Recombinant ubiquitin-conjugating enzyme of Eimeria maxima induces immunogenic maturation in chicken splenic-derived dendritic cells and drives Th1 polarization in-vitro

Expression of IL-1β in transgenic Eimeria necatrix enhances the immunogenicity of parasites and promotes mucosal immunity against coccidiosis

Anticoccidial vaccines comprising living oocysts of Eimeria tenella, Eimeria necatrix, Eimeria maxima, and Eimeria acervulina are used to control coccidiosis. This study explored the potential of IL-1β to act as a molecular adjuvant for enhancing the immunogenicity of Eimeria necatrix and mucosal immunity. We engineered E. necatrix to express a functional chIL-1β (EnIL-1β) and immunized chickens with oocysts of the wild type (EnWT) and tranegenic (EnIL-1β) strains, respectively. The chickens were then challenged with EnWT oocysts to examine the immunogenicity-enhancing potential of chIL-1β. As expected, the oocyst output of EnIL-1β-immunized chickens was significantly reduced compared to those immunized using EnWT. No difference in body weight gain and lesion scores of EnIL-1β and EnWT groups was observed. The parasite load in the small intestine and caeca showed that the invasion and replication of EnIL-1β was not affected. However, the markers of immunogenicity and mucosal barrier, Claudin-1 and avian β-defensin-1, were elevated in EnIL-1β-infected chickens. Ectopic expression of chIL-1β in E. necatrix thus appears to improve its immunogenicity and mucosal immunity, without increasing pathogenicity. Our findings support chIL-1β as a candidate for development of effective live-oocyst-based anticoccidial vaccines.

Gene cloning, expression, and enzyme kinetics analysis of Eimeria tenella 2- methylcitrate synthase

In prokaryotes and lower eukaryotes, 2-methylcitrate cycle (2-MCC) is the main pathway for propionate decomposition and transformation, but little is known about the 2-MCC pathway of Eimeria tenella. The analysis of genomic data found that the coding gene of 2- methylcitrate synthase (EC 2.3.3.5, PrpC) exists in E. tenella, which is a key enzyme of 2-MCC pathway. Through the search analysis of the database (ToxoDB), it was found that ETH_ 00026655 contains the complete putative sequence of EtprpC. In this study, we amplified the ORF sequence of EtprpC based on putative sequence. Then, prokaryotic expression, enzyme activity and kinetic analysis was performed. The results showed that the EtprpC ORF sequence was 1272 bp, encoding a 46.3 kDa protein comprising 424 amino acids. Enzyme activity assays demonstrate linearity between the initial reaction rate (OD/min) and EtPrpC concentration (ranging from 1.5 to 9 µg/reaction), with optimal enzyme activity observed at 41°C and pH 8.0. The results of enzymatic kinetic analysis showed that the Km of EtPrpC for propionyl-CoA, oxaloacetic acid, and acetyl-CoA was 5.239 ± 0.17 mM, 1.102 ± 0.08 μM, and 5.999 ± 1.24 μM, respectively. The Vmax was 191.11 ± 19.1 nmol/min/mg, 225.48 ± 14.4 nmol/min/mg, and 370.02 ± 25.8 nmol/min/mg when EtPrpC concentration at 4, 6, and 8 μg, respectively. Although the ability of EtPrpC to catalyze acetyl-CoA is only 0.11% of its ability to catalyze propionyl-CoA, it indicates that the 2-MCC pathway in E. tenella is similar to that in bacteria and may have a bypass function in the TCA cycle. This study can provide the theoretical foundation for the new drug targets and the development of new anticoccidial drugs.

An Eimeria maxima Antigen: Its Functions on Stimulating Th1 Cytokines and Protective Efficacy Against Coccidiosis

A consensus is that the Th1 immune response plays a predominant role against avian coccidiosis. Therefore, an antigen with the ability to induce Th1 cytokine responses is an ideal candidate for the development of coccidiosis vaccines. In our previous study, EmARM-β, a Th1 cytokines-stimulating antigen, was screened from the cDNA expression library of Eimeria maxima (E. maxima). Herein, we verified its stimulative effects on Th1 cytokine productions and evaluated its protective efficacy against E. maxima infection. Recombinant EmARM-β protein was expressed, and eukaryotic expression plasmid pVAX1-EmARM-β was also constructed for the immunization of birds. An immunofluorescence assay was performed to detect the native form of EmARM-β protein in the stage of sporozoites. Expressions of specific transcription factors and cytokines in immunized chickens were measured using qPCR and ELISA to verify its stimulating function on Th1 cytokines. Specific IgG antibody levels and T lymphocyte subpopulation in the immunized chickens were detected using ELISA and indirect flow cytometry to determine induced immune responses. The results showed that EmARM-β native protein is massively expressed in the sporozoites stage of E. maxima. Effective stimulation from the EmARM-β antigen to T-bet and Th1 cytokines (IL-2 and IFN-γ) was observed in vivo. After being immunized with rEmARM-β or pVAX1-EmARM-β, significant promotion to the proportion of CD4+ and CD8+ T cells and the level of antigen-specific IgG antibodies in immunized chickens was also observed. Furthermore, vaccination with rEmARM-β antigen or pVAX1-EmARM-β resulted in alleviated weight loss and enteric lesion, reduced oocyst output, and higher anticoccidial index (ACI) in challenged birds. These results indicate that EmARM-β antigen can effectively stimulate the expression of Th1 cytokines and initiate host immune responses, providing moderate protective efficacy against E. maxima. Notably, EmARM-β protein is a promising candidate for developing a novel anticoccidial vaccine.

Characteristics of Biotin lipoyl attachment and 2-oxoacid dehydrogenase acyltransferase of the parasitic nematode Haemonchus contortus and its modulatory functions on goat PBMCs in vitro

Biotin lipoyl attachment and 2-oxoacid dehydrogenase acyltransferase (BLAODA), as an essential excretion of Haemonchus contortus (HcESPs), was identified to have antigenic functions. T helper-9 (Th9) cells secrete interleukin (IL)-9, a signature cytokine associated with tumour immunology, allergy and autoimmunity. Nonetheless, the understanding of modulatory functions of BLAODA on Th9 and other immune cells is limited. In this study, the BLAODA gene was cloned, and the recombinant (r) protein of BLAODA (rHcBLAODA) was expressed and immunoblotting was performed. The results revealed that HcBLAODA gene was successfully cloned and rHcBLAODA protein was expressed. The localization of rHcBLAODA was confirmed on the surface of gut sections from adult H. contortus. The rHcBLAODA protein capability to react precisely with anti-H. contortus antibodies were confirmed by immunoblotting and immunofluorescence assay (IFA). Further functional analysis showed that interaction of rHcBLAODA with host cells significantly enhanced Th9 cells generation, IL-9 expression, nitric oxide production and cell apoptosis while suppressing the cells proliferation and cells migration depending on the concentration. Overall, these findings suggest that rHcBLAODA protein could modulate the host immune response by inducing Th9 cells to secrete IL-9 cytokine in vitro.

Characterization of immunological properties of chicken chemokine CC motif ligand 5 using new monoclonal antibodies

CCL5 (formerly RANTES) belongs to the CC (or β) chemokine family and is associated with a plethora of inflammatory disorders and pathologic states. CCL5 is mainly produced and secreted by T cells, macrophages, epithelial cells, and fibroblasts and acts as a chemoattractant to recruit effector cells to the inflammation sites. Chicken CCL5 (chCCL5) protein is closely related to avian CCL5 orthologs but distinct from mammalian orthologs, and its modulatory roles in the immune response are largely unknown. The present work was undertaken to characterize the immunological properties of chCCL5 using the new sets of anti-chCCL5 mouse monoclonal antibodies (mAbs). Eight different mAbs (6E11, 6H1, 8H11, 11G1, 11G11, 12H1, 13D1, and 13G3) were characterized for their specificity and binding ability toward chCCL5. Two (13G3 and 6E11) of them were selected to detect native chCCL5 in chCCL5-specific antigen-capture ELISA. Using 13G3 and 6E11 as capture and detection antibodies, respectively, the ELISA system detected serum chCCL5 secretions in Clostridium perfringens- and Eimeria-infected chickens. The intracellular expressions of chCCL5 in primary cells or cell lines derived from chickens were validated in immunocytochemistry and flow cytometry assays using both 13G3 and 6E11 mAbs. Furthermore, 6E11, but not 13G3, neutralized chCCL5-induced chemotaxis in vitro using chicken PBMCs. These molecular characteristics of chCCL5 demonstrate the potential application of anti-chCCL5 mAbs and CCL5-specific antigen-capture detection ELISA for detecting native chCCL5 in biological samples. The availability of these new immunological tools will be valuable for fundamental and applied studies in avian species.

Protective Immunity Induced by an Eimeria tenella Whole Sporozoite Vaccine Elicits Specific B-Cell Antigens

Simple Summary

Coccidiosis caused by Eimeria tenella is a dreadful disease with a significant economic impact to the poultry industry. The disease has been controlled by routine medication of feed with synthetic chemicals or ionophore drugs. However, the rising appearance of drug resistance and public demands for reduced drug use in poultry production have driven a dramatic change, replacing anticoccidial drugs with alternative methods, such as vaccination with either virulent or attenuated Eimeria oocysts. Based on preliminary studies, the immune protection evaluating whole-sporozoites of E. tenella vaccine was verified. After this vaccine provided successful protection, the humoral response of a heterologous species like the rabbit was compared with the natural host immune response. Several B-cells antigens from the E. tenella sporozoite suitable for a genetically engineered vaccine were identified. Vaccination with newly identified recombinant antigens offers a feasible alternative for the control of avian coccidiosis into the broiler barns favoring the gradual withdrawal of the anticoccidial drugs.

Abstract

This study investigated protection against Eimeria tenella following the vaccination of chicks with 5.3 × 10⁶E. tenella whole-sporozoites emulsified in the nanoparticle adjuvant IMS 1313 N VG Montanide™ (EtSz-IMS1313). One-day-old specific pathogen-free (SPF) chicks were subcutaneously injected in the neck with EtSz-IMS1313 on the 1st and 10th days of age. Acquired immunity was assayed through a challenge with 3 × 10⁴ homologous sporulated oocysts at 21 days of age. The anticoccidial index (ACI) calculated for every group showed the effectiveness of EtSz-IMS1313 as a vaccine with an ACI of 186; the mock-injected control showed an ACI of 18 and the unimmunized, challenged control showed an ACI of −28. In a comparison assay, antibodies from rabbits and SPF birds immunized with EtSz-IMS1313 recognized almost the same polypeptides in the blotting of E. tenella sporozoites and merozoites. However, rabbit antisera showed the clearest recognition pattern. Polypeptides of 120, 105, 94, 70, 38, and 19 kDa from both E. tenella life cycle stages were the most strongly recognized by both animal species. The E. tenella zoite-specific IgG antibodies from the rabbits demonstrated the feasibility for successful B cell antigen identification.

The immunogenic maturation of goat monocyte-derived dendritic cells and upregulation of toll-like receptors by five antigens of Haemonchus contortus in-vitro

Previously, it was found that several proteins of Haemonchus contortus were involved in the stimulation of the host immune system. However, the information about the selection of superlative antigens with immunogenic efficacies on host DCs is lacking. In the current study, the stimulatory effects of five recombinant proteins (elongation factor-1α, arginine kinase, ES-15, ES-24, and ADP-ribosylation factor 1) of H. contortus on the maturation of goat monocyte-derived dendritic cells (md-DCs) were reported. Recombinant proteins were purified separately in E. coli expression and incubated with isolated goat peripheral blood mononuclear cells (PBMC). Immunofluorescence assay (IFA) results confirmed the binding of these molecules to the md-DC's surface as compared to control groups. In the flow cytometry analysis, recombinant proteins induced md-DC stimulation via the up-regulation of the expression of the costimulatory molecule (CD80) and MHC-II. Quantitative RT-PCR data showed a significant increase in the expression of specific genes of the WNT and toll-like receptor (TLR) signaling pathways. The result of ELISA indicated the higher levels of cytokine (IL-10, IL-12, IFN-γ, and TNF-α) secretion in the md-DC compared to the negative (pET-32a His-Tag) and blank (PBS) control groups. The data gives valuable support in the selection of potential antigens for future studies on the immunomodulation of the host against the infection of H. contortus.

Actin-depolymerizing factor from Eimeria tenella promotes immunogenic function of chicken dendritic cells

Dendritic cells play a crucial role in inducing antigen-specific immunity to pathogens. During host-parasite interaction, host immune response to the parasite molecules is considered essential for recognizing novel antigens for control strategies. Therefore, in the present study, chicken dendritic cells (DCs) (ChDCs), derived from spleens were used to evaluate their capacity to proliferate and differentiate autologous T lymphocytes in response to actin-depolymerizing factor from Eimeria tenella (EtADF). Immunoblot analysis showed that recombinant EtADF protein (rEtADF) was able to interact with rat anti-rEtADF antibodies. The immunofluorescence test confirmed rEtADF binding on ChDCs surface. Flow cytometric analysis revealed that phenotypes for MHCII, CD1.1, CD11c, CD80, and CD86 were increased in ChDCs after rEtADF treatment. qRT-PCR results indicated that ChDCs triggered TLR signaling in response to rEtADF, and suppressed Wnt signaling. Transcript levels of CD83, CCL5, and CCR7 in ChDCs were improved following rEtADF treatment. In addition, rEtADF promoted DC-directed T cell proliferation and differentiation of naïve T cells into CD3⁺/CD4⁺ T cells in DC/T cell co-incubation system. Cytokine analysis of rEtADF-pulsed ChDCs showed increased levels of IL-12 and IFN-γ, while IL-10 and TGF-β remained unchanged. Moreover, rEtADF-treated ChDCs enhanced production of IFN-γ when incubated with T cells, and IL-4 secretion remained unchanged. Our findings indicted that rEtADF could facilitate the polarization of Th1 immune cells by triggering both host DCs and T cells. Our findings provide useful insights into future work aimed at anticoccidial vaccine strategies.

Glyceraldehyde-3-phosphate dehydrogenase from Eimeria acervulina modulates the functions of chicken dendritic cells to boost Th1 type immune response and stimulates autologous CD4+ T cells differentiation in-vitro

Dendritic cells (DCs) play a pivotal role to amplify antigen-specific immune responses. Antigens that sensitize T cells via antigen-presentation by DCs could enhance the capacity of host immunity to fight infections. In this study, we tested the immunogenic profiles of chicken DCs towards Glyceraldehyde-3-phosphate dehydrogenase from Eimeria acervulina (EaGAPDH). Immunoblot analysis showed that recombinant EaGAPDH (rEaGAPDH) protein was successfully recognized by rat sera generated against rEaGAPDH. Interaction and internalisation of rEaGAPDH by chicken splenic-derived DCs (chSPDCs) was confirmed by immunofluorescence analysis. Flow cytometry revealed that chSPDCs upregulated MHCII, CD1.1, CD11c, CD80, and CD86 cell-surface markers. Moreover, mRNA expressions of DC maturation biomarkers (CCL5, CCR7, and CD83) and TLR signalling genes (TLR15 and MyD88) were also upregulated whereas those of Wnt signalling were non-significant compared to negative controls. rEaGAPDH treatment induced IL-12 and IFN-γ secretion in chSPDCs but had no effect on IL-10 and TGF-β. Likewise, DC-T cell co-culture promoted IFN-γ secretion and the level of IL-4 was unaffected. Proliferation of T cells and their differentiation into CD3⁺/CD4⁺ T cells were triggered in chSPDCs-T cells co-culture system. Taken together, rEaGAPDH could promote Th1 polarization by activating both host DCs and T cells and sheds new light on the role of this important molecule which might contribute to the development of new DCs-based immunotherapeutic strategies against coccidiosis.