title: Interleukin 15 provides relief to CTLs from regulatory T cell-mediated inhibition: implications for adoptive T cell-based therapies for lymphoma.
abstract: OBJECTIVE
  Systemic administration of recombinant interleukin (IL)-2 is used to support the expansion and persistence of adoptively transferred antigen-specific CTLs in patients with cancer. However, IL-2 also expands regulatory T cells (Treg) that in turn impair the antitumor activity of CTLs. As recombinant IL-15 is approaching clinical applications, we assessed the effects of this cytokine on the proliferation and antitumor activity of CTLs in the presence of Tregs. We used the model of adoptive transfer of Epstein-Barr virus (EBV)-CTLs, as these cells induce responses in patients with EBV-associated Hodgkin lymphoma, and Tregs are frequently abundant in these patients.
  
  
  METHODS
  Tregs were isolated from the peripheral blood of healthy donors and patients with Hodgkin lymphoma or from Hodgkin lymphoma tumors and assessed for their ability to inhibit the proliferation and antitumor activity of EBV-CTLs in the presence of IL-15 or IL-2. Specific molecular pathways activated by IL-15 were also explored.
  
  
  RESULTS
  We found that in the presence of Tregs, IL-15, but not IL-2, promoted the proliferation, effector function, and resistance to apoptosis of effectors T cells and EBV-CTLs. IL-15 did not reverse or block Tregs but instead preferentially supported the proliferation of CTLs and effector T cells as compared with Tregs.
  
  
  CONCLUSIONS
  IL-15 selectively favors the survival, proliferation, and effector function of antigen-specific CTLs in the presence of Tregs, and thus IL-15, unlike IL-2, would have a significant impact in sustaining expansion and persistence of adoptively transferred CTLs in patients with cancer, including those infused with EBV-CTLs for treatment of EBV-associated malignancies.
authors.affiliation: Center for Cell and Gene Therapy, Baylor College of Medicine, The Methodist Hospital and Texas Children's Hospital, Houston, TX 77030, USA.
authors.forename: Serena K
authors.initials: SK
authors.lastname: Perna
authors.forename: Biagio
authors.initials: B
authors.lastname: De Angelis
authors.forename: Daria
authors.initials: D
authors.lastname: Pagliara
authors.forename: Sayyeda T
authors.initials: ST
authors.lastname: Hasan
authors.forename: Lan
authors.initials: L
authors.lastname: Zhang
authors.forename: Aruna
authors.initials: A
authors.lastname: Mahendravada
authors.forename: Helen E
authors.initials: HE
authors.lastname: Heslop
authors.forename: Malcolm K
authors.initials: MK
authors.lastname: Brenner
authors.forename: Cliona M
authors.initials: CM
authors.lastname: Rooney
authors.forename: Gianpietro
authors.initials: G
authors.lastname: Dotti
authors.forename: Barbara
authors.initials: B
authors.lastname: Savoldo
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D016923:Cell Death / Q000187:drug effects / Q000276:immunology; D002478:Cells, Cultured; D004854:Herpesvirus 4, Human / Q000276:immunology; D006689:Hodgkin Disease / Q000276:immunology / Q000628:therapy; D006801:Humans; D016130:Immunophenotyping; D016219:Immunotherapy, Adoptive; D019409:Interleukin-15 / Q000494:pharmacology*; D008213:Lymphocyte Activation / Q000187:drug effects / Q000276:immunology; D008223:Lymphoma / Q000276:immunology / Q000628:therapy; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects* / Q000276:immunology*; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*
chemical_list: D000970:Antineoplastic Agents; D019409:Interleukin-15