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: UMLS:C0021051 (immunodeficiency)
71,517 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A large-scale immunoaffinity (IA) purification process was developed for the isolation of recombinant soluble antigen CD4 (sCD4) from Escherichia coli fermentations. The monoclonal antibody used for IA purification of sCD4 recognized a conformation-dependent epitope on the surface of domain 1 of CD4. IA chromatography was used to purify both sCD4-183, consisting of the N-terminal 183 amino acids of human CD4, and sCD4-PE40, a fusion protein consisting of the N-terminal 178 amino acids of CD4 and amino acids 1-3 and 253-613 of Pseudomonas exotoxin A (PE40). sCD4-183 was purified from E. coli cell pellets using cell disruption, protein solubilization, oxidation, Q-Sepharose anion-exchange and IA chromatography steps. sCD4-PE40 was purified from cell pellets using cell disruption, protein solubilization, oxidation, Cu(2+)-immobilized metal-affinity chromatography, anion-exchange and IA chromatography steps. The IA-purified sCD4 analogues demonstrated the correct apparent molecular masses on SDS/PAGE. The immobilized monoclonal antibody appeared to select for correctly folded CD4 protein, since sCD4-183 and sCD4-PE40 purified by the IA method bound human-immunodeficiency-virus glycoprotein gp120 (HIV gp120) in vitro. sCD4-PE40 purified by IA chromatography also inhibited protein synthesis in CV-1 cells expressing HIV gp120/160 at the cell surface. Relatively high recoveries of sCD4-183 and sCD4-PE40 were observed in the IA step of the purification process (71 and 79% recovery respectively). The results demonstrate that immobilized monoclonal antibodies directed against conformational epitopes may be used for rapid purification of gram amounts of correctly folded protein from mixtures of oxidized E. coli proteins.
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PMID:Large-scale immunoaffinity purification of recombinant soluble human antigen CD4 from Escherichia coli cells. 829 11

HCN-1A is a human cerebral cortical neuronal cell line having properties consistent with cells of immature neuronal origin. This article details evidence for productive low-level infection of HCN-1A cells with human immunodeficiency virus type 1 (HIV-1). In vitro exposure to HCN-1A monolayers to a high titer of either LAV/HTLV-IIIB or HTLV-IIIMN resulted in HIV-1 p24 antigen production and a moderate increase in reverse transcriptase activity in cell-free supernatants. The cells in both LAV/HTLV-IIIB- and HTLV-IIIMN-infected cultures were passaged and proliferated as long as 5 weeks while continuing to express low levels of viral antigen. Virus-positive cells were detected by indirect immunofluorescence, using serum from an individual with acquired immune deficiency syndrome (AIDS) as well as with a gp120 monoclonal antibody. Confirmation of HCN-1A infection was provided by polymerase chain reaction analyses of both nuclear and cytoplasmic DNA and by de novo synthesis of viral proteins as shown by metabolic labeling and immunoprecipitation. Virus in cell-free supernatants from infected HCN-1A cultures was passaged to a permissive human T cell line (A3.01). HCN-1A cells had no detectable surface CD4 protein or CD4 message. However, the cells expressed the membrane glycolipids, galactocerebroside and sulfatide, possible receptors for gp120 on cells of neuronal origin. Undifferentiated HCN-1A cells provide an in vitro model for investigating potential interactions of HIV-1 with a homogeneous population of immature cortical neurons.
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PMID:Human cortical neuronal cell line: a model for HIV-1 infection in an immature neuronal system. 831 71

Characteristics of human immunodeficiency virus (HIV) strains and the host immune response against the virus are major determinants in the pathogenesis of AIDS. HIV isolates can be distinguished by their ability to infect and replicate to high titers in cells, to kill those cells, and to down-modulate the CD4 protein on the cell surface. In addition, their sensitivity to serum neutralization or enhancement of infection can be appreciated. The genetic sequences associated with these biologic and serologic properties have been localized and could eventually be helpful for antiviral therapy. These variations in properties of HIV strains appear to correlate with induction of neurologic and gastrointestinal disease by certain strains. In some cases, HIV can establish a silent, latent infection. The mechanisms involved are not well defined, but one concept involves the nef gene, which with some strains, can suppress virus replication. An important finding is that viruses recovered from individuals as they advance to disease have many properties in vitro of presumed virulence in the host, such as a wide cellular host range, cytopathicity, and resistance to the antiviral effect of Nef. The host immune response can control virus spread through antiviral antibodies or cellular immune responses. Neutralizing antibodies are not commonly found in infected individuals, suggesting that viruses "escape" this immune response. Instead, in some symptomatic patients, antibodies that enhance virus infection can be detected. The difference in sensitivity of a virus appears related to its envelope proteins. Cellular immune responses offer some promise in maintaining or eliminating virus infection.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Features of human immunodeficiency virus infection and disease. 843 77

Considerable effort is being made to design anti-viral drugs for the human immunodeficiency virus type 1 (HIV-1) infection process. Some of this work has focused on CD4 protein, the HIV-1 receptor on T helper lymphocytes. One drug that binds to CD4 protein and inhibits both viral infection and growth is DIDS (4,4'-diisothiocyanato-2,2'-stilbenedisulfonate). DIDS is best known for its ability to inhibit erythrocyte band 3 anion exchange. Although the antiviral potency of DIDS is evident in vitro (IC50 approximately 30 microM), intravenous administration of DIDS should not be effective owing to the large number of band 3 molecules present on the red blood cell membrane (approximately 10(6)/cell), and to the very small Kd for DIDS binding to band 3 (approximately 30 nM). Therefore, we sought to identify other anion transport inhibitors that would bind weakly to band 3, but tightly to CD4 protein, and that could be administered to humans without significant toxic side effects. On the basis of our previous work with band 3 (Salhany, J. M., Rauenbuehler, P. B., and Sloan, R. L. (1987) J. Biol. Chem. 262, 15965-15973), we elected to study the binding of pyridoxal 5'-phosphate (PLP) to soluble CD4 protein. We have discovered that PLP binds surprisingly tightly to soluble CD4 protein (Kd = 45 microM), with a stoichiometry of about 1 mol of PLP/mol of protein. Furthermore, PLP binding was found to be competitive with DIDS for its binding site on soluble CD4 protein. These results suggest that PLP may be an effective anti-viral agent for the HIV-1 infection process.
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PMID:Pyridoxal 5'-phosphate binds specifically to soluble CD4 protein, the HIV-1 receptor. Implications for AIDS therapy. 846 94

A retroviral vector was constructed in which a gene encoding a mutated soluble CD4 protein that is retained in the endoplasmic reticulum (sCD4-KDEL) is expressed under control of human immunodeficiency virus type 1 (HIV-1) regulatory elements. HIV-1 infection of a human T-cell line transduced with this vector led to induction of sCD4-KDEL synthesis and a block in transport of the HIV envelope protein to the cell surface. There was a complete block to maturation of infectious HIV-1 in the transduced cells, no viral spread, and little or no syncytium formation. Infected cells gradually disappeared from the culture over a period of 2 months. This intracellular trap for HIV has potential application in gene therapy for AIDS.
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PMID:Blockade of human immunodeficiency virus type 1 production in CD4+ T cells by an intracellular CD4 expressed under control of the viral long terminal repeat. 846 77

The gastrointestinal tract plays a major role in the pathogenesis and pathophysiology of infection by the type 1 human immunodeficiency virus (HIV-1). It is a potential route for viral entry and it is the site of a number of complications, including both opportunistic infections and a primary HIV-induced enteropathy. Correspondingly, both in vivo and in vitro studies have demonstrated HIV infection of gastrointestinal cells of lymphoid and epithelial origin. HT-29, a human colonic epithelial cell line that is infectable with many HIV-1 strains, does not express CD4 protein or mRNA. Recent studies showed that antibodies recognizing a neutral glycolipid related to galactosylceramide (GalCer) in HT-29 cells inhibited HIV-1 infection of this cell line, extending previous findings in neural cells. In the current studies, we further analyzed the neutral glycolipids of HT-29 cells and showed that they contained authentic GalCer and that recombinant gp120 bound to this glycolipid. Moreover, by analyzing GalCer expression in clones derived from HT-29 and Caco-2 (another human colonic cell line), we observed that the level of expression of this glycolipid was associated with the sensitivity to HIV-1 infection. Subclones of Caco-2 did not express GalCer and were not infectable with any of three HIV-1 strains. These results strengthen the possibility that GalCer is an alternative receptor in CD4- cell lines. Furthermore, since GalCer is a major glycolipid in epithelial cells of the small intestine and colon, these results provide a structural basis for the binding of HIV-1 by gastrointestinal epithelial cells and the entry of the virus into those cells.
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PMID:Infection of colonic epithelial cell lines by type 1 human immunodeficiency virus is associated with cell surface expression of galactosylceramide, a potential alternative gp120 receptor. 846 78

Coinfections of human immunodeficiency virus (HIV), EBV, and HTLV or sperm proteins act synergistically to enhance infectivity and replication and expand cellular tropism. While some aspects of these synergisms are understood, others are not. We have found that membrane or surface proteins of CMV, HTLV, EBV and sperm proteins share large regions of similarity with the CD4 protein of T-helper lymphocytes. Since HIV uses CD4 as a receptor, it may bind to CD4 homologues on CMV, HTLV, EBV or sperm proteins. HIV could then "piggyback" with these viruses into cells with which it normally has no tropism. Similarly, HIV may expand the cellular tropism of CMV, or EBV. Such a piggyback mechanism may provide insight into the formation or presentation of CD4-like antigens from CMV, HTLV, EBV and sperm proteins with class II MHC-like antigens on HIV (gp160 and Nef proteins) and may break immunological tolerance, inducing the autoimmunity observed against both CD4+ and class II MHC+ T cells in AIDS patients.
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PMID:Does HIV "piggyback" on CD4-like surface proteins of sperm, viruses, and bacteria? Implications for co-transmission, cellular tropism and the induction of autoimmunity in AIDS. 847 53

The gene for the human CD4 glycoprotein, which serves as the receptor for human immunodeficiency virus type 1, along with approximately 23 kb of sequence upstream of the translational start site, was cloned. The ability of 5' flanking sequences to direct tissue-specific expression was tested in cell culture and in transgenic mice. A 5' flanking region of 6 kb was able to direct transcription of the CD4 gene in NIH 3T3 cells but did not result in detectable expression in the murine T-cell line EL4 or in four lines of transgenic mice. A larger 5' flanking region of approximately 23 kb directed high-level CD4 transcription in the murine T-cell line EL4 and in three independent lines of transgenic mice. Human CD4 expression in all tissues analyzed was tightly correlated with murine CD4 expression; the highest levels of human CD4 RNA expression were found in the thymus and spleen, with relatively low levels detected in other tissues. Expression of human CD4 protein in peripheral blood mononuclear cells was examined by flow cytometry in these transgenic animals and found to be restricted to the murine CD4+ subset of lymphocytes. Human CD4 protein, detected with an anti-human CD4 monoclonal antibody, was present on the surface of 45 to 50% of the peripheral blood mononuclear cells from all transgenic lines.
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PMID:Tissue-specific expression of human CD4 in transgenic mice. 847 53

Although the Nef proteins encoded by human immunodeficiency virus type 1 (HIV-1) and simian immuno-deficiency virus (SIV) are known to induce the efficient internalization and degradation of cell surface CD4, it remains unclear whether this process involves a direct interaction between Nef and CD4. Here, we report that CD4 downregulation by HIV-1 and SIV Nef requires distinct but overlapping target sites within the CD4 intracytoplasmic domain. In particular, mutation of a glutamic acid residue located at CD4 residue 405 or of arginine and methionine residues located, respectively, at residue 406 and 407 results in a mutant CD4 protein that is efficiently downregulated by HIV-1 Nef but refractory to downregulation by SIV Nef. However, both HIV-1 and SIV Nef require an isoleucine located at residue 410 and the dileucine motif found at CD4 residues 413 and 414. CD4 downregulation induced by the Nef protein encoded by HIV-2 is shown to require a CD4 target sequence that is similar to, but distinct from, that observed with SIV Nef. These data explain the previous finding that the murine CD4 protein, which has an alanine at residue 405, is refractory to downregulation by SIV, but not HIV-1, Nef (J. L. Foster, S.J. Anderson, A. L. B. Frazier, and J. V. Garcia, Virology 201:373-379, 1994). In addition, these observations provide strong genetic support for the hypothesis that the Nef-mediated downregulation of cell surface CD4 requires a direct Nef-CD4 interaction.
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PMID:Human immunodeficiency virus types 1 and 2 and simian immunodeficiency virus Nef use distinct but overlapping target sites for downregulation of cell surface CD4. 926 98

Entry of the type 1 human immunodeficiency virus into most cells requires the presence of the CD4 protein in combination with one of several recently described co-receptors. CXCR-4 (fusin) was the first identified, and it serves as co-receptor for T-cell-line tropic (T-tropic) HIV-1 isolates. To determine the expression of CXCR-4 in the brain, a major target of HIV pathology, we used immunohistochemistry and reverse transcriptase polymerase chain reaction with CXCR-4-specific antibodies and probes. We found that CXCR-4 was expressed in several cell types in brain, but notably in neurons and microglia, a finding that was replicated in tissue culture. The study of the expression of CXCR-4 in the brain, which may be one of many chemokine receptors in the central nervous system, may provide further insight into the interactions between brain cells, pathogens, and the immune system, and help understand the pathogenesis of HIV dementia.
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PMID:CXCR-4 (Fusin), a co-receptor for the type 1 human immunodeficiency virus (HIV-1), is expressed in the human brain in a variety of cell types, including microglia and neurons. 932 37


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