Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0021051 (immunodeficiency)
 71,517 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Membrane fusion is an essential step in the infection of permissive cells with human immunodeficiency virus (HIV). Infected cells frequently fuse with each other, and then progress to form multinucleated giant cells (syncytia). To gain insight into mechanisms of HIV env-mediated membrane fusion, we developed a new assay for studying the initial events. The assay is based on the redistribution of fluorescent markers between membranes and cytoplasm of adjacent cells examined by means of fluorescence video microscopy. Membrane fusion between HIV-1 envelope glycoprotein (gp120/41) expressing effector cells and CD4+ target cells was observed 90 min after the association of cells, whereas the first syncytia only became apparent after 5 h. Moreover, membrane fusion events were observed under conditions where no syncytia were detected, for example, when the effector:target cell ratio was greater than 100:1, or less than 1:100. A significant number of cells with fused membranes were not involved in the syncytia. In order to determine whether quantitative differences in receptor expression might influence the extent of membrane fusion, we used laboratory-selected variants of CEM cells that differ in their expression of CD4. We found that CD4 is required on the target membrane for HIV env-mediated membrane fusion, but its extent is only partially dependent on CD4 surface concentration. The ability of those CEM variants to take part in HIV env-mediated membrane fusion did not correlate with their capacity to form syncytia. These findings indicate that additional steps are needed to form syncytia after membrane fusion.
 ...
PMID:Initial stages of HIV-1 envelope glycoprotein-mediated cell fusion monitored by a new assay based on redistribution of fluorescent dyes. 174 75

Based on a variety of independent assays, the expression of HIV (human immunodeficiency virus type 1) protease in living bacterial cells results in their loss of viability. Although the mechanism is not proven, we have observed degradation of cellular proteins in E. coli expressing large amounts of active HIV protease. In order to avoid the loss of viability, we devised an expression system in which the viral protease is fused to beta-lactamase and is rapidly secreted to the periplasmic space, thus reducing its duration in the cytosol. Furthermore, we find the periplasmic form of the protease is soluble and enzymatically is several-fold more active than enzyme recovered from intracellular aggregates. The question of whether the viral protease may be toxic to infected cells is discussed.
 ...
PMID:An E. coli expression system which detoxifies the HIV protease. 180 36

Recombinant sCD4-based proteins were evaluated for their effects on antigen-stimulated proliferation of human peripheral blood mononuclear cells (PBMC) and for antiviral activity against PBMC infected with human immunodeficiency virus (HIVD34). Two sCD4-based proteins were solubilized, refolded, and purified to homogeneity from recombinant E. coli and consisted of the 178 amino-terminal residues of CD4 fused with the translocating and catalytic domains of Pseudomonas exotoxin A (sCD4-PE40) or 183 amino-terminal residues of CD4 (sCD4-183); a third sCD4 consisting of 369 amino acids of CD4 was purified from recombinant mammalian cells for comparative purposes (sCD4-369). Increasing molar concentrations of these sCD4s were evaluated for inhibition of PBMC proliferation induced by alloantigen (MLR), by tetanus toxoid (TTOX), or in response to crosslinking with antibody to CD3 (OKT3). In addition, the concentrations of each protein required to inhibit replication of the HIVD34 isolate in primary PBMC was determined by quantitation of HIV p24 antigen released into supernatant fluids by infected cells. By comparing antiviral activity with anti-proliferative activity a relative estimate of the selectivity index for each recombinant sCD4 was determined. Proliferation of PBMC in response to alloantigen or OKT3 was less sensitive to inhibition than proliferation induced by TTOX, and the selectivity indices estimated for sCD4-PE40 were 170, 170 and 17, respectively. The selectivity index for sCD4-183 was greater than 350 under all assay conditions. Comparative evaluation of alloantigen-stimulated proliferation with antiviral activity of sCD4-183 versus sCD4-369 suggested that the E. coli-derived sCD4-183 may have a higher selectivity index under these conditions than its mammalian cell-derived counterpart.
 ...
PMID:Effects of a soluble CD4 and CD4-Pseudomonas exotoxin A chimeric protein on human peripheral blood lymphocytes: lymphocyte activation and anti-HIV activity in vitro. 180 85

Three lines of transgenic mice carrying the human immunodeficiency virus type 1 (HIV-1) long terminal repeat fused to the simian virus 40 early region (HIV-1 Tag) were constructed. Expression of the transgenes was reproducibly observed in the lymphoid tissue and skin of all three transgenic lines studied. Interestingly, cell types other than T cells, i.e., B cells and thymic stromal cells, contributed most of the expression detectable in the lymphoid organs. Each transgenic line also displayed a different but consistent pattern of transgene expression in nonlymphoid organs. These individual patterns probably reflect the effects of particular chromosomal integration sites on transcriptional activity of the HIV-1 promoter.
 ...
PMID:Expression of a human immunodeficiency virus type 1 long terminal repeat/simian virus 40 early region fusion gene in transgenic mice. 184 96

An in-situ assay for monitoring regulated gene expression in continuously growing mammalian cells is described. This technique can be used for the detection of the transactivator (Tat) protein in human immunodeficiency virus(HIV)-infected cells. Human kidney cells 293, harboring the luc gene, and fused to the HIV-1 long terminal repeat, were isolated and served as tester cells. Tat is supplied by transfection with a tat-carrying plasmid, or alternatively by addition of Tat-containing cell extracts, made from virus-infected or plasmid-transfected cells. Light emitted from the tester cells is recorded on film continuously, or by a photo sensor. Transactivation by HIV Tat results in a pronounced increase in light emission from the tester cells (up to 3000-fold). This assay, which detects HIV-specific gene products, may be used as a diagnostic tool for the detection of active HIV present in peripheral blood.
 ...
PMID:A bioluminescence assay for gene expression by continuously growing mammalian cells: application for detection of human immunodeficiency virus type 1 (HIV-1). 191 86

We have isolated a rat cDNA, named FE65, hybridizing to an mRNA of about 2,300 nucleotides present in rat brain, undetectable in rat liver and very poorly represented in other tissues. An mRNA of the same size is present in human neuroblastoma cells and is absent from other human cell lines. The FE65 cDNA contains an open reading frame (ORF) coding for a polypeptide of 499 amino acids in which 143 residues can be aligned with the DNA binding domain of the integrases encoded by mammalian immunodeficiency viruses. The remaining part of the FE65 ORF is not homologous with the correspondent regions of the integrases; the first 206 residues of the FE65 ORF show numerous negative charges and a short sequence not dispensable for the function of the transactivating acidic domain of the jun family transcriptional factors. A plasmid which expresses FE65 amino acids 1-232 fused to the yeast GAL4 DNA binding domain was co-transfected with a plasmid containing five GAL4 binding sites upstream of a minimal Adenovirus promoter controlling the expression of the CAT gene. This experiment showed that the fused protein GAL4-FE65 is able to obtain a 30-40 fold increase of the CAT gene expression compared to the expression observed in the presence of the GAL4 DNA binding domain alone. Two types of FE65 mRNA are present in rat brain, differing only for six nucleotides. We demonstrate that this is the consequence of a neuron-specific alternative splicing of a six-nucleotide miniexon, which is also present in the human genome, in an intron/exon context very similar to that of the rat FE65 gene.
 ...
PMID:A rat brain mRNA encoding a transcriptional activator homologous to the DNA binding domain of retroviral integrases. 192 10

The mechanisms determining the ability of some but not other strains of human immunodeficiency virus type 1 (HIV-1) to grow in peripheral blood monocyte-macrophages are presently unclear. The tat gene of HIV-1-IIIB which replicates poorly in human macrophages, and the tat gene of HIV-1-BaL, which replicates to high titers in the same cells in transient expression systems with their respective long terminal repeats (LTR) driving a reporter chloramphenicol acetyl transferase (CAT) gene were compared. The authors hypothesized that the tat gene and LTR of BaL might help account for its efficient growth in primary monocyte-macrophages by virtue of a high activity in these cells relative to that of the IIIB tat and LTR. Primary peripheral blood lymphocytes and monocytes were cotransfected with either the HIV-1BaL or HIV-1-IIIB LTR fused to the CAT gene and their respective tat genes. The IIIB tat and LTR were at least as active in primary lymphocytes as the BaL combination, and both tat-LTR pairs were more active in primary lymphocytes than monocytes. The same relative activities were also observed in primary monocytes after in vitro maturation to macrophages prior to transfection. These data strongly suggest that neither the tat gene nor the LTR of HIV-1-IIIB and HIV-1BaL can account for the great ability of the latter or the inability of the former to grow in monocyte-macrophages.
 ...
PMID:Relative activities of HIV-1-IIIB and HIV-1BaL LTR and tat in primary monocytes and lymphocytes. 193 Dec 36

The Tat protein of the human immunodeficiency virus type 1 (HIV-1) is required for efficient viral gene expression. By means of mutational analyses, several domains of the Tat protein that are required for complete activation of HIV-1 gene expression have been defined. These include an amino-terminal activating domain, a cysteine-rich dimerization domain, and a basic domain important in the binding of Tat to the trans-activation response element (TAR) and in Tat nuclear localization. Recently, we described a mutation, known as delta tat, which resulted in a protein with a truncated basic domain. This protein had a "trans-dominant" phenotype in that it inhibited wild-type Tat activation of the HIV-1 LTR. To further characterize the requirements for generating a Tat trans-dominant phenotype, we constructed a variety of Tat proteins with truncations or substitutions in the basic domain. A number of these proteins showed a trans-dominant phenotype. These Tat mutants also inhibited activation of the HIV-1 LTR by a protein composed of Tat fused to the prokaryotic R17 (phage MS2) RNA-binding protein in which the R17 recognition element was inserted in the HIV-1 LTR in place of TAR. Thus, an intact TAR element was not required for this inhibition. We also studied the cellular localization of Tat and a trans-dominant Tat mutant by means of immunofluorescence staining with the use of antibodies reactive to different domains of the Tat protein. The results indicated that Tat becomes localized predominantly in the nucleus both in the presence and absence of the trans-dominant Tat construct, suggesting that the trans-dominant mutant does not inhibit Tat nuclear localization. These studies further define the requirements for the creation of trans-dominant Tat mutants, and suggest that the mechanism of trans-dominant Tat inhibition may be either the formation of an inactive complex between wild-type and mutant Tat or sequestration of cellular factors involved in regulating HIV-1 gene expression.
 ...
PMID:Trans-dominant Tat mutants with alterations in the basic domain inhibit HIV-1 gene expression. 193 22

We have reported previously the enhancement of the infectivity of human immunodeficiency virus type 1 (HIV-1) by liposomes composed of the cationic lipid N-[2,3-(dioleyloxy) propyl]-N,N,N-trimethylammonium chloride (DOTMA). To determine the mechanism by which this process occurs, we have investigated the role of CD4, serum concentration and liposome-cell interactions in the DOTMA-mediated stimulation of HIV-1 infection of A3.01 cells. Serum alone significantly inhibited the binding and infectivity of HIV-1, but DOTMA-mediated enhancement of infectivity was more pronounced in the presence of serum than in its absence. HIV-1 binding to cells was increased in the presence of DOTMA liposomes, DEAE-dextran and polybrene, all of which also enhanced infectivity to a similar extent at comparable concentrations. Fluorescence dequenching measurements indicated that DOTMA liposomes fused with HIV-1, but not with cell membranes, in the presence of serum. The enhancing effect of DOTMA liposomes on HIV-1 infectivity was CD4-dependent, and appeared to involve virus-liposome fusion and liposome binding to the cell surface. DOTMA liposomes did not mediate infection of the CD4-K562 and Raji cell lines.
 ...
PMID:Enhancement of human immunodeficiency virus type 1 infection by cationic liposomes: the role of CD4, serum and liposome-cell interactions. 194 Aug 66

For the purpose to establish the system to express foreign antigen from Mycobacterium bovis BCG. We have cloned, sequenced and expressed genes for secreting proteins, alpha antigen, MPB64, MPB57 and MPB70 from M. bovis BCG. The upstreams and structural genes were characterized. The gene for alpha antigen of Mycobacterium kansasii was also characterized. The gene for alpha antigen of M. kansasii (k-alpha) was chosen for the further study at first. This gene was fused with shuttle plasmid PIJ666-PAL5000 obtained from T. Kisser and transfected to M. bovis BCG (Tokyo). Transformant was obtained by a selection with kanamycin. It was able to secrete k-alpha antigen. DNA-containing a B-cell epitope (Glu-12-Leu-Asp-Arg-Trp-Glu-Lys-Ile-19) of human immunodeficiency virus type 1 P17 gag was fused to this vector at C terminal of k-alpha. Using this vector, we have succeeded to express foreign antigen in M. bovis BCG. The products were analyzed in one or two dimensional electro-phoresis. The results thus obtained will be reported elsewhere.
 ...
PMID:[Study on recombinant BCG]. 194 33


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>