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R G Crystal

Publications and source records attributed to R G Crystal.

At least 55 records · Page 3Linked to original sources
PubMed2000

Dendritic cells genetically modified to express CD40 ligand and pulsed with antigen can initiate antigen-specific humoral immunity independent of CD4+ T cells.

We have investigated whether dendritic cells genetically modified to express CD40 ligand and pulsed with antigen can trigger B cells to produce antigen-specific antibodies without CD4+ T-cell help. Dendritic cells modified with a recombinant adenovirus vector to express CD40 ligand and pulsed with heat-killed Pseudomonas induced naive B cells to produce antibodies against Pseudomonas in the absence of CD4+ T cells in vitro, initiated Pseudomonas-specific humoral immune responses in vivo in wild-type and CD4-/- mice, and protected immunized wild-type and CD4-/-, but not B-cell -/- mice, from lethal intrapulmonary challenge with Pseudomonas. Thus, genetic modification of dendritic cells with CD40 ligand enables them to present a complex mixture of microbial antigens and establish CD4+ T cell-independent, B cell-mediated protective immunity against a specific microbe.

Animals↗
PubMed2000

Persistent, antigen-specific, therapeutic antitumor immunity by dendritic cells genetically modified with an adenoviral vector to express a model tumor antigen.

Dendritic cells (DC) are potent antigen-presenting cells that play a critical role in the initiation of cellular immune responses. Using a BALB/c syngeneic colon carcinoma cell line expressing a model tumor antigen beta-galactosidase (betagal), we previously reported (Song et al, J Exp Med 1997; 186: 1247-1256) that immunization of mice with a single injection of DCs genetically modified with an adenovirus vector expressing betagal confers potent protection against a lethal intravenous tumor challenge, as well as suppression of pre-established lung tumors, resulting in a significant survival advantage. In the present study, we have addressed the question: how long does the memory of tumor antigen- specific immunity persists after DC priming in vivo using this genetically modified DC-based cancer vaccination strategy? To accomplish this, two groups of mice were evaluated: (1) mice surviving >400 days following protection from an initial intravenous tumor challenge after immunization with DC genetically modified to express betagal; and (2) mice surviving >300 days that had previously demonstrated regression of pre-established lung tumors after treatment with DC immunization. By analyzing the antigen-specific cytotoxic T lymphocyte response and challenging these long-term survival mice with a second subcutaneous tumor administration, the data demonstrate that a single administration of DC genetically modified to express a model antigen induces long-lasting, antigen-specific antitumor immunity in both naive and tumor-bearing hosts, observations that have important implications in the development of genetically modified DC-based antitumor vaccination strategies. Gene Therapy (2000) 7, 2080-2086.

Adenoviridae↗
PubMed2000

Feasibility of a clinical trial of augmentation therapy for alpha(1)-antitrypsin deficiency. The Alpha 1-Antitrypsin Deficiency Registry Study Group.

We examined the feasibility of a randomized clinical trial of intravenous augmentation therapy for individuals with alpha 1-antitrypsin (alpha1AT) deficiency, basing calculations on newly available data obtained from the NHLBI Registry of Patients with Severe Deficiency of Alpha 1-Antitrypsin. Using rate of FEV(1) decline as the primary outcome and adjusting for noncompliance, a study of subjects with Stage II chronic obstructive pulmonary disease (COPD) (initial FEV(1) 35 to 49% predicted) with biannual spirometry measures obtained over 4 yr of follow-up would require 147 subjects per treatment arm to detect a difference in FEV(1) decline of 23 ml/yr (i.e., a 28% reduction), the difference observed in the NHLBI Registry (1-sided test, alpha = 0.05, 90% power). To detect a 40% reduction in mortality in a 5-year study of subjects with baseline FEV(1) 35 to 49% predicted, recruited over the first 2 yr and then followed an additional 3 yr, 342 subjects per treatment arm would be needed. Though significant impediments to carrying out a clinical trial exist, including the cost of such a trial and the potential difficulties in recruiting patients for a placebo-controlled trial, we recommend a randomized controlled trial as the best method to evaluate the efficacy of intravenous augmentation therapy and of possible future treatments.

Adult↗
PubMed2000

Lung overexpression of the vascular endothelial growth factor gene induces pulmonary edema.

We hypothesized that the angiogenic mediator, vascular endothelial growth factor (VEGF), known to be expressed in the lung and to be capable of inducing local edema in skin, might evoke the development of lung edema if expressed in excess amounts. To test this hypothesis, we developed an in vivo model of VEGF overexpression in the lung on the basis of delivery to the respiratory epithelium of the VEGF165 complementary DNA by an E1(-) adenovirus vector (AdVEGF165). Administration of AdVEGF165 by the intratracheal route (10(9) plaque-forming units [pfu]) to C57Bl/6 mice showed increased expression of VEGF messenger RNA in lung tissue by Northern analysis. Overexpression of VEGF protein in the lung at Days 1 to 10 was confirmed by enzyme-linked immunosorbent assay. Intratracheal administration of AdVEGF165 resulted in a dose-dependent increase in lung wet/dry weight ratios over time, lung histology showed widespread intra- alveolar edema, and pulmonary capillary permeability was significantly increased as quantified by the Evans blue dye assay and [(131)I]albumin permeability. To confirm the specificity of these observations, mice were pretreated with intranasal administration of an adenovirus vector expressing a truncated soluble form of the VEGF receptor flt-1 (Adsflt). Adsflt (10(9) pfu) pretreatment completely abrogated the increased lung wet/dry weight ratio caused by AdVEGF165 administration, whereas an identical adenovirus vector with an irrelevant transgene had no effect upon subsequent AdVEGF165-induced pulmonary edema. Together, these data suggest that overexpression of VEGF in the lung may be one mechanism of increased pulmonary vascular permeability in the early stages of acute lung injury.

Administration, Inhalation↗
PubMed2000

Macrophage inflammatory protein 3alpha transgene attracts dendritic cells to established murine tumors and suppresses tumor growth.

Dendritic cells (DCs) are powerful antigen-presenting cells that function as the principal activators of T cells. Since the human CC chemokine, macrophage inflammatory protein 3alpha (MIP-3alpha), is chemotactic for DCs in vitro, we hypothesized that adenovirus-mediated gene transfer of MIP-3alpha (AdMIP-3alpha) to tumors might induce local accumulation of DCs and inhibit growth of preexisting tumors. AdMIP-3alpha directed expression of mRNA and protein in vitro, and the supernatant of A549 cells infected with AdMIP-3alpha was chemotactic for DCs. In vivo, injection of AdMIP-3alpha into subcutaneous tumors resulted in local expression of the MIP-3alpha cDNA and in the local accumulation of DCs. In four syngeneic tumor models, growth of established tumors was significantly inhibited compared with untreated tumors or tumors injected with control vector, and in all but the poorly immunogenic LLC carcinoma model, this treatment increased survival advantage of the preexisting tumors. In all four tumor models, intratumoral injection of AdMIP-3alpha induced the local accumulation of CD8b. 2(+) cells and elicited tumor-specific cytotoxic T-lymphocyte activity, and adoptive transfer of splenocytes of animals receiving this treatment protected against a subsequent challenge with the identical tumor cells. In wild-type but not in CD8-deficient mice, AdMIP-3alpha inhibited the growth of tumors. Finally, AdMIP-3alpha also inhibited the growth of distant tumors. This strategy may be useful for enlisting the help of DCs to boost anti-tumor immunity against local and metastatic tumors without the necessity of ex vivo isolation and manipulation of DCs.

Adenoviridae↗
PubMed2000

Antivector and antitransgene host responses in gene therapy.

Current viral gene therapy vectors effectively transfer genes in vivo at the price of eliciting innate and acquired host responses against the vector and/or transgene. Antigens present in the viral vector and the expression of the transgene both cause cellular and humoral immune responses dependent on the viral vector, the route of administration, and the genotype and infection history of the host. In general, adenoviral vectors cause strong immune responses, which result in only transient expression of the therapeutic gene. Adeno-associated virus and retrovirus vectors elicit weaker immune responses and can therefore result in long-term gene transfer and expression. Methods to avoid host responses, including modification of viral vector and immunosuppression of the host, can increase the longevity and efficiency of gene transfer.

Adjuvants, Immunologic↗
PubMed1999

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.

Adenoviridae↗
PubMed1999

Enhanced liver uptake of opsonized red blood cells after in vivo transfer of FcgammaRIIA cDNA to the liver.

Fcgamma receptors convey to phagocytic cells the ability to recognize, bind, and internalize IgG-coated cells and microorganisms. The present study demonstrates the use of adenovirus (Ad)-mediated gene transfer of human Fcgamma receptor IIA cDNA to convert normally nonphagocytic cells (hepatocytes) into functional equivalents of phagocytic cells. Ad vector in vitro transfer and expression of FcgammaRIIA cDNA in primary rat hepatocytes was confirmed by flow cytometry anti-FcgammaRIIA immunodetection, and the function of the receptor was demonstrated by enhanced binding and phagocytosis of (51)Cr-labeled IgG-opsonized erythrocytes. After in vivo gene transfer to rats, expression of FcgammaRIIA cDNA in hepatocytes was confirmed by Northern analysis and immunohistochemistry. Rats infected with the Ad vector carrying the FcgammaRIIA cDNA demonstrated enhanced clearance of opsonized erythrocytes, but not nonopsonized erythrocytes, from the circulation with increased sequestration within the liver. Together, these data demonstrate that Ad-mediated FcgammaRIIA gene transfer can convert normally IgG-nonphagocytic cells into phagocytic cells capable of recognizing, binding, and ingesting an opsonized particulate antigen, suggesting that gene transfer strategies might be used to transiently augment host defense by enhancing the clearance of immune complexes.

Animals↗
PubMed1999

Specific binding of the adenovirus capsid to the nuclear envelope.

Adenovirus (Ad) vectors used for gene therapy are efficient in entering the infected cell and targeting their genome to the nucleus. To study the mechanism of the interaction between Ad and the nuclear envelope we have established an in vitro assay using rat liver nuclei incubated with serotype 5 Ad vector. Binding of either fluorophore (Cy3)-labeled Ad5 (Cy3-AdGFP) or [3H]Ad5 was blocked by excess unlabeled Ad5, indicating that the interaction was specific. Binding reached equilibrium within 30 min, exhibited temperature dependence with more binding occurring at 37 degrees C than at 4 degrees C and appeared to be irreversible. Prior treatment of nuclei with glutaraldehyde or proteolysis of nuclei with trypsin inhibited the Cy3-AdGFP association with nuclei, and pretreatment of Cy3-AdGFP with human anti-Ad5 serum, but not naive human serum, inhibited Cy3-AdGFP, suggesting a requirement for direct interaction between Ad5 and nuclei. Addition of excess unlabeled Ad serotype 2 or Ad serotype 7 competed for binding with Cy3-AdGFP, indicating that the capsid determinant of nuclear binding was conserved among group B and C Ad serotypes. These data suggest that the Ad capsid and nuclear envelope contain specific domains that mediate binding of the two entities and that binding mechanisms to the nuclear envelope might be a common final pathway of different Ad serotypes.

Adenoviridae↗
PubMed1999

Angiogenesis gene therapy: phase I assessment of direct intramyocardial administration of an adenovirus vector expressing VEGF121 cDNA to individuals with clinically significant severe coronary artery disease.

BACKGROUND: Therapeutic angiogenesis, a new experimental strategy for the treatment of vascular insufficiency, uses the administration of mediators known to induce vascular development in embryogenesis to induce neovascularization of ischemic adult tissues. This report summarizes a phase I clinical experience with a gene-therapy strategy that used an E1(-)E3(-) adenovirus (Ad) gene-transfer vector expressing human vascular endothelial growth factor (VEGF) 121 cDNA (Ad(GV)VEGF121.10) to induce therapeutic angiogenesis in the myocardium of individuals with clinically significant coronary artery disease. METHODS AND RESULTS: Ad(GV)VEGF121.10 was administered to 21 individuals by direct myocardial injection into an area of reversible ischemia either as an adjunct to conventional coronary artery bypass grafting (group A, n=15) or as sole therapy via a minithoracotomy (group B, n=6). There was no evidence of systemic or cardiac-related adverse events related to vector administration. In both groups, coronary angiography and stress sestamibi scan assessment of wall motion 30 days after therapy suggested improvement in the area of vector administration. All patients reported improvement in angina class after therapy. In group B, in which gene transfer was the only therapy, treadmill exercise assessment suggested improvement in most individuals. CONCLUSIONS: The data are consistent with the concept that direct myocardial administration of Ad(GV)VEGF121.10 to individuals with clinically significant coronary artery disease appears to be well tolerated, and initiation of phase II evaluation of this therapy is warranted.

Adenoviridae↗
PubMed1999

Safety of direct myocardial administration of an adenovirus vector encoding vascular endothelial growth factor 121.

A gene therapy strategy involving direct myocardial administration of an adenovirus (Ad) vector encoding the vascular endothelial growth factor 121 cDNA (Ad(GV)VEGF121.10) has been shown to be capable of "biological revascularization" of ischemic myocardium in an established porcine model [Mack, C.A. (1998). J. Thorac. Cardiovasc. Surg. 115, 168-177]. The present study evaluates the local and systemic safety of this therapy in this porcine ischemia model and in normal mice. Myocardial ischemia was induced in Yorkshire swine with an ameroid constrictor 21 days prior to vector administration. Ad(GV)VEGF121.10 (10(9) or 10(10) PFU), Ad5 wild type (10(9) PFU), AdNull (control vector with no transgene; 10(9) PFU), saline, or no injection (naive) was administered in 10 sites in the ischemic, circumflex distribution of the myocardium. Toxicity was assessed by survival, serial echocardiography, blood analyses, and myocardial and liver histology at 3 and 28 days after vector administration. All pigs survived to sacrifice, except for one animal in the Ad(GV)VEGF121.10 (10(10) PFU) group, which died as a result of oversedation. Echocardiograms of Ad(GV)VEGF121.10-treated pigs demonstrated no differences in pericardial effusion, mitral valve regurgitation, or regional wall motion compared with control pigs. Intramyocardial administration of Ad(GV)VEGF121.10 included only minimal myocardial inflammation and necrosis, and no hepatic inflammation or necrosis. Only a mild elevation of the white blood cell count was encountered on day 3, which was transient and self-limited in the Ad(GV)VEGF121.10 group as compared with the saline-treated animals. As a measure of inadvertent intravascular administration of vector, normal C57/BL6 mice received intravenous Ad(GV)VEGF121.10 (10(4), 10(6), 5 x 10(7), or 10(9) PFU), AdNull (5 x 10(7) or 10(9) PFU), or saline. Toxicity was assessed by survival, blood analyses, and organ histology at 3 and 7 days after vector administration. A separate group of C57/BL6 mice received intravenous AdmVEGF164 (Ad vector encoding the murine VEGF164 cDNA), Ad(GV)VEGF121.10, AdNull (10(8) PFU each group), or saline to assess duration of expression and safety of a homologous transgene. All mice survived to sacrifice except for 40% of the mice in the highest (10(9) PFU; a dose more than 10(3)-fold higher by body weight than the efficacious dose in pigs) Ad(GV)VEGF121.10 dose group, which died on days 5-6 after vector administration. The only differences seen in the blood analyses between treated and control mice were in the very high Ad(GV)VEGF121.10 dose group (10(9) PFU), which demonstrated an anemia as well as an increase in alkaline phosphatase when compared with all other treatment groups. Hepatic VEGF levels by ELISA in AdmVEGF164-treated mice did not persist beyond 14 days after vector administration, suggesting that persistent expression of a homologous VEGF gene transferred with an Ad vector is not a significant safety risk. Although this is not a chronic toxicity study, these data demonstrate the safety of direct myocardial administration of Ad(GV)VEGF121.10, and support the potential use of this strategy to treat human myocardial ischemia.

Adenoviruses, Human↗
PubMed1999

Anti-tumor immunity induced by in vivo adenovirus vector-mediated expression of CD40 ligand in tumor cells.

CD40 ligand (CD40L), the ligand for CD40 on antigen-presenting cells, is essential for the initiation of antigen-specific T cell responses, an important component of the immune response to tumors. This study is based on the hypothesis that in vivo genetic modification of tumor cells to express CD40L will trigger CD40 on local antigen-presenting cells to present tumor antigen to the cellular immune systems, thus eliciting anti-tumor immunity to suppress growth of the tumor. To examine this concept, subcutaneous tumors of three different murine tumor models in two strains of mice were infected with a recombinant adenovirus (Ad) vector expressing murine CD40L (AdmCD40L). In the B16 (H-2b, melanoma) and CT26 (H-2d, colon cancer) murine models, injection of AdmCD40L into established subcutaneous tumors resulted in sustained tumor regression and tumor-free status in >60% of animals. Intratumoral injection of AdmCD40L also significantly suppressed the growth of established, weakly immunogenic Lewis lung carcinoma (H-2b) tumors, but to a lesser extent. Ex vivo AdmCD40L-transduced tumor cells implanted in syngeneic hosts induced significant antitumor response against preexisting identical tumors at a distant site. Both in vivo and in vitro AdmCD40L modification of tumors to express CD40L elicited tumor-specific cytolytic T lymphocytes responses, and the transfer of spleen cells from treated mice efficiently protected naive mice against a subsequent tumor challenge. These results support the concept that transduction of tumors with a recombinant CD40L adenovirus vector may be a useful strategy for cancer immunotherapy.

Adenoviruses, Human↗
PubMed1999

E1(-)E4(+) adenoviral gene transfer vectors function as a "pro-life" signal to promote survival of primary human endothelial cells.

Although endothelial cells are quiescent and long-lived in vivo, when they are removed from blood vessels and cultured in vitro they die within days to weeks. In studies of the interaction of E1(-)E4(+) replication-deficient adenovirus (Ad) vectors and human endothelium, the cells remained quiescent and were viable for prolonged periods. Evaluation of these cultures showed that E1(-)E4(+) Ad vectors provide an "antiapoptotic" signal that, in association with an increase in the ratio of Bcl2 to Bax levels, induces the endothelial cells to enter a state of "suspended animation," remaining viable for at least 30 days, even in the absence of serum and growth factors. Although the mechanisms initiating these events are unclear, the antiapoptoic signal requires the presence of E4 genes in the vector genome, suggesting that one or more E4 open reading frames of subgroup C Ad initiate a "pro-life" program that modifies cultured endothelial cells to survive for prolonged periods.

Adenoviridae↗
PubMed1999

Selective expansion of alveolar macrophages in vivo by adenovirus-mediated transfer of the murine granulocyte-macrophage colony-stimulating factor cDNA.

Based on the hypothesis that genetic modification of freshly isolated alveolar macrophages (AM) with the granulocyte-macrophage colony-stimulating factor (GM-CSF) cDNA would induce AM to proliferate, this study focuses on the ability of adenoviral (Ad) vectors to transfer and efficiently express the murine (m) GM-CSF cDNA in murine AM with consequent expansion in the number of AM in vitro and in vivo. To demonstrate that an Ad vector can effectively transfer and express genes in AM, murine AM recovered by bronchoalveolar lavage from the lung of Balb/c mice were infected with an Ad vector coding for green fluorescent protein (GFP) in vitro and expressed GFP in a dose-dependent fashion. Infection of AM with an Ad vector containing an expression cassette coding for mGM-CSF led to GM-CSF expression and to AM proliferation in vitro. When AM infected with AdGFP were returned to the respiratory tract of syngeneic recipient mice, GFP-expressing cells could still be recovered by bronchoalveolar lavage 2 weeks later. In vitro infection of AM with AdmGM-CSF and subsequent transplantation of the genetically modified AM to the lungs of syngeneic recipients led to GM-CSF expression in vivo. Strikingly, the AM recovered by lavage 5 weeks after transplantation demonstrated an increased rate of proliferation, and the total number of alveolar macrophages was 1. 9-fold greater than controls. Importantly, the increase in the numbers of AM was selective (ie, other inflammatory cell numbers were unchanged), and there was no modification to the lung architecture. Thus, it is feasible to genetically modify AM with Ad vectors and to use this strategy to modify the behavior of AM in vivo. Based on the importance of AM in the primary defense of the respiratory epithelial surface, this strategy may be useful in enhancing pulmonary defenses in immunodeficiency states.

Adenoviridae↗
PubMed1999

In vivo and ex vivo gene therapy strategies to treat tumors using adenovirus gene transfer vectors.

The adaptation of gene therapy strategies to treat tumors has broadened the potential armamentarium of anticancer strategies to include approaches for local control of tumor growth as well as to enhance systemic antitumor immunity to treat metastases. A major focus of the author and colleagues has been to use replication-deficient adenovirus vectors, both in vivo and ex vivo, to enhance local control of and systemic immunity against cancer. Several examples will be used to demonstrate these strategies. Using prodrugs, systemically administered drugs converted to toxic metabolites in the local tumor milieu, has proven to be a useful strategy for achieving high local concentrations of the toxic product while avoiding the systemic toxicity that limits the use of chemotherapy agents. Transfer of genes encoding cytosine deaminase (with 5-fluorocytosine) and carboxylesterase (CE) (with irinotecan) are two paradigms that have been used in our laboratory. The data demonstrate that using adenoviruses to deliver these genes to the tumor site leads to production of the active chemotherapeutic agent, which diffuses from the cell in which it was produced to suppress tumor growth and attain regional control in a single organ. Extensive experimental and clinical data now exist to support the concept that tumor growth is critically dependent on angiogenesis and that vascular endothelial growth factor (VEGF) appears to play a central role in the process of tumor neovascularization. Data generated in our laboratory have shown that adenovirus-mediated regional anti-VEGF therapy using a gene encoding a soluble form of flt-1 (one of the VEGF receptors) can be used for regional control of tumor growth. The critical dependence of many tumors on VEGF for neovascularization and dissemination predicts the general applicability of this strategy for treatment of many solid tumors. Another paradigm involves dendritic cells, potent antigen-presenting cells that play a critical role in the initiation of antitumor immune responses. Immunization of mice with dendritic cells genetically modified using an adenovirus vector transferring a gene encoding a tumor antigen confers potent protection against a lethal tumor challenge, as well as suppression of preestablished tumors, resulting in a significant survival advantage. One clinical scenario to which this approach is relevant is treating micrometastases present at the time of primary detection of many malignancies. A possible clinical strategy would be to modify dendritic cells from such patients using an adenovirus vector encoding the relevant tumor antigen, and then administering the genetically modified dendritic cells as adjuvant treatment following primary therapy.

Adenoviridae↗
PubMed1999

Exogenous control of cardiac gene therapy: evidence of regulated myocardial transgene expression after adenovirus and adeno-associated virus transfer of expression cassettes containing corticosteroid response element promoters.

OBJECTIVE: Because of the relative inaccessibility of the heart for repeated gene therapy, it would be useful to regulate the expression of transgenes delivered in a single dose of a gene therapy vector. Incorporation into the vector of a regulatable promoter that is responsive to pharmacologic agents that are widely used and well tolerated in clinical practice represents such a control strategy. METHODS: A replication-deficient adenovirus or an adeno-associated virus containing a chimeric promoter composed of 5 glucocorticoid response elements and the murine thrombopoietin complementary DNA (AdGRE.mTPO or AAVGRE.mTPO) was administered to the hearts of Sprague-Dawley rats. Platelet levels were evaluated as a reporter of transgene activity with or without dexamethasone. For comparison, rats received a control adenovirus vector, AdCMV.mTPO or AdCMV.Null, and the control adeno-associated virus vector AAVCMV.luc, which encodes for the firefly luciferase (luc) gene. RESULTS: Platelet elevation in the AdGRE.mTPO group peaked 4 days after dexamethasone administration, with a return to baseline 1 week after the initial corticosteroid dose. Subsequent dexamethasone administration at 2 and 4 weeks resulted in similar but progressively decreased responses. The AAVGRE.mTPO group had 5 peak platelet levels to a minimum of 2.2-fold with respect to baseline without diminution with subsequent dexamethasone administrations out to 169 days. In contrast, the AdCMV.Null and AAVCMV.luc groups demonstrated no increase in platelet counts and the AdCMV.mTPO group demonstrated a slow rise to a single peak platelet count independent of dexamethasone administration. CONCLUSION: It may be possible to control on demand the expression of a gene transferred to the heart. This strategy should be useful in cardiac gene therapy.

Animals↗