Liver-directed gene transfer in non-human primates

A novel strategy to modify adenovirus tropism and enhance transgene delivery to activated vascular endothelial cells in vitro and in vivo

To assess the possibilities of retargeting adenovirus to activated endothelial cells, we conjugated bifunctional polyethylene glycol (PEG) onto the adenoviral capsid to inhibit the interaction between viral knob and coxsackie-adenovirus receptor (CAR). Subsequently, we introduced an alphav integrin-specific RGD peptide or E-selectin-specific antibody to the other functional group of the PEG molecule for the retargeting of the adenovirus to activated endothelial cells. In vitro studies showed that this approach resulted in the elimination of transgene transfer into CAR-positive cells, while at the same time specific transgene transfer to activated endothelial cells was achieved. PEGylated, retargeted adenovirus showed longer persistence in the blood circulation with area under plasma concentration-time curve (AUC) values increasing 12-fold compared to unmodified virus. Anti-E-selectin antibody-PEG-adenovirus selectively homed to inflamed skin in mice with a delayed-type hypersensitivity (DTH) inflammation, resulting in local expression of the reporter transgene luciferase. This is the first study showing the benefits of PEGylation on adenovirus behavior upon systemic administration. The approach described here can form the basis for further development of adenoviral gene therapy vectors with improved pharmacokinetics and increased efficiency and specificity of therapeutic gene transfer into endothelial cells in disease.

Persistency of Adenoviral-Mediated Lysostaphin Expression in Goat Mammary Glands

Gene therapy has great potential to enable synthesis of protein molecules in targeted cells of an animal. One application may be the production of antibacterial enzymes by the mammary gland as a means of preventing or treating mastitis. We have previously demonstrated that goat mammary cells are capable of producing lysostaphin, an antistaphylococcal enzyme, after being transduced in vivo with a recombinant adenoviral vector containing a modified lysostaphin gene (Ad-lys). The current study examined duration of expression, and antibody response to lysostaphin and the adenoviral vector. Following intramammary infusion into nonlactating goats (n = 4), recovery of transducible adenoviral vector in mammary secretions persisted for 11 d. Transducible vector was not detected in serum, saliva, urine, or feces. Peak lysostaphin concentrations (< 20 microg/mL) in mammary secretions of infused udders were detected approximately 1 wk postinfusion, and generally returned to undetectable levels after an additional 1 to 2 wk. The poor persistency of expression was likely due to the very potent immune response to both the adenovirus and the expressed lysostaphin. Serum IgG antibodies recognizing the adenoviral vector developed within 7 d of the infusion, and titers rose dramatically to greater than 1:1 x 10(5). Similar titers of serum IgG antibodies to lysostaphin developed in 3 goats, with more moderate titers in the fourth goat. The antibody response to lysostaphin was delayed by approximately 4 d in comparison to the response to the adenovirus. Serum IgG antibody profiles were reflected in mammary secretions. No IgA antibodies to adenovirus or lysostaphin were detected in sera or mammary secretion. We demonstrate that while the lysostaphin gene can be introduced to the mammary gland using an adenoviral-mediated gene transfer technique, the strong immune response that it provokes makes the approach unsuitable for combating mastitis.

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.

Acute toxicity after high-dose systemic injection of helper-dependent adenoviral vectors into nonhuman primates

Systemic intravascular delivery of adenoviral (Ad) vectors for liver-directed gene therapy has been widely employed because of its simplicity, noninvasiveness, and potential for high transduction. For first-generation Ad vectors (FGAd), this results in high but transient levels of transgene expression and long-term hepatotoxicity due to viral gene expression from the vector backbone. Furthermore, high doses also result in an acute innate inflammatory response with potentially lethal consequences. Unlike FGAd, helper-dependent Ad vectors (HDAd) contain no viral genes and can provide sustained, high-level transgene expression with negligible long-term toxicity. However, whether the absence of viral gene expression leads to any decrease of acute toxicity in nonhuman primates has yet to be determined. To address this, we injected one baboon with 5.6 x 10(12) HDAd viral particles (VP)/kg and a second with 1.1 x 10(13) VP/kg. Approximately 50% hepatocyte transduction, accompanied by mild and transient acute toxicity, was observed in the animal receiving the lower dose. In the animal receiving the higher dose, 100% hepatocyte transduction, accompanied by lethal acute toxicity, was observed. These results indicate that systemic delivery of HDAd, like FGAd, results in acute toxicity in baboons consistent with activation of the innate inflammatory response, the severity of which is dose dependent, and confirm the hypothesis that Ad-mediated acute toxicity is independent of viral gene expression.

A new type of adenovirus vector that utilizes homologous recombination to achieve tumor-specific replication

We have developed a new class of adenovirus vectors that selectively replicate in tumor cells. The vector design is based on our recent observation that a variety of human tumor cell lines support DNA replication of adenovirus vectors with deletions of the E1A and E1B genes, whereas primary human cells or mouse liver cells in vivo do not. On the basis of this tumor-selective replication, we developed an adenovirus system that utilizes homologous recombination between inverted repeats to mediate precise rearrangements within the viral genome resulting in replication-dependent activation of transgene expression in tumors (Ad.IR vectors). Here, we used this system to achieve tumor-specific expression of adenoviral wild-type E1A in order to enhance viral DNA replication and spread within tumor metastases. In vitro DNA replication and cytotoxicity studies demonstrated that the mechanism of E1A-enhanced replication of Ad.IR-E1A vectors is efficiently and specifically activated in tumor cells, but not in nontransformed human cells. Systemic application of the Ad.IR-E1A vector into animals with liver metastases achieved transgene expression exclusively in tumors. The number of transgene-expressing tumor cells within metastases increased over time, indicating viral spread. Furthermore, the Ad.IR-E1A vector demonstrated antitumor efficacy in subcutaneous and metastatic models. These new Ad.IR-E1A vectors combine elements that allow for tumor-specific transgene expression, efficient viral replication, and spread in liver metastases after systemic vector application.

Construction and characterization of an intracellular single-chain human antibody to hepatitis C virus non-structural 3 protein

BACKGROUND/AIMS

We developed a single-chain antibody fragment (scFv) to the non-structural 3 protein (NS3) of hepatitis C virus (HCV) and tested its ability to interfere with the HCV replication cycle in infected hepatocytes.

METHODS

The variable regions of the human monoclonal antibody CM3.B6 that recognizes a conformational epitope within the helicase domain of NS3 were introduced into adenoviral vectors for expression in mammalian hepatocytes. Expression and binding properties of the scFv were analyzed by immunological assays. Effects of intracellular expression of the scFv on HCV replication were assessed in primary hepatocytes isolated from explanted livers of patients with chronic HCV infection by reverse transcription-polymerase chain reaction.

RESULTS

Transduction of HepG2 cells by the recombinant adenoviruses resulted in stable, efficient expression of scFv in the cytoplasm that was non-toxic to the cells. The scFv specifically bound to its cognate antigen. Significantly, intracellular expression of scFv resulted in a decrease in HCV genomic RNA in HCV infected hepatocytes.

CONCLUSIONS

These results indicate that specific binding of a scFv to NS3 may inhibit one or more functions of this essential viral protein thus interfering with the HCV replication cycle.

In vivo new bone formation by direct transfer of adenoviral-mediated bone morphogenetic protein-4 gene

Previous studies have demonstrated that bone morphogenetic protein-4 (BMP4) could participate in vivo endochondral ossification and is one of the main local contributing factors in the early stage of fracture healing. To investigate the effectiveness of BMP4 gene transfer, we constructed an adenoviral vector, Ad-BMP4, and evaluated its osteoinduction activity both in vitro and in vivo. In vitro study suggested that this vector could efficiently transduce mouse myoblast C2C12 cells and produce osteogenic BMP4 protein, as confirmed by immunofluorescence analysis and alkaline phosphatase activity assay. For in vivo study, Ad-BMP4 was directly injected into the hind limb muscles of male athymic nude rats. Visible new bone formation under X-ray films could be detected as early as three weeks post-injection. The bone tissue was further analyzed by histological staining and revealed a typical remodeled bone structure. In conclusion, this study is the first to establish the feasibility of adenovirus-based BMP4 gene therapy for bone regeneration.

In vivo transfection of the mouse vas deferens

To explore the possibility that specific characteristics of the epithelium of the male tract can be modified, transfections of the mouse vas deferens have been performed using in vivo injections of cationic DNA/liposome complexes. Gene transfer was done employing the reporter genes pEGFP-C1 encoding Green Fluorescent Protein (GFP) and pCMV-nls-beta encoding the nuclear beta-Galactosidase (beta-Gal). Foreign gene expression reached a maximum of 6.8% in the epithelial cells of the vas after treatment with the nuclear beta-Gal gene construction and of 13.3% after employing the GFP gene construction. Expression of the GFP gene appeared from one week up to three months following injection, and it appeared as patches of modified cells along the epithelium. Results from immunocytochemistry and Western Blotting support the conclusion that transfection of epithelial cells was achieved. We have also transfected the vas using gene constructions that express secretory proteins--specifically, the reporter system pSEAP-control that expresses a secretory form of human placental alkaline phosphatase, and the pGFP-Ctk-37 that expresses a secretion form of GFP. In both cases, the fluids expressed from the transfected vas showed a significant increase of alkaline phosphatase activity after pSEAP transfection and the presence of GFP protein when pGFP-Ctk-37 gene construction was employed. Our results indicate that the vas can be transfected in vivo using liposomes as vectors of foreign genes and that the vas fluid contents can be modified.

Gene transfer of a chimeric trans-activator is immunogenic and results in short-lived transgene expression

Pharmacologic gene regulation is a key technology, necessary to achieve safe, long-term gene transfer. The approaches described in the scientific literature all share in common the creation of artificial transcription factors by fusing a DNA-binding domain, a drug-binding domain and a transcription activation domain. These transcription factors activate the transgene expression upon binding of the pharmacologic agent (antibiotics of the tetracycline family, insect hormone, progesterone antagonist, or immunosuppressor drug) to the drug-binding domain. The major limitations to the use of these systems for human gene and cell therapies are the toxicity of the inducer molecule and the immunogenicity of the chimeric transcription factor. Thus, the gene regulation systems should operate with clinically approved drugs with safety records that do not conflict with the therapeutic gene expression regimen. This work focuses on the characterization of the immunogenicity of a tetracycline-activated transcription factor commonly used in preclinical gene therapy, rtTA2-M2, and its impact on reporter gene expression. We demonstrate that intramuscular injection of plasmid or adenoviral vectors encoding rtTA-M2 in outbred primates generates a cellular and humoral immune response to this transcription factor. The immune response to rtTA2-M2 blunts the duration of the expression the rtTA2-M2-controlled transgene in primates, presumably by destruction of the cells that coexpress rtTA2-M2 and the reporter or therapeutic gene. This immune response may result directly from the vectors used in this study, which prompts the development of new gene transfer vectors enabling safe and efficient pharmacologic gene regulation in clinic.

Preexisting immunity to adenovirus in rhesus monkeys fails to prevent vector-induced toxicity

In an earlier study we evaluated innate immune responses to a first-generation adenoviral vector infused into the portal vein of rhesus monkeys who had never been exposed to adenovirus previously. In these animals, the systemic administration of E1/E3-deleted adenoviral vectors resulted in immediate activation of innate immunity and serious toxicity caused by targeting of vector to antigen-presenting cells and systemic inflammation. We analyze here how these responses are affected by vector-specific preexisting immunity that was induced by intramuscular immunization 6 months prior to evaluation. Our results show that preexposure to the vector substantially diminishes the transgene expression in most tissues but has little effect on gene transfer. Significantly, preimmunization does not eliminate systemic vector-induced toxicity. These conclusions are based on the presence of clinical features of coagulopathy and elevated levels of proinflammatory cytokine interleukin-6 in the serum of animals treated with vector after intramuscular immunization. Furthermore, preexisting immunity appears to induce a vector-specific inhibitory effect on erythroid progenitor development in the bone marrow that is not found when naive animals are challenged with vector.

Induction of donor-specific tolerance by adenovirus-mediated CD40Ig gene therapy in rat liver transplantation

BACKGROUND

Blockade of CD40-CD40 ligand (CD154) costimulatory pathway with anti-CD154 antibody (Ab) prolongs allograft survival in experimental organ transplantations; however, repeated agent administration is needed to provide an adequate immunosuppression. Seeking for simple and effective approach to interfere this signaling, we applied adenovirus-mediated gene therapy by encoding CD40Ig gene (AdCD40Ig).

METHODS

Liver graft from ACI (RT1av1) rat was transplanted orthotopically into LEW (RT1l) rat, and AdCD40Ig was given to animals via the penile vein immediately after grafting (n=6).

RESULTS

A single treatment with AdCD40Ig at 1x10(9) plaque forming units induced specific expression of CD40Ig gene on allograft liver, produced substantial amount of the protein in the sera, and allowed indefinite graft survival. Whereas, LEW recipients given no treatment or control adenovirus vector (AdLacZ) promptly rejected ACI liver. In addition, AdCD40Ig-treated, long-term survivors accepted skin graft from the donor strain but not the third party graft. Histopathology revealed that liver structure of the long-term surviving animals was completely preserved in normal with no infiltration of mononuclear cells.

CONCLUSION

Blockade of CD40-CD154 pathway by CD40Ig gene therapy is a potent alloantigen-specific immunosuppressive strategy to induce permanent acceptance of liver allograft and would be a new therapeutic candidate in a clinical liver transplantation.

Adenovirus-mediated gene transfer to renal glomeruli in rodents

BACKGROUND

The expression of foreign genes into renal glomerular cells holds enormous potential to modulate the outcome of renal diseases. Recombinant adenoviruses (rAds) are promising gene transfer vectors because they have the ability to infect a wide range of nondividing cells. However, despite the fact that renal glomeruli are easily accessible via the renal circulation, adenovirus-mediated gene transfer into rodent glomeruli has been problematic. Here, we described our experience using rAd vectors to express foreign genes in rodent renal glomeruli in vivo and in cultured human renal glomerular cells.

METHODS

We developed two techniques--the "portal clamping" and "prolonged renal infusion"--to infect mouse and rat renal glomeruli in vivo, respectively. We used E-1-deleted rAd vectors carrying the lacZ gene encoding beta-galactosidase (Ad. CBlacZ) under the control of the cytomegalovirus enhancer and chicken beta-actin promoter. Cultured human renal glomerular podocytes, endothelial and mesangial cells were grown following standard techniques. Transgene expression was evaluated by doing beta-galactosidase staining and reverse transcription-polymerase chain reaction studies.

RESULTS

We found that both a prolonged exposure and a high concentration of circulating adenoviral vectors were required to achieve efficient gene transfer to renal glomerular cells in rodents. The virus-mediated transgene expression in renal glomeruli lasted for at least 42 days in mice and 21 days in rats without causing significant renal injury.

CONCLUSIONS

These data demonstrate the feasibility of using rAd vectors as a tool to express foreign genes in rodent renal glomerular cells and suggest that all types of human renal glomerular cells are equally susceptible to rAd infection.

Cirrhotic rat livers with extensive fibrosis can be safely transduced with clinical-grade adenoviral vectors. Evidence of cirrhosis reversion

Adenoviral vectors efficiently target normal liver cells; however, a clear-cut description of the safety boundaries for using adenovectors in hepatic cirrhosis has not been settled. With this in mind, we used a first-generation, replication-deficient adenoviral vector carrying the E. coli lacZ gene (Ad5betaGal) to monitor therapeutic range, biodistribution, toxicity and transduction efficiency in Wistar rats made cirrhotic by two different experimental approaches resembling alcoholic cirrhosis and biliary cirrhosis in humans. Further, we show proof of concept on fibrosis reversion by a 'therapeutic' Ad-vector (AdMMP8) carrying a gene coding for a collagen-degrading enzyme. Dose-response experiments with Ad5betaGal ranging from 1 x 10(8)-3 x 10(12) viral particles (vp) per rat (250 g), demonstrated that adenovirus-mediated gene transfer via iliac vein at 3 x 10(11 )vp/rat, resulted in an approximately 40% transduction in livers of rats made cirrhotic by chronic intoxication with carbon tetrachloride, compared with approximately 80% in control non-cirrhotic livers. In rats made cirrhotic by bile-duct obstruction only, 10% efficiency of transduction was observed. Biodistribution analyses showed that vector expression was detected primarily in liver and at a low level in spleen and kidney. Although there was an important increase in liver enzymes between the first 48 h after adenovirus injection in cirrhotic animals compared to non-transduced cirrhotic rats, this hepatic damage was resolved after 72-96 h. Then, the cDNA for neutrophil collagenase, also known as Matrix Metalloproteinase 8 (MMP8), was cloned in an Ad-vector and delivered to cirrhotic rat livers being able to reverse fibrosis in 44%. This study demonstrates the potential use of adenoviral vectors in safe transient gene therapy strategies for human liver cirrhosis.

Lethal toxicity, severe endothelial injury, and a threshold effect with high doses of an adenoviral vector in baboons

The effects of intravenous administration of a first-generation adenoviral vector expressing beta-galactosidase were compared in two baboons receiving a high dose or lower dose of vector, 1.2 x 10(13) or 1.2 x 10(12) particles/kg, respectively. The high-dose baboon developed acute symptoms, decreased platelet counts, and increased liver enzymes, and became moribund at 48 hr after injection, while the lower-dose baboon developed no symptoms. Expression of the beta-galactosidase transgene was prominent in liver, spleen, and endothelium of the arterial vasculature in the high-dose baboon, but was much more limited and spared the endothelium in the lower-dose baboon. Injury to the vascular endothelium was the most prominent abnormality in the high-dose baboon. Extensive histological studies provide a detailed picture of the pathology associated with a lethal dose of first-generation adenoviral vector in a primate.

In vivo gene delivery via portal vein and bile duct to individual lobes of the rat liver using a polylysine-based nonviral DNA vector in combination with chloroquine

The objective of this study was to evaluate a bifunctional synthetic peptide as a DNA vector for regional gene delivery to the rat liver by the portal vein and bile duct routes. The 31-amino-acid peptide (polylysine-molossin) comprises an amino-terminal chain of 16 lysines for electrostatic binding of DNA, and the 15 amino acid integrin-binding domain of the venom of the American pit viper, Crotalus molossus molossus. Initial in vitro evaluation demonstrated that polylysine-molossin/DNA complexes were much smaller (approximately 50-100nm versus 500-1300nm), more positively charged, and more stable in isotonic dextrose in comparisons with salt-containing solutions. However, polylysine-molossin/DNA complexes in any solution other than complete culture medium were ineffective for gene delivery in vitro. Vector localization studies demonstrated that both the portal vein and bile duct routes provided excellent access of polylysine-molossin/DNA complexes to the liver. However, complexes delivered by the portal vein were rapidly lost (<15 min) following re-establishment of the portal circulation, whereas complexes delivered by the bile duct persisted much longer. Polylysine-molossin/DNA complexes in various isotonic solutions were delivered to the right lateral lobes either by perfusion through a branch of the portal vein or by infusion into appropriate branches of the bile duct. Two or three hours before gene delivery, rats were given a single injection of chloroquine. We report that the polylysine-molossin vector is much more effective (>10-fold) when delivered by the bile duct route with all isotonic solutions evaluated, and that polylysine-molossin/DNA complexes in isotonic dextrose are much more effective (>10-fold) than complexes in salt-containing solutions.

Transplantation of hepatocytes in nonhuman primates: a preclinical model for the treatment of hepatic metabolic diseases

BACKGROUND

The transplantation of isolated hepatocytes in large animals, including nonhuman primates, must be evaluated before clinical trials are performed. However, in the absence of large transgenic animals and large-animal (as opposed to small-animal) models of genetic deficiencies, it is difficult to evaluate the fate of transplanted hepatocytes, their localization, survival, and function within the parenchyma of the host liver. In this work, we aimed to develop a technique for delivering hepatocytes to the liver of a nonhuman primate and to evaluate their localization and functionality in the short term.

METHODS

A 20% hepatectomy was performed in 34 cynomolgus monkeys (Macaca fascicularis) and hepatocytes were isolated. Hepatocytes were labeled in vitro with a recombinant retrovirus expressing the beta-galactosidase gene and returned to the liver by infusion through a portal catheter left in place. Liver biopsies were performed 4 and 7 d after transplantation.

RESULTS

Twenty-four monkeys underwent surgery to define the necessary technical adjustments and to optimize conditions. Six monkeys died. The whole protocol, including the transplantation of genetically marked hepatocytes and procurement of liver biopsies, was performed in the remaining 10 monkeys. In eight monkeys, transplanted hepatocytes expressing the beta-galactosidase gene were widely distributed in the portal tracts, sinusoids, and hepatocyte plates of the host liver 4 and 7 d after transplantation.

CONCLUSIONS

We have developed an experimental nonhuman primate model for the evaluation of hepatocyte transplantation. We demonstrated the engraftment and functioning of transplanted hepatocytes in the host liver 4 and 7 d after transplantation.

Human papilloma virus E6 and E7 proteins support DNA replication of adenoviruses deleted for the E1A and E1B genes

The action of transforming proteins from small DNA tumor viruses seems to be remarkably similar between different viruses, as they all use pRb and p53 pathways as cellular targets. This leads to deregulation of host cell cycling, which in turn creates an environment favorable for viral replication. Based on this, we hypothesized that regulatory proteins from human papillomaviruses (HPVs) can functionally trans-complement viral DNA replication of adenoviruses deleted for the E1A and E1B genes (AdE1-). To test this, we constructed AdE1- vectors expressing the human papilloma virus 16 (HPV-16) proteins E6 and E7. Expression of both E6 and E7 from these vectors partially complemented adenoviral DNA replication activity in vitro, in SK-Hep1 cells and primary human astrocytes, as well as in vivo in mouse liver. AdE1- vectors expressing E6 and E7 also increased hepatocellular DNA synthesis in vivo. Efficient AdE1- DNA replication was detected in HPV-associated cervical carcinoma cells but not in primary human cells. Linking the expression of regulatory oncoviral proteins to DNA replication of E1-mutant adenoviruses may provide a rationale for antitumor strategies.

Activation of Innate Immunity in Nonhuman Primates Following Intraportal Administration of Adenoviral Vectors

The innate immune response to intraportally infused adenoviral vector was evaluated in rhesus monkeys. A first-generation adenovirus-expressing lacZ (Ad-lacZ) was administered at a dose just below that which causes severe morbidity. The response to vector was evaluated for the initial 24 h following infusion. Clinical findings during this time were primarily limited to petechiae, consistent with the development of thrombocytopenia and biochemical evidence of disseminated intravascular coagulation. Serum transaminases were elevated and a lymphopenia developed. Tracking of fluorescent-labeled vector demonstrated distribution to macrophages and dendritic cells of the spleen and Kupffer cells of the liver. A systemic release of the cytokine IL-6 occurred soon after vector infusion. Analysis of splenic cells revealed acute activation of macrophages and dendritic cells followed by massive apoptosis. Bone marrow cultures demonstrated normal erythroid and primitive progenitors with a significant decrease in myeloid progenitors. Similar findings, except the abnormality in bone marrow cultures, were observed in monkeys who received an identical dose of Ad-lacZ in which vector genes were inactivated with psoralen and UV irradiation. These data suggest that inadvertent targeting of antigen-presenting cells following intraportal infusion of vector leads to a systemic cytokine syndrome which may be triggered by the viral capsid proteins.

Tumor-specific gene expression in hepatic metastases by a replication-activated adenovirus vector

Clinical applications of tumor gene therapy require tumor-specific delivery or expression of therapeutic genes in order to maximize the oncolytic index and minimize side effects. This study demonstrates activation of transgene expression exclusively in hepatic metastases after systemic application of a modified first-generation (E1A/E1B-deleted) adenovirus vector (AdE1-) in mouse tumor models. The discrimination between tumors and normal liver tissue is based on selective DNA replication of AdE1- vectors in tumor cells. This new AdE1- based vector system uses homologous recombination between inverted repeats to mediate precise rearrangements within the viral genome. As a result of these rearrangements, a promoter is brought into conjunction with a reporter gene creating a functional expression cassette. Genomic rearrangements are dependent upon viral DNA replication, which in turn occurs specifically in tumor cells. In a mouse tumor model with liver metastases derived from human tumor cells, a single systemic administration of replication activated AdE1- vectors achieved transgene expression in every metastasis, whereas no extra-tumoral transgene induction was observed. Here we provide a new concept for tumor-specific gene expression that is also applicable for other conditionally replicating adenovirus vectors.

Efficient gene transfer to rat renal glomeruli with recombinant adenoviral vectors

Recombinant adenoviruses are attractive vectors for renal gene transfer since they can efficiently transduce nondividing cells. However, despite the fact that renal glomeruli are easily accessible via the renal circulation, attempts to deliver foreign genes specifically into renal glomeruli, using adenoviral vectors, have had limited success in rodents. A simple intraarterial injection of adenoviral vectors into the renal circulation or incubation of the virus with the kidney for an extended period of time was found to be insufficient for this purpose. In this study, we have established an efficient gene transfer protocol to express foreign genes in rat renal glomerular cells, using adenoviral vectors. We demonstrated, for the first time, that rat glomerular endothelial cells could be efficiently transduced by slowly infusing a recombinant adenovirus (Ad.CBlacZ) into the right renal artery for a period of 15 min. High levels of lacZ expression were achieved in renal glomeruli without causing significant damage to renal glomeruli or other kidney structures. The virus-mediated expression lasted for at least 21 days. These data demonstrate the feasibility of using recombinant adenoviral vectors as a tool with which to study the effect of foreign gene expression on the structure and function of rat renal glomeruli in vivo.

Engraftment of autologous retrovirally transduced hepatocytes after intraportal transplantation into nonhuman primates: implication for ex vivo gene therapy

The main impediment to effective ex vivo liver gene therapy of metabolic diseases is the lack of experimental work on large animals to resolve such important issues as effective gene delivery, cell-processing techniques, and the development of appropriate vectors. We have used a nonhuman primate, as a preclinical model, to analyze the limiting steps of this approach using recombinant retroviruses. Seven monkeys (Macaca fascicularis) underwent the complete protocol: their left liver lobe was resected, a catheter was placed in the inferior mesenteric vein and connected to an infusion chamber, and the hepatocytes were isolated, cultured, and transduced with a retroviral vector containing the beta-galactosidase gene. The hepatocytes were harvested and returned to the host via the infusion chamber. Biopsies were taken 4-40 days later. No animal was killed in the course of the experiments. They all tolerated the procedure well. We have developed and defined conditions that permit the proliferation and transduction of up to 90% of the plated hepatocytes. A significant proportion of genetically modified cells, representing up to 3% of the liver mass, were safely delivered to the liver via the chamber. Polymerase chain reaction analysis detected integrated viral DNA sequences and quantitative analysis of the in situ beta-Gal-expressing hepatocytes indicated that a significant amount of transduced hepatocytes, up to 2%, had become integrated into the liver and were functional. These results represent substantial advances in the development of the ex vivo approach and suggest that this approach is of clinical relevance for liver-directed gene therapy.

Safe and efficient gene transfer into porcine hepatocytes using Sendai virus-cationic liposomes for bioartificial liver support

Establishment of a bioartificial liver support system using genetically modified hepatocytes is a potential approach to improve the treatment of severe liver failure. We describe the development of an efficient ex vivo method of gene transfer into a large number of porcine hepatocytes using hemagglutinating virus of Japan (HVJ)-liposome. The transfection efficiency of HVJ-liposome into isolated porcine hepatocytes attached to microcarrier beads was evaluated by beta-galactosidase (beta-gal) staining, fluorescence activated cell sorting analysis for beta-gal and luciferase assay, respectively. To examine the function and cellular damage of transduced hepatocytes, we used enzyme-linked immunosorbent assay for porcine albumin synthesis, lidocaine clearance test (P-450 activity), aspartate aminotransferase, and lactic dehydrogenase release assays. The optimal conditions for gene transfer into the beads-attached hepatocytes using HVJ-liposome included 4 microg of deoxyribonucleic acid with 200 microg of lipid/2 x 105 cells and exposure duration of 90 min. Under these conditions, beta-gal and luciferase genes were transduced to 2.5 x 108 isolated porcine hepatocytes following attachment to the beads. Positive beta-gal staining was observed in more than 30% of the beads-attached hepatocytes. The gene transfer activity of HVJ-liposome method determined by luciferase activities was about 100-fold of that of the lipofection method. Transfected porcine hepatocytes remained functional without any significant cell damage. Our results demonstrated that HVJ-liposome mediated gene transfer into microcarrier-attached porcine hepatocytes is an efficient and nontoxic method suitable for a bioartificial liver support sytem.

Comparison between intravenous and peritoneal route on liver targeted uptake and expression of plasmid delivered by Glyco-poly-L-lysine

AIM: To compare the effects of intravenous route and peritoneal route on liver targeted uptake and expression of plasmid delivered by galactose-terminal glyco-poly-L-lysine (G-PLL).

METHODS: The plasmid pTM/MMP-1 which could be expressed in eukaryotic cells was bound to G-PLL, and was then transferred into Wistar rats by intra venous and intraperitoneal injection. The expression and distribution of the plasmid were observed at different time periods by in situ hybridization and im munohistochemistry.

RESULTS: The plasmid could be expressed significantly within 24 h a fter being transferred in vivo by both intravenous and intraperitoneal routes. One week later the expression began to decrease, and could still be observed three weeks later. Although both the intravenous and intraperitoneal route could target-specifically deliver the plasmid to the liver, the effect of the former was better as compared to that of the latter.

CONCLUSION: Intravenous route is better for liver targeted uptake and expression of G-PLL-bound plasmids than the peritoneal route.

Adenovirus-mediated gene therapy to liver grafts: successful gene transfer by donor pretreatment

BACKGROUND

We have previously shown excellent adenoviral (Ad) gene transfection to transplanted liver grafts with the clamp technique (CT) where viral vector was delivered ex vivo and trapped in cold preserved liver grafts. In this study, we adopted a new gene therapy approach to achieve early transgene expression by donor pretreatment with viral vector and compared the efficacy of these two methods by using Ad vector encoding enhanced green fluorescent protein (AdEGFP) marker gene.

METHODS

AdEGFP (1 x 10(9)plaque forming units) was delivered to the liver grafts by: (1) single intravenous injection to donor Lewis rats 48 hours before harvesting, (2) ex vivo cold infusion into the harvested liver with CT, or (3) a combination of both methods. Liver grafts were stored in University of Wisconsin solution at 4 degrees C for 18 hours and then orthotopically transplanted into syngeneic recipients, and the expression of EGFP was studied.

RESULTS

With intravenous pretreatment of donor liver grafts, EGFP-expressing cells were detected as early as 3 hours after transplant, and moderate expression was seen by 12 hours. In contrast, EGFP was not detected until 12 to 24 hours after transplant with CT. High levels of EGFP-producing cells were seen with each technique at 7 days ( approximately 30% transfection efficiency). A combination of both methods did not enhance infectivity. Liver preservation injury was comparable between groups.

CONCLUSIONS

Gene transfer by donor pretreatment with AdEGFP induces early and efficient gene transduction to liver grafts compared with back-table delivery with CT. This method is simple and provides early transgene expression in liver grafts that potentially could be used to deliver genes to decrease preservation injury or rejection.

Manometric changes during retrograde biliary infusion in mice

The manometric, ultrastructural, radiographic, and physiological consequences of retrograde biliary infusion were determined in normostatic and cholestatic mice. Intraluminal biliary pressure changed as a function of infusion volume, rate, and viscosity. Higher rates of constant infusion resulted in higher peak intraluminal biliary pressures. The pattern of pressure changes observed was consistent with biliary ductular and/or canalicular filling followed by leakage at a threshold pressure. Retrograde infusion with significant elevations in pressure led to paracellular leakage of lanthanum chloride, radiopaque dye, and [(14)C]sucrose with rapid systemic redistribution via sinusoidal and subsequent hepatic venous drainage. Chronic extrahepatic bile duct obstruction resulted in significantly smaller peak intrabiliary pressures and lower levels of paracellular leakage. These findings indicate that under both normostatic and cholestatic conditions elevated intrabiliary volumes/pressures result in an acute pressure-dependent physical opening of tight junctions, permitting the movement of infusate from the intrabiliary space into the subepithelial tissue compartment. Control of intraluminal pressure may potentially permit the selective delivery of macromolecules >18-20 A in diameter to specific histological compartments.

Immunomodulation and adenoviral gene transfer to the lungs of nonhuman primates

Previous data from our laboratory and others have demonstrated a critical role for the CD4+ T lymphocyte in in vivo immune responses to recombinant adenoviral vectors. In rodent models, this subset of T cells is required for T cell proliferation, subsequent cytotoxic T cell generation, and production of anti-adenoviral antibodies by B cells. Both depleting and nondepleting anti-CD4 antibodies can attenuate these immune responses to recombinant adenovirus. On the basis of these data, we hypothesized that a nondepleting CDR-engrafted anti-human CD4 antibody (OKT4A) with cross-reactivity to rhesus macaques would attenuate both T and B cell responses to intrapulmonary administration of recombinant adenovirus and permit prolonged reporter gene expression and permit secondary gene transfer. Juvenile rhesus macaques were treated with PBS or OKT4A antibody (10 mg/kg) daily beginning 1 day prior to and up to 11 days after gene transfer. OKT4A resulted in significant attenuation of lymphocyte recruitment into the lung, lymphocyte-proliferative responses to both adenovirus capsid proteins and transgene protein, and adenovirus-induced interferon-gamma elaboration in whole blood and hilar lymph nodes. However, OKT4A was ineffective in attenuating adenovirus-induced IL-4 production in whole blood or hilar lymph nodes, generating neutralizing anti-adenoviral antibodies, or permitting secondary gene transfer. As all the monkeys in this protocol had baseline-detectable anti-adenoviral antibodies by ELISA that were nonneutralizing, analogous to most patients with cystic fibrosis, we postulate that anti-CD4 did not block the proliferation of memory B cells. Moreover, these data suggest that for transient immunomodulation to be successful, strategies need to focus specifically on B cell activation independent of CD4+ T cell help.

Osteoinduction by bone morphogenetic protein-2 via adenoviral vector under transient immunosuppression

To examine the effectiveness of gene transfer of bone morphogenetic protein (BMP)-2 in vivo, we evaluated osteoinduction by an adenoviral vector, AxCAOBMP-2, under transient immunosuppression with an immunosuppression drug (cyclophosphamide), which was given at a dose of 125 mg/kg intraperitoneally the day before vector injection. Twenty-five microliters of AxCAOBMP-2 (8.75 x 10(8) pfu, Group I) and AxCALacZ (1.75 x 10(8) pfu, control group) and 5 microliter of AxCAOBMP-2 (1.75 x 10(8) pfu, Group II) were injected into a right calf muscle. On day 21, induced bone in each group was investigated radiologically, histologically, and biochemically. The finding of osteoinduction was only seen in the AxCAOBMP-2-treated groups with immunosuppression. The activity of osteoinduction in Group I was higher than that in Group II. These results suggest that gene therapy with AxCAOBMP-2 under transient immunosuppression may be useful for bone reconstruction.

Adenoviral vector-mediated expression of physiologic levels of human factor VIII in nonhuman primates

An E1-, E2a-, E3-deleted adenoviral vector (Av3H82) encoding an epitope-tagged B domain-deleted human factor VIII cDNA (flagged FVIII) was evaluated in nonhuman primates. Twelve cynomolgus monkeys received intravenous administration of Av3H82; 6 monkeys received 6 x 10(11) particles/kg and another 6 received 3 x 10(12) particles/kg. Adenoviral vector transduction of the liver was efficient, reproducible, and linearly dose dependent. Physiologic levels of flagged FVIII were readily detected in plasma samples obtained from monkeys that received the higher dose of vector and human FVIII mRNA was detected in their livers. Expression of transgene mRNA was restricted to the liver by the albumin promoter. Although vector DNA was readily detected in the liver of monkeys that received the lower dose, neither human FVIII mRNA nor flagged FVIII protein could be detected. Vector distribution was widespread, with the highest levels observed in liver and spleen. Histopathology, hematology, and serum chemistry analysis identified the liver and blood as major sites of toxicity. Transient mild serum elevations of liver enzymes were observed, along with a dose-dependent inflammatory response in the liver. In addition, mild lymphoid hyperplasia was observed in the spleen. Mild anemia and a transient decrease in platelet count were observed, as was marrow hyperplasia and extramedullary hematopoiesis.

Clinical outcome of a protocol to produce immunosuppression in rhesus monkeys (Macaca mulatta): application to infectious disease and gene therapy studies

Induced immunosuppression is required for a number of studies using rhesus monkeys (Macaca mulatta). This report describes the clinical outcome and safety of a dose-finding experiment that determined doses of cyclophosphamide and prednisone that could be used to induce a state of immunosuppression in rhesus monkeys. After determining the optimum dose of immunosuppressive agents, the protocol was then used on animals participating in infectious disease and gene therapy studies. Splenectomy was performed in some animals to increase the severity of immunosuppression. The onset, duration, and severity of lymphopenia and leukopenia were consistent in all animals. In most animals, physical examination findings and clinical serum chemistry profiles demonstrated only transient abnormalities. With proper clinical monitoring, combination treatment with cyclophosphamide and prednisone is an effective and safe method for inducing immunosuppression in rhesus monkeys.

Cellular immune responses of healthy individuals to intradermal administration of an E1-E3- adenovirus gene transfer vector

In animals, Ad-mediated gene transfer initiates anti-Ad host immune responses that vary, depending on vector design, dose, host, and transgene. To begin to understand whether the anti-Ad vector responses in humans simulate those in animals, Ad(GV)CD.10, an E1-E3- Ad5 vector encoding the E. coli cytosine deaminase gene, was administered by the intradermal route to six normal individuals (8 x 10(7) to 8 x 10(9) particle units, each dose administered to two sites; n = 2 per group). No adverse events were observed. Polymerase chain reaction/Southern analysis demonstrated vector genome in the skin through 28 days in all individuals except one of two at the lowest dose. Local induration, independent of vector dose and baseline systemic anti-Ad5 neutralizing antibodies, developed in all subjects (6 to 17 mm, peak by day 3). Biopsies revealed a mild to moderate T cell (CD3+, CD4+, CD8+), B cell, and macrophage infiltrate at day 3, all decreased by day 28. Langerhans cells accumulated primarily in the papillary dermis. The day 3 cellular response was dose independent. On day 28, CD4+ and CD8+ T lymphocytes and macrophages showed dose dependency. There was minimal systemic Ad5-specific lymphocyte proliferation induced by Ad vector administration in three individuals studied, and no Ad5-specific cytotoxic T lymphocytes (evaluated in two subjects) could be detected. Thus, intradermal administration of an E1-E3- Ad vector to normal subjects induces mild/moderate local cellular responses, even in Ad-immunized individuals. These observations provide a baseline to determine if these human anti-Ad vector host responses can be circumvented by using "stealth" vectors and/or immunosuppression.

Gene transfer into the liver of nonhuman primates with E1-deleted recombinant adenoviral vectors: safety of readministration

Preclinical studies were designed to investigate the safety of recombinant adenoviruses infused into the portal vein of adult rhesus monkeys, as well as the safety and efficacy of readministration of these agents. The vectors used were recombinant adenoviruses, the E1 region of which was replaced with a marker gene expression cassette. Four 3- to 5-kg rhesus monkeys underwent portal vein cannulation, and infusion of escalating doses of recombinant first-generation vector. Serial sequential liver biopsies were performed, and necropsies were performed out to 14 months. X-Gal histochemical analysis of the liver showed evidence of dose-dependent increased gene transfer throughout the liver. Quantitative analysis of histopathology showed that portal inflammation was also present in transduced livers, and occurred in a dose-dependent manner. Severe toxicity, including mortality, was noted at the highest dose of vector. Readministration of a second vector was associated with the same degree of toxicity as the first vector, but prompted a much more vigorous neutralizing antibody response. The data suggest that intraportal administration and readministration of recombinant adenoviral E1-deleted vectors are feasible and safe. Vector administration at the highest dose (1 x 10(13) particles/kg) was associated with severe clinical and biochemical toxicity, and significant gene expression was associated with transaminitis. Readministration of vector is safe, but gene transfer is limited by the presence of neutralizing antibody.

In vivo endochondral bone formation using a bone morphogenetic protein 2 adenoviral vector

Bone morphogenetic proteins (BMPs) are polypeptides that induce ectopic bone formation in standard rat in vivo assay systems. Previous studies have demonstrated the clinical utility of these proteins in spinal fusion, fracture healing, and prosthetic joint stabilization. Gene therapy is also a theoretically attractive technique to express BMPs clinically, since long-term, regulatable gene expression and systemic delivery with tissue-specific expression may be possible in future. This study was performed to determine whether an adenoviral vector containing the BMP-2 gene can be used to express BMP-2 in vitro and promote endochondral bone formation in vivo. In vitro, U87 MG cells transduced per cell with 20 MOI of an adenoviral construct containing the BMP-2 gene under the control of the universal CMV promoter (Ad-BMP-2) showed positive antibody staining for the BMP-2 protein at posttransfection day 2. The synthesis and secretion of active BMP-2 into the conditioned medium of Ad-BMP-2-transduced 293 cells were confirmed by Western blot analysis and the induction of alkaline phosphatase activity in a W-20 stromal cell assay. In vivo, Sprague-Dawley rats and athymic nude rats were injected with Ad-BMP-2 in the thigh musculature and were sacrificed on day 3, 6, 9, 12, 16, 21, 60, and 110 for histological analysis. The Sprague-Dawley rats showed evidence of acute inflammation, without ectopic bone formation, at the injection sites. In the athymic nude rats, BMP-2 gene therapy induced mesenchymal stem cell chemotaxis and proliferation, with subsequent differentiation to chondrocytes. The chondrocytes secreted a cartilaginous matrix, which then mineralized and was replaced by mature bone. This study demonstrates that a BMP-2 adenoviral vector can be utilized to produce BMP-2 by striated muscle cells in athymic nude rats, leading to endochondral bone formation. However, in immunocompetent animals the endochondral response is attenuated, secondary to the massive immune response elicited by the first-generation adenoviral construct.

Intravenous administration of recombinant adenoviruses causes thrombocytopenia, anemia and erythroblastosis in rabbits

BACKGROUND

Recombinant adenoviruses are highly efficient gene transfer vehicles but their administration to mammals is accompanied by a strong inflammatory response. The present study reports additional side effects observed during adenoviral gene transfer studies in rabbits.

METHODS

Hematological and serological parameters, the course of viremia and the organ distribution were analyzed after in vivo administration of E1-deleted adenoviruses in rabbits.

RESULTS

The systemic administration of a therapeutic dose of 5 x 10(11) infectious particles/kg (infusion time 20 min) led to an average reduction of 80-90% in the platelet count within 48 h. Full recovery took 10-14 days. Virus administration induced a strong but transient erythroblastosis (peaking 24 h after administration) which settled 48 h later. Normochromic anemia occurred over the next 10 days with hemoglobin levels dropping by about 40% to reach the lowest level 10 days after administration and taking two months for full recovery. Dose-dependent thrombocytopenia was also found in mice, but neither erythroblastosis nor anemia was observed (in equivalent doses). The hematological findings did not improve after local injection via the portal vein. Local and systemic administration led to a comparable course of viremia. Only minor differences were found in the biodistribution of viruses between local and systemic administration. Large amounts of viral DNA and transgene expression were found in the lungs, the kidneys and the ovaries, even after local administration via the portal vein.

CONCLUSIONS

Local intravenous injection via the portal vein does not prevent systemic spread of viral vectors and the occurrence of vector-related side effects. The hematological changes observed in rabbits suggest the need for careful monitoring of hematological and rheological parameters in clinical trials.

Variability of human systemic humoral immune responses to adenovirus gene transfer vectors administered to different organs

Administration of adenovirus (Ad) vectors to immunologically naive experimental animals almost invariably results in the induction of systemic anti-Ad neutralizing antibodies. To determine if the human systemic humoral host responses to Ad vectors follow a similar pattern, we evaluated the systemic (serum) anti-Ad serotype 5 (Ad5) neutralizing antibodies in humans after administration of first generation (E1(-) E3(-)) Ad5-based gene transfer vectors to different hosts. AdGVCFTR.10 (carrying the normal human cystic fibrosis [CF] transmembrane regulator cDNA) was sprayed (8 x 10(7) to 2 x 10(10) particle units [PU]) repetitively (every 3 months or every 2 weeks) to the airway epithelium of 15 individuals with CF. AdGVCD.10 (carrying the Escherichia coli cytosine deaminase gene) was administered (8 x 10(8) to 8 x 10(9) PU; once a week, twice) directly to liver metastasis of five individuals with colon cancer and by the intradermal route (8 x 10(7) to 8 x 10(9) PU, single administration) to six healthy individuals. AdGVVEGF121.10 (carrying the human vascular endothelial growth factor 121 cDNA) was administered (4 x 10(8) to 4 x 10(9.5) PU, single administration) directly to the myocardium of 11 individuals with ischemic heart disease. Ad vector administration to the airways of individuals with CF evoked no or minimal serum neutralizing antibodies, even with repetitive administration. In contrast, intratumor administration of an Ad vector to individuals with metastatic colon cancer resulted in a robust antibody response, with anti-Ad neutralizing antibody titers of 10(2) to >10(4). Healthy individuals responded to single intradermal Ad vector variably, from induction of no neutralizing anti-Ad antibodies to titers of 5 x 10(3). Likewise, individuals with ischemic heart disease had a variable response to single intramyocardial vector administration, ranging from minimal neutralizing antibody levels to titers of 10(4). Evaluation of the data from all trials showed no correlation between the peak serum neutralizing anti-Ad response and the dose of Ad vector administered (P > 0.1, all comparisons). In contrast, there was a striking correlation between the peak anti-Ad5 neutralizing antibody levels evoked by vector administration and the level of preexisting anti-Ad5 antibodies (P = 0.0001). Thus, unlike the case for experimental animals, administration of Ad vectors to humans does not invariably evoke a systemic anti-Ad neutralizing antibody response. In humans, the extent of the response is dictated by preexisting antibody titers and modified by route of administration but is not dose dependent. Since the extent of anti-Ad neutralizing antibodies will likely modify the efficacy of administration of Ad vectors, these observations are of fundamental importance in designing human gene therapy trials and in interpreting the efficacy of Ad vector-mediated gene transfer.

Adenovirus-mediated gene expression in vivo is enhanced by the antiapoptotic bcl-2 gene

An adenovirus vector encoding the human Bcl-2 gene (hBcl-2) was derived. In vivo expression of hBcl-2 in murine livers enhanced and prolonged adenovirus-mediated gene expression. Furthermore, in the hBcl-2-treated group a significant reduction in the apoptosis induced by the adenovirus vector was observed. Thus, the cytoprotection of the vector-infected cells with antiapoptotic genes appears promising for successful in vivo gene therapy.

Regression of hepatocellular carcinoma in vitro and in vivo by radiosensitizing suicide gene therapy under the inducible and spatial control of radiation

To improve the efficacy and selectivity of gene therapy for hepatocellular carcinoma (HCC), we designed a strategy for suicide gene therapy in conjunction with radiation therapy using an HVJ-liposome vector system. The radio-inducible suicide gene was constructed by insertion of the early growth response gene 1 (Egr-1) promoter upstream of the HSV-tk gene (EGF-tk). First, to test the tumor specificity of Egr-1, RT-PCR and immunohistochemistry were performed. The Egr-1 gene was highly expressed in HCC compared with normal liver, where expression was barely detectable. Next, radiation-inducible activity of the Egr-1 promoter was examined in primary cultured normal hepatocytes and human hepatoma cell lines Huh7, HepG2, and PLC/PRF/5 by luciferase assay as a reporter gene system. Egr-1 promoter activity was markedly increased in hepatoma cell lines in a radiation dose-dependent manner, with maximum activation (15- to 28-fold) 12 hr after irradiation. In contrast, only a twofold increase in activation was noted in normal hepatocytes. An in vitro gene therapy experiment showed that EGR-tk-transduced hepatoma cells became highly sensitive to ganciclovir (GCV) after irradiation, but not without irradiation. GCV with or without irradiation did not show any cytotoxic effects against control gene-transfected cells. In addition, a "radiosensitization effect" was also demonstrated by combination therapy with the HSV-tk/GCV system and irradiation. To examine the efficacy of this EGR-tk/GCV gene therapy in vivo, xenografted liver tumors in nude mice were targeted using the HVJ-liposome vector system. EGR-tk-transfected tumors regressed significantly after a combination therapy of irradiation and GCV in all mice (n = 8), and almost disappeared in 3 weeks without any side effects. In comparison, tumors continued to grow in all mice (n = 8 in each group) treated by transfer of EGR-tk followed by either irradiation without GCV or GCV without irradiation. Our data indicate that HSV-tk gene therapy under the control of a radioinducible promoter is effective, and might be selective for hepatoma cells because of its inducible and radiosensitive capacity after radiation exposure as well as its tumor-specific activation.

Adenovirus-mediated transgene expression in nonhuman primate brain

Transgene expression in the brain of St. Kitts green monkey, Cercopithecus aethiops sabeus, was studied following injection of a serotype 5 adenoviral vector deleted in E1 and E3. The vector harbored the transgene for Escherichia coli beta-galactosidase (beta-Gal) with the simian virus 40 (SV40) nuclear localization signal under control of the Rous sarcoma viral (RSV) long terminal repeat. Several titers ranging from 5 x 10(7) to 2 x 10(9) plaque-forming units (PFU) in volumes ranging from 5 to 250 microl were injected into the caudate nuclei of 18 monkeys. Monkeys were treated with dexamethasone for 9 days, beginning the day prior to surgery, and were sacrificed at 1 week or at 1, 2, or 3 months. At 1 week, beta-Gal was expressed in thousands of cells, including both neurons and astrocytes. In addition, some dopaminergic neurons in the substantia nigra expressed transgene, suggesting retrograde transport of the vector. At 1 month 162,000+/-68,000 (SEM) or 65,000+/-29,000 beta-Gal-expressing cells persisted in striatum injected with 6 x 10(8) PFU in 30 microl or 5 x 10(7) PFU in 5 microl, respectively. Transgene expression was also observed in one of two monkeys sacrificed at 2 months and in a single monkey sacrificed at 3 months. No transgene expression was observed at 1 month in striatum injected with a higher titer (2 x 10(9) PFU in 100 microl) or more dilute vector (5 x 10(7) PFU in 30 microl). Staining for the major histocompatibility complex II (MHC II) subtype DR showed intense staining in sites injected with a higher vector titer, in which no transgene persisted at 1 month, whereas low to moderate staining was present in sites with high transgene expression. These observations suggest that there is an optimal range of vector titers for obtaining persistent transgene expression from E1E3-deleted adenovirus in primate brain, above which host responses limit transgene stability.

Macrophage inflammatory protein-2 gene therapy attenuates adenovirus- and acetaminophen-mediated hepatic injury

Profound hepatocellular injury is often a consequence of adenovirus-mediated gene therapy or acetaminophen ingestion. The aim of the present study was to examine the role of a CXC chemokine, macrophage inflammatory protein-2 (MIP-2), in the hepatotoxic response by mice infected with adenovirus and challenged with acetaminophen. CD1 mice that received a replication-defective human type 5 adenovirus vector (Ad70-3) intravenously exhibited hepatic injury that peaked at 24 h after infection. In contrast, mice that received a similar adenovirus vector containing a rodent MIP-2 cDNA insert had no hepatic injury at any time after infection. The combination of Ad70-3 infection and an intraperitoneal challenge with 400 mg/kg of acetaminophen was fatal in 50% of the mice, but only 10% of the AdMIP-2 group receiving acetaminophen were similarly affected. Furthermore, AdMIP-2 mice had significantly lower hepatic injury and serum aminotransaminases compared with the Ad70-3 group. However, AdMIP-2 infection in mice lacking the CXC chemokine receptor that binds MIP-2, CXCR2, did not attenuate any of the markers of liver injury after adenovirus and acetaminophen challenge. AdMIP-2 treatment of CD1 mice was also associated with significantly decreased leukocyte infiltration into the liver and an earlier increase in hepatic 3H-thymidine incorporation compared with the control group. Taken together, these data demonstrate that MIP-2 has a protective role in both adenovirus- and acetaminophen-mediated hepatotoxicity, and suggest that MIP-2 may promote rapid hepatic regeneration following acute hepatic injury.

Cellular immunity delimits adenoviral gene therapy strategies for the treatment of neoplastic diseases

BACKGROUND

Adenoviral gene therapy is a promising new approach for the treatment of neoplastic diseases. To design rational clinical trials and distinguish the effects of therapeutic transgene expression from those caused by viral infection alone, the immune response to the vector must be understood. In these experiments, we further define cellular immunity to recombinant adenovirus.

METHODS

The immune response to hepatic adenoviral gene transfer was studied in infected mice by depleting T cells with an anti-CD3 antibody, measuring splenocyte cytokine production, determining the impact of transgene expression on inflammation, and assessing liver MHC protein expression.

RESULTS

The cellular immune response to recombinant adenovirus is (1) averted by T lymphocyte depletion, (2) marked by a TH1 response with increased IL-2 production, (3) directed against both the transgene product and viral proteins, and (4) associated with increased hepatocyte MHC Class I expression.

CONCLUSIONS

It is necessary to take into consideration the constraints imposed by the immunogenicity of recombinant adenovirus and its transient transgene expression in the clinical application of adenoviral gene transfer for the treatment of cancer.

Adenovirus-mediated gene transfer to liver grafts: an improved method to maximize infectivity

BACKGROUND

Adenoviral gene therapy in liver transplantation has many potential applications, but current vector delivery methods to grafts lack efficiency and require high titers. In this study, we attempted to improve gene delivery efficacy using three different delivery methods to liver grafts with adenoviral vector encoding the LacZ marker gene (AdLacZ).

METHODS

AdLacZ was delivered to cold preserved rat liver grafts by: (1) continuous perfusion via the portal vein (portal perfusion), (2) continuous perfusion via both the portal vein and hepatic artery (dual perfusion), and (3) trapping viral perfusate in the liver vasculature by clamping outflow (clamp technique).

RESULTS

Using 1x10(9) plaque-forming units of Ad-LacZ (multiplicity of infection of 0.4), transduction rate in 3-hr preserved liver grafts, determined by 5-bromo-4-chromo-3-indolyl-beta-D-galactopyranoside staining and beta-galactosidase assay 48 hr after transplantation, was best with clamp technique (21.5+/-2.7% 5-bromo-4-chromo-3-indolyl-beta-D-galactopyranoside-positive cells and 81.1+/-3.6 U/g beta-galactosidase), followed by dual perfusion (18.5+/-1.8%, 66.6+/-19.4 U/g) and portal perfusion (8.8+/-2.5%, 19.7+/-15.4 U/g). Further studies using clamp technique demonstrated a near-maximal gene transfer rate of 30% at multiplicity of infection of 0.4 with prolonged cold ischemia to 18 hr. Transgene expression was stable for 2 weeks and slowly declined to 7.8+/-12.1% at day 28. Lack of inflammatory response was confirmed by histopathological examination and liver enzymes. Transduction was selectively induced in hepatocytes with nearly no extrahepatic transgene expression in the lung and spleen.

CONCLUSIONS

The clamp technique provides a highly efficient viral gene delivery method to cold preserved liver grafts. This method offers maximal infectivity of adenoviral vector with minimal technical manipulation.

T Cell- and NK Cell-Independent Inhibition of Hepatic Metastases by Systemic Administration of an IL-12-Expressing Recombinant Adenovirus

IL-12 is a potent immunoregulatory cytokine that has been shown to mediate tumor regression in a variety of tumor models. We describe the construction of AdCMV-IL-12, a recombinant adenovirus that encodes both subunits of IL-12 under transcriptional control of the CMV promoter. This recombinant virus efficiently infects a wide variety of cell types leading to the production of high levels of biologically active IL-12. Because the liver is a primary site of infection after i.v.-administered adenovirus, we tested the therapeutic efficacy of this virus in a murine hepatic metastasis tumor model. Systemic administration of AdCMV-IL-12 dramatically inhibited the formation of 3-day Renca hepatic metastases (mean of 16 metastases per liver) compared with the control virus AdCMV-βgal (mean of 209) or vehicle alone (mean of 272). Histologic analysis indicated that metastatic growth inhibition was accompanied by a dramatic perivascular infiltrate consisting of T cells, macrophages, and neutrophils. Therapeutic efficacy was not diminished in animals depleted of CD4+ or CD8+ T cells, or in SCID mice, even after NK cell ablation. In the latter case, a hepatic perivascular infiltrate composed of macrophages and neutrophils was observed after AdCMV-IL-12-treatment, while numerous activated Kupffer cells were noted in the hepatic parenchyma. Analysis of therapy-induced changes in hepatic gene expression demonstrated increased levels of IP-10 and Mig RNAs, but no increase in iNOS, Fas, or FasL RNA levels was observed. Our data suggest a model of metastatic growth inhibition mediated by nonlymphocyte effector cells including macrophages and neutrophils and that may involve anti-angiogenic chemokines.

Selective gene transfer into the liver of non-human primates with E1-deleted, E2A-defective, or E1-E4 deleted recombinant adenoviruses

Preclinical studies were designed to investigate the feasibility and safety of recombinant adenoviruses transduced into the hepatic artery of nonhuman primates. The vectors used are recombinant adenoviruses deleted in E1 and contain either a temperature-sensitive mutation in the E2a gene, which encodes a defective DNA-binding protein at nonpermissive temperatures, or a deletion of the E4 region, including open reading frame (ORF) 6. Six 8- to 10-kg baboons underwent femoral artery cannulation, and angiographic techniques were used to introduce vector selectively into either a portion of the right lobe of the liver via a branch of the right hepatic artery or the common hepatic artery. Necropsies were performed at 4, 29, or 61 days. Serial sequential liver biopsies were performed in the baboons that survived 29 or 61 days. In the 2 baboons with vector transduction into the right hepatic artery, X-Gal histochemical analysis of the liver showed evidence of quantitatively increased gene transfer in the targeted lobe; however, gene transfer was present throughout the liver. Quantitative analysis of histopathology showed that portal inflammation was present throughout both livers transduced with the highest dose of vector. No differences were seen in the level of portal inflammation in targeted and untargeted lobes despite the observed qualitative and quantitative differences in gene expression. Southern blot analysis of total cellular DNA isolated from targeted and nontargeted lobes showed similar levels of viral DNA throughout the liver. Polymerase chain reaction (PCR) analysis was able to detect viral DNA sequence in gonads and brain as well as many other tissues in baboons treated with high-dose vector. In baboons treated with lower doses of an E1-E4 deleted vector expressing the human ornithine transcarbamylase (OTC) gene, DNA was detectable by nested PCR in liver but not gonads at days 29 and 61. The data suggest that intraarterial administration of recombinant adenoviral E1-E4 deleted vector is feasible and safe. At high doses of vector, widespread dissemination of vector DNA is seen. At low doses, hepatic gene transfer is not associated with vector DNA dissemination to gonads.