UMLS:C0019693 - FACTA Search

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

Peyer's patch (PP) T cells through the production of appropriate cytokines foster the development of immunity to the intestinal protozoan parasites such as Giardia. T cell destruction by the human immunodeficiency virus precedes the development of acquired immune deficiency syndrome. Thus, HIV may increase susceptibility to intestinal parasite infections. Therefore, we measured the resistance and T cell cytokine responses to Giardia in C57B1/6 mice infected with the retrovirus LP-BM5 which produces a murine AIDS (MAIDS). Mice with MAIDS and controls were intragastrically challenged with 1 x 10(5) G. muris cysts. Fecal counts were measured weekly following challenge. Also, PP T cell production of interleukin (IL)2, IL3, IL4, and Interferon-gamma in response to G. muris trophozoite antigens displayed on antigen presenting cells were measured at these times. Prior to day 14 of the infection, the number of Giardia cysts in the retrovirus group paralleled that in controls. However, by day 21 after Giardia infection, mice with MAIDS failed to clear the Giardia cysts from the intestine while the control mice were completely free of cysts. IL2 and IL4 production in response to Giardia trophozoites by unfractionated PP lymphocytes were severely depressed in the retrovirus infected group, while IFN-gamma production was increased. Depressed cytokine production was most likely due to depressed PP T cell numbers. When fractionated enriched T cells were adjusted to a uniform concentration in in vitro immunization cultures, the production of IL2 and IL4/IL5 were similar between retrovirus infected compared with control mice. Recoverable PP T cells were lower in mice with MAIDS.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Suppression of resistance to Giardia muris and cytokine production in a murine model of acquired immune deficiency syndrome. 129 11

Parasitic infection is frequently accompanied by a downregulation in host cell-mediated immunity. Recent studies suggest that this modulation of helper T cells and effector cell function can at least in part be attributed to the action of a set of inhibitory cytokines produced by T lymphocytes as well as by a number of other cell types. The best characterized of these inhibitory lymphokines are IL-4, IL-10 and TGF-beta. Interestingly, both IL-4 and IL-10 are produced by the Th2 but not the Th1 subset of CD4+ helper cells. The former subset dominates in many situations of chronic or exacerbated parasitic infection and is thought to suppress Th1 function as a consequence of the cross-regulatory activity of these two cytokines. The latter hypothesis is supported by recent experiments demonstrating that mAb-mediated neutralization of IL-10 reverses suppressed IFN-gamma responses and/or disease susceptibility in mice with parasitic infections. In vivo neutralization of TGF-beta has also been reported to increase host resistance to parasite challenge. In addition to suppressing T-cell differentiation, function or proliferation, IL-4, IL-10 and TGF-beta each inhibit the ability of IFN-gamma to activate macrophages for killing of both intracellular and extracellular parasites. Moreover, the three cytokines are able to synergize with each other in downregulating these parasiticidal effects. Interestingly, each of the cytokines inhibits the production of reactive nitrogen oxides, an effector mechanism previously demonstrated to play a major role in parasite killing by activated macrophages. In the case of IL-10, this suppression of nitrogen oxide production appears to result from an inhibition of TNF-alpha synthesis leading to defective macrophage stimulation. While distant from parasites in their biology and phylogeny, some retroviruses also appear to induce an over-production in downregulatory cytokines which is closely associated with the onset of immunodeficiency. Thus, in an animal model involving infection of mice with LP-BM5 MuLV and in human HIV infection, Th2 (IL-10 and/or IL-4) cytokine synthesis is increased while Th1 (IFN-gamma and/or IL-2) cytokine production is suppressed. These observations suggest that cytokine-mediated cross-regulation may play a role in the pathogenesis of acquired immune deficiency disease, contributing both to the progression of retroviral infection and the increase in susceptibility to opportunistic infections and malignancy. Observations of similar cytokine cross-regulatory activities in organisms as diverse as helminths, protozoa and retroviruses predict that comparable mechanisms may operate in a wide variety of infectious diseases.
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PMID:Role of T-cell derived cytokines in the downregulation of immune responses in parasitic and retroviral infection. 135 51

Natural Killer cell Stimulatory Factor (NKSF) or interleukin-12 (IL-12) is a heterodimeric cytokine of 70 kDa formed by a heavy chain of 40 kDa (p40) and a light chain of 35 kDa (p35). Although it was originally identified and purified from the supernatant of Epstein-Barr virus-transformed B cell lines, it has been shown that among peripheral blood cells NKSF/IL-12 is predominantly produced by monocytes, with lower production by B cells and other accessory cells. The most powerful inducers of NKSF/IL-12 production are bacteria, bacterial products and parasites. In addition to the biologically active p70 heterodimer, the cells producing NKSF/IL-12 also secrete a large excess of monomeric p40, a molecule with no demonstrable biological activity. NKSF/IL-12 is active on T lymphocytes and NK cells on which it induces production of lymphokines, enhancement of cytotoxic activity and mitogenic effects. NKSF/IL-12 induces T and NK cells to produce IFN-gamma and synergizes with other IFN-gamma inducers in this effect. In vitro, and probably in vivo, NKSF/IL-12 is required for optimal IFN-gamma production. When human lymphocytes are stimulated with antigens in vitro, addition of exogenous NKSF/IL-12 to the culture induces differentiation of T helper type 1 (Th1) cells, whereas neutralization of endogenous NKSF/IL-12 with antibodies favors differentiation of Th2 cells. IFN-gamma, a product of Th1 cells, enhances NKSF/IL-12 production by mononuclear cells, whereas IL-10 and IL-4, products of Th2 cells, efficiently inhibit it. Therefore, NKSF/IL-12 appears to be an important inducer of Th1 responses produced by accessory cells during early antigenic stimulation and its production is regulated by a positive feedback mechanism mediated by Th1 cells through IFN-gamma and a negative one by Th2 cells through IL-10 and IL-4. The balance of IL-12 production versus IL-10 and IL-4 production early during an immune response might therefore be instrumental in determining Th1-type versus Th2-type immune responses. Because of this potential role of IL-12 during immune responses, our results demonstrating the impaired ability of HIV seropositive patients to produce NKSF/IL-12 in response to bacterial stimulation suggest that this defect in NKSF/IL-12 production might be a factor contributing to their immune depression.
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PMID:Natural killer cell stimulatory factor (NKSF) or interleukin-12 is a key regulator of immune response and inflammation. 136 96

The interferon (IFN) system, both serum IFN levels and the in vitro IFN production, was investigated in 38 clinically asymptomatic multitransfused hemophiliacs, half positive and half negative for HIV antibodies. In most patients, no circulating IFN was detected; similar levels of IFN-alpha were obtained after peripheral blood mononuclear cell (PBMC) stimulation with Sendai virus both in hemophiliacs and controls, while production of IFN-gamma following stimulation with phytohemagglutin (PHA) was diminished in a large number of patients irrespective of their HIV serology. These data indicate that the deficiency in IFN-gamma generation is not only related to HIV contamination but may be a direct consequence of the chronic antigenic stimulation through Factor VIII concentrates.
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PMID:Interferon production in severe hemophiliacs with and without HIV antibodies. 164 Jan 13

We have developed a method for attenuating vaccinia virus recombinants by expressing a fusion protein of a lymphokine and an immunogen. Chimeric genes were constructed that coded for gamma interferon (IFN-gamma) and structural proteins of the human immunodeficiency virus type 1 (HIV-1). In this study, we describe the biological and immunological properties of vaccinia virus recombinants expressing chimeric genes of murine or human IFN-gamma with glycoprotein gp120, gag, and a fragment of gp41. All fusion proteins retained the antigenic characteristics of both IFN-gamma and HIV as shown by immunoblot analysis. However, the antiviral activity of IFN-gamma could be demonstrated only for the IFN-gamma-gag fusion protein. In contrast, the attenuating activity of IFN-gamma for nude mice was retained by all of the recombinants, albeit at various rates. Unlike the antiviral activity, the attenuating activity of IFN-gamma was not species specific. Implications for the development of attenuated live recombinant vaccines for AIDS are discussed.
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PMID:Vaccinia virus recombinants expressing chimeric proteins of human immunodeficiency virus and gamma interferon are attenuated for nude mice. 156 33

HIV multiplication in blood-derived macrophages was slightly inhibited by pretreatment of cells with interferon-gamma or by preincubation of virus with serum containing antibodies against HIV. When these pretreatments were combined, the HIV titres observed a short time after infection were enhanced. This effect was blocked by antibodies against Fc receptors but not by antibodies against CD4 receptors. Interferon enhanced the expression of Fc receptors on macrophages. The results indicate that IFN-gamma, in appropriate combinations with HIV-antibody-containing human serum, may enhance the rate of HIV infection of macrophages.
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PMID:Interferon-gamma may enhance infection of blood-derived macrophages with HIV-1 in the presence of HIV-positive serum. 158 84

Peripheral blood mononuclear cells (PBMCs) from HIV-seronegative donors were infected in vitro with HIV-1. Infection was monitored by cytopathology, supernatant p24 antigen, and by immunocytochemical staining. After 14 days in culture, approximately 70-90% of the cells became infected with HIV, as indicated by cell fusion and immunostaining for virus. At this time, recombinant HuIFN-gamma was added to the cultures, followed by infection 24 h later with the intracellular protozoan parasites Toxoplasma gondii, Trypanosoma cruzi, or Leishmania chagasi. Percentages of intracellular parasites were determined at various points thereafter. Using a system capable of detecting both virus and parasite infection, we determined that (a) cells infected with HIV were capable of ingesting and/or being infected by each of these parasitic protozoa, (b) HIV-infected macrophages could be activated to inhibit the replication of all three parasites following treatment with IFN-gamma, and (c) cultures of HIV-infected macrophages could respond to IFN-gamma with increased oxidative burst activity. The degree of parasite infection or inhibition observed in infected cells was not significantly different from that observed in non-HIV-infected cells. From these observations, we concluded that HIV-1 infection does not render macrophages unresponsive to IFN-gamma activation for microbicidal activity.
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PMID:Cytokine activation of human macrophages infected with HIV-1 to inhibit intracellular protozoa. 161 64

A monocytic cell line, THP-1, was acutely infected with HIV, and the effects of various factors including INF-gamma, LPS, IL-2, and IL-6 were analyzed. While IFN-gamma suppressed HIV production, IL-2 and IL-6 augmented it. The suppressive effect of IFN-gamma was not overcome by IL-2 or by LPS. We studied whether the induction of IL-2 receptor alpha (IL-2R alpha) expression by those factors was related to HIV infection or not. By immunofluorescence analysis using monoclonal anti-IL-2R alpha antibody, we observed that HIV infection itself induced IL-2R alpha expression moderately in U937 and THP-1, and IL-6 as well as IFN-gamma highly induced IL-2R alpha expression both in uninfected and infected THP-1. Although induction of HIV production and IL-2R alpha expression by cytokines seem not to be directly correlated, these results suggest that soluble IL-2R alpha increased in AIDS patients might be at least partly derived from infected monocyte/macrophages activated by various cytokines, especially IL-6, which is mainly produced by themselves.
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PMID:Effect of cytokines on HIV release and IL-2 receptor alpha expression in monocytic cell lines. 169 Dec 89

Tryptophan (Trp) is an indispensable amino acid required for biosynthesis of proteins, serotonin and niacin. Indoleamine 2,3-dioxygenase (IDO) is induced by infections, viruses, lipopolysaccharides, or interferons (IFNs) and this results in significant catabolism of Trp along the kynurenine (Kyn) pathway. Intracellular growth of Toxoplasma gondii and Chlamydia psittaci in human fibroblasts in vitro is inhibited by IFN-gamma and this inhibition is negated by extra Trp in the medium. Similarly, growth of a number of human cell lines in vitro is inhibited by IFN-gamma and addition of extra Trp restores growth. Thus, in some in vitro systems, antiproliferative effects of IFN-gamma are mediated by induced depletion of Trp. We find that cancer patients given Type I or Type II IFNs can induce IDO which results in decreased serum Trp levels (20-50% of pretreatment) and increased urinary metabolites of the Kyn pathway (5 to 500 fold of pretreatment). We speculate that in vivo antineoplastic effects of IFNs and clinical side effects are mediated, at least in part, by a general or localized depletion of Trp. In view of reported increases of IFNs in autoimmune diseases and our earlier findings of elevated urinary Trp metabolites in autoimmune diseases, it seems likely that systemic or local depletion of Trp occurs in autoimmune diseases and may relate to degeneration, wasting and other symptoms in such diseases. We find high levels of IDO in cells isolated from synovia of arthritic joints. IFNs are also elevated in human immunodeficiency virus (HIV) patients and increasing IFN levels are associated with a worsening prognosis. We propose that IDO is induced chronically by HIV infection, is further increased by opportunistic infections, and that this chronic loss of Trp initiates mechanisms responsible for the cachexia, dementia, diarrhea and possibly immunosuppression of AIDS patients. In these symptoms, AIDS resembles classical pellagra due to dietary deficiency of Trp and niacin. In preliminary studies, others report low levels of Trp and serotonin, and elevated levels of Kyn and quinolinic acid in AIDS patients. The implications of these data in cancer, autoimmune diseases and AIDS are discussed.
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PMID:Implications of interferon-induced tryptophan catabolism in cancer, auto-immune diseases and AIDS. 172 46

We investigated monocyte-derived macrophage function in 25 HIV-positive patients, 19 in the CDC class III and 6 class IV; 17 were intravenous drug abusers (IVDA) and 8 were homosexual men. Macrophages from HIV-positive patients behaved normally in assays of superoxide anion (O2-) production and candidacidal activity. After 3 days' treatment with 200 U/ml recombinant interferon-gamma (rIFN-gamma) or 250 U/ml recombinant granulocyte/macrophage-colony stimulating factor (rGM-CSF), both control and HIV-positive patients' phagocytes expressed the activated state, as indicated by the increased O2- production in response to phagocytable or soluble stimuli; however, these cytokines did not enhance candidacidal activity. Compared to appropriate HIV-negative controls (18 healthy heterosexuals, 4 homosexuals and 4 IVDA), macrophages from 19 of the 25 HIV-positive patients presented a significant defect in their Fc receptor (FcR)-dependent phagocytosis, independently from the CDC stage, AZT therapy, or life style. Treatment of macrophages with rIFN-gamma impaired their capacity to ingest IgG-coated erythrocytes, both in controls and HIV-positive subjects. Treatment of phagocytes with rGM-CSF significantly increased their FcR-dependent phagocytosis in controls, whereas in HIV-positive patients and in HIV-negative homosexuals and IVDA only an upward tendency was observed. Although the mechanism of the impaired FcR-dependent phagocytosis in HIV-positive patients remain to be clarified, our results suggest that this functional defect may be secondary to phagocyte priming by circulating IFN-gamma in vivo. This macrophage alteration may be implicated in the immunodeficiency of HIV-positive patients. However, considering the potential role of FcRs in HIV infection enhancement, the defective FcR function might even be a protective mechanism against FcR-mediated HIV dissemination. In the light of these findings, the immunotherapeutic potential of IFN-gamma and GM-CSF in HIV infection merits further investigation.
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PMID:Monocyte-derived macrophage function in HIV-infected subjects: in vitro modulation by rIFN-gamma and rGM-CSF. 173 Jan 55

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