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At least 1,711 records · Page 95Linked to original sources
PubMed1998

Host control of HIV-1 parasitism in T cells by the nuclear factor of activated T cells.

Post HIV-1 entry, productive HIV-1 infection of primary T cells requires overcoming several cellular blocks to provirus establishment and replication. Activation of unknown host intracellular events overcomes such inhibitory steps and is concomitant with HIV-1 replication. We show that the transcription factor NFATc was sufficient as a cellular factor to induce a highly permissive state for HIV-1 replication in primary CD4+ T cells. NFATc overcame a blockade at reverse transcription and permitted active HIV-1 replication. Pharmacologic blockade of endogenous NFAT activity by FK506 or CsA inhibited synthesis of reverse transcription and also potently blocked HIV-1 replication. T cells therefore can become competent for HIV-1 replication by control of regulated host factors such as the NFATc transcription factor. The host mechanisms regulated by such permissivity factors are potential targets for anti-HIV-1 therapy.

CD4-Positive T-Lymphocytes↗
PubMedDate not supplied

Inhibition of HIV-1 replication by hydroxychloroquine: mechanism of action and comparison with zidovudine.

We have previously described the inhibition of human immunodeficiency virus serotype 1 (HIV-1) using the antimalarial hydroxychloroquine (HCQ), a weak base that inhibits the posttranslational modification of glycoprotein 120 (gp 120) in T cells and monocytes. The mechanism of inhibition of gp 120 production was presumed to be the ability of HCQ to increase endosomal pH and therefore alter enzymes required for gp120 production. To further clarify this action, we have determined the effect of HCQ and its enantiomers on endosomal pH. Pretreatment of cells with HCQ and the levo- and dextro-enantiomers at concentrations demonstrated to suppress anti-HIV-1 activity increased endosomal pH to levels similar to increases seen with chloroquine and ammonium chloride, two other weak bases, and decreased gp 120 production. The dextro- and levo-enantiomers suppressed HIV-1 replication to a similar extent and were no more toxic than racemic HCQ. We next compared the anti-HIV-1 effect of HCQ with zidovudine (ZDV) in both newly and chronically HIV-1-infected T-cell and monocytic cell lines (63 and 63HIV). HCQ suppressed HIV-1 replication in a dose-dependent manner in both recently and chronically infected T-cell and monocytic cell lines. In contrast, ZDV pretreatment had potent anti-HIV-1 activity in the newly infected T and monocytic cells but not in chronically infected cells. An additive effect of HCQ with ZDV was observed in the newly infected T and monocytic cells but not in the chronically infected cells. Although the anti-HIV-1 effect of HCQ was less than that of ZDV, HCQ may still be potentially useful either as an alternative HIV-1 treatment or in combination with other anti-HIV-1 agents, especially in patients who have rheumatic manifestations of HIV-1 infection.

Anti-HIV Agents↗
PubMed2002

Construction and characterisation of infectious recombinant HIV-1 clones containing CTL epitopes from structural proteins in Nef.

In this study the construction is described of HIV-1 molecular clones in which CTL epitopes from RT or Env late proteins were inserted into the Nef early protein. The ectopic epitopes were efficiently processed from the recombinant Nef proteins, were recognized by their cognate CTL in cytolytic assays, and did not perturb virus replication or viral protein expression in vitro. These recombinant viruses will therefore be an important tool in studying the effect of distinct epitope expression kinetics on the efficiency of CTL-mediated suppression of HIV-1 replication.

Amino Acid Sequence↗
PubMed2002

Inhibitory effects of (-)-epigallocatechin gallate on the life cycle of human immunodeficiency virus type 1 (HIV-1).

Epigallocatechin gallate (EGCg), the major tea catechin, is known as a potent anti-bacterial agent. In addition, anti-tumor promoting, anti-inflammatory, anti-oxidative and antiviral activities have been reported. In the present study, we investigated possible anti-human immunodeficiency virus type-1 (HIV-1) activity of EGCg and its mechanisms of action in the viral life cycle. EGCg impinges on each step of the HIV life cycle. Thus, destruction of the viral particles, viral attachment to cells, post-adsorption entry into cells, reverse transcription (RT), viral production from chronically-infected cells, and the level of expression of viral mRNA, were analyzed using T-lymphoid (H9) and monocytoid (THP-1) cell systems, and antiviral protease activity was measured using a cell-free assay. Inhibitory effects of EGCg on specific binding of the virions to the cellular surfaces and changes in the steady state viral regulation (mRNA expression) due to EGCg were not observed. However, EGCg had a destructive effect on the viral particles, and post-adsorption entry and RT in acutely infected monocytoid cells were significantly inhibited at concentrations of EGCg greater than 1 microM, and protease kinetics were suppressed at a concentration higher than 10 microM in the cell-free study. Viral production by THP-1 cells chronically-infected with HIV-1 was also inhibited in a dose-dependent manner and the inhibitory effect was enhanced by liposome modification of EGCg. As expected, increased viral mRNA production was observed in lipopolysaccharide (LPS)-activated chronically HIV-1-infected cells. This production was significantly inhibited by EGCg treatment of THP-1 cells. In contrast, production of HIV-1 viral mRNA in unstimulated or LPS-stimulated T-lymphoid cells (H9) was not inhibited by EGCg. Anti-HIV viral activity of EGCg may thus result from an interaction with several steps in the HIV-1 life cycle.

Anti-HIV Agents↗
PubMed2004

Genotypic resistance profile in treatment-experienced HIV-infected individuals after abacavir and efavirenz salvage regimen.

Once highly active antiretroviral therapy (HAART) fails to suppress HIV replication and resistant viruses emerge, it is difficult to find a salvage regimen since cross-resistance is high among the available classes of antiretroviral drugs. In this retrospective analysis, genotypic resistance profiles were analysed in 24 patients who switched treatment to abacavir (ABV), efavirenz (EFV), and either a NRTI or a PI at baseline and after 24 weeks of treatment. At baseline, 71% of patients harboured at least one resistance mutation in the protease gene. In the RT gene, 87.5% of the patients showed nucleoside analogue resistance mutations, and an equal 87.5% showed resistance mutations to non-nucleoside analogues. After 24 weeks of treatment, only mutations to nucleoside analogues raised in 95.8% of the patients, while resistance mutations to the other drug classes remained constant. Substitutions conferring cross-resistance within each drug family were very common among this treatment-experienced population. These data also indicate that salvage therapy is likely to remain one of the most important issues in the treatment of HIV infections.

Alkynes↗
PubMed1997

Evaluation of anti-AIDS drugs in conventional mice implanted with a permeable membrane device containing human T cells infected with HIV.

We now report the confirmation of the work of Hollingshead et al. (1995) on development of a cell based hollow fiber (HF) system for evaluating potential anti-AIDS drugs in vivo using conventional mice rather than SCID mice. CD4 +, CEM-SS cells infected with HIV/1, strain RF, at a multiplicity of infection of 0.1 were placed into HFs. The fibers were implanted into the peritoneal cavity of outbred Swiss mice. Using this model, the antiviral activity of azidothymidine (AZT) at doses of approximately 150, 75 and 37.5 mg/kg/day was evaluated by administering AZT to the mice in drinking water. Upon fiber removal on day 6, AZT treatment was shown to significantly increase CEM cell viability over the untreated, virus control group and significantly reduced the levels of HIV p24 and HIV RT activity.

Acrylic Resins↗
PubMed1999

Development and optimization of anti-HIV nucleoside analogs and prodrugs: A review of their cellular pharmacology, structure-activity relationships and pharmacokinetics.

Significant improvements in antiviral therapy have been realized over the past 10 years. Numerous nucleoside analogs, as well as prodrugs of active compounds, have been synthesized and tested for anti-HIV activity. In addition to the five nucleoside analogs currently used clinically for the treatment of HIV infection, a broad spectrum of anti-HIV nucleoside analogs (including 2',3'-dideoxynucleoside analogs, oxathiolanyl 2',3'-dideoxynucleoside analogs, dioxolanyl 2',3'-dideoxynucleoside analogs, carbocyclic 2',3'-dideoxynucleoside analogs and acyclic nucleoside analogs) and their prodrugs (including ester prodrugs, phospholipid prodrugs, dihydropyridine prodrugs, pronucleotides and dinucleotide analogs), targeted at HIV reverse transcriptase, are reviewed with focus on structure-activity relationships, cellular pharmacology and pharmacokinetics. Several of these anti-viral agents show promise in the treatment of AIDS.

Journal Article↗
PubMed1999

In vitro immunization with a recombinant antigen carrying the HIV-1 RT248-262 determinant inserted at different locations results in altered TCRVB region usage.

Immunodominance or cripticity of a peptide-borne determinant may be influenced by the protein context in which the epitope is embedded. In this frame, we previously showed that certain human T cell clones, derived from different donors, may differentially recognize the RT248-262 helper determinant depending on whether it is provided to the presenting cells as a synthetic peptide or as a recombinant carrier protein to which the sequence of interest is fused. We now report that, upon in vitro immunization of human PBL with autologous APC, the epitope-specific TCRVB repertoire obtained when selection is applied by pulsing the APC with the cognate synthetic peptide is different from that found when a recombinant protein is used in which the antigenic sequence is placed at either a N-terminal or C-terminal location of the GST carrier. As the TCRVB distribution is not a function of the APC used, we propose that processing of different recombinant molecules containing the same epitope may generate MHC/peptide complexes which, being antigenically diverse, may recruit distinct TCR specificities. These findings may be relevant for evaluating and predicting the immunogenic potential of subunit vaccines based on synthetic peptides or on recombinant proteins as compared to the native antigen.

Amino Acid Sequence↗
PubMedDate not supplied

Inhibition of human immunodeficiency virus type 1 infection in a T-cell line (CEM) by new dipeptidyl-peptidase IV (CD26) inhibitors.

Phenylalanyl-pyrrolidine-2 nitrile (Phe-pyrr-2-CN) and arginyl(PMC)-pyrrolidine-2-nitrile (Arg(PMC)-pyrr-2-CN) are two dipeptidyl peptidase IV/CD26 (DPP-IV/CD26) inhibitors designed and synthesized by our group. These two compounds suppress the enzymatic activity of DPP-IV/CD26 in a competitive and reversible manner. Pretreatment of CEM cells with either of the compounds yielded a marked albeit transient reduction of HIV infection, as measured by HIV1 p24 production, RT activity and syncytium formation. The ID50 value of the Phe-Pyrr-2-CN and Arg(PMC)-pyrr-2-CN in HIV1 inhibition was 5.3 microM and 2.4 microM, respectively. Administration of either of the DPP-IV/CD26 inhibitors 1 h after HIV1 infection did not suppress HIV1 production. An analog whose inhibitory activity toward DPP-IV/CD26 was abolished by blocking the N-terminal of Phe-pyrr-2-CN with the 9-fluorenymethyloxycarbonyl (Fmoc) group had no effect on HIV1 infection. An additive effect of HIV1 inhibition was observed in combinations of either of the DPP-IV/CD26 inhibitors with CD4 monoclonal antibody. These results suggest that DPP-IV/CD26 enzymatic activity may play a role in facilitating HIV1 infection of human CD4+T cells at the entry process. DPP-IV/CD26 inhibitors may therefore have potential use in combination with other drugs to prevent HIV1 transmission.

Anti-HIV Agents↗
PubMedDate not supplied

Susceptibility of human lymphoblastoid B-cell line CE to HIV1 infection.

In this preliminary report, we provide evidence that the human B-lymphoblastoid cell line (LCL) CE, bone-marrow-derived, previously reported to be permissive to hepatitis C virus, is also permissive to HIV1 infection. HIV1 genomes were detectable in cell supernatants, virus RNA transcripts and proviral DNAs in cell extracts at different times post-infection. Therefore, we propose this LCL cell line as a tool for exploring the mutual interactions of the two viruses in double-infected cells.

B-Lymphocytes↗
PubMed2001

A 'cassette' RNase: site-selective cleavage of RNA by RNase S equipped with RNA-recognition segment.

RNase S is a unique protein comprising the non-covalent association of two components, the S-peptide and the S-protein. An RNA-recognition segment derived from the human immunodeficiency virus (HIV)-1 Rev protein was conjugated with the S-peptide to form a complex with the S-protein. The resulting RNase S bearing the RNA-recognition segment preferentially hydrolyzed a single position of the RNA stem-loop derived from the specific binding site for the Rev protein.

Amino Acid Sequence↗
PubMed1995

HIV-1 virology. Simply Marvelous nuclear transport.

HIV-1 MA protein is a viral membrane protein, but it is also involved in nuclear import of the preinitiation complex; the latter requires transfer of some MA molecules to the maturing core particle during virus assembly.

Biological Transport↗
PubMed1999

Crystal structure of the RNA-dependent RNA polymerase of hepatitis C virus.

BACKGROUND: Hepatitis C virus (HCV) is the major etiological agent of hepatocellular carcinoma, and HCV RNA-dependent RNA polymerase (RdRp) is one of the main potential targets for anti-HCV agents. HCV RdRp performs run-off copying replication in an RNA-selective manner for the template-primer duplex and the substrate, but the structural basis of this reaction mechanism has still to be elucidated. RESULTS: The three-dimensional structure of HCV RdRp was determined by X-ray crystallography at 2.5 A resolution. The compact HCV RdRp structure resembles a right hand, but has more complicated fingers and thumb domains than those of the other known polymerases, with a novel alpha-helix-rich subdomain (alpha fingers) as an addition to the fingers domain. The other fingers subdomain (beta fingers) is folded in the same manner as the fingers domain of human immunodeficiency virus (HIV) reverse transcriptase (RT), another RNA-dependent polymerase. The ribose-recognition site of HCV RdRp is constructed of hydrophilic residues, unlike those of DNA polymerases. The C-terminal region of HCV RdRp occupies the putative RNA-duplex-binding cleft. CONCLUSIONS: The structural basis of the RNA selectivity of HCV RdRp was elucidated from its crystal structure. The putative substrate-binding site with a shallow hydrophilic cavity should have ribonucleoside triphosphate (rNTP) as the preferred substrate. We propose that the unique alpha fingers might represent a common structural discriminator of the template-primer duplex that distinguishes between RNA and DNA during the replication of positive single-stranded RNA by viral RdRps. The C-terminal region might exert a regulatory function on the initiation and activity of HCV RdRp.

Amino Acid Sequence↗
PubMed1995

X-ray structure of human nucleoside diphosphate kinase B complexed with GDP at 2 A resolution.

BACKGROUND: Nucleoside diphosphate (NDP) kinases provide precursors for DNA and RNA synthesis. In mammals, these enzymes are also involved in cell regulations. Human NDP kinase B, product of the human nm23-H2 gene, is both an enzyme and a transcription factor. It activates transcription of the c-myc oncogene independently of its catalytic function, by binding to its promoter DNA. How do the two functions coexist? RESULTS: Recombinant human NDP kinase B was co-crystallized with GDP. The X-ray structure was solved at 2.0 A resolution by molecular replacement from the homologous Drosophila Awd protein. Both enzymes are homo-hexamers with a characteristic beta alpha beta beta alpha beta fold. GDP binds near the active site His118. The guanine base is in a surface cleft and interacts with the C terminus of another subunit. CONCLUSIONS: The beta alpha beta beta alpha beta fold, also present in the 'palm' domain of Escherichia coli DNA polymerase I and HIV reverse transcriptase, is both a mononucleotide- and a polynucleotide-binding fold. If NDP kinase B binds DNA in the same way as the polymerases, the enzyme must undergo a conformation change in order to carry out gene activation.

Amino Acid Sequence↗
PubMed1998

Crystal structure and conformation of a DNA-RNA hybrid duplex with a polypurine RNA strand: d(TTCTTBr5CTTC)-r(GAAGAAGAA).

BACKGROUND: . DNA-RNA hybrids are substrates for RNase H. This enzyme catalyzes the hydrolysis of the RNA strand in the hybrid form. The polypurine tract (PPT) in human immunodeficiency virus 1 (HIV-1) is a short stretch of purines ( approximately 15 bases) located at the 3'-end of the U3 region of the RNA genome. The PPT has the unique ability to resist digestion by RNase H and serves as a primer for plus-strand DNA synthesis. RESULTS: . The crystal structure of a DNA-RNA hybrid duplex containing a polypurine RNA strand, d(TTCTTBr5CTTC)-r(GAAGAAGAA), has been determined at 1.8 A resolution. The structure was solved by molecular replacement methods and refined to a final R factor of 20.1% (R free 23.7%). The hybrid duplex adopts a standard A-form conformation. All of the sugar rings and glycosidic torsion angles are found in the standard C3'-endo/anti conformation, as seen in A-RNA or A-DNA. The crystal packing is dominated by the DNA strand, where the terminal base pairs of the hybrid abut the neighboring A-DNA sugar-phosphate backbone on the minor groove side. CONCLUSIONS: . The present DNA-RNA hybrid duplex containing a polypurine RNA strand exhibits standard A-form geometry. This observation might suggest that the RNA PPT resists the RNase H activity of HIV reverse transcriptase as a result of its A-form conformation. In addition, there appears to be a correlation between the percentage purine content of the RNA and the DNA backbone conformation.

Crystallography↗
PubMed2003

Compaction agent clarification of microbial lysates.

Recombinant proteins are often purified from microbial lysates containing high concentrations of nucleic acids. Pre-purification steps such as nuclease addition or precipitation with polyethyleneimine or ammonium sulfate are normally required to reduce viscosity and to eliminate competing polyanions before anion exchange chromatography. We report that small polycationic compaction agents such as spermine selectively precipitate nucleic acids during or after Escherichia coli lysis, allowing DNA and RNA to be pelleted with the insoluble cell debris. Analysis by spectrophotometry and protein assay confirmed a significant reduction in the concentration of nucleic acids present, with preservation of protein. Lysate viscosity is greatly reduced, facilitating subsequent processing. We have used 5mM spermine to remove nucleic acids from E. coli lysate in the purification of a hexahistidine-tagged HIV reverse transcriptase.

Bacteriolysis↗
PubMed2002

Subtle mutations in the cysteine region of HIV-1 Vif drastically alter the viral replication phenotype.

Mutations were introduced into the region encoding the two cysteine and nearby amino acid residues of human immunodeficiency virus type 1 (HIV-1) Vif protein and, 12 single-amino-acid viral mutants were constructed. Determination of their growth characteristics in two lymphocytic cell lines revealed that only a single amino acid change in the cysteine region greatly altered the replication phenotype. In particular, the four mutants of amino acid 132 of Vif were grouped into three categories on the basis of their growth potentials. These results indicate that the cysteine region of Vif is critical for the cell-dependent replication efficiency of HIV-1.

Cells, Cultured↗