title: Synthesis of 99mTc-HYNIC-interleukin-12, a new specific radiopharmaceutical for imaging T lymphocytes.
abstract: OBJECTIVE
  Few radiopharmaceuticals have been described for the study of lymphocyte trafficking despite its high clinical relevance. The main difficulty resides in the identification of a suitable highly specific probe to target these cells. Interleukin-12 (IL12) is a heterodimeric cytokine which plays a key role in the development of Th(1) lymphocytes. The aims of the present study were to label IL12 with (99m)Tc, to evaluate its ability to bind to activated T lymphocytes in vitro and to study its biodistribution in normal mice and mice affected by autoimmune colitis.
  
  
  METHODS
  IL12 was derivatised with HYNIC-NHS and labelled with( 99m)Tc. An in vitro binding assay was performed on KIT225 cells, an IL12 receptor-positive cell line. (99m)Tc-IL12 biodistribution in normal mice was studied. Targeting experiments were performed in Balb/c mice injected with KIT225 cells and in mice with chemically induced chronic colitis.
  
  
  RESULTS
  (99m)Tc-IL12 labelling efficiency ranged between 75% and 85%. Saturation binding analysis revealed a K (d) of 2.09 nM. Results of biodistribution studies showed a predominant hepatic route of excretion. A significant degree of uptake in the spleen and thymus was also observed. In mice injected with KIT225 cells, (99m)Tc-IL12-specific uptake in these cells increased over time. (99m)Tc-IL12 also accumulated significantly in bowel of mice affected by TNBS-induced colitis showing T lymphocyte infiltration at histology, while accumulation in colon from control animals was negligible.
  
  
  CONCLUSIONS
  We conclude that this radiolabelled cytokine is a suitable candidate for specific in vivo imaging of T lymphocytes: a step forward in molecular imaging of immune-mediated processes.
authors.affiliation: Nuclear Medicine, Ospedale S. Andrea, 2nd Faculty of Medicine La Sapienza, Via di Grottarossa 1035, 00189 Roma, Italy.
authors.forename: Alessio
authors.initials: A
authors.lastname: Annovazzi
authors.forename: Calogero
authors.initials: C
authors.lastname: D'Alessandria
authors.forename: Elena
authors.initials: E
authors.lastname: Bonanno
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Mather
authors.forename: Bart
authors.initials: B
authors.lastname: Cornelissen
authors.forename: Christophe
authors.initials: C
authors.lastname: van de Wiele
authors.forename: Rudi A
authors.initials: RA
authors.lastname: Dierckx
authors.forename: Maurizio
authors.initials: M
authors.lastname: Mattei
authors.forename: Graziana
authors.initials: G
authors.lastname: Palmieri
authors.forename: Francesco
authors.initials: F
authors.lastname: Scopinaro
authors.forename: Alberto
authors.initials: A
authors.lastname: Signore
mesh_terms: D000818:Animals; D002460:Cell Line; D003092:Colitis / Q000000981:diagnostic imaging* / Q000378:metabolism* / Q000473:pathology; D005240:Feasibility Studies; D018664:Interleukin-12; D007553:Isotope Labeling / Q000379:methods; D008297:Male; D008657:Metabolic Clearance Rate; D051379:Mice; D009928:Organ Specificity; D015609:Organotechnetium Compounds; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000138:chemical synthesis / Q000493:pharmacokinetics; D013601:T-Lymphocytes / Q000737:chemistry / Q000000981:diagnostic imaging* / Q000378:metabolism*; D014018:Tissue Distribution
chemical_list: C513398:99mTc-HYNIC-interleukin-12; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; D018664:Interleukin-12