title: Regulation of interleukin-18 by THP-1 monocytoid cells stimulated with HIV-1 and Nef viral protein.
abstract: Interleukin (IL)-18 is a proinflammatory cytokine that plays an important role in both innate and adaptive immune responses against several infectious pathogens. Relatively little is known about its production in HIV-1 infection, and there are controversial data on the influence of IL-18 on HIV-1 replication in vitro. In this study, we investigated the effect of HIV-1 infection, and challenge with recombinant HIV-1 proteins, on IL-18 production by THP-1 cells. This is a monocytoid cell line spontaneously producing IL-18, and consequently is particularly suitable for the study of HIV-1 effects on this type of cytokine regulation. The results reported here demonstrate a significant reduction in IL-18 secretion during HIV-infection. In fact, low levels of IL-18 were released until 120 h from viral challenge (15 +/- 11 pg/mL at 24 h and 17 +/- 13 at 96 h and < 12.5 at 120 h), whereas IL-18 production by uninfected control cells was 193 +/- 104 pg/mL and 214 +/- 114 pg/mL at 24 h and 120 h respectively. At 168 h of incubation, IL-18 production by infected and uninfected cells was found to be 164 +/- 88 pg/mL and 325 +/- 101 pg/mL respectively (p = 0.001). Of the following viral proteins: gp 120, p24 and Nef, only the last one induced decreased IL-18 secretion in the supernatants of THP-1 cells. This effect is more evident with the concentrations of 5 -1.25 microg/mL of Nef protein (p < 0.0001). In conclusion, our data show that HIV-1 and its regulatory protein, Nef, are able to down-regulate the release of IL-18, in vitro. These results confirm that a variety of modulating effects on the immune response, induced by HIV-infection, may facilitate progression of HIV-1 infection.
authors.affiliation: Department of Medical and Surgical Sciences, Section of Clinical Microbiology of Turin University, Amedeo di Savoia Hospital, Turin, Italy.
authors.forename: Agostino
authors.initials: A
authors.lastname: Pugliese
authors.forename: Valerio
authors.initials: V
authors.lastname: Vidotto
authors.forename: Tiziana
authors.initials: T
authors.lastname: Beltramo
authors.forename: Donato
authors.initials: D
authors.lastname: Torre
mesh_terms: D045744:Cell Line, Tumor; D015536:Down-Regulation; D015693:Gene Products, nef / Q000494:pharmacology*; D015497:HIV-1 / Q000502:physiology*; D006801:Humans; D020382:Interleukin-18 / Q000378:metabolism*; D009000:Monocytes / Q000187:drug effects / Q000276:immunology / Q000821:virology; D054311:nef Gene Products, Human Immunodeficiency Virus
chemical_list: D015693:Gene Products, nef; D020382:Interleukin-18; D054311:nef Gene Products, Human Immunodeficiency Virus