Effect of Acetamizuril on enolase in second-generation merozoites of Eimeria tenella

Comparative proteomic analysis across the developmental stages of the Eimeria tenella

Eimeria tenella is the main pathogen responsible for coccidiosis in chickens. The life cycle of E. tenella is, arguably, the least complex of all Coccidia, with only one host. However, it presents different developmental stages, either in the environment or in the host and either intracellular or extracellular. Its signaling and metabolic pathways change with its different developmental stages. Until now, little is known about the developmental regulation and transformation mechanisms of its life cycle. In this study, protein profiles from the five developmental stages, including unsporulated oocysts (USO), partially sporulated (7 h) oocysts (SO7h), sporulated oocysts (SO), sporozoites (S) and second-generation merozoites (M2), were harvested using the label-free quantitative proteomics approach. Then the differentially expressed proteins (DEPs) for these stages were identified. A total of 314, 432, 689, and 665 DEPs were identified from the comparison of SO7h vs USO, SO vs SO7h, S vs SO, and M2 vs S, respectively. By conducting weighted gene coexpression network analysis (WGCNA), six modules were dissected. Proteins in blue and brown modules were calculated to be significantly positively correlated with the E. tenella developmental stages of sporozoites (S) and second-generation merozoites (M2), respectively. In addition, hub proteins with high intra-module degree were identified. Gene Ontology (GO) and Kyoto Encyclopedia of Gene and Genomes (KEGG) pathway enrichment analyses revealed that hub proteins in blue modules were involved in electron transport chain and oxidative phosphorylation. Hub proteins in the brown module were involved in RNA splicing. These findings provide new clues and ideas to enhance our fundamental understanding of the molecular mechanisms underlying parasite development.

Immune synergistic mechanism of recombinant plasmid adjuvant containing chicken IL-4 and IL-2 fusion genes on chicken coccidia live vaccine

The recombinant plasmid pCI-IL-4-IL-2-EGFP containing fusion genes of chicken IL-4 and IL-2 can be used as an adjuvant to enhance the anticoccidiosis effect of the chicken coccidia live vaccine. The chickens were divided into 3 groups: blank control group, vaccine + pCI-IL-4-IL-2-EGFP adjuvant coimmunization group, and vaccine-only group to investigate the immune synergy mechanism of recombinant plasmid adjuvant pCI-IL-4-IL-2-EGFP. The expressions of IL-2, IL-4, TNF-α, and IFN-γ in chicken sera and tissues were detected by ELISA and RT-qPCR, and the proliferation of T and B lymphocytes and antigen presenting cells (APC) in chicken immune organs and intestines were detected by acid alpha-naphthalase (ANAE) staining, methyl green pyronine (MGP) staining, and immunofluorescence (IF) staining, respectively. Results showed that the mRNA expression of IL-2, IL-4, IFN-γ and the number of activated T and B lymphocytes were significantly upregulated in the spleen and cecum tonsils of chickens in vaccine + pCI-IL-4-IL-2-EGFP group compared with the vaccine-only group on 7 d after vaccination (P < 0.05). Protein contents of IL-2, IL-4 and TNF-α in vaccine + pCI-IL-4-IL-2-EGFP group were significantly increased compared to vaccine-only group on 28 d of inoculation (P < 0.05). The number of T and B lymphocytes and APC in chickens of the vaccine+ pCI-IL-4-IL-2-EGFP group was significantly higher than that of the vaccine-only group in cecum tonsils, thymus and spleen after 14 and 28 d of inoculation (P < 0.05). All results revealed that pCI-IL-4-IL-2-EGFP adjuvant enhanced the immune response of chicken coccidia live vaccine by upregulating the expression of IL-2, IL-4, TNF-α, and IFN-γ and promoting the proliferation of T, B lymphocytes and APCs in chicken intestines and immune organ sites. Moreover, our study provides a theoretical basis for the clinical application of cytogenic plasmids as adjuvants.

In Vitro Transcriptional Response of Eimeria tenella to Toltrazuril Reveals That Oxidative Stress and Autophagy Contribute to Its Anticoccidial Effect

Intestinal coccidiosis is a common parasitic disease in livestock, caused by the infection of Eimeria and Cystoisospora parasites, which results in great economic losses to animal husbandry. Triazine compounds, such as toltrazuril and diclazuril, are widely used in the treatment and chemoprophylaxis of coccidiosis. Unfortunately, widespread drug resistance has compromised their effectiveness. Most studies have focused on prophylaxis and therapeutics with toltrazuril in flocks, while a comprehensive understanding of how toltrazuril treatment alters the transcriptome of E. tenella remains unknown. In this study, merozoites of E. tenella were treated in vitro with 0.5 μg/mL toltrazuril for 0, 1, 2 and 4 h, respectively. The gene transcription profiles were then compared by high-throughput sequencing. Our results showed that protein hydrolysis genes were significantly upregulated after drug treatment, while cell cycle-related genes were significantly downregulated, suggesting that toltrazuril may affect parasite division. The expression of redox-related genes was upregulated and elevated levels of ROS and autophagosomes were detected in the parasite after toltrazuril treatment, suggesting that toltrazuril may cause oxidative stress to parasite cells and lead to its autophagy. Our results provide basic knowledge of the response of Eimeria genes to toltrazuril and further analysis of the identified transcriptional changes can provide useful information for a better understanding of the mechanism of action of toltrazuril against Eimeria.

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.

Effects of diclazuril on the expression of enolase in second-generation merozoites of Eimeria tenella

Eimeria tenella is an obligate intracellular parasite of the chicken cecum; it brings huge economic loss to the chicken industry. Enolase is a multifunctional glycolytic enzyme involved in many processes of parasites, such as infection and migration. In this study, the effect of diclazuril on the expression of enolase in second-generation merozoites of E. tenella (EtENO) was reported. The prokaryotic expression plasmid pET-28a-EtENO was constructed and transformed into Escherichia coli BL21 (DE3). Then, it was subjected to expression under the induction of isopropyl-β-D-1-thiogalactopyranoside. The expressed products were identified and purified. The purified EtENO protein was used for antibody preparation. The EtENO mRNA and protein expression levels were analyzed via real-time PCR and Western blotting. Localization of EtENO on the merozoites was examined by immunofluorescence technique. The mRNA and protein expression levels of EtENO were decreased by 36.3 and 40.36%, respectively, by diclazuril treatment. EtENO distributed in the surface, cytoplasm, and nucleus of the infected/control group. With diclazuril treatment, it was significantly reduced in the surface and cytoplasm and even disappeared in the nucleus of the infected/diclazuril group. These observations suggested that EtENO may play an important role in mechanism of diclazuril anticoccidial action and be a potential drug target for the intervention with E. tenella infection.

Preliminary study of the mechanism of action of ethanamizuril against Eimeria tenella

Ethanamizuril (EZL) is a novel triazine compound with excellent anticoccidial activity. We carried out a preliminary investigation of the effects of EZL on the different life cycle stages of Eimeria tenella. EZL mainly acted on the schizogony stage, with peak activity during the second-generation merozoite stage. We also studied the possible target of EZL by identifying the majorly differentially expressed gene affected by EZL in second-generation merozoites using real-time polymerase chain reaction, and screening for surface antigen proteins (SAGs). The relative expression levels of SAGs were compared by Western blot analysis showing that expression levels of surface antigen family member (SAGfm) and SAG19 were significantly downregulated by EZL. Immunofluorescence analysis indicated that SAGfm and SAG19 were localized on the surface of second-generation merozoites. In addition, fluorescence signals were significantly stronger in second-generation merozoites of infected non-medicated control (INC) group compared with that of the EZL group. Therefore, it was speculated that SAGs might be a potential target of EZL action. The inhibitory effects of anticoccidial drugs on SAG levels in coccidia thus warrant further research.

Proteomic analysis of the second-generation merozoites of Eimeria tenella under nitromezuril and ethanamizuril stress

Background

Eimeria tenella is a highly pathogenic coccidian that causes avian coccidiosis. Both nitromezuril (NZL) and ethanamizuril (EZL) are novel triazine compounds with high anticoccidial activity, but the mechanisms of their action are still unclear. This study explored the response of E. tenella to NZL and EZL by the study of changes in protein composition of the second-generation merozoites.

Methods

Label-free quantification (LFQ) proteomics of the second-generation merozoites of E. tenella following NZL and EZL treatment were studied by LC-MS/MS to explore the mechanisms of action. The identified proteins were annotated and analyzed by Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis and protein-protein interaction (PPI) networks analysis.

Results

A total of 1430 proteins were identified by LC-MS/MS, of which 375 were considered as differential proteins in response to drug treatment (DPs). There were 26 only found in the NZL treatment group (N-group), 63 exclusive to the EZL treatment group (E-group), and 80 proteins were present in both drug groups. In addition, among the DPs, the abundant proteins with significantly altered expression in response to drug treatment (SDPs) were found compared with the C-group, of which 49 were upregulated and 51 were downregulated in the N-group, and 66 upregulated and 79 downregulated in the E-group. Many upregulated proteins after drug treatment were involved in transcription and protein metabolism, and surface antigen proteins (SAGs) were among the largest proportion of the downregulated SDPs. Results showed the top two enriched GO terms and the top one enriched pathway treated with EZL and NZL were related, which indicated that these two compounds had similar modes of action.

Conclusions

LFQ proteomic analysis is a feasible method for screening drug-related proteins. Drug treatment affected transcription and protein metabolism, and SAGs were also affected significantly. This study provided new insights into the effects of triazine anticoccidials against E. tenella.

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.

Immunolocation and enzyme activity analysis of Cryptosporidium parvum enolase

Background

Enolase is an essential multifunctional glycolytic enzyme that is involved in many biological processes of apicomplexan protozoa, such as adhesion and invasion. However, the characteristics of enolase in Cryptosporidium parvum, including the location on the oocyst and the enzyme activity, remain unclear.

Methods

The C. parvum enolase gene (cpeno) was amplified by RT-PCR and sequenced. The deduced amino acid sequence was analysed by bioinformatics software. The gene was expressed in Escherichia coli BL21 (DE3) and purified recombinant protein was used for enzyme activity analysis, binding experiments and antibody preparation. The localisation of enolase on oocysts was examined via immunofluorescence techniques.

Results

A 1,350 bp DNA sequence was amplified from cDNA taken from C. parvum oocysts. The deduced amino acids sequence of C. parvum enolase (CpEno) had 82.1% homology with Cryptosporidium muris enolase, and 54.7–68.0% homology with others selected species. Western blot analysis indicated that recombinant C. parvum enolase (rCpEno) could be recognised by C. parvum-infected cattle sera. Immunolocalization testing showed that CpEno was found to locate mainly on the surface of oocysts. The enzyme activity was 33.5 U/mg, and the Michaelis constant (K_m) was 0.571 mM/l. Kinetic measurements revealed that the most suitable pH value was 7.0–7.5, and there were only minor effects on the activity of rCpEno with a change in the reaction temperature. The enzyme activity decreased when the Ca²⁺, K⁺, Mg²⁺ and Na⁺ concentrations of the reaction solution increased. The binding assays demonstrated that rCpEno could bind to human plasminogen.

Conclusion

This study is the first report of immunolocation, binding activity and enzyme characteristics of CpEno. The results of this study suggest that the surface-associated CpEno not only functions as a glycolytic enzyme but may also participate in attachment and invasion process of the parasite.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2200-y) contains supplementary material, which is available to authorized users.