The impact of parasite infections on the course of multiple sclerosis.

Previously, we demonstrated that helminth-infected MS patients showed significantly lower number of relapses, reduced disability scores, and lower MRI activity compared to uninfected MS subjects. In the current study, 12 patients with diagnosis of relapsing remitting MS presenting parasite infections were prospectively followed during 90 months; due to exacerbation of helminth-infection symptoms after 63 months of follow-up, 4 patients received anti-parasite treatment. Helminth-infection control was associated with significant increase in clinical and radiological MS activities. Moreover, these patients showed significant increase in the number of IFN-γ and IL-12 producing cells, and a fall in the number of TGF-β and IL-10 secreting cells, as well as CD4+CD25+FoxP3+ Treg cells evident 3 months after anti-helminth treatment began. These new observations on parasite infections associated to MS indicate that parasite regulation of host immunity can alter the course of MS.