Novel insights in the immune function of the vitamin D system: synergism with interferon-beta.

The 1,25(OH)(2)D(3) analog, TX527 (19-nor-14,20-bisepi-23-yne-1,25(OH)(2)D(3)), has an interesting dissociation profile between its potent immunomodulatory and its calcemic effects in vivo. The strong immunomodulatory potency of TX527 is reflected by its ability to attenuate experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis (MS). At present most MS patients are being treated with systemic IFN-beta administration. The aim of this study was to investigate whether combining IFN-beta with TX527 could empower its EAE-protective effects. We evaluated also combinations with the standard immunosuppressant cyclosporin A (CsA). EAE was induced in SJL mice by PLP immunization, treatment was started 3 days before disease induction. The TX527+IFN-beta combination resulted in significant disease protection which was superior to the effect of both treatment separately. No disease amelioration, even aggravation, was obtained with the IFN-beta+CsA combination. By adding TX527 to the IFN-beta+CsA combination near complete protection from EAE was achieved (100% protection from paralysis, mean maximal score of 1.8+/-1.5, both p<0.05 versus controls and all individual treatments). From these data we conclude that adding TX527 to an IFN-beta and/or CsA treatment results in clear additional immunomodulatory effects in EAE prevention and is therefore a potentially interesting candidate to be considered in clinical intervention trials in MS.