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

Among the varied cytotoxic immune reactivities elicited as a result of HIV-1 infection are two forms of non-MHC restricted cytotoxicity--namely, indirect and direct ADCC. Since these reactivities are directed at both HIV-1 infected as well as gp120 coated targets, there is a potential for anti-HIV-1 ADCC to play both a beneficial as well as a pathogenic role in the natural history of HIV-1 disease. Resolution of these issues will be of great importance to the development of future preventive and interventive therapeutic strategies for AIDS. The direct and indirect forms of ADCC described herein are, most probably, not unique to HIV-1. In theory, any viral disease, retroviral or otherwise, in which high titers of anti-envelope antibodies persist in an environment rich in Fc-receptor bearing effector NK/K cells would be likely to have some component of direct ADCC as part of the host anti-viral response. With this in mind it is imperative that those researchers involved in characterizing cellular anti-viral cytotoxicities do not mistake direct ADCC for another form of CTL activity. These two highly potent reactivities operate independently and are subject to different control mechanisms, both positive and negative, anti-viral ADCC has too long been regarded as a strictly in vitro phenomenon with no in vivo counterpart. Our studies demonstrating direct forms of ADCC in infected patients will hopefully have some impact in forcing a careful re-evaluation of this extremely important issue.
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PMID:Measurement of direct and indirect forms of anti-HIV-1 ADCC: implications for other retroviral disease. 228 91

Both infection with the human immunodeficiency virus type 1 (HIV) and zidovudine (formerly called azidothymidine [AZT]) cause myopathy. To identify criteria for distinguishing zidovudine-induced myopathy from that caused by primary HIV infection, we reviewed the histochemical, immunocytochemical, and electron-microscopical features of muscle-biopsy specimens from 20 HIV-positive patients with myopathy (15 of whom had been treated with zidovudine) and compared the findings with the patients' clinical course and response to various therapies. Among the zidovudine-treated patients, the myopathy responded to prednisone in four, to the discontinuation of zidovudine in eight, and to nonsteroidal anti-inflammatory drugs in two. Numerous "ragged-red" fibers, indicative of abnormal mitochondria with paracrystalline inclusions, were found in the biopsy specimens from the zidovudine-treated patients but not in those from the other patients. The number of these fibers appeared to correlate with the severity of the myopathy. All the patients, regardless of whether they had been treated with zidovudine, had inflammatory myopathy characterized by degenerating fibers, cytoplasmic bodies, and endomysial infiltrates consisting of CD8+ cells (mean +/- SD, 60.7 +/- 6.4 percent) and macrophages (39.2 +/- 6.4 percent) associated with Class I major histocompatibility complex (MHC-I) antigens (HLA-A, -B, and -C antigens) in the muscle fibers. The numbers and percentages of CD8+ cells and macrophages were similar in both the zidovudine-treated and the untreated HIV-positive patients. Specimens obtained on repeat muscle biopsy from two patients in whom the myopathy responded to the discontinuation of zidovudine showed remarkable histologic improvement. We conclude that long-term therapy with zidovudine can cause a toxic mitochondrial myopathy, which coexists with a T-cell-mediated inflammatory myopathy that is restricted to MHC-I antigen, and is indistinguishable from the myopathy associated with primary HIV infection or polymyositis in HIV-seronegative patients.
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PMID:Mitochondrial myopathy caused by long-term zidovudine therapy. 240 67

HIV-1-specific cell-mediated cytotoxicity (CMC) is a form of antibody-dependent cellular cytotoxicity (ADCC) in which HIV-1-specific antibodies arm NK cells directly to become cytotoxic for targets bearing HIV-1 antigenic determinants. This non-MHC-restricted cytotoxic activity is present in early stages of disease and declines markedly with disease progression. To understand the cellular and humoral factors contributing to the reduction in this activity, the conditions under which maximal arming of cells occurs was examined in vitro. With the use of a large patient cohort, a strong positive correlation was found between the capacity of a serum to direct lysis in standard ADCC assays and its ability to arm NK cells. Patients with minimal HIV-1-specific ADCC-directing antibodies exhibited low levels of CMC and were unable to arm normal effector cells in vitro. The lack of sufficient ADCC-directing antibodies was found to be one cause of defective CMC in some patients. Unlike asymptomatics, only a weak positive correlation was found between arming and ADCC with sera from AIDS patients, indicating that a factor other than absolute HIV-1 specific antibody titer was responsible for decreased CMC in this patient population. Another group of patients was found to have diminished CMC despite the presence of antibodies in the serum that were fully capable of arming normal effector cells to become cytotoxic for gp120-expressing targets. When compared with those of normal individuals, lymphocytes from seropositive patients mediated significantly reduced levels of cytotoxicity in ADCC and arming assays with the use of a high titered HIV-1-specific serum. In both assay systems, the magnitude and frequency of dysfunction in antibody-dependent cytolysis was found to be greater among AIDS patients than among asymptomatic individuals. The demonstration of both cellular and humoral defects in the ability of seropositive individuals to manifest ADCC reactivities strongly suggests that HIV-1 infection may significantly compromise the effectiveness of this potentially important cytolytic reactivity in vivo.
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PMID:Alterations in antibody-dependent cellular cytotoxicity during the course of HIV-1 infection. Humoral and cellular defects. 232 75

To characterize the cytotoxic events taking place in the lung of patients with HIV-1 infection, we studied the cells recovered from the bronchoalveolar lavage (BAL) of nine patients with AIDS, seven patients with AIDS-related complex, and two patients with lymphadenopathy. Phenotypic analysis was coupled to a series of functional evaluations of nonspecific cytotoxic abilities performed on lung effectors, including their property to bind K-562 targets, to release natural killer cytotoxic factor (NKCF), and to become cytotoxic following in vitro activation with rIL-2. Our results demonstrated that lung cells bearing the NK-related CD16, CD56, and CD57 antigens were quantitatively increased, irrespective of the disease stage. The majority of the cells also coexpressed the CD3 molecule and the alpha/beta T cell receptor (TCR), notably the phenotype characterizing MHC-unrestricted cytotoxic T cells. From a functional point of view, a severe impairment of the spontaneous cytotoxic ability was demonstrated in most patients. Evaluation at the single cell level showed a normal percentage of the effector/target conjugates formed by HIV-1 lymphocytes. The release of NKCF was undetectable in patients with AIDS even following lectin stimulation, whereas BAL cells from patients with earlier infection produced and/or could be triggered to release discrete amounts of NKCF by incubation with PHA. Studies designed to activate lung cytotoxic cells with rIL-2 showed that in most patients the stimulation of effector cells with rIL-2 enhanced the spontaneous killing and elicited a lymphokine-activated killer (LAK) phenomenon.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cytotoxic events taking place in the lung of patients with HIV-1 infection. Evidence of an intrinsic defect of the major histocompatibility complex-unrestricted killing partially restored by the incubation with rIL-2. 238 2

Immunosuppression in AIDS might be due to the immune response rather than to the pathogenicity of the virus. The basis of the immunosuppression could be molecular mimicries involving viral gp-110, CD4 molecules, antibodies, and CD4-acceptor sites. Whether an individual develops auto-immunosuppressive responses or mounts a harmless defence against (or coexists with) the virus follows the general rules of lymphocyte repertoire selection. MHC and V region genes and other polymorphic loci, together with the previous state of the immune system, particularly at early developmental periods, are factors that influence the response. Vaccination against gp 110-HIV might thus protect against infection but at the same time cause auto-immunosuppression and disease.
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PMID:Immunological consequences of HIV infection: advantage of being low responder casts doubts on vaccine development. 244 91

Vaccines incorporating HIV envelope antigens are being developed for the prevention of AIDS. To determine whether HIV envelope antigens are recognized by human cytotoxic T-lymphocytes (CTL), we assessed class I MHC-restricted, HIV envelope antigen-specific cytotoxic activity of peripheral blood mononuclear cells (PBMC) from HIV-infected individuals, following in vitro stimulation. The target cells were human skin fibroblasts of known tissue type, infected with recombinant vaccinia viruses, either containing or lacking the whole HIV envelope gene. Ten out of 17 (59%) asymptomatic HIV-seropositive individuals demonstrated HIV envelope antigen-specific cytotoxicity at levels that were above those seen in HIV-seronegative controls. MHC restriction of cytotoxicity was evident in that 13 out of 19 (68%) of the targets matched for the tissue type of the donor at one or more class I MHC loci were lysed, but only two out of 18 (11%) mismatched targets (P = 0.0004). Both partial purification of effector cells and evidence of MHC restriction indicated that T-lymphocytes were responsible for the observed cytotoxicity. HIV envelope antigen-specific CTL can be detected following in vitro stimulation of the PBMC in many asymptomatic HIV-seropositive individuals. HIV envelope antigens are recognized by human CTL and are, therefore, potentially relevant immunogens for induction of HIV-specific CTL responses.
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PMID:Human class I MHC-restricted cytotoxic T-lymphocytes specific for human immunodeficiency virus envelope antigens. 245 43

In this report we have attempted to review our knowledge of the role(s) of CD4 in human T-cell function and the consequences of interactions between CD4 molecules and the human immunodeficiency virus (HIV). The observation in 1981 that antibodies to certain epitopes of CD4 inhibited the immune functions of CD4+ T cells led to the initial suggestion that CD4 molecules play a direct role in T-cell function. Although the precise functions of CD4 remain incompletely understood, a preponderance of evidence suggests that this molecule may in fact serve several critical roles. At least one such role is that of interacting directly with MHC class II molecules on antigen-presenting cells, presumably facilitating cell-to-cell interactions. On activated CD4+ T cells, CD4 molecules can also interact directly with the T-cell receptor complex to influence the immune response. Unfortunately, in addition to interacting with the T-cell receptor and class II MHC determinants, CD4 serves as a high affinity receptor for HIV, the causative agent of AIDS. Not only does interaction between the virus and CD4 initiate viral fusion to the cell membrane and HIV entry but, in addition, a similar molecular interaction initiates fusion between HIV-infected and uninfected CD4+ cells, resulting in the formation of multinucleated syncytia. Since uninfected CD4+ cells are, in effect, recruited into such syncytia, this mechanism may account in part for the depletion of CD4+ T cells in HIV-infected patients. Soluble forms of CD4 produced either by genetic engineering or solid phase peptide synthesis can completely block HIV infectivity and syncytia formation in vitro, remarkably without apparent effects on T-cell immunity. Such molecules are currently being explored for their possible therapeutic effects on HIV infection in vivo.
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PMID:Role of CD4 in normal immunity and HIV infection. 247 27

In H-2d mice, the immunodominant determinant of the HIV-1-IIIB gp160 envelope glycoprotein recognized by CD8+ CTL is represented by a 15-residue synthetic peptide (315-329: RIQRGPGRAFVTIGK). This peptide is seen in association with the Dd class I MHC molecule expressed on H-2k L cell fibroblast targets. We explored the structural requirements for CTL recognition of this peptide at the levels of both the peptide molecule and the class I MHC molecule. Using several transfectants expressing recombinant Dd/Ld molecules, we found that presentation of this epitope required both the alpha 1 and alpha 2 domains of the Dd molecule, in contrast to certain instances of allorecognition for which alpha 1 of Dd was sufficient in association with alpha 2 of Ld. Because this peptide derives from a hypervariable segment of the HIV envelope, substituted peptides could be used to define not only the structures affecting interaction of peptide with class I MHC molecule and with the TCR, but also the structural basis for the effect of naturally occurring viral variation on CTL recognition. The CTL-LINE specific for this HIV-1-IIIB-derived sequence could not recognize the HIV-1-RF variant-derived sequence from exactly the same site (315-329:--HIGPGRVIYATGQ). Peptides with single amino acid substitutions from the HIV-1-IIIB sequence toward the HIV-1-RF sequence were made to test the effect of each residue significantly affected recognition, and only one, 324(F), was obligatory. Moreover, both 322(R) and 324(F) substituted peptides failed to inhibit the binding of the wild type peptide to the MHC molecule. Therefore, the amino-acids 322(R) and 324(F) seem to be involved in regulating peptide interaction with the Dd class I MHC molecule. In contrast, 325(V) appeared to affect interaction with the TCR. We suggest that sequence variations among known HIV-1 isolates that affect peptide binding to MHC such as those described here, if occurring during the course of infection of an individual, could result in failure of the MHC molecules of that individual to present the peptide. If the number of dominant HIV CTL epitopes is indeed very limited, such a blind spot could allow the virus to escape immune control, proliferate rapidly, and cause AIDS.
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PMID:Structural requirements for class I MHC molecule-mediated antigen presentation and cytotoxic T cell recognition of an immunodominant determinant of the human immunodeficiency virus envelope protein. 247 5

The human cell surface protein CD4 is not only an important accessory molecule in the activation of MHC class-II-restricted T cells, but has also been implicated to be a receptor for the human immunodeficiency virus HIV-I on lymphoid and monocytic cells. We have found that a 24-h treatment of the promonocytic leukemia cell line U937 with rIFN-gamma decreases the expression of the CD4 Ag by 50% as measured by cytofluorographic analysis. The decrease in CD4 expression was dependent on the concentration of rIFN-gamma, with maximal effects occurring at 20 to 200 U/ml. The decrease appeared to be due to actual loss of the CD4 molecule from the cell surface rather than masking of a particular epitope, inasmuch as similar results were obtained with the OKT4 and OKT4A antibodies. The effect of rIFN-gamma to decrease CD4 expression was not due to a general loss of cell surface Ag, because the binding of OKM1 and anti-HLe-1 increased after rIFN-gamma treatment. Treatment of rIFN-gamma also decreased cell surface CD4 expression on the promyelocytic leukemia cell line HL-60, and on the monocytic cell line THP-1, although the extent of the decrease was less than on U937 cells. Freshly isolated normal peripheral blood monocytes treated for 48 h with rIFN-gamma bound much less OKT4 or OKT4A antibody than cells incubated in the absence of rIFN-gamma. Moreover, treatment with rIFN-gamma reduced the percentage of peripheral blood monocytes that were positive for the CD4 Ag. In contrast with the decrease in CD4 levels on rIFN-gamma-treated monocytes, treatment with rIFN-gamma had no effect on CD4 levels on peripheral blood T lymphocytes or T cell lines.
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PMID:Treatment with recombinant IFN-gamma decreases cell surface CD4 levels on peripheral blood monocytes and on myelomonocyte cell lines. 249 48

Cytotoxic cells appear to play an important role in host defense against viral infection. In HIV-1 infection there is an expansion of the Leu7-positive lymphocyte population which is associated with cytotoxic activity. Since a form of non-MHC-restricted T-cell cytotoxicity [lectin-dependent cell cytotoxicity (LDCC)] has been reported to be mediated by CD3+Leu7+ cells, we evaluated LDCC and Leu7-positive lymphocyte populations in HIV-1-infected subjects and healthy controls. Both LDCC and percentages of Leu7+CD3+ and Leu7+CD2+ cells were increased in HIV-1-infected individuals as compared to controls. However, the CD3+Leu7+ lymphocyte population was increased to a greater degree than the CD8+Leu7+ population and a minor Leu7+ cell population (Leu7+CD4+) was expanded in the early stages of infection. Lectin-dependent cell cytotoxicity was positively correlated with the percentages of Leu7+CD3+ cells. Thus T-cells with the capacity to mediate high levels of non-MHC-restricted cytotoxicity are present in increased proportions in HIV-1-infected individuals and persist in advanced disease. Further studies are required to see if these cells participate in HIV-specific cytotoxicity or reflect an aberrant, ineffective, or immunologically detrimental response to the virus.
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PMID:T cells expressing high levels of non-major histocompatibility complex (MHC)-restricted cytotoxicity are present in early and late clinical phases of human immunodeficiency virus 1 (HIV-1) infection. 252 2

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