Journal of Clinical Immunology

, Volume 29, Issue 5, pp 637–645 | Cite as

siRNA Knockdown of PD-L1 and PD-L2 in Monocyte-Derived Dendritic Cells only Modestly Improves Proliferative Responses to Gag by CD8+ T Cells from HIV-1-Infected Individuals

  • Gaëlle Breton
  • Bader Yassine-Diab
  • Lillian Cohn
  • Mohamed-Rachid Boulassel
  • Jean-Pierre Routy
  • Rafick-Pierre Sékaly
  • Ralph M. Steinman



Due to their capacity to elicit and regulate immunity, dendritic cells (DCs) are important targets to improve vaccination. Knowing that programmed death-1 (PD-1) high virus-specific T cells become functionally exhausted during chronic exposure to human immunodeficiency virus-1 (HIV-1), the development of a therapeutic DC-based HIV-1 vaccine might include strategies that downregulate PD-L1 and PD-L2 counter-receptors.


After showing that monocyte-derived DCs rapidly upregulated PD-L1 and PD-L2 expression upon maturation with a variety of stimuli, e.g., Toll-like receptor ligands and cytokines, we determined that PD-L1 and PD-L2 expression could be knocked down by electroporation of a single small interfering RNA (siRNA) sequence twice at the monocyte and immature stages of DC development. This knockdown approached completion and was specific and lasting for several days.


We then added the PD-L1 and PD-L2 silenced monocyte-derived DCs to peripheral blood mononuclear cells from HIV-1-infected individuals along with pools of 15-mer HIV-1 Gag p24 peptides. However, in cultures from six patients, there was only a modest enhancing effect of PD-L1 and PD-L2 silencing on CD8+ T cell proliferative responses to the DCs.


These findings suggest that, in monocyte-derived DCs, additional strategies than PD-L1 or PD-L2 blockade will be needed to improve the function of PD-1 high T cells.


Dendritic cells PD-L1 PD-L2 siRNA HIV-1 gag CD8+ T cell 



antigen-presenting cells


5-(and-6)-carboxyfluorescein diacetate succinimidyl ester


dendritic cells


mature dendritic cells


immature dendritic cells


peripheral blood mononuclear cells


small interfering RNA


single-strand RNA


Toll-like receptors


programmed death-1


long-term nonprogressors



We thank Henry A. Zebroski (Proteomics Resource Center, The Rockefeller University) for synthesizing the Ova peptide library. This work was supported by a grant awarded to Argos Therapeutics from the National Institutes of Health (NIAID-DIADS-BAA-06-19). R.-P.S. is the Canada Research Chair in Human Immunology. J.-P.R. is a clinician–scientist supported by Fonds de Recherche en Santé du Québec.


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Copyright information

© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  • Gaëlle Breton
    • 1
  • Bader Yassine-Diab
    • 2
    • 3
    • 4
  • Lillian Cohn
    • 1
  • Mohamed-Rachid Boulassel
    • 6
  • Jean-Pierre Routy
    • 5
    • 6
  • Rafick-Pierre Sékaly
    • 2
    • 3
    • 4
    • 5
  • Ralph M. Steinman
    • 1
  1. 1.Laboratory of Cellular Physiology and Immunology, Chris Browne Center for Immunology and Immune DiseasesThe Rockefeller UniversityNew YorkUSA
  2. 2.Laboratoire d’ImmunologieCentre de Recherche du Centre Hospitalier de l’Université de Montréal (CR-CHUM) Saint-LucMontréalCanada
  3. 3.Laboratoire d’Immunologie, Département de Microbiologie et d’ImmunologieUniversité de MontréalMontréalCanada
  4. 4.INSERM U743, CR-CHUMUniversité de MontréalMontréalCanada
  5. 5.Department of Microbiology and ImmunologyMcGill UniversityMontréalCanada
  6. 6.Immunodeficiency Service and Division of Hematology, Royal Victoria HospitalMcGill University Health Centre, McGill UniversityMontréalCanada

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