title: Efficient nontoxic delivery of PD-L1 and PD-L2 siRNA into dendritic cell vaccines using the cationic lipid SAINT-18.
abstract: Dendritic cell (DC)-based vaccination is an appealing strategy to boost graft-versus-tumor immunity after allogeneic stem cell transplantation (allo-SCT), and thereby prevent or counteract tumor recurrence. By exploiting minor histocompatibility antigens (MiHA) presented on hematopoietic cells, donor CD8 T-cell immunity can be selectively targeted to patient's hematological tumor cells without the risk of inducing graft-versus-host disease. Previously, we demonstrated that silencing RNA (siRNA) of programmed death-ligand 1 (PD-L1) and PD-L2 on DCs markedly augments the expansion and function of MiHA-specific CD8 T cells. However, previously applied methods based on electroporation or lipid nanoparticles were either incompatible with target antigen mRNA delivery or required complex manufacturing compliant to Good Manufacturing Practice. Here, we investigated whether transfection using lipoplexes composed of PD-L1 and PD-L2 siRNAs plus SAINT-18:DOPE (ie, SAINT-RED) is an effective and feasible clinical-grade method in DC vaccine manufacturing. We observed that a single siRNA/SAINT-RED transfection resulted in efficient and long-term knockdown of the PD-1 ligands without affecting DC maturation or viability. Furthermore, we demonstrated that SAINT-RED can be heat sterilized without loss of function, facilitating its use in aseptic DC vaccine production. Finally, we showed that the established transfection method can be combined with target antigen mRNA or peptide loading to efficiently stimulate MiHA-specific T-cell expansion and cytokine production. Together, these findings indicate that the developed PD-L siRNA/SAINT-RED transfection protocol in combination with MiHA mRNA or peptide loading can be applied in the generation of clinical-grade DC vaccines to boost antitumor immunity after allo-SCT.
authors.affiliation: Departments of *Hematology †Laboratory Medicine-Laboratory of Hematology, Radboud University Medical Center, Nijmegen ‡Synvolux Therapeutics B.V., Groningen, The Netherlands.
authors.forename: Mieke W H
authors.initials: MW
authors.lastname: Roeven
authors.forename: Willemijn
authors.initials: W
authors.lastname: Hobo
authors.forename: Robbert
authors.initials: R
authors.lastname: van der Voort
authors.forename: Hanny
authors.initials: H
authors.lastname: Fredrix
authors.forename: Wieger J
authors.initials: WJ
authors.lastname: Norde
authors.forename: Kasper
authors.initials: K
authors.lastname: Teijgeler
authors.forename: Marcel H J
authors.initials: MH
authors.lastname: Ruiters
authors.forename: Nicolaas
authors.initials: N
authors.lastname: Schaap
authors.forename: Harry
authors.initials: H
authors.lastname: Dolstra
mesh_terms: D060890:B7-H1 Antigen / Q000037:antagonists & inhibitors* / Q000235:genetics; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D019496:Cancer Vaccines / Q000276:immunology*; D049109:Cell Proliferation; D002999:Clone Cells; D016207:Cytokines / Q000378:metabolism; D003713:Dendritic Cells / Q000276:immunology*; D020350:Graft vs Tumor Effect / Q000235:genetics; D018380:Hematopoietic Stem Cell Transplantation; D006801:Humans; D015778:Minor Histocompatibility Antigens / Q000276:immunology; D009369:Neoplasms / Q000628:therapy*; D061027:Programmed Cell Death 1 Ligand 2 Protein / Q000037:antagonists & inhibitors* / Q000235:genetics; D011726:Pyridinium Compounds / Q000737:chemistry; D034741:RNA, Small Interfering / Q000235:genetics*; D014162:Transfection / Q000379:methods*; D014184:Transplantation, Homologous
chemical_list: C532953:1-methyl-4-(9-dioleyl)methylpyridinium; D060890:B7-H1 Antigen; D019496:Cancer Vaccines; D016207:Cytokines; D015778:Minor Histocompatibility Antigens; C556977:PDCD1LG2 protein, human; D061027:Programmed Cell Death 1 Ligand 2 Protein; D011726:Pyridinium Compounds; D034741:RNA, Small Interfering