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

J Clin Immunol (2009) 29:637645 DOI 10.1007/s10875-009-9313-9

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

Galle Breton & Bader Yassine-Diab & Lillian Cohn &

Mohamed-Rachid Boulassel & Jean-Pierre Routy &

Rafick-Pierre Skaly & Ralph M. Steinman

Received: 5 April 2009 /Accepted: 9 June 2009 /Published online: 27 June 2009 # Springer Science + Business Media, LLC 2009

AbstractIntroduction 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. Methods 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.

Results 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.

Discussion 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.

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

AbbreviationsAPCs antigen-presenting cellsCFSE 5-(and-6)-carboxyfluorescein diacetate succinimidyl esterDCs dendritic cellsmDCs mature dendritic cellsiDCs immature dendritic cellsPBMCs peripheral blood mononuclear cellssiRNA small interfering RNAssRNA single-strand RNA

G. Breton : L. Cohn : R. M. Steinman (*)

Laboratory of Cellular Physiology and Immunology, Chris Browne Center for Immunology and Immune Diseases, The Rockefeller University,1230 York Avenue,New York, NY 10065, USAe-mail: [email protected]

B. Yassine-Diab : R.-P. SkalyLaboratoire dImmunologie, Centre de Recherche du Centre Hospitalier de lUniversit de Montral (CR-CHUM) Saint-Luc, Montral, QC H2X 1P1,...