Distinct characteristics of two intestinal protein compartments discriminated by using fenbendazole and a benzimidazole resistant isolate of Haemonchus contortus

Correlation of NHR-48 Transcriptional Modulator Expression with Selected CYP Genes’ Expression during Thiabendazole Treatment of Anisakis simplex (s.l.)?—An In Vitro Study

Anisakis simplex (s.l.) is a complex of three sibling (biological) species of parasitic nematodes of marine mammals, including A. berlandi, A. pegreffii and A. simplex (s.s.). It is characterized by a complex life cycle in which humans can become accidental hosts by consuming dishes made of raw or undercooked fish containing L3 larvae, which in many regions of the world is related to the national or regional culinary tradition. This has spurred scientific efforts to develop new methods for treating the disease, called anisakiasis, and to neutralize invasive L3. Thiabendazole (TBZ) is a wide-spectrum anthelminthic with a higher efficacy than albendazole, a drug whose long-term use induces resistance in many parasitic species. Cytochromes P450 participate in TBZ metabolism, and the expression of their genes is controlled by nuclear hormone receptors (NHR). This study aimed to examine the effects of TBZ on the above-described pathway in invasive larvae of A. simplex (s.l.). The efficacy of TBZ against A. simplex (s.l.) larvae was observed for the first time. Larvae were cultured in vitro for 72 h in a medium containing TBZ at five concentrations from 0.5 to 1.5 mM. However, the survival curves did not significantly differ from each other. This means that all of the concentrations of TBZ had a similar effect on the A. simplex (s.l.) L3 larvae during in vitro culture. Nevertheless, TBZ modified the expression of nhr-48, cyp13a3 and cyp1a1 genes in the L3 of A. simplex (s.l.).

Omics Driven Understanding of the Intestines of Parasitic Nematodes

The biological and molecular complexity of nematodes has impeded research on development of new therapies for treatment and control. We have focused on the versatility of the nematode intestine as a target for new therapies. To that end, it is desirable to establish a broad and deep understanding of the molecular architecture underlying intestinal cell functions at the pan-Nematoda level. Multiomics data were generated to uncover the evolutionary principles underlying both conserved and adaptable features of the nematode intestine. Whole genomes were used to reveal the functional potential of the nematodes, tissue-specific transcriptomes provided a deep assessment of genes that are expressed in the adult nematode intestine, and comparison of selected core species was used to determine a first approximation of the pan-Nematoda intestinal transcriptome. Differentially expressed transcripts were also identified among intestinal regions, with the largest number expressed at significantly higher levels in the anterior region, identifying this region as the most functionally unique compared to middle and posterior regions. Profiling intestinal miRNAs targeting these genes identified the conserved intestinal miRNAs. Proteomics of intestinal cell compartments assigned proteins to several different intestinal cell compartments (intestinal tissue, the integral and peripheral intestinal membranes, and the intestinal lumen). Finally, advanced bioinformatic approaches were used to predict intestinal cell functional categories of seminal importance to parasite survival, which can now be experimentally tested and validated. The data provide the most comprehensive compilation of constitutively and differentially expressed genes, predicted gene regulators, and proteins of the nematode intestine. The information provides knowledge that is essential to understand molecular features of nematode intestinal cells and functions of fundamental importance to the intestine of many, if not all, parasitic nematodes.

In vitro effect of seven antiparasitics on Acolpenteron ureteroecetes (Dactylogyridae) from largemouth bass Micropterus salmoides (Centrarchidae)

Few drugs are approved by the United States Food and Drug Administration for treating parasite infections in minor species such as fish, due in part to the high cost of developing such drugs and to a relatively small market share for drug sponsors. Because in vivo effectiveness trials for antiparasitic drugs are costly, time consuming, and use many animals, a systematic in vitro screening approach to describe parasite motility could help find promising drug candidates. We evaluated the effects of 7 antiparasitics on the activity and survival of the endoparasitic monogenean Acolpenteron ureteroecetes (Dactylogyridae) collected from the posterior kidneys of juvenile largemouth bass Micropterus salmoides (Lacepede, 1802) (Centrarchidae) held in the laboratory. Tests were conducted in 12 well tissue culture plates; each well had 3 parasites, and we tested 3 concentrations and 1 control for each of the 7 antiparasitics. The parasites were observed immediately after adding the drug, at 1 to 3 h, and 17 to 26 h, and video recordings were made. Drug effects were recorded by documenting morbidity (reduced movement, tremors, contracted body, abnormal morphology) and mortality. A. ureteroecetes was strongly affected by the quinoline praziquantel, the imidazothiazide levamisole, and the organophosphates dichlorvos and trichlorfon. The parasites were moderately affected by the macrocyclic lactones ivermectin and emamectin, and generally unaffected by the benzimidazole mebendazole. Our study demonstrates the utility of characterizing in vitro responses with video microscopy to document responses of fish parasites for initial screens of drug effects on a fish monogenean.

Molecular determinants archetypical to the phylum Nematoda

Background

Nematoda diverged from other animals between 600–1,200 million years ago and has become one of the most diverse animal phyla on earth. Most nematodes are free-living animals, but many are parasites of plants and animals including humans, posing major ecological and economical challenges around the world.

Results

We investigated phylum-specific molecular characteristics in Nematoda by exploring over 214,000 polypeptides from 32 nematode species including 27 parasites. Over 50,000 nematode protein families were identified based on primary sequence, including ~10% with members from at least three different species. Nearly 1,600 of the multi-species families did not share homology to Pfam domains, including a total of 758 restricted to Nematoda. Majority of the 462 families that were conserved among both free-living and parasitic species contained members from multiple nematode clades, yet ~90% of the 296 parasite-specific families originated only from a single clade. Features of these protein families were revealed through extrapolation of essential functions from observed RNAi phenotypes in C. elegans, bioinformatics-based functional annotations, identification of distant homology based on protein folds, and prediction of expression at accessible nematode surfaces. In addition, we identified a group of nematode-restricted sequence features in energy-generating electron transfer complexes as potential targets for new chemicals with minimal or no toxicity to the host.

Conclusion

This study identified and characterized the molecular determinants that help in defining the phylum Nematoda, and therefore improved our understanding of nematode protein evolution and provided novel insights for the development of next generation parasite control strategies.

Intestinal transcriptomes of nematodes: comparison of the parasites Ascaris suum and Haemonchus contortus with the free-living Caenorhabditis elegans

Background

The nematode intestine is a major organ responsible for nutrient digestion and absorption; it is also involved in many other processes, such as reproduction, innate immunity, stress responses, and aging. The importance of the intestine as a target for the control of parasitic nematodes has been demonstrated. However, the lack of detailed knowledge on the molecular and cellular functions of the intestine and the level of its conservation across nematodes has impeded breakthroughs in this application.

Methods and Findings

As part of an extensive effort to investigate various transcribed genomes from Ascaris suum and Haemonchus contortus, we generated a large collection of intestinal sequences from parasitic nematodes by identifying 3,121 A. suum and 1,755 H. contortus genes expressed in the adult intestine through the generation of expressed sequence tags. Cross-species comparisons to the intestine of the free-living C. elegans revealed substantial diversification in the adult intestinal transcriptomes among these species, suggesting lineage- or species-specific adaptations during nematode evolution. In contrast, significant conservation of the intestinal gene repertories was also evident, despite the evolutionary distance of ∼350 million years separating them. A group of 241 intestinal protein families (IntFam-241), each containing members from all three species, was identified based on sequence similarities. These conserved proteins accounted for ∼20% of the sampled intestinal transcriptomes from the three nematodes and are proposed to represent conserved core functions in the nematode intestine. Functional characterizations of the IntFam-241 suggested important roles in molecular functions such as protein kinases and proteases, and biological pathways of carbohydrate metabolism, energy metabolism, and translation. Conservation in the core protein families was further explored by extrapolating observable RNA interference phenotypes in C. elegans to their parasitic counterparts.

Conclusions

Our study has provided novel insights into the nematode intestine and lays foundations for further comparative studies on biology, parasitism, and evolution within the phylum Nematoda.

Biological properties of the nematode intestine warrant in-depth investigation, the results of which can be utilized in the control of parasitic nematodes that infect humans, livestock, and plants. Both the importance of intestinal antigens from Haemonchus contortus in immunity and the damage to H. contortus intestine by anthelmintic fenbendazole have highlighted the versatility of the intestine as an emerging target. However, biological information regarding fundamental intestinal cell functions and mechanisms is currently limited. Conserved intestinal genes across nematode pathogens could offer molecular targets for broad parasite control. Furthermore, qualitative and quantitative comparisons on intestinal gene expression among species and lineages can identify basic adaptations relative to a critical selective force, the nutrient acquisition. This study begins to identify intestinal cell characteristics that are conserved across representatives of two clades of nematodes (V and III) and further clarifies diversities that likely reflect species- or lineage-specific adaptations. Results consistent with functional data on digestive enzymes from H. contortus and RNAi in Caenorhabditis elegans, as examples, support the potential for the comparative genomics approach to produce practical applications. This study provides a platform on which extensive investigation of intestinal genes and a more comprehensive understanding of the Nematoda can be gained.