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Query: UMLS:C0001175 (AIDS)
 120,706 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A number of studies suggest a critical role of the HIV-1 envelope glycoprotein in cytopathogenesis, but the detailed mechanisms of cell injury remain to be defined. HIV-1 envelope proteins associate with the host cell membrane, and studies have demonstrated that HIV perturbs membrane structure and function. We describe here a structurally conserved region of the HIV-1 transmembrane protein (TM) that displays functional properties of target regions of proteins that interact directly with calcium-saturated calmodulin as part of cellular response cascades. The synthetic peptide homolog encompassing the carboxyl terminus (amino acid residues 828-855) of HIV-1 TM protein (LLP-1) is shown in standard in vitro assays to bind efficiently to purified calmodulin (CaM) and to inhibit in vitro CaM-mediated stimulation of phosphodiesterase activity. This suggests that this peptide homolog binds to CaM at affinities similar to those reported for a reference CaM-binding peptide. In addition, the CaM-dependent process of phospholipid synthesis can be inhibited in cell cultures by exogenous addition of the LLP-1. Finally, we have shown that the full-length TM protein binds CaM, whereas a truncated TM protein lacking the LLP-1 segment does not bind CaM. These results suggest a novel mechanism of viral cytopathogenesis mediated by the interaction of HIV-1 TM protein with cellular CaM, that could lead to an uncoupling of critical cellular signal transduction pathways.
AIDS Res Hum Retroviruses 1993 Nov
PMID:Identification of a calmodulin-binding and inhibitory peptide domain in the HIV-1 transmembrane glycoprotein. 831 49

Vesicles released from human E by Ca(2+)-loading, ATP-depletion, or storage are enriched in several glycosylphosphatidylinositol-anchored proteins such as acetylcholinesterase (AchE) and decay-accelerating factor (DAF). As a result of this, the remaining E are depleted of these proteins. We analyzed whether vesiculation induced by ATP-depletion in vitro was also responsible for a loss of C receptor 1 (CR1), which is a transmembrane protein arranged predominantly in small clusters. ATP-depleted E had lost 15.4% to 33.9% of their CR1. This loss was similar to that of AchE and DAF. The released vesicles contained CR1. The number of CR1 per band 3 protein was 1.7 to 2.7 that in the original E, indicating an enrichment of CR1 in vesicles. This enrichment was similar to that observed for AchE and DAF (1.83- and 2.6-fold, respectively). The capacity of the vesicles and the ATP-depleted E to bind C3b-coated immune complexes correlated with the CR1 number, suggesting that there was no preferential loss of CR1 clusters. Vesicles released from human E during C attack also contained CR1. In conclusion, in vitro aging induced by ATP-depletion is responsible not only for a loss of glycosylphosphatidylinositol-anchored proteins, but also of CR1. Whether vesiculation explains the loss of CR1 from aging E in vivo and from E of patients with SLE or AIDS remains to be studied.
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PMID:Release of vesicles enriched in complement receptor 1 from human erythrocytes. 832 33

A new human retrovirus, HIV-2, serologically distinct from human immunodeficiency virus type 1 (HIV-1), was first reported in 1985 and isolated in 1986 from 2 AIDS patients from Guinea-Bissau and Cape Verde Islands. Findings related to the characterization of HIV-2 antigenic and immunogenic sites that stimulate strain and type-cross-reactive immunity are illustrated; data from preliminary studies of simian immunodeficiency virus (SIV) are presented; and epidemiological and biological characteristics of HIV-2 infection are also reviewed. Prevention of HIV-2 and SIVsm infection has been achieved in cynomolgus macaques by passive transfer of an anti-SIVsm serum pool with high antibody titres. The identification of antibody-binding regions of HIV is critical for vaccine development studies. The presence of highly immunogenic domains in the extracellular proteins of HIV-2 has also been demonstrated by Western blot analysis using bacterially expressed contiguous segments representing the HIV-2 envelope products. Over 95% of HIV-2 positive sera from Senegal reacted with these protein segments. The antibody-reactive peptide scanning method defined 8 distinct antibody-binding sites in the transmembrane protein gp36 of the HIV-2 strain ROD in addition to the highly immuno-dominant site present at the amino terminus of gp36. Antibody reactions of SIVm-infected macaque sera against selected SIVm envelope peptides were very similar to those of HIV-2 and HIV-1-infected human sera to the corresponding linear antigenic sites, indicating the existence of immunological parallelism between human and simian lentiviruses. HIV-2-induced immunity in inoculated macaques has been shown to protect against SIV-associated disease, indicating that the 2 viruses share group-specific protective immunity. In a study of human sera, the occurrence of an intertype cross-reacting V3-region-specific activity correlated with the presence of cross-neutralizing activity in sera. These findings indicate that the V3 region may be an important neutralizing site not only in HIV-1 but also in HIV-2.
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PMID:Antigenic and immunogenic sites of HIV-2 glycoproteins. 845 54

Two cynomolgus macaques were infected with a genetically complex challenge stock of simian immunodeficiency virus (SIVmac251-32H). The polymerase chain reaction (PCR) was used to amplify the env gp41, rev, and nef overlapping coding sequences from provirus present in the blood of both animals at 1, 6, and 15 months post infection (p.i.). The predominant, env sequences found in both animals at the three time points were very similar to that found in the original 11/88 challenge stock. The functionally important hydrophobic fusion and membrane-spanning domains within gp41 remained conserved throughout the course of infection. Nucleotide variation within the region corresponding to the REV response element (RRE) was limited to four positions, none of which were predicted to cause any significant disruption to the secondary structure of the RRE. Very little genetic variation was observed in and around the cluster of potential glycosylation sites of the external portion of gp41. However, the existence of a previously assigned variable region elsewhere in the cytoplasmic domain of gp41 was confirmed. The three gene loci (env, rev, and nef) examined varied independently. All changes in the predominant protein sequences were brought about by single nucleotide substitutions only. After 15 months of infection with SIV, 1 animal was sick from SIV-induced disease whereas the other remained healthy. In-frame stop codons within the transmembrane protein occurred with a much greater frequency in the healthy animal.
AIDS Res Hum Retroviruses 1993 Feb
PMID:Simian immunodeficiency virus (mac 251-32H) transmembrane protein sequence remains conserved throughout the course of infection in macaques. 845 80

T-lymphocytes enter the brain in viral encephalitides. The monoclonal antibodies UCHL1 and Leu22 are widely used to identify these cells; however, both antibodies cross-react with peripheral blood monocytes, cells ontologically related to brain macrophages and microglia. This study examines the nature of UCHL1- and Leu22-positive cells in HIV-1 encephalitis, and investigates whether they carry the gp41 epitope of HIV-1. Formalin-fixed sections of brain from eight AIDS patients were double-stained using combinations of UCHL1 and Leu22 antibodies with the lectin Ricinus communis agglutinin (RCA), a lectin that binds to microglia, macrophages, and multinucleated giant cells (MNGC), or antibody to the gp41 transmembrane protein of HIV-1 and UCHL1. Some sections were also stained with the OPD4 antibody to helper/inducer T-cells. Small round cells were single-stained for UCHL1 and Leu22 in all cases. A few cells having morphologic characteristics of microglia, macrophages, and MNGC were observed using double stains employing UCHL1 or Leu22 and RCA, or UCHL1 or Leu22 and anti-gp41. Small round cells positive for both UCHL1 or Leu22 and gp41 could represent either macrophages or lymphocytes. The presence of small round cells positive only for UCHL1 or Leu22 in double-stained sections strongly suggests that T-cells are present in the brain in HIV encephalitis. Only a few of these cells were positive with OPD4 antibody for T-helper cells. Inability to demonstrate unequivocally HIV-1-infected T-cells suggests that microglia and macrophages, not T-cells, are the more important reservoirs of retrovirus in the brain.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Immunocytochemical identification of T-cells in HIV-1 encephalitis: implications for pathogenesis of CNS disease. 848 86

We selected HIV-1-LAI variants with the ability to induce syncytium formation of C8166 cells in the presence of a monoclonal antibody (MAb), 5A8, to domain 2 of CD4. Five biologically cloned variants with at least 60-fold greater resistance than wild type to 5A8-mediated inhibition of syncytium formation were obtained. The variants exhibited reduced relative sensitivity to inhibition of syncytium formation and virus infection, not only by the selecting anti-domain 2 MAb, but also by MAbs to domains 1 and 3 of CD4. By contrast, the sensitivity of these variants to neutralization by soluble CD4 and bivalent CD4-IgG was greater than for the parental clone. The affinities of soluble CD4 for Env protein, in either solubilized or membrane-anchored form, did not differ significantly between the variants and LAI. Analyses of sCD4-induced exposure of the transmembrane protein at 4 and 37 degrees C suggested, however, that the variants had acquired an increased susceptibility to the triggering of conformational changes in their Env oligomers at 37 degrees C. This may represent a mechanism of both the increased resistance to the CD4 MAbs and the enhanced sensitivity to soluble CD4.
AIDS Res Hum Retroviruses 1996 Jul 20
PMID:Altered CD4 interactions of HIV type 1 LAI variants selected for the capacity to induce membrane fusion in the presence of a monoclonal antibody to domain 2 of CD4. 882 17

CD4-expressing T cells in lymphoid organs are infected by the primary strains of HIV and represent one of the main sources of virus replication. Gene therapy strategies are being developed that allow the transfer of exogenous genes into CD4(+) T lymphocytes whose expression might prevent viral infection or replication. Insights into the mechanisms that govern virus entry into the target cells can be exploited for this purpose. Major determinants of the tropism of infection are the CD4 molecules on the surface of the target cells and the viral envelope glycoproteins at the viral surface. The best characterized and most widely used gene transfer vectors are derived from Moloney murine leukemia virus (MuLV). To generate MuLV-based retroviral gene transfer vector particles with specificity of infection for CD4-expressing cells, we attempted to produce viral pseudotypes, consisting of MuLV capsid particles and the surface (SU) and transmembrane (TM) envelope glycoproteins gp120-SU and gp41-TM of HIV type 1 (HIV-1). Full-length HIV-1 envelope glycoproteins were expressed in the MuLV env-negative packaging cell line TELCeB6. Formation of infectious pseudotype particles was not observed. However, using a truncated variant of the transmembrane protein, lacking sequences of the carboxyl-terminal cytoplasmic domain, pseudotyped retroviruses were generated. Removal of the carboxyl-terminal domain of the transmembrane envelope protein of HIV-1 was therefore absolutely required for the generation of the viral pseudotypes. The virus was shown to infect CD4-expressing cell lines, and infection was prevented by antisera specific for gp120-SU. This retroviral vector should prove useful for the study of HIV infection events mediated by HIV-1 envelope glycoproteins, and for the targeting of CD4(+) cells during gene therapy of AIDS.
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PMID:Pseudotyping of murine leukemia virus with the envelope glycoproteins of HIV generates a retroviral vector with specificity of infection for CD4-expressing cells. 923 30

The poor prognosis associated with patients afflicted with the acquired immunodeficiency syndrome and primary central nervous system lymphoma (AIDS-PCNSL) is due in part to the intrinsic resistance of this Epstein-Barr virus (EBV)-associated tumor to conventional antineoplastic therapy. Fas (CD95) is a transmembrane protein receptor that transmits an intracellular signal leading to rapid programmed cell death following ligation with its natural ligand or anti-Fas antibodies. Fas expression and function were assessed in AIDS-PCNSL biopsy samples and in EBV+ human B-cell tumors that spontaneously developed in severe combined immune deficient (SCID) mice engrafted with human lymphocytes (hu-PBL-SCID mice). All tumors samples showed high-density surface expression of Fas by flow cytometry or immunohistochemical staining. Cells from two AIDS-PCNSL biopsy samples that did not express pan B-cell markers did not express Fas antigen. All tumors examined were susceptible to Fas-mediated apoptosis, as measured by standard assays for endonucleolytic cleavage of DNA. The response to Fas-mediated apoptosis was dependent on log-fold increases in the concentration of immobilized anti-Fas antibody, but could also be induced with a mobilized anti-Fas antibody. No evidence for intrinsic resistance to Fas-mediated apoptosis (ie, secreted or truncated forms of Fas) could be shown. Radiation-induced apoptosis of neoplastic EBV+ B cells was enhanced by activation of Fas, and prolonged exposure to interleukin-2 increased both Fas expression and Fas-induced apoptosis. As the normal brain parenchyma appears to have either low-density or absent expression of Fas, and antineoplastic therapy can be selectively delivered to the CNS with little systemic toxicity, local delivery of Fas-activating molecules could prove to be a useful component in the multimodal treatment of AIDS-PCNSL.
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PMID:Phenotypic and functional analysis of Fas (CD95) expression in primary central nervous system lymphoma of patients with acquired immunodeficiency syndrome. 929 6

The cytoplasmic domain (CD) of the SIVmac transmembrane protein (TM) can affect viral infectivity by modulating several Env functions, notably fusogenic capacity and incorporation into virions. In addition, envelopes with a truncated CD are counterselected in primary cells in culture and in vivo in rhesus macaques, suggesting a role for this domain in viral persistence. Here, we have used mutagenesis to examine specific features of the SIVmac TM CD, including the conserved C-terminal alpha helix and the overall length of the CD. Several mutations dramatically reduced and/or delayed virus infectivity in lymphoid cell lines. Detailed analysis of mutants revealed defects in envelope stability, fusogenic capacity, and virion incorporation. The primary defect associated with an envelope containing a 64-residue CD was rapid degradation. A mutant Env lacking the C-terminal alpha helix but encoding an exceptionally long CD (373 residues) was highly fusogenic but inefficiently incorporated into virions. A third mutant, containing amino acid substitutions designed to alter the charge density of the C-terminal helix, retained cytopathic properties and showed enhanced fusogenic capacity but replicated with delayed kinetics. Taken together, these results demonstrate that CD sequence variation entails functional "tradeoffs" that can involve optimization of certain Env functions at the expense of others.
AIDS Res Hum Retroviruses 1998 Mar 20
PMID:Features of the SIVmac transmembrane glycoprotein cytoplasmic domain that are important for Env functions. 954 96

To investigate the protective efficacy of various gp130 vaccine preparations, rhesus monkeys were immunized with gp130 oligomers (O-gp130) or two different gp130-monomer preparations (M1-gp130; M2-gp130) and challenged with 50 MID50 of simian immunodeficiency virus (SIV)mac32H. Following challenge the control animals and all animals of the M1- and M2-gp130 group and 1 animal of the O-gp130 group were productively infected, whereas 3 animals of the O-gp130 group resisted the productive virus replication. The protection was correlated with high neutralizing antibodies and a long-lasting immune response to the transmembrane protein gp41. Whereas none of the O-gp130 animals had developed disease symptoms, 3 M1-gp130 animals, 1 M2-gp130 animal, and 2 control animals died as a result of AIDS within 18 months after challenge. Therefore, immunization with virion-derived gp130 oligomers of SIVmac32H can confer protection against the productive infection with SIVmac32H and suppress the development of the AIDS-like disease.
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PMID:Prechallenge high neutralizing antibodies and long-lasting immune reactivity to gp41 correlate with protection of rhesus monkeys against productive simian immunodeficiency virus infection or disease development. 985 57


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