Abstract 13051: Profiling CD8+ T Cell Activation in Experimental Models With LDL-R Deficiency and in Patients With Familial Hypercholesteroleamia

Introduction and Hypothesis: Familial Hypercholesterolaemia (FH) is a rare genetic disease characterized by elevated plasma cholesterol levels, xanthomas, overt atherosclerosis and premature cardiovascular death. HoFH and severe HeFH present an elevated inflammatory burden and poorly responsive to therapeutics such as anti-PCSK9 monoclonal antibodies. Therefore, innovative approaches to diagnose the severity of the disease and control the over-activation of the immune-inflammatory response in the arterial wall of FH patients should be studied to improve the management of this genetic disease. Here we profiled the activation of CD8+ T lymphocytes from experimental models and with patients with clinical diagnosis of FH.

Methods: Immunophenotypic characterization of T cells from WT and LDLR KO mice was performed in vitro and in vivo coupled to proteomics and WB analysis on isolated T cells. CD8 T cell response in FH patients, carrying mutations in the LDLR gene, was profiled.

Results: LDLR mRNA expression increased after in vitro activation of CD8, but not CD4 T cells, suggesting a different regulation of cholesterol homeostasis between T cell subsets. LDLR deficiency mainly affected CD8 T cell activation as demonstrated by reduced in vitro and in vivo proliferation and cytokine production after ovalbumin vaccination of LDL-R KO T cells compared to their wild type counterpart. The addition of LDL to serum free media increased CD8 proliferation in WT but not in KO CD8 T cells. Proteomic and WB analysis showed that this phenotype is the consequence of reduced mTORC1 activation and impaired lysosomal organization. The proliferation of CD8 T cells from FH patients was less pronounced compared to sex- and age-matched controls. In addition, CD8 T cells from FH vaccinated for seasonal influenza were tested in vitro with virus-derived peptides, showing a decreased granzyme production compared to CD8 from vaccinated controls.

Conclusions: LDLR plays a critical role in regulating the immunometabolic reprogramming of activated CD8 T cells by fuelling the cholesterol-lysosome-mTORC1 axis. Acknowledgments: This study is supported by a Grant from the Italian Ministry of Health: RF-2019-12370896