Effect of a combination of clevudine and emtricitabine with adenovirus-mediated delivery of gamma interferon in the woodchuck model of hepatitis B virus infection. (33/171)

Our aim was to evaluate the antiviral effect of a combination of two nucleoside reverse transcriptase inhibitors, emtricitabine (FTC) and clevudine (L-FMAU), with the addition of an adenovirus-driven delivery of recombinant gamma interferon (IFN-gamma) in the woodchuck model of hepatitis B virus infection. Six woodchuck hepatitis virus (WHV)-infected woodchucks received L-FMAU (10 mg/kg) plus FTC (30 mg/kg) intraperitoneally for 8 weeks; six other animals received in addition an intravenous injection of a recombinant adenovirus vector expressing woodchuck IFN-gamma (Ad-IFN) at weeks 4 and 8. In the control group, two animals received Ad-IFN alone, two received adenovirus vector expressing the green fluorescent protein reporter gene, and one remained untreated. In less than 2 weeks, all woodchucks that received L-FMAU plus FTC showed a rapid and marked inhibition of viral replication, with a 4-log(10) drop in serum WHV DNA. In two animals, viremia remained suppressed for several months after the end of treatment. Similarly, a dramatic decrease in intrahepatic replicative intermediates of viral DNA was observed in the L-FMAU/FTC-treated groups. The additional administration of Ad-IFN led to increased inflammation in the liver but did not enhance the antiviral effect of the L-FMAU/FTC combination. In conclusion, therapies combining L-FMAU and FTC in WHV-infected woodchucks resulted in a potent and sustained antihepadnaviral effect both in the liver and in the blood circulation. However, no extra benefit of adding IFN-gamma gene transduction to the L-FMAU/FTC combination could be detected.  (+info)

Adenovirus-based gene therapy during clevudine treatment of woodchucks chronically infected with woodchuck hepatitis virus. (34/171)

Interferon-alpha (IFN-alpha) is a potent suppressor of hepatitis B virus (HBV) replication in the HBV-transgenic mouse, depleting virus replication intermediates from infected hepatocytes via pathways mediated by interferon-gamma (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha). It has also been hypothesized that cytokines induce curing of infected hepatocytes via non-cytolytic pathways during resolution of transient hepadnavirus infections. We have therefore evaluated therapy of chronic woodchuck hepatitis virus (WHV) infections using treatment with the nucleoside analog clevudine [L-FMAU; 1-(2-fluoro-5-methyl-b-L-arabinofuranosyl) uracil] and therapy with adenovirus vectors expressing INF-gamma, TNF-alpha, and beta-galactosidase. Before their use in vivo, expression of IFN-gamma and TNF-alpha from the adenovirus vectors was evaluated in vitro. Conditioned media from adenovirus-infected WC-3 cells was shown to inhibit WHV replication in baculovirus-transduced cells. Adenovirus super-infection of the liver in woodchucks led to declines in the percentage of hepatocytes with detectable core antigen and nucleic acids, and in levels of covalently closed circular DNA (cccDNA) and total WHV DNA, but a major long-term benefit of adenovirus super-infection during clevudine treatment was not demonstrated. Moreover, the effect took at least 2 weeks to develop suggesting that the declines in the percentage of WHV-infected cells, ccc, and total WHV DNA resulted from induction of the adaptive immune response by the adenovirus super-infection, and only indirectly from the expression of cytokines by the vectors.  (+info)

Molecular imaging of temporal dynamics and spatial heterogeneity of hypoxia-inducible factor-1 signal transduction activity in tumors in living mice. (35/171)

Tumor hypoxia is a spatially and temporally heterogeneous phenomenon, which results from several tumor and host tissue-specific processes. To study the dynamics and spatial heterogeneity of hypoxia-inducible factor-1 (HIF-1)-specific transcriptional activity in tumors, we used repetitive noninvasive positron emission tomography (PET) imaging of hypoxia-induced HIF-1 transcriptional activity in tumors in living mice. This approach uses a novel retroviral vector bearing a HIF-1-inducible "sensor" reporter gene (HSV1-tk/GFP fusion) and a constitutively expressed "beacon" reporter gene (DsRed2/XPRT). C6 glioma cells transduced with this multireporter system revealed dose-dependent patterns in temporal dynamics of HIF-1 transcriptional activity induced by either CoCl2 or decreased atmospheric oxygen concentration. Multicellular spheroids of C6 reporter cells developed a hypoxic core when >350 microm in diameter. 18F-2'-fluoro-2'deoxy-1beta-D-arabionofuranosyl-5-ethyl-uracil (FEAU) PET revealed spatial heterogeneity of HIF-1 transcriptional activity in reporter xenografts in mice as a function of size or ischemia-reperfusion injury. With increasing tumor diameter (>3 mm), a marked increase in HIF-1 transcriptional activity was observed in the core regions of tumors. Even a moderate ischemia-reperfusion injury in small C6 tumors caused a rapid induction of HIF-1 transcriptional activity, which persisted for a long time because of the inability of C6 tumors to rapidly compensate acute changes in tumor microcirculation.  (+info)

Distribution of 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl) uracil in mice bearing colorectal cancer xenografts: rationale for therapeutic use and as a positron emission tomography probe for thymidylate synthase. (36/171)

PURPOSE: In colorectal, breast, and head and neck cancers, response to 5-fluorouracil is associated with low expression of thymidylate synthase. In contrast, tumors with high expression of thymidylate synthase may be more sensitive to prodrugs such as 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl) uracil (FAU) that are activated by thymidylate synthase. These studies were designed to evaluate FAU as a potential therapeutic and diagnostic probe. EXPERIMENTAL DESIGN: [18F]-FAU and [3H]-FAU were synthesized with >97% radiochemical purity. [3H]-FAU or [18F]-FAU was administered intravenously to severe combined immunodeficient mice bearing either HT29 (low thymidylate synthase) or LS174T (high thymidylate synthase) human colon cancer xenografts. Four hours after [3H]-FAU dosing, tissue distribution of total radioactivity and incorporation of 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl) 5-methyluracil (FMAU), derived from thymidylate synthase activation of FAU, into tumor DNA was measured. Positron emission tomography (PET) images were obtained for 90 minutes after injection of [18F]-FAU. Thymidylate synthase activity was determined in vitro in tumors from untreated mice by [3H] release from [3H]dUMP. Each cell line was incubated in vitro with [3H]-FAU or [3H]-FMAU in the absence or presence of 5-fluoro-2'-deoxyuridine (FdUrd) and then was analyzed for incorporation of radiolabel into DNA. RESULTS: Thymidylate synthase enzymatic activity in LS174T xenografts was approximately 3.5-fold higher than in HT29 xenografts, and incorporation of radioactivity derived from [3H]-FAU into LS174T DNA was approximately 2-fold higher than into HT29 DNA. At 240 minutes, radioactivity derived from [3H]-FAU was approximately 2-fold higher in tumors than in skeletal muscle. At times up to 90 minutes, PET imaging detected only small differences in uptake of [18F]-FAU between the tumor types. Fluorine-18 in skeletal muscle was higher than in tumor for the first 90 minutes and plateaued earlier, whereas [18F] in tumor continued to increase during the 90-minute imaging period. For both cell lines in vitro, FdUrd decreased the rate of incorporation of [3H]-FAU into DNA, whereas the incorporation of [3H]-FMAU was increased. CONCLUSIONS: These results for FAU incorporation into DNA in vitro and in vivo further support clinical evaluation of FAU as a therapeutic agent in tumors with high concentrations of thymidylate synthase that are less likely to respond to 5-fluorouracil treatment. The high circulating concentrations of thymidine reported in mice may limit their utility in evaluating FAU as a PET probe.  (+info)

PET of cardiac transgene expression: comparison of 2 approaches based on herpesviral thymidine kinase reporter gene. (37/171)

PET of reporter gene expression holds promise for noninvasive monitoring of gene therapy. Previously, 2 approaches based on the herpes simplex virus type 1 thymidine kinase gene (HSV1-tk) have been successfully applied to the heart. Wild-type HSV1-tk was imaged with (124)I-labeled 2'-fluoro-2'-deoxy-5-iodo-1-beta-D-arabinofuranosyl-5-iodouracil (FIAU), and a mutant HSV1-tk (HSV1-sr39tk) was imaged with (18)F-labeled 9-[4-fluoro-3-(hydroxymethyl)butyl]guanine (FHBG). The aim of this study was to compare these 2 combinations with regard to specificity, imaging contrast, and reporter probe kinetics using dynamic PET in small and large animals. METHODS: Similar titers of adenovirus-expressing wild-type HSV1-tk (Ad(tk)), mutant HSV1-sr39tk (Ad(sr39tk)), or control genes were directly injected into the myocardium of 24 rats and 8 pigs. Two days later, dynamic PET was performed with a clinical scanner during the 120 min after injection of (124)I-FIAU (Ad(tk) animals and controls) or (18)F-FHBG (Ad(sr39tk) animals and controls). Imaging with (13)N-ammonia was performed to identify cardiac regions of interest. RESULTS: In rats, significant cardiac (124)I-FIAU accumulation occurred in images obtained early (10-30 min) after Ad(tk) injection. Because of tracer washout, however, no difference between Ad(tk)-injected animals and controls was seen in the images obtained later. For (18)F-FHBG, specific myocardial accumulation greater than background levels was detected in Ad(sr39tk)-injected animals at early imaging and, in contrast to (124)I-FIAU accumulation, increased over time until the latest imaging (105-120 min). At maximum, cardiac (18)F-FHBG concentration showed a 4.15 +/- 1.65-fold increase compared with controls (105-120 min), and cardiac (124)I-FIAU concentration reached a maximal increase of 1.34 +/- 0.38-fold compared with controls (10-30 min, P = 0.0014). Global cardiac reporter probe kinetics in rats were confirmed by regional myocardial analysis in pig hearts. Transgene expression was specifically visualized by both approaches. The highest target-to-background ratio of (124)I-FIAU in Ad(tk)-infected pig myocardium was 1.50 +/- 0.20, versus 2.64 +/- 0.49 for (18)F-FHBG in Ad(sr39tk)-infected areas (P = 0.01). In vivo results were confirmed by ex vivo counting and autoradiography. CONCLUSION: Both reporter gene/probe combinations were feasible for noninvasive imaging of cardiac transgene expression in different species. Specific probe kinetics suggest different myocardial handling of pyrimidine (FIAU) and acycloguanosine (FHBG) derivatives. The results favor (18)F-FHBG with mutant HSV1-sr39tk because of continuous accumulation over time and higher imaging contrast.  (+info)

Synthesis and evaluation of 2'-deoxy-2'-18F-fluoro-5-fluoro-1-beta-D-arabinofuranosyluracil as a potential PET imaging agent for suicide gene expression. (38/171)

2'-deoxy-2'-(18)F-fluoro-5-fluoro-1-beta-D-arabinofuranosyluracil ((18)F-FFAU) has been synthesized and evaluated in HT-29 cells as a potential PET agent for herpes simplex virus type 1 thymidine kinase (HSV1-tk) gene expression. METHODS: 2-Deoxy-2-(18)F-fluoro-1,3,5-tri-O-benzoyl-alpha-D-arabinofuranose was prepared by the reaction of the respective 2-triflate with tetrabutylammonium (18)F-fluoride. The fluorosugar was converted to its 1-bromo derivative and coupled with protected 5-fluorouracil. The crude product was hydrolyzed in base and purified by high-performance liquid chromatography to obtain the (18)F-FFAU. In vitro studies were performed in HT-29 cells by incubation at various time points. In vivo studies including biodistribution and microPET were performed in tumor-bearing nude mice. RESULTS: The radiochemical yield was 20%-30% decay corrected with an average of 25% in 4 runs. Radiochemical purity was >99% and average specific activity was 85 GBq/micromol (2,300 mCi/micromol) (end of synthesis). In vitro accumulation of (3)H-FFAU in HSV1-tk-expressing cells was approximately 180-fold (P < 0.001) higher than that in the wild-type cells between 30 and 120 min. In vivo uptake of (3)H-FFAU in HSV1-tk-positive tumors at 2 h was approximately 8-fold (P < 0.001) higher than that in the control tumors. Tumor uptake (percentage injected dose per gram of tissue) and the uptake ratio (tk-positive to wild type) of (3)H-FFAU in tk-positive cells was higher compared with those of our earlier studies using 2'-(14)C-deoxy-2'-fluoro-5-methyl-1-beta-D-arabinofuranosyluracil ((14)C-FMAU) and 9-(4-(18)F-fluoro-3-hydroxymethylbutyl)guanine ((18)F-FHBG) in the same cell lines. microPET on tumor-bearing nude mice also demonstrated a very high uptake of (18)F-FFAU in tk-positive tumors compared with that of the control tumor without significant accumulation in other organs. CONCLUSION: These results demonstrate that (18)F-FFAU has superior biodistribution characteristics and significantly higher in vivo uptake in HSV1-tk-expressing tumor compared with previously studied agents.  (+info)

Myocardial kinetics of reporter probe 124I-FIAU in isolated perfused rat hearts after in vivo adenoviral transfer of herpes simplex virus type 1 thymidine kinase reporter gene. (39/171)

Reporter gene imaging holds promise for noninvasive monitoring of cardiac gene therapy. We recently demonstrated that (124)I-labeled 2'-fluoro-2'-deoxy-5'-iodo-1beta-d-arabinofuranosyluracil ((124)I-FIAU) is suitable for PET of myocardial expression of herpes simplex virus type 1 thymidine kinase reporter gene (HSV1-tk). In contrast to previous studies in tumors, early specific uptake was followed by rapid washout. Myocardial kinetics of (124)I-FIAU are still poorly understood. This study aimed at a further investigation under controlled conditions using an isolated heart perfusion model. METHODS: Male Wistar rats underwent transthoracic regional injection of replication-defective adenovirus (2.5 x 10(9) plaque-forming units) containing either HSV1-tk (n = 16) or LacZ reporter gene (n = 15) into the inferior wall. Nonmanipulated rats (n = 5) served as further controls. Hearts were excised 2 d later and perfused according to the Langendorff technique with (124)I-FIAU-containing buffer (15 min, followed by 30 min of nonradioactive perfusion). Experiments were performed under baseline conditions and in the presence of thymidine (competitive substrate) or fludarabine (in vitro inhibitor of 5'-nucleotidase). Time-activity curves were acquired by external coincident detectors. The myocardial rate of (124)I-FIAU uptake (K(i)), clearance rate (K(o)), and volume of distribution (V(d) = K(i)/K(o)) were calculated. Subsequently, hearts were subjected to gamma-counting, followed by microtome slicing and autoradiography. RESULTS: The V(d) from Langendorff perfusion significantly correlated with final whole-heart tracer retention (r = 0.88, P = 0.019) and the autoradiographic area of regional myocardial activity (r = 0.89, P = 0.016). HSV1-tk hearts showed higher K(i) and V(d) of (124)I-FIAU compared with that of controls (P < 0.001) and detectable but slower washout compared with that of the LacZ group (P < 0.01). Addition of thymidine to the perfusate inhibited myocardial uptake of (124)I-FIAU by reducing V(d) and K(i) in HSV1-tk and LacZ hearts compared with the baseline. Addition of fludarabine did not result in the expected reduction of washout in HSV1-tk hearts due to inhibition of 5'-nucleotidases (which may dephosphorylate (124)I-FIAU monophosphate). It acted as an uptake inhibitor similar to thymidine, reducing V(d) in HSV1-tk hearts. CONCLUSION: Assessment of specific reporter probe kinetics after regional in vivo reporter gene transfer is feasible using the isolated perfused rat heart preparation. This model allows one to study the effects of pharmacologic interventions and may refine understanding of the reporter probe signal for in vivo imaging. Different nucleoside analogs significantly inhibit (124)I-FIAU uptake, emphasizing the importance of transporter mechanisms for reporter probe kinetics.  (+info)

Imaging bacterial infections with radiolabeled 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-iodouracil. (40/171)

Bacterial infections provide diagnostic dilemmas that could be enlightened by modern imaging technologies. We have developed a simple method for imaging bacterial infections in mice that relies on the phosphorylation and trapping of the thymidine kinase (TK) substrate 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-[125I] iodouracil ([125I]FIAU) within bacteria. FIAU was found to inhibit the growth of WT Escherichia coli but not a TK- strain, indicating that WT E. coli could metabolize this compound. In silico analyses demonstrated that all pathogenic strains of bacteria whose genomes have been sequenced contain a TK gene highly homologous to the E. coli TK. Accordingly, we demonstrated that localized infections caused by representatives of five genera of bacteria could be readily imaged with [125I]FIAU. Such imaging provides a general method for the diagnosis of localized bacterial infections that could be translatable to the clinic.  (+info)