Lentivirus-mediated gene transfer to the respiratory epithelium: a promising approach to gene therapy of cystic fibrosis

Gene Therapy for Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a devastating clinical syndrome that leads to acute respiratory failure and accounts for over 70,000 deaths per year in the United States alone, even prior to the COVID-19 pandemic. While its molecular details have been teased apart and its pathophysiology largely established over the past 30 years, relatively few pharmacological advances in treatment have been made based on this knowledge. Indeed, mortality remains very close to what it was 30 years ago. As an alternative to traditional pharmacological approaches, gene therapy offers a highly controlled and targeted strategy to treat the disease at the molecular level. Although there is no single gene or combination of genes responsible for ARDS, there are a number of genes that can be targeted for upregulation or downregulation that could alleviate many of the symptoms and address the underlying mechanisms of this syndrome. This review will focus on the pathophysiology of ARDS and how gene therapy has been used for prevention and treatment. Strategies for gene delivery to the lung, such as barriers encountered during gene transfer, specific classes of genes that have been targeted, and the outcomes of these approaches on ARDS pathogenesis and resolution will be discussed.

ACE2-lentiviral transduction enables mouse SARS-CoV-2 infection and mapping of receptor interactions

SARS-CoV-2 uses the human ACE2 (hACE2) receptor for cell attachment and entry, with mouse ACE2 (mACE2) unable to support infection. Herein we describe an ACE2-lentivirus system and illustrate its utility for in vitro and in vivo SARS-CoV-2 infection models. Transduction of non-permissive cell lines with hACE2 imparted replication competence, and transduction with mACE2 containing N30D, N31K, F83Y and H353K substitutions, to match hACE2, rescued SARS-CoV-2 replication. Intrapulmonary hACE2-lentivirus transduction of C57BL/6J mice permitted significant virus replication in lung epithelium. RNA-Seq and histological analyses illustrated that this model involved an acute inflammatory disease followed by resolution and tissue repair, with a transcriptomic profile similar to that seen in COVID-19 patients. hACE2-lentivirus transduction of IFNAR-/- and IL-28RA-/- mouse lungs was used to illustrate that loss of type I or III interferon responses have no significant effect on virus replication. However, their importance in driving inflammatory responses was illustrated by RNA-Seq analyses. We also demonstrate the utility of the hACE2-lentivirus transduction system for vaccine evaluation in C57BL/6J mice. The ACE2-lentivirus system thus has broad application in SARS-CoV-2 research, providing a tool for both mutagenesis studies and mouse model development.

Breaching the Delivery Barrier: Chemical and Physical Airway Epithelium Disruption Strategies for Enhancing Lentiviral-Mediated Gene Therapy

The lungs have evolved complex physical, biological and immunological defences to prevent foreign material from entering the airway epithelial cells. These mechanisms can also affect both viral and non-viral gene transfer agents, and significantly diminish the effectiveness of airway gene-addition therapies. One strategy to overcome the physical barrier properties of the airway is to transiently disturb the integrity of the epithelium prior to delivery of the gene transfer vector. In this study, chemical (lysophosphatidylcholine, LPC) and physical epithelium disruption using wire abrasion were compared for their ability to improve airway-based lentiviral (LV) vector mediated transduction and reporter gene expression in rats. When luciferase expression was assessed at 1-week post LV delivery, LPC airway conditioning significantly enhanced gene expression levels in rat lungs, while a long-term assessment in a separate cohort of rats at 12 months revealed that LPC conditioning did not improve gene expression longevity. In rats receiving physical perturbation to the trachea prior to gene delivery, significantly higher LacZ gene expression levels were found when compared to LPC-conditioned or LV-only control rats when evaluated 1-week post gene transfer. This proof-of-principle study has shown that airway epithelial disruption strategies based on physical perturbation substantially enhanced LV-mediated airway gene transfer in the trachea.

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

Cystic fibrosis (CF) is a progressive, chronic and debilitating genetic disease caused by mutations in the CF Transmembrane-Conductance Regulator (CFTR) gene. Unrelenting airway disease begins in infancy and produces a steady deterioration in quality of life, ultimately leading to premature death. While life expectancy has improved, current treatments for CF are neither preventive nor curative. Since the discovery of CFTR the vision of correcting the underlying genetic defect - not just treating the symptoms - has been developed to where it is poised to become a transformative technology. Addition of a properly functioning CFTR gene into defective airway cells is the only biologically rational way to prevent or treat CF airway disease for all CFTR mutation classes. While new gene editing approaches hold exciting promise, airway gene-addition therapy remains the most encouraging therapeutic approach for CF. However, early work has not yet progressed to large-scale clinical trials. For clinical trials to begin in earnest the field must demonstrate that gene therapies are safe in CF lungs; can provide clear health benefits and alter the course of lung disease; can be repeatedly dosed to boost effect; and can be scaled effectively from small animal models into human-sized lungs. Demonstrating the durability of these effects demands relevant CF animal models and accurate and reliable techniques to measure benefit. In this review, illustrated with data from our own studies, we outline recent technological developments and discuss these key questions that we believe must be answered to progress CF airway gene-addition therapies to clinical trials.

Chitosan in Non-Viral Gene Delivery: Role of Structure, Characterization Methods, and Insights in Cancer and Rare Diseases Therapies

Non-viral gene delivery vectors have lagged far behind viral ones in the current pipeline of clinical trials of gene therapy nanomedicines. Even when non-viral nanovectors pose less safety risks than do viruses, their efficacy is much lower. Since the early studies to deliver pDNA, chitosan has been regarded as a highly attractive biopolymer to deliver nucleic acids intracellularly and induce a transgenic response resulting in either upregulation of protein expression (for pDNA, mRNA) or its downregulation (for siRNA or microRNA). This is explained as the consequence of a multi-step process involving condensation of nucleic acids, protection against degradation, stabilization in physiological conditions, cellular internalization, release from the endolysosome ("proton sponge" effect), unpacking and enabling the trafficking of pDNA to the nucleus or the siRNA to the RNA interference silencing complex (RISC). Given the multiple steps and complexity involved in the gene transfection process, there is a dearth of understanding of the role of chitosan's structural features (Mw and degree of acetylation, DA%) on each step that dictates the net transfection efficiency and its kinetics. The use of fully characterized chitosan samples along with the utilization of complementary biophysical and biological techniques is key to bridging this gap of knowledge and identifying the optimal chitosans for delivering a specific gene. Other aspects such as cell type and administration route are also at play. At the same time, the role of chitosan structural features on the morphology, size and surface composition of synthetic virus-like particles has barely been addressed. The ongoing revolution brought about by the recent discovery of CRISPR-Cas9 technology will undoubtedly be a game changer in this field in the short term. In the field of rare diseases, gene therapy is perhaps where the greatest potential lies and we anticipate that chitosans will be key players in the translation of research to the clinic.

Genetic Modification of the Lung Directed Toward Treatment of Human Disease

Genetic modification therapy is a promising therapeutic strategy for many diseases of the lung intractable to other treatments. Lung gene therapy has been the subject of numerous preclinical animal experiments and human clinical trials, for targets including genetic diseases such as cystic fibrosis and α1-antitrypsin deficiency, complex disorders such as asthma, allergy, and lung cancer, infections such as respiratory syncytial virus (RSV) and Pseudomonas, as well as pulmonary arterial hypertension, transplant rejection, and lung injury. A variety of viral and non-viral vectors have been employed to overcome the many physical barriers to gene transfer imposed by lung anatomy and natural defenses. Beyond the treatment of lung diseases, the lung has the potential to be used as a metabolic factory for generating proteins for delivery to the circulation for treatment of systemic diseases. Although much has been learned through a myriad of experiments about the development of genetic modification of the lung, more work is still needed to improve the delivery vehicles and to overcome challenges such as entry barriers, persistent expression, specific cell targeting, and circumventing host anti-vector responses.

Intratympanic Gene Delivery of Antimicrobial Molecules in Otitis Media

Otitis media (OM) in children is clinically important because of its detrimental effects on the development of language and motor coordination and is the most common reason for prescription of antibiotics. A recent bacteriological change in OM pathogens such as emergence of antibiotic resistance and vaccination-mediated pathogenic shift urges us to develop a new non-antibiotic strategy. The middle ear epithelium abundantly secretes a variety of antimicrobial molecules suppressing the viability of the common OM pathogens. Recently, we have demonstrated that the adenoviral vector is able to deliver the β-defensin 2 gene to the middle ear epithelial cells in vitro and in vivo, and adenovirus-mediated overexpression of β-defensin 2 is protective for experimental OM. There are many hurdles limiting successful clinical application of gene delivery to the respiratory epithelium of the tubotympanum; however, intratympanic gene therapy with β-defensin 2 is a promising alternative or adjuvant strategy for the management of OM.

Long-term therapeutic and reporter gene expression in lentiviral vector treated cystic fibrosis mice

BACKGROUND

Persistent reporter gene and cystic fibrosis transmembrane conductance regulator (CFTR) nasal airway gene expression can be achieved with a single lentiviral (LV) gene vector dosing when coupled with a preparatory lysophosphatidylcholine (LPC) airway pre-treatment. In the present study, we characterised the duration of gene expression in individual cystic fibrosis (CF) knockout mice (cftr(tm1unc)) over their lifetimes.

METHODS

CF mouse nasal airways were treated with LV-Rx, a mixture of a therapeutic LV-CFTR gene vector and a LV-luciferase reporter gene vector, after pre-treatment with LPC. Control groups received either PBS sham pre-treatment followed by LV-Rx, or LPC prior to delivery of a LV vector containing no transgene (LV-MT). Airway reporter gene expression was monitored by bioluminescence, and functional CFTR expression was assessed via nasal transepithelial potential difference measurements at regular intervals up to 21 months. The presence of the CFTR transgene in the nasal septa, liver and spleen tissues were assessed by a quantitative polymerase chain reaction. Circulating antibodies to the vector glycoprotein envelope and to the luciferase protein were also measured.

RESULTS

The combined use of LPC and LV gene vectors in the nasal airway produced enhanced and sustained luciferase and CFTR gene expression lasting at least 12 months. Improved survival was also observed in CF knockout mice treated with the LV vector mixture compared to all control CF mouse groups.

CONCLUSIONS

The present study showed that our airway pre-treatment and gene delivery technique resulted in sustained functional CFTR expression and improved survival in CF mice.

Efficient intratracheal delivery of airway epithelial cells in mice and pigs

Cellular therapy via direct intratracheal delivery has gained interest as a novel therapeutic strategy for treating various pulmonary diseases including cystic fibrosis lung disease. However, concerns such as insufficient cell engraftment in lungs and lack of large animal model data remain to be resolved. This study aimed to establish a simple method for evaluating cell retention in lungs and to develop reproducible approaches for efficient cell delivery into mouse and pig lungs. Human lung epithelial cells including normal human bronchial/tracheal epithelial (NHBE) cells and human lung epithelial cell line A549 were infected with pSicoR-green fluorescent protein (GFP) lentivirus. GFP-labeled NHBE cells were delivered via a modified intratracheal cell instillation method into the lungs of C57BL/6J mice. Two days following cell delivery, GFP ELISA-based assay revealed a substantial cell-retention efficiency (10.48 ± 2.86%, n = 7) in mouse lungs preinjured with 2% polidocanol. When GFP-labeled A549 cells were transplanted into Yorkshire pig lungs with a tracheal intubation fiberscope, a robust initial cell attachment (22.32% efficiency) was observed at 24 h. In addition, a lentiviral vector was developed to induce the overexpression and apical localization of cystic fibrosis transmembrane conductance regulator (CFTR)-GFP fusion proteins in NHBE cells as a means of ex vivo CFTR gene transfer in nonprogenitor (relatively differentiated) lung epithelial cells. These results have demonstrated the convenience and efficiency of direct delivery of exogenous epithelial cells to lungs in mouse and pig models and provided important background for future preclinical evaluation of intratracheal cell transplantation to treat lung diseases.

IGF axis and other factors in HPV-related and HPV-unrelated carcinogenesis (review)

The insulin-like growth factor (IGF) axis promotes the growth of cells, tissues and organs. IGF-1 is mainly produced in the liver but is also secreted from local tissues. In the circulation, IGF-1 is bound to insulin-like binding proteins (IGFBPs), and when released it activates the insulin-like growth factor receptor (IGF-1R). The signal is further transmitted by intracellular signaling pathways leading to gene expression that regulates, among others, cell proliferation and survival. This review presents the IGF axis in the context of cell transformation and cancer development. Aspects involving IGF-1 deficiency and protection from cancer are also briefly described. Furthermore, human papillomaviruses (HPVs) interplaying with IGF axis components in cervical cancer development are described. These small dsDNA viruses are divided into low-risk and high-risk HPVs with regard to the potency of their oncogenic actions; they mainly infect epithelial or mucosal cells. Special attention is drawn to expression of two major HPV oncogenes (E6 and E7) initiating and maintaining cervical carcinogenesis, which is a multistep and multifactorial process; therefore, involvement of additional factors such as mitochondrial DNA changes, sex hormones, retinoic and folic acids are also discussed. Finally, IGF axis components and HPV oncogenes as targets in anticancer treatment are presented which include IGF-1R downregulation, RNA interference and anti-HPV therapeutic vaccines. The review concludes that despite an enormous advancement in research on IGF and HPV-related cancers, more molecular studies and clinical trials are needed before commercialized therapies are widely available for oncology patients.

A preliminary step of a novel strategy in suicide gene therapy with lentiviral vector

Background:

One of the challenges in lentiviral vector–based suicide gene therapy by toxin or apoptosis-inducing genes is death of packaging cells. Therefore, the process of production of these lentiviral particles would be stopped in this step. We proposed that insertion of a reverse promoter between R and U5 regions of 5′ long terminal repeat (LTR) in transfer plasmid could be considered as a solution for this problem. But it is not known, whether the insertion of RΔU3 sequence between the promoter and target gene in proviral genome during the life-cycle of lentivirus may interfere whit gene expression in target cells.

Materials and Methods:

These following methods were performed in this study: insertion of RΔU3 sequence in pEGFP-N1 plasmid, evaluation of the expression of eGFP gene after calcium phosphate co-precipitation transfection of pCMV-RΔU3-GFP construction in 293T cells, and quantitative assay of eGFP gene by flow cytometry technique.

Results:

Our results from flow cytometry technique analysis showed that there was no significant difference between the expression of eGFP gene in transfected cells with pEGFP-N1 and pCMV-RΔU3-GFP plasmids (P > 0.05).

Conclusion:

In this step of our strategy, we demonstrated that modification of orientation and location of promoter may overcome some issues in lentiviral suicide gene therapy, especially when toxin or apoptosis-inducing genes are used.

Lentivirus-mediated overexpression of TGF-β inducible early gene 1 inhibits SW1990 pancreatic cancer cell growth

TIEG1 (TGF-β inducible early gene 1) plays a significant role in regulating cell proliferation and apoptosis in various cell types. Previous studies have shown a close relationship between the expression level of TIEG1 and various cancers, including breast, prostate, colorectal and pancreatic cancer. In this study, we up-regulated the gene expression of TIEG1 in SW1990 pancreatic cancer cell line by a lentivirus transfection system and investigated its potential as a therapeutic target for pancreatic cancer. The results showed that lentivirus-mediated overexpression of TIEG1 gene inhibited human pancreatic cancer SW1990 cell proliferation and caused the cell cycle arrest at the G1-phase in vitro. SW1990 cells transduced with lenti-TIEG1 showed significant inhibition of colony formation and cancer cell growth in 3-D culture model. Moreover, overexpression of TIEG1 gene significantly slowed the growth of SW1990 xenografts in nude mice. Taken together, these data provided evidence that overexpression of TIEG1 gene by a lentivirus transfection system led to suppressed human pancreatic cancer cell growth and might therefore be a feasible approach in the clinical management of pancreatic cancer.

Gene therapy: light is finally in the tunnel

After two decades of ups and downs, gene therapy has recently achieved a milestone in treating patients with Leber's congenital amaurosis (LCA). LCA is a group of inherited blinding diseases with retinal degeneration and severe vision loss in early infancy. Mutations in several genes, including RPE65, cause the disease. Using adeno-associated virus as a vector, three independent teams of investigators have recently shown that RPE65 can be delivered to retinal pigment epithelial cells of LCA patients by subretinal injections resulting in clinical benefits without side effects. However, considering the whole field of gene therapy, there are still major obstacles to clinical applications for other diseases. These obstacles include innate and immune barriers to vector delivery, toxicity of vectors and the lack of sustained therapeutic gene expression. Therefore, new strategies are needed to overcome these hurdles for achieving safe and effective gene therapy. In this article, we shall review the major advancements over the past two decades and, using lung gene therapy as an example, discuss the current obstacles and possible solutions to provide a roadmap for future gene therapy research.

Gene and cell therapy for cystic fibrosis: from bench to bedside

Clinical trials in cystic fibrosis (CF) patients established proof-of-principle for transfer of the wild-type cystic fibrosis transmembrane conductance regulator (CFTR) gene to airway epithelial cells. However, the limited efficacy of gene transfer vectors as well as extra- and intracellular barriers have prevented the development of a gene therapy-based treatment for CF. Here, we review the use of new viral and nonviral gene therapy vectors, as well as human artificial chromosomes, to overcome barriers to successful CFTR expression. Pre-clinical studies will surely benefit from novel animal models, such as CF pigs and ferrets. Prenatal gene therapy is a potential alternative to gene transfer to fully developed lungs. However, unresolved issues, including the possibility of adverse effects on pre- and postnatal development, the risk of initiating oncogenic or degenerative processes and germ line transmission require further investigation. Finally, we discuss the therapeutic potential of stem cells for CF lung disease.

Integrase-defective lentiviral-vector-based vaccine: a new vector for induction of T cell immunity

INTRODUCTION

The development of new strategies for the induction of potent and broad immune responses is of high priority in the vaccine field. In this setting, integrase-defective lentiviral vectors (IDLV) represent a new and promising delivery system for immunization purposes.

AREAS COVERED

In this review we describe the development and application of IDLV for vaccination. IDLV are turning out to be a new class of vectors endowed with peculiar characteristics, setting them apart from the parental integration-competent lentiviral vectors. Recent data suggest that IDLV are able to induce strong antigen-specific immune responses in terms of quantity, persistence and quality of CD8(+) T cell response following a single immunization in mice.

EXPERT OPINION

IDLV are a recent acquisition in the field of genetic immunization, thus allowing for the opportunity of further upgrading, including increasing antigen expression and potency of immune response. Based on recent reports showing the potential of IDLV for immunization in mouse models, further development and validation of IDLV, including comparison with other vaccine protocols and use in non-human primate models, are warranted.

Lentiviral airway gene transfer in lungs of mice and sheep: successes and challenges

BACKGROUND

Persistent airway gene expression can be achieved in mouse nasal airway using a vesicular stomatitis virus glycoprotein pseudotyped lentiviral (LV) gene vector in combination with lysophosphatidylcholine (LPC) pretreatment. We have now examined the acute in vivo effects of this combination single-dose method for airway LV gene transfer in mouse and sheep lung.

METHODS

Mouse and sheep lungs were exposed to LPC followed 1 h later with the LV vector. Lungs were processed 7 days later using X-gal detection to measure beta-gal gene expression and identify transduced cell types.

RESULTS

In mouse ciliated conducting airways, LPC pretreatment produced extensive gene transfer that extended from the tracheal dosing site into the bronchi and lower airways. Gene expression was present in both terminally differentiated surface cells and in basal cells. Without LPC pretreatment, transduction was limited to the dosing site. In sheep lung, small-volume bronchoscopic instillation delivery produced localized and low-level transduction near the dosing site. Gene expression was again present in surface and basal cells. Neither alterations in LPC dose parameters, nor larger vector volumes increased the level of transduction.

CONCLUSIONS

These findings are the first to confirm the applicability of LPC pretreatment in the production of extensive lentiviral gene transfer in mouse lung airways. However, improved methodologies to increase transduction efficiency are required for adult sheep lung. The results suggest that continued in vivo development of LPC-enhanced lentiviral gene transfer is needed in the lungs of large animals to establish effective lentiviral gene transfer techniques suited to the treatment of airway disease.

Magnetically guided lentiviral-mediated transduction of airway epithelial cells

BACKGROUND

Lentiviral (LV) vectors are able to only slowly and inefficiently transduce nondividing cells such as those of the airway epithelium. To address this issue, we have exploited the magnetofection technique in in vitro models of airway epithelium.

METHODS

Magnetofectins were formed by noncovalent interaction between LV particles and polycation-coated iron oxide nanoparticles. Efficiency of LV-mediated transduction (as evaluated through green fluorescent protein (GFP) expression by cytofluorimetric analysis) was measured in bronchial epithelial cells in the presence or absence of a magnetic field. Cytotoxicity was evaluated by lactate dehydrogenase (LDH) release; cell monolayer integrity by measurement of transepithelial resistance (TER) and evaluation of correct zonula occludens-1 (ZO-1) localization at tight junctions (TJs) by immunofluorescence and confocal microscopy.

RESULTS

In nonpolarized cells, magnetofectins enhanced LV-mediated transduction at multiplicity of infection (MOI) of 50 up to 3.9-fold upon a 24-h incubation, to levels that approached those achieved at MOI of 200 for LV alone, in the presence or absence of the magnetic field. Magnetofection significantly increased the percentage of transduced cells up to 186-fold already after 15 min of incubation. In polarized cells, magnetofection increased GFP+ cells up to 24-fold compared to LV alone. Magnetofection did not enhance LDH release and slightly altered TER but not ZO-1 localization at the TJs.

CONCLUSIONS

We conclude that magnetofection can facilitate in vitro LV-mediated transduction of airway epithelial cells, in the absence of overt cytotoxicity and maintaining epithelial integrity, by lowering the necessary vector dose and reducing the incubation time required to achieve efficient transduction.

A VSV-G Pseudotyped Last Generation Lentiviral Vector Mediates High Level and Persistent Gene Transfer in Models of Airway Epithelium In Vitro and In Vivo

The aim of this work was to evaluate the efficiency and duration of gene expression mediated by a VSV-G pseudotyped last generation lentiviral (LV) vector. We studied LV efficiency in ex-vivo models of respiratory epithelial cells, obtained from bronchial biopsies and nasal polyps, by GFP epifluorescence and cytofluorimetry. In vivo efficiency and persistence of gene expression was investigated by GFP immunohistochemistry and luciferase activity in lung cryosections and homogenates, respectively, upon intranasal and intratracheal administration protocols in C57Bl/6 mice. Both primary bronchial and nasal epithelial cells were transduced up to 70–80% 72 hr after the LV infection. In vivo nasal luciferase expression was increased by lysophosphatidylcholine pre-treatment of the nose. Conversely, the bronchial epithelium was transduced in the absence of any pre-conditioning treatment and luciferase expression lasted for at least 6 months without any decline. We conclude that a last generation LV vector is a promising gene transfer agent in the target organ of genetic and acquired lung diseases, as in the case of cystic fibrosis.

Stem cell therapy for cystic fibrosis: current status and future prospects

Although cystic fibrosis (CF), an autosomal recessive disease caused by mutations in the gene encoding for the CF transmembrane conductance regulator (CFTR), seems a good candidate for gene therapy, 15 years of intense investigation and a number of clinical trials have not yet produced a viable clinical gene-therapy strategy. In addition, the duration of gene expression has been shown to be limited, only lasting 1-4 weeks. Therefore, alternative approaches involve the search for, and use of, stem cell populations. Bone marrow contains different stem cell types, including hematopoietic stem cells and multipotent mesenchymal stromal cells. Numerous studies have now demonstrated the ability of hematopoietic stem cells and mesenchymal stromal cells to home to the lung and differentiate into epithelial cells of both the conducting airways and the alveolar region. However, engraftment of bone marrow-derived stem cells into the airways is a very inefficient process. Detailed knowledge of the cellular and molecular determinants governing homing to the lung and transformation of marrow cells into lung epithelial cells would benefit this process. Despite a very low level of engraftment of donor cells into the nose and gut, significant CFTR mRNA expression and a measurable level of correction of the electrophysiological defect were observed after transplantation of wild-type marrow cells into CF mice. It is uncertain whether this effect is due to the presence of CFTR-expressing epithelial cells derived from donor cells or to the immunomodulatory role of transplanted cells. Finally, initial studies on the usefulness of umbilical cord blood and embryonic stem cells in the generation of airway epithelial cells will be discussed in this review.

Impact of lentiviral vector-mediated transduction on the tightness of a polarized model of airway epithelium and effect of cationic polymer polyethylenimine

Lentiviral (LV) vectors are promising agents for efficient and long-lasting gene transfer into the lung and for gene therapy of genetically determined pulmonary diseases, such as cystic fibrosis, however, they have not been evaluated for cytotoxicity and impact on the tightness of the airway epithelium. In this study, we evaluated the transduction efficiency of a last-generation LV vector bearing Green Fluorescent Protein (GFP) gene as well as cytotoxicity and tight junction (TJ) integrity in a polarized model of airway epithelial cells. High multiplicities of infection (MOI) showed to be cytotoxic, as assessed by increase in propidium iodide staining and decrease in cell viability, and harmful for the epithelial tightness, as demonstrated by the decrease of transepithelial resistance (TER) and delocalization of occludin from the TJs. To increase LV efficiency at low LV:cell ratio, we employed noncovalent association with the polycation branched 25 kDa polyethylenimine (PEI). Transduction of cells with PEI/LV particles resulted in 2.5–3.6-fold increase of percentage of GFP-positive cells only at the highest PEI:LV ratios (1×10⁷ PEI molecules/transducing units with 50 MOI LV) as compared to plain LV. At this dose PEI/LV transduction resulted in 6.5 ± 2.4% of propidium iodide-positive cells. On the other hand, PEI/LV particles did not determine any alteration of TER and occludin localization. We conclude that PEI may be useful for improving the efficiency of gene transfer mediated by LV vectors in airway epithelial cells, in the absence of high acute cytotoxicity and alteration in epithelial tightness.

Toward gene therapy for cystic fibrosis using a lentivirus pseudotyped with Sendai virus envelopes

Gene therapy for cystic fibrosis (CF) is making encouraging progress into clinical trials. However, further improvements in transduction efficiency are desired. To develop a novel gene transfer vector that is improved and truly effective for CF gene therapy, a simian immunodeficiency virus (SIV) was pseudotyped with envelope proteins from Sendai virus (SeV), which is known to efficiently transduce unconditioned airway epithelial cells from the apical side. This novel vector was evaluated in mice in vivo and in vitro directed toward CF gene therapy. Here, we show that (i) we can produce relevant titers of an SIV vector pseudotyped with SeV envelope proteins for in vivo use, (ii) this vector can transduce the respiratory epithelium of the murine nose in vivo at levels that may be relevant for clinical benefit in CF, (iii) this can be achieved in a single formulation, and without the need for preconditioning, (iv) expression can last for 15 months, (v) readministration is feasible, (vi) the vector can transduce human air-liquid interface (ALI) cultures, and (vii) functional CF transmembrane conductance regulator (CFTR) chloride channels can be generated in vitro. Our data suggest that this lentiviral vector may provide a step change in airway transduction efficiency relevant to a clinical programme of gene therapy for CF.

Nanomedicine for respiratory diseases

Treatment of respiratory diseases and infections has proved to be a challenging task, with the incidence of these ailments increasing worldwide. Nanotechnology-based drug and gene delivery systems offer a possible solution to some of the shortfalls of the current treatment regimen. Nanobased drug delivery systems have revolutionised the field of pharmacotherapy by presenting the ability to alter the pharmacokinetics of the conventional drugs to extend the drug retention time, reduce the toxicity and increase the half-life of the drugs. Delivery of exogenous genes to the airway epithelium in vivo has been limited by several physiological barriers, resulting in the low success rate of these systems. With the advent of nanotechnology, DNA compacted with cationic polymers to produce nanoparticles has exhibited a significant increase in the transfection efficiencies. With nanoparticulate drug/gene delivery systems, specific cells can be targeted by functionalising the polymeric nanoparticles with ligands that allow the particles to dock at a specific site of the cell. In addition, polymeric systems allow for the cargo to be released in a controlled and stimuli-responsive manner. The advantages that nanoparticulate delivery systems present in the treatment of respiratory diseases and infections are summarised in this review.

Lentiviral vectors and cystic fibrosis gene therapy

Cystic fibrosis (CF) is a chronic autosomic recessive syndrome, caused by mutations in the CF Transmembrane Conductance Regulator (CFTR) gene, a chloride channel expressed on the apical side of the airway epithelial cells. The lack of CFTR activity brings a dysregulated exchange of ions and water through the airway epithelium, one of the main aspects of CF lung disease pathophysiology. Lentiviral (LV) vectors, of the Retroviridae family, show interesting properties for CF gene therapy, since they integrate into the host genome and allow long-lasting gene expression. Proof-of-principle that LV vectors can transduce the airway epithelium and correct the basic electrophysiological defect in CF mice has been given. Initial data also demonstrate that LV vectors can be repeatedly administered to the lung and do not give rise to a gross inflammatory process, although they can elicit a T cell-mediated response to the transgene. Future studies will clarify the efficacy and safety profile of LV vectors in new complex animal models with CF, such as ferrets and pigs.

Repeated aerosol delivery of carboxyl-terminal modulator protein suppresses tumor in the lungs of K-rasLA1 mice

RATIONALE

Difficulties in achieving long-term survival of patients with lung cancer treated with conventional therapies suggest that novel approaches are required. Recent advances in aerosol-mediated gene delivery have provided the possibility of an alternative for the safe and effective treatment of lung cancer.

OBJECTIVES

To investigate the repeated effect of carboxyl-terminal modulator protein (CTMP) on multistage lung tumorigenesis. In this study, we addressed this question by studying the effects of lentivirus-based CTMP in the lungs of 9- and 13-week-old K-ras(LA1) mice, a model of lung cancer.

METHODS

An aerosol of lentivirus-based CTMP was delivered into 9- and 13-week-old K-ras(LA1) mice, a model of lung cancer, through a nose-only inhalation system twice a week for 4 weeks. The effects of CTMP on lung cancer progression and Akt-related signals were evaluated.

MEASUREMENTS AND MAIN RESULTS

Long-term repeated delivery of CTMP effectively reduced tumor progression in the lungs at different stages of development. Lentiviral-CTMP inhibited protein synthesis and cell cycle and altered Akt signaling pathway in the lungs of 9-week-old K-ras(LA1) mice, and increased apoptosis was observed in the lungs of 13-week-old K-ras(LA1) mice.

CONCLUSIONS

Long-term repeated viral delivery of CTMP may provide a useful tool for designing lung tumor treatment.

Involvement of glycosaminoglycans in vesicular stomatitis virus G glycoprotein pseudotyped lentiviral vector-mediated gene transfer into airway epithelial cells

BACKGROUND

The involvement of surface molecules in HIV-1-derived lentivirus (LV)-mediated transduction of airway epithelial cells has not been studied so far. The present study aimed to evaluate the role of glycosaminoglycans (GAGs) in gene transfer mediated by a third generation vesicular stomatitis virus G glycoprotein (VSV-G) pseudotyped LV vector in an in vitro model of polarized airway epithelial cells.

METHODS

Human bronchial (16HBE-S1) and tracheal (CFT1-C2) epithelial cells were grown either on plastic or on filters and transduced with the LV vector polypurine tract (PPT)-green fluoresecent protein (GFP). Zonula Occludens (ZO)-1, a marker of tight junction, and GAG localization were assessed by cytofluorimetry and confocal microscopy. Soluble GAGs and removal of cell surface GAGs were used to affect LV-mediated transduction.

RESULTS

Extensive optimization of experimental parameters (presence of polybrene during the infection, the incubation time in the presence of LV particles, period of time intercurring between infection and gene expression analysis) was carried out in plastic-adherent cells. Polybrene resulted to be cytotoxic and was not further used. In CFT1-C2 polarized cells, EGTA treatment determined a 20% decrease in transepithelial resistance, a diminished ZO-1 localization at the tight junction location and a 31% increase in GFP positive cells. Heparane sulfate was distributed evenly on the cell surface. Heparin and soluble chondroitin sulfate A and B inhibited LV-mediated transduction in a dose-dependent fashion. These results were confirmed upon enzymatic removal of GAGs from the cell surface.

CONCLUSIONS

Taken together, these results show that GAGs are involved in VSV-G LV transduction of airway epithelial cells.

CFTR function and prospects for therapy

Mutations in the gene coding for the cystic fibrosis transmembrane conductance regulator (CFTR) epithelial anion channel cause cystic fibrosis (CF). The multidomain integral membrane glycoprotein, a member of the adenine nucleotide-binding cassette (ABC) transporter family, conserved in metazoan salt-transporting tissues, is required to control ion and fluid homeostasis on epithelial surfaces. This review considers different therapeutic strategies that have arisen from knowledge of CFTR structure and function as well as its biosynthetic processing, intracellular trafficking, and turnover.

Lentivirus vector can be readministered to nasal epithelia without blocking immune responses

For many envisioned applications of lentivirus vectors as tools in respiratory biology and therapeutic gene delivery, the efficiency of gene transfer must be improved. We previously demonstrated stable, persistent (>11 months) in vivo expression following a single application of a feline immunodeficiency virus (FIV)-based lentivirus vector (GP64-FIV) to murine nasal epithelia. Here we investigate the efficacy of repeated administration of lentivirus vectors to the airways. Using quantitative bioluminescent imaging, we found that consecutive daily dosing achieved a linear increase in gene expression and greatly increased the number of epithelial cells targeted. Surprisingly, reporter gene expression also increased additively following each of seven doses of FIV delivered over consecutive weeks (1 dose/week), without the development of systemic or local neutralizing antibodies. This approach enhanced expression of both reporter and therapeutic transgenes. Transduction efficiency achieved following a single dose of FIV expressing mouse erythropoietin was insufficient to increase hematocrit, whereas seven consecutive daily doses significantly increased hematocrit. These unexpected results contrast strikingly with findings reported for adenovirus vectors. Prolonged gene expression has been observed in vivo following a single dose of virus vector; however, depending on the application, repeated administration of vector may be necessary to achieve stable, therapeutic gene expression.

Lentiviruses inefficiently incorporate human parainfluenza type 3 envelope proteins

We have previously shown that the envelope glycoproteins of human parainfluenza type 3 (HPIV3), F and HN, are able to pseudotype lentiviruses, but the titers of these viruses are too low for use in clinical gene transfer. In this study we investigated the cause of these low titers. We compared the mRNA and protein expression levels of HN and F in transfected cells and in cells infected with wild-type HPIV3. Transfected cells contained similar levels of HN and F cytosolic mRNA, but fewer cell-surface HN and F proteins (3.8- and 1.3-fold less, respectively), than cells infected with wild-type HPIV3. To increase expression of HN in transfected cells, we codon-optimized HN and used it to transfect lentivirus producer cells. Cell surface expression of HN, as well as the amount of HN incorporated into virus particles, increased two- to threefold. Virus titers increased 1.2- to 6.4-fold, and the transduction efficiency of polarized MDCK cells via their apical surfaces increased 1.4-fold. Interestingly, even though codon optimization improved the expression levels of HN and virus titers, we found that HPIV3 pseudotyped viruses contained about 14-fold fewer envelope proteins than lentiviruses pseudotyped with the amphotropic envelope protein. Taken together, our findings suggest that titers are low, not because virus producer cells express levels of HPIV3 envelope proteins that are too low, but because too few of these proteins are incorporated by the lentiviruses for them to be able to efficiently transduce cells.

Gene delivery to airway epithelial cells in vivo: a direct comparison of apical and basolateral transduction strategies using pseudotyped lentivirus vectors

Lentivirus vectors are being investigated as gene delivery vehicles for cystic fibrosis airway gene therapy. Vesicular stomatitis virus G glycoprotein (VSV-G)-pseudotyped vectors transduce airway epithelia via receptors that are located predominantly on the basolateral surface of the airway epithelium. Effective transduction with VSV-G-pseudotyped vectors requires the use of a pre-treatment that disrupts epithelial tight junctions, allowing access to these basolateral receptors. In contrast, it has been reported that apically targeted lentiviral vectors allow efficient gene transfer in the absence of any pre-treatment. In a direct comparison of transduction by a VSV-G-pseudotyped vector, in combination with a pre-treatment with lysophosphatidylcholine (LPC), and the same vector pseudotyped with the apically targeted baculovirus GP64 envelope (without any pre-treatment), the GP64 vector was found to be significantly less efficient. However, when a pre-treatment with LPC was used the level of transduction with the GP64-pseudotyped lentiviral vector was not significantly different to that resulting from the VSV-G-pseudotyped vector. The cell types transduced with each vector were essentially the same, with the majority of cells transduced being respiratory (ciliated cells). However, unlike the VSV-G-pseudotyped vector, which results in persisting gene expression, transduction with the GP64-pseudotyped vector resulted in gene expression that declined to undetectable levels over six months, whether or not an LPC pre-treatment was used.

Novel Therapies for the Treatment of Cystic Fibrosis: New Developments in Gene and Stem Cell Therapy

Cystic fibrosis (CF) was one of the first target diseases for lung gene therapy. Studies of lung gene transfer for CF have provided many insights into the necessary components of successful gene therapy for lung diseases. Many advancements have been achieved with promising results in vitro and in small animal models. However, studies in primate models and patients have been discouraging despite a large number of clinical trials. This reflects a number of obstacles to successful, sustained, and repeatable gene transfer in the lung. Cell-based therapy with embryonic stem cells and adult stem cells (bone marrow or cord blood), have been investigated recently and may provide a viable therapeutic approach in the future. In this article, the authors review CF pathophysiology with a focus on specific targets in the lung epithelium for gene transfer and summarize the current status and future directions of gene- and cell-based therapies.

Gene therapy for disorders affecting children, progress and potential

For over two decades gene therapy has been actively pursued as a treatment modality for the inherited diseases that affect the paediatric population, however, it is still to make a real impact in the clinic. There are many reasons for this including inadequate technology and a lack of understanding of the biological complexities that impact on the efficiency of gene delivery and its outcomes, both positive and negative. However, recent progress is now addressing these issues and indicates that these problems can be overcome, and that gene therapy will play a significant role in the treatment of at least some of these disorders. This review will first give a short overview of relevant gene delivery technologies, what strategies can be used and which diseases are potential targets for gene therapy, and then illustrate several specific diseases for which gene therapy is actively being developed.

Phage phiC31 integrase-mediated genomic integration and long-term gene expression in the lung after nonviral gene delivery

BACKGROUND

Phage phiC31 integrase has emerged as a potent tool for achieving long-term gene expression in different tissues. The present study investigated the activity of phiC31 integrase in murine lungs.

METHODS

Transfections in murine alveolar epithelial (MLE12) cells were performed with Lipofectamine 2000. For in vivo gene delivery, DNA was complexed with polyethylenimine (PEI) and PEI-DNA complexes were injected intravenously into mice. Expression of luciferase in mice was monitored by in vivo bioluminsecence imaging. Genomic integration and integration into a previously described 'hotspot' were confirmed by polymerase chain reaction (PCR).

RESULTS

phiC31 integrase mediated intramolecular recombination between wild-type attB and attP sites in MLE12 cells. Long-term gene expression could be observed in MLE12 cells in the presence of integrase without any selection pressure. Long-term expression of luciferase after intravenous injection of PEI-DNA complexes could be observed only in the lungs of mice which were co-injected with the integrase-encoding plasmid. Increased amounts of integrase plasmid and administration of a second dose had no effect on the level of luciferase expression achieved with a single dose, which was three orders of magnitude lower than the values observed on 'day 1' post application. Genomic integration of the transgene in the mouse lungs was confirmed by PCR. Seven out of the fifteen treated mice showed integration at the mpsL1 site, a previously described 'hot spot' from liver.

CONCLUSIONS

These results provide evidence for the activity of phiC31 integrase in lungs but also emphasize the need for optimization of the system to maintain long-term gene expression at high levels.

Other medications for aerosol delivery

Although aerosol therapy is most commonly used to treat asthma and COPD, there are a large number of aerosol medications now used or in development for other diseases. Mucoactive agents have long been available by aerosol, but now we have truly effective drugs to improve effective airway clearance including dornase alfa, hyperosmolar saline, and aerosol surfactant. Inhaled antibiotics are available for the treatment of cystic fibrosis, bronchiectasis and other chronic airway infections. With the development of devices that can target aerosol to the deep lung, the opportunity to deliver medications systemically by the aerosol route has become a reality. Insulin, recently approved in the US as aerosol therapy, and other peptides are systemically absorbed from the distal airway and alveolus. Aerosol gene transfer therapy to correct abnormalities associated with cystic fibrosis, primary ciliary dyskinesia and other airway diseases also holds great potential.

Inhibition of cervical cancer cell growth in vitro and in vivo with lentiviral-vector delivered short hairpin RNA targeting human papillomavirus E6 and E7 oncogenes

In this study, we investigated the suppressive effect of a short hairpin RNA delivered by a lentiviral vector (LV-shRNA) against human papillomavirus (HPV) type 18 E6 on the expression of the oncogenes E6 and E7 in cervical cancer HeLa cells both in vitro and in vivo. The LV-shRNA effectively delivered the shRNA to HeLa cells and lead to a dose-dependent reduction of E7 protein and the stabilization of E6 target proteins, p53 and p21. Low-dose infection of HeLa cells with LV-shRNA caused reduced cell growth and the induction of senescence, whereas a high-dose infection resulted in specific cell death via apoptosis. Transplant of HeLa cells infected with a low dose of LV-shRNA into Rag-/- mice significantly reduced the tumor weight, whereas transplant of cells infected with a high dose resulted in a complete loss of tumor growth. Systemic delivery of LV-shRNA into mice with established HeLa cell lung metastases led to a significant reduction in the number of tumor nodules. Our data collectively suggest that lentiviral delivery is an effective way to achieve stable suppression of E6/E7 oncogene expression and induce inhibition of tumor growth both in vitro and in vivo. These results encourage further investigation of this form of RNA interference as a promising treatment for cervical cancer.