Cystic Fibrosis Gene Transfer Research Articles

167. Development of Non-Viral Gene Delivery Systems Deliverable Via Aerosol and Displaying Broad-Spectrum Antibacterial Activity for Cystic Fibrosis Gene Therapy

In cystic fibrosis (CF) patients, bronchopulmonar infections are due to various micro-organisms including Gram(+) (e.g. Staphylococcus aureus) and Gram(-) (e.g. Pseudomonas aeruginosa) bacteria. These can alter CF gene transfer, especially by impairing the DNA to be delivered and the epithelial cells to be transfected. Gene delivery vectors can show some antibacterial activity, an additive property that could be useful for transfecting cells in spite of the presence of bacteria. To date, most of the vectors that we have evaluated can demonstrate strong antibacterial activity against Gram(+) bacteria but little or no against Gram(-) bacteria.

Ex Vivo Adenoviral Vector Gene Delivery Results in Decreased Vector-associated Inflammation Pre- and Post–lung Transplantation in the Pig

Acellular normothermic ex vivo lung perfusion (EVLP) is a novel method of donor lung preservation for transplantation. As cellular metabolism is preserved during perfusion, it represents a potential platform for effective gene transduction in donor lungs. We hypothesized that vector-associated inflammation would be reduced during ex vivo delivery due to isolation from the host immune system response. We compared ex vivo with in vivo intratracheal delivery of an E1-, E3-deleted adenoviral vector encoding either green fluorescent protein (GFP) or interleukin-10 (IL-10) to porcine lungs. Twelve hours after delivery, the lung was transplanted and the post-transplant function assessed. We identified significant transgene expression by 12 hours in both in vivo and ex vivo delivered groups. Lung function remained excellent in all ex vivo groups after viral vector delivery; however, as expected, lung function decreased in the in vivo delivered adenovirus vector encoding GFP (AdGFP) group with corresponding increases in IL-1β levels. Transplanted lung function was excellent in the ex vivo transduced lungs and inferior lung function was seen in the in vivo group after transplantation. In summary, ex vivo delivery of adenoviral gene therapy to the donor lung is superior to in vivo delivery in that it leads to less vector-associated inflammation and provides superior post-transplant lung function.

Novel Cationic Lipids with Enhanced Gene Delivery and Antimicrobial Activity

Cationic lipids facilitate plasmid delivery, and some cationic sterol-based compounds have antimicrobial activity because of their amphiphilic character. These dual functions are relevant in the context of local ongoing infection during intrapulmonary gene transfer for cystic fibrosis. The transfection activities of two cationic lipids, dexamethasone spermine (DS) and disubstituted spermine (D(2)S), were tested as individual components and mixtures in bovine aortic endothelial cells and A549 cells. The results showed a 3- to 7-fold improvement in transgene expression for mixtures of DS with 20 to 40 mol% D(2)S. D(2)S and coformulations with DS, dioleoyl phosphatidylethanolamine, and DNA exhibited potent bactericidal activity against Escherichia coli MG1655, Bacillus subtilis, and Pseudomonas aeruginosa PAO1, which was maintained in bronchoalveolar lavage fluid. Complete bacterial killing was demonstrated at approximately 5 microM, including gene delivery formulations, with 2 orders of magnitude higher tolerance before eukaryotic membrane disruption (erythrocyte hemolysis). D(2)S also exhibited lipopolysaccharide (LPS) scavenging activity resulting in significant inhibition of LPS-mediated activation of human neutrophils with 85 and 65% lower interleukin-8 released at 12 and 24 h, respectively. Mixtures of DS and D(2)S can improve transfection activity over common lipofection reagents, and D(2)S has strong antimicrobial action suited for the suppression of bacterial-mediated inflammation.

Lentiviral transduction of the murine lung provides efficient pseudotype and developmental stage-dependent cell-specific transgene expression

Gene transfer for cystic fibrosis (CF) airway disease has been hampered by the lung's innate refractivity to pathogen infection. We hypothesized that early intervention with an integrating gene transfer vector capable of transducing the lung via the lumen may be a successful therapeutic approach. An HIV-based lentiviral vector pseudotyped with the baculovirus gp64 envelope was applied to the fetal, neonatal or adult airways. Fetal intra-amniotic administration resulted in transduction of approximately 14% of airway epithelial cells, including both ciliated and non-ciliated epithelia of the upper, mid and lower airways; there was negligible alveolar or nasal transduction. Following neonatal intra-nasal administration we observed significant transduction of the airway epithelium (approximately 11%), although mainly in the distal lung, and substantial alveolar transduction. This expression was still detectable at 1 year after application. In the adult, the majority of transduction was restricted to the alveoli. In contrast, vesicular stomatitis virus glycoprotein pseudotyped virus transduced only alveoli after adult and neonatal application and no transduction was observed after fetal administration. Repeat administration did not increase transduction levels of the conducting airway epithelia. These data demonstrate that application at early developmental stages in conjunction with an appropriately pseudotyped virus provides efficient, high-level transgene expression in the murine lung. This may provide a modality for treatment for lung disease in CF.

Expression of CFTR from a ciliated cell-specific promoter is ineffective at correcting nasal potential difference in CF mice

Successful gene therapy will require that the therapeutic gene be expressed at a sufficient level in the correct cell type(s). To improve the specificity of gene transfer for cystic fibrosis (CF) and other airway diseases, we have begun to develop cell-type specific promoters to target the expression of transgenes to specific airway cell types. Using a FOXJ1 promoter construct previously shown to direct transgene expression specifically to ciliated cells, we have generated transgenic mice expressing human cystic fibrosis transmembrane conductance regulator (CFTR) in the murine tracheal and nasal epithelia. RNA analysis demonstrated levels of CFTR expression is greater than or equal to the level of endogenous mouse CFTR. Immunoprecipitation and western blotting demonstrated the production of human CFTR protein, and immunochemistry confirmed that CFTR was expressed in the apical region of ciliated cells. The transgenic animals were bred to CFTR null mice (Cftr(tm1Unc)) to determine if expression of CFTR from the FOXJ1 promoter is capable of correcting the airway defects in Cl(-) secretion and Na(+) absorption that accompany CF. Isolated trachea from neonatal CF mice expressing the FOXJ1/CFTR transgene demonstrated a correction of forskolin-stimulated Cl(-) secretion. However, expression of human CFTR in ciliated cells of the nasal epithelia failed to significantly change the nasal bioelectrics of the CF mice.

Towards an in vitro model of cystic fibrosis small airway epithelium: characterisation of the human bronchial epithelial cell line CFBE41o-

The CFBE41o- cell line was generated by transformation of cystic fibrosis (CF) tracheo-bronchial cells with SV40 and has been reported to be homozygous for the DeltaF508 mutation. A systematic characterisation of these cells, which however, is a pre-requisite for their use as an in vitro model, has not been undertaken so far. Here, we report an assessment of optimal culture conditions, the expression pattern of drug-transport-related proteins and the stability/presence of the CF transmembrane conductance regulator (CFTR) mutation in the gene and gene product over multiple passages. The CFBE41o- cell line was also compared with a wild-type airway epithelial cell line, 16HBE14o-, which served as model for bronchial epithelial cells in situ. The CFBE41o- cell line retains at least some aspects of human CF bronchial epithelial cells, such as the ability to form electrically tight cell layers with functional cell-cell contacts, when grown under immersed (but not air-interfaced) culture conditions. The cell line is homozygous for DeltaF508-CFTR over multiple passages in culture and expresses a number of proteins relevant for pulmonary drug absorption (e.g. P-gp, LRP and caveolin-1). Hence, the CFBE41o- cell line should be useful for studies of CF gene transfer or alternative treatment with small drug molecules and for the gathering of further information about the disease at the cellular level, without the need for primary culture.

Gene transfer of CFTR to airway epithelia: low levels of expression are sufficient to correct Cl−transport and overexpression can generate basolateral CFTR

Gene transfer of CFTR cDNA to airway epithelia is a promising approach to treat cystic fibrosis (CF). Most gene transfer vectors use strong viral promoters even though the endogenous CFTR promoter is very weak. To learn whether expressing CFTR at a low level in a fraction of cells would correct Cl(-) transport, we mixed freshly isolated wild-type and CF airway epithelial cells in varying proportions and generated differentiated epithelia. Epithelia with approximately 20% wild-type cells generated approximately 70% the transepithelial Cl(-) current of epithelia containing 100% wild-type cells. These data were nearly identical to those previously obtained with CFTR expressed under control of a strong promoter in a CF epithelial cell line. We also tested high level CFTR expression using the very strong cytomegalovirus (CMV) promoter as well as the cytokeratin-18 (K18) promoter. In differentiated airway epithelia, the CMV promoter generated 50-fold more transgene expression than the K18 promoter, but the K18 promoter generated more transepithelial Cl(-) current at high vector doses. Using functional studies, we found that with marked overexpression, some CFTR channels were present in the basolateral membrane where they shunted Cl(-) flow, thereby reducing net transepithelial Cl(-) transport. These results suggest that very little CFTR is required in a fraction of CF epithelial cells to complement Cl(-) transport because transepithelial Cl(-) flow is limited at the basolateral membrane. Thus they suggest a broad leeway in promoter strength for correcting the CF gene transfer, although at very high expression levels CFTR may be mislocalized to the basolateral membrane.

A shortened adeno-associated virus expression cassette for CFTR gene transfer to cystic fibrosis airway epithelia.

Adeno-associated viruses (AAVs) such as AAV5 that transduce airway epithelia from the apical surface are attractive vectors for gene transfer in cystic fibrosis (CF). However, their utility in CF has been limited because packaging of the insert becomes inefficient when its length exceeds approximately 4,900-5,000 bp. To partially circumvent this size constraint, we previously developed a CF transmembrane conductance regulator (CFTR) transgene that deleted a portion of the R domain (CFTRDeltaR). In this study, we focused on shortening the other elements in the AAV expression cassette. We found that portions of the CMV immediate/early (CMVie) enhancer/promoter could be deleted without abolishing activity. We also tested various intervening sequences, poly(A) signals, and an intron to develop an expression cassette that meets the size restrictions imposed by AAV. We then packaged these shortened elements with the CFTRDeltaR transgene into AAV5 and applied them to the apical surface of differentiated CF airway epithelia. Two to 4 weeks later, the AAV5 vectors partially corrected the CF Cl(-) transport defect. These results demonstrate that a single AAV vector can complement the CF defect in differentiated airway epithelia and thereby further the development of effective CF gene transfer.

143. Use of Ciliated Cell Specific Promoter FoxJ1 in Gene Transfer Vectors for the Airway Epithelium

Non-viral gene therapy vectors are being developed for Cystic Fibrosis (CF) lung disease. Most CF gene transfer studies employ viral promoters, eg. CMV, that result in high level transgene expression, but become attenuated in vivo leading to rapid loss of expression. Previously we used endogenous polyubiquitin promoter UbC to overcome promoter attenuation in mouse lung (Gill et al, Gene Ther. 8:1539). As well as maintaining persistent transgene expression in vivo, the choice of promoter affects cell specificity of gene expression. In CF the target cells are airway epithelial cells. The use of a cell-specific promoter could boost gene transfer efficacy and reduce potentially deleterious effects of expression in irrelevant cells. Transgenic mice expressing EGFP from the FoxJ1 promoter have been shown to express in ciliated cells in the respiratory epithelium of nose and lung (Ostrowski et al, 2003, Mol. Ther. 8:637). In this study, a 1kb DNA fragment containing the FoxJ1 sequence was used to replace the CMV promoter in luciferase (lux) plasmid pCIKLux, generating pFIKLux. Lux expression was confirmed in vitro following transient transfection into HEK293T cells (pCIKLux: 169.8 54.1 RLU/g; pFIKLux: 208.7 32.5 RLU/g). To evaluate expression in vivo, female BALB/c mice (6–8 weeks) were dosed with 100g of pCIKLux or pFIKLux in 150l water (n=6) via intranasal instillation. In lungs, mean lux activity (24 hours post-dose) was similar from pCIKLux (27.5 19.1 RLU/mg) and pFIKLux (8.6 4.8 RLU/mg, ANOVA, p=0.3427). Lux expression was also similar in nasal epithelium following nasal perfusion (15min) of 200g of pCIKLux or pFIKLux in 100l water (pCIKLux: 24.8 9.5 RLU/mg; pFIKLux: 30.5 18.9 RLU/mg). A plasmid expressing Enhanced Green Fluorescent Protein (EGFP) under the control of the FoxJ1 promoter was constructed to investigate the cell specificity of transgene expression, following delivery to the mouse nose and lung. Whole mouse heads were fixed in paraformaldehyde, decalcified and prepared for cryosection. As a control, delivery of adenovirus expressing EGFP from the CMV promoter (2 1011 viral particles per mouse) resulted in cells of the olfactory epithelium (sustentacular, olfactory receptor) being positive 24hours post-dose. No EGFP+ve cells lining the nasal cavity were observed following delivery of plasmid vectors expressing EGFP. 24hr after lung delivery of 300g of pFIKEGFP in 150l water (n=2) lungs were inflated, fixed and cryosections taken. 180 sections from each animal were examined using fluorescence microscopy, revealing low numbers of GFP+ve cells lining the airway epithelium. No GFP+ve cells were observed in lung parenchyma. Previously, lung administration of pEGFP-N1 (CMV promoter) revealed GFP+ve cells in the both conducting airway epithelial cells (approx. 79%) and parenchymal cells (21%). Antibody co-localisation studies are underway to confirm the epithelial cell types. These studies indicate that reporter expression from the FoxJ1 promoter may not be greatly reduced compared to the CMV promoter, and that cell-specific expression may help restrict transgene expression to the airway epithelium.

Human fetal trachea-scid mouse xenografts: efficacy of vesicular stomatitis virus-G pseudotyped lentiviral-mediated gene transfer

Background/Purpose Postnatal gene transfer in respiratory epithelium has been inefficient, particularly in submucosal gland cells, the target cells for cystic fibrosis transmembrane regulator (CFTR) gene transfer in cystic fibrosis. The authors hypothesized that fetal tracheobronchial epithelium may be more receptive to gene transfer in that precursor cells of the respiratory epithelium may be more accessible. Methods Vesicular stomatitis virus-G (VSV-G) pseudotyped lentiviral vector was first tested in human fetal tracheal organ culture then validated in a human fetal tracheal xenograft model in severe combined immunodeficiency (SCID) mice. Between 7 × 10 7 and 1.6 × 10 8 transducing units of lentiviral vector encoding the transgene LacZ under the control of the human CMV promoter were administered onto the lumenal surface of the xenografts (n = 6). Biopsy specimens were taken from the xenografts at one month (n = 1), 2 months (n = 2), 3 months (n = 1), 6 months (n = 4), and 9 months (n = 1) after vector administration. Analysis of transgene expression was performed on X-gal stained sections. Results Transgene expression was observed in 20.2% to 99% of the surface epithelial cells (mean, 70.8 ± 32.3% SD) and in 28.4% to 99% of the submucosal gland cells (mean, 68.5 ± 26.2% SD) out to 9 months after vector administration in the tracheal xenografts, equivalent to 63 weeks postconceptual age. No staining was seen in the controls. Conclusions Excellent gene transfer in human fetal tracheal xenografts after VSV-G pseudotyped lentiviral vector administration, which may result from more accessible target precursor cells during development, suggests the feasibility of fetal gene therapy for the treatment of congenital airway disease such as cystic fibrosis.

Current status of gene therapy for cystic fibrosis pulmonary disease.

Cystic fibrosis (CF) is a common lethal genetic disorder that affects all ethnic populations; however, it is most prevalent in Caucasians. Intensive basic research over the last 20 years has resulted in a wealth of information regarding the CF gene, its protein product and the mutational basis of disease. This increased understanding has lead to the development of gene therapy for the treatment of CF pulmonary disease. Delivery of the CF gene to the airway requires direct in vivo transfer using vectors encoding for normal CF transmembrane regulator (CFTR) protein. Several vectors are currently available for CF gene transfer and include both viral (adenoviruses, adeno-associated viruses) and non-viral (liposomal) systems. Initial clinical trials with each of these vectors have demonstrated that gene transfer to the CF airway is possible. The efficiency of transfer and duration of expression, however, have been limited. The effects of gene transfer on correction of the basic ion transport defects have also been highly variable and inconsistent, irrespective of the vector. Currently, the risk of severe immunological reactions is the primary factor limiting the clinical advancement of gene therapy. Both the adenoviral and liposomal vectors are associated with significant acute inflammatory reactions. The adenoviruses and adeno-associated viruses also elicit humoral immune responses that significantly reduce the efficiency of transgene expression and increase the risk of readministration. Several strategies are under investigation to improve the efficiency of gene transfer to the CF airway. These include overcoming local barriers in the lung, circumventing the immune response and improving vector internalization and/or uptake. Application of gene transfer in the child and possibly the fetus are also potential future clinical applications of gene therapy. However, despite considerable research with gene therapy, there is little evidence to suggest that a well tolerated and effective gene transfer method is imminent and aggressive use of conventional pharmacological therapies currently offer the greatest promise in the treatment of patients with CF.

Secreted and Transmembrane Mucins Inhibit Gene Transfer with AAV4 More Efficiently than AAV5

Adeno-associated virus (AAV) is a promising vector for gene transfer in cystic fibrosis. AAV4 and AAV5 both bind to the apical surface of differentiated human airway epithelia, but only AAV5 infects. Both AAV4 and AAV5 require 2,3-linked sialic acid for binding. However, AAV5 interacts with sialic acid on N-linked carbohydrates, whereas AAV4 interacts with sialic acid on O-linked carbohydrates. Because mucin is decorated with O-linked carbohydrates, we hypothesized that mucin binds AAV4 and inhibits gene transfer. To evaluate the effect of secreted mucin, we studied mucin binding and gene transfer to COS cells and the basolateral membrane of well differentiated human airway epithelia. AAV4 bound mucin more efficiently than AAV5, and mucin inhibited gene transfer with AAV4. Moreover, O-glycosidase-pretreated mucin did not block gene transfer with AAV4. Similar to secreted mucin, the transmembrane mucin MUC1 inhibited gene transfer with AAV4 but not AAV5. MUC1 inhibited AAV4 by blocking internalization of the virus. Thus, O-linked carbohydrates of mucin are potent inhibitors of AAV4. Furthermore, whereas mucin plays an important role in innate host defense, its activity is specific; some vectors or pathogens are more resistant to its effects.

Cystic fibrosis sputum: a barrier to the transport of nanospheres.

Cystic fibrosis (CF) is characterized by the presence of a viscoelastic mucus layer in the upper airways and bronchi. The underlying problem is a mutation in the gene encoding the cystic fibrosis transmembrane conductance regulator protein. Clinical studies of gene transfer for CF are ongoing. For gene delivery to the airways of CF patients to be effective, the mucus covering the target cells must be overcome. We therefore examined the extent to which CF sputum presents a physical barrier to the transport of nanospheres of a size comparable to that of lipoplexes and other transfection systems currently being clinically evaluated for CF gene therapy. We observed that an extremely low percentage of nanospheres (< 0.3%) moved through a 220-microm-thick CF sputum layer after 150 min. The largest nanospheres studied (560 nm) were almost completely blocked by the sputum, whereas the smaller nanospheres (124 nm) were retarded only by a factor of 1.3 as compared with buffer. Surprisingly, the nanospheres diffused significantly more easily through the more viscoelastic sputum samples. We hypothesize that the structure of the network in sputum becomes more macroporous when the sputum becomes more viscoelastic. Sputum from a patient with chronic obstructive pulmonary disease retarded the transport of nanospheres to the same extent as did CF sputum. When directly mixed with CF sputum, recombinant human deoxyribonuclease I moderately facilitated the transport of nanospheres through CF sputum.

Inhibition of recombinant adeno-associated virus (rAAV) transduction by bronchial secretions from cystic fibrosis patients.

The conducting airways are the primary target for gene transfer in cystic fibrosis (CF), yet the inflammation associated with CF lung disease could potentially pose a significant barrier to gene transfer vectors, such as recombinant adeno-associated virus (rAAV). In order to investigate this possibility, aliquots of bronchoalveolar lavage (BAL) fluid from eight individuals with CF were tested for their in vitro inhibitory effects on rAAV transduction, along with BAL from non-CF individuals. While the non-CF BAL fluid was not inhibitory, seven of eight CF BAL samples had significant inhibitory activity, resulting in a five- to 20-fold reduction in transduction events. Inhibition of rAAV transduction by CF BAL could be reversed by alpha-1-antitrypsin (AAT), but not by DNase. When neutrophil elastase and neutrophil alpha defensins (human neutrophil peptides, HNP) were measured in these samples, they were elevated by 500- and 10,000-fold, respectively. The levels of HNP correlated inversely with the amount of rAAV transduction. Furthermore, rAAV transduction could be blocked by purified HNP in an AAT-reversible manner at HNP concentrations within the range measured in these fluids. We conclude that products of inflammation in CF BAL fluid are inhibitory to rAAV transduction, and that these effects may be reversible by AAT.

Progress in adenovirus-mediated gene therapy for cystic fibrosis lung disease

ObjectiveThe goal of this article was to review the status of gene therapy involving cystic fibrosis (CF), particularly the progress that has been made over the past decade in adenovirus (Ad)-mediated CF lung disease. BackgroundCF is theoretically an ideal disease to use in the study of gene therapy. Over the past decade, considerable progress has been made, with the path from CF gene discovery to clinical application being cleared. Clinical trials, mainly using Ad vectors, have been conducted, involving>200 patients with CF. ConclusionsThe results of the past decade of study have been both encouraging and frustrating. Good evidence exists that there are low levels of CF transmembrane conductance regulator (CFTR) gene transfer and limited evidence of small changes in ion transport. Although Ad vectors are the most advanced method for CF gene transfer to human airways, the current vectors are not yet suitable for in vivo application. The main problem involves the inefficiency of the Ad vectors when they are applied to the apical surface of the airway epithelia. Therefore, further applications of current Ad vectors in gene therapy in vivo will require improvements in efficiency and minimization of the toxicity/inflammatory responses in patients with CF. Although the efficiency of gene transfer is not sufficient to correct the functional defect of CF airways, many strategies to improve this gene transfer are being explored.

Sequential magnetic resonance imaging analysis of the maxillary sinuses: implications for a model of gene therapy in cystic fibrosis.

Serial maxillary sinus aminoglycoside lavage is an adjunctive technique increasingly employed in a variety of areas in cystic fibrosis (CF). It may be helpful in reducing revision rates for sinus surgery, in lowering rates of bronchial pseudomonal colonization after lung transplantation and in the evolving field of gene therapy for CF. The goal of this study was to assess the utility of the maxillary sinus as a model for gene transfer in cystic fibrosis. We performed serial maxillary sinus lavage, in accordance with published protocols, using tobramycin in a randomized series of five CF subjects. Lavage was performed for up to 10 days and sequential magnetic resonance imaging (MRI) scans were taken at zero, 10, 30, 60, 120 and 180 days. The 30 MRI scans were blindly scored by two examiners on the parameters of maxillary sinus aeration, averaged over the five time intervals, was significantly improved (p < 0.05) in the lavaged sinus. This study provides the first systematic image-based measure of efficacy of maxillary sinus aminoglycoside lavage, a major element of a number of clinical protocols used in the treatment of CF. The prolonged increase in aeration after lavage suggests that any further improvement potentially achievable after gene transfer would be difficult to detect, limiting the value of this system as a model of clinical efficacy of gene transfer in CF.

The effect of mucolytic agents on gene transfer across a CF sputum barrier in vitro.

Trials of gene transfer for cystic fibrosis (CF) are currently underway. However, direct application to the airways may be impeded by the presence of airway secretions. We have therefore assessed the effect of CF sputum on the expression of the reporter gene beta-galactosidase complexed with the cationic liposome DC-Chol/DOPE in a number of cell lines in vitro. Transfection was markedly inhibited in the presence of sputum; the effect was concentration dependent and was only partially ameliorated by removal of sputum with phosphate-buffered saline (PBS) washing before gene transfer. However, treatment of the sputum-covered cells with recombinant human DNase (rhDNase, 50 micrograms/ml) but not with N-acetylcysteine, Nacystelyn, lysine (all 20 mM) or recombinant alginase (0.5 U/ml) significantly (P < 0.005) improved gene transfer. Adenovirus-mediated gene transfer efficiency in the presence of sputum was similarly inhibited, and again, treatment with rhDNase before transfection significantly improved gene transfer (P < 0.005). Transfection of Cos 7 cells in the presence of exogenous genomic DNA alone demonstrated similar inhibition to that observed with sputum and was also ameliorated by pre-treatment of DNA-covered cells with rhDNase. In a separate series of experiments performed in the absence of added sputum or genomic DNA, increasing concentrations of rhDNase resulted in a concentration-related decline in transfection efficiency. However, even at the highest concentration (500 micrograms/ml of rhDNase), transfection efficiency remained more than 50% of control. Thus, pre-treatment of CF airways with rhDNase may be appropriate before liposome or adenovirus-mediated gene therapy.

In Vivo Nasal Potential Difference: Techniques and Protocols for Assessing Efficacy of Gene Transfer in Cystic Fibrosis

Cystic fibrosis (CF) is a monogenetic disease that is associated with chronic airways disease and early death. The pulmonary disease reflects mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, and associated abnormal epithelial ion transport, including defective cAMP-mediated (CFTR) Cl- secretion and an accelerated rate of basal Na+ transport. With the development of vectors for gene therapy, the airway epithelium of CF patients has been targeted for studies of gene transfer. The biological efficacy of gene transfer of the normal CFTR cDNA into CF respiratory epithelia can be assessed by in vivo measurements of the transepithelial potential difference (PD), a parameter of ion transport that reflects the expression and function of CFTR. This paper describes techniques that can be used to discriminate in vivo between the ion transport phenotype of normal subjects and patients with cystic fibrosis. Protocols are outlined to allow assessment of individual components of the electrolyte transport phenotype, i.e., the magnitude of the basal and cAMP-mediated (CFTR) Cl- secretion, and the rate of Na+ transport. The physiologic basis of the protocols and important technical features of these measurements are defined. If performed properly, the in vivo nasal PD technique clearly discriminates between normal subjects and cystic fibrosis patients, and can yield estimates of the biological efficacy of gene transfer to achieve correction of the electrolyte transport defects in CF patients.

Adenovirus-mediated gene transfer for cystic fibrosis: Part A. Safety of dose and repeat administration in the nasal epithelium. Part B. Clinical efficacy in the maxillary sinus.

Adenovirus-mediated gene transfer for cystic fibrosis: Part A. Safety of dose and repeat administration in the nasal epithelium. Part B. Clinical efficacy in the maxillary sinus.