A phase II, double-blind, randomized, placebo-controlled clinical trial of tgAAVCF using maxillary sinus delivery in patients with cystic fibrosis with antrostomies

Superior neovascularization and muscle regeneration in ischemic skeletal muscles following VEGF gene transfer by rAAV1 pseudotyped vectors

Recombinant adeno-associated virus serotype 2 (rAAV2) vector has been widely employed for gene therapy. Recent progress suggests that the new serotypes of AAV showed a better performance than did AAV2 in normal tissues. Here, we evaluate the potential role of human vascular endothelial growth factor (VEGF) gene transfer using rAAV vector pseudotyped with serotype 1 capsid proteins (rAAV1) in the treatment of muscle ischemia. In ischemic skeletal muscles, the rAAV1-LacZ vector allowed higher level, broader distribution, and long-lasting gene expression compared with the rAAV2-LacZ vector. Muscle VEGF165 production following the rAAV1-VEGF165 vector injection was 5-10 times higher than that following the rAAV2-VEGF165 vector injection. VEGF165 production mediated by the rAAV1-VEGF165 vector stimulated a large set of neovascularization with relatively mature vascular structures and enhanced muscle regeneration in the ischemic skeletal muscles. Thus, the rAAV1-VEGF165 vector mediated gene transfer may be a therapeutic approach to peripheral vascular diseases.

The inhibitory effects of anticoagulation on in vivo gene transfer by adeno-associated viral or adenoviral vectors

Identifying factors that influence gene transfer efficacy is critical for a successful gene-based clinical study. Here we demonstrate that in vivo AAV-2-mediated gene transfer is efficiently inhibited by unfractionated heparin, but not by a heparin preparation containing mainly low-molecular-weight forms (LMWH). Surprisingly, inhibitors of thrombin or factor Xa (F.Xa) significantly reduced AAV-2 transduction in a dose-dependent manner. These effects were independent of the vector promoter, transgene, or strain of mice. Expression by alternate AAV serotypes 5 and 8 was not affected by anticoagulant drugs, which suggests an AAV-2-specific effect. Moreover, AAV-2-mediated gene expression was diminished in mice with deficiency in thrombin generation (factor IX deficiency) and enhanced in mice with procoagulant phenotype due to factor V Leiden. In addition, inhibitors of F.Xa diminished adenovirus-mediated gene expression. These results demonstrated that coagulation activity itself is critical to ensure optimal viral vector transduction. Since intravascular delivery of vectors often requires the use of anticoagulants, the use of LMWH appears to be safe. These observations are of relevance for approaches using AAV-2 or adenoviral vectors, especially in early phase studies designed to identify the minimum therapeutic doses.

Green fluorescent protein-tagged adeno-associated virus particles allow the study of cytosolic and nuclear trafficking

To allow the direct visualization of viral trafficking, we genetically incorporated enhanced green fluorescent protein (GFP) into the adeno-associated virus (AAV) capsid by replacement of wild-type VP2 by GFP-VP2 fusion proteins. High-titer virus progeny was obtained and used to elucidate the process of nuclear entry. In the absence of adenovirus 5 (Ad5), nuclear translocation of AAV capsids was a slow and inefficient process: at 2 h and 4 h postinfection (p.i.), GFP-VP2-AAV particles were found in the perinuclear area and in nuclear invaginations but not within the nucleus. In Ad5-coinfected cells, isolated GFP-VP2-AAV particles were already detectable in the nucleus at 2 h p.i., suggesting that Ad5 enhanced the nuclear translocation of AAV capsids. The number of cells displaying viral capsids within the nucleus increased slightly over time, independently of helper virus levels, but the majority of the AAV capsids remained in the perinuclear area under all conditions analyzed. In contrast, independently of helper virus and with 10 times less virions per cell already observed at 2 h p.i., viral genomes were visible within the nucleus. Under these conditions and even with prolonged incubation times (up to 11 h p.i.), no intact viral capsids were detectable within the nucleus. In summary, the results show that GFP-tagged AAV particles can be used to study the cellular trafficking and nuclear entry of AAV. Moreover, our findings argue against an efficient nuclear entry mechanism of intact AAV capsids and favor the occurrence of viral uncoating before or during nuclear entry.

Spliceosome-Mediated RNATrans-Splicing with Recombinant Adeno-Associated Virus Partially Restores Cystic Fibrosis Transmembrane Conductance Regulator Function to Polarized Human Cystic Fibrosis Airway Epithelial Cells

We previously reported that spliceosome-mediated RNA trans-splicing (SMaRT), using recombinant adenoviral vectors expressing pre-trans-splicing molecules (PTMs), could partially restore cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel activity to polarized human DeltaF508 CF airway epithelia. Although these studies proved that SMaRT could correct CFTR mRNA defects, recombinant adenoviral infection from the basolateral surface was required because of inefficient infection from the apical membrane. Hence, applications of SMaRT technology for CF gene therapy require further testing with alternative, more clinically viable, vector systems. Furthermore, because recombinant adeno-associated virus (rAAV) vectors have packing limitations with respect to the size of the CFTR transgene insert, SMaRT correction of CFTR has the added attraction of a smaller transgene cassette. In the present study, we investigated whether rAAV vectors could effectively rescue CFTR chloride conductance in polarized human CF airway epithelial cells, using a SMaRT approach. AAV vectors were generated to carry a PTM engineered to bind intron 9 of CFTR pre-mRNA and then trans-splice the normal sequence for human CFTR exons 10-24 into the endogenous pre-mRNA. Human CF polarized airway epithelia were infected from the apical membrane with rAAV2 or rAAV5 CFTR-PTM vectors in the presence of proteasome-modulating agents (doxorubicin and N-acetyl-L-leucinyl-L-leucinyl-L-norleucinal) to enhance transduction. Epithelia were then evaluated for cAMP-sensitive short-circuit currents 2 weeks postinfection. Levels of CFTR correction seen with rAAV2 (1.07 +/- 0.24 microA) and rAAV5 (0.90 +/- 0.20 microA) CFTR-PTM vectors were similar, representing conductance equivalent to 14.2 and 13.6% of that observed in non-CF human polarized epithelia, respectively. RT-PCR analysis demonstrated the existence of wild-type CFTR transcript in CFTR-PTM-corrected epithelia, whereas only DeltaF508 mRNA was detected in polarized cells infected with control rAAV LacZ-PTM vectors. These results provide evidence that rAAV vectors are capable of using SMaRT to correct CFTR function after apical infection of human CF airway epithelia. The ability of CFTR-PTM-mediated correction to maintain endogenous CFTR regulation of the transgene product may further improve the efficacy of gene therapy for CF.

Inhibition of p38 mitogen activated protein kinase controls airway inflammation in cystic fibrosis

BACKGROUND

Cystic fibrosis (CF) airways are characterised by chronic inflammation, increased interleukin (IL)-8 secretion, and neutrophil activation which are considered the principal factors of morbidity and mortality in CF patients. Optimising management of this chronic inflammatory response is therefore a key issue of basic and clinical CF research. Several reports have addressed ways to manage CF airways inflammation, and an attractive therapeutic strategy may be the inhibition of the p38-mitogen activated protein kinase (p38-MAP-k) pathway.

METHODS

A new ex vivo model was used to study the mucosal inflammatory response to environmental airways stimuli. Nasal biopsy tissues from CF patients and controls were cultured ex vivo for 20 minutes, 4 hours, and 24 hours in the presence of lipopolysaccharide (LPS) from Pseudomonas aeruginosa (PA) with and without the p38-MAP-k inhibitor SB203580. Quantitative mRNA assessment, immunohistochemistry, and Western blots were used to detect the expression and modulation of inflammatory markers.

RESULTS

PA-LPS challenge induced a time dependent mucosal inflammation indicated by rapid epithelial activation, IL-8 release, COX-2 upregulation, and neutrophil migration to the upper mucosal layers. Some of these LPS induced changes (IL-8 release and neutrophil migration) were specific to CF tissues. SB203580 significantly controlled all LPS induced mucosal changes in CF tissues.

CONCLUSION

These findings provide a rationale and proof of principle for the potential use of p38-MAP-k inhibitors to control inflammation in patients with CF.

Progress towards gene therapy for cystic fibrosis

A decade ago it was widely anticipated that cystic fibrosis would be one of the first diseases to be treated by gene therapy. The difficult hurdle of cloning the responsible gene had been accomplished, its function was established and the lung appeared readily accessible for gene replacement. Since the first clinical trials for cystic fibrosis lung disease in the early 1990s it has become increasingly apparent that successful lung-directed gene therapy is significantly more complex than was first envisioned. Numerous obstacles including vector toxicity, inefficient transgene expression and limited vector production have delayed progress. An increased understanding of vector biology and host interaction has led to the development of novel strategies to enhance the efficiency and selectivity of gene delivery to the lung. Although significant challenges remain, there is now a realistic prospect of a clinically effective treatment in the next 10 years.

Compacted DNA nanoparticles administered to the nasal mucosa of cystic fibrosis subjects are safe and demonstrate partial to complete cystic fibrosis transmembrane regulator reconstitution

A double-blind, dose escalation gene transfer trial was conducted in subjects with cystic fibrosis (CF), among whom placebo (saline) or compacted DNA was superfused onto the inferior turbinate of the right or left nostril. The vector consisted of single molecules of plasmid DNA carrying the cystic fibrosis transmembrane regulator- encoding gene compacted into DNA nanoparticles, using polyethylene glycol-substituted 30-mer lysine peptides. Entry criteria included age greater than 18 years, FEV1 exceeding 50% predicted, and basal nasal potential difference (NPD) isoproterenol responses (> or = -5 mV) that are typical for subjects with classic CF. Twelve subjects were enrolled: 2 in dose level I (DLI) (0.8 mg DNA), 4 in DLII (2.67 mg), and 6 in DLIII (8.0 mg). The primary trial end points were safety and tolerability, and secondary gene transfer end points were assessed. In addition to routine clinical assessments and laboratory tests, subjects were serially evaluated for serum IL-6, complement, and C-reactive protein; nasal washings were taken for cell counts, protein, IL-6, and IL-8; and pulmonary function and hearing tests were performed. No serious adverse events occurred, and no events were attributed to compacted DNA. There was no association of serum or nasal washing inflammatory mediators with administration of compacted DNA. Day 14 vector polymerase chain reaction analysis showed a mean value in DLIII nasal scraping samples of 0.58 copy per cell. Partial to complete NPD isoproterenol responses were observed in eight subjects: one of two in DLI, three of four in DLII, and four of six in DLIII. Corrections persisted for as long as 6 days (1 subject to day 28) after gene transfer. In conclusion, compacted DNA nanoparticles can be safely administered to the nares of CF subjects, with evidence of vector gene transfer and partial NPD correction.

Impaired nuclear transport and uncoating limit recombinant adeno-associated virus 2 vector-mediated transduction of primary murine hematopoietic cells

Controversies abound concerning hematopoietic stem cell transduction by recombinant adeno-associated virus 2 (AAV) vectors. For human hematopoietic cells, we have shown that this problem is related to the extent of expression of the cellular receptor for AAV. At least a small subset of murine hematopoietic cells, on the other hand, does express both the AAV receptor and the coreceptor, yet is transduced poorly. In the present study, we have found that approximately 85% of AAV genomes were present in the cytoplasmic fraction of primary murine c-Kit(+)Lin- hematopoietic cells. However, when mice were injected intraperitoneally with hydroxyurea before isolation of these cells, the extent to which AAV genomes were detected in the cytoplasmic fraction was reduced to approximately 40%, with a corresponding increase to approximately 60% in the nuclear fraction, indicating that hydroxyurea facilitated nuclear transport of AAV. It was apparent, nonetheless, that a significant fraction of the AAV genomes present in the nuclear fraction from cells obtained from hydroxyurea-treated mice was single stranded. We next tested whether the single-stranded AAV genomes were derived from virions that failed to undergo uncoating in the nucleus. A substantial fraction of the signal in the nuclear fraction of hematopoietic cells obtained from hydroxyurea-treated mice was also resistant to DNase I. That AAV particles were intact and biologically active was determined by successful transduction of 293 cells by virions recovered from murine hematopoietic cells 48 hr postinfection. Although hydroxyurea facilitated nuclear transport of AAV, most of the virions failed to undergo uncoating, thereby leading to only a partial improvement in viral second- strand DNA synthesis and transgene expression. A better understanding of the underlying mechanism of viral uncoating has implications in the optimal use of recombinant AAV vectors in hematopoietic stem cell gene therapy.

Safety characterization of HeLa-based cell substrates used in the manufacture of a recombinant adeno-associated virus-HIV vaccine

The use of transformed cell substrates for prophylactic vaccine manufacturing is widely debated. Extensive characterization is required to address the suitability of neoplastic cell substrates for vaccine manufacture. The HeLa-based cell substrate used in the manufacture of a prophylactic rAAV-HIV vaccine, AAV2-gagPR delta RT (tgAAC09) was tested in vivo for its tumor-forming potential, the oncogenic potential of its high molecular weight DNA and the potential presence of occult oncogenic adventitious agents. This data from these in vivo studies, in conjunction with prion gene and protein characterization, cell and viral clearance studies and quantity of residual host-cell DNA levels in the purified tgAAC09 vaccine, were used to establish what we believe to be an acceptable safety profile for the vaccine manufacturing process. The tumor-producing dose in 50% of the animals was consistent with that in a published report from FDA staff for HeLa cells. High molecular weight cellular DNA was not oncogenic and no occult oncogenic agents were detected by testing in nude mice and newborn rodent models, respectively. Endogenous prion protein was also normal and genomic sequence analysis detected no mutations associated with increased risk of prion disease. In addition, the purification process used to produce this vaccine candidate removed all detectable cells (clearance of greater than 22 log10), viral clearance study showed 6-17 log10 clearance of three model viruses and host-cell DNA in the bulk product was less than 100pg host-cell DNA per dose of 3 x 10(11) DNase resistant particles (DRP) of the vaccine. Taken together, the data from the in vivo and in vitro tests that were performed to characterize the HeLa based producer cell line (T3B12-5B) and HeLa S3 cells support the use of these cells as substrates for the manufacture of a purified rAAV-HIV vaccine candidate. The data also supports the ability of the process, employing the HeLa cell substrate, used to manufacture the rAAV-HIV vaccine to produce a product as free of adventitious agents as current testing procedures can document. Safety of the rAAV-HIV vaccine is currently being assessed in a Phase I clinical trial.

Airway gene therapy and cystic fibrosis

Airway disease in cystic fibrosis (CF) is the major cause of death and is presently inadequately treatable, but genetic therapies offer the hope that such life-long disease will be curable, or at least satisfactorily treated. Normal pathogen defences that have evolved on airway surfaces also prevent the various gene vectors now available from producing effective gene transfer. Nevertheless, findings from basic research and human clinical trials are revealing how these barriers might be overcome or circumvented, with benefits to therapeutic efficacy and patient safety. Though progress is slower than expected or desired, the therapeutic rewards will be great when safe and effective gene therapy for CF airway disease becomes a clinical reality.

Prevention and reversal of lupus in NZB/NZW mice by costimulatory blockade with adeno-associated virus-mediated gene transfer

OBJECTIVE

To investigate the potency of costimulatory blockade with adeno-associated virus (AAV)-mediated gene transfer in the prevention and reversal of lupus in a murine model.

METHODS

AAV vectors expressing CTLA-4Ig or CD40Ig were injected into NZB/NZW mice. Serum levels of transgene expression and autoantibody titers were determined by enzyme-linked immunosorbent assay. The therapeutic effects on proteinuria, renal pathologic features, and survival rate were evaluated. Splenic T cell phenotypes were analyzed by flow cytometry. The humoral immune response to a foreign antigen was also examined in treated mice.

RESULTS

A single injection of AAV serotype 8 (AAV8)-CTLA-4Ig in neonatal NZB/NZW mice before the onset of lupus effectively delayed and inhibited autoantibody production, proteinuria, and kidney damage and prolonged their lifespan. In addition, coinjection of AAV8-CTLA-4Ig and AAV8-CD40Ig vectors into neonatal mice achieved a synergistic effect and the best efficacy. The preventive effects were attributed to suppression of CD4+ T cell activation and the transition from naive to memory T cells. Moreover, coinjection of these 2 vectors in adult mice reversed the existing autoantibody levels, suppressed the development of proteinuria, and prolonged their lifespan. The therapeutic effects were found to be dependent on the vector dose. In addition, AAV-mediated long-term gene expression did not severely suppress the host humoral response to foreign antigen.

CONCLUSION

Our findings show that delivery of costimulatory inhibitor transgenes by AAV vectors could prevent and reverse lupus in this murine model, suggesting the potential of AAV-mediated gene transfer as an alternative treatment for lupus.

Adeno-associated virus serotypes 1 to 5 mediated tumor cell directed gene transfer and improvement of transduction efficiency

BACKGROUND

Gene therapy is an attractive new approach for the treatment of cancer. Therefore, the development of efficient vector systems is of crucial importance in this field. Different adeno-associated virus (AAV) serotypes have been characterized so far, which show considerable differences in tissue tropism. Consequently, we aimed to characterize the most efficient serotype for this application.

METHODS

To exclude all influences other than those provided by the capsid, all serotypes contained the same transgene cassette flanked by the AAV2 inverted terminal repeats. We systematically compared these vectors for efficiency in human cancer cell directed gene transfer. In order to identify limiting steps, the influence of second-strand synthesis and proteasomal degradation of AAV in a poorly transducible cell line were examined.

RESULTS

AAV2 was the most efficient serotype in all solid tumor cells and primary melanoma cells with transduction rates up to 98 +/- 0.3%. Transduction above 70% could be reached with serotypes 1 (in cervical and prostate carcinoma) and 3 (in cervical, breast, prostate and colon carcinoma) using 1000 genomic particles per cell. In the colon carcinoma cell line HT-29 proteasomal degradation limited AAV1-AAV4-mediated gene transfer. Moreover, inefficient second-strand synthesis prevents AAV2-mediated transgene expression in this cell line.

CONCLUSIONS

Recent advances in AAV-vector technology suggest that AAV-based vectors can be used for cancer gene therapy. Our comparative analysis revealed that, although AAV2 is the most promising candidate for such an application, serotypes 1 and 3 are valid alternatives. Furthermore, the use of self-complementary AAV vectors and proteasome inhibitors significantly improves cancer cell transduction.

Dual Therapeutic Utility of Proteasome Modulating Agents for Pharmaco-gene Therapy of the Cystic Fibrosis Airway

Pharmacologic- and gene-based therapies have historically been developed as two independent therapeutic platforms for cystic fibrosis (CF) lung disease. Inhibition of the dysregulated epithelial Na channel (ENaC) is one pharmacologic approach to enhance airway clearance in CF. We investigated pharmacologic approaches to enhance CFTR gene delivery with recombinant adeno-associated virus (rAAV) and identified compounds that significantly improved viral transduction while simultaneously inhibiting ENaC activity through an unrelated mechanism. Treatment of human CF airway epithelia with proteasome modulating agents (LLnL and doxorubicin) at the time of rAAV2 or rAAV2/5 infection dramatically enhanced CFTR gene delivery and correction of CFTR-mediated short-circuit currents. Surprisingly, these agents also facilitated long-term (15-day) functional inhibition of ENaC currents independent of CFTR vector administration. Inhibition of ENaC activity was predominantly attributed to a doxorubicin-dependent decrease in gamma-ENaC subunit mRNA expression and an increase in gamma-ENaC promoter methylation. This is the first report to describe the identification of compounds with dual therapeutic action that are able to enhance the efficacy of CFTR gene therapy to the airway while simultaneously ameliorating primary aspects of CF disease pathophysiology. The identification of such compounds mark a new area for drug development, not only for CF, but also for other gene therapy disease targets.

Advances in AAV-mediated gene transfer for the treatment of inherited disorders

The holy grail of gene therapy is the cure of genetic diseases. To achieve this goal, a vector system is desirable that offers a high level of safety combined with clinical efficacy and versatility in terms of potential applications. Gene therapy vectors based on recombinant adeno-associated viruses (AAVs) meet all of these criteria: They are nonpathogenic, devoid of viral coding sequences, and mediate long-term gene expression in the absence of an immune or inflammatory response. Moreover, with the recent discovery of novel AAV serotypes, there is now one preferred serotype for nearly every organ or tissue to target. Thus, AAV gene therapy vectors are increasingly becoming the vectors of choice for the treatment of inherited disorders.

Long-term correction of murine lipoprotein lipase deficiency with AAV1-mediated gene transfer of the naturally occurring LPL(S447X) beneficial mutation

Human lipoprotein lipase (LPL) deficiency causes profound hypertriglyceridemia and life-threatening pancreatitis. We recently developed an adult murine model for LPL deficiency: LPL -/- mice display grossly elevated plasma triglyceride (TG) levels (>200-fold) and very low high-density lipoprotein cholesterol (HDL-C < 10% of normal). We used this animal model to test the efficacy of adeno-associated virus-mediated expression of hLPL(S447X) (AAV1-LPL(S447X)) in muscle for the treatment of LPL deficiency. Intramuscular administration of AAV1-LPL(S447X) resulted in dose-dependent expression of hLPL protein and LPL activity (up to 33% of normal murine levels) in postheparin plasma. Remarkably, visible hyperlipidemia was resolved within 1 week; plasma TG was reduced to near-normal levels (from 99.0 to 1.8 mmol/L), and plasma HDL-C was increased 6-fold (from 0.2 to 1.1 mmol/L). At 8 months after administration of AAV1-LPL(S447X), an intravenous lipid challenge showed efficient, near-normal clearance of plasma TG. Histologic analyses of injected muscle further indicated that abnormal muscle morphology observed in LPL -/- mice was reversed after treatment. Expression of therapeutic levels of LPL(S447X), and the subsequent beneficial effect on plasma lipid levels, has lasted for more than 1 year. We therefore conclude that AAV1-mediated transfer of LPL(S447X) into murine skeletal muscle results in long-term near-correction of dyslipidemia associated with LPL deficiency.

Gene therapy in clinical medicine

Although the field of gene therapy has experienced significant setbacks and limited success, it is one of the most promising and active research fields in medicine. Interest in this therapeutic modality is based on the potential for treatment and cure of some of the most malignant and devastating diseases affecting humans. Over the next decade, the relevance of gene therapy to medical practices will increase and it will become important for physicians to understand the basic principles and strategies that underlie the therapeutic intervention. This report reviews the history, basic strategies, tools, and several current clinical paradigms for application.

Efficient transduction of skeletal muscle using vectors based on adeno-associated virus serotype 6

Vectors based on recombinant adeno-associated viruses (rAAV) have emerged as tools of choice for gene transfer to skeletal muscle. rAAV vectors demonstrate efficient, safe, and stable transduction. Multiple serotypes of AAV exist, but vectors based on serotype 2 (rAAV2) are the most thoroughly characterized and frequently employed. Here, we characterize transduction of the skeletal musculature using rAAV vectors pseudotyped with serotype 6 capsid proteins (rAAV6). We demonstrate that rAAV6 vectors can efficiently transduce the skeletal musculature of mice at levels >500-fold higher than is achievable with rAAV2 vectors and can readily saturate individual muscles following direct injection. Further, rAAV6 vectors are capable of transducing the diaphragm and intercostal muscles of mice after a simple injection into the intrathoracic cavity and are capable of widespread transduction throughout the musculature of mice injected in the intraperitoneal space as newborn pups. These results demonstrate that rAAV6 vectors hold great potential for use in gene delivery protocols targeting the skeletal musculature.

Functional Characterization of a Recombinant Adeno- Associated Virus 5-Pseudotyped Cystic Fibrosis Transmembrane Conductance Regulator Vector

Despite extensive experience with recombinant adeno-associated virus (rAAV) 2 vectors in the lung, gene expression has been low in the context of cystic fibrosis (CF) gene therapy, where the large size of the cystic fibrosis transmembrane conductance regulator (CFTR) coding sequence has prompted the use of compact endogenous promoter elements. We evaluated the possibility that gene expression from recombinant adeno-associated virus (rAAV) could be improved by using alternate AAV capsid serotypes that target different cell-surface receptors (i.e., rAAV5) and/or using stronger promoters. The relative activities of the cytomegalovirus (CMV) Rous sarcoma virus (RSV) promoter, the CMV enhancer/beta-actin (CB) promoter combination, and the CMV enhancer/RSV promoter hybrid were assessed in vitro in a CF bronchial cell line. The CB promoter was the most efficient. AAV capsid serotypes, rAAV2 and rAAV5, were also compared, and rAAV5 was found to be significantly more efficient. Based on these studies a rAAV5-CB-promoter-driven CFTR minigene vector was then used to correct the CF chloride transport defect in vitro, as well as the hyperinflammatory lung phenotype in Pseudomonas-agarose bead challenged CF mouse lungs in vivo. These studies provide functional characterization of a new version of rAAV-CFTR vectors.

Gene delivery systems—gene therapy vectors for cystic fibrosis

Gene delivery systems (GDS) play a central role in the development of gene therapy strategies for Cystic Fibrosis (CF). Further, these systems are important tools in studies with cultured cells and in animal models. In this review, we describe the properties of several viral and synthetic gene delivery systems, and evaluate their possible application in gene therapy of CF. While many gene delivery systems give satisfactory results in cultured or animal studies, none of these systems has been shown to fulfil all the requirements of safety and efficacy for use in CF patients. The intact airway epithelium, the most important target in CF gene therapy, proves to be well protected against invading vector systems.

Recombinant adeno-associated virus as delivery vector for gene therapy--a review

Recombinant adeno-associated virus (rAAV) is one of the most promising delivery vectors for gene therapy, due to its nonpathogenic property, nonimmunogenecity to host, and broad cell and tissue tropisms. This article summarizes the biological characteristics of AAV; the procedures to prepare, purify, and characterize the rAAV for gene therapy applications; and some of the clinical trials utilizing rAAV as delivery vehicles. Also discussed are the current efforts to modify rAAV to change its tropism, the application of different promoters to accommodate specific transgene expression, and the strategy to expand its capacity.

Distinct classes of proteasome-modulating agents cooperatively augment recombinant adeno-associated virus type 2 and type 5-mediated transduction from the apical surfaces of human airway epithelia

Tripeptidyl aldehyde proteasome inhibitors have been shown to effectively increase viral capsid ubiquitination and transduction of recombinant adeno-associated virus type 2 (rAAV-2) and rAAV-5 serotypes. In the present study we have characterized a second class of proteasome-modulating agents (anthracycline derivatives) for their ability to induce rAAV transduction. The anthracycline derivatives doxorubicin and aclarubicin were chosen for analysis because they have been shown to interact with the proteasome through a mechanism distinct from that of tripeptidyl aldehydes. Our studies demonstrated that doxorubicin and aclarubicin also significantly augmented rAAV transduction in airway cell lines, polarized human airway epithelia, and mouse lungs. Both tripeptidyl aldehyde and anthracycline proteasome-modulating agents similarly augmented nuclear accumulation of rAAV in A549 and IB3 airway cell lines. However, these two cell types demonstrated cell specificity in the ability of N-acetyl-L-leucyl-L-leucyl-L-norleucine (LLnL) or doxorubicin to augment rAAV transduction. Interestingly, the combined administration of LLnL and doxorubicin resulted in substantially increased transduction (>2,000-fold) following apical infection of human polarized epithelia with either rAAV-2 or rAAV-5. In summary, the cell type specificity of LLnL and doxorubicin to induce rAAV transduction, together with the ability of these compounds to synergistically enhance rAAV transduction in polarized airway epithelial induction, suggests that these two classes of compounds likely modulate different proteasome functions that affect rAAV transduction. Findings from this study provide new insights into how modulation of proteasome function can be effectively used to augment rAAV transduction in airway epithelia for gene therapy of cystic fibrosis.

Enhancement of gene transfer with recombinant adeno-associated virus (rAAV) vectors into primary B-cell chronic lymphocytic leukemia cells by CpG-oligodeoxynucleotides

OBJECTIVE

Transduction of primary B-cell chronic lymphocytic leukemia (B-CLL) cells with recombinant adeno-associated virus (rAAV) vectors is dependent on preactivation of leukemic cells by CD40L. CpG-oligodeoxynucleotides (CpG-ODNs) are able to activate cytokine production and proliferation of B-CLL cells. Therefore CpG-ODNs were tested for their potential to enhance transgene expression in CLL cells.

MATERIALS AND METHODS

Using an optimized adenovirus-free packaging system, rAAV vectors coding for the enhanced green fluorescent protein (AAV/EGFP) were packaged and highly purified resulting in infectious titers up to 5 x 10(9)/mL. Cells obtained from patients with B-CLL were infected with AAV/EGFP at a multiplicity of infection of 100 while being stimulated with CpG-ODNs and/or CD40L-expressing HeLa/SF cells. Transgene expression was assessed after 48 hours by flow cytometry.

RESULTS

Stimulation of B-CLL cells by CpG-ODNs resulted in up-regulation of costimulatory molecules and G(1)/S-phase transition at similar levels compared to activation by HeLa/SF cells, but use of CpG-ODNs alone did not result in any efficient AAV/EGFP transduction. Combined stimulation of B-CLL cells with HeLa/SF cells and CpG-ODNs during AAV/EGFP transduction significantly enhanced transgene expression compared to feeder stimulation alone (p=0.004). In addition, the copy number per single cell was significantly increased by addition of CpG-ODNs as detected by quantitative real-time PCR (p=0.04). Use of self-complementary AAV vectors that are not dependent on target cell DNA synthesis did not result in increased transgene expression compared to single-stranded AAV vectors (p=0.30).

CONCLUSION

Stimulation by CD40L is crucial for efficient gene transfer into B-CLL cells by rAAV vectors, whereas transduction efficiency can be significantly enhanced by CpG-ODNs.

Endocrine aspects of cancer gene therapy

The field of cancer gene therapy is in continuous expansion, and technology is quickly moving ahead as far as gene targeting and regulation of gene expression are concerned. This review focuses on the endocrine aspects of gene therapy, including the possibility to exploit hormone and hormone receptor functions for regulating therapeutic gene expression, the use of endocrine-specific genes as new therapeutic tools, the effects of viral vector delivery and transgene expression on the endocrine system, and the endocrine response to viral vector delivery. Present ethical concerns of gene therapy and the risk of germ cell transduction are also discussed, along with potential lines of innovation to improve cell and gene targeting.

Repeated Adeno-Associated Virus Serotype 2 Aerosol-Mediated Cystic Fibrosis Transmembrane Regulator Gene Transfer to the Lungs of Patients With Cystic Fibrosis

STUDY OBJECTIVES

The primary objective was to determine the safety and tolerability of repeated doses of aerosolized adeno-associated serotype 2 vector containing cystic fibrosis transmembrane conductance regulator (CFTR) complementary DNA (cDNA) [tgAAVCF], an adeno-associated virus (AAV) vector encoding the complete human CFTR cDNA. Secondary objectives included evaluation of pulmonary function assessed by spirometry, lung abnormalities by high-resolution CT (HRCT), airway cytokines, vector shedding, serum neutralizing antibody to AAV serotype 2 (AAV2), and gene transfer and expression in a subset of subjects undergoing bronchoscopy with bronchial brushings.

DESIGN

Randomized, double-blind, placebo-controlled, phase II trial.

SETTING

Eight cystic fibrosis (CF) centers in the United States.

SUBJECTS

CF patients with mild lung disease, defined as FEV(1) > or =60% predicted.

INTERVENTIONS

Subjects were randomized to inhale three aerosolized doses of 1 x 10(13) deoxyribonuclease-resistant particles of tgAAVCF or matching placebo at 30-day intervals using the Pari LC Plus nebulizer (PARI; Richmond, VA).

MEASUREMENTS AND RESULTS

Of 42 subjects randomized, 20 subjects received at least one dose of tgAAVCF and 17 subjects received placebo. No difference in the pattern of adverse events or laboratory abnormalities was noted between the two treatment groups. Improvements in induced-sputum interleukin-8 (p = 0.03) and FEV(1) (p = 0.04) were observed at day 14 and day 30, respectively, in the group receiving tgAAVCF when compared to those receiving placebo. No significant differences in HRCT scans were noted. Vector shedding in sputum was observed at low levels up to 90 days after the third dose of vector. All subjects receiving tgAAVCF exhibited an increase (by at least fourfold) in serum AAV2-neutralizing antibodies and detectable levels in BAL fluid from five of six treated subjects undergoing BAL. Gene transfer but not gene expression was detected in a subset of six tgAAVCF subjects who underwent bronchoscopy.

CONCLUSIONS

Repeat doses of aerosolized tgAAVCF were safe and well tolerated, and resulted in encouraging trends in improvement in pulmonary function in patients with CF and mild lung disease.

Gene therapy in heart and lung disease

PURPOSE OF REVIEW

Gene therapy utilizes viral and non-viral vectors to transfer genetic material into a host in the hope of treating disease. This article will review the potential applications of gene therapy in the treatment of cardiac and pulmonary diseases.

RECENT FINDINGS

The results from several phase I and II clinical trials have recently been published. In patients with ischemic heart disease, evidence of coronary revascularization has been observed after the delivery of angiogenic factors. Several trials have demonstrated a reduction in anginal symptoms, increases in exercise tolerance, and objective improvements in myocardial perfusion. Evidence of the transfer of therapeutic genes has been observed in human trials of inherited pulmonary diseases. Unfortunately, there has been little evidence of clinical efficacy in these studies. A variety of gene therapy strategies are being explored in the treatment of thoracic malignancies. Partial antitumor responses have occurred in some of the subjects enrolled in these studies.

SUMMARY

Significant progress has been made in the field of gene therapy in the past decade. Data from these early animal and human clinical trials will provide important information to guide future studies.

Heat-shock treatment-mediated increase in transduction by recombinant adeno-associated virus 2 vectors is independent of the cellular heat-shock protein 90

Recombinant adeno-associated virus 2 (AAV) vectors transduction efficiency varies greatly in different cell types. We have described that a cellular protein, FKBP52, in its phosphorylated form interacts with the D-sequence in the viral inverted terminal repeat, inhibits viral second strand DNA synthesis, and limits transgene expression. Here we investigated the role of cellular heat-shock protein 90 (HSP90) in AAV transduction because FKBP52 forms a complex with HSP90, and because heat-shock treatment augments AAV transduction efficiency. Heat-shock treatment of HeLa cells resulted in tyrosine dephosphorylation of FKBP52, led to stabilization of the FKBP52-HSP90 complex, and resulted in approximately 6-fold increase in AAV transduction. However, when HeLa cells were pre-treated with tyrphostin 23, a specific inhibitor of cellular epidermal growth factor receptor tyrosine kinase, which phosphorylates FKBP52 at tyrosine residues, heat-shock treatment resulted in a further 18-fold increase in AAV transduction. HSP90 was shown to be a part of the FKBP52-AAV D-sequence complex, but HSP90 by itself did not bind to the D-sequence. Geldanamycin treatment, which disrupts the HSP90-FKBP52 complex, resulted in >22-fold increase in AAV transduction in heat-shock-treated cells compared with heat shock alone. Deliberate overexpression of the human HSP90 gene resulted in a significant decrease in AAV-mediated transduction in tyrphostin 23-treated cells, whereas down-modulation of HSP90 levels led to a decrease in HSP90-FKBP52-AAV D-sequence complex formation, resulting in a significant increase in AAV transduction following pre-treatment with tyrphostin 23. These studies suggest that the observed increase in AAV transduction efficiency following heat-shock treatment is unlikely to be mediated by HSP90 alone and that increased levels of HSP90, in the absence of heat shock, facilitate binding of FKBP52 to the AAV D-sequence, thereby leading to inhibition of AAV-mediated transgene expression. These studies have implications in the optimal use of recombinant AAV vectors in human gene therapy.

Pathophysiology and management of pulmonary infections in cystic fibrosis

This comprehensive State of the Art review summarizes the current published knowledge base regarding the pathophysiology and microbiology of pulmonary disease in cystic fibrosis (CF). The molecular basis of CF lung disease including the impact of defective cystic fibrosis transmembrane regulator (CFTR) protein function on airway physiology, mucociliary clearance, and establishment of Pseudomonas aeruginosa infection is described. An extensive review of the microbiology of CF lung disease with particular reference to infection with P. aeruginosa is provided. Other pathogens commonly associated with CF lung disease including Staphylococcal aureus, Burkholderia cepacia, Stenotrophomonas maltophilia, Achromobacter xylosoxidans and atypical mycobacteria are also described. Clinical presentation and assessment of CF lung disease including diagnostic microbiology and other measures of pulmonary health are reviewed. Current recommendations for management of CF lung disease are provided. An extensive review of antipseudomonal therapies in the settings of treatment for early P. aeruginosa infection, maintenance for patients with chronic P. aeruginosa infection, and treatment of exacerbation in pulmonary symptoms, as well as antibiotic therapies for other CF respiratory pathogens, are included. In addition, the article discusses infection control policies, therapies to optimize airway clearance and reduce inflammation, and potential future therapies.

Phase I trial of intranasal and endobronchial administration of a recombinant adeno-associated virus serotype 2 (rAAV2)-CFTR vector in adult cystic fibrosis patients: a two-part clinical study

Recombinant adeno-associated serotype 2-based vectors (rAAV2) possess a number of theoretical advantages for cystic fibrosis (CF) gene therapy because they elicit little or no inflammatory response and generally result in stable expression. rAAV2 vectors expressing the cystic fibrosis transmembrane conductance regulator (CFTR) gene have previously been shown to mediate stable correction of the CF defect in CF bronchial epithelial cells and stable expression of CFTR in rabbit and nonhuman primate models. Here we report the results of the first trial initiated with rAAV in humans, a phase I study in 25 adult and adolescent CF patients with mild to moderate lung disease. Doses of the rAAV-CFTR vector (tgAAVCF) ranging from 3 x 10(1) to 1 x 10(9) replication units (RU), which is equivalent to approximately 6 x 10(4) to 2 x 10(12) DNase resistant particles (DRP), were administered to one side of the nose and to the superior segment of the lower lobe of the right lung. Several adverse events were noted prior to and/or after vector delivery, but most of them appeared to be related to the endogenous CF lung disease or a result of the bronchoscopic procedures. Only one of the serious events was judged to be possibly vector-related (based on temporal association), and this event was a pulmonary exacerbation very similar to several others experienced by the same subject in the three months preceding vector delivery. Vector shedding was minimal throughout the study, and serum-neutralizing antibodies were detected after vector delivery to subjects in the highest dosage cohorts. Gene transfer as measured by DNA polymerase chain reaction (PCR) was not observed until cohort 10 in nasal and bronchial epithelia. Sporadic low-level copy numbers suggested gene transfer of anywhere from 0.002 copies per cell up to 0.5 copies per cell was possible; however, DNA PCR was positive in lungs prior to direct dosing suggesting aspiration from the nasal dosing. These data indicate the need for continued evaluation of rAAV-CFTR vectors in additional clinical trials.

Pathways of removal of free DNA vector ends in normal and DNA-PKcs-deficient SCID mouse hepatocytes transduced with rAAV vectors

Elucidation of the mechanisms of transformation of single-stranded (ss) recombinant adeno-associated virus (rAAV) vector genomes into a variety of stable double-stranded (ds) forms is key to a complete understanding of rAAV vector transduction in vivo. Ds monomer genome formation and cellular ds DNA break (DSB) repair pathways that remove free vector ends toxic to cells, presumably play a central role in this process. By delivering rAAV and naked ds linear DNA vectors into livers of DNA-dependent protein kinase catalytic subunit (DNA-PKcs)-deficient severe combined immunodeficiency (SCID) and wild-type mice, we demonstrate the presence of three major pathways for free ds vector end removal: (1) DNA-PKcs-dependent self-circularization, (2) DNA-PKcs-independent self-circularization, and (3) DNA-PKcs-independent concatemerization. By using the DNA-PKcs-independent pathways, mouse hepatocytes efficiently removed free ds rAAV vector ends even in the absence of DNA-PKcs. Our studies suggest a hierarchical organization of these processes; self-circularization is the preferred pathway over concatemerization, although the former has a limited capacity to remove free vector ends. These studies shed new light on the molecular mechanisms of rAAV vector transduction in vivo.

Non-viral gene transfer therapy for cystic fibrosis

Non-viral methods of gene transfer are being investigated to treat cystic fibrosis (CF) and include naked DNA, lipid-DNA complexes and complexes of DNA with polycations such as poly-L-lysine (poly K) or polyethylenimine (PEI), all of which can carry the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The most recent promising strategy is the use of polycation-DNA complexes, particularly those prepared with poly-K and substituted with polyethylene glycol. These complexes produced partial correction of the CF defect in a mouse model with minimal toxicity, and have advanced to clinical trial. Improvements in this and other non-viral methods are in process and include i). targeting the complexes to the desired cells using receptor ligands, ii). lessening toxicity by changing the mix of lipids or adding protective molecules to polycations, iii). modifying the plasmid DNA to reduce inflammatory CpG sequences and enhance intensity, duration and tissue specificity of expression, and iv). modification of the complexes to improve nuclear access.

Recombinant adeno-associated virus serotype 4 mediates unique and exclusive long-term transduction of retinal pigmented epithelium in rat, dog, and nonhuman primate after subretinal delivery

We previously described chimeric recombinant adeno-associated virus (rAAV) vectors 2/4 and 2/5 as the most efficient vectors in rat retina. We now characterize these two vectors carrying the CMV.gfp genome following subretinal injection in the Wistar rat, beagle dog, and cynomolgus macaque. Both serotypes displayed stable GFP expression for the duration of the experiment (6 months) in all three animal models. Similar to the AAV-2 serotype, AAV-2/5 transduced both RPE and photoreceptor cells, with higher level of transduction in photoreceptors, whereas rAAV-2/4 transduction was unambiguously restricted to RPE cells. This unique specificity found conserved among all three species makes AAV-2/4-derived vectors attractive for retinal diseases originating in RPE such as Leber congenital amaurosis (RPE65) or retinitis pigmentosa due to a mutated mertk gene. To provide further important preclinical data, vector shedding was monitored by PCR in various biological fluids for 2 months post-rAAV administration. Following rAAV-2/4 and -5 subretinal delivery in dogs (n = 6) and in nonhuman primates (n = 2), vector genome was found in lacrymal and nasal fluids for up to 3-4 days and in the serum for up to 15-20 days. Overall, these findings will have a practical impact on the development of future gene therapy trials of retinal diseases.

Production of clinical-grade recombinant adeno-associated virus vectors

Recombinant adeno-associated viral (rAAV) vectors are being evaluated in animal models and humans. Pre-clinical data demonstrating vector safety, efficiency and efficacy have been used to initiate human clinical trials. The clinical manufacture of rAAV vectors has supported phase I and phase II trials, showing that adeno-associated virus serotype 2 vectors are safe when administered to humans.

Taking stock of gene therapy for cystic fibrosis

The identification of the cystic fibrosis (CF) gene opened the way for gene therapy. In the ten years since then, proof of principle in vitro and then in animal models in vivo has been followed by numerous clinical studies using both viral and non-viral vectors to transfer normal copies of the gene to the lungs and noses of CF patients. A wealth of data have emerged from these studies, reflecting enormous progress and also helping to focus and define key difficulties that remain unresolved. Gene therapy for CF remains the most promising possibility for curative rather than symptomatic therapy.

Cytokine dysregulation in activated cystic fibrosis (CF) peripheral lymphocytes

Recent studies demonstrate in vivo and in vitro cytokine dysregulation in CF epithelial cells. To see if these abnormalities may be generalized to other cells expressing cystic fibrosis transmembrane conductance regulator (CFTR) but not directly exposed to local inflammation, we studied mRNA transcription, intracellular protein production and extracellular secretion of IL-2, IL-4, IL-5, IL-10 and interferon-gamma (IFN-gamma) from freshly isolated blood mononuclear and CD4+ T cells from CF patients and controls. Cells were activated by phorbol myristate acetate (PMA) and anti-CD3, PMA-ionomycin, or lipopolysaccharide (LPS) and assessed for cytokine mRNA transcription by semiquantitative reverse transcriptase-polymerase chain reaction, intracellular protein production by flow cytometry, and secretion by supernatant ELISA. Cytokine expression was highly stimulus-dependent. CF cells showed higher IL-10 transcription than control cells after maximal activation by LPS (P = 0.01); despite this, cytokine production and secretion were equivalent to controls. CF cells showed lower cellular IL-10 production after PMA-anti-CD3 activation (P = 0.002). CF cells secreted less IFN-gamma than control cells after maximal activation by PMA-anti-CD3 (1836 +/- 273 pg/ml versus 9635 +/- 3437 pg/ml, P = 0.04). IL-2, IL-4 and IL-5 regulation was similar to controls. We conclude that CF mononuclear cells show selective cytokine dysregulation after maximal activation, namely reduced IFN-gamma secretion and increased IL-10 mRNA without increased production or secretion. These findings extend defects described in respiratory epithelial cells to circulating immunoregulatory cells, suggesting a link between CF genotype and cytokine dysregulation.