Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Somatostatin (SS) and growth hormone-releasing hormone (GHRH) are synthesized and secreted by the hypothalamus, which can control the synthesis and secretion of the growth hormone (GH) from the hypophysis as well as regulate the GH concentrations in animals and humans. In this article, we describe the regulation of animal growth using plasmid DNA encoding both the GHRH gene and the SS gene fused with the hepatitis B surface antigen (HBsAg) gene. We constructed a series of expression plasmids to express the GHRH and HBsAg-SS fusion genes individually as well as collectively. The fusion gene and GHRH were successfully expressed in Chinese hamster ovary (CHO) cells, as proven by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunoblotting tests. Poly D, L-lactide-co-glycolic acid (PLGA) plasmid-encapsulating microspheres were prepared and injected intramuscularly into the leg skeletal muscles of rabbits. Weight gain/day and the levels of insulinlike growth factor-I (IGF-I), SS, and hepatitis B surface antibody (HBsAb) were monitored. During days 30 postinjection, increase in weight gain/day and IGF- I concentration and decrease in SS were observed in treatment groups. From days 15 to 30 postinjection, the weight gain/day significantly increased (P < 0.05) by 129.13%, 106.8%, and 72.82% relative to the control group in the co-expression GHRH and fusion gene (named P-G-HS), fusion gene (named P-HS), and GHRH (named P-G) groups, respectively. And most importantly, the P-G-HS group showed significant weight gain/day (P < 0.05) relative to the P-G and P-HS groups. A significant increase in the IGF-I concentration and decrease in the SS level relative to the control group were also observed. The results indicated that the combination of plasmid-mediated GHRH supplementation and positive immunization against SS led to more robust weight gain/day in rabbits.
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PMID:Simultaneous expression of growth hormone releasing hormone (GHRH) and hepatitis B surface antigen/somatostatin (HBsAg/SS) fusion genes in a construct in the skeletal muscle enhances rabbit weight gain. 1843 1

The objective of this study was to pursue the techniques involving the screening of the human antibody Fab fragment against hepatitis B virus surface antigen (HBsAg) and the construction of its disulfide-stabilized Fv fragment (dsFv). The phage antibody Fab fragments against HBsAg were screened from the human combinatorial immunoglobulin library. Sequence analysis revealed that its heavy chain gene was complete, but the light chain gene was lost. To improve the affinity of the antibody by chain shuffling, a human antibody light chain gene repertoire was generated by reverse transcriptase-polymerase chain reaction (RT-PCR) from the human peripheral blood lymphocytes. A phage antibody sub-library was then constructed by inserting the light chain gene repertoire into the phagmid that contained the Fd gene. Five clones with appreciably higher absorbance than that of the original clones were obtained, which indicated that the affinity of the light chain-shuffled phage antibodies was improved. Then, the mutated genes of dsFv against HBsAg were constructed by using PCR-based point mutagenesis method. Purified V(H) and V(L) proteins were folded into a 25-kDa protein, designated as anti-HBsAg dsFv. ELISA and competition ELISA revealed that the dsFv maintained the specificity of the Fab by binding to HBsAg, even through with a lower binding activity. These results have facilitated the undertaking of further functional analyses of the constructed dsFv, and may therefore provide an improved technique for the production and application of dsFvs against HBsAg.
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PMID:Screening of human antibody Fab fragment against HBsAg and the construction of its dsFv form. 1846 17

Even with the most advanced 3rd-generation assays, the serologic window period of hepatitis C virus (HCV) is approximately 74 days. HCV RNA detection would reduce the risk of transmission during this period. Furthermore, quantitation of HCV RNA is necessary for proper planning of treatment, monitoring disease progression, and assessing response to antiviral therapy. We have standardized an in-house HCV real-time reverse transcriptase polymerase chain reaction (RT-PCR) for screening and accurate quantitation and detection of HCV RNA in plasma samples. The in-house real-time assay was compared with a commercial assay using 100 chronically infected individuals and 70 blood donors who are negative for hepatitis B surface antigen, HCV antibody, and HIV antibody. The lower limit of detection of this in-house HCV real-time RT-PCR as assessed against the World Health Organization (WHO) standard was 50 IU/mL. Interassay and intraassay coefficient of variation ranged from 1.3% to 6.4% and 0.0% to 2.3% respectively. Virus loads as estimated with this in-house HCV real-time assay correlated with the commercial artus HCV RG RT-PCR assay (r = 0.59, P < 0.0001). This assay could be used in screening and monitoring individuals on therapy, showing no genotype-dependent differences in detection.
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PMID:Quantitation of hepatitis C virus using an in-house real-time reverse transcriptase polymerase chain reaction in plasma samples. 1848 3

We studied hepatic transaminases among rural Ugandans initiating highly active antiretroviral therapy (HAART) and assessed the impact of positive serology for hepatitis B surface antigen (HBsAg) and coadministration of therapy for tuberculosis. From July 2003 to December 2004, persons with symptomatic HIV disease or a CD4 count less than 250 cells/mm(3) and who had alanine transferase (ALT) or aspartate transferase (AST) less than 5 times the upper limit of normal were started on HAART including nevirapine (96%) or efavirenz (4%). Repository sera from a subset of 596 participants were analyzed for hepatic transaminase levels. A transaminase elevation was present before therapy for 249 (42%) of 596, at 3 months for 140 (25%) of 553, 12 months for 59 (11%) of 520, and 24 months for 67 (13%) of 508. In multivariate analyses, a transaminase elevation at 3 months was associated with male gender (odds ratio [OR], 1.55; 95% confidence interval [CI], 1.02-2.35), body mass index less than 18 kg/m(2) (OR, 2.10; 95% CI, 1.34-3.30), transaminase elevation at baseline (OR, 1.97; 95% CI, 1.30-2.99), and treatment for tuberculosis (OR, 4.68; 95% CI, 2.28-9.59). HBsAg status was not associated with transaminase elevations at baseline or while on HAART. The prevalence of hepatic transaminase elevations decreased during non-nucleoside reverse transcriptase inhibitor (NNRTI)-based antiretroviral therapy in this cohort of HIV-infected persons in rural Uganda.
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PMID:Liver enzymes improve over twenty-four months of first-line non-nucleoside reverse transcriptase inhibitor-based therapy in rural Uganda. 1877 41

GB virus C (GBV-C) infection is frequent in patients infected with the human immunodeficiency virus (HIV) due to similar transmission routes of these viruses. The aim of this study was to determine the rate of infection and genotypic characteristics of GBV-C in this population. The presence of GBV-C RNA was determined in serum samples of 106 patients infected with HIV by reverse transcriptase-nested polymerase chain reaction. GBV-C genotypes were determined by direct sequencing. Hepatitis B surface antigen (HBsAg), hepatitis B surface antibody (anti-HBs), hepatitis C antibody (anti-HCV), alanine aminotransferase (ALT) levels, HIV viral load and CD4(+) count were also tested in all patients. The overall prevalence of GBV-C infection was 11.3% in HIV patients. There was no significant difference between patients with and without GBV-C infection regarding age, sex, route of transmission, viral load, ALT levels, HBV and HCV co-infection and treatment with antiretroviral drugs. 66.7% of patients with GBV-C had a CD4(+) count > or = 200 and 33.3% had a CD4(+) count < 200 cells/mm(3). Phylogenetic analysis revealed that all GBV-C isolates were genotype 2, and classified as subtype 2a. GBV-C infection is relatively common in patients infected with HIV. The prevailing GBV-C genotype 2a in this study group concurred with reports from other parts of the Middle East.
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PMID:Frequency and genotype of GB virus C among Iranian patients infected with HIV. 1881 33

The hepatitis B virus (HBV) belongs to the hepadnavirus family. The genome of the virus, formed by a small DNA molecule with 3,200 base pairs, has 4 strongly overlapping protein coding regions: ORF preS/S, corresponding to the envelope proteins that constitute the HBV surface antigen (HBsAg); ORF preC/C, which encodes the viral capsid component (core antigen or HBcAg) and a non-structural protein that, after postranslation modification, is secreted and constitutes the "e" antigen (HBeAg); ORF P, which encodes the viral polymerase (polyprotein with DNA polymerase activity, reverse transcriptase and RNAase), and ORF X, which encodes a protein that acts as a multifunctional regulator for both the viral and cell cycles. HBV has a mutation rate of 1.4-3.2 x 105 substitutions/nucleotide/year. As a result of this variability, the virus circulates as a complex mixture of genetic variants, constituting a semi-species, that evolves throughout the infection depending on the evolutionary pressure of factors such as the immune response and antiviral treatments. Based on this variability, HBV has been classified into 8 genotypes (A-H) defined by a difference of more than 8% in the sequences of the complete viral genome. This variability is also responsible for HBV resistance to antiviral treatments with nucleotide and nucleoside analogs. Diagnosis of HBV infection includes determination of virological markers: viral antigens (HBsAg, HBeAg), specific antibodies (anti-HBc, anti-HBe, anti-HBs) and study of HBV-DNA for its detection and quantification and determination of genotypes and viral variants.
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PMID:[Molecular virology of the hepatitis B virus]. 1910 Feb 26

In rodents, p38 MAP kinase inhibitors (p38is) induce bone marrow hypocellularity and reduce reticulocyte and erythrocyte counts. To identify target cell populations affected, a differentiating primary liquid erythroid culture system using sca-1(+)cells from mouse bone marrow was developed and challenged with p38is SB-203580, SB-226882, and SB-267030. Drug-related alterations in genes involved at different stages of erythropoiesis, cell-surface antigen expression (CSAE), burst-forming unit erythroid (BFU-E) colony formation, and cellular morphology (CM), growth (CG), and viability were evaluated. CSAE, CM, and decreases in BFU-E formation indicated delayed maturation, while CG and viability were unaffected. Terminal differentiation was delayed until day 14 versus day 7 in controls. CSAE demonstrated higher percentages of sca-1(+)cells after day 2 and reduced percentages of ter119(+) cells after day 7 in all treated cultures. Real-time reverse transcriptase polymerase chain reaction revealed a transient delay in expression of genes involved at early, intermediate, and late stages of erythropoiesis, followed by rebound expression at later time points. Results demonstrate p38is do not irreversibly inhibit erythrogenesis but induce a potency-dependent, transient delay in erythropoietic activity. The delay in activity is suggestive of effects on sca-1(+)bone marrow cells caused by alterations in expression of genes related to erythroid commitment and differentiation resulting in delayed maturation.
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PMID:Effects of p38 MAP kinase inhibitors on the differentiation and maturation of erythroid progenitors. 1912 91

Hepatitis B virus (HBV) vaccine and diagnostic escape mutants are a growing concern. The principle target of detection, hepatitis B surface antigen (HBsAg), encoded by S, is completely overlapped by the reverse transcriptase encoding P. With the increased incidence of nucleos(t)ide analogue resistance altering P, the concurrent impact on S must be assessed. HBV DNA from 59 HBsAg-positive plasma samples was sequenced across the polymerase/surface region and the amino acid sequence of HBsAg was inferred. ELISAs were formatted containing individually bound monoclonal antibodies directed against three discrete epitopes on HBsAg. Similar point mutations occurring in different genotypes were shown to influence epitope conformation differently, indicating that the genetic backbone is a major factor in predicting phenotype. C-terminal changes associated with antiviral resistance were found to modulate epitope profiles of HBsAg. Treatment options which may promote drug resistance should be avoided to both protect antiviral treatment and prevent facilitation of vaccine and diagnostic escape mutants.
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PMID:The genetic backbone modulates the phenotype of hepatitis B surface antigen mutants. 1975 42

Niger is a west African country that is highly endemic for hepatitis B virus (HBV) infection. The seroprevalence for HBV surface antigen (HBsAg) is about 20%; however, there are no reports on the molecular epidemiology of HBV strains spreading in Niger. In the present study, HBV isolates from the sera of 58 consecutive, asymptomatic, HBsAg-positive blood donors were characterized. Genotype affiliation was determined by amplification, sequencing and phylogenetic analysis of the preS1, polymerase/reverse transcriptase (RT/Pol) and precore (preC)/C regions. The first series of results revealed that different genomic fragments clustered with different genotypes on phylogenetic trees, suggesting recombination events. Twenty-four complete genomic sequences were obtained by amplification and sequencing of seven overlapping regions covering the whole genome, and were studied by extensive phylogenetic analysis. Among them, 20 (83.3%) were classified unequivocally as genotype E (HBV/E). The remaining four (16.7%) clustered on a distinct branch within HBV/D with strong bootstrap and posterior probability values. Complete molecular characterization of these four strains was achieved by the Simplot program, bootscanning analysis and cloning experiments, and enabled us to identify an HBV/D-E recombinant that formed a new HBV/D subgenotype spreading in Niger, tentatively named D8. Moreover, 20 new complete HBV/E nucleotide sequences were determined that exhibited higher genetic variability than is generally described in Africa. One was found to be a recombinant containing HBV/D sequences in the preS2 and RT/Pol regions. Taken together, these data suggest that, in Niger, genetic variability of HBV strains is still evolving, probably reflecting ancient endemic HBV infection.
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PMID:A novel hepatitis B virus (HBV) subgenotype D (D8) strain, resulting from recombination between genotypes D and E, is circulating in Niger along with HBV/E strains. 2014 17

Although an estimated 1 million persons in the United States are chronically infected with hepatitis B virus, the prevalence of hepatitis B has declined since the implementation of a national vaccination program. Hepatitis B virus is transmitted in blood and secretions. Acute infection may cause nonspecific symptoms, such as fatigue, poor appetite, nausea, vomiting, abdominal pain, low-grade fever, jaundice, and dark urine; and clinical signs, such as hepatomegaly and splenomegaly. Fewer than 5 percent of adults acutely infected with hepatitis B virus progress to chronic infection. The diagnosis of hepatitis B virus infection requires the evaluation of the patient's blood for hepatitis B surface antigen, hepatitis B surface antibody, and hepatitis B core antibody. The goals of treatment for chronic hepatitis B virus infection are to reduce inflammation of the liver and to prevent complications by suppressing viral replication. Treatment options include pegylated interferon alfa-2a administered subcutaneously or oral antiviral agents (nucleotide reverse transcriptase inhibitors). Persons with chronic hepatitis B virus infection should be monitored for disease activity with liver enzyme tests and hepatitis B virus DNA levels; considered for liver biopsy; and entered into a surveillance program for hepatocellular carcinoma.
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PMID:Hepatitis B: diagnosis and treatment. 2038 72


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