Characterization of the Antigen Specificity and TCR Repertoire, and TCR-Based DNA Vaccine Therapy in Myelin Basic Protein-Induced Autoimmune Encephalomyelitis in DA Rats

Like Lewis rats, DA rats are an experimental autoimmune encephalomyelitis (EAE)-susceptible strain and develop severe EAE upon immunization with myelin basic protein (MBP). However, there are several differences between the two strains. In the present study we induced acute EAE in DA rats by immunization with MBP and MBP peptides and examined the Ag specificity and TCR repertoire of encephalitogenic T cells. It was found that although immunization with MBP and a peptide corresponding to its 62–75 sequence (MBP62–75) induced clinical EAE, the responses of lymph node T cells isolated from MBP-immunized rats to MBP62–75 was marginal, indicating that this peptide contains major encephalitogenic, but not immunodominant, epitopes. The TCR analysis by CDR3 spectratyping of spinal cord T cells revealed that Vβ10 and Vβ15 spectratype expansion was always found in MBP62–75-immunized symptomatic rats. On the basis of these findings, we examined the encephalitogenicity of Vβ10- and Vβ15-positive T cells. First, the adoptive transfer experiments revealed that Vβ10-positive T line cells derived from MBP62–75-immunized rats induced clinical EAE in recipients. Second, administration of DNA vaccines encoding Vβ10 and Vβ15, alone or in combination, ameliorated MBP62–75-induced EAE. Collectively, it was strongly suggested that Vβ10- and Vβ15-positive T cells are encephalitogenic. Analyses of the Ag specificity and T cell repertoire of pathogenic T cells performed in this study provide useful information for designing specific immunotherapies against autoimmune diseases.