title: Fluorosomes: a convenient new reagent to detect and block multivalent and complex receptor-ligand interactions.
abstract: We describe for the first time fluorescent virus-like particles decorated with biologically active mono- and multisubunit immune receptors of choice and the basic application of such fluorosomes (FSs) to visualize and target immune receptor-ligand interactions. For that purpose, human embryonic kidney (HEK)-293 cells were stably transfected with Moloney murine leukemia virus (MoMLV) matrix protein (MA) GFP fusion constructs. To produce FSs, interleukins (ILs), IL-receptors (IL-Rs), and costimulatory molecules were fused to the glycosyl phosphatidyl inositol anchor acceptor sequence of CD16b and coexpressed along with MoMLV group-specific antigen-polymerase (gag-pol) in MA::GFP(+) HEK-293 cells. We show that IL-2 decorated but not control-decorated FSs specifically identify normal and malignant IL-2 receptor-positive (IL-2R(+)) lymphocytes by flow cytometry. In addition to cytokines and costimulatory molecules, FSs were also successfully decorated with the heterotrimeric IL-2Rs, allowing identification of IL-2(+) target cells. Specificity of binding was proven by complete inhibition with nonlabeled, soluble ligands. Moreover, IL-2R FSs efficiently neutralized soluble IL-2 and thus induced unresponsiveness of T cells receiving full activation stimuli via T-cell antigen receptor and CD28. FSs are technically simple, multivalent tools for assessing and blocking mono- and multisubunit immune receptor-ligand interactions with natural constituents in a plasma membrane context.
authors.affiliation: Institute of Immunology, Center for Physiology, Pathophysiology and Immunology, Medical University of Vienna, A-1090 Borschkegasse 8A, Vienna, Austria.
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Kueng
authors.forename: Calin
authors.initials: C
authors.lastname: Manta
authors.forename: Daniela
authors.initials: D
authors.lastname: Haiderer
authors.forename: Victoria M
authors.initials: VM
authors.lastname: Leb
authors.forename: Klaus G
authors.initials: KG
authors.lastname: Schmetterer
authors.forename: Alina
authors.initials: A
authors.lastname: Neunkirchner
authors.forename: Ruth A
authors.initials: RA
authors.lastname: Byrne
authors.forename: Clemens
authors.initials: C
authors.lastname: Scheinecker
authors.forename: Peter
authors.initials: P
authors.lastname: Steinberger
authors.forename: Brian
authors.initials: B
authors.lastname: Seed
authors.forename: Winfried F
authors.initials: WF
authors.lastname: Pickl
mesh_terms: D002461:Cell Line, Transformed; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry*; D058851:GPI-Linked Proteins; D049452:Green Fluorescent Proteins / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D007376:Interleukin-2 / Q000032:analysis / Q000276:immunology*; D008024:Ligands; D016393:Lymphoma, B-Cell / Q000175:diagnosis / Q000276:immunology; D018613:Microscopy, Confocal; D008979:Moloney murine leukemia virus; D017452:Receptors, IgG; D015375:Receptors, Interleukin-2 / Q000032:analysis / Q000276:immunology*; D011994:Recombinant Proteins / Q000737:chemistry* / Q000235:genetics; D013601:T-Lymphocytes / Q000276:immunology; D014771:Virion / Q000737:chemistry* / Q000235:genetics
chemical_list: C428200:FCGR3B protein, human; D005456:Fluorescent Dyes; D058851:GPI-Linked Proteins; D007376:Interleukin-2; D008024:Ligands; D017452:Receptors, IgG; D015375:Receptors, Interleukin-2; D011994:Recombinant Proteins; D049452:Green Fluorescent Proteins