Antigenic epitopes of MAP2694 homologous to T-cell receptor gamma-chain are highly recognized in multiple sclerosis Sardinian patients

Mycobacterium avium ss. paratuberculosis (MAP) is an intracellular pathogen recently associated with multiple sclerosis (MS). Aiming to identify immunodominant epitopes belonging to MS related protein MAP2694 (UniProt accession no. Q73WG6), we investigated the binding activity of selected peptides against MS Sardinian sera. An overlapping 9-mers peptide library was synthesized spanning the entire aminoacidic sequence of the protein. Peripheral blood was collected from 47 MS patients and 42 sex and age matched healthy volunteers and subjected to enzyme-linked immunosorbent assay (ELISA) in order to investigate the reaction against the linear peptides generated. Two out of 58 synthetic 9-mers were strongly recognized by MS patients’ antibodies compared to controls. A competitive inhibition assay demonstrated that these two epitopes are immunodominant antibody targets within MAP2694 protein, as sera pre-adsorbed with these peptides were able to significantly block the antibody reaction to the MAP2694 protein, even if at a lesser extent than MAP2694 protein itself