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)

The role of drugs inhibiting viral replication in patients infected with HIV has been confirmed. Until now only dideoxynucleosides, which are reverse transcriptase inhibitors, have demonstrated antiviral activity in humans. A number of compounds acting on other steps of the viral cycle are currently being evaluated and clinical trials are being performed. Some investigators are attempting to inhibit the binding of viral particles to target cells and their penetration into these by acting on the interaction between HIV ant the CD4 molecule. Another approach consists in the characterization of enzymatic activities which are specific of HIV, other than reverse transcriptase, such as ribonuclease H, integrase or protease, in order to prepare specific inhibitors. Attempts are made to inhibit retroviral gene expression and production of viral particles in infected cells. The development of new nucleoside analogues and drugs with mechanisms of action and toxicities different from those of zidovudine should allow in the near future combination chemotherapy of HIV infection.
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PMID:[Chemotherapy for human immunodeficiency virus infection. Current status and perspectives]. 134 31

To study the interaction between the primate lentiviruses simian immunodeficiency virus (SIV) and human immunodeficiency virus (HIV) and the CD4 receptor we have cloned and sequenced the CD4 molecule from six non-human primate species: African green monkeys (three subspecies: sabeus, pytherethrus, aethiops), sooty mangabeys, patas monkeys, chimpanzees, rhesus macaques, and pig-tail macaques. Molecular cDNA clones representing CD4 mRNA were generated from total RNA from peripheral blood mononuclear cells (PBMC) by polymerase chain reaction (PCR) amplification including reverse transcriptase in initial reactions followed by two rounds of nested amplifications. Primer sequences were selected from regions conserved among human and rodent CD4 genes. Alignments of deduced amino acid sequences revealed interesting findings. First, all of the primate CD4 molecules were about 90% identical to the human CD4 sequence except the chimpanzee (98%). Second, two macaques or two African green monkey subspecies were as distanly related as the human versus chimpanzee sequences. Third, relatedness of CD4 sequences could not be predicted on the basis of geographic origin (Asian vs. African). Finally, upon sequencing several clones from individual monkeys, a low degree of sequence variation (nucleotide substitutions, deletions, and insertions) was found within the same animal, and in case of sooty mangabeys two distict populations of CD4 molecules were present within three of four individuals. The distinguishing features involved eight amino acid changes, including a single lysine deletion relative to a primate consensus sequence in the first complementary-determing region of V1J1. These two CD4 populations were present also at the genomic DNA level and may arrive from the two chromosomal alleles, suggesting the existence of distinct sooty mangabey subspecies. Overall, the V1J1 and to a lesser extent V2J2 were the most variable regions among the sequences examined. By construction and expression in mammalian cell lines of CD4 chimeras in which these regions of the human CD4 were replaced by those of the African green monkey and pig-tail macaques, a higher molecular mass of the CD4 chimeras were obtained in sodium dodecyl sulfate-polyacrylamide gel electrophoresis suggesting that the additional N-linked glycosylation sites present in these monkey CD4 are also used.
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PMID:Cloning and sequences of primate CD4 molecules: diversity of the cellular receptor for simian immunodeficiency virus/human immunodeficiency virus. 142 21

Recent findings have indicated that megakaryocytes may be susceptible to human immunodeficiency virus (HIV) infection, suggesting a potential role for megakaryocytes as viral reservoirs in HIV-infected patients. We report that the megakaryocytic cell line Dami could be productively infected with the HTLV III-B strain of HIV-1, in 26 different experiments (results of 16 experiments are reported); productive infection lasted up to 30 weeks. Despite a lack of detectable surface expression of the CD4 molecule and very low levels of CD4 mRNA, between 40% and 60% of megakaryocytic cells produced viral proteins after contact with HIV-1. Neither cytopathogenic effects nor syncytial formation was observed. Production of high levels of functional viral particles was indicated by analysis of p24 protein levels, reverse transcriptase activity, ultrastructural studies, and the capacity of supernatants from infected Dami cells to infect the Molt-4 T-lymphocytic cell line. HIV-1 RNA and protein levels in infected Dami cells were enhanced by treatment with tumor necrosis factor-alpha (TNF-alpha), and decreased by treatment with interferon-alpha (IFN-alpha) and IFN-gamma. Transient transfection of the megakaryocytic cells with various constructs of the HIV-1 promoter (LTR) linked to the luciferase reporter gene suggested that the effect of TNF-alpha was related, as in monocytic and T-cell lines, to transactivation of the enhancer region of the HIV-1 LTR. These findings indicate that signals provided by the immune system may modulate HIV-1 expression in cells of the megakaryocytic lineage.
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PMID:Productive human immunodeficiency virus-1 infection of megakaryocytic cells is enhanced by tumor necrosis factor-alpha. 158 16

This study describes the derivation of a series of mutants from the human leukemic cell line CEM using the frame shift mutagen Ethyl-methanesulfonate followed by negative selection with multiple treatments of OKT4A + C, and sorting into CD4-, CD4-dull, and CD4-intermediate mutants. These mutants express reduced CD4 levels ranging from 0 to 60% of the parental line. The mutants were analyzed by staining with a battery of CD4-specific mAb, by assessing their ability to bind soluble gp120, and by their ability to form syncytia after infection with cell-free HIV I virus and a gp160-vaccinia vector. Two groups of particularly interesting mutants were identified: (1) CD4-dull mutants expressing only 5 to 10% of the wild type surface CD4 density, which nevertheless were infectable by HIV I and produced as many syncytia and reverse transcriptase activity as the parental line after infection with gp160-vaccinia or cell free HIV I. (2) CD4-intermediate mutants (30 to 60% of parental CD4 level), which express CD4-epitopes required for interaction with the HIV I envelope protein, yet are markedly deficient in their ability to form syncytia after gp160-vaccinia or HIV I infection. Two of these mutants did form syncytia after transient reconstitution with a wild type CD4 containing vaccinia vector. Inasmuch as they were found to bind soluble gp120 with the same avidity as other, functionally normal, CD4-intermediate mutants, these human T cell mutants may have a reduced susceptibility to HIV I infection due to the absence of a "fusogenic component" or to a structural alteration in a region of the CD4 molecule not required for binding of the HIV I envelope, but for the subsequent fusion and entry process.
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PMID:Chemically induced CD4 mutants of a human T cell line. Evidence for dissociation between binding of HIV I envelope and susceptibility to HIV I infection and syncytia formation. 169 Feb 35

A long asymptomatic period is one of the characteristics of human immunodeficiency virus (HIV) infection, despite its fatal consequences. Antiviral defense in HIV-infected individuals controls viral replication during this period. In the present study, we demonstrate that peripheral blood leukocytes (PBL) of asymptomatic HIV-1 carriers, following exogenous HIV-1 infection in vitro, do not support viral replication. These cells do not produce detectable amounts of reverse transcriptase or accumulate unintegrated proviral DNA. This is a striking contrast to the behavior of HIV-1-infected PBL of seronegative individuals, which produce large amounts of RT and unintegrated DNA. Such resistance to HIV-1 replication is not seen in PBL of patients with advanced disease. Since the binding of HIV-1 to CD4 molecule is not impaired in PBL of asymptomatic carriers, the interference with HIV replication must occur after the stage of virus binding. PBL lose their resistance when CD8+ lymphocytes are removed. In addition, these PBL are not resistant to an exogenous infection with HIV-2. These observations suggest that certain populations of CD8+ lymphocytes of asymptomatic HIV-1 carriers operate on the target cells in PBL to block viral replication in an HIV-1-specific manner. Such CD8+ lymphocyte-mediated interference with HIV replication could play an important role in the maintenance of the period of disease latency.
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PMID:Interference with human immunodeficiency virus (HIV) replication by CD8+ T cells in peripheral blood leukocytes of asymptomatic HIV carriers in vitro. 169 4

Heterosexual transmission of HIV-1 is likely to involve transmission of virus present in seminal fluid to inflammatory cells, particularly macrophages, present in the endometrium and peritoneal cavity. We have investigated the susceptibility of peritoneal macrophages and the corresponding autologous blood monocytes from normal women to infection by the BA-L strain of HIV-1. In 10 of 18 examples, peritoneal macrophages showed signs of infection within 4-5 days, which was earlier than the autologous monocytes. In contrast to peritoneal macrophages, lung macrophages from 10 of 11 normal donors failed to show significant reverse transcriptase (RT) values 3 weeks post infection. Monolayer cultures of monocytes cultured for 5 days prior to infection developed RT values similar overall to those of freshly isolated cells although individual donors varied as to which culture condition was optimal. The ease of infection of peritoneal macrophages did not correlate with levels of CD4 antigen or degree of pelvic inflammatory development, nor were macrophages harvested from women early in the menstrual cycle significantly more susceptible to infection than those collected from midcycle on. This unexplained heightened infectibility of peritoneal macrophages in a proportion of normal women suggests that those individuals could be more at risk for heterosexual transmission of HIV-1 infection.
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PMID:Variation of HIV infectibility of macrophages as a function of donor, stage of differentiation, and site of origin. 170 34

The CD4 molecule, a glycoprotein expressed primarily on the cell surface of specific T lymphocytes, is thought to function in T-cell antigen recognition and activation. In addition, CD4 serves as a receptor for human immunodeficiency virus type 1 (HIV-1) by a direct interaction with the HIV-1 surface glycoprotein (gp120). To further characterize the HIV-1-cell interaction, a HeLa cell line was established that expressed a chimeric molecule of CD4 and decay-accelerating factor (DAF). In the chimeric CD4-DAF molecule the transmembrane and cytoplasmic domains of CD4 were deleted and replaced with the carboxy-terminal 37 amino acids of DAF. This resulted in the anchoring of the extracellular domain of CD4 to the cell membrane via a glycophospholipid linkage. The glycophospholipid-anchored CD4 had a molecular size of approximately 56 to 62 kDa and was released following treatment of the cells with phosphatidylinositol-specific phospholipase C. HeLa cells expressing the CD4-DAF hybrid could be infected with HIV-1, as evidenced by reverse transcriptase activity, p24 core antigen content, and infectious virus production. In addition, transfection of the HeLa CD4-DAF cells with a plasmid that directs the synthesis of HIV-1 envelope glycoproteins or cocultivation with HeLa cells expressing the virus glycoproteins resulted in syncytium formation. These results indicate that the transmembrane and cytoplasmic domains of the CD4 molecule are dispensable for both HIV infection and syncytium formation.
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PMID:Human immunodeficiency virus infection and syncytium formation in HeLa cells expressing glycophospholipid-anchored CD4. 170 1

Four Epstein-Barr virus-positive lymphoblastoid cell lines (LCL) were successfully infected in vitro with immunodeficiency virus type 1 (HIV-1) as demonstrated by reverse transcriptase activity and p24 HIV antigen in culture supernatants, positive cell staining for gag-encoded HIV proteins, presence of viral HIV genome by Southern blot analysis and ulstrastructural observations. In addition, both HIV-1-infected B cells and their supernatants efficiently transactivated the chloramphenicol acetyl transferase reporter gene which is under the control of the HIV-1 long terminal repeat. The LCL cells displayed long-term HIV-1 infection and production, but no cytopathic effects were observed. Cytofluorimetric analysis did not detect membrane CD4 presence in the LCL cells before and after HIV-1 infection; moreover, a minute amount of CD4 mRNA was observed only in one of the LCL. A monoclonal antibody specific for the viral binding site of the CD4 molecule delayed, but did not block, HIV-1 infection of the LCL cells. Following HIV-1 infection, changes in LCL phenotype were observed, consisting of a decrease in CD23- and CD39-positive cells, and a concomitant increase of cells with surface CD10 and Bac-1. Furthermore, HIV-1-infected LCL cells did not grow in tight clumps, as usually observed in uninfected LCL, but as disperse suspensions, and formed more agar colonies than control LCL. However, despite this apparent acquisition of a malignant-like phenotype, c-myc proto-oncogene rearrangement was not detected. The appearance of cells with new characteristics did not seem due to clone selection by HIV-1 infection, since all the LCL conserved their clonotypic pattern of IgH chain rearrangement. The acquisition of malignant-like features by HIV-infected B cells might be clinically significant in terms of the pathogenesis of non-Hodgkin's B cell lymphomas, which occur frequently in AIDS patients.
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PMID:Infection of Epstein-Barr virus-transformed lymphoblastoid B cells by the human immunodeficiency virus: evidence for a persistent and productive infection leading to B cell phenotypic changes. 217 Jan 47

The general physical characteristics and replication of retroviruses are considered, along with assays for viral products. The specific agent for acquired immunodeficiency syndrome, the human immunodeficiency virus (HIV), is characterized as a lentivirus causing persistent, lifelong infection. While human immunodeficiency virus retroviruses share many of the same properties as other replication-competent viruses, genetic variability occurs among HIV isolates, and this variability may have a considerable effect on the virus' virulence, cell type specificity, viral susceptibility to antiviral compounds, clinical presentation, and disease progression. The most notable difference between HIV replication and other retroviruses is the intricate control of HIV gene expression by viral and cellular factors. Possible mechanisms by which HIV kills infected cells include the formulation of multinucleate syncytia; cytopathic components within the virions themselves; and interaction between viral envelope proteins and the CD4 molecule on the cell surface. Agents shown to inhibit viral replication at the level of the reverse transcriptase are phosphonoformate, sulfated polysaccharides, rifabutin, and nucleoside analogs, as well as purine and pyrimidine analogs. To date, only one nucleoside analog, zidovudine, has demonstrated clear clinical benefit and anti-HIV activity.
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PMID:Biology of retroviruses: detection, molecular biology, and treatment of retroviral infection. 219 45

Individuals infected by the human immunodeficiency virus type 1 (HIV-1) demonstrate progressive depletion and qualitative dysfunction of the helper T4 (CD4+) cell population. Mechanisms proposed for attrition of CD4+ T cells include direct cytopathicity of these mature cells following infection as well as infection of early T-lymphocyte progenitors. The latter mechanism could lead to failure to regenerate mature functioning CD4+ T cells. The present study determines the susceptibility of thymocytes at various stages of maturity to infection with HIV-1. Various normal thymocyte populations were inoculated with HIV-1, including unfractionated (UF), CD3- CD4- CD8- ["triple negative" (TN)], CD4+ CD8+ ["double positive" (DP)] thymocytes, and thymocyte populations obtained by limited dilution cloning. Cultures were studied for the presence of HIV-1 DNA by polymerase chain reaction in addition to examination for reverse transcriptase activity. We determined that transformed T-cell and thymocyte cell lines completely lacking CD4 were not susceptible to infection by HIV-1, whereas all of the following lines were: UF thymocytes (70-90% CD4hi+); DP thymocytes (99% CD4hi+); TN thymocytes (0% CD4hi+); and TCR alpha beta +, TCR gamma delta +, or CD16+ CD3- (natural killer) thymocyte clones expressing variable levels of CD4 and representing the progeny of TN thymocytes. [TCR alpha beta + and TCR gamma delta + refer to the chains of the T-cell antigen receptor (TCR), and CD4hi refers to a strong rightward shift (greater than 30 linear channels) of the CD4 curve on flow cytometric analysis compared with control.] Monoclonal antibodies (mAbs) to CD4 (T4a epitope) but not to CD3 (T3) were capable of blocking infection of mature and immature CD4hi+ thymocytes. Moreover, anti-CD4(T4a) mAbs also inhibited infection of CD4hi- TN thymocytes, indicating that these T-cell precursors--despite their apparent "triple negativity" (CD3- CD4hi- CD8-)--expressed sufficient CD4 molecules to become infected. Cell sorter analysis with a panel of CD4 mAbs demonstrated a mean shift of the mean fluorescence channel (MFC) with CD4 mAbs on TN thymocytes of 6 +/- 4 MFC units. Thus, intrathymic T-cell precursors and their progeny representing many stages of T-cell ontogeny are susceptible to infection by HIV-1, including early TN thymocytes, which express very low levels of CD4. Infection of multiple stages and multiple subsets of the T-cell lineage in man, mediated via the CD4 molecule, may explain the inability of the T-cell pool to regenerate in the setting of progressive HIV infection.
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PMID:Evidence for susceptibility of intrathymic T-cell precursors and their progeny carrying T-cell antigen receptor phenotypes TCR alpha beta + and TCR gamma delta + to human immunodeficiency virus infection: a mechanism for CD4+ (T4) lymphocyte depletion. 221 6


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