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

Human T cells can express MHC-class II products and were shown to be potential antigen-presenting cells. However, they are unable to capture the antigen and only antigens, which bind to T cell membranes such as the gp120 glycoprotein of HIV, are internalized, processed, and presented by T cells. To better understand the role of T cells as antigen-presenting cells, we established a method which overcomes the lack of antigen capture by T cells. Antigen (tetanus toxoid, TT) or an antigenic peptide of TT (residue 830-843, P2) was coupled to antibodies directed to T cell surface molecules such as CD2, CD4, CD8. Antibody/TT and antibody/P2 constructs stimulated P2-specific T cell clones in the absence of accessory cells, if the antibody recognized a T cell surface structure. Compared to the peptide alone, a 100-500 times lower molar concentration of the antibody/peptide construct was required to achieve a similar proliferative response. T cell stimulation via the constructs involved intracellular processing, as nonspecific, glutaraldehyde fixed T cell lines pulsed with the constructs could present the peptide and processing inhibitors like Leupeptin or Chloroquine inhibited the development of a proliferative response to the constructs. Our data underline the ability of T cells to function as antigen-processing and -presenting cells and show that antibody/antigen or antibody/peptide constructs are able to direct a certain antigen or peptide to a T cell. Antibody/peptide constructs may be interesting tools to better understand antigen processing and to study the consequences of antigen presentation by different cells.
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PMID:Use of antibody/peptide constructs of direct antigenic peptides to T cells: evidence for T cell processing and presentation. 172 68

Several domains of the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein have been identified that are involved in HIV-1-mediated membrane fusion. One domain that is involved in membrane fusion is the hydrophobic amino terminus of the HIV-1 transmembrane glycoprotein gp41. Here we show that a polar substitution at gp41 amino acid 2 (the 41.2 mutation) results in an envelope glycoprotein that dominantly interferes with both syncytium formation and infection mediated by the wild-type HIV-1 envelope glycoprotein. The interference by the 41.2 mutant is not a result of aberrant envelope glycoprotein synthesis, processing, or transport. The 41.2 mutant elicits a dominant interfering effect even in the presence of excess wild-type glycoprotein, suggesting that a higher-order envelope glycoprotein complex is involved in membrane fusion. These results shed light on the process by which the HIV-1 envelope glycoproteins induce membrane fusion reactions and present a possible approach to anti-HIV therapy.
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PMID:A mutation in the human immunodeficiency virus type 1 transmembrane glycoprotein gp41 dominantly interferes with fusion and infectivity. 172 20

Utilizing a recombinant vaccinia expression system, we investigated the biological properties and CD4 receptor interactions of the envelope glycoproteins of a noncytopathic human immunodeficiency virus type 2 strain, termed HIV-2/ST, and a highly cytopathic variant derived from it. The efficiency and host cell range of syncytium formation by the recombinant glycoproteins of both viruses were highly restricted compared to those of prototypic strains of HIV (HIV-2/ROD or HIV-1/IIIB). However, the glycoprotein of cytopathic but not wild-type ST generated numerous large syncytia in the human T-cell line Sup T1 from which it was derived. A single cell line (Molt 4 clone 8) was permissive to fusion by both wild-type and cytopathic ST envelopes, but only the glycoprotein of cytopathic ST could be inhibited with a soluble form of the viral receptor CD4 (sCD4). While these results indicated major differences in the envelope glycoprotein-CD4 receptor interactions of wild-type versus cytopathic ST, direct and competition binding assays utilizing soluble external glycoprotein (SU) and sCD4 surprisingly revealed equivalent low binding affinity for both viruses. From these experiments we conclude that relevant biological properties (e.g., CD4 binding, cytopathic potential, and sCD4 neutralization) of HIV viruses which differ in their pathogenic potential are reflected in the sCD4 interactions of the assembled native envelope complex (as on cell or virion surfaces) but not the soluble SU glycoprotein.
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PMID:Human immunodeficiency virus type 2 envelope glycoprotein: differential CD4 interactions of soluble gp120 versus the assembled envelope complex. 173 26

The aim of this study was to determine whether mannosyl-specific lectins, especially Concanavalin A (ConA), may bridge HIV-1 env glycoproteins to cell membranes to increase virus binding to its targets, and to what extent this lectin-carbohydrate interaction can modify HIV-1 infectivity for monocytic compared with lymphoid cells. Monocytic U937 and lymphoid CEM cells, which both express surface mannose, were utilized. Whether first incubated with env glycoprotein or with the cells, lectins bound both to the cells and to radiolabeled recombinant gp160 (rgp160). Thus, they enhanced rgp160 adsorption to the cells in a methyl-alpha-mannose inhibitable manner. ConA did not appear to bind to the V1 domain of CD4 at the U937 cell surface since Leu3a binding was not blocked in the presence of ConA, nor was recombinant CD4 retained on a ConA-agarose affinity matrix. Moreover, enhanced rgp160 binding to the cells was CD4 independent, since it was not modified by preincubating the cells with Leu3a. Finally, ConA did not inhibit the binding of CD4-IgG3 chimeric molecules to virions immobilized on nitrocellulose membrane, which argues against the possibility that it interferes with the interaction of gp120 and CD4. However, both when incubated with the virus or with the cells and despite mediating enhanced binding of env glycoprotein, ConA neutralized HIV-1 infectivity for monocytic U937 as well as for lymphoid CEM cells. In this respect, ConA behaves like neutralizing antibodies which do not interfere with CD4 binding of gp120 but rather with some later event that leads to virus entry. These findings obtained with plant lectins may be of relevance in vivo, inasmuch as endogenous mannosyl-binding proteins, which are known to function as opsonins, have been reported to inhibit in vitro infection by HIV-1.
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PMID:Lectin-carbohydrate interactions and infectivity of human immunodeficiency virus type 1 (HIV-1). 173 38

The carboxyl half of the HIV-1 gp120 glycoprotein, which has been implicated in binding to the CD4 receptor, contains two disulfide bonds linking cysteine residues 378-445 and 385-418. To examine the necessity of these disulfide bonds for the formation and/or maintenance of a gp120 glycoprotein competent for CD4 binding, we created mutants of a soluble form of gp120 in which combinations of these cysteine residues were altered. The mutant glycoproteins were examined for export from the expressing cell and for CD4 binding ability. Mutant gp120 molecules lacking both disulfide bonds were not stably expressed or exported. However, mutants for which either disulfide bond could form were exported and were fully competent for CD4 binding. In some cases, the presence of one of the pair of linked cysteines exerted more detrimental effects on export or CD4 binding than did alteration of both cysteines. Thus, the evaluation or the contribution of a particular disulfide bond to a phenotype should include studies in which both cysteines involved in the bond are simultaneously altered.
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PMID:Contribution of disulfide bonds in the carboxyl terminus of the human immunodeficiency virus type I gp120 glycoprotein to CD4 binding. 173 91

It was postulated that similar genetic elements that are 'hot spots' for genetic variation might exist in both the HIV-1 and the human genome. To test this possibility a short repeated sequence from a region of variability in the HIV-1 glycoprotein (env) gene was amplified and used as a probe for blot hybridization with human genome DNA. Human genomic regions were hybridized and characterized by a set of polymorphic restriction DNA fragments. The pattern of the restriction fragments was individual specific. Thus a DNA probe from the HIV-1 env gene can serve as a genetic marker for hybridization with human genome regions and for the identification of individuals.
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PMID:Individual-specific patterns of human variable genomic regions detected by a DNA probe from the HIV-1 env gene. 175 67

Acquired immune deficiency syndrome (AIDS) is caused by infection with the human immunodeficiency virus (HIV), a human retrovirus. The virus infects cells of the immune system by attachment of a glycoprotein viral envelope (gp 120) to a molecule expressed on human helper T cells called CD4. The fusion of the virus envelope protein to its specific receptor allows HIV to penetrate the T cell. Once inside the cell viral RNA is transcribed into double-stranded DNA by an enzyme unique to retroviruses, reverse transcriptase. The double-stranded, proviral DNA travels to the nucleus of the cell and is integrated into the infected cell's chromosomal DNA where it may remain latent for years. As a result of triggers that are poorly understood, viral replication becomes activated and proviral DNA is transcribed back into genomic RNA and RNA that is translated into viral proteins, both of which are packaged and bud from the infected T cell as infectious virus. The viral life cycle orchestrates the natural history of clinical HIV infection. Three to four weeks following exposure to HIV there is a phase of rapid viral replication, high levels of plasma viremia, and development of a "flue like" illness. Four to six weeks after exposure, during this stage of acute infection, antibodies to HIV core (p24) and envelope (gp 160, gp 120, gp41) proteins appear. Six to eight weeks after exposure symptoms disappear and plasma viremia subsides, presumably due to clearance by the immune system.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Pathogenesis and natural history of HIV infection. 175 33

A protein profile has been monitored during human immunodeficiency virus (HIV) infection. The investigation concerned 60 patients suffering from acquired immunodeficiency syndrome (AIDS), 24 asymptomatic HIV-antibody seropositive subjects and 22 healthy HIV-antibody seronegative, individuals voluntary blood donors. Data show that retinol-binding protein, thyroxin-binding prealbumin and beta 2-microglobulin are already modified in HIV infection (p less than 0.05) whereas the other protein alteration becomes apparent during AIDS. These studies demonstrate that severe, but progressive malnutrition occurs in patients with AIDS. On the other hand nutritional abnormalities can be shown to have a deleterious effect upon the disease course as revealed by increasing alpha-1-acid glycoprotein and C-reactive protein levels for 60 to 70% of patients.
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PMID:[Inflammatory reaction markers and nutritional markers in HIV infection]. 177 13

Western blot (WB) analysis of various strains of HIV-2 indicated that transmembrane glycoprotein (TMP) of HIV-2 exists as trimers. These trimers have molecular weights and electrophoretic mobilities in the region of the major external glycoprotein, gp120, resulting in WB misidentification during diagnosis. A simple and rapid procedure was developed using trichloroacetic acid (TCA) to efficiently dissociate oligomeric forms of the TMP to monomers prior to the preparation of WB. This procedure permitted the unambiguous identification of antibodies to gp120 and to the TMP. Use of HIV-2 WB strips without any oligomeric forms of the TMP demonstrated (1) that cross reactivity of HIV-1-positive specimens on HIV-2 WB was mainly directed to Gag and Pol proteins, with some reactivity to gp36/gp41 TMP, but none to gp120; (2) that these strips can substantially reduce the number of specimens falsely identified as dually (HIV-1 and HIV-2) reactive; and (3) that HIV-2-positive specimens reacted to viral gp120 in a strain-specific manner, demonstrating high antigenic variation in this glycoprotein. It is recommended that this general procedure of viral protein dissociation be used for HIV-2 WB preparation.
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PMID:Oligomeric nature of transmembrane glycoproteins of HIV-2: procedures for their efficient dissociation and preparation of Western blots for diagnosis. 177 59

The envelope (env) glycoprotein of human immunodeficiency virus 1 (HIV-1), initially synthesized as a precursor molecule termed gp160, is cleaved into two noncovalently associated subunits prior to delivery to the plasma membrane. We have studied the oligomeric structure of this protein using chemical cross-linking, velocity gradient sedimentation, and SDS-resistance. We find that gp160 forms stable homodimers after synthesis. After cleavage to gp120/gp41 the molecule becomes less stable to detergent solubilization and centrifugation but remains dimeric. Interactions between the 129 amino terminal residues in the ectodomains of adjoining gp41 subunits are both sufficient and necessary for assembly. In addition, tetramers composed of two dimers were also formed. Larger structures were not observed. The tetrameric paramyxovirus F protein, which has structural and functional similarities to the HIV-1 env protein, also forms a dimer of dimers.
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PMID:The assembly of the HIV-1 env glycoprotein into dimers and tetramers. 178 45


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