Molecular characterization and functional analysis of Eimeria tenella malate dehydrogenase

Pathogenicity and drug resistance of the Eimeria tenella isolate from Yiwu, Zhejiang province, eastern China

Chicken coccidiosis can cause severe enteritis with high mortality, which causes serious economic losses to the global breeding industry each year. The most virulent species is Eimeria tenella (E. tenella), but the infectivity of different E. tenella varies among geographic strains. At present, there are no reports related to the pathogenicity and drug resistance of E. tenella in Yiwu, Zhejiang province, China. A total of 600 fecal samples were collected from 10 farms in Zhejiang province, the overall oocyst prevalence was 54.2% (325/600). The prevalence was significantly higher (P < 0.01) in chickens under 40 d (97.5%) than that in chickens between 60 and 85-days-old (40.5%) and chickens over 90-days-old (24.5%). E. tenella stain was isolated from fecal samples of chickens in Yiwu and the pathogenicity of this isolate was determined, and then we recorded the survival rate, bloody stool score, lesion score, average weight gain. The results showed that all of the chickens infected with 5 × 105 sporulated oocysts of E. tenella died after the seventh day of infection, the bloody stool score and average lesion score of chickens from group 1 (5 × 105), group 2 (5 × 104), group 3 (5 × 103) and group 4 (5 × 102) decreased successively; the average weight gain (g) and relative weight gain (%) increased successively; the weight gain of the low-dose E. tenella infection groups (5 × 103 and 5 × 102) were higher than the other 2 groups (5 × 105 and 5 × 104) (P < 0.05). Finally, The E. tenella isolate was tested for sensitivity to 6 anticoccidial drugs (sulfachloropyrazine sodium, amproline, toltrazuril, clopidol, salinomycin, and nicarbazine) using 4 indexes including anticoccidial index(ACI), percent of optimum anticoccidial activity (POAA), reduction of lesion scores (RLS), and relative oocyst production (ROP). The results showed that this isolate has developed severe resistance to drugs of salinomycin and nicarbazine, moderate resistance to amproline and clopidol, slight resistance to toltrazuril, while the E. tenella isolate performed more sensitive to sulfachloropyrazine sodium.

Genetic selection of Eimeria parasites in the chicken for improvement of poultry health: implications for drug resistance and live vaccine development

AbstractApicomplexan parasites of the genus Eimeria are widespread in poultry flocks and can cause the intestinal disease coccidiosis. Early studies, concerned with intraspecific variation in oocyst morphology, indicated that phenotypic changes may be induced by selection experiments conducted in vivo. Genetic selection driven by targeted selection for specific phenotypes has contributed to our understanding of the phenomenon of drug resistance and the development of live attenuated vaccines. Our present knowledge regarding genetics of Eimeria is largely based upon the utilization of such selected strains as genetic markers. Practical advantages of working with Eimeria spp. in the chicken are discussed. The selection of drug resistant strains by serial propagation has provided useful information regarding the mechanisms of drug resistance and likely longevity of anticoccidial drugs when introduced in the field. Selection experiments to develop precocious strains of Eimeria and growth in chicken embryos have contributed to the development of safe and effective live attenuated vaccines for control of coccidiosis. Establishment of protocols for genetic complementation by transient or stable transfection of Eimeria is now supporting direct manipulation of parasite genotypes, creating opportunities to expand the range and value of live parasite vaccines. Procedures for developing drug resistant and precocious lines of Eimeria and/or genetic markers described here are likely to prove useful for researchers investigating the propensity for resistance development to novel compounds and the development of new attenuated vaccines. Such investigations can be helpful in providing a better understanding of biochemical and molecular aspects of the biology of these parasites.

Activation of ChTLR15/ChNF-κB-ChNLRP3/ChIL-1β signaling transduction pathway mediated inflammatory responses to E. tenella infection

Avian coccidiosis caused by Eimeria leads to severe economic losses in the global poultry industry. Although chicken Toll-like receptor 15 (ChTLR15) was reported to be involved in Eimeria infection, the detailed mechanism underlying its role in the inflammatory response remains to be discovered. The present study demonstrated that the mRNA expression levels of ChTLR15, ChMyD88, ChNF-κB, ChNLRP3, ChCaspase-1, ChIL-18 and ChIL-1β and the protein levels of ChTLR15 and ChNLRP3 in cecal tissues of Eimeria-infected chickens were significantly elevated at 4, 12, and 24 h compared with those in noninfected control chickens (p < 0.01). Moreover, the mRNA levels of molecules in the ChTLR15/ChNF-κB and ChNLRP3/ChIL-1β pathways and the protein levels of ChTLR15 and ChNLRP3 in chicken embryo fibroblast cells (DF-1) stimulated by E. tenella sporozoites were consistent with those in Eimeria-infected chickens. Furthermore, overexpression of ChTLR15 in DF1 cells augmented activation of the ChTLR15/ChNF-κB and ChNLRP3/ChIL-1β pathways when stimulated with E. tenella sporozoites, while knockdown of ChTLR15 in DF1 cells showed inverse effects. Taken together, the present study provides evidence that E. tenella sporozoites specifically activate ChTLR15 and then trigger activation of the ChNLRP3/ChIL-1β pathway, which partially mediates inflammatory responses to Eimeria infection.

Identification and Characterization of a Novel Apical Membrane Antigen 3 in Eimeria tenella

Eimeria tenella is an obligate intracellular parasite in the phylum Apicomplexa. As described for other members of Apicomplexa, apical membrane antigen 1 (AMA1) has been shown to be critical for sporozoite invasion of host cells by E. tenella. Recently, an E. tenella paralogue of AMA1 (EtAMA1), dubbed sporoAMA1 (EtAMA3), was identified in proteomic and transcriptomic analyses of E. tenella, but not further characterized. Here, we show that EtAMA3 is a type I integral membrane protein that has 24% -38% identity with other EtAMAs. EtAMA3 has the same pattern of Cys residues in domains I and II of AMA1 orthologs from apicomplexan parasites, but high variance in domain III, with all six invariant Cys residues absent. EtAMA3 expression was developmentally regulated at the mRNA and protein levels. EtAMA3 protein was detected in sporulated oocysts and sporozoites, but not in the unsporulated oocysts or second-generation merozoites. EtAMA3 is secreted by micronemes and is primarily localized to the apical end of sporozoites during host-cell invasion. Additionally, pretreatment of sporozoites with rEtAMA3-specific antibodies substantially impeded their invasion into host cells. These results suggest EtAMA3 is a sporozoite-specific protein that is involved in host-cell sporozoite invasion.

Anticoccidial Effect of Herbal Powder "Shi Ying Zi" in Chickens Infected with Eimeria tenella

Simple Summary

Herbal medicines are playing an increasingly important role in the control of poultry diseases. The present study demonstrated that the herbal powder “Shi Ying Zi” consisting of Cnidium monnieri (L.) Cuss, Taraxacum mongolicum Hand.-Mazz., and sodium chloride could protect chickens from infection with Eimeria tenella through prophylactic or therapeutic administration. The “Shi Ying Zi” powder could improve the survival rate and relative growth rate with the anti-coccidial indexes of 165 (prophylactic effect) and 144 (therapeutic effect), which were equal to positive controls (monensin and sulfamlopyrazine). The “Shi Ying Zi” powder exhibits the potential to control E. tenella infection.

Abstract

Coccidiosis is one of the most economically important diseases affecting the poultry industry. Currently, anticoccidial drugs used in veterinary clinics show many deficiencies, and new control measures are urgently needed. This study presents an anticoccidial herbal powder “Shi Yin Zi”, which consists of Cnidium monnieri (L.) Cuss, Taraxacum mongolicum Hand.-Mazz., and sodium chloride. In chickens infected with Eimeria tenella, supplementation with “Shi Yin Zi” powder for 3 d prior to infection or treatment with “Shi Yin Zi” powder after infection could improve the survival rate and relative growth rate and alleviate the pathological changes in the cecum, liver, and kidney. “Shi Yin Zi” powder could recover the levels of alanine aminotransferase, creatinine, albumin, and triglycerides in serum. The hemorrhage occurrence and total number of oocysts in feces were reduced. The anti-coccidial indexes reached 165 for the prophylactic effect and 144 for the therapeutic effect. The anti-coccidial effects were equal to positive controls (monensin and sulfamlopyrazine). These results suggest that “Shi Ying Zi” powder possesses a potent anticoccidial effect and exhibits the potential to control E. tenella infection.

Comparative Transcriptome Analyses of Drug-sensitive and Drug-resistant Strains of Eimeria tenella by RNA-sequencing

Avian coccidiosis is a widespread and economically significant disease in poultry. At present, treatment of coccidiosis mainly relies on drugs. Anticoccidial drugs can be divided into two categories: ionophorous compounds and synthetic drugs. However, the emergence of drug-resistant strains has become a challenge for coccidiosis control with anticoccidial drugs. To gain insights into the molecular mechanism governing the drug resistance of Eimeria tenella, two drug-resistant strains of E. tenella, one maduramicin-resistant (MRR) strain and one diclazuril-resistant (DZR) strain, were generated. We carried out comparative transcriptome analyses of a drug-sensitive strain (DS) and two drug-resistant MRR and DZR strains of E. tenella using RNA-sequencing. A total of 1,070 differentially expressed genes (DEGs), 672 upregulated and 398 downregulated, were identified in MRR vs. DS, and 379 DEGs, 330 upregulated and 49 downregulated, were detected in DZR vs. DS. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed to better understand the functions of these DEGs. In the comparison of DZR vs. DS, some DEGs were involved in peroxisome, biosynthesis of unsaturated fatty acids, and fatty acid metabolism. In the comparison of MRR vs. DS, some DEGs were involved in glycolysis/gluconeogenesis, regulation of actin cytoskeleton, and DNA replication. In addition, some DEGs coded for surface antigens that were downregulated in two drug-resistant strains involved invasion, pathogenesis, and host-parasite interactions. These results provided suggestions for further research toward unraveling the molecular mechanisms of drug resistance in Eimeria species and contribute to developing rapid molecular methods to detect resistance to these drugs in Eimeria species in poultry.

Eukaryotic elongation factor 2 is involved in the anticoccidial action of diclazuril in the second-generation merozoites of Eimeria tenella

Eimeria tenella, an obligate intracellular parasite, can actively invade the cecal epithelial cells of chickens and cause severe enteric disease. Eukaryotic elongation factor 2 (eEF2) plays a major role in protein synthesis and cell survival. This study aims to explore the exact mechanisms underlying diclazuril inhibition in second-generation merozoites of E. tenella. The eEF2 cDNA of the second-generation merozoites of E. tenella (EtEF2) was cloned by reverse transcriptase polymerase chain reaction and rapid amplification of cDNA ends. Diclazuril-induced expression profiles of EtEF2 were also analyzed. The cloned full-length cDNA (2893 bp) of the EtEF2 nucleotide sequence encompassed a 2499 bp open reading frame (ORF) that encoded a polypeptide of 832 residues with an estimated molecular mass of 93.12 kDa and a theoretical isoelectric point of 5.99. The EtEF2 nucleotide sequence was submitted to the GenBank database with the accession number KF188423. The EtEF2 protein sequence shared 99 % homology with the eEF2 sequence of Toxoplasma gondii (GenBank XP_002367778.1). The GTPase activity domain and ADP-ribosylation domain were conserved signature sequences of the eEF2 gene family. The changes in the transcriptional and translational levels of EtEF2 were detected through quantitative real-time PCR and Western blot analyses. The mRNA expression level of EtEF2 was 2.706 fold increases and the protein level of EtEF2 was increased 67.31 % under diclazuril treatment. In addition, the localization of EtEF2 was investigated through immunofluorescence assay. Experimental results demonstrated that EtEF2 was distributed primarily in the cytoplasm of second-generation merozoites, and its fluorescence intensity was enhanced after diclazuril treatment. These findings indicated that EtEF2 may have an important role in understanding the signaling mechanism underlying the anticoccidial action of diclazuril and could be a promising target for novel drug exploration.