Human Schistosome Infection and Allergic Sensitisation

Abstract

Several field studies have reported an inverse relationship between the prevalence of helminth infections and that of allergic sensitisation/atopy. Recent studies show that immune responses induced by helminth parasites are, to an extent, comparable to allergic sensitisation. However, helminth products induce regulatory responses capable of inhibiting not only antiparasite immune responses, but also allergic sensitisation. The relative effects of this immunomodulation on the development of protective schistosome-specific responses in humans has yet to be demonstrated at population level, and the clinical significance of immunomodulation of allergic disease is still controversial. Nonetheless, similarities in immune responses against helminths and allergens pose interesting mechanistic and evolutionary questions. This paper examines the epidemiology, biology and immunology of allergic sensitisation/atopy, and schistosome infection in human populations.

Clinical morbidity associated with Schistosoma haematobium infection in pre‐school age children from an endemic district in Zimbabwe

“…Further follow-up with an ultrasound scan would be beneficial and further bio-chemical evaluation of the ascitic fluid would be very valuable [42]. Contrary to previous reports of an inverse relationship between schistosomiasis and atopy, infected children had a 6-fold higher odds of presenting with atopy [6,43,44]. It has been reported that schistosomiasis in PSAC is usually at low intensities and this might explain why we had a positive relation [5].…”

Antigenic cross‐reactivity between Schistosoma mansoni and peanut: a role for cross‐reactive carbohydrate determinants (CCDs) and implications for the hygiene hypothesis

“…Early schistosome infections, before patency, induce host immunity of the T helper type 1 (Th1) type involving interferon‐ γ and tumour necrosis factor‐ α . However, both acute S. mansoni infection and sensitization by allergens evoke similar immune responses that are Th2‐biased and characterized by the release of cytokines such as interleukin‐4 (IL‐4), IL‐5 and IL‐13, eosinophilia, and production of IgE antibodies . Chronic and advanced stages of infection are characterized also by Th2 immunity, but in a form that is ‘modified or ‘modulated’ and that evokes regulatory T‐cell activity and production of cytokines such as IL‐10 and transforming growth factor‐ β , which curb excessive inflammatory responses and so enhance survival of the parasite and perhaps that of the host also .…”

“…4 However, both acute S. mansoni infection and sensitization by allergens evoke similar immune responses that are Th2-biased and characterized by the release of cytokines such as interleukin-4 (IL-4), IL-5 and IL-13, eosinophilia, and production of IgE antibodies. 5,6 Chronic and advanced stages of infection are characterized also by Th2 immunity, but in a form that is 'modified or 'modulated' and that evokes regulatory T-cell activity and production of cytokines such as IL-10 and transforming growth factorb, which curb excessive inflammatory responses and so enhance survival of the parasite and perhaps that of the host also. 4,7,8 Incidentally, the characteristics of immunomodulated anti-parasite Th2 immunity are to some extent similar to those that pertain after successful immunotherapy of allergic diseases.…”

Study on Intestinal Helminth Parasites in School Children of Rangeli Municipality of Morang District in Eastern Nepal

“…The average intensity of infection of Ascaris lumbricoides and Trichuris trichiura rises in children aged 5-15 years and declines in intensity and frequency in adulthood [16] while hookworm often displays a firm rise in the intensity of infection with age which peaks up in adulthood [17].…”