title: Targeting activated lymphocytes with an entirely human immunotoxin analogue: human pancreatic RNase1-human IL-2 fusion.
abstract: A hybrid human protein was produced in E. coli by fusing the genes encoding human pancreatic RNase1 (hpRNase1) and human IL-2 (hIL-2). The recombinant hpRNase1-hIL-2 inhibited protein synthesis in HTLV-1-infected, malignant T cells, which hyperproduce high affinity IL-2 receptors, with an IC(50)of 2x10(-8) M, whereas no inhibition was detectable in control cells with lower affinity receptors. HpRNase1 alone had an IC(50)of almost 10(-3) M. A molar excess of hIL-2 blocked the protein synthesis inhibition dose-dependently. In a human mixed lymphocyte culture, hpRNase1-hIL-2 inhibited the proliferation of responder cells with potency comparable to that of cyclosporine, while non-effective doses of FK506 importantly improved its potency. Despite its short half-life in animals, hpRNase1-hIL-2 rapidly enters cells in a few minutes and arrests the protein translation in less than 10 h. Thus, hpRNase1-hIL-2 may be useful to selectively eliminate activated lymphocytes hyperproducing high affinity IL-2 receptors, as in allograft rejection, graft-versus-host disease, autoimmune disorders, adult T cell leukaemia and other lymphoproliferative or retroviral malignancies including HIV infection, without inducing general immunosuppression. As an entirely human "immunotoxin analogue" it may alleviate the dose limiting toxicity and immunogenicity of conventional immunotoxins.
authors.affiliation: Department of Surgery, School of Medicine, Keio University, Tokyo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Psarras
authors.forename: M
authors.initials: M
authors.lastname: Ueda
authors.forename: M
authors.initials: M
authors.lastname: Tanabe
authors.forename: M
authors.initials: M
authors.lastname: Kitajima
authors.forename: S
authors.initials: S
authors.lastname: Aiso
authors.forename: S
authors.initials: S
authors.lastname: Komatsu
authors.forename: M
authors.initials: M
authors.lastname: Seno
mesh_terms: D000818:Animals; D002455:Cell Division / Q000187:drug effects; D003001:Cloning, Molecular; D004926:Escherichia coli; D015368:Human T-lymphotropic virus 1 / Q000502:physiology*; D006801:Humans; D007376:Interleukin-2 / Q000493:pharmacokinetics / Q000494:pharmacology / Q000633:toxicity*; D015458:Leukemia, T-Cell; D008213:Lymphocyte Activation / Q000187:drug effects / Q000502:physiology*; D007959:Lymphocyte Culture Test, Mixed; D016399:Lymphoma, T-Cell; D008657:Metabolic Clearance Rate; D051381:Rats; D011917:Rats, Inbred Lew; D015375:Receptors, Interleukin-2 / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000493:pharmacokinetics / Q000633:toxicity; D012259:Ribonuclease, Pancreatic / Q000493:pharmacokinetics / Q000494:pharmacology / Q000633:toxicity*; D013601:T-Lymphocytes / Q000187:drug effects* / Q000276:immunology / Q000821:virology; D014407:Tumor Cells, Cultured
chemical_list: D007376:Interleukin-2; D015375:Receptors, Interleukin-2; D011993:Recombinant Fusion Proteins; C412343:recombinant fusion protein RNase1-IL-2; D012259:Ribonuclease, Pancreatic