HTLV-1-mediated Imprinting of Dendritic cell Immune Functions – ViralImprint

Chronic infection by HTLV-1 leads to cancer and/or neurodegenerative disorder and increases the risk of co-infections. Immune dysfunctions have been repeatedly reported in asymptomatic HTLV-1 carriers, indicating that chronic infection induces systemic effects and hampers the ability of the immune system to respond adequately. Indeed, Dendritic cells (DCs) from infected individuals exhibit a defect in NF-kB-driven maturation suggesting a lower ability to initiate HTLV-1 specific T cell responses. How these defects are induced by HTLV-1 is not known, yet crucial to define efficient therapies. The goal of this project is to dissect how exposure to HTLV-1 imprints dendritic cell functions in initiating immune responses. The central hypothesis is that exposure to HTLV-1 induces a poor capacity of DCs to induce T-cell responses, by decreasing the ability of DCs to respond to danger signals and by interfering with antigen (Ag) presentation and induction of pro-inflammatory cytokines.
Our project has the following specific aims:
1-Characterizing the mechanisms of HTLV-1-induced DC low responsiveness We will define the complete landscape of DC alterations induced upon their exposure to and/or infection by HTLV-1, before and after DC re-stimulation with TLR agonists. We will use flow cytometry to investigate in depth the phenotype of HTLV-1-exposed or infected DCs, as well as phosphoflow cytometry and RNA-seq to identify the underlying transcriptional landscape. We will identify which viral regulatory/auxiliary proteins can recapitulate these alterations using ectopic expression in DC.
2-Elucidating the mechanisms of HTLV-1 manipulation of innate signalling in DCs Because many functions of DC converge towards NFkB and IRF3 signalling, pathways specifically targeted by HTLV-1 proteins in T-cells, we will monitor these signalling in HTLV-1-exposed DCs. We will analyse the phosphorylation of pathway intermediates using western blotting, the nuclear translocation of NFkB/IRF3 using imaging and imaging cytometry and the ability of DC to secrete NFkB/IRF3-induced proteins using ELISA. We will determine the interaction network of viral regulatory/auxiliary proteins in DC using ectopic expression and immunoprecipitation of Flag-tagged proteins followed by mass spectrometry.
3-Addressing the consequences of HTLV-1-mediated DC alterations on T cell activation We will define the extent to which HTLV-1 exposure of DC translates into dysfunctional T cell activation and determine how viral proteins interfere with MHC biology. We will screen the effect of HTLV-1 proteins on antigen (Ag) presentation using model APC expressing viral proteins and model Ag before their co-culture with cognate Ag-specific T-cell clones and we will monitor by flow cytometry and ELISA the activation of T-cells. We will follow the traffic of MHC proteins in model APC expressing viral proteins and we will define at the molecular level how HTLV-1 viral proteins interfere with the processing and presentation of Ag.
Our consortium is built around 2 partners with strong and complementary expertise on virus / innate immunity interactions and molecular virology (Partner 1), and antigen presentation and activation of T cell responses (Partner 2). This project is supported by preliminary data generated via on going collaborations between our groups. The consortium’s complementarity will allow us to synergistically combine state-of-the-art approaches available in either location, in an original and multi-perspective approach of the HTLV-1 / DC interplay. The expected outcome is a comprehensive characterization of the consequences of HTLV-1 and DC interactions and of the underlying mechanisms, resulting in immune dysfunctions observed throughout the chronic infection. We will bring insights into the cell biology of DCs, and in particular on the signaling cascades of innate immunity and the pathways of viral Ag presentation manipulated by viruses.