Background:
Multiple sclerosis (MS) is a chronic demyelinating inflammatory disease of the central nervous system (CNS) characterized by damage to myelin sheaths secondary to an autoimmune process. The exact cause of MS remains elusive, but it is a multifactorial disease. Many environmental factors have been associated with the development of this disease affecting generally the young adults. Among them, Epstein-Barr virus (EBV) infection seems to play a key role in the MS pathogenesis. EBV seropositivity is very frequent in the general population (>90%). However, EBV infection manifested by infectious mononucleosis (IM) typically during adolescence or early adulthood is a strong MS factor of risk. EBV is well known to have a tropism for the B cells. The latter have recently been linked with MS pathogenesis particularly due to beneficial effects of B cells-depleting therapies used in MS patients. Recently, oxidized metabolites of cholesterol called oxysterols have been linked with neuroinflammation. They seem to have disturbed profiles in MS patients, to have proinflammatory actions and to promote immune cells trafficking into CNS. Interestingly, EBV has been proposed to induce expression of an oxysterol receptor named Epstein-Barr virus-induced gene 2 (EBI2), which is a G protein-coupled receptor. Nevertheless, it is still unknown if EBV triggers the EBI2 expression on B cells during neuroinflammation and if its expression contributes to MS disease.
Aim of the project:
The aim of this project is to assess the role of EBV in inducing EBI2 expression on various lymphocyte subtypes obtained from peripheral blood mononuclear cells (PBMC) in order to emphasize the role of environmental factors in neuroinflammation and especially in the MS pathogenesis.
Methods:
In this project, human blood samples have been taken from healthy donors. From them, the PBMC have been isolated for in vitro culture. PBMC have been further infected or not with EBV, more precisely with an EBV supernatant. The samples have been stained with anti- EBI2 antibody and specific lymphocyte surface markers. Finally, cells have been passed to the fluorescence-activated cell sorting (FACS) machine (LSR II) and the EBI2 expression was analysed on the different lymphocyte subsets at steady state and during EBV infection using a program processing flow cytometry data called FlowJo.
Results:
We studied the expression of EBI2 on different subtypes of B and T lymphocytes. We showed that EBI2 is expressed on both naïve (CD27-CD19+) and memory (CD27+CD19+) B cells. Furthermore, we demonstrated that EBI2 is upregulated under EBV infection on all B cells subtypes. However, the most consistent upregulation was on the B memory (CD27+CD19+) subpopulation.
Concerning the T cells, we observed EBI2 expression on all T cell subtypes tested (i.e. naïve and memory T-helper cells as well as cytotoxic T cells respectively CD3+CD45RA+, CD3+CD45RA- and CD3+CD8+), but no statistically significant EBI2 upregulation, under EBV infection, have been highlighted.