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
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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.
KeywordsDendritic cells PD-L1 PD-L2 siRNA HIV-1 gag CD8+ T cell
5-(and-6)-carboxyfluorescein diacetate succinimidyl ester
mature dendritic cells
immature dendritic cells
peripheral blood mononuclear cells
small interfering RNA
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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