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

Earlier findings indicate that peptides can affect the expression of major histocompatibility complex (MHC) class I molecules on the surface of cells with defective peptide loading mechanism. We have used peptide induced increase of class I antigen expression to assess peptide interaction with MHC class I molecules. A panel of 41 overlapping synthetic peptides derived from the human immunodeficiency virus-1 (HIV-1) gag protein and 33 nonoverlapping peptides from Epstein-Barr virus (EBV) proteins EBNA-1, 2, 3, 4, 5, 6, LMP, BZLF2, BILF2, BSLF2, BALF4 and BcLF1 was assessed for the ability to enhance the expression of HLA-A2.1, H-2Db, Kb and Dd on the murine RMA-S and human 721.174/T2 (.174/T2) lines by indirect immunofluorescence. Considering doubling of the fluorescence intensity in the peptide-treated samples as positivity, 6 of 39 HIV and 1 of 32 EBV peptides were found to bind to A2.1, 6 of 39 HIV gag and 7 of 16 EBV peptides to Db, 8 of 39 HIV gag and 5 of 16 EBV peptides to Kb and 2 of 39 HIV gag and 1 of 17 EBV peptides to Dd. The sensitivity of the method is comparable to the in vitro class I assembly assay with conformation-dependent monoclonal antibody and is more discriminating than the solid-phase assay. Due to its simplicity this method can also serve for testing large peptide panels for binding capacity to various class I molecules. Moreover, the method provides information about the relevance of in vitro tests for class I assembly in living cells.
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PMID:Assessment of major histocompatibility complex class I interaction with Epstein-Barr virus and human immunodeficiency virus peptides by elevation of membrane H-2 and HLA in peptide loading-deficient cells. 132 2

HIV infection of CD4+ peripheral blood lymphocytes leads to a loss of MHC class I molecules on the surface of the infected cells as detectable by monoclonal antibody staining and flow cytometry. Incubation of the infected cells at 26 degrees C or treatment at 37 degrees C with peptides leads to upregulation of MHC class I to levels equal to those found on uninfected cells cultured under the same conditions. The data suggest that, after HIV infection, the mechanisms responsible for peptide generation, peptide transport and thus stable association between peptides and MHC class I molecules are severely affected.
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PMID:Mechanism of MHC class I downregulation in HIV infected cells. 135 May 67

To understand better the specificity of peptide binding by MHC class I molecules, we have evaluated the capacity of a panel of unrelated peptides to compete for the presentation of viral peptides presented by HLA-A3 and HLA-B27. The HIV-Nef7F peptide (74-82) was presented by HLA-A3 to Nef-specific HLA-A3-restricted CTL lines, and the influenza nucleoprotein peptide NP(380-393) was presented by HLA-B27 to NP(380-393)-specific HLA-B27-restricted CTL lines. In addition, we have extended studies from our group that have evaluated the capacity of a similar panel of peptides to inhibit presentation of an influenza nucleoprotein peptide NP (335-349) by HLA-B37 and a matrix peptide, M1 (57-68), by HLA-A2 to the appropriate peptide-specific CTL lines. Out of 41 peptides tested, only five bound to more than one of the MHC molecules analyzed. Pairwise comparisons of the peptide binding specificities among these four different class I molecules revealed no common competitor peptides in four of the six possible comparisons. Thus, each class I molecule appears to have a functionally distinct peptide binding site, as reflected by the ability to bind largely non-overlapping sets of peptides.
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PMID:The peptide binding specificity of HLA class I molecules is largely allele-specific and non-overlapping. 137 81

Sp100, a protein with a dot-like intranuclear localization in immunofluorescence microscopy, is a major target for patient autoantibodies in primary biliary cirrhosis (PBC) and occasionally in rheumatic disorders. The human Sp100 cDNA has recently been cloned, and the deduced amino acid sequence was found to contain sequence similarities with an MHC class I domain and several transacting regulatory proteins, including HIV-1 nef proteins. In this study, recombinant Sp100 fusion proteins were used to differentiate the immunoglobulin isotypes and to map the epitopes involved in the anti-Sp100 autoimmune response. PBC patients developed IgG as well as IgM and/or IgA class anti-Sp100 autoantibodies whereas most patients with rheumatic diseases developed IgG class autoantibodies only. For epitope mapping, truncated versions of the Sp100 protein were probed for immunoreactivity in ELISA and immunoblotting. With 55 sera, 17 different reaction patterns were obtained, and at least three non-overlapping major autoantigenic domains were recognized by the majority of sera. One domain, which contains the sequence similarity with HIV nef proteins, was recognized by all anti-Sp100 sera and harbours multiple, in part discontinuous, epitopes. These data demonstrate a heterogeneous and patient-specific anti-Sp100 autoimmune response which is antigen-driven and, at least in terms of isotype composition, different in PBC and non-PBC patients.
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PMID:Autoantibodies to the nuclear Sp100 protein in primary biliary cirrhosis and associated diseases: epitope specificity and immunoglobulin class distribution. 138 13

In vivo priming of CTL requires the association with MHC class I molecules of peptides derived from the processing of endogenously produced proteins. Immunization with exogenous proteins or peptides rarely induces MHC class I-restricted CTL unless they are associated with lipidic compounds. The capacity to induce CTL was compared in synthetic peptides and simple lipopeptides containing the Immunodominant MHC class I H-2Dd-restricted T-cell epitope of HIV-1 gp160. In contrast with free peptides in saline, lipopeptides induced strong primary CTL responses in vivo. These CTL were able to lyse cells infected with a recombinant vaccinia virus expressing the HIV-1 env gene. Priming of CTL was also successful when using 16-amino acid lipopeptides as 34-amino acid lipopeptides, suggesting that several epitopes might be included in a single construct. In vivo priming of CTL also requires CD4+ T cell help. We therefore searched for Th cell activation after priming with lipopeptides. Our results show that, as with CTL induction, Th cell activation with lipopeptides did not require mixing with adjuvant. In addition, lipopeptides were also efficient at stimulating antibody-mediated responses. Our results show that a single lipopeptidic construct can induce a total immune response, which is of importance in vaccine development.
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PMID:Immunization of mice with lipopeptides bypasses the prerequisite for adjuvant. Immune response of BALB/c mice to human immunodeficiency virus envelope glycoprotein. 138 24

Studies to date assessing HIV escape from CTL in vivo have yielded conflicting results. Previous studies have demonstrated that simian immunodeficiency virus of macaques (SIVmac)-infected rhesus monkeys expressing the MHC class I allele Mamu-A*01 reproducibly develop a gag-specific CTL response limited to a 9-amino acid epitope of the SIVmac gag protein (residues 182-190 within peptide 11C). To determine whether CTL have a role in selecting for AIDS virus mutants, we examined mutations in SIVmac proviral DNA encoding this gag CTL epitope in PBL of infected rhesus monkeys. Three Mamu-A*01+ rhesus monkeys were infected with SIVmac and assessed for gag- and peptide 11C-specific CTL responses. This specific CTL response was maintained in two monkeys, but lost in the third animal 2 yr after infection. The generation of proviral gag mutations was then determined by sequencing 500-bp proviral fragments amplified from fresh PBL obtained from the monkeys more than 2.5 yr after infection. Although numerous point mutations were characterized in 131 polymerase chain reaction-generated clones of SIVmac gag, only four mutations within the gag CTL epitope-coding region of the genome were identified. Comparison of synonymous and nonsynonymous nucleotide substitutions in the regions encoding peptide 11C (p11C) and the flanking gag protein indicated a lack of selective pressure for viral mutations in the CTL epitope coding region. Interestingly, a predominant gag mutant encoding a single amino acid change in p11C was found in a monkey which lost its CTL activity. However, even in this setting there was no evidence for selection of mutations in the CTL epitope coding region when compared with the flanking region. Furthermore, synthetic peptides corresponding to all naturally occurring variants in the gag epitope-coding region were recognized by cloned and bulk cultured effector cells of the infected monkeys with persistent CTL. These results indicate that SIVmac gag- and p11C-specific CTL do not select for mutations in the immunodominant epitope-coding region and that the naturally occurring mutants do not appear to escape CTL recognition.
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PMID:Cytotoxic T lymphocytes do not appear to select for mutations in an immunodominant epitope of simian immunodeficiency virus gag. 146 Feb 91

The adjuvant activity of a single highly purified saponin from the soap bark tree Quillaja saponaria was evaluated by using it as a component in an experimental vaccine containing rHIV-1 envelope protein (HIV-1 160D) adsorbed to alum. BALB/c mice immunized with experimental vaccine formulations containing the saponin adjuvant QS-21 produced significantly higher titers of antibodies than mice vaccinated with only the alum-adsorbed HIV-1 160D. Potent amnestic antibody responses to HIV-1 viral proteins were also induced. Ag-specific proliferative responses to recombinant proteins and to three variants of HIV-1 were significantly increased using QS-21 as an adjuvant. Alum-adsorbed HIV-1 160D failed to induce measurable proliferative responses to inactivated HIV-1 viruses, but group-specific proliferative responses were raised when the QS-21 adjuvant was used in the vaccine formulation. MHC class I restricted CTL specific for the immunodominant V-3 loop were induced but only when the QS-21 adjuvant was included in the vaccine formulation. The production of serine esterase by Ag-activated splenic mononuclear cells, indicating the maturation of precursor CTL, was used as a secondary measure of CTL activity, and this response was also increased. The specificity of antibody responses was not significantly broadened using QS-21; the adjuvant increased the immune recognition of epitopes throughout the HIV-1 glycoprotein 160. However, the specificity of the proliferation and serine esterase responses was broadened, suggesting that the QS-21 augmented cell-mediated immune responses specific for epitopes outside of the V-3 loop. Additionally, the QS-21 adjuvant appeared to induce recognition of weakly immunogenic epitopes that were not recognized using only alum-adsorbed HIV-1 160D. The ability of QS-21 to augment both antibody and cell-mediated immune responses suggests that this adjuvant could be a valuable component in subunit vaccines.
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PMID:Saponin adjuvant enhancement of antigen-specific immune responses to an experimental HIV-1 vaccine. 153 34

The length of time after which persons infected with HIV-1 progress to AIDS is variable. Certain alleles at the MHC have been shown to influence negatively the clinical outcome of HIV-1-infected persons and to be associated with special clinical manifestations. We investigated the MHC class I, class II and class III antigens in 54 Caucasian HIV-1-infected persons. The MHC profile of individuals with a prolonged period before AIDS is marked by a lower frequency of C4 null alleles.
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PMID:Prolonged clinically asymptomatic evolution after HIV-1 infection is marked by the absence of complement C4 null alleles at the MHC. 157 87

The KBF1 factor, which binds to the enhancer A located in the promoter of the mouse MHC class I gene H-2Kb, is indistinguishable from the p50 DNA binding subunit of the transcription factor NF-kappa B, which regulates a series of genes involved in immune and inflammatory responses. The KBF1/p50 factor binds as a homodimer but can also form heterodimers with the products of other members of the same family, like the c-rel and v-rel (proto)oncogenes. The dimerization domain of KBF1/p50 is contained between amino acids 201 and 367. A mutant of KBF1/p50 (delta SP), unable to bind to DNA but able to form homo- or heterodimers, has been constructed. This protein reduces or abolishes in vitro the DNA binding activity of wild-type proteins of the same family (KBF1/p50, c- and v-rel). This mutant also functions in vivo as a trans-acting dominant negative regulator: the transcriptional inducibility of the HIV long terminal repeat (which contains two potential NF-kappa B binding sites) by phorbol ester (PMA) is inhibited when it is co-transfected into CD4+ T cells with the delta SP mutant. Similarly the basal as well as TNF or IL1-induced activity of the MHC class I H-2Kb promoter can be inhibited by this mutant in two different cell lines. These results constitute the first formal demonstration that these genes are regulated by members of the rel/NF-kappa B family.
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PMID:Inhibition of transcription factors belonging to the rel/NF-kappa B family by a transdominant negative mutant. 167 4

Monocyte/macrophages (MM) were isolated from HIV-1 seronegative individuals, infected with HIV-1 and examined for their ability to infect autologous T lymphocytes with and without concomitant presentation of exogenous Ag. HIV-1-infected MM presented tetanus toxin (TT) and streptokinase to T cells (as measured by [3H]thymidine incorporation) comparable to presentation by uninfected MM. In these studies, it was observed that HIV-1-infected MM without additional exogenous Ag stimulated autologous T lymphocytes, however, to a lesser degree than with TT and streptokinase. Virus production in T cells appeared to be relative to the degree of stimulation with the highest levels of stimulation and infection observed when T cells were exposed to HIV-1-infected TT-presenting MM. Studies were carried out to examine some of the restricting elements in MM-mediated infection of T lymphocytes with and without TT presentation. Antibodies to CD4, as well as soluble immunopurified gp120, blocked cell-mediated infection indicating that infection of T cells was through the CD4 molecule as has been demonstrated with cell-free virus. In addition, soluble gp120 inhibited Ag presentation by HIV-1-infected and uninfected MM. mAb to MHC class II Ag HLA-DR and -DP blocked T cell infection by HIV-1-infected MM with and without presentation of TT. No effect was observed with mAb to MHC class I Ag. These results indicate that virus transmission to T lymphocytes can be mediated by HIV-1-infected MM and that these cells maintain their function as APC. Activation of T cells appears to be important in the process of T cell infection in this system inasmuch as antibodies that block Ag presentation and thus a T cell proliferative signal inhibit infection.
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PMID:HIV-1 transmission and function of virus-infected monocytes/macrophages. 169 Feb 36


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