Intestinal permeability in strongyloidiasis

Helminths' therapeutic potential to treat intestinal barrier dysfunction

The intestinal barrier is a dynamic multi-layered structure which can adapt to environmental changes within the intestinal lumen. It has the complex task of allowing nutrient absorption while limiting entry of harmful microbes and microbial antigens present in the intestinal lumen. Excessive entry of microbial antigens via microbial translocation due to 'intestinal barrier dysfunction' is hypothesised to contribute to the increasing incidence of allergic, autoimmune and metabolic diseases, a concept referred to as the 'epithelial barrier theory'. Helminths reside in the intestinal tract are in intimate contact with the mucosal surfaces and induce a range of local immunological changes which affect the layers of the intestinal barrier. Helminths are proposed to prevent, or even treat, many of the diseases implicated in the epithelial barrier theory. This review will focus on the effect of helminths on intestinal barrier function and explore whether this could explain the proposed health benefits delivered by helminths.

Helminth-derived biomacromolecules as therapeutic agents for treating inflammatory and infectious diseases: What lessons do we get from recent findings?

Despite the tremendous progress in healthcare sectors, a number of life-threatening infectious, inflammatory, and autoimmune diseases are continuously challenging mankind throughout the globe. In this context, recent successes in utilizing helminth parasite-derived bioactive macromolecules viz. glycoproteins, enzymes, polysaccharides, lipids/lipoproteins, nucleic acids/nucleotides, and small organic molecules for treating various disorders primarily resulted from inflammation. Among the several parasites that infect humans, helminths (cestodes, nematodes, and trematodes) are known as efficient immune manipulators owing to their explicit ability to modulate and modify the innate and adaptive immune responses of humans. These molecules selectively bind to immune receptors on innate and adaptive immune cells and trigger multiple signaling pathways to elicit anti-inflammatory cytokines, expansion of alternatively activated macrophages, T-helper 2, and immunoregulatory T regulatory cell types to induce an anti-inflammatory milieu. Reduction of pro-inflammatory responses and repair of tissue damage by these anti-inflammatory mediators have been exploited for treating a number of autoimmune, allergic, and metabolic diseases. Herein, the potential and promises of different helminths/helminth-derived products as therapeutic agents in ameliorating immunopathology of different human diseases and their mechanistic insights of function at cell and molecular level alongside the molecular signaling cross-talks have been reviewed by incorporating up-to-date findings achieved in the field.

Chronic Strongyloides stercoralis infection increases presence of the Ruminococcus torques group in the gut and alters the microbial proteome

We explored the impact of chronic Strongyloides stercoralis infection on the gut microbiome and microbial activity in a longitudinal study. At baseline (time-point T0), 42 fecal samples from matched individuals (21 positive for strongyloidiasis and 21 negative) were subjected to microbiome 16S-rRNA sequencing. Those positive at T0 (untreated then because of COVID19 lockdowns) were retested one year later (T1). Persistent infection in these individuals indicated chronic strongyloidiasis: they were treated with ivermectin and retested four months later (T2). Fecal samples at T1 and T2 were subjected to 16S-rRNA sequencing and LC-MS/MS to determine microbial diversity and proteomes. No significant alteration of indices of gut microbial diversity was found in chronic strongyloidiasis. However, the Ruminococcus torques group was highly over-represented in chronic infection. Metaproteome data revealed enrichment of Ruminococcus torques mucin-degrader enzymes in infection, possibly influencing the ability of the host to expel parasites. Metaproteomics indicated an increase in carbohydrate metabolism and Bacteroidaceae accounted for this change in chronic infection. STITCH interaction networks explored highly expressed microbial proteins before treatment and short-chain fatty acids involved in the synthesis of acetate. In conclusion, our data indicate that chronic S. stercoralis infection increases Ruminococcus torques group and alters the microbial proteome.

Membrane Technology for Rapid Point-of-Care Diagnostics for Parasitic Neglected Tropical Diseases

Parasitic neglected tropical diseases (NTDs) affect over one billion people worldwide, with individuals from communities in low-socioeconomic areas being most at risk and suffering the most. Disease management programs are hindered by the lack of infrastructure and resources for clinical sample collection, storage, and transport and a dearth of sensitive diagnostic methods that are inexpensive as well as accurate. Many diagnostic tests and tools have been developed for the parasitic NTDs, but the collection and storage of clinical samples for molecular and immunological diagnosis can be expensive due to storage, transport, and reagent costs, making these procedures untenable in most areas of endemicity. The application of membrane technology, which involves the use of specific membranes for either sample collection and storage or diagnostic procedures, can streamline this process, allowing for long-term sample storage at room temperature. Membrane technology can be used in serology-based diagnostic assays and for nucleic acid purification prior to molecular analysis. This facilitates the development of relatively simple and rapid procedures, although some of these methods, mainly due to costs, lack accessibility in low-socioeconomic regions of endemicity. New immunological procedures and nucleic acid storage, purification, and diagnostics protocols that are simple, rapid, accurate, and cost-effective must be developed as countries progress control efforts toward the elimination of the parasitic NTDs.

Helminth infection in mice improves insulin sensitivity via modulation of gut microbiota and fatty acid metabolism

Intestinal helminths are prevalent in individuals who live in rural areas of developing countries, where obesity, type 2 diabetes, and metabolic syndrome are rare. In the present study, we analyzed the modulation of the gut microbiota in mice infected with the helminth Strongyloides venezuelensis, and fed either a standard rodent chow diet or high-fat diet (HFD). To investigate the effects of the microbiota modulation on the metabolism, we analyzed the expression of tight-junction proteins present in the gut epithelium, inflammatory markers in the serum and tissue and quantified glucose tolerance and insulin sensitivity and resistance. Additionally, the levels of lipids related to inflammation were evaluated in the feces and serum. Our results show that infection with Strongyloides venezuelensis results in a modification of the gut microbiota, most notably by increasing Lactobacillus spp. These modifications in the microbiota alter the host metabolism by increasing the levels of anti-inflammatory cytokines, switching macrophages from a M1 to M2 pattern in the adipose tissue, increasing the expression of tight junction proteins in the intestinal cells (thereby reducing the permeability) and decreasing LPS in the serum. Taken together, these changes correlate with improved insulin signaling and sensitivity, which could also be achieved with HFD mice treated with probiotics. Additionally, helminth infected mice produce higher levels of oleic acid, which participates in anti-inflammatory pathways. These results suggest that modulation of the microbiota by helminth infection or probiotic treatment causes a reduction in subclinical inflammation, which has a positive effect on the glucose metabolism of the host.

Helminths as an alternative therapy for intestinal diseases

Animal models and clinical studies have shown that helminth infections exert immunomodulatory activity, altering intestinal permeability and providing a potential beneficial action on autoimmune and inflammatory disorders in human beings, such as inflammatory bowel disease (IBD) and celiac disease. This is consistent with the theory that intestinal microbiota is responsible for shaping human immunological responses. With the arrival of the immunobiologic era and the use of antibodies, we propose a distinctive pathway for treating patients with IBD and celiac disease. We have some evidence about the safety and tolerability of helminth use, but evidence about their impact on disease activity is lacking. Using worms to treat diseases could be a possible way to lower treatment costs, since the era of immunobiologic agents is responsible for a significant rise in expenses. Some questions remain to be investigated regarding the use of helminths in intestinal disease, such as the importance of the specific species of helminths used, appropriate dosing regimens, optimal timing of treatment, the role of host genetics, diet, environment, and the elucidation of the exact mechanisms of action. One promising approach is the use of helminth-derived anti-inflammatory molecules as drugs. Yet there are still many challenges with this method, especially with regard to safety. Studies on intestinal permeability point to Strongyloides stercoralis as a useful nematode for these purposes.

Intestinal permeability and antigliadin antibody test for monitoring adult patients with celiac disease

Celiac disease causes chronic inflammation of the intestinal mucosa and reduces surface absorption; after the withdrawal of gluten from the diet, there are clinical and histologic improvements. The intestinal permeability test and serologic tests are useful for confirming the diagnosis and monitoring patients. The goal of this study is to compare the antigliadin antibody (AGA) test with the intestinal permeability test for celiac patients on a gluten-free diet. The sample consisted of 22 celiac patients who were antigliadin immunoglobulin A-positive before treatment. After 12 months on a gluten-free diet, AGA testing was repeated and the intestinal permeability test was performed. A control group was composed of 11 healthy individuals. AGA remained positive in 40.9% of celiac patients, and the mean urinary lactulose excretion was 10.27%, that of mannitol was 10.18%, and the lactulose/mannitol ratio was 1.02. In the subgroup in which antigliadin became negative (59.1%), the value for lactulose was 3.79%, that for mannitol was 11.12%, the lactulose/mannitol ratio was 0.38, and the p value was less than 0.0001, 0.66, and less than 0.0001, respectively. When the two celiac subgroups were compared with the control group, the urinary lactulose excretion and the lactulose/mannitol ratio was less in the control group, whereas urinary mannitol excretion was greater. The p values were less than 0.0001 for the three variables, suggesting persistent lesions in mucosa of both subgroups, although to a lesser degree for those that became AGA negative. It is concluded that intestinal permeability allows a more precise clinical physiopathologic correlation than antigliadin and offers more information for the monitoring of these patients.

Enteric pathogens, intestinal permeability and nitric oxide production in acute gastroenteritis

BACKGROUND

Aboriginal children hospitalized with diarrheal disease in northern Australia have high rates of acidosis, hypokalemia and osmotic diarrhea, as well as abnormal small bowel permeability and elevated nitric oxide (NO) production.

METHODS

In a study of 291 diarrheal admissions and 84 controls, we examined the relationship of diarrheal severity outcomes with specific enteric pathogens. NO production was measured by urine nitrate plus nitrite excretion on a low nitrate diet, small bowel permeability by the lactulose:rhamnose ratio on a timed blood specimen and stool pathogens by standard microbiologic investigations and PCR.

RESULTS

The addition of diagnostic tests for diarrheagenic Escherichia coli to standard stool microbiologic testing increased the rate of specific diagnoses from 53% to 75%, but with multiple pathogens isolated from 34%. The most frequently isolated pathogens from diarrheal patients were enteroaggregative E. coli (28.9%), rotavirus (26.5%), enteropathogenic E. coli (17.2%), Salmonella spp. (10.7%), Cryptosporidium parvum (7.2%) and Strongyloides stercoralis (7.2%). High geometric mean permeability ratios (95% confidence intervals) occurred with rotavirus (19.6; 15.3 to 25.1), enteroaggregative E. coli (21.2; 15.3 to 29.3) and Cryptosporidium (23.0; 15.1 to 35.1) compared with 9.4 (6.8 to 13.1) for no pathogens. NO production was highest for Cryptosporidium (3.7; 2.3 to 6.1) compared with 0.6 (0.4 to 1.1) for no pathogens. Multiple regression analysis revealed significant associations (P < 0.001) for rotavirus with acidosis and osmotic diarrhea, for Strongyloides with wasting and hypokalemia and for Cryptospoidium with severe and prolonged diarrhea.

CONCLUSIONS

Cryptosporidium, Strongyloides, rotavirus and enteroaggregative E. coli are important contributors to the severe manifestations of acute gastroenteritis in Australian Aboriginal children.

Small bowel intestinal permeability in Australian aboriginal children

OBJECTIVE

To show that the severity of diarrheal disease in Aboriginal children in tropical Australia is a consequence of underlying small intestinal mucosal damage.

STUDY DESIGN

A prospective study of 338 Aboriginal admissions compared to 37 non-Aboriginal children, both diarrhea cases and controls. Intestinal permeability was measured by lactulose-rhamnose (L/R) ratios on a timed 90-minute blood test.

RESULTS

For diarrheal admissions, significantly more Aboriginal (vs. non-Aboriginal children) had hypokalemia (70 vs. 10%), acidosis (65 vs. 29%), moderate to severe dehydration (52 vs. 19%) and a longer mean length of stay (mean 8.9 vs. 3.9 days). Mean L/R ratios (95% confidence intervals) in Aboriginal children (diarrhea vs. controls) were 16.5 (14.6-18.7) vs. 4.5 (3.8-5.3) compared to 7.7 (4.4-13.3) vs. 2.5 (1.8-3.4), respectively, in non-Aboriginals. Abnormal permeability ratios (> 5.6) consistent with tropical-environmental enteropathy syndrome were found in 36% (27/75) of Aboriginal controls compared to none of the non-Aboriginal controls. On multiple regression, the factors associated with high L/R ratios were diarrheal severity ( < 0.001), acidosis ( = 0.007) and hypokalemia ( = 0.04).

CONCLUSIONS

An underlying tropical-environmental enteropathy contributes to the severity of acute gastroenteritis in Aboriginal children. Diarrheal complications, such as acidosis, hypokalemia, and osmotic diarrhea are associated with high L/R ratios, reflecting greater small intestinal mucosal damage.