title: Interleukin-8 fails to induce human immunodeficiency virus-1 expression in chronically infected promonocytic U1 cells but differentially modulates induction by proinflammatory cytokines.
abstract: This study addresses the role of interleukin (IL)-8, a CXC-chemokine, the level of which is reported to be raised in the peripheral circulation of human immunodeficiency virus-1 (HIV-1)-infected individuals, during the induction of HIV-1 expression from latency and during cytokine-mediated HIV-1 up-regulation. IL-8 at the higher concentrations tested (> or = 100 ng/ml) was unable to induce HIV-1 expression in the chronically infected promonocytic U1 cell line, as measured by p24 antigen enzyme-linked immunosorbent assay (ELISA), whereas at lower concentrations of 1 and 10 ng/ml, constitutive HIV-1 expression was only marginally reduced. HIV-1 replication in acutely infected U937 cells was also significantly reduced by IL-8. The potent up-regulation of HIV-1 expression in U1 cells by tumour necrosis factor-alpha (TNF-alpha) remained unaffected by the addition of IL-8. HIV-1 induction by IL-1beta, IL-6 and TNF-beta, cytokines grouped here as intermediate HIV-1 inducers, was suppressed by IL-8 at concentrations of 1 and 10 ng/ml. However, IL-8 at 100 ng/ml did not significantly alter the effect of IL-1beta, synergized with IL-6 in enhancing, and marginally suppressed TNF-beta-induced HIV-1 expression. IL-8 suppressed granulocyte-macrophage colony-stimulating factor (GM-CSF) and enhanced interferon-gamma (IFN-gamma)-induced HIV-1 expression in a dose-dependent manner. Pretreatment of U1 cells with IL-8 did not alter the IL-8-mediated effects on cytokine-induced HIV-1 expression, suggesting that this chemokine exerts its effect at the time of HIV-1 induction or at a postinduction stage. Furthermore, IL-8 was itself induced by cytokines that up-regulate HIV-1 expression in U1 cells and the levels produced correlated directly with the levels of p24 antigen produced, suggesting common pathways for cytokine induction of both HIV-1 and IL-8. These results show that IL-8, typically a non-inducer, can differentially modulate HIV-1 expression in U1 cells and that this is dependent on the inducing cytokine and on the concentration of IL-8.
authors.affiliation: AIDS Virus Research Unit, National Institute for Virology and Department of Virology, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: C T
authors.initials: CT
authors.lastname: Tiemessen
authors.forename: B
authors.initials: B
authors.lastname: Kilroe
authors.forename: D J
authors.initials: DJ
authors.lastname: Martin
mesh_terms: D000208:Acute Disease; D002908:Chronic Disease; D016207:Cytokines / Q000276:immunology; D004306:Dose-Response Relationship, Immunologic; D015658:HIV Infections / Q000276:immunology* / Q000821:virology; D015497:HIV-1 / Q000502:physiology*; D006801:Humans; D016209:Interleukin-8 / Q000276:immunology*; D009000:Monocytes / Q000821:virology; D020298:U937 Cells; D014779:Virus Replication / Q000276:immunology*
chemical_list: D016207:Cytokines; D016209:Interleukin-8