title: Long-term tolerance to factor VIII is achieved by administration of interleukin-2/interleukin-2 monoclonal antibody complexes and low dosages of factor VIII.
abstract: BACKGROUND
  Regulatory T cells (Tregs) play a pivotal role in regulating anti-factor VIII (FVIII) immune responses. Interleukin (IL)-2 mixed with a particular IL-2 monoclonal antibody (mAb; JES6-1) can induce the selective expansion of Tregs in vivo.
  
  
  METHODS
  In the prevention experiments, we treated mice with hemophilia A with IL-2/IL-2mAb complexes (three times per week) and concurrently with FVIII protein (80 U kg(-1) per week) for 4 weeks. Generation of anti-FVIII immune responses was examined afterward. Next, to induce long-term tolerance to FVIII, a series of treatment dosages and schedules for administering IL-2/IL-2mAb complexes and FVIII protein in mice with hemophilia A was evaluated.
  
  
  RESULTS
  Compared to control mice that were treated with only FVIII, which produced high-titer anti-FVIII antibodies, mice treated with IL-2/IL-2mAb complexes plus FVIII produced no antibodies. A marked seven-fold increase in CD4(+) CD25(+) Foxp3(+) Helios(+) natural Tregs was maintained for 4 weeks in blood, spleen, and lymph nodes and then dropped to normal levels within the next 10 days. The suppressive functions of expanded Tregs were demonstrated with suppressive, proliferative, and cytokine assays. The administration of anti-CD25 mAb (PC-61) blocked this protective effect, confirming the involvement of Tregs in suppressing anti-FVIII immune responses. Importantly, administration of IL-2/IL-2mAb complexes (three times per week for 8 weeks) combined with contiguous weekly injections of low-dosage FVIII protein (20 U kg(-1) per week for 18 weeks) not only abrogated the formation of anti-FVIII antibodies but also induced long-term tolerance to FVIII.
  
  
  CONCLUSIONS
  Treatment with IL-2/IL-2mAb complexes is highly promising for the induction and maintenance of FVIII-specific tolerance after FVIII protein replacement therapy.
authors.affiliation: Center for Immunity and Immunotherapies, Seattle Children's Research Institute, Seattle, WA, USA.
authors.forename: C L
authors.initials: CL
authors.lastname: Liu
authors.forename: P
authors.initials: P
authors.lastname: Ye
authors.forename: J
authors.initials: J
authors.lastname: Lin
authors.forename: D
authors.initials: D
authors.lastname: Djukovic
authors.forename: C H
authors.initials: CH
authors.lastname: Miao
mesh_terms: D000818:Animals; D000906:Antibodies / Q000097:blood*; D000911:Antibodies, Monoclonal / Q000008:administration & dosage*; D002478:Cells, Cultured; D003029:Coagulants / Q000008:administration & dosage* / Q000276:immunology; D004195:Disease Models, Animal; D004334:Drug Administration Schedule; D005169:Factor VIII / Q000008:administration & dosage* / Q000235:genetics / Q000276:immunology; D006467:Hemophilia A / Q000097:blood / Q000188:drug therapy* / Q000235:genetics / Q000276:immunology; D006801:Humans; D007108:Immune Tolerance / Q000187:drug effects*; D007376:Interleukin-2 / Q000008:administration & dosage* / Q000276:immunology; D053645:Interleukin-2 Receptor alpha Subunit / Q000037:antagonists & inhibitors / Q000276:immunology; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D050378:T-Lymphocytes, Regulatory / Q000187:drug effects / Q000276:immunology; D013997:Time Factors
chemical_list: D000906:Antibodies; D000911:Antibodies, Monoclonal; D003029:Coagulants; C508018:Il2ra protein, mouse; D007376:Interleukin-2; D053645:Interleukin-2 Receptor alpha Subunit; C584092:PC61 monoclonal antibody; C078147:F8 protein, human; D005169:Factor VIII
keywords: IL-2/IL-2mAb complexes; factor VIII; hemophilia; immune tolerance; immunomodulation; regulatory T cells