title: Anti-melanoma vaccines engineered to simultaneously modulate cytokine priming and silence PD-L1 characterized usingex vivomyeloid-derived suppressor cells as a readout of therapeutic efficacy.
abstract: Efficacious antitumor vaccines strongly stimulate cancer-specific effector T cells and counteract the activity of tumor-infiltrating immunosuppressive cells. We hypothesised that combining cytokine expression with silencing programmed cell death ligand 1 (PD-L1) could potentiate anticancer immune responses of lentivector vaccines. Thus, we engineered a collection of lentivectors that simultaneously co-expressed an antigen, a PD-L1-silencing shRNA, and various T cell-polarising cytokines, including interferon γ (IFNγ), transforming growth factor β (TGFβ) or interleukins (IL12, IL15, IL23, IL17A, IL6, IL10, IL4). In a syngeneic B16F0 melanoma model and using tyrosinase related protein 1 (TRP1) as a vaccine antigen, we found that simultaneous delivery of IL12 and a PD-L1-silencing shRNA was the only combination that exhibited therapeutically relevant anti-melanoma activities. Mechanistically, we found that delivery of the PD-L1 silencing construct boosted T cell numbers, inhibitedin vivotumor growth and strongly cooperated with IL12 cytokine priming and antitumor activities. Finally, we tested the capacities of our vaccines to counteract tumor-infiltrating myeloid-derived suppressor cell (MDSC) activitiesex vivo. Interestingly, the lentivector co-expressing IL12 and the PD-L1 silencing shRNA was the only one that counteracted MDSC suppressive activities, potentially underlying the observed anti-melanoma therapeutic benefit. We conclude that (1) evaluation of vaccines in healthy mice has no significant predictive value for the selection of anticancer treatments; (2) B16 cells expressing xenoantigens as a tumor model are of limited value; and (3) vaccines which inhibit the suppressive effect of MDSC on T cells in ourex vivoassay show promising and relevant antitumor activities.
authors.affiliation: Division of infection and immunity; Rayne Institute; University College London ; London, UK ; Immunomodulation group; Navarrabiomed-Fundacion Miguel Servet ; Pamplona, Navarra, Spain.
authors.forename: Therese
authors.initials: T
authors.lastname: Liechtenstein
authors.affiliation: Division of infection and immunity; Rayne Institute; University College London ; London, UK ; Cancer Epigenetics group; Navarrabiomed-Fundacion Miguel Servet ; Pamplona, Navarra, Spain.
authors.forename: Noemi
authors.initials: N
authors.lastname: Perez-Janices
authors.affiliation: Cancer Epigenetics group; Navarrabiomed-Fundacion Miguel Servet ; Pamplona, Navarra, Spain.
authors.forename: Idoia
authors.initials: I
authors.lastname: Blanco-Luquin
authors.affiliation: Laboratory of Molecular and Cellular Therapy; Department of Physiology-Immunology; Vrije Universiteit Brussel ; Jette, Belgium.
authors.forename: Cleo
authors.initials: C
authors.lastname: Goyvaerts
authors.affiliation: Laboratory of Molecular and Cellular Therapy; Department of Physiology-Immunology; Vrije Universiteit Brussel ; Jette, Belgium.
authors.forename: Julia
authors.initials: J
authors.lastname: Schwarze
authors.affiliation: Laboratory of Molecular and Cellular Therapy; Department of Physiology-Immunology; Vrije Universiteit Brussel ; Jette, Belgium ; Department of Radiotherapy; Vrije Universiteit Brussel ; Jette, Belgium.
authors.forename: Ines
authors.initials: I
authors.lastname: Dufait
authors.affiliation: Division of infection and immunity; Rayne Institute; University College London ; London, UK.
authors.forename: Alessio
authors.initials: A
authors.lastname: Lanna
authors.affiliation: Department of Radiotherapy; Vrije Universiteit Brussel ; Jette, Belgium.
authors.forename: Mark De
authors.initials: M
authors.lastname: Ridder
authors.affiliation: Cancer Epigenetics group; Navarrabiomed-Fundacion Miguel Servet ; Pamplona, Navarra, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Guerrero-Setas
authors.affiliation: Laboratory of Molecular and Cellular Therapy; Department of Physiology-Immunology; Vrije Universiteit Brussel ; Jette, Belgium.
authors.forename: Karine
authors.initials: K
authors.lastname: Breckpot
authors.affiliation: Division of infection and immunity; Rayne Institute; University College London ; London, UK ; Immunomodulation group; Navarrabiomed-Fundacion Miguel Servet ; Pamplona, Navarra, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Escors
keywords: 142 3p, target sequence for the microRNA 142 3p; DC, dendritic cell; G-MDSC, granulocytic MDSC; IL, interleukin; IiOVA, MHC II invariant chain-ovalbumin; M-MDS, monocytic MDSC; MDSC; MDSC, myeloid-derived suppressor cell; MLR, mixed lymphocyte reaction; OVA, chicken ovalbumin; PD-1, programmed cell death 1; PD-L1; PD-L1, programmed cell death 1 ligand 1; T cell; TAA, tumor associated antigen; TCR, T cell receptor; TRP1, tyrosinase related protein 1;; TRP2, tyrosinase related protein 2; Th, T helper lymphocyte; immunotherapy; melanoma; p1, PD-L1-targeted microRNA; shRNA, short hairpin RNA