Deposition and expression of aerosolized rAAV vectors in the lungs of Rhesus macaques

Combinatorial development of nebulized mRNA delivery formulations for the lungs

Inhaled delivery of mRNA has the potential to treat a wide variety of diseases. However, nebulized mRNA lipid nanoparticles (LNPs) face several unique challenges including stability during nebulization and penetration through both cellular and extracellular barriers. Here we develop a combinatorial approach addressing these barriers. First, we observe that LNP formulations can be stabilized to resist nebulization-induced aggregation by altering the nebulization buffer to increase the LNP charge during nebulization, and by the addition of a branched polymeric excipient. Next, we synthesize a combinatorial library of ionizable, degradable lipids using reductive amination, and evaluate their delivery potential using fully differentiated air-liquid interface cultured primary lung epithelial cells. The final combination of ionizable lipid, charge-stabilized formulation and stability-enhancing excipient yields a significant improvement in lung mRNA delivery over current state-of-the-art LNPs and polymeric nanoparticles.

Influence of lipid composition of messenger RNA-loaded lipid nanoparticles on the protein expression via intratracheal administration in mice

Intratracheal (i.t.) administration, which takes advantage of the specific structure of the respiratory system, can effectively deliver nanoparticles to the lung. Much remains unknown about the i.t. administration of messenger RNA (mRNA)-lipid nanoparticles (LNPs) and the effect of lipid composition. In this study, we administered minute amounts of mRNA-LNP solutions into mice intratracheally and investigated the effect of lipid composition on protein expression in the lungs. We first validated higher protein expression with mRNA-LNP compared to that with mRNA-PEI complex and naked mRNA. Then, we evaluated the influence of lipid composition of LNPs on the protein expression and found that: 1) decreasing the PEG molarity from 1.5% to 0.5% could significantly increase the protein expression; 2) replacing DMG-PEG with DSG-PEG could slightly increase the protein expression; 3) using DOPE instead of DSPC could increase protein expression by an order of magnitude. We successfully prepared an mRNA-LNP with optimal lipid compositions that led to robust protein expression following i.t. administration, thus providing meaningful insights into advanced development of mRNA-LNPs for therapeutic i.t. administration.

AAV2-hAADC (Eladocagene Exuparvovec) Biodistribution and Expression: Superiority of Intraputaminal versus Intracerebroventricular and Intrathecal (Lumbar) Routes of Administration

Aromatic L-amino acid decarboxylase deficiency is a genetic disorder of enzyme loss with decreased neurotransmitter synthesis, and it is characterized by symptoms of impaired motor development and cognitive function, hypotonia, dystonia, and oculogyric crises. Though symptomatic severity varies, the majority of patients experience severe motor impairments, including an inability to sit, stand, or walk. One approved therapy for Aromatic L-amino acid decarboxylase deficiency involves intraputaminal delivery of an adeno-associated virus packaging the human Aromatic L-amino acid decarboxylase enzyme (hAADC) cDNA. The objective of this study in monkeys was to determine the acceptability of ICV/IT as minimally invasive dosing options by evaluating hAADC biodistribution and expression following intraputaminal, intracerebroventricular (ICV), or intrathecal (IT, lumbar) administration. Results show that all routes produced comparable CSF transgene levels and were well-tolerated. The intraputaminal route yielded the highest levels of transgene-derived mRNA expression in the putamen, caudate, and globus pallidus, while expression levels in the spinal cord and dorsal root ganglia (DRG, a target of special toxicological concern) were undetectable. In contrast, the highest transgene levels in ICV/IT groups were observed in the spinal cord and DRG, but levels were too low to result in expression in the putamen, caudate, and globus pallidus. Unlike ICV/IT, the intraputaminal route produced no transgene in blood, suggesting a lower likelihood of off-target toxicities. Additionally, intraputaminal dosing resulted in the lowest anti-AAV2 antibody (anti-drug antibody) levels. Together, these data demonstrate the superiority of intraputaminal administration over ICV/IT routes in achieving AAV2-hAADC transgene DNA distribution and mRNA expression in target therapeutic areas while minimizing risk of toxicity.

Nebulized fusion inhibitory peptide protects cynomolgus macaques from measles virus infection

Measles is the most contagious airborne viral infection and the leading cause of child death among vaccine-preventable diseases. We show here that aerosolized lipopeptide fusion inhibitor, derived from heptad-repeat regions of the measles virus (MeV) fusion protein, blocks respiratory MeV infection in a non-human primate model, the cynomolgus macaque. We use a custom-designed mesh nebulizer to ensure efficient aerosol delivery of peptide to the respiratory tract and demonstrate the absence of adverse effects and lung pathology in macaques. The nebulized peptide efficiently prevents MeV infection, resulting in the complete absence of MeV RNA, MeV-infected cells, and MeV-specific humoral responses in treated animals. This strategy provides an additional means to fight against respiratory infection in non-vaccinated people, that can be readily translated to human trials. It presents a proof-of-concept for the aerosol delivery of fusion inhibitory peptides to protect against measles and other airborne viruses, including SARS-CoV-2, in case of high-risk exposure.

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.

Current knowledge on the tissue distribution of mRNA nanocarriers for therapeutic protein expression

Exogenously delivered mRNA-based drugs are emerging as a new class of therapeutics with the potential to treat several diseases. Over the last decade, advancements in the design of non-viral delivery tools have enabled mRNA to be evaluated for several therapeutic purposes including protein replacement therapies, gene editing, and vaccines. However, in vivo delivery of mRNA to targeted organs and cells remains a critical challenge. Evaluation of the biodistribution of mRNA vehicles is of utmost importance for the development of effective pharmaceutical candidates. In this review, we discuss the recent advances in the design of nanoparticles loaded with mRNA and extrapolate the key factors influencing their biodistribution following administration. Finally, we highlight the latest developments in the preclinical and clinical translation of mRNA therapeutics for protein supplementation therapy.

Inhaled siRNA nanoparticles targeting IL11 inhibit lung fibrosis and improve pulmonary function post-bleomycin challenge

Interleukin-11 (IL-11) is a profibrotic cytokine essential for the differentiation of fibroblasts into collagen-secreting, actin alpha 2, smooth muscle-positive (ACTA2⁺) myofibroblasts, driving processes underlying the pathogenesis of idiopathic pulmonary fibrosis (IPF). Here, we developed an inhalable and mucus-penetrative nanoparticle (NP) system incorporating siRNA against IL11 (siIL11@PPGC NPs) and investigated therapeutic potential for the treatment of IPF. NPs are formulated through self-assembly of a biodegradable PLGA-PEG diblock copolymer and a self-created cationic lipid-like molecule G0-C14 to enable efficient transmucosal delivery of siIL11. Noninvasive aerosol inhalation hindered fibroblast differentiation and reduced ECM deposition via inhibition of ERK and SMAD2. Furthermore, siIL11@PPGC NPs significantly diminished fibrosis development and improved pulmonary function in a mouse model of bleomycin-induced pulmonary fibrosis without inducing systemic toxicity. This work presents a versatile NP platform for the locally inhaled delivery of siRNA therapeutics and exhibits promising clinical potential in the treatment of numerous respiratory diseases, including IPF.

Endo-bronchial aerosolized AAV1.SERCA2a gene therapy in a pulmonary hypertension pig model: addressing the lung delivery bottleneck

A disappointing number of new therapies for pulmonary hypertension (PH) have been successfully translated to the clinic. Adeno-associated viral (AAV) gene therapy has the potential to treat the underlying pathology of PH, but the challenge remains in efficient and safe delivery. The aims of this study were i) to test the efficacy of endo-bronchial aerosolization delivery for AAV1-mediated sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2a (SERCA2a) gene therapy in a PH pig model and ii) to identify the most efficient airway administration modality for in-lung gene therapy in PH. We hypothesized that delivery to the distal bronchi increases lung viral uptake and avoids virus loss in off-target compartments. In part one of the study, PH was induced in pigs by surgically banding the pulmonary veins. Two months post-surgery, 1x1013 viral genomes (vg) of AAV1.SERCA2a or saline was endo-bronchially aerosolized using a bronchoscope. Two months after aerosolization, high vg copies were detected in the lungs, accompanied by functional and morphometrical amelioration of PH. In part two of the study, we directly compared the endo-bronchial aerosolization gene delivery to the intra-tracheal aerosolization in PH pigs. Endo-bronchial delivery demonstrated higher viral expression (6,719 ± 927 vs 1,444 ± 402 vg copy/100ng DNA, p=0.0017), suggesting this delivery modality is a promising method for clinical AAV gene therapy for PH.

Complete Protection Against Yersinia pestis in BALB/c Mouse Model Elicited by Immunization With Inhalable Formulations of rF1-V10 Fusion Protein via Aerosolized Intratracheal Inoculation

Pneumonic plague, caused by Yersinia pestis, is an infectious disease with high mortality rates unless treated early with antibiotics. Currently, no FDA-approved vaccine against plague is available for human use. The capsular antigen F1, the low-calcium-response V antigen (LcrV), and the recombinant fusion protein (rF1-LcrV) of Y. pestis are leading subunit vaccine candidates under intense investigation; however, the inability of recombinant antigens to provide complete protection against pneumonic plague in animal models remains a significant concern. In this study, we compared immunoprotection against pneumonic plague provided by rF1, rV10 (a truncation of LcrV), and rF1-V10, and vaccinations delivered via aerosolized intratracheal (i.t.) inoculation or subcutaneous (s.c.) injection. We further considered three vaccine formulations: conventional liquid, dry powder produced by spray freeze drying, or dry powder reconstituted in PBS. The main findings are: (i) rF1-V10 immunization with any formulation via i.t. or s.c. routes conferred 100% protection against Y. pestis i.t. infection; (ii) rF1 or rV10 immunization using i.t. delivery provided significantly stronger protection than rF1 or rV10 immunization via s.c. delivery; and (iii) powder formulations of subunit vaccines induced immune responses and provided protection equivalent to those elicited by unprocessed liquid formulations of vaccines. Our data indicate that immunization with a powder formulation of rF1-V10 vaccines via an i.t. route may be a promising vaccination strategy for providing protective immunity against pneumonic plague.

Nanotechnologies in Delivery of DNA and mRNA Vaccines to the Nasal and Pulmonary Mucosa

Recent advancements in the field of in vitro transcribed mRNA (IVT-mRNA) vaccination have attracted considerable attention to such vaccination as a cutting-edge technique against infectious diseases including COVID-19 caused by SARS-CoV-2. While numerous pathogens infect the host through the respiratory mucosa, conventional parenterally administered vaccines are unable to induce protective immunity at mucosal surfaces. Mucosal immunization enables the induction of both mucosal and systemic immunity, efficiently removing pathogens from the mucosa before an infection occurs. Although respiratory mucosal vaccination is highly appealing, successful nasal or pulmonary delivery of nucleic acid-based vaccines is challenging because of several physical and biological barriers at the airway mucosal site, such as a variety of protective enzymes and mucociliary clearance, which remove exogenously inhaled substances. Hence, advanced nanotechnologies enabling delivery of DNA and IVT-mRNA to the nasal and pulmonary mucosa are urgently needed. Ideal nanocarriers for nucleic acid vaccines should be able to efficiently load and protect genetic payloads, overcome physical and biological barriers at the airway mucosal site, facilitate transfection in targeted epithelial or antigen-presenting cells, and incorporate adjuvants. In this review, we discuss recent developments in nucleic acid delivery systems that target airway mucosa for vaccination purposes.

Delivery of synthetic mRNAs for tissue regeneration

In recent years, nucleic acid-based therapeutics have gained increasing importance as novel treatment options for disease prevention and treatment. Synthetic messenger RNAs (mRNAs) are promising nucleic acid-based drugs to transiently express desired proteins that are missing or defective. Recently, synthetic mRNA-based vaccines encoding viral proteins have been approved for emergency use against COVID-19. Various types of vehicles, such as lipid nanoparticles (LNPs) and liposomes, are being investigated to enable the efficient uptake of mRNA molecules into desired cells. In addition, the introduction of novel chemical modifications into mRNAs increased the stability, enabled the modulation of nucleic acid-based drugs, and increased the efficiency of mRNA-based therapeutic approaches. In this review, novel and innovative strategies for the delivery of synthetic mRNA-based therapeutics for tissue regeneration are discussed. Moreover, with this review, we aim to highlight the versatility of synthetic mRNA molecules for various applications in the field of regenerative medicine and also discuss translational challenges and required improvements for mRNA-based drugs.

In Vitro Investigations on Optimizing and Nebulization of IVT-mRNA Formulations for Potential Pulmonary-Based Alpha-1-Antitrypsin Deficiency Treatment

In vitro-transcribed (IVT) mRNA has come into focus in recent years as a potential therapeutic approach for the treatment of genetic diseases. The nebulized formulations of IVT-mRNA-encoding alpha-1-antitrypsin (A1AT-mRNA) would be a highly acceptable and tolerable remedy for the protein replacement therapy for alpha-1-antitrypsin deficiency in the future. Here we show that lipoplexes containing A1AT-mRNA prepared in optimum conditions could successfully transfect human bronchial epithelial cells without significant toxicity. A reduction in transfection efficiency was observed for aerosolized lipoplexes that can be partially overcome by increasing the initial number of components. A1AT produced from cells transfected by nebulized A1AT-mRNA lipoplexes is functional and could successfully inhibit the enzyme activity of trypsin as well as elastase. Our data indicate that aerosolization of A1AT-mRNA therapy constitutes a potentially powerful means to transfect airway epithelial cells with the purpose of producing functional A1AT, while bringing along the unique advantages of IVT-mRNA.

A durable protective immune response to wild-type measles virus infection of macaques is due to viral replication and spread in lymphoid tissues

Infection with wild-type (WT) measles virus (MeV) is an important cause of childhood mortality that leads to lifelong protective immunity in survivors. WT MeV and the live-attenuated MeV used in the measles vaccine (LAMV) are antigenically similar, but the determinants of attenuation are unknown, and protective immunity induced by LAMV is less robust than that induced by WT MeV. To identify factors that contribute to these differences, we compared virologic and immunologic responses after respiratory infection of rhesus macaques with WT MeV or LAMV. In infected macaques, WT MeV replicated efficiently in B and T lymphocytes with spreading throughout lymphoid tissues resulting in prolonged persistence of viral RNA. In contrast, LAMV replicated efficiently in the respiratory tract but displayed limited spread to lymphoid tissue or peripheral blood mononuclear cells. In vitro, WT MeV and LAMV replicated similarly in macaque primary respiratory epithelial cells and human lymphocytes, but LAMV-infected lymphocytes produced little virus. Plasma concentrations of interleukin-1β (IL-1β), IL-12, interferon-γ (IFN-γ), CCL2, CCL11, CXCL9, and CXCL11 increased in macaques after WT MeV but not LAMV infection. WT MeV infection induced more protective neutralizing, hemagglutinin-specific antibodies and bone marrow plasma cells than did LAMV infection, although numbers of MeV-specific IFN-γ- and IL-4-producing T cells were comparable. Therefore, MeV attenuation may involve altered viral replication in lymphoid tissue that limited spread and decreased the host antibody response, suggesting a link between lifelong protective immunity and the ability of WT MeV, but not LAMV, to spread in lymphocytes.

New Directions in Pulmonary Gene Therapy

The lung has long been a target for gene therapy, yet efficient delivery and phenotypic disease correction has remained challenging. Although there have been significant advancements in gene therapies of other organs, including the development of several ex vivo therapies, in vivo therapeutics of the lung have been slower to transition to the clinic. Within the past few years, the field has witnessed an explosion in the development of new gene addition and gene editing strategies for the treatment of monogenic disorders. In this review, we will summarize current developments in gene therapy for cystic fibrosis, alpha-1 antitrypsin deficiency, and surfactant protein deficiencies. We will explore the different gene addition and gene editing strategies under investigation and review the challenges of delivery to the lung.

Acetylcholinesterase inhibition resulting from exposure to inhaled OP can be prevented by pretreatment with BChE in both macaques and minipigs

More frequent and widespread nerve agent attacks highlight the need for efficacious pre- and post-exposure organophosphate (OP) counter-measures to protect military and civilian populations. Because of critical targeting of acetylcholinesterase (AChE) in the CNS by OPs, a pre-treatment candidate for preventing/reducing poisoning will be a broadly acting molecule that scavenges OPs in blood before they reach their physiological targets. Prophylactic human butyrylcholinesterase (HuBChE), the leading pretreatment candidate, has been shown to protect against multiple LD50's of nerve agents in rodents, macaques, and minipigs. This review describes the development of a HuBChE bioscavenger pretreatment from early proof-of-concept studies to pre-clinical studies with the native injectable enzyme and the development of aerosolized forms of recombinant enzyme, which can be delivered by inhalation nebulizer devices, to effect protection against inhaled OP nerve agents and insecticides. Early animal studies utilized parenteral exposure. However, lungs are the portal of entry for most volatile OP vapors and represent the major means of OP intoxication. In this regard, pretreat-ment with 7.5 mg/kg of HuBChE by IM injection protected minipigs against lethal sarin vapor and prevented AChE inhibition in the blood. This is similar to the five-day protection in macaques by an aerosolized rHuBChE using a nebulizer against aerosolized paraoxon (estimated to be an 8 mg/kg estimated human dose). Importantly, lethal inhaled doses of OP may be smaller relative to the same dose delivered by injection, thus reducing the protective HuBChE dose, while a combination of HuBChE and post-exposure oxime may prolong protection.

Inhalable nanotherapeutics to improve treatment efficacy for common lung diseases

Respiratory illnesses are prevalent around the world, and inhalation-based therapies provide an attractive, noninvasive means of directly delivering therapeutic agents to their site of action to improve treatment efficacy and limit adverse systemic side effects. Recent trends in medicine and nanoscience have prompted the development of inhalable nanomedicines to further enhance effectiveness, patient compliance, and quality of life for people suffering from lung cancer, chronic pulmonary diseases, and tuberculosis. Herein, we discuss recent advancements in the development of inhalable nanomaterial-based drug delivery systems and analyze several representative systems to illustrate their key design principles that can translate to improved therapeutic efficacy for prevalent respiratory diseases. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Respiratory Disease.

Aerosolized recombinant human butyrylcholinesterase delivered by a nebulizer provides long term protection against inhaled paraoxon in macaques

The recent intentional use of nerve agents and pesticides in Europe and Afghanistan highlights the need for an effective countermeasure against organophosphates (OP) toxins. The most developed pretreatment candidate to date is plasma (native) human butyrylcholinesterase (HuBChE), which is limited in availability and because of its 1:1 stoichiometry with OPs, a large dose will present challenges when delivered parenterally both in terms of pharmacokinetics and manageability in the field. A tetrameric recombinant (r) form of human BChE produced in CHO-K1 cells with similar structure, in vivo stability and antidotal efficacy as the native form, has been developed to deliver rHuBChE as an aerosol (aer) to form a pulmonary bioshield capable of neutralizing inhaled OPs in situ and prevent AChE inhibition in the blood and in the brain; the latter associated with the symptoms of OP toxicity. Previous proof-of-concept macaque studies demonstrated that delivery of 9 mg/kg using a microsprayer inserted down the trachea, resulted in protection against an inhaled dose of 15ug/kg of aer-paraoxon (aer-Px) given 72 h later. In the present studies, pulmonary delivery of rHuBChE in macaques was achieved using Aerogen vibrating mesh nebulizers, similar to that used for human self-administration. The promising findings indicate that despite the poor lung deposition observed in macaques using nebulizers (13-20%), protective levels of RBC-AChE were still present in the blood even when exposure aer-Px (55 μg/kg) was delayed for five days. This long term retention of 5 mg/kg rHuBChE deposited in the lung bodes well for the use of an aer-rHuBChE pretreatment in humans where a user-friendly customized nebulizer with increased lung deposition up to 50% will provide even longer protection at a lower dose.

Intra-tracheal amikacin spray delivery in healthy mechanically ventilated piglets

BACKGROUND

Nebulization during mechanical ventilation is impeded by large extra-pulmonary drug deposition and long administration durations which currently limit implementation of inhaled antibiotic therapy. Direct intra-tracheal delivery using a sprayer represents an appealing alternative investigated in small animal models, but large animal data are lacking.

METHODS

Amikacin was administered through intravenous infusion (20 mg/kg), nebulization (60 mg/kg) and direct intra-tracheal spray (30 mg/kg) to 10 intubated piglets, in a randomized cross-over design. Amikacin concentrations were measured in the serum and pulmonary parenchyma. Anatomic deposition was investigated using immuno-histochemistry.

RESULTS

Spray delivery resulted in higher amikacin outputs than nebulization and infusion. Pulmonary inhaled delivery techniques yielded much higher lung concentrations and much lower serum concentrations than intravenous infusion. However, unlike nebulization and infusion, intra-tracheal spray delivery was associated with more than 100- and 1000-fold variability in lung concentrations between and within animals. Amikacin specific immuno-histochemistry showed consistent bronchial and alveolar drug deposition with all modalities.

CONCLUSION

Nebulization remains the most reliable and simple technique to deliver inhaled amikacin uniformly to the lung during mechanical ventilation. Further development of tracheal sprays is required to take advantage of potential benefits related to high drug output and low extra-pulmonary deposition in large animals.

Inhaled Nanoformulated mRNA Polyplexes for Protein Production in Lung Epithelium

Noninvasive aerosol inhalation is an established method of drug delivery to the lung, and remains a desirable route for nucleic-acid-based therapeutics. In vitro transcribed (IVT) mRNA has broad therapeutic applicability as it permits temporal and dose-dependent control of encoded protein expression. Inhaled delivery of IVT-mRNA has not yet been demonstrated and requires development of safe and effective materials. To meet this need, hyperbranched poly(beta amino esters) (hPBAEs) are synthesized to enable nanoformulation of stable and concentrated polyplexes suitable for inhalation. This strategy achieves uniform distribution of luciferase mRNA throughout all five lobes of the lung and produces 101.2 ng g^-1 of luciferase protein 24 h after inhalation of hPBAE polyplexes. Importantly, delivery is localized to the lung, and no luminescence is observed in other tissues. Furthermore, using an Ai14 reporter mouse model it is identified that 24.6% of the total lung epithelial cell population is transfected after a single dose. Repeat dosing of inhaled hPBAE-mRNA generates consistent protein production in the lung, without local or systemic toxicity. The results indicate that nebulized delivery of IVT-mRNA facilitated by hPBAE vectors may provide a clinically relevant delivery system to lung epithelium.

A Preclinical Study in Rhesus Macaques for Cystic Fibrosis to Assess Gene Transfer and Transduction by AAV1 and AAV5 with a Dual-Luciferase Reporter System

Cystic fibrosis (CF) is an autosomal recessive disease that is potentially treatable by gene therapy. Since the identification of the gene encoding CF transmembrane conductance regulator, a number of preclinical and clinical trials have been conducted using the first generation of adeno-associated virus, AAV2. All these studies showed that AAV gene therapy for CF is safe, but clinical benefit was not clearly demonstrated. Thus, a new generation of AAV vectors based on other serotypes is needed to move the field forward. This study tested two AAV serotypes (AAV1 and AAV5) using a dual-luciferase reporter system with firefly and Renilla luciferase genes packaged into AAV1 or AAV5, respectively. Two male and two female Rhesus macaques were each instilled in their lungs with both serotypes using a Penn-Century microsprayer. Both AAV1 and AAV5 vector genomes were detected in all the lung samples when measured at the time of necropsy, 45 days after instillation. However, the vector genome number for AAV1 was at least 10-fold higher than for AAV5. Likewise, luciferase activity was also detected in the same samples at 45 days. AAV1-derived activity was not statistically greater than that derived from AAV5. These data suggest that gene transfer is greater for AAV1 than for AAV5 in macaque lungs. Serum neutralizing antibodies were increased dramatically against both serotypes but were less abundant with AAV1 than with AAV5. No adverse events were noted, again indicating that AAV gene therapy is safe. These results suggest that with more lung-tropic serotypes such as AAV1, new clinical studies of gene therapy using AAV are warranted.

Adeno-Associated Virus (AAV) gene therapy for cystic fibrosis: current barriers and recent developments

INTRODUCTION

Since the cystic fibrosis (CF) gene was discovered in 1989, researchers have worked to develop a gene therapy. One of the most promising and enduring vectors is the AAV, which has been shown to be safe. In particular, several clinical trials have been conducted with AAV serotype 2. All of them detected viral genomes, but identification of mRNA transduction was not consistent; clinical outcomes in Phase II studies were also inconsistent. The lack of a positive outcome has been attributed to a less-than-efficient viral infection by AAV2, a weak transgene promoter and the host immune response to the vector. Areas covered: Herein, the authors focus on AAV gene therapy for CF, evaluating past experience with this approach and identifying ways forward, based on the progress that has already been made in identifying and overcoming the limitations of AAV gene therapy. Expert opinion: Such progress makes it clear that this is an opportune time to push forward toward the development of a gene therapy for CF. Drugs to treat the basic defect in CF represent a remarkable advance but cannot treat a significant cohort of patients with rare mutations. Thus, there is a critical need to develop a gene therapy for those individuals.

Intratracheal Gene Delivery of SERCA2a Ameliorates Chronic Post-Capillary Pulmonary Hypertension: A Large Animal Model

BACKGROUND

Pulmonary hypertension (PH) is characterized by pulmonary arterial remodeling that results in increased pulmonary vascular resistance, right ventricular (RV) failure, and premature death. Down-regulation of sarcoplasmic reticulum Ca(2+)-ATPase 2a (SERCA2a) in the pulmonary vasculature leads to perturbations in calcium ion (Ca(2+)) homeostasis and transition of pulmonary artery smooth muscle cells to a proliferative phenotype.

OBJECTIVES

We assessed the feasibility of sustained pulmonary vascular SERCA2a gene expression using aerosolized delivery of adeno-associated virus type 1 (AAV1) in a large animal model of chronic PH and evaluated the efficacy of gene transfer regarding progression of pulmonary vascular and RV remodeling.

METHODS

A model of chronic post-capillary PH was created in Yorkshire swine by partial pulmonary vein banding. Development of chronic PH was confirmed hemodynamically, and animals were randomized to intratracheal administration of aerosolized AAV1 carrying the human SERCA2a gene (n = 10, AAV1.SERCA2a group) or saline (n = 10). Therapeutic efficacy was evaluated 2 months after gene delivery.

RESULTS

Transduction efficacy after intratracheal delivery of AAV1 was confirmed by β-galactosidase detection in the distal pulmonary vasculature. Treatment with aerosolized AAV1.SERCA2a prevented disease progression as evaluated by mean pulmonary artery pressure, vascular resistance, and limited vascular remodeling quantified by histology. Therapeutic efficacy was supported further by the preservation of RV ejection fraction (p = 0.014) and improvement of the RV end-diastolic pressure-volume relationship in PH pigs treated with aerosolized AAV1.SERCA2a.

CONCLUSIONS

Airway-based delivery of AAV vectors to the pulmonary arteries was feasible, efficient, and safe in a clinically relevant chronic PH model. Vascular SERCA2a overexpression resulted in beneficial effects on pulmonary arterial remodeling, with attendant improvements in pulmonary hemodynamics and RV performance, and might offer therapeutic benefit by modifying fundamental pathophysiology in pulmonary vascular diseases.

Creation of a protective pulmonary bioshield against inhaled organophosphates using an aerosolized bioscavenger

In addition to the global use of organophosphate (OP) pesticides for agriculture, OP nerve agents and pesticides have been employed on battlefields and by terrorists (e.g., a recent sarin attack in Syria). These occurrences highlight the need for an effective countermeasure against OP exposure. Human butyrylcholinesterase (HuBChE) is a leading candidate, but injection of the high doses required for protection present pharmacokinetic challenges. An aerosolized recombinant form (aer-rHuBChE) that can neutralize inhaled OPs at the portal of entry has been assessed for its efficacy in protecting macaques against respiratory toxicity following inhalation exposure to the pesticide paraoxon (aer-Px). While protection in macaques has been demonstrated using the MicroSprayer® delivery device, administration to humans will likely employ a vibrating mesh nebulizer (VMN). Compared to the 50-70% lung deposition achieved in adult humans with a VMN, deposition in macaques is <5%, an initial major obstacle to demonstrating protection. Such problems have been partly overcome by using a more efficient modified VMN and proportionally higher doses, which together generate an effective rHuBChE pulmonary bioshield and protect against high levels of inhaled Px.

Development of rAAV2-CFTR: History of the First rAAV Vector Product to be Used in Humans

The first human gene therapy trials using recombinant adeno-associated virus (rAAV) vectors were performed in cystic fibrosis (CF) patients. Over 100 CF patients were enrolled in 5 separate trials of rAAV2-CFTR administration via nasal, endobronchial, maxillary sinus, and aerosol delivery. Recombinant AAV vectors were designed to deliver the CF transmembrane regulator (CFTR) gene and correct the basic CFTR defect by restoring chloride transport and reverting the upregulation of proinflammatory cytokines. However, vector DNA expression was limited in duration because of the low incidence of integration and natural airway epithelium turnover. In addition, repeated administration of AAV-CFTR vector resulted in a humoral immune response that prevented effective gene transfer from subsequent doses of vector. AAV serotype 2 was used in human trials before the comparison with other serotypes and determination that serotypes 1 and 5 not only possess higher tropism for the airway epithelium, but also are capable of bypassing the binding and trafficking processes-both were important hindrances to the effectiveness of rAAV2. Although rAAV-CFTR gene therapy does not appear likely to supplant newer small-molecule CFTR modulators in the near future, early work with rAAV-CFTR provided an important foundation for later use of rAAV in humans.

Complement yourself: Transcomplementation rescues partially folded mutant proteins

Cystic Fibrosis (CF) is an autosomal disease associated with malfunction in fluid and electrolyte transport across several mucosal membranes. The most common mutation in CF is an in-frame three-base pair deletion that removes a phenylalanine at position 508 in the first nucleotide-binding domain of the cystic fibrosis conductance regulator (CFTR) chloride channel. This mutation has been studied extensively and leads to biosynthetic arrest of the protein in the endoplasmic reticulum and severely reduced channel activity. This review discusses a novel method of rescuing ΔF508 with transcomplementation, which occurs when smaller fragments of CFTR containing the wild-type nucleotide binding domain are co-expressed with the ΔF508 deletion mutant. Transcomplementation rescues the processing and channel activity of ΔF508 and reduces its rate of degradation in airway epithelial cells. To apply transcomplementation as a therapy would require that the cDNA encoding the truncated CFTR be delivered to cells. We also discuss a gene therapeutic approach based on delivery of a truncated form of CFTR to airway cells using adeno-associated viral vectors.

Dose- and time-dependent effects of lipopolysaccharide on technetium-99-m-labeled diethylene-triamine pentaacetatic acid clearance, respiratory system mechanics and pulmonary inflammation

Intratracheal administration of lipopolysaccharide (LPS) in animals is a commonly used model of acute lung injury, characterized by increased alveolar-capillary membrane permeability causing protein-rich edema, inflammation, deterioration of lung mechanical function and impaired gas exchange. Technetium-99-m-labeled diethylene-triamine pentaacetatic acid ((99m)Tc-DTPA) scintigraphy is a non-invasive technique to assess lung epithelial permeability. We hypothesize that the longer the exposure and the higher the dose of LPS the greater the derangement of the various indices of lung injury. After 3, 6 and 24 h of 5 or 40 μg LPS intratracheally administration, (99m)Tc-DTPA was instilled in the lung. Images were acquired for 90 min with a γ-camera and the radiotracer clearance was estimated. In another subgroup, the mechanical properties of the respiratory system were estimated with the forced oscillation technique and static pressure-volume curves, 4.5, 7.5 and 25.5 h post-LPS (iso-times with the end of (99m)Tc-DTPA scintigraphy). Bronchoalveolar lavage (BAL) was performed and a lung injury score was estimated by histology. Lung myeloperoxidase (MPO) activity was measured. (99m)Tc-DTPA clearance increased in all LPS challenged groups compared with control. DTPA clearance presented a U-shape time course at the lower dose, while LPS had a declining effect over time at the larger dose. At 7.5 and 25.5 h post-LPS, tissue elasticity was increased and static compliance decreased at both doses. Total protein in the BAL fluid increased at both doses only at 4.5 h Total lung injury score and MPO activity were elevated in all LPS-treated groups. There is differential time- and dose-dependency of the various indices of lung injury after intratracheally LPS instillation in rats.

2-diethylaminoethyl-dextran methyl methacrylate copolymer nonviral vector: still a long way toward the safety of aerosol gene therapy

Revealing the lung tumor genome has directed the current treatment strategies toward targeted therapy. First line treatments targeting the genome of lung tumor cells have been approved and are on the market. However, they are limited by the small number of patients with the current investigated genetic mutations. Novel treatment administration modalities have been also investigated in an effort to increase the local drug deposition and disease control. In the current study, we investigated the safety of the new nonviral vector 2-diethylaminoethyl-dextran methyl methacrylate copolymer (DDMC; Ryujyu Science), which belongs to the 2-diethylaminoethyl-dextran family by aerosol administration. Thirty male BALBC mice, 2 month old, were included and divided into three groups. However, pathological findings indicated severe emphysema within three aerosol sessions. In addition, the CytoViva technique was applied for the first time to display the nonviral particles within the pulmonary tissue and emphysema lesions, and a spectral library of the nonviral vector was also established. Although our results in BALBC mice prevented us from further investigation of the DDMC nonviral vector as a vehicle for gene therapy, further investigation in animals with larger airways is warranted to properly evaluate the safety of the vector.

Aerosol delivery of eukaryotic translation initiation factor 4E-binding protein 1 effectively suppresses lung tumorigenesis in K-rasLA1 mice

Conventional radiotherapy or chemotherapy for the long-term survival of patients with lung cancer is still difficult for treatment in metastatic and advanced tumors. Therefore, the safe and effective approaches to the treatment of lung cancer are needed. In this study, the effect of delivered eukaryotic translation initiation factor 4E (eIF4E)-binding protein 1 (4E-BP1) on lung cancer progression was evaluated. Recombinant adeno-associated virus (rAAV)-M3/4E-BP1 was delivered into 6-week-old K-rasLA1 lung cancer model mice through a nose-only inhalation system twice a week for 4 weeks. Long-term repeated delivery of 4E-BP1 effectively reduced tumor progression in the lungs of K-rasLA1 mice. Reduction of eIF4E by overexpression of 4E-BP1 resulted in suppression of cap-dependent protein expression of basic fibroblast growth factor (bFGF or FGF-2) and vascular endothelial growth factor (VEGF). In addition, delivered 4E-BP1 inhibited the proliferation of lung cancer cells in K-rasLA1 mice model. Our results suggest that long-term repeated viral delivery of 4E-BP1 may provide a useful tool for designing lung cancer treatment.

Inhalable magnetic nanoparticles for targeted hyperthermia in lung cancer therapy

Lung cancer (specifically, non-small cell lung cancer; NSCLC) is the leading cause of cancer-related deaths in the United States. Poor response rates and survival with current treatments clearly indicate the urgent need for developing an effective means to treat NSCLC. Magnetic hyperthermia is a non-invasive approach for tumor ablation, and is based on heat generation by magnetic materials, such as superparamagnetic iron oxide (SPIO) nanoparticles, when subjected to an alternating magnetic field. However, inadequate delivery of magnetic nanoparticles to tumor cells can result in sub-lethal temperature change and induce resistance while non-targeted delivery of these particles to the healthy tissues can result in toxicity. In our studies, we evaluated the effectiveness of tumor-targeted SPIO nanoparticles for magnetic hyperthermia of lung cancer. EGFR-targeted, inhalable SPIO nanoparticles were synthesized and characterized for targeting lung tumor cells as well as for magnetic hyperthermia-mediated antitumor efficacy in a mouse orthotopic model of NSCLC. Our results show that EGFR targeting enhances tumor retention of SPIO nanoparticles. Further, magnetic hyperthermia treatment using targeted SPIO nanoparticles resulted in significant inhibition of in vivo lung tumor growth. Overall, this work demonstrates the potential for developing an effective anticancer treatment modality for the treatment of NSCLC based on targeted magnetic hyperthermia.

Pulmonary delivery of an aerosolized recombinant human butyrylcholinesterase pretreatment protects against aerosolized paraoxon in macaques

Butyrylcholinesterase (BChE) is the leading pretreatment candidate against exposure to organophosphates (OPs), which pose an ever increasing public and military health. Since respiratory failure is the primary cause of death following acute OP poisoning, an inhaled BChE therapeutic could prove highly efficacious in preventing acute toxicity as well as the associated delayed neuropathy. To address this, studies have been performed in mice and macaques using Chinese Hamster Ovary cells (CHO)-derived recombinant (r) BChE delivered by the pulmonary route, to examine whether the deposition of both macaque (Ma) and human (Hu) rBChE administered as aerosols (aer) favored the creation and retention of an efficient protective "pulmonary bioshield" that could scavenge incoming (inhaled) OPs in situ thereby preventing entry into the circulation and inhibition of plasma BChE and AChE on red blood cells (RBC-AChE) and in cholinergic synapses. In contrast to parenteral delivery of rBChE, which currently requires posttranslational modification for good plasma stability, an unmodified aer-rBChE pretreatment given 1-40 h prior to >1 LD50 of aer-paraoxon (Px) was able to prevent inhibition of circulating cholinesterase in a dose-dependent manner. These studies are the first to show protection by rBChE against a pesticide such as paraoxon when delivered directly into the lung and bode well for the use of a non-invasive and consumer friendly method of rHuBChE delivery as a human treatment to counteract OP toxicity.

Vectors for inhaled gene therapy in lung cancer. Application for nano oncology and safety of bio nanotechnology

Novel aerosol therapeutic modalities have been investigated for lung cancer. Inhaled gene therapy has presented safety and effectiveness previously in cystic fibrosis. However, safety concerns have been raised regarding the safety of non-viral vectors for inhaled gene therapy in lung cancer, and therefore small steps have been made towards this multifunctional treatment modality. During the last decade, numerous new nanocomplexes have been created and investigated as a safe gene delivery nano-vehicle. These formulations are multifunctional; they can be used as either local therapy or carrier for an effective inhaled gene therapy for lung cancer. Herein, we present current and future perspectives of nanocomplexes for inhaled gene therapy treatment in lung cancer.

Pulmonary delivery of dry powders to rats: tolerability limits of an intra-tracheal administration model

The inhaled route is increasingly developed to deliver locally acting or systemic therapies, and rodent models are used to assess tolerance before clinical studies. Endotracheal intubation of rats with a probe which generates powder aerosols enables controlled administration of drug directly into the respiratory tract. However, preliminary observations of intratracheal powder administration procedures have raised concerns with regard to pulmonary safety. The aim of the present work was to evaluate the safety of intra-tracheal administration of dry powder in a rat model. Sixty animals were administered various volumes of air alone, lactose or magnesium stearate through a Microsprayer(®) (Pencentury, USA). The mass of powder actually delivered to each animal was calculated. Rats were sacrificed immediately after administration, and the lungs, trachea and larynx were removed and examined for gross pathology. The mass of powder delivered varied, the full dose being rarely delivered. About one third of the administration procedures resulted in respiratory failure, and macroscopic pulmonary lesions were observed in about 55% of animals. Lung damages were observed with air alone, lactose and magnesium stearate. In conclusion, artifacts observed with this technique may limit the relevance of the model. These observations are particularly important in the context of regulatory toxicity studies.

Inhalation of nebulized perfluorochemical enhances recombinant adenovirus and adeno-associated virus-mediated gene expression in lung epithelium

Use of perfluorochemical liquids during intratracheal vector administration enhances recombinant adenovirus and adeno-associated virus (AAV)-mediated lung epithelial gene expression. We hypothesized that inhalation of nebulized perfluorochemical vapor would also enhance epithelial gene expression after subsequent intratracheal vector administration. Freely breathing adult C57BL/6 mice were exposed for selected times to nebulized perflubron or sterile saline in a sealed Plexiglas chamber. Recombinant adenoviral vector was administered by transtracheal puncture at selected times afterward and mice were killed 3 days after vector administration to assess transgene expression. Mice tolerated the nebulized perflubron without obvious ill effects. Vector administration 6 hr after nebulized perflubron exposure resulted in an average 540% increase in gene expression in airway and alveolar epithelium, compared with that with vector alone or saline plus vector control (p<0.05). However, vector administration 1 hr, 1 day, or 3 days after perflubron exposure was not different from either nebulized saline with vector or vector alone and a 60-min exposure to nebulized perflubron is required. In parallel pilot studies in macaques, inhalation of nebulized perflubron enhanced recombinant AAV2/5 vector expression throughout the lung. Serial chest radiographs, bronchoalveolar lavages, and results of complete blood counts and serum biochemistries demonstrated no obvious adverse effects of nebulized perflubron. Further, one macaque receiving nebulized perflubron only was monitored for 1 year with no obvious adverse effects of exposure. These results demonstrate that inhalation of nebulized perflubron, a simple, clinically more feasible technique than intratracheal administration of liquid perflubron, safely enhances lung gene expression.

Pulmonary delivery and tissue distribution of aerosolized antisense 2'-O-Methyl RNA containing nanoplexes in the isolated perfused and ventilated rat lung

Pulmonary delivery of drugs, particularly in the treatment of lung cancer, is an attractive strategy for future targeted therapy. In this context, inhalation of nanoplexes might offer a new mode for drug delivery in gene therapy. However, limited data are currently available demonstrating pulmonary delivery, cellular uptake as well as local tolerability in lung tissue. The aim of this study was to elucidate the pulmonary delivery, tissue distribution and local tolerability of aerosolized chitosan-coated poly(lactide-co-glycolide) based nanoplexes containing antisense 2'-O-Methyl RNA (OMR). Therefore, an aerosol of OMR-nanoplexes or OMR alone was administered intra-tracheally using the model of the isolated perfused and ventilated rat lung. Localization of OMR in rat lung tissue was examined by immunohistochemistry. Administration of the OMR-nanoplex formulation resulted in significantly higher cellular OMR uptake of the respiratory epithelium in contrast to the administration of OMR alone, indicating that drug administration via aerosolized nanoplexes is able to target lung tissue. No prominent changes in lung physiology parameters were observed following inhalation, suggesting good local tolerability of OMR-nanoplex formulation.

Successful respiratory immunization with dry powder live-attenuated measles virus vaccine in rhesus macaques

Measles remains an important cause of childhood mortality worldwide. Sustained high vaccination coverage is the key to preventing measles deaths. Because measles vaccine is delivered by injection, hurdles to high coverage include the need for trained medical personnel and a cold chain, waste of vaccine in multidose vials and risks associated with needle use and disposal. Respiratory vaccine delivery could lower these barriers and facilitate sustained high coverage. We developed a novel single unit dose, dry powder live-attenuated measles vaccine (MVDP) for respiratory delivery without reconstitution. We tested the immunogenicity and protective efficacy in rhesus macaques of one dose of MVDP delivered either with a mask or directly intranasal with two dry powder inhalers, PuffHaler and BD Solovent. MVDP induced robust measles virus (MeV)-specific humoral and T-cell responses, without adverse effects, which completely protected the macaques from infection with wild-type MeV more than one year later. Respiratory delivery of MVDP was safe and effective and could aid in measles control.

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.

Targeted combined aerosol chemotherapy in dogs and radiologic toxicity grading

BACKGROUND

We investigated whether combination chemotherapy, targeted with the AeroProbe® Intracorporeal Nebulizing Catheter (INC), could be safely administered, and developed a radiologic grading scheme to monitor subclinical effects on the lungs.

METHODS

In anesthetized and mechanically ventilated healthy dogs (n = 3), we introduced the INC via a flexible bronchoscope into the right caudal lung lobe and administered escalating dosages of gemcitabine (1, 2, 3, or 6 mg/kg) followed by cisplatin (10 mg/m(2)). Treatments were performed every 2 weeks for 4 treatments and dogs were monitored weekly with physical examination, biochemical tests, and thoracic radiographs. Dogs were sacrificed 2 weeks after the final treatment and tissues examined histologically. A radiologic grading scheme was developed to monitor subclinical pulmonary toxicity.

RESULTS

No significant side effects occurred in any dog. All dogs developed focal pneumonitis radiographically, and chronic, severe pneumonia with fibrosis histologically limited to the treated portion of the lung. Radiologic scores increased over time following increasing doses of chemotherapy.

CONCLUSIONS

Targeted aerosol delivery of gemcitabine and cisplatin by INC was clinically well tolerated. This minimally invasive method is promising for lung cancer treatment, especially given the lack of clinical toxicity. The proposed radiologic grading scheme provides a method to monitor subclinical local drug toxicity.

Respiratory syncytial virus engineered to express the cystic fibrosis transmembrane conductance regulator corrects the bioelectric phenotype of human cystic fibrosis airway epithelium in vitro

Cystic fibrosis (CF) is the most common lethal recessive genetic disease in the Caucasian population. It is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene that is normally expressed in ciliated airway epithelial cells and the submucosal glands of the lung. Since the CFTR gene was first characterized in 1989, a major goal has been to develop an effective gene therapy for CF lung disease, which has the potential to ameliorate morbidity and mortality. Respiratory syncytial virus (RSV) naturally infects the ciliated cells in the human airway epithelium. In addition, the immune response mounted against an RSV infection does not prevent subsequent infections, suggesting that an RSV-based vector might be effectively readministered. To test whether the large 4.5-kb CFTR gene could be expressed by a recombinant RSV and whether infectious virus could be used to deliver CFTR to ciliated airway epithelium derived from CF patients, we inserted the CFTR gene into four sites in a recombinant green fluorescent protein-expressing RSV (rgRSV) genome to generate virus expressing four different levels of CFTR protein. Two of these four rgRSV-CFTR vectors were capable of expressing CFTR with little effect on viral replication. rgRSV-CFTR infection of primary human airway epithelial cultures derived from CF patients resulted in expression of CFTR protein that was properly localized at the luminal surface and corrected the chloride ion channel defect in these cells.

Francisella inhibits STAT1-mediated signaling in macrophages and prevents activation of antigen-specific T cells

Signal transducer and activator of transcription-1 (STAT1) signaling mediate most biological functions of IFNalpha, IFNbeta and IFNgamma although recent studies indicate that IFNgamma can alter expression of several genes via a STAT1-independent pathway. STAT1 is critical for immunity against a variety of intracellular pathogens and some studies show that pathogens evade host immunity by interfering with STAT1 signaling. Here, we have investigated the role of STAT1 in host defense against pulmonary Francisella novicida infection using STAT1-/- mice. In addition, we examined the effect of F. novicida on STAT1 signaling in macrophages and on their ability to activate antigen-specific T cells. Both wild-type (WT) and STAT1-/- BALB/c mice were susceptible to aerosol challenge with 10(3) F. novicida and displayed 100% mortality. However, STAT1-/- mice developed more severe pneumonia, liver pathology and succumbed to infection faster than WT mice. The lungs, liver and hearts from F. novicida-infected STAT1-/- mice also contained more bacteria than WT mice at the time of death. In vitro studies showed that F. novicida suppressed IFNgammaRalpha (alpha subunit of IFNgamma receptor) and MHC class II expression, down-regulated IFNgamma-induced STAT1 activation and reduced nuclear binding of STAT1 in RAW264.7 macrophages. Furthermore, F. novicida-infected BMDM loaded with ovalbumin (OVA) were less efficient in activating OVA-specific CD4+ T cells in vitro. These findings demonstrate that STAT1-mediated signaling participates in the host defense against pulmonary F. novicida infection but it is not sufficient to prevent mortality associated with this infection. Moreover, our results show that F. novicida attenuates STAT1-mediated IFNgamma signaling in macrophages and impairs their ability to activate antigen-specific CD4+ T cells.

Tailoring the AAV vector capsid for gene therapy

A number of preclinical studies have shown the adeno-associated virus (AAV) to be an efficient vehicle for gene therapy. Clinical studies successfully demonstrated its potential for in vivo gene transfer. The complexity of host-vector interactions when progressing from small to large animal models, and eventually to humans, has impeded translation of AAV technology to the clinic. One approach to address this complexity has been to explore the biological characteristics of variations in AAV capsid structure. Initial strategies characterized the naturally occurring capsid variants from mammalian species. The structural and functional knowledge gathered on these natural AAV variants as vectors has led to the first series of second-generation vectors that aim at specifically improving certain properties by rational design of the capsid. A third exciting approach uses directed evolution to isolate vectors that are able to overcome selective pressures applied in the laboratory and thereby steer the capsid to evolve toward improved functionality.

Inhalable siRNA: potential as a therapeutic agent in the lungs

RNA interference (RNAi) is gaining increasing popularity both as a molecular biology tool and as a potential therapeutic agent. RNAi is a naturally occurring gene regulatory mechanism, which has a number of advantages over other gene/antisense therapies including specificity of inhibition, potency, the small size of the molecules and the diminished risk of toxic effects, e.g., immune responses. Targeted, local delivery of RNAi to the lungs via inhalation offers a unique opportunity to treat a range of previously untreatable or poorly controlled respiratory conditions. In this timely review we look at the potential applications of RNAi in the lungs for the treatment of a range of diseases including inflammatory and immune conditions, cystic fibrosis, infectious disease and cancer. In 2006 Alnylam initiated the first phase 1 clinical study of an inhaled siRNA for the treatment of respiratory syncytial virus. If its potential as a therapeutic is to be realized, then safe and efficient means of targeted delivery of small interfering RNA (siRNA) to the lungs must be developed. Therefore in this review we also present the latest developments in siRNA delivery to airway cells in vitro and the work to date on in vivo delivery of siRNA to the lungs for the treatment of a range of diseases.

Respiratory infection with Francisella novicida induces rapid dystrophic cardiac calcinosis (DCC)

Francisella tularensis causes pulmonary tularemia and death in humans when left untreated. Here, using a novel aerosol infection model, we show that acute pulmonary Francisella novicida infection not only causes pneumonia and liver damage, but also induces dystrophic cardiac calcinosis (DCC) in BALB/c mice. C57BL/6 mice also develop pneumonia and hepatic damage, but fail to develop DCC. Development of DCC in BALB/c mice is associated with significant induction of RANKL but not osteopontin in their organs. Depletion of lung macrophages prior to infection markedly reduces pericarditis and calcification in BALB/c mice but does not increase their susceptibility to infection.

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.

Expression of a truncated cystic fibrosis transmembrane conductance regulator with an AAV5-pseudotyped vector in primates

Gene therapy using recombinant adeno-associated virus (rAAV2) vectors for cystic fibrosis has shown gene transfer and remarkable safety, yet indeterminate expression. A new construct has been characterized with a powerful exogenous promoter, the cytomegalovirus enhancer/chicken beta-actin promoter, driving a truncated CF transmembrane conductance regulator (CFTR), pseudotyped in an AAV5 viral coat. Our goal is to demonstrate that airway delivery of a pseudotyped rAAV5 vector results in gene transfer as well as expression in non-human primates. Aerosolized pseudotyped rAAV5-DeltaCFTR or rAAV5-GFP (green fluorescent protein) genes were delivered to four and six lungs, respectively. The pseudotyped rAAV5 vector did result in GFP gene transfer (1.005x10(6) copies/mug DNA on average) and quantifiable gene expression. Microscopy confirmed protein expression in airway epithelium. Similarly, the vector also resulted in vector-specific CFTR DNA (1.24x10(5) copies/microg) and mRNA expression. Immunoprecipitation and (32)P phosphoimaging were used to demonstrate CFTR protein expression, as qualitatively enhanced beyond the barely detectable endogenous expression in untreated animals. Based on these promising studies, this CFTR minigene construct is a therapeutic candidate.