title: Oligonucleotide-mediated inhibition of CD28 expression induces human T cell hyporesponsiveness and manifests impaired contact hypersensitivity in mice.
abstract: Ligation of CD28 provides a costimulatory signal essential for Ag-mediated T cell activation via the TCR. Blocking CD28 ligation can inhibit cytokine expression and elicits a state of T cell hyporesponsiveness. In this study, we examined the effect of inhibiting CD28 expression on in vitro and in vivo T cell responses. To address this, we have synthesized a series of G-rich phosphorothioate oligonucleotides that inhibited activation-induced transcription and cell surface expression of CD28 on human T cells. CD28 blockade was selective, as expression of other activation-induced receptors was unaffected by oligonucleotide treatment. Using strategic changes to base composition, we identified a minimal 12-mer sequence, containing two sets of four contiguous guanosines separated by 3 to 5 bases, which conferred activity in vitro. Furthermore, inhibition of CD28 expression mediated by one representative active oligonucleotide, GR1, resulted in a concomitant dose-dependent diminution of anti-CD3/PMA-induced cytokine (IL-2, IFN-gamma, IL-8) production. Inhibition of IL-2 synthesis was dependent on CD28 expression, as GR1 failed to abrogate activated IL-2 production in a CD28-deficient T cell line, HUT 78. The inhibitory activity of GR1 reduced T cell proliferative responses in MLR and induced Ag-specific T cell hyporesponsiveness to alloantigens. Finally, s.c. administration of GR1 impaired in vivo contact hypersensitivity responses in mice and was associated with substantially decreased CD28 and IFN-gamma mRNA expression in lymph node cells. Collectively, our studies show the tolerogenic potential of oligonucleotide-mediated CD28 inhibition on T cell activation, in vitro and in vivo.
authors.affiliation: Immunology Laboratory, ICN Pharmaceuticals Inc., Costa Mesa, CA 92626, USA.
authors.forename: R C
authors.initials: RC
authors.lastname: Tam
authors.forename: U T
authors.initials: UT
authors.lastname: Phan
authors.forename: T
authors.initials: T
authors.lastname: Milovanovic
authors.forename: B
authors.initials: B
authors.lastname: Pai
authors.forename: C
authors.initials: C
authors.lastname: Lim
authors.forename: J
authors.initials: J
authors.lastname: Bard
authors.forename: L
authors.initials: L
authors.lastname: He
mesh_terms: D000818:Animals; D018106:CD28 Antigens / Q000096:biosynthesis* / Q000187:drug effects* / Q000378:metabolism; D003877:Dermatitis, Contact / Q000209:etiology / Q000276:immunology* / Q000517:prevention & control*; D006801:Humans; D007108:Immune Tolerance / Q000187:drug effects*; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D009841:Oligonucleotides / Q000494:pharmacology*; D013601:T-Lymphocytes / Q000187:drug effects*
chemical_list: D018106:CD28 Antigens; D009841:Oligonucleotides