The Intestinal Expulsion of the Roundworm Ascaris suum Is Associated with Eosinophils, Intra-Epithelial T Cells and Decreased Intestinal Transit Time

Abstract

Ascaris lumbricoides remains the most common endoparasite in humans, yet there is still very little information available about the immunological principles of protection, especially those directed against larval stages. Due to the natural host-parasite relationship, pigs infected with A. suum make an excellent model to study the mechanisms of protection against this nematode. In pigs, a self-cure reaction eliminates most larvae from the small intestine between 14 and 21 days post infection. In this study, we investigated the mucosal immune response leading to the expulsion of A. suum and the contribution of the hepato-tracheal migration. Self-cure was independent of previous passage through the liver or lungs, as infection with lung stage larvae did not impair self-cure. When animals were infected with 14-day-old intestinal larvae, the larvae were being driven distally in the small intestine around 7 days post infection but by 18 days post infection they re-inhabited the proximal part of the small intestine, indicating that more developed larvae can counter the expulsion mechanism. Self-cure was consistently associated with eosinophilia and intra-epithelial T cells in the jejunum. Furthermore, we identified increased gut movement as a possible mechanism of self-cure as the small intestinal transit time was markedly decreased at the time of expulsion of the worms. Taken together, these results shed new light on the mechanisms of self-cure that occur during A. suum infections.

Serum‐mediated Haemonchus contortus larval aggregation differs by larval stage and is enhanced by complement

“…When bound by peripheral blood mononuclear cells, H. contortus larval motility can be significantly restricted resulting in impaired movement . An inability to maintain positioning within the abomasum, such as the serum‐mediated larval aggregation that has been shown in this study, may aid peristaltic clearance of the parasite through the gastrointestinal tract …”

Mind the gaps in research on the control of gastrointestinal nematodes of farmed ruminants and pigs

“…However, particularly for A. suum , a small residual adult population may develop, and a small number of animals will continue to harbour large adult worm burdens which contribute markedly to the contamination of the environment with infective eggs (Nejsum et al., ). The immune‐reactive mechanisms appear to be similar to other helminth infections, namely a Th2‐biased response characterized by eosinophilia, mastocytosis and increased gut permeability and decreased transit time (Kringel, Iburg, Dawson, Aasted, & Roepstorff, ; Masure et al., ). Oesophagostomum dentatum differs in that the Th2‐response is markedly delayed and/or lower in intensity (Andreasen et al., ).…”

“…| 221 other helminth infections, namely a Th2-biased response characterized by eosinophilia, mastocytosis and increased gut permeability and decreased transit time (Kringel, Iburg, Dawson, Aasted, & Roepstorff, 2006;Masure et al, 2013). Oesophagostomum dentatum differs in that the Th2-response is markedly delayed and/or lower in intensity (Andreasen et al, 2015).…”

Soil-Transmitted Helminth Vaccines: Are We Getting Closer?

“…However, similar Th2-controlled effector mechanisms have been put forward for hookworm ( 12 ). For Ascaris , liver-stage immunity during the migratory stages of infection has been associated with oxidative phosphorylation and the production of reactive oxygen species ( 162 ), the lung-stage with an eosinophilia ( 163 , 164 ), and expulsion from the gut with increased muscle contractility ( 165 ).…”