Dangerous liaisons: how helminths manipulate the intestinal epithelium

In vitro co-culture of Fasciola hepatica newly excysted juveniles (NEJs) with 3D HepG2 spheroids permits novel investigation of host-parasite interactions

Fasciola hepatica, or liver fluke, causes fasciolosis in humans and livestock. Following ingestion of vegetation contaminated with encysted parasites, metacercariae, newly excysted juveniles (NEJ) excyst in the small intestine and cross the intestinal wall. After penetrating the liver, the parasite begins an intra-parenchymal migratory and feeding phase that not only drives their rapid growth and development but also causes extensive haemorrhaging and immune pathology. Studies on infection are hindered by the difficulty in accessing these microscopic juvenile parasites in vivo. Thus, a simple and scalable in vitro culture system for parasite development is needed. Here, we find that two-dimensional (2D) culture systems using cell monolayers support NEJ growth to a limited extent. By contrast, co-culture of F. hepatica NEJ with HepG2-derived 3D spheroids, or "mini-livers," that more closely mimic the physiology and microenvironment of in vivo liver tissue, promoted NEJ survival, growth, and development. NEJ grazed on the peripheral cells of the spheroids, and they released temporally regulated digestive cysteine proteases, FhCL3, and FhCL1/2, similar to in vivo parasites. The 3D co-culture induced development of the NEJ gut and body musculature, and stimulated the tegument to elaborate spines and a variety of surface sensory/tango/chemoreceptor papillae (termed S1, S2, and S3); these were especially pronounced around the oral and ventral suckers that sense host chemical cues and secure the parasite in tissue. HepG2 3D spheroid/parasite co-culture methodologies should accelerate investigations into the understanding of F. hepatica NEJ developmental biology and studies on host-parasite interactions, and streamline the search for new anti-parasite interventions.

Molecular detection of intestinal parasites in a rural community of Colombia: A one health approach to explore potential environmental-zoonotic transmission

AIMS

Protozoan and helminth parasitic infections pose significant public health challenges, especially in developing countries with rural populations marked by suboptimal hygiene practices and socio-economic constraints. The parasites are the etiological agents of these infections and have a notably elevated global prevalence. Therefore, this study focuses on estimating the frequency and transmission dynamics of several parasitic species, including Blastocystis, Giardia, Cryptosporidium spp., Entamoeba histolytica, Ascaris lumbricoides, Trichuris trichiura, Taenia spp. and hookworms, within a rural community in southwest Colombia with a particular emphasis on the One Health framework, considering environmental and zoonotic transmission potentials.

METHODS AND RESULTS

This study involved the analysis of 125 samples, encompassing human participants (n = 99), their domestic pets (dogs) (n = 24) and water sources (n = 2). Parasite detection was carried out utilizing a combination of microscopy and molecular techniques. Furthermore, the characterization of Blastocystis subtypes (STs) was achieved through Oxford Nanopore sequencing of the rRNA-18S gene. The investigation also entailed the examination of potential associations between intestinal parasitism and various sociodemographic factors. Results revealed a high frequency of parasitic infections when employing molecular methods, with Blastocystis (n = 109/87%), Giardia (n = 20/16%), Ancylostoma duodenale (n = 28/22%), Ancylostoma ceylanicum (n = 7/5.6%), E. histolytica (n = 6/4.8%), Cryptosporidium spp. (n = 12/9.6%) and even Taenia (n = 1/0.8%) detected. Cryptosporidium spp. was also identified in water samples. Coinfections were prevalent, with 57% (n = 70) of samples exhibiting single-parasite infections and 43% (n = 53) showing various degrees of polyparasitism, emphasizing the complexity of transmission dynamics. Blastocystis subtyping, conducted via Oxford Nanopore sequencing, revealed a diversity of subtypes and coexistence patterns, with ST2 being the most prevalent.

CONCLUSIONS

This research underscores the importance of using molecular techniques for frequency estimation, particularly emphasizing the relevance of zoonotic transmission in parasitic infections. It highlights the significance of the One Health approach in comprehending the circulation of parasites among animals, humans and environmental sources, thereby directly impacting public health and epidemiological surveillance.

Worming into infancy: Exploring helminth-microbiome interactions in early life

There is rapidly growing awareness of microbiome assembly and function in early-life gut health. Although many factors, such as antibiotic use and highly processed diets, impinge on this process, most research has focused on people residing in high-income countries. However, much of the world's population lives in low- and middle-income countries (LMICs), where, in addition to erratic antibiotic use and suboptimal diets, these groups experience unique challenges. Indeed, many children in LMICs are infected with intestinal helminths. Although helminth infections are strongly associated with diverse developmental co-morbidities and induce profound microbiome changes, few studies have directly examined whether intersecting pathways between these components of the holobiont shape health outcomes in early life. Here, we summarize microbial colonization within the first years of human life, how helminth-mediated changes to the gut microbiome may affect postnatal growth, and why more research on this relationship may improve health across the lifespan.

Toxocara canis-induced changes in host intestinal microbial communities

BACKGROUND

Toxocara canis is a roundworm that resides in the gastrointestinal tract of dogs and causes various pathological changes. The dog's intestinal system consists of a diverse and dynamic bacterial community that has extensive effects on intestinal physiology, immunity and metabolics. In the case of intestinal parasites, interactions with the host intestinal flora are inevitable during the process of parasitism.

METHODS

We studied the role of T. canis in regulating the composition and diversity of the intestinal flora of the host by high-throughput sequencing of the 16S ribosomal RNA gene and various bioinformatics analyses.

RESULTS

The α-diversity analysis showed that Toxocara canis infection resulted in a significant decrease in the abundance and diversity of host intestinal flora. The β-diversity analysis showed that the intestinal flora of infected dogs was similar to that carried by T. canis. Analysis of the microflora composition and differences at the phylum level showed that the ratio of Firmicutes to Bacteroidetes (F/B ratio) increased with T. canis infection. Analysis of species composition and differences at the genus level revealed that the proportion of some of the pathogenic bacteria, such as Clostridium sensu stricto and Staphylococcus, increased after T. canis infection.

CONCLUSIONS

Toxocara canis infection affected the composition and diversity of the flora in the host intestinal tract. These results not only shed light on the potential mechanism of T. canis invasion and long-term survival in the intestinal tract, but also provide a new basis for the development of anthelmintic drugs.