P145

Molecular determinants and transcriptional and epigenetic basis of glutamate dehydrogenase-PGE2-dependent Treg cell development

PRODJINOTHO F. 1,6, KUMAR N. 1, GRES V. 2, HENKEL F. 3, LACORCIA M. 1, DANDL R. 4, HASLBECK M. 4, SCHMIDT V. 5,6, WINKLER A. 5,6, SIKASUNGE C. 7, JAKOBSSON P. 8, HENNEKE P. 2,9, ESSER-VON BIEREN J. 3, PRAZERES DA COSTA C. 1,6

1 Institute for Medical Microbiology, Immunology and Hygiene, Technical University of Munich, Munich, Germany; 2 Institute for Immunodeficiency, Center for Chronic Immunodeficiency, Medical Center and Faculty of Medicine, University of Freiburg, Freiburg, Germany; 3 Center of Allergy and Environment (ZAUM), Technical University of Munich and Helmholtz Center Munich, Munich, Germany; 4 Department of Chemistry, Technical University Munich , Garching Bei Munich, Germany; 5 Department of Neurology, University Hospital, Klinikum rechts der Isar, Technical University Munich, Munich, Germany; 6 Center for Global Health, Technical University of Munich, Munich, Germany; 7 School of Veterinary Medicine, Department of Paraclinicals, University of Zambia, Lusaka, Zambia; 8 Rheumatology Unit, Department of Medicine, Karolinska University Hospital, Stockholm, Sweden; 9 Center for Pediatrics and Adolescent Medicine, Medical Center, University of Freiburg, Freiburg, Germany

Background and objectives: Distinct tissue-derived signals drive regulatory T cell (Treg) induction in tissues and shape their heterogeneity and functionality in chronic inflammation. In the brain inflammatory parasitic disease, neurocysticercosis (NCC), we have recently identified the parasite larval enzyme glutamate dehydrogenase (GDH) as the main driver of Treg in asymptomatic non-epileptic NCC by yet unknown mechanisms and characteristics. In this work, we aim to uncover the underlying mechanisms controlling GDH-modulated development of Tregs and the epigenetic landscape and transcriptional signatures associated with GDH-Treg cell identity and functionality.
 
Methods: Peripheral and brain immune cells from mice and healthy volunteers were pulsed with parasite- and recombinant expressed-GDH. Immune modulation and underlying mechanistic aspects were identified via adoptive transfer of larval GDH-treated DCs, and qPCR/FACS surrogate markers expression associated with LC/MS/MS profiling of eicosanoids and precursors and PGE2/IL-10 receptors antagonists. The mechanisms underlying Treg development, epigenetic landscape and transcriptional signatures associated with GDH-PGE2/IL-10-induced Tregs as well as FACS-sorted Tregs from NCC infected patients as compared to healthy individuals were addressed via sequencing technologies (ATACSeq, RNASeq).
 
Results: Mechanistically, we demonstrated that the parasite enzyme and recombinant expressed GDH instruct tolerogenic CD206+ monocytes and phagocytic Iba-1lo microglia to release IL-10 and the lipid mediator PGE2. These act in concert via their respective receptors EP2/4 and IL-10R, converting naive CD4+ T cells into brain homing CD25hiFoxP3+CTLA-4+CCR6+CCR7+ Tregs. Compared to sorted conventional T cells and classical Tregs, GDH-PGE2/IL-10-Tregs display distinct transcriptional and epigenetic signatures (e.g. JAK-STAT pathway) as similarly identified in asymptomatic NCC patients with pronounced expression of Helios, ST2 and IL-35 but significant reduction of CD226.
 
Conclusions: This work provides important insights into GDH-PGE2 axis as a novel regulator of tissue Treg cell development and reveals targets for therapeutic strategies that may enhance Treg expansion and immune tolerance in inflamed tissues and NCC.

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