Evaluation of the efficacy and safety of in vitro, adenovirus-mediated transfer of the human cystic fibrosis transmembrane conductance regulator cDNA

IgG-Complexed Adenoviruses Induce Human Plasmacytoid Dendritic Cell Activation and Apoptosis

Following repeat exposure to many human adenoviruses (HAdVs), most adults harbour long-lived B- and T-cell responses. Combined, this response typically protects us for years from re-infection by the same HAdV type. In spite of these immune responses, some HAdV types are associated with persistent infections that constitute a life-threatening risk when an individual’s T-cell response is compromised. By contrast, patients with B-cell deficiencies do not appear to be at a greater risk of HAdV disease. This dichotomy begs the question of the secondary role of anti-HAdV antibodies during host defence. In this study, we explored IgG-complexed (IC)-HAdV5 and primary human plasmacytoid dendritic cell (pDC) interactions. We found that IC-HAdV5 are efficiently internalized in pDCs, stimulate their activation through TLR9 signalling, and cause apoptosis. These data may help reconcile the enigma of robust immune response to HAdVs, while concurrently allowing persistence.

A helper-dependent adenoviral vector rescues CFTR to wild-type functional levels in cystic fibrosis epithelial cells harbouring class I mutations

Cystic fibrosis (CF) is a genetic disorder affecting multiple organs, including the pancreas, hepatobiliary system and reproductive organs; however, lung disease is responsible for the majority of morbidity and mortality. Management of CF involves CF transmembrane conductance regulator (CFTR) modulator agents including corrector drugs to augment cellular trafficking of mutant CFTR as well as potentiators that open defective CFTR channels. These therapies are poised to help most individuals with CF, with the notable exception of individuals with class I mutations where full-length CFTR protein is not produced. For these mutations, gene replacement has been suggested as a potential solution.In this work, we used a helper-dependent adenoviral vector (HD-CFTR) to express CFTR in nasal epithelial cell cultures derived from CF subjects with class I CFTR mutations.CFTR function was significantly restored in CF cells by HD-CFTR and reached healthy control functional levels as detected by Ussing chamber and membrane potential (FLIPR) assay. A dose-response relationship was observed between the amount of vector used and subsequent functional outcomes; small amounts of HD-CFTR were sufficient to correct CFTR function. At higher doses, HD-CFTR did not increase CFTR function in healthy control cells above baseline values. This latter observation allowed us to use this vector to benchmark in vitro efficacy testing of CFTR-modulator drugs.In summary, we demonstrate the potential for HD-CFTR to inform in vitro testing and to restore CFTR function to healthy control levels in airway cells with class I or CFTR nonsense mutations.

Cystic Fibrosis Gene Therapy: Looking Back, Looking Forward

Cystic fibrosis (CF) is an autosomal recessive disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene that encodes a cAMP-regulated anion channel. Although CF is a multi-organ system disease, most people with CF die of progressive lung disease that begins early in childhood and is characterized by chronic bacterial infection and inflammation. Nearly 90% of people with CF have at least one copy of the ΔF508 mutation, but there are hundreds of CFTR mutations that result in a range of disease severities. A CFTR gene replacement approach would be efficacious regardless of the disease-causing mutation. After the discovery of the CFTR gene in 1989, the in vitro proof-of-concept for gene therapy for CF was quickly established in 1990. In 1993, the first of many gene therapy clinical trials attempted to rescue the CF defect in airway epithelia. Despite the initial enthusiasm, there is still no FDA-approved gene therapy for CF. Here we discuss the history of CF gene therapy, from the discovery of the CFTR gene to current state-of-the-art gene delivery vector designs. While implementation of CF gene therapy has proven more challenging than initially envisioned; thanks to continued innovation, it may yet become a reality.

Humoral immune response to adenovirus induce tolerogenic bystander dendritic cells that promote generation of regulatory T cells

Following repeated encounters with adenoviruses most of us develop robust humoral and cellular immune responses that are thought to act together to combat ongoing and subsequent infections. Yet in spite of robust immune responses, adenoviruses establish subclinical persistent infections that can last for decades. While adenovirus persistence pose minimal risk in B-cell compromised individuals, if T-cell immunity is severely compromised reactivation of latent adenoviruses can be life threatening. This dichotomy led us to ask how anti-adenovirus antibodies influence adenovirus T-cell immunity. Using primary human blood cells, transcriptome and secretome profiling, and pharmacological, biochemical, genetic, molecular, and cell biological approaches, we initially found that healthy adults harbor adenovirus-specific regulatory T cells (T_regs). As peripherally induced T_regs are generated by tolerogenic dendritic cells (DCs), we then addressed how tolerogenic DCs could be created. Here, we demonstrate that DCs that take up immunoglobulin-complexed (IC)-adenoviruses create an environment that causes bystander DCs to become tolerogenic. These adenovirus antigen loaded tolerogenic DCs can drive naïve T cells to mature into adenovirus-specific T_regs. Our study reveals a mechanism by which an antiviral humoral responses could, counterintuitively, favor virus persistence.

While numerous studies have addressed the cellular and humoral response to primary virus encounters, relatively little is known about the interplay between persistent infections, neutralizing antibodies, antigen-presenting cells, and T-cell responses. Our studies suggests that if adenovirus–antibody complexes are taken up by professional antigen-presenting cells (e.g. dendritic cells), the DCs can generate an environment that causes bystander dendritic cells to become tolerogenic. These tolerogenic dendritic cells favors the creation of adenovirus-specific regulatory T cells. While this pathway likely favors pathogen survival, there may be advantages for the host also.

Efficient in vivo catheter-based pericardial gene transfer mediated by adenoviral vectors

Adenoviral vectors are promising agents for a number of in vivo gene therapy applications including diseases of the heart and coronary vessels. Efficient intravascular gene transfer to specific sites has been achieved in occluded vessels, but otherwise is hampered by the effect of blood flow on localized vector uptake in the vessel wall. An alternative delivery approach to coronary arteries is the expression of diffusible gene products into the pericardial space surrounding the heart and coronary arteries. However, in vivo pericardial access is comparatively difficult and has been limited to surgical approaches. We hypothesized that efficient adenovirus-mediated gene expression in pericardial lining mesothelium could be achieved by transmyocardial vector delivery to the pericardium. To evaluate this concept, a hollow, helical-tipped penetrating catheter was used to deliver vector-containing fluid directly into the intrapericardial space. The catheter was introduced percutaneously in anesthetized mongrel dogs, advanced into the right ventricle, and the tip passed through the apical right ventricular myocardium under direct radiographic visualization until the open end of the catheter tip resided in the intrapericardial space. Adenoviral vectors expressing either nuclear-localizing beta-galactosidase, cytoplasmic luciferase, or secreted human alpha 1AT reporters (Av1nBg, Av1Lu, or Av1Aa, respectively) were instilled through the catheter into the intrapericardial space. Three days later the animals were sacrificed and reporter gene expression was evaluated in pericardium, epicardium, and multiple other tissues. In animals receiving Av1nBg, beta-galactosidase activity was evident in most of the pericardial lining endothelium, up to 100% in many areas. In animals receiving Av1Lu, luciferase reporter activity was abundant in pericardial tissues, but near-background levels were observed in other organs. In animals receiving Av1Aa, human alpha 1AT was abundant (16-29 mg/ml) in pericardial fluid, but was undetectable in serum. All animals tolerated the procedure well with no electrocardiographic changes and no clinical sequelae. These observations demonstrate highly efficient adenovirus vector delivery and gene transfer and expression in the pericardium and support the feasibility of localized gene therapy via catheter-based pericardial approaches. We suggest that the pericardial sac may serve as a sustained-release protein delivery system for the generation of desired gene products or their metabolites for diffusion into the epicardial region.

Persistent expression of PEDF in the eye using high-capacity adenovectors

Ocular neovascularization, the growth of abnormal blood vessels in the eye, is a factor shared by the most common blinding diseases in developed countries. Pigment epithelium-derived factor (PEDF) is a potent antiangiogenic and neuroprotective protein that is normally produced in the eye. When delivered via an adenovector, PEDF can block the growth of new blood vessels and trigger the selective regression of abnormal vessels in animal models of ocular disease. Because of the absence of adenoviral genes, high-capacity (HC) adenovectors offer the potential for persistent transgene expression and enhanced tolerability. We have assessed the durability of PEDF expression and the induction of ocular inflammation following delivery of a PEDF-expressing HC adenovector compared to earlier generation vectors. The HC vector mediated prolonged PEDF expression in tissue-cultured pigmented epithelial cells and when delivered by intravitreal injection into the mouse eye. Delivery of first-generation adenovectors resulted in a dose-dependent increase in cytokine/chemokine gene expression, which correlated with the infiltration of inflammatory cells in the eye. In comparison, the levels of inflammatory gene expression and the intraocular infiltrate were substantially reduced following delivery of the HC vector. These results support the development of the HC adenovector gene delivery system for ocular disease.

An adenovirus type 5 (Ad5) amplicon-based packaging cell line for production of high-capacity helper-independent deltaE1-E2-E3-E4 Ad5 vectors

Production of multiply deleted adenoviral (Ad) vectors with increased cloning capacity and reduced immunogenicity to adenovirus gene products requires the concomitant generation of efficient packaging cell lines. High expression levels of the complementing genes must be achieved in a coordinated fashion with viral replication. This is a particularly difficult task in light of the significant cytotoxicity displayed by adenoviral proteins. To this end, we developed a novel adenovirus-based amplicon with an Epstein-Barr virus origin of replication, Ad type 5 (Ad5) inverted terminal repeats, all Ad5 early region 2 (E2) genes, and the early region 4 (E4) open reading frame 6 (ORF6) under the control of a tetracycline-dependent promoter. The amplicon (pE2) was stably maintained in multiple copies in the nuclei of 293 cells stably expressing the Epstein-Barr virus nuclear antigen 1 (EBNA1) and allowed replication as a linear DNA upon induction of E2 and ORF6 gene expression. A stable cell line (2E2) was generated by introducing pE2 into 293EBNATet cells expressing the tetracycline-dependent transcriptional silencer and the reverse Tet transactivator (rtTA2). Upon induction with doxicycline, 2E2 cells produced higher levels of polymerase, precursor terminal protein (pTP), and DNA binding protein than noninduced 2E2 cells infected with first-generation Ad5 vector and supported efficient amplification of a multiply deleted Ad5 vector lacking E1, E2, E3, and E4 genes (Ad5DeltaE(1-4)). The high cloning capacity of Ad5DeltaE(1-4) (up to 12.6 kb) was exploited to construct a vector encoding the entire hepatitis C virus (HCV) polyprotein. Infection of HeLa cells by the resulting vector showed high levels of correctly processed HCV proteins.

Induction and Inhibition of Innate Inflammatory Responses by Adenovirus Early Region Proteins

First-generation adenovirus (Ad) gene therapy vectors deleted for the E1A, E1B, and E3 regions and carrying foreign genes under the control of strong foreign promoters induce high-level innate inflammatory responses within the first 24 hrs after transduction. Both uptake of the capsid and expression of gene products encoded by the vector contribute to the innate inflammatory response. Natural infections by Ad are frequently asymptomatic, suggesting that Ad has potent methods of inhibiting inflammation. The inability of Ad vectors to counter inflammatory responses suggests that the products of the Ad genes deleted in vector construction play critical roles in inhibiting these responses. Genetic analysis of the roles of Ad early region gene functions in vivo demonstrated that a virus made replication-incompetent by deletion of the preterminal protein gene and deleted for the transcriptional activation function of E1A effectively inhibits the innate inflammatory processes induced by Ad vectors. The mechanism(s) by which the Ad early region proteins inhibit inflammation is complex, as certain early region proteins can promote as well as inhibit inflammation, depending on the genetic context of the virus. Understanding of the roles of the Ad gene products in the induction and inhibition of innate inflammatory functions offers potential for the development of non-inflammatory vectors as well as for understanding of the mechanisms by which inflammation is regulated.

Adenoviral vectors: development and application

One of the prerequisites for the successful application of gene vaccination and therapy is the development of efficient gene delivery vectors. The rate-limiting nature of vectors was clearly manifested during the first wave of gene therapy testing, resulting in the demand for more effective and suitable vector systems. Adenoviral (Ad) vectors have recently played a central role in the development of gene-vector technology due to their practical advantages and potential applications. A large number of preclinical and clinical studies both have generated an overwhelming amount of data and literature on this vector system. It is the intention of this article to provide a systematic and broad spectrum review of this system, outlining the principle, potential, and limitations, and evaluating the rational development of this delivery approach. Recombinant adenoviruses (Ad), helper cell lines, and related technologies have been developed and applied to many indications owing to progress in virological research, molecular and cellular biology, eukaryotic protein expression, recombinant vaccines, and gene therapy. The technical depth this article covers should be useful to both the experienced researcher and to beginners in this field.

Receptor Interactions Involved in Adenoviral-Mediated Gene Delivery After Systemic Administration in Non-Human Primates

Adenovirus serotype 5 (Ad5)-based vectors can bind at least three separate cell surface receptors for efficient cell entry: the coxsackie-adenovirus receptor (CAR), alpha nu integrins, and heparan sulfate glycosaminoglycans (HSG). To address the role of each receptor involved in adenoviral cell entry, we mutated critical amino acids in fiber or penton to inhibit receptor interaction. A series of five adenoviral vectors was prepared and the biodistribution of each was previously characterized in mice. To evaluate possible species differences in Ad vector tropism, we characterized the effects of each detargeting mutation in non-human primates after systemic delivery to confirm our conclusions made in mice. In non-human primates, CAR was found to have minimal effects on vector delivery to all organs examined including liver and spleen. Cell-surface alpha nu integrins played a significant role in delivery of vector to the spleen, lung and kidney. The fiber shaft mutation S*, which presumably inhibits HSG binding, was found to significantly decrease delivery to all organs examined. The ability to detarget the liver corresponded with decreased elevations in liver serum enzymes (aspartate transferase [AST] and alanine transferase [ALT]) 24 hr after vector administration and also in serum interleukin (IL)-6 levels 6 hr after vector administration. The biodistribution data generated in cynomolgus monkeys correspond with those data derived from mice, demonstrating that CAR binding is not the major determinant of viral tropism in vivo. Vectors containing the fiber shaft modification may provide for a detargeted adenoviral vector on which to introduce new tropisms for the development of targeted, systemically deliverable adenoviral vectors for human clinical application.

Adenovirus serotype 5 fiber shaft influences in vivo gene transfer in mice

Adenoviral vectors used in gene therapy are predominantly derived from adenovirus serotype 5 (Ad5), which infects a broad range of cells. Ad5 cell entry involves interactions with the coxsackie-adenovirus receptor (CAR) and integrins. To assess these receptors in vivo, we mutated amino acid residues in fiber and penton that are involved in receptor interaction and showed that CAR and integrins play a minor role in hepatic transduction but that integrins can influence gene delivery to other tissues. These data suggest that an alternative entry pathway exists for hepatocyte transduction in vivo that is more important than CAR or integrins. In vitro data suggest a role for heparan sulfate glycosaminoglycans (HSG) in adenovirus transduction. The role of the fiber shaft in liver uptake was examined by introducing specific amino acid changes into a putative HSG-binding motif contained within the shaft or by preparing fiber shaft chimeras between Ad5 and Ad35 fibers. Results were obtained that demonstrate that the Ad5 fiber shaft can influence gene transfer both in vitro and to the liver in vivo. These observations indicate that the currently accepted two-step entry pathway, which involves CAR and integrins, described for adenoviral infection in vitro, is not used for hepatic gene transfer in vivo. In contrast, alpha(v) integrins influence gene delivery to the lung, spleen, heart, and kidney. The detargeted vector constructs described here may provide a foundation for the development of targeted adenoviral vectors.

Uptake of plasmid/glycosylated polymer complexes and gene transfer efficiency in differentiated airway epithelial cells

BACKGROUND

We have studied gene transfer efficiency of glycosylated polylysines and glycosylated polyethylenimines as vectors in immortalized differentiated airway gland serous cells and primary cultures of human airway surface epithelial cells.

METHODS AND RESULTS

In both cell types, lactosylated PEI was more efficient for gene transfer than unsubstituted PEI and lactosylated polylysine which requires the presence of endosomolytic agents. However, for all the vectors tested, gene transfer efficiency was lower in differentiated cells as compared with poorly differentiated cells. The presence of membrane lectins, i.e. cell surface sugar-specific receptors, was evaluated using fluorescein-conjugated neoglycoproteins and microscopy or flow cytometry. In differentiated airway surface epithelial cells, membrane lectins were not expressed and plasmid DNA/fluorescein-conjugated glycosylated polymer complexes were not incorporated. This accounted in part for the lack of gene transfer efficiency in these cells. In contrast, in differentiated airway gland serous cells, expression of lectins and their endocytotic properties appeared to be similar to that observed in undifferentiated cells, and plasmid DNA/fluorescein-conjugated glycosylated polymer complexes were incorporated in similar amounts by cells in both differentiated states

CONCLUSIONS

Glycosylated PEI appears to be a promising gene delivery system since it is more efficient than the sugar-free polymer and does not require endosomolytic agents. However, in differentiated airway gland serous cells, a low gene transfer efficiency was observed that could not be attributed to low expression of membrane lectins or low uptake of glycosylated complexes. An impaired intracellular trafficking of glycosylated complexes in differentiated airway gland serous cells is suggested.

Adenoviral-mediated transfer of a lysostaphin gene into the goat mammary gland

As a step toward preventing and curing Staphylococcus aureus mastitis, an adenoviral-mediated gene transfer technique was used to enable mammary cells to synthesize and secrete lysostaphin, an anti-staphylococcal protein. A lysostaphin gene, modified for eukaryotic expression of the bioactive variant, Gln125,232-lysostaphin, was inserted into a replication deficient adenovirus by homologous recombination in 293 cells. The resulting adenoviral vector containing the modified lysostaphin gene (Ad-lys) was used to infect bovine mammary epithelial cells in vitro and caprine mammary cells in vivo. A similar adenoviral vector containing the Escherichia coli gene encoding beta-galactosidase (Ad-lacZ) was also evaluated. Transduction of cultured bovine cells by Ad-lacZ was confirmed by the presence of beta-galactosidase in fixed cells 48 h postinfection. Bovine cells transduced by Ad-lys secreted immunoreactive Gln125,232-lysostaphin (0.8 microg/ml) into media that had approximately 20% bioactivity compared with native lysostaphin. To evaluate transduction in vivo, udder halves of four nonlactating goats were exposed to 10(10) plaque-forming units (pfu) ofAd-lacZ by two intramammary infusions given 48 h apart. The animals were euthanized 24 h later, and extensive expression of beta-galactosidase was detected in cells lining the teat canals, with more moderate expression observed in adjoining mammary parenchyma. Udder halves of two other nonlactating goats were infused with 10(10) pfu of Ad-lys while contralateral udder halves received Ad-lacZ. The animals were euthanized 48 h postinfusion. In both animals, extensive expression of beta-galactosidase was detected in Ad-lacZ exposed teats. Immunoreative Gln125,232-lysostaphin was detectable in secretions from Ad-lys exposed glands 24 h postinfusion, increasing to approximately 1 microg/ml at 48 h postinfusion. As with cultured bovine mammary epithelial cells, the bioactivity of goat-derived Gln125,232-lysostaphin was approximately 20% of native lysostaphin. These results demonstrate that an adenoviral vector can be used to introduce a gene into the ruminant mammary gland, enabling the secretion of a bioactive form of lysostaphin.

AP-2alpha modulates human corticotropin-releasing hormone gene expression in the placenta by direct protein-protein interaction

Since AP-2alpha induces the expression of hPL, hCG and other syncytiotrophoblast-specific marker genes in cytotrophoblast cells during in vitro differentiation, we have examined whether AP-2alpha also induces hCRH gene expression during differentiation of cytotrophoblast cells. Infection of human cytotrophoblast cells in vitro with an adenovirus expressing AP-2alpha resulted in a twofold increase in hCRH mRNA levels, while infection with an adenovirus expressing a dominant/negative mutant of AP-2alpha inhibited basal hCRH mRNA levels by 40% and completely blocked the induction of hCRH mRNA by AP-2alpha. Transient transfection studies in AtT-20 and HepG2 cells indicated that the induction of hCRH mRNA levels was due, at least in part, to transcriptional activation of the hCRH gene. Gel mobility shift and immunoprecipitation assays strongly suggest that AP-2alpha induces hCRH gene expression by interacting with CREB and not by binding directly to the hCRH promoter.

Preparation of purified, sterilized, and stable adenovirus vectors using albumin

Cesium chloride ultracentrifugation combined with dialysis is a standard method for preparing a high titer of purified recombinant adenovirus. However, it was found that sterilization of the filter membrane after dialysis led to a complete loss of adenovirus activity. A virus pellet was visualized after centrifugation shortly and electron microscopy revealed an aggregation of recombinant virus within the filter membrane following dialysis with 10% (V/V) glycerol in phosphate buffered saline. The entrapment of aggregated adenovirus by the filter membrane explains why adenovirus activity is lost following sterilization. The addition of 1% albumin prevented viral aggregation and allowed the purified virus to retain its activity after filter sterilization. Furthermore, viral activity was retained within the 1% albumin solution for at least 1 week at 37 degrees C and for 2 weeks at 4 degrees C, whereas viral activity within the albumin-free solution was quickly lost.

The release of inflammatory cytokines from human peripheral blood mononuclear cells in vitro following exposure to adenovirus variants and capsid

Preclinical and clinical studies with adenoviral vectors have clearly illustrated the potential advantages of this gene transfer system. However, many studies have also demonstrated potent immune responses directed at both vector and transduced cells. We examined in vitro responses of human peripheral blood mononuclear cells (PBMC) to virus exposure as a model for this host response. PBMC were isolated from normal donors and incubated with wild-type adenovirus (Ad5), Ad5 variants deleted for segments of E1 and/or E3, and empty viral capsids. Proinflammatory cytokine release was monitored for 96 hr. Induction of TNF-alpha by intact virions was low although stimulation by empty capsid gave a significant and sustained response. Induction of IL-6, GM-CSF, and a panel alpha- and beta-chemokines by intact virions was prominent, often approaching results obtained with 2.5 microg/ml of lipopolysaccharide (LPS). Responses were generally independent of virion genetic composition and were only partially blunted when UV-inactivated virus was used. Dose-response data showed 100-fold increases in virion concentration produced a maximum 3-fold increase in cytokine release, suggesting saturation. Surprisingly, prominent stimulation occurred after addition of empty capsid, which typically provoked responses equivalent to those seen with LPS stimulation. We present arguments that cellular signal transduction mechanisms activated by binding of virions/capsids stimulate transcription of proinflammatory cytokine genes.

Gene therapy vectors harboring AFP regulatory sequences. Preparation of an adenoviral vector

Gene therapy for hepatocellular carcinoma (HCC) may be achieved by introducing a therapeutic gene under the control of transcriptional regulatory sequences of the alpha-fetoprotein (AFP) gene. Transcription of the human AFP gene is controlled positively by the promoter and the enhancer and negatively by the silencer. The AFP promoter is a 200-bp region immediately upstream of the AFP gene, and the enhancer is present between 3 and 4.9 kb upstream of the transcription initiation site. Two silencer regions have been identified upstream of the gene, one at -0.31 kb and the other at -1.75 kb. To achieve specific killing of HCC, adenoviral vectors carrying AFP regulatory sequences have been constructed. In this article, we describe the details of the preparation of an adenoviral vector designed to express the herpes simplex virus thymidine kinase gene under the control of the 4.9-kb AFP 5'-regulatory sequence. Treatment with this viral vector followed by ganciclovir resulted in specific killing of AFP-positive HCC transplanted in nude mice. Other viral vectors containing AFP-regulatory sequences are also discussed.

Downmodulation of bFGF-binding protein expression following restoration of p53 function

Angiogenesis is a requirement for solid tumor growth. Therefore, inhibition of this neovascularization is one mechanism by which restoration of wtp53 function may lead to tumor regression. Here we report that adenoviral vector-mediated wild-type p53 transduction results in growth inhibition of squamous cell carcinoma of the head and neck tumor cells both in vitro and in a xenograft mouse model. This growth inhibition is associated with the down-regulation of the expression of fibroblast growth factor binding protein, a secreted protein required for the activation of angiogenic factor basic FGF. These findings suggest that wtp53-induced tumor regression is due, at least in part, to antiangiogenesis mediated by the downmodulation of fibroblast growth factor binding protein.

Gene therapy of cystic fibrosis: the glycofection approach

Many cells express surface membrane lectins that selectively bind and carry glycoconjugates into intracellular endosomes; in addition, various intracellular membrane and soluble lectins act as shuttles between different compartments. On this basis, we developed glycosylated polycations, now called glycofectins (glycosylated polylysine and polyethyleneimine). Recently, we set up a simple way to transform oligosaccharides into glycosynthons suitable to substitute proteins or polymers. Glycofectins bind plasmid DNA leading to compact glycoplexes. Glycoplexes prepared with glycofectins were found to be much more active than naked plasmid to transfer genes to various types of cells including human airway epithelial and serous cells. The gene transfer efficiency was found to depend on the nature of the sugars borne by glycofectins. It appeared that the sugar-dependent efficiency was not only related to the uptake but also to the intracellular traffic of glycoplexes.

A Cre-expressing cell line and an E1/E2a double-deleted virus for preparation of helper-dependent adenovirus vector

Adenoviral vectors are attractive for the delivery of transgenes into mammalian cells because of their efficient transduction, high titer, and stability. The major concerns with using E1-deleted adenoviral vectors in gene therapy are the pathogenic potential of the virus backbone and the leaky viral protein synthesis that leads to host immune responses and a short duration of transgene expression. Helper-dependent (HD) adenoviral vectors that are devoid of all viral protein-coding sequences have significantly increased the safety and reduced the immunogenicity of these vectors. Currently available HD vectors depend on an E1-deleted adenovirus as a helper to provide viral proteins in trans. As a consequence, contamination with helper virus cannot be avoided in the HD vector preparation though it can be decreased to 0.01% using a Cre/loxP mechanism. Since the presence of E1-deleted helper virus may have substantial unwanted effects, we have developed a new Cre-expressing cell line based on an E1- and E2a-complementing cell. This new cell line can efficiently cleave the packaging region in the helper virus genome. We have also developed an E1 and E2a double-deleted helper virus. By using the CreE cell with the helper virus deleted in both the E1 and the E2a genes it may be possible to further improve the safety of the vectors.

Adenovirus infection increases iNOS and peroxynitrite production in the lung

Host inflammatory and immune responses limit viral gene expression after administration of replication-deficient adenoviruses to the lung. The current study asks whether inducible nitric oxide synthase (iNOS) expression and peroxynitrite generation accompanied the inflammatory response following intratracheal administration of adenovirus. Pulmonary iNOS mRNA and protein were increased 2, 7, and 14 days following administration of 2 x 10(9) plaque-forming units of recombinant adenovirus (Av1Luc1) to BALB/c mice. Adenovirus infection was associated with a marked increase in nitrotyrosine staining. Intense nitrotyrosine staining was observed in alveolar macrophages, respiratory epithelial cells, conducting airways, and alveolar spaces 2 days postinfection. Two weeks after exposure to adenovirus, nitrotyrosine staining was detected within alveolar macrophages, suggesting adenovirus enhanced the nitration of proteins that were subsequently taken up by alveolar macrophages. Western blot analysis using anti-nitrotyrosine antibody did not demonstrate accumulation of nitrated surfactant protein A (SP-A), although a small fraction of aggregated SP-A comigrated with a nitrotyrosine-positive protein. iNOS expression, peroxynitrite, and nitrotyrosine generation accompany and may contribute to inflammatory responses to adenovirus in the lung.

A PDZ-binding motif is essential but not sufficient to localize the C terminus of CFTR to the apical membrane

Localization of ion channels and transporters to the correct membrane of polarized epithelia is important for vectorial ion movement. Prior studies have shown that the cytoplasmic carboxyl terminus of the cystic fibrosis transmembrane conductance regulator (CFTR) is involved in the apical localization of this protein. Here we show that the C-terminal tail alone, or when fused to the green fluorescent protein (GFP), can localize to the apical plasma membrane, despite the absence of transmembrane domains. Co-expression of the C terminus with full-length CFTR results in redistribution of CFTR from apical to basolateral membranes, indicating that both proteins interact with the same target at the apical membrane. Amino acid substitution and deletion analysis confirms the importance of a PDZ-binding motif D-T-R-L> for apical localization. However, two other C-terminal regions, encompassing amino acids 1370–1394 and 1404–1425 of human CFTR, are also required for localizing to the apical plasma membrane. Based on these results, we propose a model of polarized distribution of CFTR, which includes a mechanism of selective retention of this protein in the apical plasma membrane and stresses the requirement for other C-terminal sequences in addition to a PDZ-binding motif.

A new vector system with inducible E2a cell line for production of higher titer and safer adenoviral vectors

Adenoviral vectors have been used in gene therapy and for vaccination. The major concerns with using adenoviral vectors are the pathogenic potential of the virus backbone and the generation of replication-competent adenovirus that may replicate in an uncontrolled manner, especially in immunocompromised patients. It is important to develop new vectors that are safer for clinical trials while maintaining high titer and efficient transduction. A new adenovirus vector production system was developed, which includes several vector backbone plasmids deleted for E2a and a new cell line expressing both E1 and E2a. The new cell line with the tTA-inducible E2a expression cassette can significantly increase the titer of E1/E2a-deleted vectors by four to five orders of magnitude upon withdrawal of tetracycline. Furthermore, there is no sequence overlap between the vector and the cellular DNA within the E2a open reading frame and downstream, making the generation of virus with wild-type E2a through homologous recombination substantially less likely. The new vector system may improve the safety of vectors for vaccination and cancer therapy and may also provide safer backbones for further vector development, such as helper-dependent and hybrid vectors.

Correction of glycogen storage disease type 1a in a mouse model by gene therapy

Glycogen storage disease type 1a (GSD-1a), characterized by hypoglycemia, liver and kidney enlargement, growth retardation, hyperlipidemia, and hyperuricemia, is caused by a deficiency in glucose-6-phosphatase (G6Pase), a key enzyme in glucose homeostasis. To evaluate the feasibility of gene replacement therapy for GSD-1a, we have infused adenoviral vector containing the murine G6Pase gene (Ad-mG6Pase) into G6Pase-deficient (G6Pase(-/-)) mice that manifest symptoms characteristic of human GSD-1a. Whereas <15% of G6Pase(-/-) mice under glucose therapy survived weaning, a 100% survival rate was achieved when G6Pase(-/-) mice were infused with Ad-mG6Pase, 90% of which lived to 3 months of age. Hepatic G6Pase activity in Ad-mG6Pase-infused mice was restored to 19% of that in G6Pase(+/+) mice at 7-14 days post-infusion; the activity persisted for at least 70 days. Ad-mG6Pase infusion also greatly improved growth of G6Pase(-/-) mice and normalized plasma glucose, cholesterol, triglyceride, and uric acid profiles. Furthermore, liver and kidney enlargement was less pronounced with near-normal levels of glycogen depositions in both organs. Our data demonstrate that a single administration of a recombinant adenoviral vector can alleviate the pathological manifestations of GSD-1a in mice, suggesting that this disorder in humans can potentially be corrected by gene therapy.

Enhanced radiosensitivity of malignant glioma cells after adenoviral p53 transduction

OBJECT

The goal of this study was to determine whether adenoviral vector-mediated expression of human wildtype p53 can enhance the radiosensitivity of malignant glioma cells that express native wild-type p53. The p53 gene is thought to function abnormally in the majority of malignant gliomas, although it has been demonstrated to be mutated in only approximately 30%. This has led to studies in which adenoviral transduction with wild-type human p53 has been investigated in an attempt to slow tumor cell growth. Recent studies suggest that reconstitution of wild-type p53 can render cells more susceptible to radiation-mediated death, primarily by p53-mediated apoptosis.

METHODS

Rat RT2 glioma cells were analyzed for native p53 status by reverse transcriptase-polymerase chain reaction and sequence analysis and for p53 expression by Western blot analysis. Clonogenic survival and the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling assay were used to characterize RT2 cell radiosensitivity and apoptosis, respectively, with and without prior transduction with p53-containing and control adenoviral vectors. Animal survival length was monitored after intracerebral implantation with transduced and nontransduced RT2 cells, with and without cranial radiation. The RT2 cells were demonstrated to express native rat wild-type p53 and to markedly overexpress human p53 following adenoviral p53 transduction. The combination of p53 transduction followed by radiation resulted in marked decreases in RT2 cell survival and increases in apoptosis at radiation doses from 2 to 6 Gy. Animals receiving cranial radiation after intracerebral implantation with RT2 cells previously transduced with p53 survived significantly longer than control animals (p<0.01).

CONCLUSIONS

The ability to enhance the radiosensitivity of malignant glioma cells that express wild-type p53 by using adenoviral transduction to induce overexpression of p53 offers hope for this approach as a therapeutic strategy, not only in human gliomas that express mutant p53, but also in those that express wild-type p53.

Adenovector-mediated gene delivery of interleukin-2 in metastatic breast cancer and melanoma: results of a phase 1 clinical trial

We conducted a phase 1 trial of direct injection of an E1, E3-deleted adenovirus encoding interleukin-2 (AdCAIL-2) into subcutaneous deposits of melanoma or breast cancer. Twenty-three patients were injected at seven dose levels (10(7)-10(10) p.f.u). Local inflammation was observed at the site of injection in 60% of patients, but side-effects were otherwise minor. Incomplete local tumor regression occurred at the site of injection in 24% of patients, but no conventional clinical responses were seen. Circulating CD4 and CD8 counts fell significantly 24 h after injection. Post-injection biopsies demonstrated tumor necrosis and lymphocytic infiltration with the predominant tumor-infiltrating cells both CD3- and CD8-positive. Vector-derived sequences were detected in 14 of 18 biopsies examined 7 days after injection and vector-derived hIL-2 mRNA was detected in 80% of 7-day biopsies processed after injection of 10(8) p.f.u. of AdCAIL-2 or higher. While IL-2 was detectable by ELISA in tumor biopsies at 48 h, no protein was detectable in injected tumors after 7 days and no circulating IL-2 was detectable at any time-point. No Ad5E1 sequences were detected either before or after injection indicating absence of replication-competent virus or endogenous E1-like sequence; furthermore, only rare vector shedding was detected. Anti-adenovirus and neutralizing antibody titers were elevated 1 month after injection in all patients. This trial therefore confirms the safety of use of adenoviral vectors for gene delivery in humans and demonstrates successful transgene expression even in the face of pre-existing immunity to adenovirus.

Attenuation of ANG II actions by adenovirus delivery of AT1 receptor antisense in neurons and SMC

Both central and peripheral renin-angiotensin systems (RAS) are important in the development and establishment of hypertension. Thus, introducing genes relevant to RAS into neuronal and vascular smooth muscle (VSM) cells, two major targets for angiotensin (ANG) II action, is a prerequisite in considering a gene therapy approach for the control of ANG-dependent hypertension. In this study, we explored the use of adenoviral (Ad) vector to transfer AT1 receptor antisense cDNA (AT1R-AS) into neuronal and VSM cells with the anticipation of attenuation of ANG II-mediated cellular actions. Incubation of neurons and VSM cells with viral particles containing AT1R-AS (Ad-AT1R-AS) resulted in a robust expression of AT1R-AS in a majority (approximately 80%) of the cells. The expression was persistent for at least 28 days and was associated with decreases in the immunoreactive AT1 receptor protein and the maximal binding for AT1 receptor in a time- and dose-dependent manner in both cell types. ANG II stimulation of [3H]thymidine incorporation in VSM cells and norepinephrine transporter gene expression in neuronal cells were attenuated by Ad-AT1R-AS infection. Uninfected cells or cells infected with adenovirus particles containing a mutant AT1 receptor sense cDNA showed no effects on either AT1 receptor or on attenuation of ANG II's cellular affects. These observations show, for the first time, that adenovirus can be used to deliver AT1 receptor mutant sense and antisense cDNAs into two major ANG II target tissues. This consequently influences AT1 receptor-mediated cellular actions of ANG II.

An academic centre for gene therapy research with clinical grade manufacturing capability

Huddinge University Hospital is a major teaching hospital affiliated with the Karolinska Institute in Southern Stockholm. For the past few years several groups have been working there in different areas of gene therapy relating to cancer, genetic and infectious diseases. However, a facility to produce clinical grade material under good manufacturing practice was lacking. To this end, Huddinge University Hospital has taken the initiative to open a Gene Therapy Research Center in 1996. This facility, which is unique of its kind in Scandinavia, is located in the Novum Research Park, Huddinge, and is a part of the existing Clinical Research Center. The newly built centre will allow clinicians and researchers to develop and produce vectors (viral and nonviral) for clinical trials and do basic research to understand the mechanisms of diseases. Although the centre will primarily serve the academic institutions it will also extend its facilities to other investigators in this field. The production unit is run in collaboration with the Faculty of Medicine, University of Lund. On-going projects include production of plasmid vectors for prevention of postangioplasty restenosis, DNA vaccine for HIV-1, cationic liposome DNA complexes for cystic fibrosis and retroviral vectors for HIV-1.

Expression of human cholesterol 7alpha-hydroxylase in atherosclerosis-susceptible mice via adenovirus infection

Adenovirus is a vector for the delivery of genes mainly to the liver. Short-term (approximately 3 days) studies using adenovirus transfection have provided valuable insights into how genes can complement normal and pathological phenotypes. When atherosclerosis-susceptible C57BL/6 mice were infected with an adenovirus vector containing the human 7alpha-hydroxylate cDNA (AV17h1) and fed on a chow diet, human 7alpha-hydroxylase mRNA and enzyme activity doubled compared with that in mice infected with an adenovirus vector (AV1Null) alone. In AV17h1-infected mice fed on a high fat cholic acid (HFCA) diet, mRNA expression and activity of both the endogenous and adenovirus (human) 7alpha-hydroxylase were repressed. AV17h1-infected mice fed on a HFCA diet and killed at mid-light had increased 7alpha-hydroxylase activity and mRNA compared with mice killed at mid-dark. Since expression of AV17h1 is driven by a constitutive Rous sarcoma virus promoter, the repression of human 7alpha-hydroxylase by the HFCA diet was unexpected. In spite of this post-transcriptional repression by the HFCA diet, AV17h1-infected mice expressed the human 7alpha-hydroxylase mRNA, causing its enzyme activity to be 3-fold greater than in AV1Null-infected mice. In AV17h1-infected mice, the 7alpha-hydroxylase enzyme activity varied as a linear function of human mRNA abundance. In conclusion, the accumulation of apolipoprotein B-containing lipoproteins in plasma of C57BL/6 mice fed on the HFCA diet was not reduced by longer-term (2 weeks) 7alpha-hydroxylase expression, probably because of its diminished expression caused by the diet and hepatic inflammation from the adenovirus infection. These results may suggest that adenovirus is effective in promoting longer-term (2 weeks) expression of 7alpha-hydroxylase.

Increased contact time improves adenovirus-mediated CFTR gene transfer to nasal epithelium of CF mice

Multiple dosing with recombinant adenoviral vectors containing the cystic fibrosis transmembrane conductance regulator (CFTR) cDNA to the nasal mucosa of cystic fibrosis (CF) transgenic mice reportedly results in only partial correction of the CF defect in chloride (Cl-) secretion without normalizing sodium (Na+) hyperabsorption, perhaps indicating inefficient gene transfer into the nasal airway epithelium in vivo. In this study, we have examined whether optimizing vector administration such as contact time could improve gene transfer efficiency. Changes in basal nasal potential difference (PD), and in PD (delta PD) following addition of amiloride and subsequent removal of Cl- from the luminal perfusate were assayed. As reported previously, the basal nasal PD was significantly more negative in CF mice (-24.9 +/- 2.1 mV) than in normal mice (-6.3 +/- 1.2 mV). Normal mouse nasal mucosa exhibited a large hyperpolarization in response to low Cl- substitution (delta PD of 8.5 +/- 1.9 mV), whereas the nasal mucosa of the CF mouse depolarized in response to this treatment. No correction of either the Cl- or Na+ transport defects were observed when 5 x 10(9) IU of Ad2/CFTR-5 were administered to the nasal passage of CF mice over a period of 5-20 min. However, when CF mice were perfused over a period of 60 min with the same dose of vector, a significant response (delta PD of 5.9 +/- 1.1 mV) to low Cl- substitution was detected 2 days later. In these mice, the basal nasal PD (-10.5 +/- 1.4 mV) and the response to amiloride were also reduced, indicating a partial correction of the Na+ transport defect. Expression of functional CFTR activity was transient with no measurable delta PD signals observed by day 7 post-treatment. These results suggest that prolonging the contact between an adenoviral vector and the respiratory epithelium enhances the efficiency of gene transfer and can result in improved correction of the CF Na+ and Cl- ion transport defects. Therefore, strategies that improve internalization of viral vectors and that prolong their contact time with target cells may result in the improved clinical efficacy of such vectors.

Generation, validation, and large scale production of adenoviral recombinants with large size inserts such as a 6.3 kb human dystrophin cDNA

Human, serotype 5 (Ad 5), replication-defective recombinant adenoviruses (AdVs) expressing a 6.3 kb partial dystrophin cDNA (Becker) under the control of either the CMV early or the RSV LTR promoter/enhancer in combination with various polyadenylation sequences (polyA), were developed for gene transfer studies aimed at Duchenne muscular dystrophy. Based on previous experience, a strategy for generation, screening and validation of AdVs with relatively large size gene expression cassette inserts was established. Here we focus on some aspects of stability and safety of such AdVs as gene therapeutic tools based on relevant molecular biological methods. Furthermore, the quality of our best AdV-minidystrophin construct was validated following its large scale production and purification as well as its delivery in mdx mice. These results are of interest for establishing other AdVs, where the combined length of a tissue specific promoter, the gene of interest and the polyA sequences reach the upper limit of the packaging capacity of first generation AdVs.

Interleukin-2 gene transduction into freshly isolated lung adenocarcinoma cells with adenoviral vectors

We evaluated the efficiency of gene transduction and of gene expression by adenoviral vectors in human lung adenocarcinoma cells. Freshly isolated cancer cells were collected from pleural effusions in adenocarcinoma patients by centrifugation with a Percoll gradient. Adenoviral vectors resulted in effective gene transduction into human lung cancer cell lines and into freshly isolated lung adenocarcinoma cells. In an experiment using the beta-galactosidase (LacZ) gene, the Adex1CA vector with a regulatory sequence of chicken beta-actin as promoter and an enhancer derived from cytomegalovirus produced a higher transduction ratio and greater expression levels than adenoviral vectors with other promoter systems. Transduction with Adex1CA vectors containing the human interleukin-2 (IL-2) gene (Adex1CAhIL-2) resulted in enhanced secretion of IL-2 from gene-modified lung cancer cells. Treatment with normal human serum inhibited gene transduction by Adex1CAhIL-2 but did not inhibit gene expression after transduction by Adex1CAhIL-2. The secretion of IL-2 from the gene-modified cells, which were irradiated at 100 Gy before transduction, continued for 8 days. In a mouse model, the intrapleural injection of IL-2 gene-modified 3LL cells transduced by Adex1CAhIL-2 could cure the pre-existing lung tumours with malignant pleural effusions to induce tumor-specific immunity. But these therapies did not show any therapeutic benefit on the pre-existing tumor in subcutaneous region. These data suggest a potentially useful but limited clinical role of Adex1CAhIL-2 in gene therapy for lung cancer patients.

Characterization of factors involved in modulating persistence of transgene expression from recombinant adenovirus in the mouse lung

One potential limitation of adenovirus (Ad)-based vectors for the gene therapy of cystic fibrosis (CF) and other genetic diseases is the transience of expression observed in most in vivo systems. In this study, the influence of various factors on persistence of transgene expression in the lung was investigated. In the absence of immune pressure, such as in the nude mouse, the genomic structure of the vector was found to be predominant in determining the persistence of expression; Ad vector constructs with an E1-E3+E4ORF6+ backbone encoding beta-galactosidase (beta-Gal) or the cystic fibrosis transmembrane conductance regulator (CFTR) produced declining levels of expression while an Ad/CMV beta Gal vector with an E1-E3+E4+ backbone gave rise to sustained, long-term reporter gene expression. The ability of the latter vector to persist was in turn limited in part by the presence of cytotoxic T lymphocytes (CTLs). Adoptive transfer experiments indicated that CTLs directed against either viral proteins or the beta-Gal reporter gene product were able to reduce expression in nude C57BL/6 mice stably expressing beta-Gal from the E4+ vector. Finally, the specificity and strength of the CTL response elicited by Ad vector was found to vary considerably depending on mouse strain haplotype. These results indicate that persistence of transgene expression in a given system is determined by the interplay between several factors including genomic structure of the vector, host background, and immune response.

Evaluation of the concentration and bioactivity of adenovirus vectors for gene therapy

Development of adenovirus vectors as potential therapeutic agents for multiple applications of in vivo human gene therapy has resulted in numerous preclinical and clinical studies. However, lack of standardization of the methods for quantifying the physical concentration and functionally active fraction of virions in these studies has often made comparison between various studies difficult or impossible. This study was therefore carried out to define the variables for quantification of the concentration of adenovirus vectors. The methods for evaluation of total virion concentration included electron microscopy and optical absorbance. The methods for evaluation of the concentration of functional virions included detection of gene transfer (transgene transfer and expression) and the plaque assay on 293 cells. Enumeration of total virion concentration by optical absorbance was found to be a precise procedure, but accuracy was dependent on physical disruption of the virion to eliminate artifacts from light scattering and also on a correct value for the extinction coefficient. Both biological assays for enumerating functional virions were highly dependent on the assay conditions and in particular the time of virion adsorption and adsorption volume. Under optimal conditions, the bioactivity of the vector, defined as the fraction of total virions which leads to detected target cell infection, was determined to be 0.10 in the plaque assay and 0.29 in the gene transfer assay. This difference is most likely due to the fact that detection by gene transfer requires only measurement of levels of transgene expression in the infected cell whereas plaque formation is dependent on a series of biological events of much greater complexity. These results show that the exact conditions for determination of infectious virion concentration and bioactivity of recombinant adenovirus vectors are critical and must be standardized for comparability. These observations may be very useful in comparison of data from different preclinical and clinical studies and may also have important implications for how adenovirus vectors can optimally be used in human gene therapy.

Development of a complementing cell line and a system for construction of adenovirus vectors with E1 and E2a deleted

Although adenovirus vectors offer many advantages, it would be desirable to develop vectors with improved expression and decreased toxicity. Toward this objective, an adenovirus vector system with deletion of both the El and E2a regions was developed. A 5.9-kb fragment of the adenovirus type 5 (Ad5) genome containing the E2a gene and its early and late promoters was transfected into 293 cells. A complementing cell line, designated 293-C2, expressed the E2a mRNA and protein and was found to complement the defect in Ad5 viruses with temperature-sensitive or deletion mutations in E2a. A deletion of 1.3 kb removing codons 40 to 471 of the 529 amino acids of E2a was introduced into plasmids for preparation of viruses and vectors. An Ad5 virus with disruption of the El gene and deletion of E2a grew on 293-C2 cells but not on 293 cells. Vectors with E1 and E2a deleted expressing Escherichia coli beta-galactosidase or human alpha1-antitrypsin were prepared and expressed the reporter genes after intravenous injection into mice. This vector system retains sequences in common between the complementing cell line and the vectors, including 3.4 kb upstream and 1.1 kb downstream of the deletion. These vectors have potential advantages of increased capacity for insertion of transgene sequences, elimination of expression of E2a, and possibly reduction in expression of other viral proteins. Although the titers of the vectors with deleted are about 10- to 30-fold below those of vectors with E2a wild-type regions, the former vectors are suitable for detailed studies with animals to evaluate the effects on host immune responses, on duration of expression, and on safety.

Infection of A549 cells with a recombinant adenovirus vector induces ICAM-1 expression and increased CD-18-dependent adhesion of activated neutrophils

A significant number of pulmonary exacerbations in patients with cystic fibrosis (CF) and asthma are associated with respiratory virus infections. The molecular mediators of this process are beginning to be understood. Viral infection of respiratory epithelial cultures in vitro leads to the production of intercellular adhesion molecule-1 (ICAM-1) (a ligand for inflammatory cell adhesion and activation) and a number of proinflammatory cytokines. Human gene therapy vectors derived from human adenoviruses (AV) are currently under evaluation for CF transmembrane regulator (CFTR) gene delivery to the airway epithelium of CF patients. However, studies in animal models using these AV vectors demonstrate pulmonary inflammation following AV exposure. Using an in vitro model, we examined the hypothesis that exposure of respiratory epithelial cells to AV vectors results in upregulation of ICAM-1 gene expression. Infections were performed using a replication-deficient, first-generation AV vector. A549 cells (a human pulmonary adenocarcinoma cell line) were exposed to AV at multiplicity of infection of 50-150 plaque-forming units/cell (resulting in > 90% of cells expressing the reporter gene by 48 hr following exposure). Measurements of ICAM-1 expression were made at time intervals following virus exposure using enzyme immunoassay, flow cytometry, and Northern blot analysis. Cell-bound ICAM-1 was significantly increased 96 hr following vector exposure, two to four times control, p < 0.001). The AV-exposed A549 cells also supported increased levels of adhesion of activated neutrophils 96 hr following AV exposure (four times control, p < 0.001) that was blocked by antibody to CD18. AV exposure of A549 monolayers increases expression of biologically active ICAM-1. Strategies to minimize host cellular proinflammatory responses to the replication-deficient AV vectors may improve their safety for gene therapy.

Efficient adenovirus-mediated gene transfer to basal but not columnar cells of cartilaginous airway epithelia

Adenoviral vectors (AdV) developed for treatment of the pulmonary manifestations of cystic fibrosis (CF) can deliver, with high efficiency, transgenes to respiratory epithelial cells grown in culture. This study investigated the efficiency of AdV-mediated gene transfer to murine and human respiratory epithelium in vivo and concluded that the epithelial cells facing the lumen of the respiratory cartilaginous airways (columnar cells) are poorly transduced with AdV. Mechanical injury to the epithelium, however, leads to efficient in vivo gene transfer by exposing a susceptible epithelial subtype (basal cells). Increased gene transfer efficiency in vivo after injury is not a nonspecific response because the proliferative status of the epithelium after injury was shown not to correlate temporally to the increased transduction susceptibility of the epithelium. Although basal cells were the cell type transduced at the time of vector delivery, with time, basal cell differentiation to columnar cells occurred with maintenance of transgene expression. Collectively, these results show that murine and human cartilaginous airways are poorly transduced by AdV. To correct the cartilaginous airway CF bioelectrical defect in vivo, efforts should be directed to increase the tropism of AdV to the columnar airway epithelial cells.

Surfactant effects on aerosolized and instilled adenoviral-mediated gene transfer

The effects of surfactant on aerosolization of adenovirus and the distribution of aerosolized and instilled adenovirus in rabbit lungs were measured. Using 99Tc sulfur colloid as a marker for the aerosol, 33P-adenovirus with and without 3H-surfactant, we found that the aerosol had the same particle size distribution independent of surfactant and the 33P-adenovirus distributed proportionately to the other radiolabels in the aerosol. Rabbits received aerosolized or instilled suspensions of adenovirus and 99Tc-sulfur colloid with or without 10 mg/ml surfactant. Rabbit lungs were separated into large airways (trachea, carina, and primary bronchi) and more distal lung parenchyma either immediately after treatment for measurement of 99Tc distribution or 3 days after treatment for luciferase transgene expression. More instillate (94 +/- 1%) than aerosol (68 +/- 2%) was recovered in the parenchyma immediately after treatment (p < 0.01). Transgene expression in the parenchyma as a percent of total lung expression was lower for both instillation (72 +/- 8%) and aerosolization (30 +/- 8%) than for the initial distributions (p < 0.01). Surfactant did not change the distributions of 99Tc sulfur colloid or transgene expression. The adenovirus was aerosolized successfully but the distribution of the aerosol did not favor transgene expression in the lung parenchyma.

Safety of adenovirus-mediated transfer of the human cystic fibrosis transmembrane conductance regulator cDNA to the lungs of nonhuman primates

To define the toxicity of cystic fibrosis transmembrane conductance regulator gene (CFTR) gene therapy with a replication-deficient recombinant adenovirus (Av1Cf2) in a nonhuman primate model, 10(10) plaque forming units (pfu) were instilled directly through a bronchoscope into the right lung of 5 macaques, and a lower dose of 4 x 10(6) pfu was administered to the right lung of 1 macaque. One sham-treated control received phosphate-buffered saline (PBS). The macaques were evaluated sequentially by clinical examination, vital signs, weight, hematology, blood chemistry, chest radiography, pulse oximetry, and bronchoalveolar lavage (BAL) at baseline and 3-28 days post-treatment. After the period of observation, macaques were sacrificed for autopsy and histological examination. The macaques tolerated the experimental therapy clinically with no changes in body temperature, oxygen saturation, heart rate, body weight, or blood pressure. However, 1 macaque with visible evidence of aspiration at the time of initial bronchoscopy developed tachypnea with right lower lobe (RLL) pneumonia on chest radiograph and by histology. There were no changes in Hgb, Wbc, BUN, plasma electrolytes, bilirubin, or hepatic transaminases. In the macaques that received 10(10) pfu, there was a progressive increase in the number of CD8+ lymphocytes in BAL that was maximal at 28 days. Histological examination of the treated lungs of the high-dose macaques at 3 days showed marked peribronchial and perivascular cuffing by inflammatory cells and alveolar accumulation of neutrophils and macrophages. The alveolitis appeared to be resolving at 28 days, although the perivascular and peribronchial aggregates of mononuclear cells were still present. In the high-dose macaques, BAL interleukin-8 (IL-8) was increased at all time points (256-388 pg/ml versus 1-84 pg/ml at baseline and in control), whereas IL-1 beta was increased only at days 21 and 28 (341-852 pg/ml versus 30-92 pg/ml at baseline and in control). There were no increases in BAL cell counts, IL-1 beta or IL-8, and histological changes were mild in the macaque that received 4 x 10(6) pfu. Evaluation for Av1Cf2-derived human CFTR expression using RS-PCR demonstrated expression at 3, 10, and 21, but not 28 days in macaques treated with 10(10) pfu of Av1Cf2. In situ hybridization analysis demonstrated human CFTR mRNA in the alveolar regions of the lobes that received the vector at 10 and 21 days. There was no evidence of expression after treatment with 4 x 10(6) pfu. This study showed that high-dose adenoviral vector administration to the lung achieved CFTR gene transfer and expression but was associated with increased concentrations of cytokines in BAL and alveolar inflammation. A low dose, equivalent to the maximum clinical dose currently proposed for phase I trials in human subjects, was not associated with cellular or cytokine evidence of inflammation, and histological abnormalities were mild.

Effect of adenoviral vector infection on cell proliferation in cultured primary human airway epithelial cells

Although recombinant adenoviruses are used as vectors for delivering therapeutic genes to the airways of cystic fibrosis (CF) patients, the effects of these vectors on the kinetics of airway epithelial cell growth have not been investigated. We tested whether E1, E3-deleted Ad vectors (Ad5-CMV-lacZ) affect the kinetics of cell proliferation of human airway epithelial cells in primary culture. There was a dose-dependent relationship between the vector multiplicity of infection (moi) and the efficiency of Ad-mediated lacZ gene transfer. Growth curves of cells exposed to vector were shifted to the right as compared to vehicle in a dose-dependent manner. The vector-induced slowing of cell proliferation resulted from both (i) increased apoptotic cell death and (ii) lower recruitment into S phase. UV inactivation of the vector genes abolished the effects on cell proliferation. These data demonstrate that as the moi of vectors is increased to achieve effective gene transfer, apoptosis and slowing of the cell cycle of infected cells increases concomitantly. The identification and inactivation of these vector effects on human airway cells may be important for reducing the toxicity of adenovirus vectors for gene therapy of CF airways.

Two cystic fibrosis transmembrane conductance regulator mutations have different effects on both pulmonary phenotype and regulation of outwardly rectified chloride currents

Cystic fibrosis (CF), a disorder of electrolyte transport manifest in the lungs, pancreas, sweat duct, and vas deferens, is caused by mutations in the CF transmembrane conductance regulator (CFTR). The CFTR protein has been shown to function as a cAMP-activated chloride channel and also regulates a separate protein, the outwardly rectifying chloride channel (ORCC). To determine the consequence of disease-producing mutations upon these functions, mutant CFTR was transiently expressed in Xenopus oocytes and in human airway epithelial cells lacking functional CFTR. Both G551D, a mutation that causes severe lung disease, and A455E, a mutation associated with mild lung disease, altered but did not abolish CFTR's function as a chloride channel in Xenopus oocytes. Airway epithelial cells transfected with CFTR bearing either A455E or G551D had levels of chloride conductance significantly greater than those of mock-transfected and lower than those of wild-type CFTR-transfected cells, as measured by chloride efflux. A combination of channel blockers and analysis of current-voltage relationships were used to dissect the contribution of CFTR and the ORCC to whole cell currents of transfected cells. While CFTR bearing either mutation could function as a chloride channel, only CFTR bearing A455E retained the function of regulating the ORCC. These results indicate that CF mutations can affect CFTR functions differently and suggest that severity of pulmonary disease may be more closely associated with the regulatory rather than chloride channel function of CFTR.

Persistence of replication-deficient adenovirus-mediated gene transfer in lungs of immune-deficient (nu/nu) mice

To evaluate the role of cell-mediated immunity during gene transfer to the respiratory epithelium, the time course of luciferase activity was assessed after intratracheal administration of Av1Luc1, an E1a-E3-deleted adenoviral (Ad5) vector expressing firefly luciferase, to FVB/N, BALB/c and BALB/c-nu/nu adult mice. Adenovirus-mediated luciferase activity was rapidly lost from the respiratory tract between 2 and 14 days after treatment of both FVB/N and BALB/c wild-type mice. In the wild-type mice, loss of luciferase activity was associated with an early inflammatory response consisting of infiltration with macrophages and polymorphonuclear leukocytes and a more prolonged response characterized by lymphocytic infiltration. In the immune-deficient nu/nu mice, luciferase activity was maintained at higher levels than in immune-competent mice after exposure to virus and was associated with a distinct pattern of inflammation, consisting primarily of macrophages and polymorphonuclear cells but lacking the lymphocytic infiltrates typical of the inflammation in wild-type mice. Adenoviral DNA was rapidly cleared from the lungs of both nu/nu and wild-type mice. Markedly increased expression of proliferating cell nuclear antigen (PCNA) was observed in bronchiolar and alveolar epithelial cells and in inflammatory cells after exposure to Av1LUc1. The proliferative response of the respiratory epithelium was more extensive and persistent in wild-type than in nu/nu mice. To assess further the impact of the immune system on adenovirus-mediated gene expression, cotton rats treated with cyclosporin A or dexamethasone were exposed to Av1Luc1. Both agents decreased lung inflammation and significantly increased lung luciferase activity. The loss of lung luciferase activity is dependent, in part, on the immune-mediated clearance of respiratory epithelial cells, which may limit the extent and duration of gene expression with recombinant adenoviral vectors.

Safety evaluation of Ad5CMV-p53 in vitro and in vivo

In preparation for a clinical trial of the recombinant p53 adenovirus Ad5CMV-p53 for the treatment of lung cancer, the potential adverse effects of Ad5CMV-p53 were assessed in vitro and in vivo. No infectious replication of Ad5CMV-p53 was detectable in HeLa cells infected with extracts from HeLa cells previously infected with Ad5CMV-p53. No Ad5CMV-p53 DNA replication was detected by 32Pi labeling in lung cancer cells infected with Ad5CMV-p53 at multiplicities of infection (moi) up to 1,000 pfu/cell (total of 5 x 10(9) pfu viruses). The infectivity and cytotoxicity of Ad5CMV-p53 were examined in vitro in normal human bronchial epithelial (NHBE) cells. At a moi of 50 pfu/cell, Ad5CMV-p53 infection and expression were detectable in 80% of the treated cells. The exogenous p53 protein was first detected by western blotting at 8 hr and peaked at 48 hr after infection. Growth of NHBE cells was not affected by Ad5CMV-p53 infection at a moi of 100 pfu/cell. The pathogenicity of Ad5CMV-p53 was assessed in BALB/c mice. The virus was given to four groups of mice by intratracheal injection at dosages from 10(7) to 10(10) pfu; a fifth group received phosphate-buffered saline alone. None of the viral injections proved to be lethal. Mild to moderate peribronchiolar and perivascular infiltration by mononuclear cells and lymphocytes, with patches of pneumonitis, was the most acute toxic effect detected by histologic analysis in the two high-dose groups. Immunohistochemical analysis of the same paraffin-embedded sections showed that infectivity and level of expression of p53 in lung tissue were dose-dependent. Our results demonstrate that Ad5CMV-p53 is a replication-defective virus that yields a relatively low degree of acute toxicity in mice; these data document a safety profile encouraging for clinical trials of Ad5CMV-p53 in the therapy of lung cancer.