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

Anti-idiotypic antibodies (Ab2) binding to the antigen-combining site of other antibodies may functionally and even structurally mimic antigen. Ab2 to antibodies directed against the lymphocyte CD4 receptor for human immunodeficiency virus type 1 (HIV-1) may mimic the receptor and therefore inhibit viral infectivity. We have produced Ab2 against monoclonal anti-CD4 receptor antibodies (Ab1). The Ab1 strongly inhibit HIV-1 binding to the receptor. Six monoclonal rat Ab2 and two polyclonal rabbit Ab2 were produced against the Ab1 MT151 and nine monoclonal Ab2 against the Ab1 OKT4A. These Ab2 bound only to Ab1 and not to a panel of nine unrelated murine monoclonal antibodies (MAbs). The Ab2 completely inhibited the binding of the homologous Ab1 to CD4-positive target cells, and recombinant soluble CD4 inhibited binding of Ab2 to Ab1. Thus, the Ab2 seemed to mimic the Ab1-binding site of the CD4 receptor, although the results of inhibition assays did not exclude steric hindrance of antibody-combining sites. However, none of the 17 Ab2 bound to gp120 of HIV-1 envelope or inhibited syncytia formation between cells infected and uninfected with HIV-1. These results suggest that the Ab2 do not mimic the HIV-1 binding site of the CD4 receptor. They further suggest that the Ab1 may not bind within the virus-binding site of the CD4 receptor.
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PMID:Anti-idiotypic antibodies against anti-CD4 antibodies MT151 and OKT4A. 172

The isolate HTLV-IIIB is used by a large number of investigators for a variety of studies. The data shown here emphasize the uniqueness of this isolate with respect to certain biological behaviors, in particular, the ability to infect cells other than T lymphocytes and mononuclear phagocytes, and the ability to infect chimpanzee T cells. Data also presented indicates that HTLV-IIIB has a greater binding affinity for the CD4 receptor molecule, which may help to explain its observed biological uniqueness. Caution in generalizing from findings based on studies with HTLV-IIIB alone is recommended. In addition, evidence demonstrating CD4-mediated entry of HIV-1 into normal human monocyte/macrophages is included.
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PMID:Virus-host cell interactions in human immunodeficiency virus infections. 172 68

We have investigated the susceptibility of cord blood monocyte-derived macrophages to human immunodeficiency virus type 1 (HIV-1) infection in vitro. Cord blood monocytes were maintained in vitro for 10 to 15 days and then infected with HIV-1. Syncytia were observed 14 days after infection by light microscopy. Viral proteins were detected by immunofluorescence assay. Electron microscopic examination demonstrated typical lentivirus particles within cytoplasmic vacuoles. The supernatants from the HIV-1-infected cultures also contained significant reverse transcriptase activity and p24 antigen. Like adult monocyte/macrophages, cord-derived monocyte/macrophages expressed the CD4 receptor molecule. Pretreatment with blocking antibody prior to infection with HIV-1 Bal significantly reduced or blocked infection of cord monocyte/macrophages. When cord and adult monocyte/macrophages were infected with HIV-1 Bal or Ada-M and directly compared, higher reverse transcriptase activities and p24 antigen expression were obtained with cord monocyte/macrophages. However, no significant difference was found between adult and cord monocyte/macrophages infected with HIV-1 IIIB. These observations suggest that cord monocyte-derived macrophages may be important in the pathogenesis of pediatric AIDS and that the increased susceptibility of cord monocyte/macrophages to HIV-1 infection in vitro may be relevant to the enhanced susceptibility of neonates to HIV-1 diseases in vivo.
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PMID:Infection of cord blood monocyte-derived macrophages with human immunodeficiency virus type 1. 172

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 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

Anti-CD4 antibody was found in 30% of human immunodeficiency virus (HIV-1)-seropositive thrombocytopenic patients compared with 5% of nonthrombocytopenic seropositive patients (chi 2 = 21.7, P less than 0.001) and was shown by the following observations to contain internal-image anti-idiotype antibody (Ab2) directed against the antibody (Ab1) to gp120, the HIV-1 envelope glycoprotein that binds to CD4: (i) affinity-purified anti-CD4 (Ab2) bound to affinity-purified anti-HIV-1gp120 (Ab1) on solid-phase radioimmunoassay, and binding could be blocked by recombinant CD4 (rCD4) as well as recombinant gp120 (rgp120); (ii) F(ab')2 fragments of Ab1 inhibited the binding of Ab2 to rCD4; (iii) Ab2 inhibited the binding of Ab1 to HIV-1 beads; (iv) Ab2 inhibited the binding of Ab1 to gp120 on immunoblot; (v) Ab2 bound to the CD4 receptor on a CD4-bearing T-cell line, H9; (vi) Ab3 (anti-rgp120) could be produced in vivo by immunizing mice with Ab2, and binding of Ab3 to rgp120 could be blocked with rCD4; and (vii) three different Ab2 preparations bound to two different homologous Ab1 preparations. Ab1 or Ab2 alone did not bind to platelets, whereas the idiotype-anti-idiotype complex did bind to platelets in a concentration-dependent manner. Binding of the internal-image complex was 10-fold greater than that of a non-internal-image Ab1-Ab2 complex composed of anti-HIV-1gp120 and anti-anti-HIV-1gp120. Thus, patients with HIV-1 thrombocytopenia contain internal-image idiotype-anti-idiotype complexes that could be affecting CD4 cell number or function, inhibiting HIV-1 binding to CD4 cells or contributing to HIV-1 thrombocytopenia.
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PMID:Internal-image anti-idiotype HIV-1gp120 antibody in human immunodeficiency virus 1 (HIV-1)-seropositive individuals with thrombocytopenia. 174 4

Infection of Human organism by Human Immunodeficiency viruses induces, after a shorter or a longer period, a complex immune Deficiency (ID) that has been named Acquired Immune Deficiency Syndrome (AIDS). Although the designation is not correct, it has been accepted by the scientific community. AIDS includes multiple clinical situations that have in common HIV infection and an almost constant ID, that at the end of natural course of infection manifestated by the presence of opportunistic infections and malignant tumors. HIV-1 and HIV-2 are slow RNA viruses with a common architecture and well known genomic organization. The characteristics that made HIV infectious agent n. 1 in XXth Century are their remarkable heterogeneity, close AA sequence homology between some of their proteins and relevant molecules in human beings: MHC molecules, IL-2, VIP, etc. and a strong affinity of gp 120 to CD4 receptor of T helper lymphocytes (T4), mononuclear phagocytes, natural killer cells, etc. all of them sharing a relevant role in normal immune response (IR). Affected in its cornerstones of cellular defense, human organism starts an immune defense through antibodies, cytotoxic T Lymphocytes (CTL) Natural Killer Cells (NK) antibody dependent cell cytotoxicity (ADCC), that fails. Activating immune system HIV turn that defense strategy to their own profit and enhanced replication. After an apparent latency period--in which the balance seems to favor the host--new viral variants arise due to high rate of HIV mutagenesis, that in turn stimulate immune system, induce new cycles of viral replication and new high virulent mutants, leading to the final collapse of Immune System.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Immunologic aspects of HIV infection]. 180 34

The role of placental cells in transplacental transmission of human immunodeficiency virus type 1 (HIV 1) was investigated. Placental macrophages and trophoblasts, which together represent the main cell components of the placenta, were cultivated separately and then compared to foetal monocyte-derived macrophages for susceptibility to HIV 1 infection. Placental macrophages treated with granulocyte-macrophage colony-stimulating factor (GM-CSF) were less easily infected with HIV 1 than were GM-CSF-treated foetal monocyte-derived macrophages. HIV 1 replication in cocultures consisting of infected placental macrophages together with a highly HIV 1-permissive cell line (CEM) was detected persistently for at least 6 weeks by reverse transcriptase assay, even though placental macrophages expressed no detectable CD4 receptor, as indicated by indirect immunofluorescence. HIV 1-specific DNA sequences were also detected in infected placental macrophages. Trophoblasts exhibited no detectable CD4 expression and did not support the replication of HIV 1, although low levels of HIV 1-specific DNA sequences could be detected in infected trophoblasts. Placental macrophages or trophoblasts (or both) may thus play an important role in transplacental HIV 1 transmission.
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PMID:Replication of human immunodeficiency virus type 1 in primary cultured placental cells. 189 50

The effect of recombinant protein from the envelope (gp120) of the HIV on B lymphocytes purified from either HIV-infected individuals or healthy seronegative controls was examined. B cells from peripheral blood and lymph nodes of HIV-infected individuals spontaneously secreted TNF-alpha; this secretion was augmented by the presence of gp120, whereas B cells from healthy seronegative donors failed to secrete significant levels of TNF-alpha in the presence or absence of gp120. In a coculture system of B cells and chronically HIV-infected T cells (ACH-2), where viral expression is largely mediated by TNF-alpha, gp120 increased virus expression only if the B cells were obtained from HIV-infected individuals. The effects of gp120 on viral expression in this system were not mediated via CD4 receptor binding or FcR binding of anti gp120-gp120 immune complexes. Besides its effect on cytokine production, gp120 also stimulated Ig secretion in B cells from HIV-infected individuals, but not from normal donors. Finally, it was demonstrated by in situ hybridization that germinal centers of lymph nodes from HIV-infected individuals contain large amounts of HIV RNA that is in close proximity to germinal center B cells. These findings suggest that the hyperplastic germinal centers of lymph nodes provide an unique environment for virus expression and accumulation where gp120 stimulates B cells to secrete HIV inductive cytokines, such as IL-6 and TNF-alpha, and thereby further enhances virus expression in infected cells in a paracrine manner.
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PMID:Recombinant gp120 specifically enhances tumor necrosis factor-alpha production and Ig secretion in B lymphocytes from HIV-infected individuals but not from seronegative donors. 191 99

The construction of recombinant proteins by genetic engineering has opened new avenues in basic research (studies on protein organization, protein folding, immunogenicity of proteins, ...) and many different applications. Recombinant proteins which keep properties of both parental proteins are especially interesting. For example, if one protein--the vector protein--is targeted to a given cellular compartment, the other protein--the passenger--may be identically targeted. Also, if the vector protein can be purified by a simple affinity chromatographic procedure, this property may be extended to the passenger. The authors have developed a genetic procedure to detect "permissive" sites within potential vector proteins so that genetic fusion to these sites keep most or all biological properties of the vector. When they used LamB, an outer membrane protein from E. coli, foreign sequences could be expressed at the bacterial cell surface. This may lead to several types of applications: live bacterial vaccines, simple diagnostic tests, selection procedures for peptides with biological activity. When they used the MalE protein, a periplasmic maltose binding protein from E. coli, the passengers could be exported and purified in one-step high affinity chromatography in mild non-denaturing conditions. This led us to a simple preparation and purification scheme for the soluble part of the CD4 receptor for the Human Immunodeficiency Virus (HIV).
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PMID:Bacterial vectors to target and/or purify polypeptides: their use in immunological studies. 192 41


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