Gene Therapy for Cystic Fibrosis Lung Disease: Overcoming the Barriers to Translation to the Clinic

Lentiviral vector gene therapy and CFTR modulators show comparable effectiveness in cystic fibrosis rat airway models

Mutation-agnostic treatments such as airway gene therapy have the potential to treat any individual with cystic fibrosis (CF), irrespective of their CF transmembrane conductance regulator (CFTR) gene variants. The aim of this study was to employ two CF rat models, Phe508del and CFTR knockout (KO), to assess the comparative effectiveness of CFTR modulators and lentiviral (LV) vector-mediated gene therapy. Cells were isolated from the tracheas of rats and used to establish air-liquid interface (ALI) cultures. Phe508del rat ALIs were treated with the modulator combination, elexacaftor-tezacaftor-ivacaftor (ETI), and separate groups of Phe508del and KO tracheal epithelial cells were treated with LV-CFTR followed by differentiation at ALI. Ussing chamber measurements were performed to assess CFTR function. ETI-treated Phe508del ALI cultures demonstrated CFTR function that was 59% of wild-type level, while gene-addition therapy restored Phe508del to 68% and KO to 47% of wild-type level, respectively. Our findings show that rat Phe508del-CFTR protein can be successfully rescued with ETI treatment, and that CFTR gene-addition therapy provides significant CFTR correction in Phe508del and KO ALI cultures to levels that were comparable to ETI. These findings highlight the potential of an LV vector-based gene therapy for the treatment of CF lung disease.

Ultra-fastin vivodirectional dark-field x-ray imaging for visualising magnetic control of particles for airway gene delivery

Objective.Magnetic nanoparticles can be used as a targeted delivery vehicle for genetic therapies. Understanding how they can be manipulated within the complex environment of live airways is key to their application to cystic fibrosis and other respiratory diseases.Approach.Dark-field x-ray imaging provides sensitivity to scattering information, and allows the presence of structures smaller than the detector pixel size to be detected. In this study, ultra-fast directional dark-field synchrotron x-ray imaging was utlilised to understand how magnetic nanoparticles move within a live, anaesthetised, rat airway under the influence of static and moving magnetic fields.Main results.Magnetic nanoparticles emerging from an indwelling tracheal cannula were detectable during delivery, with dark-field imaging increasing the signal-to-noise ratio of this event by 3.5 times compared to the x-ray transmission signal. Particle movement as well as particle retention was evident. Dynamic magnetic fields could manipulate the magnetic particlesin situ. Significance.This is the first evidence of the effectiveness ofin vivodark-field imaging operating at these spatial and temporal resolutions, used to detect magnetic nanoparticles. These findings provide the basis for further development toward the effective use of magnetic nanoparticles, and advance their potential as an effective delivery vehicle for genetic agents in the airways of live organisms.

Construction and application of adenoviral vectors

Adenoviral vectors have been widely used as vaccine candidates or potential vaccine candidates against infectious diseases due to the convenience of genome manipulation, their ability to accommodate large exogenous gene fragments, easy access of obtaining high-titer of virus, and high efficiency of transduction. At the same time, adenoviral vectors have also been used extensively in clinical research for cancer gene therapy and treatment of diseases caused by a single gene defect. However, application of adenovirus also faces a series of challenges such as poor targeting, strong immune response against the vector itself, and they cannot be used repeatedly. It is believed that these problems will be solved gradually with further research and technological development in related fields. Here, we review the construction methods of adenoviral vectors, including "gutless" adenovirus and discuss application of adenoviral vectors as prophylactic vaccines for infectious pathogens and their application prospects as therapeutic vaccines for cancer and other kinds of chronic infectious disease such as human papillomavirus, hepatitis B virus, and hepatitis C virus.

Transduction of Ferret Surface and Basal Cells of Airways, Lung, Liver, and Pancreas via Intratracheal or Intravenous Delivery of Adeno-Associated Virus 1 or 6

Cystic fibrosis (CF) is potentially treatable by gene therapy. Since the identification of the CF gene, preclinical and clinical trials have concentrated on achieving effective gene therapy targeting the lung. However, the lung has proven to be a formidable barrier to successful gene therapy especially for CF, and many clinical trials failed to achieve efficacy. Recent advances in vector design and adeno-associated virus (AAV) serotypes have increased the chances of success. Given that CF is a multi-organ disease, the goal of this study was to test whether a gene therapy approach involving AAV1 or AAV6 vector delivery via the systemic circulation would at the same time overcome the barrier of lung delivery and transduce organs commonly affected by CF. To accomplish this, we sprayed AAV1 containing green fluorescent protein (GFP) into the trachea or injected it intravenously (IV). We also tested AAV6 injected IV. No adverse events were noted. Ferrets were necropsied 30 days after vector delivery. AAV1 or AAV6 vector genomes, messenger RNA (mRNA) expression, and GFP were detected in all the tracheal and lung samples from the treated animals, whether AAV1 was sprayed into the trachea or injected IV or AAV6 was injected IV. Importantly, both surface epithelial and basal cells of the trachea and lung airways were successfully transduced, regardless of which route of delivery or vector serotype used for transduction. We detected also AAV1 and AAV6 vector genomes, mRNA expression, and GFP in the livers and pancreases, particularly in the acinar cells of the pancreatic duct. These data suggest that gene transfer is attainable in the airways, liver, and pancreas using either serotype, AAV1 or AAV6. Given that these same organs are affected in CF, systemic delivery of AAV may be the preferred route of delivery for a gene therapy for CF.

Repeat or single-dose lentiviral vector administration to mouse lungs? It's all about the timing

Lentiviral vectors are attractive delivery vehicles for cystic fibrosis gene therapy owing to their low immunogenicity and ability to integrate into the host cell genome, thereby producing long-term, stable gene expression. Nonetheless, repeat dosing may be required to increase initial expression levels, and/or boost levels when they wane. The primary aim of this study was to determine if repeat dosing of a VSV-G pseudotyped LV vector delivered into mouse lungs is more effective than a single dose. C57Bl/6 mouse lungs were conditioned with lysophosphatidylcholine, followed one-hour later by a LV vector carrying the luciferase reporter gene, using six different short-term (≤1 wk) and long-term (>1 wk) dosing schedules. Luciferase expression was quantified using bioluminescence imaging over 12 months. Most dosing schedules produced detectable bioluminescence over the 12-month period, but the shorter intervals (≤1 wk) produced higher levels of flux than the longest interval (five doses at least 1-month apart). Ex vivo lung analysis at 12 months showed that the estimated mean flux for the group that received two doses 1-week apart was significantly greater than the single dose group and the two groups that received doses over a period greater than 1-week. These results suggest that early consecutive multiple doses are more effective at improving gene expression in mouse lungs at 12 months, than longer repeat dosing intervals.

Perceptions of airway gene therapy for cystic fibrosis

BACKGROUND

Airway gene therapy could produce lasting benefit for cystic fibrosis (CF) lung disease, however patient and public support is critical for successful adoption.

RESEARCH DESIGN AND METHODS

Two separate quantitative online surveys were conducted to examine perceptions towards airway gene therapy for CF among people with CF, their families, and members of the public. Data was collected from a total of 213 participants across both studies, with 43 having a diagnosis of CF, 122 having a family member with CF, and 135 knowing someone with CF.

RESULTS

Participants in both studies displayed positive perceptions towards gene therapy and were supportive of involvement in CF gene therapy trials. Around 50% hoped gene therapy could provide a cure. In Study 1 gene therapy was the most important research area, but in Study 2 this was new daily drugs. Almost all thought gene therapy was still required even if modulators already improved quality of life.

CONCLUSION

The factors that influence acceptance, whether trials would be positively viewed, and whether individuals with CF are receptive to gene therapy, are essential to determine prior to clinical trials. Our findings indicate people have positive opinions about airway gene therapy for CF, but further education is vital.

Molecular targets for cystic fibrosis and therapeutic potential of monoclonal antibodies

Cystic fibrosis (CF) is a genetic disease that affects the exocrine glands and is caused by cystic fibrosis transmembrane conductance regulator gene (CFTR) mutations. Lung disease is the leading cause of morbidity in patients. Target-specific treatment of CF has been achieved using monoclonal antibodies (mAbs). The purpose of this article is to discuss the possibility of treating CF with mAbs through their significant target specificity. We searched electronic databases in Web of Science, PubMed, EMBASE, Scopus, and Google Scholar from 1984 to 2021. We discussed the critical role of targeted therapy in cystic fibrosis, as it will be more effective at suppressing the molecular networks. After conducting a critical review of the available literature, we concluded that it is critical to understand the fundamental molecular mechanisms underlying CF prior to incorporating biologics into the therapy regimen. Omalizumab, Mepolizumab, Benralizumab, Dupilumab and KB001-A have been successfully screened for asthma-complicated CF, and their efficacies have been well reported. Despite the availability of effective targeted biologics, treating CF has remained a difficult task, particularly when it comes to reduction of secondary inflammatory mediators. This review emphasizes the overall views on CF, the immunological mechanism of CF, and the prospective therapeutic use of mAbs as potential targeted biologics for enhancing the overall status of human health.

Gene therapy for cystic fibrosis: Challenges and prospects

Cystic fibrosis (CF) is a life-threatening autosomal-recessive disease caused by mutations in a single gene encoding cystic fibrosis transmembrane conductance regulator (CFTR). CF effects multiple organs, and lung disease is the primary cause of mortality. The median age at death from CF is in the early forties. CF was one of the first diseases to be considered for gene therapy, and efforts focused on treating CF lung disease began shortly after the CFTR gene was identified in 1989. However, despite the quickly established proof-of-concept for CFTR gene transfer in vitro and in clinical trials in 1990s, to date, 36 CF gene therapy clinical trials involving ∼600 patients with CF have yet to achieve their desired outcomes. The long journey to pursue gene therapy as a cure for CF encountered more difficulties than originally anticipated, but immense progress has been made in the past decade in the developments of next generation airway transduction viral vectors and CF animal models that reproduced human CF disease phenotypes. In this review, we look back at the history for the lessons learned from previous clinical trials and summarize the recent advances in the research for CF gene therapy, including the emerging CRISPR-based gene editing strategies. We also discuss the airway transduction vectors, large animal CF models, the complexity of CF pathogenesis and heterogeneity of CFTR expression in airway epithelium, which are the major challenges to the implementation of a successful CF gene therapy, and highlight the future opportunities and prospects.

Gene Therapy: Will the Promise of Optimizing Lung Allografts Become Reality?

Lung transplantation is the definitive therapy for patients living with end-stage lung disease. Despite significant progress made in the field, graft survival remains the lowest of all solid organ transplants. Additionally, the lung has among the lowest of organ utilization rates-among eligible donors, only 22% of lungs from multi-organ donors were transplanted in 2019. Novel strategies are needed to rehabilitate marginal organs and improve graft survival. Gene therapy is one promising strategy in optimizing donor allografts. Over-expression or inhibition of specific genes can be achieved to target various pathways of graft injury, including ischemic-reperfusion injuries, humoral or cellular rejection, and chronic lung allograft dysfunction. Experiments in animal models have historically utilized adenovirus-based vectors and the majority of literature in lung transplantation has focused on overexpression of IL-10. Although several strategies were shown to prevent rejection and prolong graft survival in preclinical models, none have led to clinical translation. The past decade has seen a renaissance in the field of gene therapy and two AAV-based in vivo gene therapies are now FDA-approved for clinical use. Concurrently, normothermic ex vivo machine perfusion technology has emerged as an alternative to traditional static cold storage. This preservation method keeps organs physiologically active during storage and thus potentially offers a platform for gene therapy. This review will explore the advantages and disadvantages of various gene therapy modalities, review various candidate genes implicated in various stages of allograft injury and summarize the recent efforts in optimizing donor lungs using gene therapy.

Improved in-vivo airway gene transfer via magnetic-guidance, with protocol development informed by synchrotron imaging

Gene vectors to treat cystic fibrosis lung disease should be targeted to the conducting airways, as peripheral lung transduction does not offer therapeutic benefit. Viral transduction efficiency is directly related to the vector residence time. However, delivered fluids such as gene vectors naturally spread to the alveoli during inspiration, and therapeutic particles of any form are rapidly cleared via mucociliary transit. Extending gene vector residence time within the conducting airways is important, but hard to achieve. Gene vector conjugated magnetic particles that can be guided to the conducting airway surfaces could improve regional targeting. Due to the challenges of in-vivo visualisation, the behaviour of such small magnetic particles on the airway surface in the presence of an applied magnetic field is poorly understood. The aim of this study was to use synchrotron imaging to visualise the in-vivo motion of a range of magnetic particles in the trachea of anaesthetised rats to examine the dynamics and patterns of individual and bulk particle behaviour in-vivo. We also then assessed whether lentiviral-magnetic particle delivery in the presence of a magnetic field increases transduction efficiency in the rat trachea. Synchrotron X-ray imaging revealed the behaviour of magnetic particles in stationary and moving magnetic fields, both in-vitro and in-vivo. Particles could not easily be dragged along the live airway surface with the magnet, but during delivery deposition was focussed within the field of view where the magnetic field was the strongest. Transduction efficiency was also improved six-fold when the lentiviral-magnetic particles were delivered in the presence of a magnetic field. Together these results show that lentiviral-magnetic particles and magnetic fields may be a valuable approach for improving gene vector targeting and increasing transduction levels in the conducting airways in-vivo.

Novel Insights into the Therapeutic Potential of Lung-Targeted Gene Transfer in the Most Common Respiratory Diseases

Over the past decades, a better understanding of the genetic and molecular alterations underlying several respiratory diseases has encouraged the development of new therapeutic strategies. Gene therapy offers new therapeutic alternatives for inherited and acquired diseases by delivering exogenous genetic materials into cells or tissues to restore physiological protein expression and/or activity. In this review, we review (1) different types of viral and non-viral vectors as well as gene-editing techniques; and (2) the application of gene therapy for the treatment of respiratory diseases and disorders, including pulmonary arterial hypertension, idiopathic pulmonary fibrosis, cystic fibrosis, asthma, alpha-1 antitrypsin deficiency, chronic obstructive pulmonary disease, non-small-cell lung cancer, and COVID-19. Further, we also provide specific examples of lung-targeted therapies and discuss the major limitations of gene therapy.

Gene Therapy Knowledge and Attitude Among Healthcare Professionals: A Cross-Sectional Study

This study aimed to assess healthcare professionals' knowledge, attitudes, and concerns toward gene therapy in Saudi Arabia. We conducted an online cross-sectional survey via convenience sampling during the period from December 2018 to March 2019. A total of 419 (358 pharmacists and 61 physicians) responded to our questionnaire. Three hundred and nine (73.7%) were male, and the mean (±SD) age of 32.0 ± 7.7 years. The mean knowledge scores of all participants, pharmacists, and physicians were 3.8 ± 1.9, 3.8 ± 1.9, and 3.7 ± 1.9, respectively (P = 0.73). Higher knowledge score was associated with younger age (Coefficient: -0.03; P = 0.02), male (Coefficient: 0.57; P = 0.01), master's degree (Coefficient: 0.93; P = 0.003) and Ph.D. holders (Coefficient: 1.10; P = 0.01), and participants graduated from Canada (Coefficient: 2.10; P = 0.01).Moreover, about half of the respondents (55%) were concerned about gene therapy, and genetics training at college was considered the best gene therapy education method by 69.4%. Attitude score was not significantly associated with the profession (P = 0.88) but positively correlated with the knowledge score (rho= 0.4; P < 0.001). In conclusion, pharmacists and physicians showed limited knowledge with a positive attitude toward gene therapy. Therefore, educational programs on gene therapy need to be considered, focusing primarily on the safety, and social acceptance of such new therapeutic management.

In vitro optimization of miniature bronchoscope lentiviral vector delivery for the small animal lung

Current gene therapy delivery protocols for small animal lungs typically utilize indirect dose delivery via the nasal airways, or bolus delivery directly into the trachea. Both methods can result in variable transduction throughout the lung, as well as between animals, and cannot be applied in a targeted manner. To minimize variability and improve lung coverage we previously developed and validated a method to visualize and dose gene vectors into pre-selected lobes of rat lungs using a mini-bronchoscope. Lentiviral (LV) vectors are known to be fragile and can be inactivated easily by temperature or the application of shear stresses. There are several ways that the bronchoscope could be configured to deliver the LV vector, and these could result in different amounts of functional LV vector being delivered to the lung. This study evaluated several methods of LV vector delivery through the bronchoscope, and how flow rates and LV vector stabilizing diluents impact LV vector delivery. NIH-3T3 cells were exposed to LV vector containing the green fluorescent protein (GFP) reporter gene using various bronchoscopic delivery techniques and the number of GFP-positive cells produced by each was quantified by flow cytometry. The results showed that directly drawing the LV vector into the bronchoscope tip resulted in 80-90% recovery of viable vector, and was also the simplest method of delivery. The fluid delivery rate and the use of stabilizing serum in the vector diluent had no effect on the viability of the LV vector delivered. These findings can be used to optimize LV vector dose delivery into individual lung lobes of small animal models.

Recent Advances and Challenges in Gene Delivery Mediated by Polyester-Based Nanoparticles

Gene therapy is a promising approach for the treatment of several diseases, such as chronic or viral infections, inherited disorders, and cancer. The cellular internalization of exogenous nucleic acids (NA) requires efficient delivery vehicles to overcome their inherent pharmacokinetic drawbacks, e.g. electrostatic repulsions, enzymatic degradation, limited cellular uptake, fast clearance, etc. Nanotechnological advancements have enabled the use of polymer-based nanostructured biomaterials as safe and effective gene delivery systems, in addition to viral vector delivery methods. Among the plethora of polymeric nanoparticles (NPs), this review will provide a comprehensive and in-depth summary of the polyester-based nanovehicles, including poly(lactic-co-glycolic acid) (PLGA) and polylactic acid (PLA) NPs, used to deliver a variety of foreign NA, e.g. short interfering RNA (siRNA), messenger RNA (mRNA), and plasmid DNA (pDNA). The article will review the versatility of polyester-based nanocarriers including their recent application in the delivery of the clustered, regularly-interspaced, short palindromic repeats/Cas (CRISPR/Cas) genome editing system for treating gene-related diseases. The remaining challenges and future trend of the targeted delivery of this revolutionary genome-editing system will be discussed. Special attention will be given to the pivotal role of nanotechnology in tackling emerging infections such as coronavirus disease 2019 (COVID-19): ground-breaking mRNA vaccines delivered by NPs are currently used worldwide to fight the pandemic, pushing the boundaries of gene therapy.

The Effects of Conditioning and Lentiviral Vector Pseudotype on Short- and Long-Term Airway Reporter Gene Expression in Mice

A gene addition therapy into the conducting airway epithelium is a potential cure for cystic fibrosis lung disease. Achieving sustained lung gene expression has proven difficult due to the natural barriers of the lung. The development of lentiviral (LV) vectors pseudotyped with viral envelopes that have a natural tropism to the airway has enabled persistent gene expression to be achieved in vivo. The aims of this study were to compare the yields of hemagglutinin (HA) and vesicular stomatitis virus-glycoprotein (VSV-G) pseudotyped HIV-1 vectors produced under the same conditions by our standard LV vector production method. We then sought to measure gene expression in mouse airways and to determine whether lysophosphatidylcholine (LPC) conditioning enhances short- and long-term gene expression. C57Bl/6 mouse airways were conditioned with 10 μL of 0.1% LPC or saline control, followed 1 h later by a 30 μL dose of an HA or VSV-G pseudotyped vector carrying either the LacZ or luciferase reporter genes. LacZ expression was assessed by X-gal staining after 7 days, while lung luminescence was quantified regularly for up to 18 months by bioluminescent imaging. The HA pseudotyped vectors had functional titers 25 to 60 times lower than the VSV-G pseudotyped vectors. Conditioning the lung with LPC significantly increased the total number of LacZ-transduced cells for both pseudotypes compared to saline control. Regardless of LPC conditioning, the VSV-G pseudotype produced higher initial levels of gene expression compared to HA. LPC conditioning did not increase the number of transduced basal cells for either pseudotype compared to saline, and was not required for long-term gene expression. Both pseudotyped vectors effectively transduced the upper conducting airways of wild-type mice. The use of LPC conditioning before vector delivery was not required in mouse lungs to produce long-term gene expression, but did improve short-term gene expression.

Towards Human Translation of Lentiviral Airway Gene Delivery for Cystic Fibrosis: A One-Month CFTR and Reporter Gene Study in Marmosets

Gene therapy continues to be a promising contender for the treatment of cystic fibrosis (CF) airway disease. We have previously demonstrated that airway conditioning with lysophosphatidylcholine (LPC) followed by delivery of a HIV-1-based lentiviral (LV) vector functionally corrects the CF transmembrane conductance regulator (CFTR) defect in the nasal airways of CF mice. In our earlier pilot study we showed that our technique can transduce marmoset lungs acutely; this study extends that work to examine gene expression in this nonhuman primate (NHP) 1 month after gene vector treatment. A mixture of three separate HIV-1 vesicular stomatitis virus G (VSV-G)-pseudotyped LV vectors containing the luciferase (Luc), LacZ, and hCFTR transgenes was delivered into the trachea through a miniature bronchoscope. We examined whether a single-dose delivery of LV vector after LPC conditioning could increase levels of transgene expression in the trachea and lungs compared with control (phosphate-buffered saline [PBS]) conditioning. At 1 month, bioluminescence was detected in vivo in the trachea of three of the six animals within the PBS control group, compared with five of the six LPC-treated animals. When examined ex vivo there was weak evidence that LPC improves tracheal Luc expression levels. In the lungs, bioluminescence was detected in vivo in four of the six PBS-treated animals, compared with five of the six LPC-treated animals; however, bioluminescence was present in all lungs when imaged ex vivo. LacZ expression was predominantly observed in the alveolar regions of the lung. hCFTR was detected by qPCR in the lungs of five animals. Basal cells were successfully isolated and expanded from marmoset tracheas, but no LacZ-positive colonies were detected. There was no evidence of an inflammatory response toward the LV vector at 1 month postdelivery, with cytokines remaining at baseline levels. In conclusion, we found weak evidence that LPC conditioning improved gene transduction in the trachea, but not in the marmoset lungs. We also highlight some of the challenges associated with translational lung gene therapy studies in NHPs.

Treatment of Cystic Fibrosis: From Gene- to Cell-Based Therapies

Prognosis of patients with cystic fibrosis (CF) varies extensively despite recent advances in targeted therapies that improve CF transmembrane conductance regulator (CFTR) function. Despite being a multi-organ disease, extensive lung tissue destruction remains the major cause of morbidity and mortality. Progress towards a curative treatment strategy that implements a CFTR gene addition-technology to the patients’ lungs has been slow and not yet developed beyond clinical trials. Improved delivery vectors are needed to overcome the body’s defense system and ensure an efficient and consistent clinical response before gene therapy is suitable for clinical care. Cell-based therapy–which relies on functional modification of allogenic or autologous cells ex vivo, prior to transplantation into the patient–is now a therapeutic reality for various diseases. For CF, pioneering research has demonstrated proof-of-principle for allogenic transplantation of cultured human airway stem cells into mouse airways. However, applying a cell-based therapy to the human airways has distinct challenges. We review CF gene therapies using viral and non-viral delivery strategies and discuss current advances towards autologous cell-based therapies. Progress towards identification, correction, and expansion of a suitable regenerative cell, as well as refinement of pre-cell transplant lung conditioning protocols is discussed.

Will Airway Gene Therapy for Cystic Fibrosis Improve Lung Function? New Imaging Technologies Can Help Us Find Out

The promise of genetic therapies has turned into reality in recent years, with new first-line treatments for fatal diseases now available to patients. The development and testing of genetic therapies for respiratory diseases such as cystic fibrosis (CF) has also progressed. The addition of gene editing to the genetic agent toolbox, and its early success in other organ systems, suggests we will see rapid expansion of gene correction options for CF in the future. Although substantial progress has been made in creating techniques and genetic agents that can be highly effective for CF correction in vitro, physiologically relevant functional in vivo changes have been largely prevented by poor delivery efficiency within the lungs. Somewhat hidden from view, however, is the absence of reliable, accurate, detailed, and noninvasive outcome measures that can detect subtle disease and treatment effects in the lungs of humans or animal models. The ability to measure the fundamental function of the lung-ventilation, the effective transport of air throughout the lung-has been constrained by the available measurement technologies. Without sensitive measurement methods, it is difficult to quantify the effectiveness of genetic therapies for CF. The mainstays of lung health assessment are spirometry, which cannot provide adequate disease localization and is not sensitive enough to detect small early changes in disease; and computed tomography, which provides structural rather than functional information. Magnetic resonance imaging using hyperpolarized gases is increasingly useful for lung ventilation assessment, and it removes the radiation risk that accompanies X-ray methods. A new lung imaging technique, X-ray velocimetry, can now offer highly detailed regional lung ventilation information well suited to the diagnosis, treatment, and monitoring needs of CF lung disease, particularly after the application of genetic therapies. In this review, we discuss the options now available for imaging-based lung function measurement in the generation and use of genetic and other therapies for treating CF lung disease.

Non-viral mediated gene therapy in human cystic fibrosis airway epithelial cells recovers chloride channel functionality

Gene therapy strategies based on non-viral vectors are currently considered as a promising therapeutic option for the treatment of cystic fibrosis (CF), being liposomes the most commonly used gene carriers. Niosomes offer a powerful alternative to liposomes due to their higher stability and lower cytotoxicity, provided by their non-ionic surfactant and helper components. In this work, a three-formulation screening is performed, in terms of physicochemical and biological behavior, in CF patient derived airway epithelial cells. The most efficient niosome formulation reaches 28% of EGFP expressing live cells and follows caveolae-mediated endocytosis. Transfection with therapeutic cystic fibrosis transmembrane conductance regulator (CFTR) gene results in 5-fold increase of CFTR protein expression in transfected versus non-transfected cells, which leads to 1.5-fold increment of the chloride channel functionality. These findings highlight the relevance of niosome-based systems as an encouraging non-viral gene therapy platform with potential therapeutic benefits for CF.

Quantification of muco-obstructive lung disease variability in mice via laboratory X-ray velocimetry

To effectively diagnose, monitor and treat respiratory disease clinicians should be able to accurately assess the spatial distribution of airflow across the fine structure of lung. This capability would enable any decline or improvement in health to be located and measured, allowing improved treatment options to be designed. Current lung function assessment methods have many limitations, including the inability to accurately localise the origin of global changes within the lung. However, X-ray velocimetry (XV) has recently been demonstrated to be a sophisticated and non-invasive lung function measurement tool that is able to display the full dynamics of airflow throughout the lung over the natural breathing cycle. In this study we present two developments in XV analysis. Firstly, we show the ability of laboratory-based XV to detect the patchy nature of cystic fibrosis (CF)-like disease in β-ENaC mice. Secondly, we present a technique for numerical quantification of CF-like disease in mice that can delineate between two major modes of disease symptoms. We propose this analytical model as a simple, easy-to-interpret approach, and one capable of being readily applied to large quantities of data generated in XV imaging. Together these advances show the power of XV for assessing local airflow changes. We propose that XV should be considered as a novel lung function measurement tool for lung therapeutics development in small animal models, for CF and for other muco-obstructive diseases.

Feasibility of Aerosolized Alpha-1 Antitrypsin as a Therapeutic Option

Inhalation therapy is integral in the management of patients with chronic obstructive pulmonary disease (COPD). Specifically, intravenous augmentation therapy is available to patients with alpha-1 antitrypsin deficiency (AATD), although there is insufficient alpha-1 antitrypsin (AAT) delivery to the lungs to modify airways inflammation. In contrast, the inhaled route allows replacement therapy to reach the target site of action and with higher AAT levels. Patients certainly support the inhalation route as an alternative to intravenous injections, obviating repetitive needle insertion and allowing treatment empowerment rather than dependency on traveling to specialized units. The difficulty with inhalation has been the ability to target the formulation to the pathophysiological site of disease: the emphysematous lung parenchyma of the small alveolated airways. Recent advances have suggested nebulizers as being able to deliver an adequate dose, consistently and reproducibly, and, coupled with developments in formulation science, allowed replacement therapy to reach the epithelial lining fluid of the small airways. The bench science has been translated to the first randomized, placebo-controlled clinical trial to study the effects of nebulized AAT, which, although not meeting the primary endpoint of prolonging time to first exacerbation, showed this treatment modality was safe and achievable in a large patient cohort. Indeed, learning from this trial suggests the importance of choosing the right clinical endpoints, and recent key advances in lung physiology indices allow better assessment of the "silent zone" of small airways disease. Knowledge from other respiratory diseases will complement treating patients with AATD, where there is considerable innovation in aerosol science and inhalation medicine directed at utilizing the inhaled route. Indeed, it could be postulated that the inhaled route may not only achieve local pulmonary therapeutic benefit, but through systemic absorption and controlled pharmacokinetic profiling, the formulation may reach and treat liver disease.

Viral Vectors, Animal Models, and Cellular Targets for Gene Therapy of Cystic Fibrosis Lung Disease

After more than two decades since clinical trials tested the first use of recombinant adeno-associated virus (rAAV) to treat cystic fibrosis (CF) lung disease, gene therapy for this disorder has undergone a tremendous resurgence. Fueling this enthusiasm has been an enhanced understanding of rAAV transduction biology and cellular processes that limit transduction of airway epithelia, the development of new rAAV serotypes and other vector systems with high-level tropism for airway epithelial cells, an improved understanding of CF lung pathogenesis and the cellular targets for gene therapy, and the development of new animal models that reproduce the human CF disease phenotype. These advances have created a preclinical path for both assessing the efficacy of gene therapies in the CF lung and interrogating the target cell types in the lung required for complementation of the CF disease state. Lessons learned from early gene therapy attempts with rAAV in the CF lung have guided thinking for the testing of next-generation vector systems. Although unknown questions still remain regarding the cellular targets in the lung that are required or sufficient to complement CF lung disease, the field is now well positioned to tackle these challenges. This review will highlight the role that next-generation CF animal models are playing in the preclinical development of gene therapies for CF lung disease and the knowledge gaps in disease pathophysiology that these models are attempting to fill.

Intratracheal aerosolization of viral vectors to newborn pig airways

Gene therapy for airway diseases requires efficient delivery of nucleic acids to the airways. In small animal models, gene delivery reagents are commonly delivered as a bolus dose. However, large animal models are often more relevant for the transition from preclinical studies to human trials. Aerosolizing viral vectors to the lungs of large animals can maximize anatomical distribution. Here, we describe a technique for aerosolization of viral vectors to the airways of newborn pigs. Briefly, a pig is anesthetized and intubated with an endotracheal tube, and a microsprayer is passed through the endotracheal tube. A fine mist is then sprayed into the distal trachea. Widespread and uniform distribution of transgene expression is critical for developing successful lung gene therapy treatments.

Historically, achieving uniform distribution of a gene therapy reagent in the lungs has been challenging. Here, we describe an aerosolizing technique which can be used to achieve homogenous expression of a viral vector in newborn pig lungs. Briefly, pigs are sedated and intubated with an endotracheal tube, and a microsprayer is used to aerosolize a viral vector which results in its widespread distribution in the lungs.

CFTR Modulators: The Changing Face of Cystic Fibrosis in the Era of Precision Medicine

Cystic fibrosis (CF) is a lethal inherited disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene, which result in impairment of CFTR mRNA and protein expression, function, stability or a combination of these. Although CF leads to multifaceted clinical manifestations, the respiratory disorder represents the major cause of morbidity and mortality of these patients. The life expectancy of CF patients has substantially lengthened due to early diagnosis and improvements in symptomatic therapeutic regimens. Quality of life remains nevertheless limited, as these individuals are subjected to considerable clinical, psychosocial and economic burdens. Since the discovery of the CFTR gene in 1989, tremendous efforts have been made to develop therapies acting more upstream on the pathogenesis cascade, thereby overcoming the underlying dysfunctions caused by CFTR mutations. In this line, the advances in cell-based high-throughput screenings have been facilitating the fast-tracking of CFTR modulators. These modulator drugs have the ability to enhance or even restore the functional expression of specific CF-causing mutations, and they have been classified into five main groups depending on their effects on CFTR mutations: potentiators, correctors, stabilizers, read-through agents, and amplifiers. To date, four CFTR modulators have reached the market, and these pharmaceutical therapies are transforming patients' lives with short- and long-term improvements in clinical outcomes. Such breakthroughs have paved the way for the development of novel CFTR modulators, which are currently under experimental and clinical investigations. Furthermore, recent insights into the CFTR structure will be useful for the rational design of next-generation modulator drugs. This review aims to provide a summary of recent developments in CFTR-directed therapeutics. Barriers and future directions are also discussed in order to optimize treatment adherence, identify feasible and sustainable solutions for equitable access to these therapies, and continue to expand the pipeline of novel modulators that may result in effective precision medicine for all individuals with CF.

Novel therapeutic approaches for the management of cystic fibrosis

Cystic fibrosis (CF) is a genetic condition characterised by the build-up of thick, sticky mucus that can damage many of the body's organs. It is a life-long disease that results in a shortened life expectancy, often due to the progression of advanced lung disease. Treatment has previously targeted the downstream symptoms such as diminished mucus clearance and recurrent infection. More recently, significant advances have been made in treating the cause of the disease by targeting the faulty gene responsible. Hope for the development of potential therapies lies with ongoing research into new pharmacological agents and gene therapy. This review gives an overview of CF, and summarises the current evidence regarding the disease management and upcoming strategies aimed at treating or potentially curing this condition.

Real-time in vivo imaging of regional lung function in a mouse model of cystic fibrosis on a laboratory X-ray source

Most measures of lung health independently characterise either global lung function or regional lung structure. The ability to measure airflow and lung function regionally would provide a more specific and physiologically focused means by which to assess and track lung disease in both pre-clinical and clinical settings. One approach for achieving regional lung function measurement is via phase contrast X-ray imaging (PCXI), which has been shown to provide highly sensitive, high-resolution images of the lungs and airways in small animals. The detailed images provided by PCXI allow the application of four-dimensional X-ray velocimetry (4DxV) to track lung tissue motion and provide quantitative information on regional lung function. However, until recently synchrotron facilities were required to produce the highly coherent, high-flux X-rays that are required to achieve lung PCXI at a high enough frame rate to capture lung motion. This paper presents the first translation of 4DxV technology from a synchrotron facility into a laboratory setting by using a liquid-metal jet microfocus X-ray source. This source can provide the coherence required for PCXI and enough X-ray flux to image the dynamics of lung tissue motion during the respiratory cycle, which enables production of images compatible with 4DxV analysis. We demonstrate the measurements that can be captured in vivo in live mice using this technique, including regional airflow and tissue expansion. These measurements can inform physiological and biomedical research studies in small animals and assist in the development of new respiratory treatments.

Optimization of peptide-plasmid DNA vectors formulation for gene delivery in cancer therapy exploring design of experiments

The field of gene therapy still attracts great interest due to its potential therapeutic effect towards the most deadly diseases, such as cancer. For cancer gene therapy to be feasible and viable in a clinical setting, the design and development of a suitable gene delivery system is imperative. Peptide based vectors, in particular, reveal to be promising for therapeutic gene release. Following this, two different peptides, RALA and WRAP5, have been investigated mainly regarding their ability to form complexes with a p53 encoding plasmid (pDNA) with suitable properties for gene delivery. To address this issue, and after an initial screening study focused on the dependence of pDNA complexation capacity with the nitrogen to phosphate groups (N/P) ratio, a design of experiments (DoE) tool has been employed. For each peptide/pDNA system, parameters such as, the buffer pH and the N/P ratio were considered the DoE inputs and the vector size, zeta potential and pDNA complexation capacity (CC) were monitored as DoE outputs. The main goal was to find the optimal experimental conditions to minimize particle sizes, as well as, to maximize the positive surface charges of the formulated nanosystems and maximize the pDNA CC. Through the DoE method applied, the optimal RALA/pDNA and WRAP5/pDNA formulations were revealed and show interesting features related to peptide structure and pDNA complexation ability. This work illustrates the great utility of experimental design tools in optimizing the formulation of peptide/pDNA vectors in a minimum number of experiments providing relevant knowledge for the development of more suitable and efficient gene delivery systems. The new insights achieved on these carriers clearly instigate deeper research on gene therapy.

Particle coating alters mucociliary transit in excised rat trachea: A synchrotron X-ray imaging study

We have previously developed non-invasive in vivo mucociliary transport (MCT) monitoring methods using synchrotron phase contrast X-ray imaging (PCXI) to evaluate potential therapies for cystic fibrosis (CF). However, previous in vivo measurements of MCT velocity using this method were lower than those from alternate methods. We hypothesise this was due to the surface chemistry of the uncoated particles. We investigated the effect of particle surface coating on MCT marker performance by measuring the velocity of uncoated, positively-charged (aminated; NH₂), and negatively-charged (carboxylated; COOH) particles. The effect of aerosolised hypertonic saline (HS) was also investigated, as previous in vivo measurements showed HS significantly increased MCT rate. PCXI experiments were performed using an ex vivo rat tracheal imaging setup. Prior to aerosol delivery there was little movement of the uncoated particles, whilst the NH₂ and COOH particles moved with MCT rates similar to those previously reported. After application of HS the uncoated and COOH particle velocity increased and NH₂ decreased. This experiment validated the use of COOH particles as MCT marker particles over the uncoated and NH₂ coated particles. Our results suggest that future experiments measuring MCT using synchrotron PCXI should use COOH coated marker particles for more accurate MCT quantification.

Lentiviral Vectors for the Treatment and Prevention of Cystic Fibrosis Lung Disease

Despite the continued development of cystic fibrosis transmembrane conductance regulator (CFTR) modulator drugs for the treatment of cystic fibrosis (CF), the need for mutation agnostic treatments remains. In a sub-group of CF individuals with mutations that may not respond to modulators, such as those with nonsense mutations, CFTR gene transfer to airway epithelia offers the potential for an effective treatment. Lentiviral vectors are well-suited for this purpose because they transduce nondividing cells, and provide long-term transgene expression. Studies in primary cultures of human CF airway epithelia and CF animal models demonstrate the long-term correction of CF phenotypes and low immunogenicity using lentiviral vectors. Further development of CF gene therapy requires the investigation of optimal CFTR expression in the airways. Lentiviral vectors with improved safety features have minimized insertional mutagenesis safety concerns raised in early clinical trials for severe combined immunodeficiency using γ-retroviral vectors. Recent clinical trials using improved lentiviral vectors support the feasibility and safety of lentiviral gene therapy for monogenetic diseases. While work remains to be done before CF gene therapy reaches the bedside, recent advances in lentiviral vector development reviewed here are encouraging and suggest it could be tested in clinical studies in the near future.