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.

Glossary

Actinomycetes

Group of terrestrial or aquatic bacteria

Allergy

Hypersensitivity disorder of the immune system. Symptoms include red eyes, itchiness, runny nose, eczema or asthma attacks

Antibodies

Protein produced by the immune system to recognize or neutralize foreign molecules or micro-organisms

Antigen

Any substance inducing a response of the immune system

Autoimmune disease

Diseases arising as a result of an abnormal immune response by the body, directed against substances and tissues normally present in the body of the host

Clinically isolated syndrome

First episode of a demyelinating disease. It is the step prior to MS development

Commensal organisms

Organisms that obtain benefits from other organisms without producing any damage

Cytokines

Broad and loose category of small proteins that are important in cell signalling. They are released by several cells but particularly by cells of the immune system and affect the behaviour of other cells, or even of the releasing cell itself

Deworming

To give an antihelminthic drug to a person or animal to rid it of intestinal parasites

Demyelinating disease

Disease produced by the loss of myelin

Dendritic cell

Cells that recognize, process and present antigens to T cells, inducing their activation

Experimental autoimmune encephalomyelitis (EAE)

Animal model that mimics essential clinical and pathological characteristics of MS. It can be induced in different species such as rabbit, guinea pigs, rats, mice or monkeys

Gadolinium

Contrast medium used in magnetic resonance imaging studies to highlight abnormalities or disease process. In the brain, a gadolinium-positive lesion means the presence of inflammation

Gut microbiota

Also known as gut flora is a complex group of micro-organism species inhabiting the digestive tract of animals and humans and the largest reservoir of commensal micro-organisms

Helminths

Wormlike organisms living in and feeding on living hosts

Incidence

Measure of the risk of developing some new condition within a given time period

Interferon-γ

A type of cytokine that has most often a pro-inflammatory effect

Interleukins

A group of cytokines produced by white blood cells

Macrophage

Type of white blood cell that engulfs and digests cellular debris, foreign substances, microbes and cancer cells in a process called phagocytosis

Magnetic resonance imaging (MRI)

Also known as nuclear magnetic resonance imaging (NMRI) is a medical imaging technique used in radiology to investigate the anatomy and physiology of the body. MRI scanners use strong magnetic fields and radio waves to form images of the body without exposure to ionizing radiation

Multiple sclerosis

Inflammatory disease in which the insulating covers of nerve cells in the brain, spinal cord and optic nerve are damaged. This damage disrupts the ability of parts of the nervous system to communicate, resulting in a wide range of signs and symptoms

Mycobacteria

Widespread bacteria, typically living in water and food sources. Some, however, including tuberculosis and the leprosy bacteria, appear to be obligate parasites and are not found as free-living members of the genus

Natural killer cell

Type of cytotoxic lymphocytes that induce the death of tumour cells or virally infected cells

Prevalence

Proportion of a population found to have a condition, typically a disease or a risk factor

Saprophytes

Organisms obtaining nutrients from dead organic matter

T helper cell (Th)

Type of T cell that helps the activity of other immune cells by releasing T cell cytokines. These cells help, suppress or regulate immune responses

Transforming growth factor-β

Is a cytokine that controls proliferation, cellular differentiation and other functions in most cells