential for utilizing various breathing techniques in concert with variations in particle sizes are considered. Further research on the factors that determine distribution of aerosol in the diseased lung may help in designing successful targeting strategies for the future.

Pulmonary microbial infection in mice: comparison of different application methods and correlation of bacterial numbers and histopathology

Many investigations have been performed in characterising experimental bacterial infections in the lung of mice using several pathogens. Robust experimental pulmonary infection models require a reproducible method of application with defined numbers of pathogens to the respiratory tract without contaminating extrapulmonary tissues. At the same time trauma due to the experimental procedure should be kept to a minimum. So far several routes of administration have been used but a systematic comparison of these methods is still missing. Here we provide a comprehensive evaluation of view controlled i.t. instillation, tracheotomy, intranasal application, blind instillation and aerosol infection. An infection dose of up to 5 x 10(4) bacteria (L. monocytogenes) was applied to a group of ten mice by each technique and the animals were killed after 1 h or 24h. The number of viable bacteria was estimated by plating homogenates of the lungs and spleens. In addition, pathological effects on lung tissue were examined by histology 24h after infection. The highest reproducibility was achieved after applying Listeria directly in the trachea under view or by tracheotomy. However, mice were severely affected in their vitality after tracheotomy. Thus, for topical application of bacterial suspension into the lung the view controlled i.t. instillation is most appropriate.

On the transport of lipoplexes through cystic fibrosis sputum

PURPOSE

The aim of this study was to examine the extent to which plasmid DNA (pDNA) complexed to cationic liposomes diffuse through cystic fibrosis (CF) sputum. The influence of the physical and chemical properties of the sputa was evaluated. We further investigated whether degradation of the sputa by recombinant human DNase I (rhDNase I) enhances the transport.

METHODS

The transport of lipoplexes was studied through layers of CF sputa placed between the donor and acceptor compartment of vertical diffusion chambers. The content of the acceptor compartment was analyzed by confocal fluorescence microscopy, gel electrophoresis and Southern blotting. The influence of linear DNA present in the CF sputa on the size, surface charge and gene expression of the lipoplexes was evaluated by dynamic light scattering, particle electrophoresis and transfection experiments.

RESULTS

Lipoplexes were observed in the acceptor compartments. However, the percent of diffused lipoplexes was low: 0.05/% +/- 0.01%. It was found that both steric obstruction by the sputa as well as the long" distance the lipoplexes have to travel were responsible for this low transport. Surprisingly, the transport occurred better through more viscoelastic sputa. The DNA in the CF sputa also retarded the transport, which was attributed to aggregation of the lipoplexes by the DNA. Finally, rhDNase I moderately enhanced the diffusion of lipoplexes.

CONCLUSIONS

CF sputum drastically retards the diffusion of lipoplexes. DNA in the sputa aggregates the lipoplexes. This may lower the transport of lipoplexes through the sputa and gene expression. Pretreatment of CF patients with rhDNase I may enhance the efficiency of CF gene therapy, as it allows a better transport of the lipoplexes through the sputum and as it partly removes the sputum which will result in a thinner sputum layer on top of the epithelial cells.

Partial correction of endogenous DeltaF508 CFTR in human cystic fibrosis airway epithelia by spliceosome-mediated RNA trans-splicing

Spliceosome-mediated RNA trans-splicing (SMaRT) was investigated as a means for functionally correcting endogenous DeltaF508 cystic fibrosis transmembrane conductance regulator (CFTR) transcripts using in vitro human cystic fibrosis (CF) polarized airway epithelia and in vivo human CF bronchial xenografts. Recombinant adenovirus (Ad.CFTR-PTM) encoding a pre-therapeutic molecule (PTM) targeted to CFTR intron 9 corrected transepithelial cyclic AMP (cAMP)-sensitive short-circuit current (Isc) in DeltaF508 homozygous epithelia to a level 16% of that observed in normal human bronchial epithelia. Molecular analyses using RT-PCR and western blotting confirmed SMaRT-mediated partial correction of endogenous DeltaF508 messenger RNA (mRNA) transcripts and protein. In an in vivo model of DeltaF508 CF airway epithelia, human CF bronchial xenografts infected with Ad.CFTR-PTM also demonstrated partial correction of CFTR-mediated Cl- permeability at a level 22% of that seen in non-CF xenografts. These results provide functional evidence for SMaRT-mediated repair of mutant endogenous CFTR mRNA in intact polarized CF airway epithelial models.

Cystic fibrosis: a brief look at some highlights of a decade of research focused on elucidating and correcting the molecular basis of the disease

The disease Cystic Fibrosis (CF) is caused by mutations in the protein called CFTR, cystic fibrosis transmembrane conductance regulator, an ABC-transporter-like protein found in the plasma membrane of animal cells. CFTR is believed to function primarily as a Cl- channel, but evidence is mounting that this protein has other roles as well. Structurally, CFTR consists of a single polypeptide chain (1480 amino acids) that folds into 5 distinct domains. These include 2 transmembrane domains that are involved in channel formation; 2 nucleotide-binding domains (NBF1 and NBF2), the first of which clearly binds and hydrolyzes ATP; and 1 regulatory domain (R) that is phosphorylated in a cAMP-dependent process. Currently, the 3D structure of neither CFTR nor its domains has been elucidated, although both nucleotide domains have been modeled in 3D, and solution structures in 3D have been obtained for peptide segments of NBF1. The most common mutation causing CF is the deletion (delta) of a single phenylalanine (F) in position 508 within a putative helix located in NBF1. CF patients bearing this deltaF508 mutation frequently experience chronic lung infections, particularly by Pseudomonas aeruginosa, and have a life span that rarely exceeds the age of 30. Since the CFTR gene was cloned and sequenced in 1989, there has been over a decade of research focused on understanding the molecular basis of CF caused by the deltaF508 mutation, with the ultimate objective of using the knowledge gained to carry out additional research designed to correct the underlying defect. In general, this pioneering or "ground roots" research has succeeded according to plan. This brief review summarizes some of the highlights with a focus on those studies conducted in the authors' laboratory. For us, this research has been both exciting and rewarding mainly because the results obtained, despite very limited funding, have provided considerable insight, not only into the chemical, molecular, and pathogenic basis of CF, but have made it possible for us and others to now develop novel, chemically rational, and "cost effective" strategies to identify agents that correct the structural defect in the deltaF508 CFTR protein causing most cases of CF.

Flexible bronchoscopy in molecular biology

Flexible fiberoptic bronchoscopy has allowed researchers to use the bench to bedside approach in the study and therapy of lung diseases. Through bronchoscopy, the lung is a relatively convenient source of samples for the direct evaluation of human gene expression and function. Sampling of respiratory epithelium is performed by brushing with a cytology brush, whereas the epithelial lining fluid and the inflammatory cells in the bronchoalveolar space are obtained by bronchoalveolar lavage. Furthermore, bronchoscopy has been a cornerstone essential to gene therapy trials for lung disease.

Coarse spray delivery to a localized region of the pulmonary airways for gene therapy

Targeting adenoviral vectors for cystic fibrosis gene therapy to the human airways with minimal exposure to alveoli would avoid adverse reactions and maximize response. At present, to deliver gene therapy vectors, large volumes of fluid are instilled or nebulized as aerosols. Either approach would likely cause alveolar exposure and increases the potential for side effects. We describe a coarse spray delivery device that precisely and reproducibly delivers the viral vector to the human airways to treat a small region of the airways for clinical trials. An endoscopic washing pipe (Olympus) that can be inserted into the channel of a bronchoscope was used. To minimize the escape of the therapeutic material downstream from the site of administration, we restricted the volume delivered to <150 microl (to prevent bulk flow), and used large droplets. Their high velocity further enhanced the probability of impaction in the vicinity of the nozzle. A pneumatic dosing system (Kahnetics) was used to reproducibly deliver the spray. The droplet size distribution was determined by laser diffraction and confirmed by cascade impaction: 190-microm volume median diameter with 1% mass <10 microm. The localization of the spray was studied in hollow cast models of human airways. 99mTc-sulfur colloid was used as a radiolabeled marker for these studies. Localization of the deposited spray was determined by scintigraphy and by measuring the radioactivity exiting the terminal airways. In the lung casts the spray was localized to one or two generations over an approximately 2-cm2 area. We conclude that delivery of large droplet sprays limits exposure to a few generations and may be useful in topical gene delivery clinical trials.

Solvoplex: a new type of synthetic vector for intrapulmonary gene delivery

A novel type of synthetic vector, termed solvoplex, is described that can greatly enhance gene expression in lung after intrapulmonary delivery. Solvoplexes consist of plasmid DNA and organic solvents. Several organic solvents were analyzed, and luciferase reporter gene expression was observed after intrapulmonary delivery of solvoplexes containing DPSO (di-n-propylsulfoxide), TMU (tetramethylurea), or BMSO (butylmethylsulfoxide). Expression levels correlated with the amount of solvent used at constant DNA amounts. Highest expression was obtained in the lung after intratracheal injection with 15% DPSO resulting in an increase up to 440-fold compared with DNA alone. DPSO-solvoplexes (15%) gave higher reporter gene expression than polyplexes (ExGen 500) or lipoplexes (DOTAP-cholesterol or DOTAP-DOPE). Solvoplex-mediated gene expression did not depend on the delivery mode, and was observed in both mice and rats. Readministration of DPSO-solvoplexes was possible. A second injection after 4 weeks resulted in expression levels similar to the first administration. Histological analyses using lacZ and GFP reporter genes demonstrated gene expression in the lung airway epithelium after intratracheal and microspray delivery. When luciferase expression levels in lung homogenates were compared with adenovirus vectors, DPSO-solvoplexes were 4- or 100-fold less efficient, depending on the promoter used in the viral vector. A quantitative histological comparison between solvoplexes and adenovirus vectors in the best expressing regions revealed that solvoplexes yielded about 2% LacZ-positive cells in the lung airway epithelium, and adenovirus vectors about 20%. Using the microsprayer system, we demonstrated that DNA remained intact in solvoplexes on spraying and that reporter gene expression was observed in mice after intrapulmonary delivery of a solvoplex spray. DNA in DPSO-solvoplexes remained stable and functional after prolonged storage at room temperature.

Intravenous administration of recombinant adenoviruses causes thrombocytopenia, anemia and erythroblastosis in rabbits

BACKGROUND

Recombinant adenoviruses are highly efficient gene transfer vehicles but their administration to mammals is accompanied by a strong inflammatory response. The present study reports additional side effects observed during adenoviral gene transfer studies in rabbits.

METHODS

Hematological and serological parameters, the course of viremia and the organ distribution were analyzed after in vivo administration of E1-deleted adenoviruses in rabbits.

RESULTS

The systemic administration of a therapeutic dose of 5 x 10(11) infectious particles/kg (infusion time 20 min) led to an average reduction of 80-90% in the platelet count within 48 h. Full recovery took 10-14 days. Virus administration induced a strong but transient erythroblastosis (peaking 24 h after administration) which settled 48 h later. Normochromic anemia occurred over the next 10 days with hemoglobin levels dropping by about 40% to reach the lowest level 10 days after administration and taking two months for full recovery. Dose-dependent thrombocytopenia was also found in mice, but neither erythroblastosis nor anemia was observed (in equivalent doses). The hematological findings did not improve after local injection via the portal vein. Local and systemic administration led to a comparable course of viremia. Only minor differences were found in the biodistribution of viruses between local and systemic administration. Large amounts of viral DNA and transgene expression were found in the lungs, the kidneys and the ovaries, even after local administration via the portal vein.

CONCLUSIONS

Local intravenous injection via the portal vein does not prevent systemic spread of viral vectors and the occurrence of vector-related side effects. The hematological changes observed in rabbits suggest the need for careful monitoring of hematological and rheological parameters in clinical trials.

Targeted adenoviral vectors for cancer gene therapy

The delineation of the molecular basis of cancer allows for the possibility of specific intervention at the molecular level for therapeutic purposes. To this end, viral and nonviral vectors have been designed for delivery and expression of genes into target malignant and non-malignant cells. Gene transfer by available vectors, applied both in the ex vivo and in in vivo contexts, has resulted frequently in the desired cellular phenotypical changes. In this regard, recombinant adenoviruses have been particularly efficient for in vivo gene transfer. Importantly, numerous human clinical protocols using adenoviruses have rapidly entered Phase I clinical trials. However, major vector-related problems remain to be solved before the transfer of therapeutic genes by adenoviruses can become an effective and common place strategy for cancer. An overriding obstacle is the basic ability to deliver therapeutic genes specifically into tumor cells. Here we review a diverse number of advances in adenoviral vectors being developed for overcoming this obstacle. As vector technology fulfills these requirements for obtaining the "targetable-injectable" vector, it is anticipated that promising results already observed in pre-clinical studies will translate quickly into the clinic.

[Mucoviscidosis: therapeutic strategies are multiplying]

Since the cloning of the defective gene in cystic fibrosis, much has been learned on the function of CFTR and on the mechanisms regulating its expression. Based on the current understanding of the processes involved in lung disease progression, a number of approaches have been developed using gene therapy and pharmacological agents. Several of these agents have been reported to restitute a function to CFTR with specific mutations. Other molecules act on channels other than CFTR, and may be effective by bypassing CFTR itself. In the present review the various therapeutical strategies currently investigated are discussed.

The management of young adults with cystic fibrosis: 'genes, jeans and genies'

Cystic fibrosis is now an adult disease. The understanding of the basic pathophysiology of this disease has increased considerably over the past decade. This has resulted in effective management protocols and the development of innovative approaches to therapy. Management of young adults is complex and requires expert medical care delivered in a sensitive and appropriate way. The daily treatment schedule for many adults involves physiotherapy; nebulized, oral and i.v. drugs; exercise and nutritional supplements. Adherence to such treatment while living a busy school, work and social life is extremely difficult for patients. The psychological implications of having a disease with very significant morbidity and mortality also has an enormous impact on individuals with CF. Many of these issues have evolved as survival has increased and the next few decades may produce more unexpected 'genies'. These may be from the disease itself or from some of the exciting new treatments currently being developed. It is important that individuals with CF are fully involved in decisions relating to their treatment and that CF teams provide optimal and appropriate care to enable these young adults to enjoy their lives to the fullest extent.

Gene therapy. Is the future here yet?

Despite the overwhelming number of articles on gene therapy that have been published in the last few years, there is a paucity of trials that have successfully demonstrated the clinical usefulness of this modality. The enthusiasm characterizing some of the earlier studies has given way to a more realistic approach. The next step is to develop more efficient vectors for effective targeting and persistent gene expression.

Aerosol administration of a recombinant adenovirus expressing CFTR to cystic fibrosis patients: a phase I clinical trial

Ad CFTR, a replication-deficient adenovirus expressing the human cystic fibrosis transmembrane conductance regulator (CFTR), was administered by aerosolization in a single escalating dose to three pairs (cohorts) of cystic fibrosis (CF) patients. Buffer only was administered to the nose and lungs 9-14 days before nasal instillation of virus followed the day after by aerosolization of Ad CFTR to the lung. Nasal doses (defined in terms of viral plaque forming units, pfu) were 10(5), 10(7), and 4 x 10(8), whereas aerosolized doses were 10(7), 10(8), 5.4 x 10(8) for each cohort, respectively. No acute toxic effects were observed in the first 4 weeks after virus treatment. Shedding of infectious Ad CFTR was never detected, whereas detection of vector DNA sequences and CFTR expression demonstrated DNA transfer to the nose and airways of patients. No significant deviations in immunological and inflammatory parameters were observed in serum and in bronchoalveolar lavage (BAL). Importantly, for all patients, the serum anti-adenovirus antibody levels did not change significantly from baseline and no antibodies against adenovirus were found in BAL.

Potential of preventing Pseudomonas aeruginosa lung infections in cystic fibrosis patients: experimental studies in animals

In patients with cystic fibrosis (CF), respiratory tract infections caused by Staphylococcus aureus and Haemophilus influenzae are followed by Pseudomonas aeruginosa with increasing age. Chronic endobronchial lung infection with P. aeruginosa is the leading cause of morbidity and mortality. In Danish CF patients we noted that both onset of initial colonization and chronic lung infection with P. aeruginosa peaked during the winter months which is the season for respiratory virus infections. Virus may therefore pave the way for P. aeruginosa. We established a chronic P. aeruginosa lung infection in rats by embedding mucoid bacteria in seaweed alginate and installing the beads intratracheally into the lower part of the left lung. Although the rats did not suffer from CF, the antibody responses and the pathologic changes of the lungs mimicked the findings in CF patients. By using this model in normal and athymic rats we showed that the T-cell response during the "natural" course of the infection played no major role. In a model of acute P. aeruginosa pneumonia we found that the macroscopic inflammatory response of the lungs was immense and that the natural capacity to clear P. aeruginosa was very efficient and could not be improved by immunization, although high serum levels of IgM, IgG and IgA antibodies to P. aeruginosa alginate, LPS, exotoxin A and sonicate were induced. We developed a method for collecting and measuring IgA in saliva and noted that mucosal IgA antibodies were induced by vaccination; they did not significantly prevent inflammation, however. In the chronic rat model we succeeded to improve the survival significantly and to change the inflammatory response subsequent to vaccination from an acute type inflammation dominated by polymorphonuclear leukocytes (PMNs) as in CF patients to a chronic type inflammation dominated by mononuclear leukocytes. Furthermore, we found that rats immunized with an alginate containing vaccine had a significantly earlier cellular shift to a chronic type inflammation as well as a significant reduction in the severity of the macroscopic inflammation compared to two other vaccine groups and to nonimmunized controls. Similar results were obtained in rats treated with the TH1 cytokine, interferon-gamma (IFN-gamma). Several authors have shown that the lung tissue damage during chronic infection in CF patients is caused by a type III hypersensitivity reaction leading to release of elastase by PMNs surrounding the bacterial microcolonies. The cellular shift we have induced by vaccination and by IFN-gamma treatment therefore offers a possible new strategy for improving the clinical course in chronically infected CF patients.

Modification of nasal epithelial potential differences of individuals with cystic fibrosis consequent to local administration of a normal CFTR cDNA adenovirus gene transfer vector

Mutations in the cystic fibrosis transmembrane conductance regulator gene (CFTR) manifest on the nasal epithelial surface of individuals with cystic fibrosis (CF) by Na+ hyperabsorption and diminished beta-agonist-induced Cl- conductance, resulting in an abnormal bioelectric phenotype across the nasal epithelium. A clinical trial was conducted to determine if a replication-deficient, recombinant adenovirus vector containing a normal copy of the CFTR cDNA (AdCFTR) could, when administered to the nasal epithelium, correct the abnormal bioelectric phenotype. Nine individuals with CF received 2 x 10(5) to 2 x 10(8.5) plaque forming units of AdCFTR to the epithelium of one nostril. Measurements made included: baseline electrical potential difference (PD) between the surface of the nasal epithelium and the interstitial fluid, change in PD in response to amiloride, which inhibits apical Na+ channels, and change in PD in response to isoproterenol in a low Cl- solution, a measure of cAMP-regulated Cl- conductance. The functional integrity of the epithelium was evaluated by the PD response to ATP. Each individual served as their own control with measurements made in the nostril to be treated before AdCFTR administration, and in the contralateral untreated nostril. On the average, in the treated nostril over 2 weeks after the local administration of the adenovirus vector compared to measurements made in the same nostril before treatment, baseline PD decreased toward normal (-53.3 +/- 4.0 to -34.6 +/- 3.4, p = 0.01), response to amiloride decreased toward normal (36.9 +/- 4.7 to 19.7 +/- 3.0, p = 0.02), and response to low Cl- and isoproterenol increased toward normal (-4.5 +/- 1.5 to -9.1 +/- 2.1, p = 0.05). There were no changes in response to ATP (-15.3 +/- 2.7 to -15.8 +/- 1.9, p = 0.39), suggesting that the epithelium remained functionally intact. Importantly, there were no significant changes in measurements made in the untreated nostril. While limited to the nasal epithelium, these data suggest an adenovirus vector can safely deliver sufficient CFTR cDNA function to improve the abnormal CF bioelectric phenotype.