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)

An African lioness from the Zoo of Zurich had to be euthanized because of an inoperable tumor. The serum tested negative for feline leukemia virus (FeLV) p27 antigen by enzyme-linked immunosorbent assay (ELISA) but was strongly positive for feline immunodeficiency virus (FIV) antibodies by ELISA and Western blot. When her only offspring and mate were tested for FIV, high antibody titers to FIV were also found in their serum. Lymphocytes were prepared from these two lions on different occasions and co-cultivated with specific pathogen free (SPF) cat lymphocytes in the presence of concanavalin A and recombinant human interleukin-2 (IL-2) for 6 weeks. The cell culture supernatants tested negative for Mg(2+)-dependent reverse transcriptase and FIV p24 by a double antibody sandwich ELISA throughout the culture period. Whole blood and buffy coat cells collected from these two lions were transmitted by intraperitoneal injection into two SPF cats. The two cats did not seroconvert for a period of 11 months nor could reverse transcriptase activity and FIV p24 antigen be demonstrated in the supernatant of several lymphocyte cultures. To determine the importance of lentivirus infections in zoo-kept wild felids, 124 serum samples were obtained from African lions, Indian and Siberian tigers, snow leopards, panthers, cheetahs and other wild cats from nine European zoos. In addition, serum samples collected from 12 Asiatic lions originating from Gir forest in the Indian State of Gujarat were included in this study. The sera were tested for antibodies to FIV, FeLV and feline syncytium-forming virus (FeSFV) by ELISA and Western blot using the respective viruses after gradient purification. In addition, some of the sera were also tested for antibodies to equine infectious anemia virus (EIAV) and Visna-Maedi virus (VMV). Antibodies to FIV were found in 30/53 (57%) of African lions, one of 18 tigers and one of four panthers. All other sera including those collected from the 12 Asiatic lions were negative for FIV antibodies. Some of the FIV positive lion sera had high antibody titers producing strong bands on Western blot strips even in dilutions of >> 1:1000. The Western blot pattern of the lion sera differed from that of domestic cats in that primarily p24 and to a lesser degree p17 was recognized. Antibodies to FeSFV were found in 14 animals (seven with strong, seven with intermediate, reaction). No correlation was found between FIV and FeSFV infection. Antibodies to FeLV were found in two cheetahs which later turned out to have been vaccinated with Leukocell, a FeLV vaccine.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Retrovirus infections in non-domestic felids: serological studies and attempts to isolate a lentivirus. 133 98

Human immunodeficiency virus (HIV) has been implicated as the etiologic agent of acquired immunodeficiency syndrome and is a member of the sub-family Lentivirinae within the family Retroviridae. HIV type 1 (HIV-1) contains three major genes, gag, pol and env, which code for (1) core proteins, (2) a protease, reverse transcriptase and integrase, and (3) envelope glycoproteins, respectively. The core proteins p17, p24 and p15 are derived from gag precursor, p55, by endoproteolytic cleavage. The two nucleic-acid-binding proteins p7 and p9 are synthesized from p15 by proteolytic cleavage. These two structural proteins are apparently needed for the ribonucleoprotein-core formation. The envelope glycoproteins gp120 and gp41 (gp120-gp41 complex) are also generated by cleavage env precursors, gp160. The assembly of HIV-1 particles, like other retroviruses, appears to involve the association of the env precursor gp160 with the gag proteins. There are several factors which influence the assembly and budding process of HIV-1. In this article, we describe important events in HIV-1 morphogenesis and factors which influence this aspect of the HIV-1 life cycle.
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PMID:Morphogenesis of human immunodeficiency virus type 1. 138 14

The gag-pol coding region of the HIV-2BEN genome was expressed in CV-1 cells infected with four recombinant vaccinia viruses (VV). These recombinant VV encoded either the whole gag-pol region or the gag gene including the protease-coding region of the pol gene or the gag gene truncated at its 3'-end or only the pol gene. The HIV-2BEN gag precursor p55, its mature cleavage products p24 and p17 as well as the pol reverse transcriptase (RT) p66 were detected in VV-infected CV-1 cells. The p55 and two intermediate cleavage products p40 and p35 were myristilated. Comparison to lysates of permanently HIV-2BEN-infected Molt 4 clone 8 cells revealed that several additional gag and pol proteins were present in the VV-infected CV-1 cells. Deletion of the gag and pol overlapping region coding for the viral protease prevented cleavage of the recombinant gag precursor. Electron microscopy of VV-infected CV-1 cells revealed budding structures and immature as well as mature retroviral particles formed by the recombinant gag proteins. Striking differences in the ability to form complete particles were observed between the different recombinant VV. Expression of the truncated gag gene led to the formation of budding structures, but completely budded circular particles were not detectable. Such particles were produced by expression of the whole gag gene and the protease. Mature virions with an internal core structure were only detected in VVgagpol-infected cells. From these findings we conclude that the 3'-end of the gag gene coding for the p16 protein is essential for the formation of complete HIV-2 particles and that the pol proteins support the assembly of the viral core.
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PMID:Morphogenesis of recombinant HIV-2 gag core particles. 152 43

The gag and pol genes of the human immunodeficiency virus type 1 (HIV-1) (ref. 1) are translated as two polyproteins, Pr55gag and Pr160gag-pol (refs 2-6), which are subsequently cleaved by the action of a virus-encoded protease into the four structural gag proteins of the virion core (p17, p24, p7 and p6) and the pol-encoded enzymes essential for retrovirus replication (protease, reverse transcriptase, ribonuclease H, and endonuclease). Mutational inactivation of the proteases of HIV-1 and other retroviruses results in immature, non-infectious virions, indicating that exogenous inhibition of the protease may represent an attractive approach to anti-AIDS therapy. Here we demonstrate that synthetic peptide analogues, which are potent inhibitors of purified HIV-1 protease, inhibit the processing of the viral polyproteins in cultures of HIV-1-infected T lymphocytes and attenuate viral infectivity.
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PMID:Inhibition of HIV-1 protease in infected T-lymphocytes by synthetic peptide analogues. 168 46

Retroviruses encode proteinases necessary for the proteolytic processing of the viral gag and gag-pol precursor proteins. These enzymes have been shown to be structurally and functionally related to aspartyl proteinases such as pepsin and renin. Cerulenin is a naturally occurring antibiotic, commonly used as an inhibitor of fatty acid synthesis. Cerulenin has been observed to inhibit production of Rous sarcoma virus and murine leukaemia virus by infected cells, possibly by interfering with proteolytic processing of viral precursor proteins. We show here that cerulenin inhibits the action of the HIV-1 proteinase in vitro, using 3 substrates: a synthetic heptapeptide (SQNYPIV) which corresponds to the sequence at the HIV-1 gag p17/p24 junction, a bacterially expressed gag precursor, and purified 66 kDa reverse transcriptase. Inhibition of cleavage by HIV-1 proteinase required preincubation with cerulenin. Cerulenin also inactivates endothiapepsin, a well-characterised fungal aspartyl proteinase, suggesting that the action of cerulenin is a function of the common active site structure of the retroviral and aspartic proteinases. Molecular modelling suggests that cerulenin possesses several of the necessary structural features of an inhibitor of aspartyl proteinases and retroviral proteinases. Although cerulenin itself is cytotoxic and inappropriate for clinical use, it may provide leads for the rational design of inhibitors of the HIV proteinase which could have application in the chemotherapy of AIDS.
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PMID:In vitro inhibition of HIV-1 proteinase by cerulenin. 169 Jan 52

We have succeeded in infecting human thymic lymphocytes with both the HIV-IIIB laboratory strain of HIV-1 as well as with a clinical isolate of this virus. Thymic lymphocytes were at least as susceptible to infection by HIV-1 as were cord blood lymphocytes, but appeared to display somewhat greater resistance to the cytopathic effects of the virus. As measured variously by each of indirect immunofluorescence for detection of viral p17, antigen capture assay for the presence of viral p24 in culture fluids, and levels of viral reverse transcriptase activity in culture fluids, infection of thymic lymphocytes could be detected as early as 2 days after infection by HIV-1, and persisted through at least 14 days of tissue culture maintenance. These findings suggest that thymic lymphocytes may be susceptible to infection by HIV-1 in vivo, and may also be relevant to our understanding of HIV-1-induced pathogenesis, particularly in pediatric populations.
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PMID:Infection of human thymic lymphocytes by HIV-1. 169 Feb 86

The reverse transcriptase enzyme of HIV-1 is known to be error-prone. We were interested in the possibility of isolating a variant HIV-1 strain that might be capable of replication in the presence of AZT, thought to act by antagonizing reverse transcriptase activity. Toward this end, chronically infected H-9 cells were exposed to various concentrations of AZT for at least 500 days. No mutant has yet arisen from such cultures, which continued to produce high levels of each of the viral proteins p24, p17, gp41, and gp51/66 in the presence of the drug. Notwithstanding such expression of viral antigens, culture fluids from these various AZT-treated cultures were not capable of infecting otherwise susceptible target cells. Electron microscopic observations of AZT-treated chronically infected H-9 cells indicated a lower production of viral structures, in comparison with control cultures. Furthermore, those particles seen at the plasma membrane of AZT-treated cells often appeared to be envelope-deficient. These data suggest that AZT may be able to interfere in some way with proper assembly and/or packaging of infectious progeny HIV-1 at the cell membrane, although other modes of action for a postintegrational effect of AZT cannot be excluded.
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PMID:AZT (zidovudine) may act postintegrationally to inhibit generation of HIV-1 progeny virus in chronically infected cells. 169 85

An expression vector (pU3R-III/2-5AS) of human 2',5'-oligoadenylate (2-5A) synthetase was constructed in which a cDNA encoding an active form of the enzyme was located 3' to a 3'-long terminal repeat (LTR) of human immunodeficiency virus type 1 (HIV-1). The LTR-directed expression of this hybrid DNA could be activated in trans by the HIV tat gene product. This vector was used for transfection of HeLa-T4+ cells, which are permissive to HIV infection, as well as of normal HeLa cells. HIV replication after infection of the CD4-receptor-bearing HeLa-T4+ cells with HIV-1 was found to be strongly reduced when drug-selected cells cotransfected with pU3R-III/2-5AS and a hygromycin B resistance gene containing plasmid were used. In nontransfected cultures or after transfection with the selectable marker plasmid only, about 60% p17- and p24-positive cells were found 5 days after infection. However, after stable transfection with pU3R-III/2-5AS the number of positive cells was decreased to about 2%. The reverse transcriptase (RT) activity, as a measure for virus production, was markedly decreased in the culture fluids of pU3R-III/2-5AS transfected cells compared with the mock-transfected controls. In parallel experiments it was established that Tat-mediated trans-activation of HIV-1 LTR-directed 2-5A synthetase expression resulted in a great increase in both 2-5A synthetase mRNA level and activity as well as in cellular 2-5A content. Similar results were found in HeLa-T4+ cells and in HeLa cells (without CD4 receptor) cotransfected with pU3R-III/2-5AS and a tat gene containing plasmid or after introduction of purified Tat protein into the pU3R-III/2-5AS transfected cells by using a modified scrape loading procedure. These results indicate that HIV-trans-activated 2-5A synthetase can selectively inhibit HIV replication in vitro, and might be a promising gene therapeutical approach.
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PMID:Protection of HeLa-T4+ cells against human immunodeficiency virus (HIV) infection after stable transfection with HIV LTR-2',5'-oligoadenylate synthetase hybrid gene. 169 80

Mutations were introduced by recombinant DNA techniques into 9 genes of an infectious molecular clone of human immunodeficiency virus type 1. The 24 mutants generated were characterized biochemically and biologically by transfection and infection experiments. None of the mutants which have mutations in gag (p17, p24, and p15 regions), pol (protease, reverse transcriptase, and endonuclease domains), env (gp120 region), tat, or rev were infectious, whereas vif, vpr, vpu, some of env (gp41) and nef mutants could grow in human CD4+ cells to various degrees. Of the non-infectious mutants, only endonuclease (pol) and gp41 mutants exhibited normal phenotypes with respect to the production of functional reverse transcriptase, the expression of gag, pol, and env proteins, and the generation of progeny virions, when examined in transient assays. All infectious mutants killed the CD4+ cells with the exception of a mutant carrying a defect in the vif gene.
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PMID:Generation and characterization of the human immunodeficiency virus type 1 mutants. 170 90

Crude extracts of dried leaves of Hyssop officinalis showed strong anti-HIV activity as measured by inhibition of syncytia formation, HIV reverse transcriptase (RT), and p17 and p24 antigen expression, but were non-toxic to the uninfected Molt-3 cells. Ether extracts from direct extraction (Procedure I), after removal of tannins (Procedure II), or from the residue after dialysis of the crude extract (Procedure III), showed good antiviral activity. Methanol extracts, subsequent to ether, chloroform and chloroform ethanol extractions, derived from procedure I or II, but not III, also showed very strong anti-HIV activity. In addition, the residual material after methanol extractions still showed strong activity. Caffeic acid was identified in the ether extract of procedure I by HPLC and UV spectroscopy. Commercial caffeic acid showed good antiviral activity in the RT assay and high to moderate activity in the syncytia assay and the p17 and p24 antigen expression. Tannic acid and gallic acid, common to other teas, could not be identified in our extracts. When commercial products of these two acids were tested in our assay systems, they showed high to moderate activity against HIV-1. Hyssop officinalis extracts contain caffeic acid, unidentified tannins, and possibly a third class of unidentified higher molecular weight compounds that exhibit strong anti-HIV activity, and may be useful in the treatment of patients with AIDS.
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PMID:Inhibition of HIV replication by Hyssop officinalis extracts. 170 26


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