INTERACTION OF EIMERIA TENELLA WITH INTESTINAL MUCIN IN VITRO

Differential expression of microRNAs in the caecal content and faeces of broiler chickens experimentally infected with Eimeria

AbstractCoccidiosis caused by Eimeria spp. incurs significant morbidity and mortality in chickens, and is thus of great economic importance. Post-mortem intestinal lesion scoring remains one of the most common means of diagnosis, and therefore alternative, non-invasive methods of diagnosis and monitoring would be highly desirable. Micro-RNAs (miRNAs) have been shown to be stable in faeces of human and animal species with expression altered in gastrointestinal disease. We hypothesised that miRNA is stable in caecal content of chickens, and that differential miRNA expression patterns would be seen in Eimeria infected versus uninfected individuals. Initially, RNA was extracted from Eimeria tenella infected (n = 3; seven days post-infection) and uninfected (n = 3) chicken caecal content to demonstrate miRNA stability. Subsequently, next generation miRNA sequencing was performed on caecal content from E. tenella infected chickens with high (lesion score (LS) 3-4; n = 3) or low (LS1; n = 3) levels of pathology and uninfected controls (n = 3). Comparative analysis identified 19 miRNAs that exhibited significantly altered expression in the caecal content of E. tenella infected chickens versus uninfected chickens (t-test, False Discovery Rate (FDR) < 0.05). Eight of these miRNAs showed significant up-regulation in infection (fold change of 9.8-105, FDR <0.05). Quantitative PCR was performed using separate biological replicates to confirm differential regulation in 8 of these miRNA candidates in caecal and faecal content. This work has identified a panel of miRNA candidates which may be appropriate for use as non-invasive faecal markers of active caecal coccidiosis without the need for culling.

Effects of host vimentin on Eimeria tenella sporozoite invasion

Background

Chicken coccidiosis is a parasitic disease caused by Eimeria of Apicomplexa, which has caused great economic loss to the poultry breeding industry. Host vimentin is a key protein in the process of infection of many pathogens. In an earlier phosphorylation proteomics study, we found that the phosphorylation level of host vimentin was significantly regulated after Eimeria tenella sporozoite infection. Therefore, we explored the role of host vimentin in the invasion of host cells by sporozoites.

Methods

Chicken vimentin protein was cloned and expressed. We used qPCR, western blotting, and indirect immunofluorescence to detect levels of mRNA transcription, translation, and phosphorylation, and changes in the distribution of vimentin after E. tenella sporozoite infection. The sporozoite invasion rate in DF-1 cells treated with vimentin polyclonal antibody or with small interfering RNA (siRNA), which downregulated vimentin expression, was assessed by an in vitro invasion test.

Results

The results showed that vimentin transcription and translation levels increased continually at 6–72 h after E. tenella sporozoite infection, and the total phosphorylation levels of vimentin also changed. About 24 h after sporozoite infection, vimentin accumulated around sporozoites in DF-1 cells. Treating DF-1 cells with vimentin polyclonal antibody or downregulating vimentin expression by siRNA significantly improved the invasion efficiency of sporozoites.

Conclusion

In this study, we showed that vimentin played an inhibitory role during the invasion of sporozoites. These data provided a foundation for clarifying the relationship between Eimeria and the host.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-05107-4.

Purified mucins in drug delivery research

One of the main challenges in the field of drug delivery remains the development of strategies to efficiently transport pharmaceuticals across mucus barriers, which regulate the passage and retention of molecules and particles in all luminal spaces of the body. A thorough understanding of the molecular mechanisms, which govern such selective permeability, is key for achieving efficient translocation of drugs and drug carriers. For this purpose, model systems based on purified mucins can contribute valuable information. In this review, we summarize advances that were made in the field of drug delivery research with such mucin-based model systems: First, we give an overview of mucin purification procedures and discuss the suitability of model systems reconstituted from purified mucins to mimic native mucus. Then, we summarize techniques to study mucin binding. Finally, we highlight approaches that made use of mucins as building blocks for drug delivery platforms or employ mucins as active compounds.

Anticoccidial effect of toltrazuril and Radix Sophorae Flavescentis combination: Reduced inflammation and promoted mucosal immunity

An anticoccidial model of chicken infected with Eimeria tenella was established to investigate the effect of toltrazuril (Tol) combined with the Radix Sophorae Flavescentis (RSF) on coccidiosis. The anticoccidial index (ACI) was evaluated, and the cecal developmental parameters (i.e., villus height, [VH], crypt depth, [CD], and VH/CD) were determined. The distributions of glycoproteins and goblet cells in the cecal tissue were determined through the Periodic Acid-Schiff (PAS) and Alcian blue PAS staining methods, respectively. The mRNA expression levels of interleukin (IL)-1β, IL-2, IL-4, IL-6, IL-10, and IL-17 of the cecal tissue were determined through quantitative real-time PCR. The moderate ACI was obtained using the combination of Tol and RSF. Compared with the normal control (NC) group, the infected control (IC) group showed remarkably lower VH and VH/CD at five and seven days postinfection. Compared with the IC group, the IC + RSF and IC + TolRSF groups showed remarkably higher VH and VH/CD at five and seven days postinfection. Compared with the NC group, the IC group contained fewer glycoproteins and goblet cells, but the Tol and RSF treatment promoted more glycoproteins and goblet cells at five and seven days postinfection. The mRNA expression levels of IL-1β, IL-2, IL-4, IL-6, IL-10, and IL-17 in the IC group were upregulated (P < 0.01) compared with those in the NC group. The IC + RSF and IC + TolRSF groups had downregulated mRNA expression levels of IL-1β, IL-6, and IL-17 cytokines (P < 0.01), and upregulated mRNA expression levels of IL-2 and IL-4 cytokines (P < 0.01) compared with the IC group. Results showed that the combination of Tol and RSF exerts anticoccidial effect by reducing inflammation and promoting intestinal mucosal immunity.

Modulation of Morphology and Glycan Composition of Mucins in Farmed Guinea Fowl (Numida meleagris) Intestine by the Multi-Strain Probiotic Slab51®

Probiotics have become highly recognized as supplements for poultry.Since gut health can be considered synonymous withanimal health, the effects of probiotic Slab51® on the morphology and the glycan composition of guineafowlintestine were examined. The probiotics were added in drinking water (2 × 1011 UFC/L) throughout the grow-out cycle.Birds were individually weighed andslaughtered after four months. Samples from the duodenum, ileum and caecum were collected and processed for morphological, morphometric, conventional and lectin glycohistochemical studies.The results were analyzed for statistical significance by Student's t test. Compared with control samples, probiotic group revealed (1) significant increase in villus height (p < 0.001 in duodenum and ileum; p < 0.05 in caecum), crypt depth (p < 0.001 in duodenum and caecum; p < 0.05 in ileum) and goblet cells (GCs) per villus (p < 0.001) in all investigated tracts; (2) increase in galactoseβl,3N-acetylgalacyosamine(Galβl,3GalNAc)terminating O-glycans and αl,2-fucosylated glycans secretory GCs in the duodenum; (3) increase in α2,6-sialoglycans and high-mannose N-linked glycans secretory GCs but reduction in GCs-secreting sulfoglycans in the ileum; (4) increase in Galβl,3GalNAc and high-mannose N-linked glycans secretory GCs and decrease in GCs-producing sulfomucins in the caecum; (5) increase in the numbers of crypt cells containing sulfate and non-sulfated acidic glycans. Overall, dietary Slab51® induces morphological and region-specific changes in glycoprotein composition of guinea fowl intestine, promoting gut health.

Overview of Poultry Eimeria Life Cycle and Host-Parasite Interactions

Apicomplexan parasites of the genus Eimeria are organisms which invade the intestinal tract, causing coccidiosis, an enteric disease of major economic importance worldwide. The disease causes high morbidity ranging from an acute, bloody enteritis with high mortality, to subclinical disease. However, the presence of intestinal lesions depends on the Eimeria species. The most important poultry Eimeria species are: E. tenella, E. necatrix, E. acervulina, E. maxima, E. brunetti, E. mitis, and E. praecox. Key points to better understanding the behavior of this species are the host-parasite interactions and its life cycle. The present paper reviews the literature available regarding the life cycle and the initial host-parasite interaction. More studies are needed to better understand these interactions in poultry Eimerias, taking into account that almost all the information available was generated from other apicomplexan parasites that generate human disease.

Mucus-Pathogen Interactions in the Gastrointestinal Tract of Farmed Animals

Gastrointestinal infections cause significant challenges and economic losses in animal husbandry. As pathogens becoming resistant to antibiotics are a growing concern worldwide, alternative strategies to treat infections in farmed animals are necessary in order to decrease the risk to human health and increase animal health and productivity. Mucosal surfaces are the most common route used by pathogens to enter the body. The mucosal surface that lines the gastrointestinal tract is covered by a continuously secreted mucus layer that protects the epithelial surface. The mucus layer is the first barrier the pathogen must overcome for successful colonization, and is mainly composed of densely glycosylated proteins called mucins. The vast array of carbohydrate structures present on the mucins provide an important setting for host-pathogen interactions. This review summarizes the current knowledge on gastrointestinal mucins and their role during infections in farmed animals. We examine the interactions between mucins and animal pathogens, with a focus on how pathogenic bacteria can modify the mucin environment in the gut, and how this in turn affects pathogen adhesion and growth. Finally, we discuss analytical challenges and complexities of the mucus-based defense, as well as its potential to control infections in farmed animals.

Effect of threonine deficiency on intestinal integrity and immune response to feed withdrawal combined with coccidial vaccine challenge in broiler chicks

For this study, threonine (Thr) deficiency was hypothesised to exacerbate the intestinal damage induced by feed withdrawal with coccidial infection because of its high obligatory requirement by the gut; two dietary Thr treatments (0·49 and 0·90 %) were applied to chicks from 0 to 21 d of age. At 13 d of age, feed was withdrawn for 24 h from one-half of birds of each dietary treatment with subsequent gavage of a 25× dose of coccidial vaccine. Overall, there were four treatments with eight replicate cages per treatment. Under combined challenge, birds fed the Thr-deficient diet had 38 % lower 13–21-d body weight gain (P≤0·05) compared with birds fed the Thr-control diet. At 21 d, the challenged group fed low Thr had higher number of oocysts (+40 %, P=0·03) and lower crypt depth (−31 %, P<0·01). In addition, birds fed the low-Thr diet had higher gut permeability as measured after 2 h of administration of fluorescein isothiocyanate-dextran (3–5 kDa, P<0·01), which may be attributed to decreased IgA production (P=0·03) in the ileum. In caecal tonsils, the challenged group fed low Thr had lower CD3:Bu-1 ratio (P≤0·05), along with a tendency for lower CCR9 mRNA expression in birds fed the low-Thr diet (P=0·10). In addition, Thr deficiency tended to increase IL-10 mRNA expression regardless of infection (P=0·06), but did not change interferon-γ mRNA expression upon coccidial infection (P>0·05). Overall, Thr deficiency worsened the detrimental effects of combined feed withdrawal and coccidial infection on growth performance and oocyst shedding by impairing intestinal morphology, barrier function, lymphocyte profiles and their cytokine expressions.

Identification of O-glycan Structures from Chicken Intestinal Mucins Provides Insight into Campylobactor jejuni Pathogenicity

The Gram-negative bacteria Campylobactor jejuni is the primary bacteria responsible for food poisoning in industrialized countries, and acute diarrheal illness is a leading cause of mortality among children in developing countries. C. jejuni are commensal in chickens. They are particularly abundant in the caecal crypts, and poultry products are commonly infected as a result of cross-contamination during processing. The interactions between C. jejuni and chicken intestinal tissues as well as the pathogenic molecular mechanisms of colonization in humans are unknown, but identifying these factors could provide potential targets to reduce the incidence of campylobacteriosis. Recently, purified chicken intestinal mucin was shown to attenuate adherence and invasion of C. jejuni in the human colorectal adenocarcinoma cell line HCT-8 in vitro, and this effect was attributed to mucin O-glycosylation. Mucins from different regions of the chicken intestine inhibited C. jejuni binding and internalization differentially, with large intestine>small intestine>caecum. Here, we use LC-MS to perform a detailed structural analysis of O-glycans released from mucins purified from chicken large intestine, small intestine, and caecum. The O-glycans identified were abundantly sulfated compared with the human intestines, and sulfate moieties were present throughout the chicken intestinal tract. Interestingly, alpha 1-2 linked fucose residues, which have a high binding affinity to C. jejuni, were identified in the small and large intestines. Additionally, N-glycolylneuraminic/N-acetylneuraminic acid containing structures present as Sd(a)-like epitopes were identified in large intestine samples but not small intestine or caecum. O-glycan structural characterization of chicken intestinal mucins provides insights into adherence and invasion properties of C. jejuni, and may offer prospective candidate molecules aimed at reducing the incidence of infection.

Expression of digestive enzymes and nutrient transporters in Eimeria acervulina-challenged layers and broilers

Avian coccidiosis is a disease caused by intestinal protozoa in the genus Eimeria. Clinical signs of coccidiosis include intestinal lesions and reduced feed efficiency and BW gain. This growth reduction may be due to changes in expression of digestive enzymes and nutrient transporters in the intestine. The objective of this study was to examine the differential expression of digestive enzymes, transporters of amino acids, peptides, sugars, and minerals, and an antimicrobial peptide in the small intestine of Eimeria acervulina-infected broilers and layers. Uninfected broilers and layers, in general, expressed these genes at comparable levels. Some differences included 3-fold and 2-fold greater expression of the peptide transporter PepT1 and the antimicrobial peptide LEAP2 (liver expressed antimicrobial peptide 2), respectively, in the jejunum of layers compared with broilers and 17-fold greater expression of LEAP2 in the duodenum of broilers compared with layers. In the duodenum of Eimeria-infected broilers and layers, there was downregulation of aminopeptidase N; sucrase-isomaltase; the neutral, cationic, and anionic amino acid transporters b(o,+)AT/rBAT, B(o)AT, CAT2, and EAAT3; the sugar transporter GLUT2; the zinc transporter ZnT1; and LEAP2. In the jejunum of infected layers there was downregulation of many of the same genes as in the duodenum plus downregulation of PepT1, b(o,+)AT/rBAT, and the y(+) L system amino acid transporters y(+) LAT1 and y(+) LAT2. In the ileum of infected layers there was downregulation of CAT2, y(+)LAT1, the L type amino acid transporter LAT1, and the sugar transporter GLUT1, and upregulation of APN, PepT1, the sodium glucose transporter SGLT4, and LEAP2. In E. acervulina-infected broilers, there were no gene expression changes in the jejunum and ileum. These changes in intestinal digestive enzyme and nutrient transporter gene expression may result in a decrease in the efficiency of protein digestion, uptake of important amino acids and sugars, and disruption of mineral balance that may affect intestinal cell metabolism and Eimeria replication.

Sulfate migration in oligosaccharides induced by negative ion mode ion trap collision-induced dissociation

Migration of sulfate groups between hydroxyl groups was identified after collision-induced dissociation (CID) of sulfated oligosaccharides in an ion trap mass spectrometer in negative ion mode. Analysis of various sulfated oligosaccharides showed that this was a common phenomenon and was particularly prominent in sulfated oligosaccharides also containing sialic acid. It was also shown that the level of migration was increased when the sulfate was positioned on the flexible areas of the oligosaccharides not involved in the pyranose ring, such as the extra-cyclic C-6 carbon of hexoses or N-acetylhexosamines, or on reduced oligosaccharide. This suggested that migration is dependent on the spatial availability of the sulfate in the ion trap during collision. It is proposed that the migration is initiated when the negatively charged -SO3 (-) residue attached to the oligosaccharide precursor becomes protonated by a CID-induced proton transfer. This is supported by the CID fragmentation of precursor ions depleted of acidic protons such as doubly charged [M - 2H](2-) ions or the sodiated [M + Na - 2H](-) ions of oligosaccharides containing one sulfate and one sialic acid in the same molecule. Compared to the CID fragmentation of their monocharged [M - H](-) ions, no migration was observed in CID of proton depleted precursors. Alternative fragmentation parameters to suppress migration of sulfated oligosaccharides also showed that it was not present when sulfated oligosaccharides were fragmented by HCD (High-Energy C-trap Dissociation) in an Orbitrap mass spectrometer.

Purified chicken intestinal mucin attenuates Campylobacter jejuni pathogenicity in vitro

Campylobacter jejuni is a major causative agent of diarrhoeal disease worldwide in the human population. In contrast, heavy colonization of poultry typically does not lead to disease and colonized chickens are a major source of Campylobacter infections in humans. Previously, we have shown that chicken (but not human) intestinal mucus inhibits C. jejuni internalization. In this study, we test the hypothesis that chicken mucin, the main component of mucus, is responsible for this inhibition of C. jejuni virulence. Purified chicken intestinal mucin attenuated C. jejuni binding and internalization into HCT-8 cells depending on the site of origin of the mucin (large intestine>small intestine>caecum). C. jejuni invasion of HCT-8 cells was preferentially inhibited compared to bacterial binding to cells. Exposure of the mucin to sodium metaperiodate recovered bacterial invasion levels, suggesting a glycan-mediated effect. However, fucosidase or sialidase pre-treatment of mucin failed to abrogate the inhibition of C. jejuni pathogenicity. In conclusion, differences in the composition of chicken and human intestinal mucin may contribute to the differential outcome of Campylobacter infection of these hosts.