Immunoregulation And Immunointervention in Transplantation and Autoimmunity
Béatrice Charreau
Research Scientist

Engineer

In solid organ transplantation, the endothelial cells (ECs) of the graft express the donor's MHC and consequently are both trigger and target of allogeneic cellular and humoral responses. Our studies aim to better define the role of the graft endothelium in alloimmune responses and to understand the specific role of endothelial MICA and HLA-E in triggering NK and T cell activation or costimulation and in inducing unconventional T responses, respectively. Endothelial cell activation also contributes to inflammation which is a secondary effector of cellular and humoral rejection. Our work has identified the Notch signaling pathway and the SH2B3 adaptor protein as key players in the control of EC activation and graft vasculopathy. Our project currently develops new tools targeting the Notch and SH2B3 pathway for the diagnosis and treatment of microvascular inflammation.

Description

Ongoing Research Project

Endothelium and Immunity in Transplantation 

Béatrice Charreau (PI), Nicolas Jouand, Nicolas Petit, Nathalie Gérard, Chloé Coste, Antoine Bruguière

INSERM UMR1064, CRTI, CHU de Nantes, Université de Nantes, France.

Immune-mediated vascular lesions severely impair long term transplant outcome and still require specific evaluation and prevention. Initiating allograft vasculopathy, the damage caused to the graft’s endothelial cells (EC) by donor-specific antibodies (DSA) and CD8T cells triggers both acute and chronic allograft rejection. Understanding the initiating mechanisms of endothelial dysfunction and identify molecular targets to protect the endothelium and graft are the two objectives of the project. Previously we reported on the restricted expression and regulation of non-classical of HLA class I molecules by graft ECs and identified HLA-E and MICA as key players of endothelial immunity (Coupel et al., Blood 2007; Chauveau et al., JIN 2014) and as markers of vascular injury. Based on our findings, donor/recipient mismatch for the major MICA variant MICA A5.1 is an immunodominant factor involved in kidney transplant recipient (KTR) alloimmunization and graft function (Tonnerre et al., JASN, 2013) and in post-transplant BK polyomavirus reactivation (Tonnerre et al. J. Infectious Diseases 2016), that will be further characterized prospectively both in KTR cohorts and in cellular models. We also reported on alternative splice transcripts associated with 2 MICA alleles (MICA*015 and MICA*017) sharing a point mutation and we characterized the resulting MICA isoforms that display either agonist or antagonist NKG2D ligand functions (Gavalovsky et al., J. Immunol., 2016). These new MICA isoforms provide Innovative tools and approaches targeting the NKG2D immune checkpoint that we are currently developing (patent PCT/EP2014/064316, 04/07/2014; Gavlovsky et al., Hum Immunol. 2016). We also showed that HCMV-specific/HLA-E-restricted/CD8T cells include crossreactive effector memory CTL that damage allogeneic endothelium (Allard et al., PLos One, 2012). Our current study investigates the frequency, peptide specificity, time course, immunophenotype and functions of this non-conventional CD8T response (Jouand et al. 2017 in preparation) ex vivo in KTR. The possible harmful effect of HLA-E-restricted anti-HCMV response toward vascular injury and graft survival is also explored (patent PCT/ EP12305823.2, 10/07/2012).

 

Mechanistically, we have highlighted the regulatory functions in vascular ECs of the Notch pathway and of an adaptor protein, SH2B3 in intracellular signaling associated with rejection (Quillard et al. Biochem Pharmacol. 2010, IJMS 2013, Devalliere et al. Faseb J. 2012; Pabois et al. Biochem Pharmacol. 2014, 2016). A comprehensive analysis of Notch and SH2B3 signaling in the development of antibody-mediated rejection by controlling EC activation, endothelial/leukocyte crosstalk for cell recruitment and differentiation, as well as the respective involvement of alloantibodies and complement is being conducted in parallel in transplant biopsies and in cellular knock-in/-down models. Ultimately, this project should identify novel risk factors, predictive markers of rejection in KTR and new therapeutic targets.

 

As a specific tool, banked EC cultures from Transplant donors (n=183, 2005-2016), routinely and prospectively and stored (BiolCol DIVAT, CHU de Nantes) at the time of transplantation isolated in our group, are available for our translational studies. Our project relies on a network of dedicated scientific collaborations developed locally (UMR982, EFS de Nantes, Virology unit), but also at national (Hôpital Necker and Saint-Louis in Paris, Angers University) and international level (David Briscoe, Boston, Ben McFarland, Seattle). A partnership with the phytochemists (Sonas, Angers, Fr) also allows us to develop and assess on endothelial functions new bioactive natural molecules with anti-inflammatory and immunosuppressive effects (Rouger C. et al., J. Natural Products 2015, Plos One 2016). Our group currently participates in two “Laboratories of Excellence” (LabEx IGO and LabEx Transplantex) and CESTI IHU programs