title: siRNA silencing of PD-L1 and PD-L2 on dendritic cells augments expansion and function of minor histocompatibility antigen-specific CD8+ T cells.
abstract: Tumor relapse after human leukocyte antigen-matched allogeneic stem cell transplantation (SCT) remains a serious problem, despite the long-term presence of minor histocompatibility antigen (MiHA)-specific memory T cells. Dendritic cell (DC)-based vaccination boosting MiHA-specific T-cell immunity is an appealing strategy to prevent or counteract tumor recurrence, but improvement is necessary to increase the clinical benefit. Here, we investigated whether knockdown of programmed death ligand 1 (PD-L1) and PD-L2 on monocyte-derived DCs results in improved T-cell activation. Electroporation of single siRNA sequences into immature DCs resulted in efficient, specific, and long-lasting knockdown of PD-L1 and PD-L2 expression. PD-L knockdown DCs strongly augmented interferon-γ and interleukin-2 production by stimulated T cells in an allogeneic mixed lymphocyte reaction, whereas no effect was observed on T-cell proliferation. Moreover, we demonstrated that PD-L gene silencing, especially combined PD-L1 and PD-L2 knockdown, resulted in improved proliferation and cytokine production of keyhole limpet hemocyanin-specific CD4(+) T cells. Most importantly, PD-L knockdown DCs showed superior potential to expand MiHA-specific CD8(+) effector and memory T cells from leukemia patients early after donor lymphocyte infusion and later during relapse. These data demonstrate that PD-L siRNA electroporated DCs are highly effective in enhancing T-cell proliferation and cytokine production, and are therefore attractive cells for improving the efficacy of DC vaccines in cancer patients.
authors.affiliation: Department of Laboratory Medicine-Laboratory of Hematology, Radboud University NijmegenMedical Center, Nijmegen Center for Molecular Life Sciences, Nijmegen, The Netherlands.
authors.forename: Willemijn
authors.initials: W
authors.lastname: Hobo
authors.forename: Frans
authors.initials: F
authors.lastname: Maas
authors.forename: Niken
authors.initials: N
authors.lastname: Adisty
authors.forename: Theo
authors.initials: T
authors.lastname: de Witte
authors.forename: Nicolaas
authors.initials: N
authors.lastname: Schaap
authors.forename: Robbert
authors.initials: R
authors.lastname: van der Voort
authors.forename: Harry
authors.initials: H
authors.lastname: Dolstra
mesh_terms: D015703:Antigens, CD / Q000235:genetics* / Q000276:immunology; D060890:B7-H1 Antigen; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D049109:Cell Proliferation; D002478:Cells, Cultured; D016207:Cytokines / Q000276:immunology; D003713:Dendritic Cells / Q000276:immunology* / Q000378:metabolism; D020868:Gene Silencing; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics* / Q000276:immunology; D015778:Minor Histocompatibility Antigens / Q000276:immunology*; D061027:Programmed Cell Death 1 Ligand 2 Protein
chemical_list: D015703:Antigens, CD; D060890:B7-H1 Antigen; C423236:CD274 protein, human; D016207:Cytokines; D036341:Intercellular Signaling Peptides and Proteins; D015778:Minor Histocompatibility Antigens; C556977:PDCD1LG2 protein, human; D061027:Programmed Cell Death 1 Ligand 2 Protein