Transient anti-CD154-mediated immunotherapy of ongoing relapsing experimental autoimmune encephalomyelitis induces long-term inhibition of disease relapses.

Relapsing experimental autoimmune encephalomyelitis (R-EAE) is a Th1-mediated central nervous system (CNS) autoimmune disease with pathology similar to that of relapsing-remitting multiple sclerosis. Among recent therapeutic approaches to prevent or treat relapsing disease is the strategic blockade of the CD154-CD40 ligand pair interactions. We have previously shown that CD154 blockade at the peak of acute disease can, in the short term, inhibit spontaneous disease relapse and this is at least partly associated with the inhibition of T cell effector function and blockade of inflammatory cell recruitment to and/or retention in the CNS. However, little is understood about the long-term effects of CD154 blockade in the inhibition of immune responses to encephalitogenic antigens. Here we demonstrate that transient anti-CD154 blockade of CD154-CD40 interactions at the peak of acute phase of R-EAE resulted in significant long-term inhibition (by >80%) of clinical relapses and that clinical disease in those mice that did relapse was reduced in duration and severity compared to control antibody-treated mice. Additionally, we show that this strategy permanently inhibits DTH responses of T cells specific for relapse-associated encephalitogenic epitopes. Thus, transient CD154 blockade during ongoing disease has a long-term therapeutic efficacy in preventing disease relapses.