Biology of E1-deleted adenovirus vectors in nonhuman primate muscle

Selection-free gene repair after adenoviral vector transduction of designer nucleases: rescue of dystrophin synthesis in DMD muscle cell populations

Duchenne muscular dystrophy (DMD) is a fatal X-linked muscle-wasting disorder caused by mutations in the 2.4 Mb dystrophin-encoding DMD gene. The integration of gene delivery and gene editing technologies based on viral vectors and sequence-specific designer nucleases, respectively, constitutes a potential therapeutic modality for permanently repairing defective DMD alleles in patient-derived myogenic cells. Therefore, we sought to investigate the feasibility of combining adenoviral vectors (AdVs) with CRISPR/Cas9 RNA-guided nucleases (RGNs) alone or together with transcriptional activator-like effector nucleases (TALENs), for endogenous DMD repair through non-homologous end-joining (NHEJ). The strategies tested involved; incorporating small insertions or deletions at out-of-frame sequences for reading frame resetting, splice acceptor knockout for DNA-level exon skipping, and RGN-RGN or RGN-TALEN multiplexing for targeted exon(s) removal. We demonstrate that genome editing based on the activation and recruitment of the NHEJ DNA repair pathway after AdV delivery of designer nuclease genes, is a versatile and robust approach for repairing DMD mutations in bulk populations of patient-derived muscle progenitor cells (up to 37% of corrected DMD templates). These results open up a DNA-level genetic medicine strategy in which viral vector-mediated transient designer nuclease expression leads to permanent and regulated dystrophin synthesis from corrected native DMD alleles.

Targeted gene therapy for the treatment of heart failure

Chronic heart failure is one of the leading causes of morbidity and mortality in Western countries and is a major financial burden to the health care system. Pharmacologic treatment and implanting devices are the predominant therapeutic approaches. They improve survival and have offered significant improvement in patient quality of life, but they fall short of producing an authentic remedy. Cardiac gene therapy, the introduction of genetic material to the heart, offers great promise in filling this void. In-depth knowledge of the underlying mechanisms of heart failure is, obviously, a prerequisite to achieve this aim. Extensive research in the past decades, supported by numerous methodological breakthroughs, such as transgenic animal model development, has led to a better understanding of the cardiovascular diseases and, inadvertently, to the identification of several candidate genes. Of the genes that can be targeted for gene transfer, calcium cycling proteins are prominent, as abnormalities in calcium handling are key determinants of heart failure. A major impediment, however, has been the development of a safe, yet efficient, delivery system. Nonviral vectors have been used extensively in clinical trials, but they fail to produce significant gene expression. Viral vectors, especially adenoviral, on the other hand, can produce high levels of expression, at the expense of safety. Adeno-associated viral vectors have emerged in recent years as promising myocardial gene delivery vehicles. They can sustain gene expression at a therapeutic level and maintain it over extended periods of time, even for years, and, most important, without a safety risk.

Emerging strategies for cell and gene therapy of the muscular dystrophies

The muscular dystrophies are a heterogeneous group of over 40 disorders that are characterised by muscle weakness and wasting. The most common are Duchenne muscular dystrophy and Becker muscular dystrophy, which result from mutations within the gene encoding dystrophin; myotonic dystrophy type 1, which results from an expanded trinucleotide repeat in the myotonic dystrophy protein kinase gene; and facioscapulohumeral dystrophy, which is associated with contractions in the subtelomeric region of human chromosome 1. Currently the only treatments involve clinical management of symptoms, although several promising experimental strategies are emerging. These include gene therapy using adeno-associated viral, lentiviral and adenoviral vectors and nonviral vectors, such as plasmid DNA. Exon-skipping and cell-based therapies have also shown promise in the effective treatment and regeneration of dystrophic muscle. The availability of numerous animal models for Duchenne muscular dystrophy has enabled extensive testing of a wide range of therapeutic approaches for this type of disorder. Consequently, we focus here on the therapeutic developments for Duchenne muscular dystrophy as a model of the types of approaches being considered for various types of dystrophy. We discuss the advantages and limitations of each therapeutic strategy, as well as prospects and recent successes in the context of future clinical applications.

Designed recombinant adenovirus type 5 vector induced envelope-specific CD8(+) cytotoxic T lymphocytes and cross-reactive neutralizing antibodies against human immunodeficiency virus type 1

BACKGROUND

A monoclonal antibody (mAb) 2F5 binds to the membrane-proximal external region (MPER) of the transmembrane subunit gp41 of human immunodeficiency virus type 1 (HIV-1) is known to broadly neutralize HIV-1 strains. The Adenovirus type 5 vector (Ad5) has been widely applied for HIV-1 vaccine, and hexon hypervariable region 5 (HVR5) is exposed on viral surface and easily target host immune responses against Ad5.

METHODS

We constructed a recombinant adenovirus type 5 vector (rAd5) with a 2F5-binding epitope (ELDKWA) of MPER on Ad5-HVR5. In addition, we developed rAd5 encoding the HIV-1(IIIB) envelope (Env) gene for the induction of Env-specific cellular immunity.

RESULTS

The virus titers of the constructed rAd5 were similar to that of the parental Ad5 vector. Furthermore, high-dose immunization of rAd5 induced Env-specific CD8(+) cells and high levels of anti-ELDKWA antibodies. Moreover, an in vitro HIV-1 neutralization assay indicated that ELDKWA-specific mAbs derived from rAd5-immunized mice neutralized a wide range of HIV-1 strains.

CONCLUSIONS

The present study outlines the development of an Ad5-based HIV-1 vaccine targeting the hypervariable regions of Ad5. The constructed rAd5 induced an HIV-1-specific cellular immune response and neutralizing antibodies against various strains of HIV-1 simultaneously.

Potential Use of Gene Transfer in Athletic Performance Enhancement

After only a short history of three decades from concept to practice, gene therapy has recently been shown to have potential to treat serious human diseases. Despite this success, gene therapy remains in the realm of experimental medicine, and much additional preclinical and clinical study will be necessary for proving the efficacy and safety of this approach in the treatment of diseases in humans. However, a potential complicating factor is that advances in gene transfer technology could be misused to enhance athletic performance in sports, in a practice termed "gene doping". Moreover, gene doping could be a precursor to a broader controversial agenda of human "genetic enhancement" with the potential for a significant long-term impact on society. This review addresses the possible ways in which knowledge and experience gained in gene therapy in animals and humans may be abused for enhancing sporting prowess. We provide an overview of recent progress in gene therapy, with potential application to gene doping and with the major focus on candidate performance-enhancement genes. We also discuss the current status of preclinical studies and of clinical trials that use these genes for therapeutic purposes. Current knowledge about the association between the natural "genetic make-up" of humans and their physical characteristics and performance potential is also presented. We address issues associated with the safety of gene transfer technologies in humans, especially when used outside a strictly controlled clinical setting, and the obstacles to translating gene transfer strategies from animal studies to humans. We also address the need for development and implementation of measures to prevent abuse of gene transfer technologies, and to pursue research on strategies for its detection in order to discourage this malpractice among athletes.

Current Status of Cardiovascular Gene Therapy

Gene transfer for the therapeutic modulation of cardiovascular diseases is an expanding area of gene therapy. During the last decade several approaches have been designed for the treatment of hyperlipidemias, post-angioplasty restenosis, hypertension, and heart failure, and for protection of vascular by-pass grafts and promotion of therapeutic angiogenesis. Adenoviruses (Ads) and adeno-associated viruses (AAVs) are currently the most efficient vectors for delivering therapeutic genes into the cardiovascular system. Gene transfer using local gene delivery techniques have been shown to be superior to less-targeted intra-arterial or intra-venous applications. To date, no gene therapy drugs have been approved for clinical use in cardiovascular applications. In preclinical studies of therapeutic angiogenesis, various growth factors such as vascular endothelial growth factors (VEGFs) and fibroblast growth factors (FGFs), have shown positive results. Gene therapy also appears to have potential clinical applications in improving the patency of vascular grafts and in treating heart failure. Post-angioplasty restenosis, hypertension, and hyperlipidemias (excluding homozygotic familial hypercholesterolemia) can usually be managed satisfactorily by conventional approaches, and are therefore less favored areas for gene therapy. The development of technologies that can ensure long-term, targeted, and regulated gene transfer, and a careful selection of target patient populations, will be very important for the progress of cardiovascular gene therapy in clinical applications.

Plasmid DNA vaccine-elicited cellular immune responses limit in vivo vaccine antigen expression through Fas-mediated apoptosis

Particularly potent cellular or humoral immune responses are needed to confer protection in animal models against such pathogens as HIV/SIV, Mycobacterium tuberculosis, and malarial parasites. Persistent, high-level vaccine Ag expression may be required for eliciting such potent and durable immune responses. Although plasmid DNA immunogens are being explored as potential vaccines for protection against these pathogens, little is known about host factors that restrict long-term plasmid DNA vaccine Ag expression in vivo. We observed rapid damping of transgene expression from a plasmid DNA immunogen in wild-type, but not in T cell-deficient mice. This damping of Ag expression was temporally associated with the emergence of Ag-specific cellular immune responses. A requirement for Fas and the appearance of apoptotic nuclei at the site of vaccine inoculation suggest that T cells induce Fas-mediated apoptosis of plasmid DNA vaccine Ag-expressing cells. These studies demonstrate that high levels of in vivo Ag expression are associated with high-frequency cellular immune responses that in turn rapidly down-regulate vaccine Ag expression in vivo. These findings argue that it may not be possible to maintain persistent, high-level production of vaccine Ag in vivo to drive persistent immune responses as long as vaccine Ag production can be limited by host immune responses.

Adenovirus-based prime-boost immunization for rapid vaccination against anthrax

Prime-boost vaccination using plasmid DNA and replication-defective adenovirus vectors has emerged as a highly effective strategy for vaccinating against viral pathogens. However, its ability to provide protection against bacterial disease has never been assessed. Here we evaluate prime-boost vaccination approaches for immunizing against anthrax. We show that mice primed with DNA and boosted with an adenovirus vector, both expressing domain four of Bacillus anthracis protective antigen (PA), have higher antibody and toxin-neutralizing titers than mice immunized with either single modality alone. DNA-primed/adenovirus-boosted mice also had significantly higher antibody and toxin-neutralizing titers than mice immunized with Anthrax Vaccine Adsorbed. High levels of antigen-specific interferon-gamma-secreting cells were present in vaccinated mice indicating that a cell-mediated immune response had also been stimulated. Both DNA-primed/adenovirus-boosted and adenovirus-primed/adenovirus-boosted mice were fully protected from Sterne strain spore challenge. We also show that a single injection with an adenovirus vector-expressing domain four of PA can provide partial protection from spore challenge 2 weeks after immunization and full protection 3 weeks after immunization. These results demonstrate that adenovirus-based prime-boost vaccination can provide rapid protection from anthrax and that this approach may be an effective strategy for immunizing against bacterial as well as viral pathogens.

Characterization of a permissive epitope insertion site in adenovirus hexon

A robust immune response is generated against components of the adenovirus capsid. In particular, a potent and long-lived humoral response is elicited against the hexon protein. This is due to the efficient presentation of adenovirus capsid proteins to CD4+ T cells by antigen-presenting cells, in addition to the highly repetitive structure of the adenovirus capsids, which can efficiently stimulate B-cell proliferation. In the present study, we take advantage of this immune response by inserting epitopes against which an antibody response is desired into the adenovirus hexon. We use a B-cell epitope from Bacillus anthracis protective antigen (PA) as a model antigen to characterize hypervariable region 5 (HVR5) of hexon as a site for peptide insertion. We demonstrate that HVR5 can accommodate a peptide of up to 36 amino acids without adversely affecting virus infectivity, growth, or stability. Viruses containing chimeric hexons elicited antibodies against PA in mice, with total immunoglobulin G (IgG) titers reaching approximately 1 x 10(3) after two injections. The antibody response contained both IgG1 and IgG2a subtypes, suggesting that Th1 and Th2 immunity had been stimulated. Coinjection of wild-type adenovirus and a synthetic peptide from PA produced no detectable antibodies, indicating that incorporation of the epitope into the capsid was crucial for immune stimulation. Together, these results indicate that the adenovirus capsid is an efficient vehicle for presenting B-cell epitopes to the immune system, making this a useful approach for the design of epitope-based vaccines.

Tumor immunity and prolonged survival following combined adenovirus-HSP72 and CEA-plasmid vaccination

We have studied the effects of recombinant adenoviruses as immune adjuvants for DNA vaccination. In a mouse model, using the weak immunogen carcinoembryonic antigen (CEA), anti-CEA IgG production was significantly higher and occurred earlier when immunization included a recombinant adenovirus together with CEA-plasmid DNA. Combined immunization with a recombinant adenovirus expressing the immunomodulatory molecule heat shock protein 72 (ADHSP72) and CEA-plasmid DNA resulted in CEA-specific T-cell activation capable of protecting mice from tumor formation with CEA expressing cells. Additionally, animals with CEA expressing tumors showed diminished tumor growth and prolonged survival when immunized with ADHSP72 and CEA-plasmid DNA compared to controls. Recombinant adenoviruses expressing immunomodulatory molecules such as HSP72 may be useful adjuvants for DNA vaccination.

Patterns of transgene expression and viral clearance from the transplanted liver following ex vivo adenovirus-mediated gene transfer

BACKGROUND/AIMS

In the rat liver transplant model, the liver graft can be transduced ex vivo by adenovirus encoding CTLA-4Ig (AdCTLA-4Ig) to achieve high level of immunosuppression in the liver after transplantation. To characterize the pattern of transgene expression following ex vivo gene transfer to the liver and examine whether immunosuppression would promote adenovirus persistence, we followed the life span of vector DNA and transgene expression in the transplanted liver.

METHODS

Rat liver grafts were perfused ex vivo with adenovirus carrying the reporter gene beta-galactosidase (AdlacZ). The period of transgene expression was assessed at predetermined intervals after transplantation into syngeneic, allogeneic or nude (athymic) recipients. Clearance of vector DNA was assessed by PCR analysis of liver DNA after transplantation.

RESULTS

Graft transduction with AdCTLA-4Ig or systemic cyclosporine treatment effectively abrogated the alloimmune response but did not result in sustained lacZ expression. The course of viral DNA clearance from the liver was also unaffected by immunosuppression as was the implied nucleolytic cleavage of viral DNA.

CONCLUSIONS

In the transplant setting, local expression of CTLA-4Ig or systemic immunosuppression does not solve the problem of viral clearance from the liver. Non-adaptive immune mechanisms may have a significant role in the host response to adenovirus after liver transplantation.

Inhibition of costimulation allows for repeated systemic administration of adenoviral vector in rhesus monkeys

Immunogenicity of recombinant adenoviral (Ad) vectors severely hampers the clinical development of gene therapy protocols using repeated vector administrations. Inhibition of costimulation by APCs was explored as a strategy to circumvent the immune response against Ad particles. This strategy was tested in rhesus monkeys, treated transiently with chimeric anti-human CD40 and anti-human CD86 antagonist monoclonal antibodies (MAbs) at the time of systemic administration of a recombinant Ad vector. After Ad vector administration in the absence of immunosuppressive treatment, transgene expression in the serum lasted about 3-4 weeks. All control animals developed a strong neutralizing antibody (NAb) response to the Ad particles, which totally prevented efficient administration of a second vector, as shown by the lack of transgene expression. Treatment with anti-CD40 and anti-CD86 chimeric MAbs delayed or blocked the development of a humoral response against Ad and the infiltration of CD8(+) lymphocytes into the liver. This resulted in (i) increased persistence of Ad-transduced cells after injection of a first vector encoding a nonimmunogenic transgene, and (ii) the possibility of readministering a second Ad vector with significant efficacy. In both respects, the combined blockade of CD40 and CD86 was more efficient than treatment with anti-CD40 alone. This study shows for the first time in non-human primates that blocking CD40 and CD86 costimulatory molecules represents a promising strategy to inhibit immune responses against an Ad vector injected systemically.

T cells cause acute immunopathology and are required for long-term survival in mouse adenovirus type 1-induced encephalomyelitis

Infection of adult C57BL/6 (B6) mice with mouse adenovirus type 1 (MAV-1) results in dose-dependent encephalomyelitis. Utilizing immunodeficient mice, we analyzed the roles of T cells, T-cell subsets, and T-cell-related functions in MAV-1-induced encephalomyelitis. T cells, major histocompatibility complex (MHC) class I, and perforin contributed to acute disease signs at 8 days postinfection (p.i.). Acute MAV-1-induced encephalomyelitis was absent in mice lacking T cells and in mice lacking perforin. Mice lacking alpha/beta T cells had higher levels of infectious MAV-1 at 8 days, 21 days, and 12 weeks p.i., and these mice succumbed to MAV-1-induced encephalomyelitis at 9 to 16 weeks p.i. Thus, alpha/beta T cells were required for clearance of MAV-1. MAV-1 was cleared in mice lacking perforin, MHC class I or II, CD4+ T cells, or CD8+ T cells. Our results are consistent with a model in which either CD8+ or CD4+ T cells are sufficient for clearance of MAV-1. Furthermore, perforin contributed to MAV-1 disease but not viral clearance. We have established two critical roles for T cells in MAV-1-induced encephalomyelitis. T cells caused acute immunopathology and were required for long-term host survival of MAV-1 infection.

Distribution and toxicity resulting from adenoviral vector administration to a single salivary gland in adult rats

BACKGROUND

We examined the distribution and toxicity associated with a single salivary gland administration of a recombinant adenoviral vector, AdCMVH3, encoding human histatin 3.

METHODS

Adult rats received different doses of AdCMVH3 (0, 106, 3 x 107, and 109 pfu; 50 microl) via the right submandibular gland and were followed for 15 days. Food consumption, weight gain, clinical appearance, and serum chemistry were monitored, and a necropsy was performed. Vector distribution was examined by polymerase chain reaction, and selected saliva samples were tested for replication-competent adenovirus (RCA).

RESULTS

All animals survived to sacrifice (days 2, 8, and 15), and appeared normal clinically. There were no differences in food consumption, weight gain, and serum chemistry. The only consistent necropsy findings were lymphoid infiltrates and necrosis in the target submandibular glands of high-dosage animals. AdCMVH3 detection was virus dose dependent, decreased with time, and at low dose preferentially observed in the targeted gland. No RCA was detected.

CONCLUSIONS

Salivary gland administration of 109 pfu AdCMVH3 elicits an initial focal pathologic response and wide tissue distribution. There is no associated systemic toxicity up to 15 days, and lower doses are primarily found in glands.

Autocrine stimulation by erythropoietin in transgenic mice results in erythroid proliferation without neoplastic transformation

Erythropoietin (Epo) autocrine stimulation has been implicated in erythroleukemia. To develop a model of Epo autocrine stimulation, we made transgenic mice using a construct that linked the human Epo gene to an erythroid-specific regulatory element, designated 5'HS-2, from the human beta-globin locus control region. We hypothesized that Epo gene expression would be targeted to erythroid cells in these mice, resulting in autocrine stimulation of erythroid progenitor cell growth in culture, and that chronic autocrine Epo stimulation would result in erythroleukemia. Transgenic mice containing intact copies of the 5'HS-2Epo construction had elevated hematocrits, reticulocyte counts and serum Epo levels and marked splenic enlargement. Analysis of RNA isolated from organs of transgenic mice revealed constitutive Epo mRNA expression primarily in spleen, blood and bone marrow. RNA samples from anemic transgenic mice revealed Epo gene induction only in the liver. Marrow derived from 5'HS-2Epo mice grew BFU-E in the absence of exogenous Epo. Despite observation of up to 2 years, no mouse developed erythroleukemia, demonstrating that Epo autocrine stimulation alone is insufficient for progression to malignancy. These studies show that 5'HS-2 can be used to target Epo gene expression to erythroid tissue. These mice could provide a model system for studying autocrine growth regulation.

Preexisting antiadenoviral immunity and regional myocardial gene transfer: modulation by nitric oxide

The utility of adenoviral vectors, currently used in cardiovascular gene transfer protocols, is limited by the brevity of transgene expression and by antiadenoviral immune responses. The effect of preexisting antiadenoviral immunity on intracardiac gene transfer or its modulation by nitric oxide is unknown. Adenoviral vectors, expressing the firefly luciferase gene (AdLuc) or the human nitric oxide synthase 3 (NOS3) gene (AdNOS3), were infused into the great cardiac vein of naive pigs or immunized pigs. Pigs were immunized by intravenous injection of control virus AdRR5 and the resulting neutralizing antibody titers (median, 1:178; p < 0.0001 vs. baseline) were similar to preexisting titers in 54% of randomly selected coronary artery bypass graft patients. In naive animals distribution of transgene expression in the left ventricular free wall was focal. In immunized pigs myocardial luciferase expression 3 days after AdLuc gene transfer was more than 1000-fold lower than in naive pigs, whereas no change in NOS3 transcript levels was detected after AdNOS3 gene transfer. Severe, grade III-IV mononuclear cell infiltration and myocyte apoptosis were observed in four of five AdLuc-infected, immunized animals, compared with low-level inflammation and apoptosis in five of six AdNOS3-infected pigs. Coinfusion of AdLuc and AdNOS3 in immunized pigs resulted in spatially colocalized transgene expression, reduced T cell-mediated inflammation, and myocyte apoptosis and was associated with 200-fold greater median reporter transgene expression levels in the subendocardium (1.0 x 10(3) light units [LU]/mg protein, n = 8, vs. 4.5 x 10(1) LU/mg protein in AdLuc- and AdRR5-coinfected pigs, n = 7, p = 0.02). Preexisting antiadenoviral immunity abrogates myocardial gene expression in pigs and is associated with severe inflammation and myocyte apoptosis. Intracardiac NOS3 gene transfer may reduce these barriers to adenovirus-mediated myocardial gene transfer.

Phase I study of direct administration of a replication deficient adenovirus vector containing the vascular endothelial growth factor cDNA (CI-1023) to patients with claudication

The long-term safety and efficacy of adenoviral delivery of growth factors in patients with peripheral arterial disease (PAD) is unknown. CI-1023 (Ad(GV)VEGF(121.10)) is a replication-deficient adenovirus encoding human vascular endothelial growth factor isoform 121. In this phase I trial, we investigated the safety and efficacy of CI-1023 in subjects with advanced claudication symptoms secondary to infra-inguinal disease. Eighteen subjects >35 years of age with a median ankle brachial index (ABI) at rest of 0.525 (interquartile range 0.4) and angiographic disease involving the infra-inguinal vessels underwent intramuscular injection of CI-1023 (4 x10(8) to 4 x10(10) particle units, n = 15) or placebo (n = 3). Eleven of 15 patients (73%) who received CI-1023 and 1 of 3 subjects (33%) who received placebo, completed 1 year of follow-up. Edema and rash were the most common early adverse event. One infra-inguinal bypass procedure occurred in each of the placebo and CI-1023 groups at days 29 and 104, respectively. One death (day 160) and 1 malignancy (day 274) occurred in the CI-1023 group. Conclusions on efficacy could not be made due to the small number of patients. However, there were encouraging trends in ABI at rest and peak walking time at follow-up.

Adeno-cosmid cloning vectors for regulated gene expression

BACKGROUND

Adenovectors are widely used for efficient delivery of genes into a variety of cell types and organisms. However, the construction of the desired vector/genes combination, especially if it involves the cloning of several gene cassettes, can be laborious due to the large size of these vectors. New methods are needed to simplify the construction of complex combinations of gene cassettes into adenovectors.

METHODS

Using simple cloning techniques and exploiting the lambda-phage packaging system, we devised efficient methods for the 'selection' of the desired vector constructs. Thus we generated a series of cosmids containing the adeno helper dependent (HD) backbone in which we inserted cis- and trans-acting tetracycline (tet) elements for the regulation of any gene of interest. One of these cosmids has been used to produce an HD adenovirus carrying a tetracycline-regulated gene expressing beta-galactosidase.

RESULTS

We have demonstrated that the adeno-cosmid system allows rapid and efficient cloning of genes of interest in helper dependent vectors, and described a prototype 'ready-to-use' vector in which any gene of interest can be easily expressed under the control of the tet system. The HD viruses produced with this novel methodology can be grown at high titers, can be easily separated from the helper adenovirus, and allow delivery and regulated gene expression in a variety of tissues.

CONCLUSIONS

Exploiting the lambda-packaging system, complex adeno constructs can be generated with a simple and reproducible protocol, which allows selection of the desired size construct, counterselecting for the frequently observed intramolecular recombinations and deletions.

Adenovirus-transduced lung as a portal for delivering alpha-galactosidase A into systemic circulation for Fabry disease

Gene therapy efforts have focused primarily on the use of either the liver or skeletal muscle as depot organs for the production of a variety of therapeutic proteins that act systemically. Here we examined the lung to determine whether it could function as yet another portal for the secretion of proteins into the circulation. Fabry disease is caused by a deficiency of the lysosomal hydrolase alpha-galactosidase A, resulting in the abnormal deposition of the glycosphingolipid globotriaosylceramide (GL-3) in vascular lysosomes. Pulmonary instillation of a recombinant adenoviral vector (Ad2/CMVHI-alpha(gal)) encoding human alpha-galactosidase A into Fabry mice resulted in high-level transduction and expression of the enzyme in the lung. Importantly, enzymatic activity was also detected in the plasma, liver, spleen, heart, and kidneys of the Fabry mice. The detection of enzymatic activity outside of the lung, along with the finding that viral DNA was limited to the lung, indicates that the enzyme crossed the air/blood barrier, entered the systemic circulation, and was internalized by the distal visceral organs. The levels of alpha-galactosidase A attained in these tissues were sufficient to reduce GL-3 to basal levels in the lung, liver, and spleen and to approximately 50% of untreated levels in the heart. Together, these results suggest that the lung may be a viable alternate depot organ for the production and systemic secretion of alpha-galactosidase A for Fabry disease.

Adenoviral gene therapy

As of May 2001, 532 gene therapy protocols had been approved for evaluation in clinical trials; however, only five of those had been evaluated in phase III clinical trials. Among the most commonly used vectors for the delivery of genetic material into human cells are the adenoviruses. Remarkable progress has been made with these vectors in the last decade, but some shortcomings continue to challenge investigators. The newly acquired knowledge of the adenoviral life cycle and the positive outcomes from phase II clinical trials have led to the application of vectors engineered to selectively target tumor tissue under controlled promoters.