Sex-dependent treatment of chronic EAE with partial MHC class II constructs

Background: One of the main challenges in treating multiple sclerosis (MS) is reversing the effects of accumulated damage in the central nervous system (CNS) of progressive MS subjects. While most of the available drugs for MS subjects are anti-inflammatory and thus are limited to relapsing-remitting MS subjects, it is not clear to what extent their effects are capable of inducing axonal repair and remyelination in subjects with chronic MS. Methods: A chronic model of experimental autoimmune encephalomyelitis (EAE) was used to evaluate the potency of partial MHC (pMHC) class II constructs in treating progressive EAE. Results: We demonstrated an estrogen receptor alpha (ERα)-dependent increased dose requirement for effective treatment of female vs. male mice using pMHC. Such treatment using 100-μg doses of RTL342M or DRα1-mMOG-35-55 constructs significantly reversed clinical severity and showed a clear trend for inhibiting ongoing CNS damage, demyelination, and infiltration of inflammatory cells into the CNS in male mice. In contrast, WT female mice required larger 1-mg doses for effective treatment, although lower 100-μg doses were effective in ovariectomized or ERα-deficient mice with EAE. Conclusions: These findings will assist in the design of future clinical trials using pMHC for treatment of progressive MS.