Response of intestinal epithelial cells to Trichuris suis excretory-secretory products and the influence on Campylobacter jejuni invasion under in vitro conditions

Co-operative suppression of inflammatory responses in human dendritic cells by plant proanthocyanidins and products from the parasitic nematode Trichuris suis

Interactions between dendritic cells (DCs) and environmental, dietary and pathogen antigens play a key role in immune homeostasis and regulation of inflammation. Dietary polyphenols such as proanthocyanidins (PAC) may reduce inflammation, and we therefore hypothesized that PAC may suppress lipopolysaccharide (LPS) -induced responses in human DCs and subsequent T helper type 1 (Th1) -type responses in naive T cells. Moreover, we proposed that, because DCs are likely to be exposed to multiple stimuli, the activity of PAC may synergise with other bioactive molecules that have anti-inflammatory activity, e.g. soluble products from the helminth parasite Trichuris suis (TsSP). We show that PAC are endocytosed by monocyte-derived DCs and selectively induce CD86 expression. Subsequently, PAC suppress the LPS-induced secretion of interleukin-6 (IL-6) and IL-12p70, while enhancing secretion of IL-10. Incubation of DCs with PAC did not affect lymphocyte proliferation; however, subsequent interferon-γ production was markedly suppressed, while IL-4 production was unaffected. The activity of PAC was confined to oligomers (degree of polymerization ≥ 4). Co-pulsing DCs with TsSP and PAC synergistically reduced secretion of tumour necrosis factor-α, IL-6 and IL-12p70 while increasing IL-10 secretion. Moreover, both TsSP and PAC alone induced Th2-associated OX40L expression in DCs, and together synergized to up-regulate OX40L. These data suggest that PAC induce an anti-inflammatory phenotype in human DCs that selectively down-regulates Th1 response in naive T cells, and that they also act cooperatively with TsSP. Our results indicate a novel interaction between dietary compounds and parasite products to influence immune function, and may suggest that combinations of PAC and TsSP can have therapeutic potential for inflammatory disorders.

A role for the pattern recognition receptor Nod2 in promoting recruitment of CD103+ dendritic cells to the colon in response to Trichuris muris infection

The ability of the colon to generate an immune response to pathogens, such as the model pathogen Trichuris muris, is a fundamental and critical defense mechanism. Resistance to T. muris infection is associated with the rapid recruitment of dendritic cells (DCs) to the colonic epithelium via epithelial chemokine production. However, the epithelial-pathogen interactions that drive chemokine production are not known. We addressed the role of the cytosolic pattern recognition receptor Nod2. In response to infection, there was a rapid influx of CD103(+)CD11c(+) DCs into the colonic epithelium in wild-type (WT) mice, whereas this was absent in Nod2(-/-) animals. In vitro chemotaxis assays and in vivo experiments using bone marrow chimeras of WT mice reconstituted with Nod2(-/-) bone marrow and infected with T. muris demonstrated that the migratory function of Nod2(-/-) DCs was normal. Investigation of colonic epithelial cell (CEC) innate responses revealed a significant reduction in epithelial production of the chemokines CCL2 and CCL5 but not CCL20 by Nod2-deficient CECs. Collectively, these data demonstrate the importance of Nod2 in CEC responses to infection and the requirement for functional Nod2 in initiating host epithelial chemokine-mediated responses and subsequent DC recruitment and T-cell responses following infection.

Alterations in the porcine colon microbiota induced by the gastrointestinal nematode Trichuris suis

Helminth parasites ensure their survival by regulating host immunity through mechanisms that dampen inflammation. These properties have recently been exploited therapeutically to treat human diseases. The biocomplexity of the intestinal lumen suggests that interactions between the parasite and the intestinal microbiota would also influence inflammation. In this study, we characterized the microbiota in the porcine proximal colon in response to Trichuris suis (whipworm) infection using 16S rRNA gene-based and whole-genome shotgun (WGS) sequencing. A 21-day T. suis infection in four pigs induced a significant change in the composition of the proximal colon microbiota compared to that of three parasite-naive pigs. Among the 15 phyla identified, the abundances of Proteobacteria and Deferribacteres were changed in infected pigs. The abundances of approximately 13% of genera were significantly altered by infection. Changes in relative abundances of Succinivibrio and Mucispirillum, for example, may relate to alterations in carbohydrate metabolism and niche disruptions in mucosal interfaces induced by parasitic infection, respectively. Of note, infection by T. suis led to a significant shift in the metabolic potential of the proximal colon microbiota, where 26% of all metabolic pathways identified were affected. Besides carbohydrate metabolism, lysine biosynthesis was repressed as well. A metabolomic analysis of volatile organic compounds (VOCs) in the luminal contents showed a relative absence in infected pigs of cofactors for carbohydrate and lysine biosynthesis, as well as an accumulation of oleic acid, suggesting altered fatty acid absorption contributing to local inflammation. Our findings should facilitate development of strategies for parasitic control in pigs and humans.

Helminthic therapy: improving mucosal barrier function

The epidemiology of autoimmune diseases and helminth infections led to suggestions that helminths could improve inflammatory conditions, which was then tested using animal models. This has translated to clinical investigations aimed at the safe and controlled reintroduction of helminthic exposure to patients suffering from autoimmune diseases (so-called 'helminthic therapy') in an effort to mitigate the inflammatory response. In this review, we summarize the results of recent clinical trials of helminthic therapy, with particular attention to mechanisms of action. Whereas previous reviews have emphasized immune regulatory mechanisms activated by helminths, we propose that enhancement of mucosal barrier function may have an equally important role in improving conditions of inflammatory bowel diseases.

Development of improved methods for delivery of Trichuris muris to the laboratory mouse

Murine immunological responses to experimental infection with Trichuris muris and the effects of the resident microbiota on these responses are of increasing interest. For these studies, accurate dose delivery and improved sterilization of inocula are essential to prevent co-infection with unknown contaminants. We found that washing T. muris eggs with antibiotics may not be sufficient for sterilization of inocula. However, washing eggs in 6.25% hypochlorite/bleach eliminated bacteria and fungi, as determined by culture and PCR, did not harm viable T. muris eggs and reduced the number of non-viable eggs in the inocula. A hatching assay and propidium iodide staining method were developed and found to increase the accuracy for assessing T. muris egg viability prior to infection for rapid dose evaluation. In addition, metal gavage feeding needles increased the accuracy and precision of the dose delivered to the mice compared to flexible rubber tubes. These methods will improve experimental Trichuris studies by decreasing the variability in outcome due to unintended carryover of adherent microorganisms and unrecognized variation in inocula.

An update on the use of helminths to treat Crohn's and other autoimmunune diseases

This review updates our previous one (Reddy and Fried, Parasitol Research 100: 921-927, 2007) on Crohn's disease and helminths. The review considers the most recent literature on Trichuris suis therapy and Crohn's and the significant literature on the use of Necator americanus larvae to treat Crohn's and other autoimmune disorders. The pros and cons of helminth therapy as related to autoimmune disorders are discussed in the review. We also discuss the relationship of the bacterium Campylobacter jejuni and T. suis in Crohn's disease. The significant literature on helminths other than N. americanus and T. suis as related to autoimmune diseases is also reviewed.

Taenia taeniaeformis: colonic hyperplasia in heavily infected rats

Only one study previously mentioned the involvement of colon during Taenia taeniaeformis larvae infection in rats with inconsistent occurrence of lesions. Present study aimed to determine the consistency of histopathologic changes in colonic epithelia, and the proliferation of mucosal cells through BrdU and PCNA immunohistochemistry. Results demonstrated that crypt hyperplasia of the colon was found in all infected rats, although variable in degree even in a single tissue section. Cystic cavities were frequently seen in severely hyperplastic mucosa. Proliferative zone lengths were significantly increased and PCNA positive cells were observed throughout the colonic crypt lengths at 9 but not at 6 weeks post infection. Cell proliferation involving the major types of cells in the epithelial colon was also increased in infected rats at 9 weeks post infection, with labeling indices significantly greater than the control rats throughout the BrdU time course labeling. Findings suggested that massive increases in epithelial cells and depth of colonic crypts were due to a remarkable increase in cell proliferation. The study concluded that enteropathy in the colon during T. taeniaeformis infection could be consistently observed in heavily infected rats.

Geohelminth infections protect against severe inflammatory diarrhoea inchildren

We investigated the risk of severe inflammatory diarrhoea associated with geohelminth parasites in 1746 children attending a rural hospital in Ecuador from December 2000 to July 2002. Infections with geohelminths were strongly protective against the risk of severe inflammatory diarrhoea. Our findings suggest that geohelminth infections have important protective effects against enteroinvasive infections in young children.