title: Pronounced acute immunosuppression in vivo mediated by HIV Tat challenge.
abstract: HIV infection is accompanied by an early immune dysfunction limiting host control of virus and likely contributing to difficulties in achieving a successful vaccine against HIV. We report here that the HIV Tat protein is strongly immunosuppressive, both immediately after immunization of mice with soluble protein (sTat), and in seroconverting humans, and propose that Tat-induced suppression cripples immune surveillance to HIV infection. We show that macrophages are sensitive to sTat stimulation at concentrations 1,000-fold lower (500 pM) than T cells, and this stimulation is accompanied by the immunosuppressive induction of Fas ligand on the macrophage. T cell proliferative defects induced by sTat in vitro can be completely (at lower concentrations of sTat) or partially (at higher concentrations) reversed by antagonists to Fas/Fas ligand interaction. We further report a method to preserve immunogenicity while inactivating Tat immunosuppression through oxidation, which advances the use of oxidized Tat as a component of an anti-HIV vaccine. These observations define additional methods to study the immunosuppressive functions of sTat that now may be rapidly applied to primary isolates from individuals with differing clinical courses. Our findings have immediate relevance for vaccine development, by describing and supporting a strategy that includes inactivated sTat in a multicomponent, anti-HIV vaccine.
authors.affiliation: Dermatology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: S S
authors.initials: SS
authors.lastname: Cohen
authors.forename: C
authors.initials: C
authors.lastname: Li
authors.forename: L
authors.initials: L
authors.lastname: Ding
authors.forename: Y
authors.initials: Y
authors.lastname: Cao
authors.forename: A B
authors.initials: AB
authors.lastname: Pardee
authors.forename: E M
authors.initials: EM
authors.lastname: Shevach
authors.forename: D I
authors.initials: DI
authors.lastname: Cohen
mesh_terms: D016915:AIDS Vaccines / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D053222:Fas Ligand Protein; D005434:Flow Cytometry; D015696:Gene Products, tat / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology*; D015658:HIV Infections / Q000276:immunology / Q000378:metabolism; D006801:Humans; D007108:Immune Tolerance / Q000502:physiology*; D015151:Immunoblotting; D007963:Leukocytes, Mononuclear / Q000276:immunology / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D011994:Recombinant Proteins / Q000494:pharmacology; D006377:T-Lymphocytes, Helper-Inducer / Q000187:drug effects; D054322:tat Gene Products, Human Immunodeficiency Virus
chemical_list: D016915:AIDS Vaccines; C505661:FASLG protein, human; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D015696:Gene Products, tat; D008562:Membrane Glycoproteins; D011994:Recombinant Proteins; D054322:tat Gene Products, Human Immunodeficiency Virus