Ann Doherty

Changes in physiological, functional and structural markers of cystic fibrosis lung disease with treatment of a pulmonary exacerbation

Background Clinical trials in cystic fibrosis (CF) have been hindered by the paucity of well characterised and clinically relevant outcome measures. Aim To evaluate a range of conventional and novel biomarkers of CF lung disease in a multicentre setting as a contributing study in selecting outcome assays for a clinical trial of CFTR gene therapy. Methods A multicentre observational study of adult and paediatric patients with CF (>10 years) treated for a physician-defined exacerbation of CF pulmonary symptoms. Measurements were performed at commencement and immediately after a course of intravenous antibiotics. Disease activity was assessed using 46 assays across five key domains: symptoms, lung physiology, structural changes on CT, pulmonary and systemic inflammatory markers. Results Statistically significant improvements were seen in forced expiratory volume in 1 s (p<0.001, n=32), lung clearance index (p<0.01, n=32), symptoms (p<0.0001, n=37), CT scores for airway wall thickness (p<0.01, n=31), air trapping (p<0.01, n=30) and large mucus plugs (p=0.0001, n=31), serum C-reactive protein (p<0.0001, n=34), serum interleukin-6 (p<0.0001, n=33) and serum calprotectin (p<0.0001, n=31). Discussion We identify the key biomarkers of inflammation, imaging and physiology that alter alongside symptomatic improvement following treatment of an acute CF exacerbation. These data, in parallel with our study of biomarkers in patients with stable CF, provide important guidance in choosing optimal biomarkers for novel therapies. Further, they highlight that such acute therapy predominantly improves large airway parameters and systemic inflammation, but has less effect on airway inflammation.

Pre-clinical evaluation of three non-viral gene transfer agents for cystic fibrosis after aerosol delivery to the ovine lung

We use both large and small animal models in our pre-clinical evaluation of gene transfer agents (GTAs) for cystic fibrosis (CF) gene therapy. Here, we report the use of a large animal model to assess three non-viral GTAs: 25 kDa-branched polyethyleneimine (PEI), the cationic liposome (GL67A) and compacted DNA nanoparticle formulated with polyethylene glycol-substituted lysine 30-mer. GTAs complexed with plasmids expressing human cystic fibrosis transmembrane conductance regulator (CFTR) complementary DNA were administered to the sheep lung (n=8 per group) by aerosol. All GTAs gave evidence of gene transfer and expression 1 day after treatment. Vector-derived mRNA was expressed in lung tissues, including epithelial cell-enriched bronchial brushing samples, with median group values reaching 1–10% of endogenous CFTR mRNA levels. GL67A gave the highest levels of expression. Human CFTR protein was detected in small airway epithelial cells in some animals treated with GL67A (two out of eight) and PEI (one out of eight). Bronchoalveolar lavage neutrophilia, lung histology and elevated serum haptoglobin levels indicated that gene delivery was associated with mild local and systemic inflammation. Our conclusion was that GL67A was the best non-viral GTA currently available for aerosol delivery to the sheep lung, led to the selection of GL67A as our lead GTA for clinical trials in CF patients.

Chimeric constructs endow the human CFTR Cl− channel with the gating behavior of murine CFTR

The cystic fibrosis transmembrane conductance regulator (CFTR) is a Cl− channel gated by ATP-driven nucleotide-binding domain (NBD) dimerization. Here we exploit species differences between human and murine CFTR to investigate CFTR channel gating. Using homologous recombination, we constructed human-murine CFTR (hmCFTR) chimeras with sequences from NBD1, NBD2, or the regulatory domain (RD) of human CFTR replaced by the equivalent regions of murine CFTR. The gating behavior of hmRD and human CFTR were indistinguishable, whereas hmNBD1 and hmNBD2 had subtle effects on channel gating, prolonging both burst duration and interburst interval. By contrast, hmNBD1+2, containing both NBDs of murine CFTR, reproduced the gating behavior of the subconductance state of murine CFTR, which has dramatically prolonged channel openings. The CFTR potentiator pyrophosphate (PPi) enhanced human, hmRD, and hmNBD1 CFTR Cl− currents, but not those of hmNBD2, hmNBD1+2, and murine CFTR. By analyzing the rate-equilibrium free-energy relationships of chimeric channels, we obtained snapshots of the conformation of the NBDs during ATP-driven dimerization. Our data demonstrate that the conformation of NBD1 changes before that of NBD2 during channel opening. This finding suggests that NBD dimerization does not proceed by a symmetric tweezer-like motion, but instead in an asymmetric fashion led by NBD1. We conclude that the NBDs of murine CFTR determine the unique gating behavior of its subconductance state, whereas NBD2 controls channel potentiation by PPi.

Preparation for a first-in-man lentivirus trial in patients with cystic fibrosis.

We have recently shown that non-viral gene therapy can stabilise the decline of lung function in patients with cystic fibrosis (CF). However, the effect was modest, and more potent gene transfer agents are still required. Fuson protein (F)/Hemagglutinin/Neuraminidase protein (HN)-pseudotyped lentiviral vectors are more efficient for lung gene transfer than non-viral vectors in preclinical models. In preparation for a first-in-man CF trial using the lentiviral vector, we have undertaken key translational preclinical studies. Regulatory-compliant vectors carrying a range of promoter/enhancer elements were assessed in mice and human air–liquid interface (ALI) cultures to select the lead candidate; cystic fibrosis transmembrane conductance receptor (CFTR) expression and function were assessed in CF models using this lead candidate vector. Toxicity was assessed and ‘benchmarked’ against the leading non-viral formulation recently used in a Phase IIb clinical trial. Integration site profiles were mapped and transduction efficiency determined to inform clinical trial dose-ranging. The impact of pre-existing and acquired immunity against the vector and vector stability in several clinically relevant delivery devices was assessed. A hybrid promoter hybrid cytosine guanine dinucleotide (CpG)- free CMV enhancer/elongation factor 1 alpha promoter (hCEF) consisting of the elongation factor 1α promoter and the cytomegalovirus enhancer was most efficacious in both murine lungs and human ALI cultures (both at least 2-log orders above background). The efficacy (at least 14% of airway cells transduced), toxicity and integration site profile supports further progression towards clinical trial and pre-existing and acquired immune responses do not interfere with vector efficacy. The lead rSIV.F/HN candidate expresses functional CFTR and the vector retains 90–100% transduction efficiency in clinically relevant delivery devices. The data support the progression of the F/HN-pseudotyped lentiviral vector into a first-in-man CF trial in 2017.

Limitations of the murine nose in the development of nonviral airway gene transfer.

A clinical program to assess whether lipid GL67A-mediated gene transfer can ameliorate cystic fibrosis (CF) lung disease is currently being undertaken by the UK CF Gene Therapy Consortium. We have evaluated GL67A gene transfer to the murine nasal epithelium of wild-type and CF knockout mice to assess this tissue as a test site for gene transfer agents. The plasmids used were regulated by either (1) the commonly used short-acting cytomegalovirus promoter/enhancer or (2) the ubiquitin C promoter. In a study of approximately 400 mice with CF, vector-specific CF transmembrane conductance regulator (CFTR) mRNA was detected in nasal epithelial cells of 82% of mice treated with a cytomegalovirus-plasmid (pCF1-CFTR), and 62% of mice treated with an ubiquitin C-plasmid. We then assessed whether CFTR gene transfer corrected a panel of CFTR-specific endpoint assays in the murine nose, including ion transport, periciliary liquid height, and ex vivo bacterial adherence. Importantly, even with the comparatively large number of animals assessed, the CFTR function studies were only powered to detect changes of more than 50% toward wild-type values. Within this limitation, no significant correction of the CF phenotype was detected. At the current levels of gene transfer efficiency achievable with nonviral vectors, the murine nose is of limited value as a stepping stone to human trials.

Role of biophysical parameters on ex vivo and in vivo gene transfer to the airway epithelium by polyethylenimine/albumin complexes

Efficient gene transfer to the airways by nonviral vectors is a function of different parameters, among which the size and the charge of the transfecting particles. The aim of this study was to determine the transfection efficiency of polyethylenimine (PEI)/albumin polyplexes in ex vivo and in vivo models of respiratory epithelium and to correlate it with biophysical characteristics of the particles. Complexes were obtained by adding different amounts of human serum albumin (HSA) to PEI polyplexes preformed in saline. The presence of HSA caused the formation of bigger and more negative polyplexes and increased PEI transfection efficiency in primary respiratory epithelial cells by 4-6-fold. For in vivo administration to the lung, PEI polyplexes were formed in water and optimized with respect to the N/ P ratio. PEI/pC-Luc complexes gave the highest luciferase expression at N/ P 15 when administered through the trachea. At this N/ P ratio, the size and the surface charge of albumin-containing polyplexes were not different as compared with plain PEI polyplexes. Formulation of PEI polyplexes in the presence of HSA or murine serum albumin (MSA) resulted in a 2-fold increase in luciferase expression. In mice treated with PEI or PEI/MSA polyplexes containing the nuclear beta-gal gene, X-gal staining revealed that transfected cells localized at the bronchiolar epithelium and that PEI/MSA transfected four times as many cells as PEI ( p < 0.05). Finally, double administration of PEI/MSA polyplexes resulted in a further enhancement of transfection of the lung. Our data show that serum albumin enhances PEI-mediated gene transfer to airway epithelial cells in vivo, likely facilitating the uptake of polyplexes, and indicate that this formulation would fulfill the requirement of repeated administration, as necessary in chronic lung diseases like cystic fibrosis.

An immunocytochemical assay to detect human CFTR expression following gene transfer

BACKGROUND To assess gene therapy treatment for cystic fibrosis (CF) in clinical trials it is essential to develop robust assays that can accurately detect transgene expression in human airway epithelial cells. Our aim was to develop a reproducible immunocytochemical assay for human CFTR protein which can measure both endogenous CFTR levels and augmented CFTR expression after gene delivery. METHODS We characterised an antibody (G449) which satisfied the criteria for use in clinical trials. We optimised our immunocytochemistry method and identified G449 dilutions at which endogenous CFTR levels were negligible in CF samples, thus enhancing detection of transgenic CFTR protein. After developing a transfection technique for brushed human nasal epithelial cells, we transfected non-CF and CF cells with a clinically relevant CpG-free plasmid encoding human CFTR. RESULTS The optimised immunocytochemistry method gave improved discrimination between CF and non-CF samples. Transfection of a CFTR expression vector into primary nasal epithelial cells resulted in detectable RNA and protein expression. CFTR protein was present in 0.05-10% of non-CF cells and 0.02-0.8% of CF cells. CONCLUSION We have developed a sensitive, clinically relevant immunocytochemical assay for CFTR protein and have used it to detect transgene-expressed CFTR in transfected human primary airway epithelial cells.

P106 Inflammatory markers: data from the UK CF Gene Therapy Consortium Run-In Study

Inflammatory markers in sputum and serum have been used with variable success as outcome measures in interventional studies. Limited data are available on reproducibility of such assays in cystic fibrosis (CF) particularly over a long time period. This study was designed to address this; stable patients (FEV1>40, >10 years age) were recruited into the study which ran over an 18-month period with up to four hospital visits. Patients provided a 24 h sputum collection, for weighing at each visit. Spontaneous sputum was collected at the beginning of each visit; if insufficient sample was obtained, sputum was induced with hypertonic saline. Inflammatory markers were measured in dithiothreitol-processed sputum (total and differential cell counts, IL8 (and other cytokines), calprotectin, neutrophil elastase, myeloperoxidase and extracellular DNA). Blood was collected at each visit for cytokines (IL1β, IL6, IL8, IL10, IL12 (p40) and TNFα) and calprotectin. Data are available from 189 patients at 655 visits. Adequate sputum for analysis was obtained at only 60% of visits. Sputum induction accounted for only 16% of adequate samples. Median and range for each detectable assay are shown below. Serum cytokines IL1β, IL10, IL12 (p40) and TNFα were undetectable at each visit, and IL6 was only detectable in 17% of samples. To assess intra-individual variability the coefficient of variation of results across each visit for each patient is presented. Both sputum and serum assays showed a large range of results at each visit, but the variation for each individual was much higher than the ideal 10%. Serum assays were not able to discriminate between CF and non-CF, apart from calprotectin (CF 10.1(0.8–72.5) vs non-CF 0.40 (0.2–1.12) p<0.001). Due to the difficulty in obtaining sputum samples reliably and the large variability of results between visits in these stable patients, we consider it unlikely that a change due to a new therapy would be detectable. As such, we are not considering sputum inflammatory markers as primary or secondary efficacy endpoints in our multidose gene therapy trial. Serum markers also appear to be of limited use is assessing efficacy but will still be useful for toxicology and safety studies.Abstract P106 Table 1

Magnetofection to enhance transfection efficiency of large genomic context vectors in vitro

It has been proposed that genomic context vectors (GCVs), which contain the endogenous gene locus including regulatory elements and introns, may be useful gene transfer vectors. GCVs continue to be evaluated by in vitro transfection. Here we assessed whether magnetofection improves transfection efficiency of GCVs into C127 cells, a comparatively difficult to transfect mouse mammary epithelial cell line, and compared efficiency to standard lipofection. For this purpose, a 149kb GCV containing parts of the CFTR locus and a CMV-lacZ expression cassette was complexed with Lipofectamine 2000 (Invitrogen, UK) and mixed with TransMAGPEI (Chemicell, Germany), a polyethylenimime (PEI) – coated iron oxide particle. Following exposure to a strong magnet, the complexes are forced into more intimate contact with the cell surface, which may lead to increased cellular uptake. Prior to magnetofection, we optimised the dose and complexing ratio of lipid to GCVs. LacZ expression was optimal with 0.2 μg GCV/well, at a 1:1 w/w ratio (0.2 μg: 4478 ± 539 RLU/mg protein, untransfected: 34.1 ± 12.1 RLU/mg protein; p < 0.001, n = 8). However, gene expression with GCV was 100-fold less (n = 8, p < 0.001) compared to that of a standard CMV-lacZ plasmid (7 kb) at the same dose. Due to its smaller size, 20 times more expression cassettes of 7 kb plasmid were delivered for any given dose by weight of GCV. When the vectors were matched for number of expression cassettes rather than weight, (0.2 μg GCV; 0.01 μg 7kb plasmid) there was no difference in expression, despite their size difference. The optimal GCV formulation was coupled to TransMAGPEI at 1:1 up to 4:1 w/w ratios (TransMAGPEI:DNA). We used a magnetic device consisting of 96 circular disc neodymium-iron-boron magnets (depth = 6 mm, height = 5 mm). The magnet was applied for 15 min. Exposure to the magnetic field increased gene expression moderately (with magnet: 15,753 ± 2387 RLU/mg protein, no magnet: 4455 ± 437 RLU/mg protein; p < 0.001, n = 8). An increase of up to 2 logs was seen when using a lower dose of 0.1 μg GCV/well (with magnet: 9938 ± 1041 RLU/mg protein, no magnet: 92.3 ± 28.6 RLU/mg protein; p < 0.001, n = 8), reaching similar levels as with the higher dose of 0.2 μg. In conclusion, as previously reported for standard-sized plasmids (Plank C. et al, Biol Chem, 2003, 384:737–47) magnetofection did not increase overall levels of recombinant protein attainable with a GCV, but reduced the amount of DNA required per well.

479. KLN-47, a safe lipophosphoramide reagent, efficiently transfects (>100 kb) large plasmids into epithelial cells

Cystic fibrosis (CF) is the most common recessive lethal inherited disorder among Caucasian populations. The genetic basis of cystic fibrosis was resolved in 1989 when the CFTR (cystic fibrosis transmembrane conductance regulator) gene was cloned. Until recently, few CF patients survived childhood and other than transplantation, there is no effective therapy for CF lung disease. The realisation of gene therapy represents the best hope for these patients.