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Query: UMLS:C0019693 (HIV)
 170,526 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human immunodeficiency virus type 1 (HIV-1) isolates are genetically so heterogeneous that they must be described in terms of populations of related but distinct genomes called quasispecies. A recent study of the influence of ex vivo culturing on HIV-1 quasispecies demonstrated that usually low-abundance genomes outgrew the more prominent forms. Here it is shown that multiple passages of an HIV-1 isolate on peripheral blood mononuclear cells resulted in the outgrowth of very minor forms. A single passage of equal proportions of supernatants to either of the established lymphocyte and monocyte cell lines Molt-3 and U937-2, respectively, resulted in the isolation of different sets of minor forms. Recombination between component sequences was observed. Extensive and monotonous base substitutions of G----A (G----A hypermutation) were evident in many sequences. A strong preference for the transition within the GpA dinucleotide was observed. Dislocation mutagenesis, in this case, a -1 slippage or dislocation of the primer with respect to the template, during DNA synthesis by the HIV-1 reverse transcriptase would explain this bias. When the consequences of polymerase errors, recombination, hypermutation, and instability are added to the genetic description of HIV-1, the real complexity of this virus starts to become apparent.
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PMID:Selection, recombination, and G----A hypermutation of human immunodeficiency virus type 1 genomes. 200 43

Human immunodeficiency virus type 1 (HIV-1) gene expression is activated by Tat, a virally encoded protein. Tat trans-activation requires viral (trans-activation--responsive; TAR) RNA sequences located in the R region of the long terminal repeat (LTR). Existing evidence suggests that Tat probably cooperates with cellular factors that bind to TAR RNA in the overall trans-activation process. A HeLa complementary DNA was isolated and characterized that encodes a TAR RNA-binding protein (TRBP). TRBP activated the HIV-1 LTR and was synergistic with Tat function.
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PMID:Characterization of a human TAR RNA-binding protein that activates the HIV-1 LTR. 201 39

Human immunodeficiency virus type 1 (HIV-1) infection in utero was examined by isolating the virus and detecting the HIV-1 DNA sequence from different fetal tissues. The brain, thymus, lung, liver, spleen, and placenta tissues from fetuses (10-23 weeks of gestation) born to HIV-1-infected asymptomatic mothers were examined. HIV-1 was isolated from 2 of 7, 1 of 7, and 1 of 7 cocultures of splenic, thymic, and trypsin-resistant cells from the liver and placenta, respectively, with peripheral blood mononuclear cells; 20-30% and 40-60% of splenic and of thymic cells were CD4+ lymphoid cells and 40-80% of trypsin-resistant cells were mononuclear phagocytes. The HIV-1 DNA sequence was detected in 4 of 7, 3 of 7, 1 of 7, 1 of 7, 2 of 7, and 2 of 6 samples from the spleen, thymus, brain, lung, liver, and placenta, respectively, using the polymerase chain reaction. In one case, the intensity of the HIV-1 DNA sequence appeared to be correlated with the success of viral isolation. We indicate that fetal HIV-1 infection may frequently occur in the second trimester and the cells responsible for the infection may be CD4+ lymphoid cells and mononuclear phagocytes.
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PMID:Fetal human immunodeficiency virus type 1 infection of different organs in the second trimester. 201 16

Human immunodeficiency virus type 1 (HIV-1) NEF protein has been demonstrated to be a negative regulator of HIV-1 replication and HIV-1 LTR transcription under transient expression conditions. The difficulty of several laboratories to reproduce these findings led us to reexamine the role of NEF in HIV-1 provirus expression and HIV-1 LTR transcription. Basal transcription from the HIV-1 LTR in the presence of a NEF expression vector was compared to that in the presence of a mutated NEF vector. NEF expression led to a greater than 10-fold repression of LTR transcription under these conditions. HeLa and Jurkat cell lines carrying the nef gene linked to the CMV promoter or the HIV-1 LTR were isolated by coselection for neomycin resistance. Single cell isolates were further selected for the expression of nef transcripts. With the exception of the anti-sense nef cell lines, all the nef cell lines expressed the 27-kDa NEF protein, detectable by immunoprecipitation. NEF+ HeLa cell lines were at least 5-fold less efficient than NEF- HeLa cell lines in transient proviral expression. Provirus expression was also repressed in the NEF+ Jurkat cell lines. TAT-activated LTR transcription from an HIV-1 LTR-linked CAT expression vector was repressed 10-fold in the NEF+ HeLa and NEF+ Jurkat cell lines. When infected with HIV-1, NEF expressing T lymphoid cell lines showed moderate delays in onset and peak of reverse transcriptase production. However, none of these cell lines completely arrested virus replication. Our data confirm a negative regulatory effect of NEF on both virus production and LTR driven CAT expression in the cell lines tested. It is possible that cell specific factors may influence NEF activity.
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PMID:Human immunodeficiency virus type 1 (HIV-1) provirus expression and LTR transcription are repressed in NEF-expressing cell lines. 202 88

Human immunodeficiency virus type 1 (HIV-1) gene expression is regulated by viral and cellular factors interacting with cis-elements located in the retroviral long terminal repeat (LTR). In this report we analyzed HIV-1 LTR-specific regulatory sequences responsive to the HIV-1 Tat and HTLV-I Tax trans-activator proteins. Our results indicate that the Sp1 binding sites in the HIV-1 LTR are crucially involved in Tat-mediated gene expression in human Jurkat T-cells whereas they are dispensable for HTLV-I Tax-induced activation. In contrast, the NF-kB binding sites within the HIV-1 LTR are essential for Tax-mediated transcription but had only marginal effect on Tat-induced reporter gene expression.
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PMID:trans-activation of the HIV-1 LTR by the HIV-1 Tat and HTLV-I Tax proteins is mediated by different cis-acting sequences. 202 3

Human immunodeficiency virus type 2 (HIV-2) is similar in genetic organization to HIV-1 but contains a unique gene (vpx) that encodes a 16-kDa protein. A replication-competent molecular clone of HIV-2 (HIV-2sbl/isy) that infects human primary cells in vitro and rhesus monkeys was used to generate three mutations in the vpx gene. In the first mutant, the vpx open reading frame was truncated at amino acid 20; the second mutant was tailored to eliminate the proline-rich carboxyl terminus of the protein; and the third mutant was obtained by addition of four amino acids (KDEL) to the carboxyl terminus of the protein to provide a retention signal in the endoplasmic reticulum. The viral infection kinetics of the three mutant viruses and isogeneic HIV-2sbl/isy in the SupT1 cell line were similar. Slight impairment in the early phases of viral replication was observed during infection of primary human peripheral blood mononuclear cells with the vpx mutant viruses. All of the vpx mutant viruses readily infected macrophages, indicating that vpx expression is dispensable for HIV-2 infection and replication in human macrophages.
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PMID:Dispensable role of the human immunodeficiency virus type 2 Vpx protein in viral replication. 204 Nov 3

Human immunodeficiency virus type 1 (HIV-1) NEF protein has been reported to share certain biochemical and structural properties with known oncoproteins like src or rats. To determine whether this is a general property of NEF from various HIV isolates, three different NEF proteins were expressed in Escherichia coli using a thermoinducible expression system previously exploited to overproduce functionally active p21 ras proteins. ras and NEF proteins expressed in this manner were evaluated in parallel to compare their biochemical and biological properties. In contrast to ras, our NEF protein preparations had no detectable GTP binding but showed autophosphorylation activity when incubated in the presence of either GTP or ATP. This putative autokinase activity was higher in NEF proteins containing threonine at position 15 than in those carrying alanine at that position. Two different NEF genes also failed to induce oncogenic transformation of permanently transfected NIH 3T3 cells under conditions that led to oncogenic transformation using activated ras genes. Also, unlike ras, the NEF gene products failed to induce meiotic maturation when injected into fully grown Xenopus oocytes.
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PMID:Biochemical and biological comparison of HIV-1 NEF and ras gene products. 205 79

The neuropsychological development of 15 human immunodeficiency virus type 1 (HIV-1) seropositive children infected through neonatal blood transfusion was compared with that of a control group of 33 HIV-1 seronegative children who had also received blood transfusions as neonates. Human immunodeficiency virus type 1 infection was identified on the basis of a callback blood testing. Two thirds of the HIV-1-infected children were asymptomatic at time of enrollment in the study of development. The children were administered two psychological batteries approximately 8 months apart. The results indicated that the two serostatus groups did not differ in overall intelligence, even as long as 8 years after HIV-1 infection. Significant group differences, though slight, were found on school achievement and on tasks that require motor speed, visual scanning, and cognitive flexibility. Continued longitudinal study of this cohort will be important in characterizing the evolution of neuropsychological deficits.
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PMID:Neuropsychological functioning in human immunodeficiency virus type 1 seropositive children infected through neonatal blood transfusion. 205 75

Human immunodeficiency virus type 1 (HIV-1) specific cytotoxic T lymphocytes (CTL) have been detected in most patients following infection. It has also been suggested that the specific CTL response, which may play an important role in delaying disease in infected humans, may decline during the course of disease progression. We have measured HIV peptide specific CTL precursor frequency by limiting dilution analysis in two healthy seropositive patients whose fresh peripheral blood mononuclear cells (PBM) specifically lysed MHC matched target cells (restricted by HLA B27 and B8 respectively). The frequency of HIV peptide specific CTL precursors is high (3 x 10(-3)-10(-4], but lower than estimates of circulating CTL with the same specific cytotoxic activity present directly in peripheral blood using the same sample (10(-2)-10(-3]. We suggest that this difference may result from terminal effector CTL differentiation in the T cell lineage. This implies that only a subset of CTL effectors have growth potential, whereas relatively higher levels of CTL with lytic activity can be detected in PBM of healthy HIV seropositive patients.
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PMID:High frequency of memory and effector gag specific cytotoxic T lymphocytes in HIV seropositive individuals. 208 33

Eighty-six peripheral blood mononuclear cell (PBMC) samples from 30 patients with AIDS were analyzed using a transcription-based amplification system (TAS) and the polymerase chain reaction (PCR). Human immunodeficiency virus type 1 (HIV-1) sequences were detected by amplification-mediated hybridization in 98% of the samples, 52% of which were positive for p24 antigen by ELISA. Neither TAS (93%) nor PCR (95%) detected HIV-1 sequences in all 86 samples. The hybridization-detection methods (slot blot, bead-based sandwich, and solution) used to detect the HIV-1-specific TAS products had a clear influence on the efficiency of detecting and quantitating the levels of HIV-1 present in these samples. The reproducibility of amplification of constant amounts of HIV-1 RNA and beta-globin DNA by TAS and PCR was studied over 3 months. The results indicated that variations of 10- and 5-fold in the HIV-1 sequence levels could be detected between samples by TAS and PCR, respectively. Within the range of sensitivities for each assay used, the administration of zidovudine did not appear to reduce the amount of HIV-1 nucleic acid sequences as observed in PBMC obtained serially from six AIDS patients.
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PMID:Detection of human immunodeficiency virus type 1 in AIDS patients using amplification-mediated hybridization analyses: reproducibility and quantitative limitations. 211 72


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