T cells directed against different myelin antigen epitopes cooperate to induce autoimmune encephalomyelitis in mice

Abstract

Abstract Multiple Sclerosis (MS) is the most common demyelinating autoimmune disease of the central nervous system (CNS). Important insights have emerged into the pathogenic mechanisms that drive the inflammatory events and demyelination in MS, however, much less is known about the events initiating this disease. The murine model of MS, experimental autoimmune encephalomyelitis (EAE), is usually induced through injection with a high dose of single immunodominant peptides found on the myelin sheath of the CNS. Low doses of single peptide do not induce EAE or result in very low disease incidence. In individual MS patients, autoimmune T cell-reactivity is usually directed against multiple myelin antigen epitopes and fluctuates significantly over the course of disease. Thus, we hypothesize that MS is triggered by the emergence of autoreactive T cells directed against multiple myelin epitopes, which together synergize to induce the disease. To test this concept in an animal model of EAE, we explored the effect of induction of EAE using combinations of low dose peptides akin to a “multiple hit” mechanism implicated in other disease conditions. We found that EAE can be induced through the immunization of mice with a combination of low dose myelin peptides from different myelin proteins, which individually are suboptimal to induce disease. The disease observed after multi-peptide immunization is comparable or more severe than with optimal doses of peptide traditionally used to induce EAE. This research provides new insights into the potential mechanisms underlying the induction of MS and could lead to novel approaches for immunotherapy.