MBP 85-99-SPECIFIC TCR REPERTOIRE IN DRB1*15 PATIENTS AFFECTED BY MULTIPLE SCLEROSIS

Objective: Multiple Sclerosis (MS) is an inflammatory, chronic, degenerative and demyelinating disease of the Central Nervous System (CNS). It is known that HLA-DR2 haplotype is a predisponent genetic factor to MS. The activation of myeline reactive T cells in the periphery lead to demyelination in CNS, through the induction of expression of adhesion molecules that allow their entry in the CNS through the Blood-Brain Barrier (BBB). We investigated the TR-β repertoire of T cells specific for epitope MBP85-99, immunodominat in HLA-DR2+ patients. Methods: We focused on DR2+ subjects: 7 untreated patients with diagnosis of active MS; 6 pazients with Clinically Isolated Syndrome (CIS); 6 MS patients in remission phase (REM); 7 healthy control subjects (HS). PBMC were cultured in vitro with or without MBP85-99 and with MBP111-129. We used the “Immunoscope” technique (a TRBV-TRBJ spectratyping) to investigate the TR-β repertoire of T cells. Magnetic separation of IL17+ and IFN+ populations was performed and their TR-β repertoire was analyzed. We performed the sequencing analysis of the more interesting TRBV-TRBJ rearrangements. Results: In a first analysis we identified 20 MBP85-99 specific TRBV-TRBJ rearrangements shared among MS DR2+ patients. The MBP111-129 specific rearrangements showed expansions unshared with the MBP85-99 epitope. Shared TCRs were studied in the IL17+ cells. As control, the same rearrangements were checked in the IFN+ cells and in polarized T cells from HS. The TCR repertoire usage in Th17 and Th1 cells is mutually exclusive. In one patient we founded 1 rearrangement specific to Th17 cells, while 25% of the investigated TCRs were specific for IFN+ cells. Longitudinal analyses in one patient with active MS and after 6 (REM) and 12 (relapse) months of therapy showed a correlation between TCR usage and the treatment efficacy. We performed the sequencing of the shared TCRs to confirm the similar response to MBP85-99 in the MS patients, not detectable in the CIS and healthy subjects. Conclusions: These data hint that the repertoire of TCR specific for MBP85-99 may be broader in CIS than in MS patients. In REM and during efficient treatment we observe a contraction of TCRs, in particular the ones secreting IFNgamma and IL17. We could be able to monitor the identified specific TCRs in the peripheral blood of the MS patients during the various relapsing-remitting phases of the disease and during therapy.