Helminths and the IBD hygiene hypothesis

Abstract

Helminths are parasitic animals that have evolved over 100,000,000 years to live in the intestinal track or other locations of their hosts. Colonization of humans with these organisms was nearly universal until the early 20th century. More than 1,000,000,000 people in less developed countries carry helminths even today. Helminths must quell their host's immune system to successfully colonize. It is likely that helminths sense hostile changes in the local host environment and take action to control such responses. Inflammatory bowel disease (IBD) probably results from an inappropriately vigorous immune response to contents of the intestinal lumen. Environmental factors strongly affect the risk for IBD. People living in less developed countries are protected from IBD. The "IBD hygiene hypothesis" states that raising children in extremely hygienic environments negatively affects immune development, which predisposes them to immunological diseases like IBD later in life. Modern day absence of exposure to intestinal helminths appears to be an important environmental factor contributing to development of these illnesses. Helminths interact with both host innate and adoptive immunity to stimulate immune regulatory circuitry and to dampen effector pathways that drive aberrant inflammation. The first prototype worm therapies directed against immunological diseases are now under study in the United States and various countries around the world. Additional studies are in the advanced planning stage.

Establishment of nematode infection despite increased Th2 responses and immunopathology after selective depletion of Foxp3+ cells

“…It has been demonstrated that nematode infections may prevent and control undesired immune reactions [6][7][8][9][10][11][12]30]. Several studies showed that the beneficial effects of the infections could be mimicked by transfer of Treg derived from nematode-infected donors to naïve recipients rendering them refractory to the inflammatory disorders such as asthma and colitis [6,8,11,12].…”

“…However, such effects can be beneficial by downregulating inflammatory reactions to allergens and inflammatory disorders of the intestinal tract. Studies in animal models showed that helminths can suppress airway hyperreactivity and colitis [6][7][8] and nematodes have been used to efficiently treat human inflammatory bowel disease in clinical trials [9,10]. …”

Decreased Prevalence of Lymphatic Filariasis Among Subjects with Type-1 Diabetes

“…12,13 Several studies have found that persons infected with chronic parasitic worm infections have lower rates of autoimmune diseases than persons without these infections. 14,15 Currently, trials are under way using Trichuris suum and Necator americanus infection for the treatment of T1DM, multiple sclerosis, inflammatory bowel disease, asthma, and food allergies. 16 However, large-scale epidemiologic studies examining the association of helminth infections and the prevalence of autoimmunity are lacking.…”

Helmintos y microbiota: la comunidad del anillo

“…Numerosos trabajos han estudiado la interacción entre los parásitos y el sistema inmune (Weinstock et al, 2009), microbiota y sistema inmune (Clemente et al, 2012), pero aún se ha estudiado poco acerca de la interacción parasito-microbiota. Claramente los antibióticos juegan un papel fundamental en la comunicación entre la salud intestinal y el estatus fisiológico del hospedador (Ferrer et al, 2014).…”