Helminth Immunoregulation and Multiple Sclerosis Treatment

Abstract

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system, affecting an estimated 2 million people worldwide, and is the second cause of neurological disability in young adults after traumatic brain injuries. Although the aetiology remains unknown, several lines of evidence support autoimmunity as playing a major role in disease development. MS incidence has significantly increased during the second half of the twentieth century. This has been attributed to changes in certain environmental factors, including a significant decline in exposure to infections, due to better public health practices. Epidemiological studies suggest autoimmune diseases, such as MS, are less frequent in individuals infected by certain kinds of parasites, particularly those called helminths. This observation has been tested in different autoimmune disease animal models in which mice colonized with helminths show protection from disease. Downmodulation of inflammatory responses resulting from helminth infection has sparked interest in exploring the potential clinical efficacy of establishing controlled infections in patients suffering from autoimmune diseases, using live parasitic worms, in an attempt to decrease disease severity. To date, clinical trials using helminth therapy in MS have been safety-oriented and small in size, seeking to reproduce and confirm epidemiological and experimental data. Clearly, longer studies, monitoring safety and objective outcome measures are necessary to assess this novel therapeutic strategy. Alternatively, identification of helminth-derived immunomodulatory molecules mimicking the protective effects of parasite infections might also help combat autoimmune diseases without undesired side effects.