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)

Antibody-dependent enhancement (ADE) of human immunodeficiency virus type 1 (HIV-1) infection in vitro has been described recently and was shown to occur by two mechanisms: either participation of the alternative pathway of complement or to involve an Fc receptor-mediated, complement-independent mechanism. Complement-mediated ADE results in an accelerated cytopathic effect in target cells that can abrogate the protective properties of neutralizing antibodies. This study characterizes the surface antigens of MT-2 cells using flow cytometric analysis and shows that these cells express high levels of both CD4 and complement receptor type 2 (CR2) while several CD4+ cell lines that do not demonstrate complement-mediated ADE lack high levels of complement receptors. Further, utilizing MT-2 cell cultures, it is demonstrated that complement-mediated ADE of HIV-1 infection is conferred by the sera from more than 80% of HIV-1 antibody-positive individuals (N = 85). Complement-mediated ADE of HIV-1 infection causes an acceleration of several parameters indicative of HIV-1 infection in vitro including increased HIV-1 antigen synthesis as detected by indirect immunofluorescence, RNA accumulation as measured by a solution hybridization protocol, reverse transcriptase release, and progeny virus production.
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PMID:Complement-mediated, antibody-dependent enhancement of HIV-1 infection in vitro is characterized by increased protein and RNA syntheses and infectious virus release. 246 4

Human immunodeficiency virus type 1 (HIV-1) infectivity and cytopathic effect require proper maturation of the viral envelope glycoprotein carbohydrate moieties. We have found that fresh human serum enhances the infectivity of HIV-1 in MT-2 cell infection assays when virus is synthesized in the presence of the mannosidase I inhibitor, 1-deoxymannojirimycin, or the mannosidase II inhibitor, swainsonine, but has no enhancing effect on virus synthesized in the presence of the glucosidase I inhibitors, castanospermine and 1-deoxynojirimycin, or the glucosidase II inhibitor, bromoconduritol. Enhanced infections were characterized by cytopathic effect, antigen synthesis and reverse transcriptase release, all which occurred sooner than in control-infected cultures. This enhancement of infection was also observed in C1q-deficient serum but was not observed in serum that was heat-inactivated or depleted of complement components C3 or factor B, thus suggesting a requirement for the alternate pathway of complement.
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PMID:Antibody-independent, complement-mediated enhancement of HIV-1 infection by mannosidase I and II inhibitors. 247 15

Mismatched double-stranded RNA of the form r(I)n.r(C12-U)n (Ampligen) has been shown to be active against human immunodeficiency virus type 1 (HIV-1) using CEM and C3 cells as targets for infection by the highly similar HIV-1 isolates HTLV-IIIB and LAV (Montefiori, D.C. and Mitchell, W.M., 1987, Proc. Natl. Acad. Sci. U.S.A., 84, 2985-2989). The scope of Ampligen's anti-HIV-1 activity was examined in this study using the genetically divergent HIV-1 isolate HTLV-IIIRF, two additional target T-cell lines, H9 and MT-2, and a monocyte/macrophage cell line, U937. As judged by indirect immunofluorescence, reverse transcriptase activity and vital dye uptake, Ampligen was active against HTLV-IIIRF in H9, MT-2, C3 and U937 cells in addition to being active against HTLV-IIIB in U937 cells. A minimum of 1 h preincubation of cells (MT-2) with Ampligen was required for maximum activity. These results suggest that Ampligen's potential clinical efficacy may not be limited by either the highly variable nature or host cell range of HIV-1.
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PMID:Mismatched dsRNA (ampligen) induces protection against genomic variants of the human immunodeficiency virus type 1 (HIV-1) in a multiplicity of target cells. 296 77

Modifying previously reported techniques, we attempted to increase the efficiency of human T cell leukemia-lymphoma virus (HTLV) transformation of human T lymphocytes. Lethally irradiated donor cells (DCs) were cultured with target mononuclear cells (TMCs). DCs included ten HTLV+ T cell lines with varying degrees of virus expression or seven cell lines that do not express HTLV. TMCs were prepared from 20 cord and 16 adult peripheral blood samples, including eight patients with acquired immunodeficiency syndrome (AIDS). TMCs were either added directly to the DCs or were first stimulated with phytohemagglutinin (PHA) (5 micrograms/mL) and grown in T cell growth factor (TCGF) prior to exposure to DCs. The presence of integrated HTLV proviral DNA in the transformed cells was determined by dot blot hybridization, utilizing a cloned probe to the HTLV-I genome. HTLV production by transformed TMCs was assessed for HTLV p19, reverse transcriptase, and virus particles. No transformation occurred with T cell donor lines that do not express HTLV. Low virus expressor DCs could only, with rare exception, transform preactivated TMCs. High-titer virus-producing DCs could transform activated and nonactivated cord blood cells and activated adult TMCs. Only MT-2 could routinely transform nonactivated normal adult and activated AIDS TMCs. HUT 102 B2 could transform only one activated AIDS sample, the cells of which initially expressed HTLV-like proteins and virions. Transformed cell lines contained subsets of mature T lymphocytes with variable HTLV expression. Prior activation and culture of the T lymphocytes increases the probability and rate of transformation by HTLV, allowing for biologic detection of low HTLV-producing cells and for in vitro expansion of T lymphocyte subsets from selected patients.
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PMID:Efficient transformation of previously activated and dividing T lymphocytes by human T cell leukemia-lymphoma virus. 633 58

We have tried to isolate a retrovirus from adult T-cell leukemia (ATL) which is a new clinical entity of T-cell malignancy. This disease shows a peculiar geographic clustering of patient birthplaces in the southwestern part of Japan. A retrovirus was isolated from the T-cell line, MT-2, which was established from cord lymphocytes cocultivated with leukemic cells from an ATL patient and characterized by: (a) density of 1.152-1.155 g/ml in sucrose gradient; (b) reverse transcriptase activity; (c) specific protein components; (d) RNA labeled with 3H-uridine, and (e) specific DNA complementary with viral RNA. The retrovirus was named adult T-cell leukemia virus (ATLV). Complementary DNA (cDNA) prepared by the endogenous reaction of detergent-treated virions hybridized with 35S RNA in MT-2 cells and another ATL cell line, MT-1, and this 35S RNA was inducible with IUDR treatment of the MT-1 cells, indicating that ATLV is a typical retrovirus containing 35S RNA as the genome. However, the cDNA did not show any detectable hybridization with cellular RNA of other human cell lines unrelated to ATL. The ATLV proviral DNA was detected in the chromosomal DNA of MT-1 and MT-2 cell lines as well well as in fresh peripheral blood cells of all five patients with ATL tested; however, it was not found in those of three healthy adults. Furthermore, sera from the patients reacted with one component of the ATLV protein, but normal sera did not. These sera and all other sera from ATL patients were previously shown to react with antigen(s) in leukemic cells of ATL, and the antigen(s) also reacted with sera from about 25% of the healthy adults in the endemic area, but not in the non-endemic area. These close associations of ATLV proviral DNA and proteins with ATL are direct evidence strongly suggesting the involvement of the retrovirus, ATLV, in the leukemogenesis of human ATL.
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PMID:A retrovirus from human leukemia cell lines: its isolation, characterization, and implication in human adult T-cell leukemia (ATL). 698 2

Foscarnet (phosphonoformic acid) is a pyrophosphate analog that inhibits the replication of human immunodeficiency virus type 1 (HIV-1) in vitro and in patients with AIDS. HIV-1 resistance to foscarnet has not been reported despite long-term foscarnet therapy of AIDS patients with cytomegalovirus disease. We therefore attempted to select foscarnet-resistant HIV-1 in vitro by serial endpoint passage of virus in 400 microM foscarnet. After 13 cycles of passage in MT-2 cells, virus exhibiting > or = 8.5-fold foscarnet resistance was isolated. The reverse transcriptase (RT) from resistant virions exhibited a similar level of foscarnet resistance in enzyme inhibition assays (approximately 10-fold resistance). Foscarnet-resistant virus showed increased susceptibility to 3'-azido-3'-deoxythymidine (90-fold) and to the HIV-1-specific RT inhibitors TIBO R82150 (30-fold) and nevirapine (20-fold). DNA sequence analysis of RT clones from resistant virus revealed the coexistence of two mutations in all clones: Gln-161 to Leu (CAA to CTA) and His-208 to Tyr (CAT to TAT). Sequence analysis of six clinical HIV-1 isolates showing reduced susceptibility to foscarnet revealed the Tyr-208 mutation in two, the Leu-161 mutation in one, and a Trp-88-to-Ser or -Gly mutation in four isolates. Site-specific mutagenesis and production of mutant recombinant viruses demonstrated that the Leu-161, Ser-88, and Tyr-208 mutations reduced HIV-1 susceptibility to foscarnet 10.5-, 4.3-, and 2.4-fold, respectively, in MT-2 cells. In the crystal structure of HIV-1 RT, the Gln-161 residue lies in the alpha E helix beneath the putative deoxynucleoside triphosphate (dNTP) binding site. The Gln-161-to-Leu mutation may affect the structure of the dNTP binding site and its affinity for foscarnet. The location of the Trp-88 residue in the Beta5a strand of HIV-1 RT suggest that the Ser-88 mutation affects template-primer binding, as do several mutations that affect RT susceptibility to nucleoside analogs.
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PMID:Novel mutations in reverse transcriptase of human immunodeficiency virus type 1 reduce susceptibility to foscarnet in laboratory and clinical isolates. 754 60

The dynamics leading to the emergence of a zidovudine-resistant mutation at codon 215 of the reverse transcriptase coding region was investigated in a cohort of HIV-infected individuals who received early zidovudine therapy. Clinical implications and the role of the resistance mutation at codon 41 were also assessed. Thirty-eight initially asymptomatic HIV-infected patients with a CD4+ cell count above 400 cells/mm3 were followed for a mean period of 121 weeks (20 received zidovudine and 18 matching placebo). Specific mutations in the HIV-1 reverse transcriptase coding region conferring resistance to zidovudine were detected using a selective polymerase chain reaction. During the follow-up period a mutation at codon 215 was detected in eight (40%) of the individuals in the zidovudine group, and in two of these eight subjects, a mutation at codon 41 was found. During the study, disease progression occurred in seven of the eight (88%) patients with a mutation at codon 215, compared with 7 of 18 (39%) patients assigned to the placebo group and 3 of the 12 (25%) patients receiving zidovudine treatment who did not develop a 215-mutant strain (p < 0.05). At entry, none of the patients harbored MT-2 tropic virus. Therefore, the emergence of a zidovudine-resistant mutation at codon 215 is associated with subsequent disease progression in asymptomatic HIV-infected patients who receive zidovudine monotherapy. This association suggests that the mutation at codon 215 is involved in a loss of therapeutic efficacy and, therefore, patients should be monitored during treatment with zidovudine.
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PMID:Emergence and clinical relevance of mutations associated with zidovudine resistance in asymptomatic HIV-1 infected patients. 758 24

The (-) enantiomers of 2',3'-dideoxy-5-fluoro-3'-thiacytidine [(-)-FTC] and 2',3'-dideoxy-3'-thiacytidine [(-)-BCH-189] were recently shown to inhibit selectively human immunodeficiency viruses (HIV) and hepatitis B virus in vitro. In the current study, the potential for HIV type 1 (HIV-1) resistance to these compounds was evaluated by serial passage of the virus in human peripheral blood mononuclear cells and MT-2 cells in the presence of increasing drug concentrations. Highly drug-resistant HIV-1 variants dominated the replicating virus population after two or more cycles of infection. The resistant variants were cross-resistant to (-)-FTC, (-)-BCH-189, and their (+) congeners but remained susceptible to 2',3'-dideoxycytidine, 3'-azido-3'-deoxythymidine, 3'-fluoro-3'-deoxythymidine, 2',3'-dideoxyinosine, phosphonoformate, the TIBO compound R82150, and the bis(heteroaryl)piperazine derivative U-87201E. Reverse transcriptase derived from drug-resistant viral particles was 15- to 50-fold less susceptible to the 5'-triphosphates of FTC and BCH-189 compared with enzyme from parental drug-susceptible virus. DNA sequence analysis of the reverse transcriptase gene amplified from resistant viruses consistently identified mutations at codon 184 from Met (ATG) to Val (GTG or GTA) or Ile (ATA). Sequence analysis of amplified reverse transcriptase from a patient who had received (-)-BCH-189 therapy for 4 months demonstrated a mixture of the Met-184-to-Val (GTG) mutation and the parental genotype, indicating that the Met-184 mutation can occur in vivo.
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PMID:Characterization of human immunodeficiency viruses resistant to oxathiolane-cytosine nucleosides. 768 16

Temperature elevation constitutes a beneficial component of the host defence against viral pathogens. However, heat treatment may be detrimental to HTLV-I-infected cells by increasing virion and oncoprotein production. We investigated the effects of thermal elevation on the in vitro replication of HTLV-I (human T-cell leukaemia/lymphoma virus type I) in MT-2 cells, an HTLV-I-transformed lymphoid cell line. We found that HTLV-I replication in MT-2 cells was markedly increased as demonstrated by a nearly 2-fold increase in detection of viral p24 antigen and a 20-fold increase in reverse transcriptase activity during up to 5 h of heat treatment at 42 degrees C. The results suggest that physiologic thermal elevations may induce viral production in HTLV-I-infected individuals.
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PMID:In vitro thermal enhancement of human T-cell leukaemia/lymphoma virus type I (HTLV-I) in HTLV-I-transformed cells. 768 46

We investigated permissiveness of the malignantly transformed trophoblast (choriocarcinoma) cell lines JAR, BeWo and JEG-3 to the human T cell lymphotropic virus type I (HTLV-I). After co-culture with the productively infected cell line MT-2 the choriocarcinoma cell lines were analysed for infection over a period of three months. The presence of HTLV-I viral DNA was examined by PCR using primers targeting the gag, pol, env and pX specific sequences. All amplified segments were found consistently in the cell cultures throughout the period of study. Further analysis that aimed to characterize the size variation of the integrated proviral DNA by Southern blotting revealed the presence of integrated proviral sequences which consisted, for the most part, of incomplete genomes. The presence of the full-length HTLV-I genome, however, was unequivocally confirmed in clonally expanded cell cultures derived from the originally infected parental cells. In order to analyse virus expression at the transcriptional level, we used reverse transcriptase (RT)-mediated PCR that was targeted at intra-exon regions (gag, pol, env and pX), and the splicing sites of the env and pX-tax/rex mRNAs. When compared with MT-2 cells, substantially lower levels of all transcripts were found in all the cell lines analysed. We were unsuccessful in attempts to detect viral protein expression using polyvalent or Tax- and Gag-specific monoclonal antibodies by Western blot analysis or immunoprecipitation, and we could not detect any RT activity released into the supernatant of the infected cells either. Collectively, these data suggest that the trophoblastic cells may become persistently but essentially non-productively infected with HTLV-I.
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PMID:Cell-mediated transmission of human T cell lymphotropic virus type I to human malignant trophoblastic cells results in long-term persistent infection. 784 28


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