Cyclosporine enhances virally induced T-cell-mediated demyelination. The effect of cyclosporine on a demyelinating virus infection

Semliki Forest virus infection of adult mice results in a demyelinating meningoencephalomyelitis. Demyelination does not result from direct viral damage but from the activity of T lymphocytes. We have studied the effect of the immunosuppressant cyclosporine (Cs) on the outcome of this infection. Cs had no effect when given 5 days after the infection, and little effect when given 4 h after infection. When the Cs was given 48 h before infection there was a prolongation of the blood and brain virus titres, and a reduction in some mice of serum IgG anti-viral antibody synthesis, but an increase in the severity of the CNS inflammatory response and the demyelination. Consideration of these findings along with measurement of Cs levels in the serum and cerebrospinal fluid suggests that this drug does not cross the blood brain barrier.