Avian coccidiosis is a major parasitic disease that poses a significant threat to the poultry industry. Elucidating the regulatory mechanisms of key molecules involved in the interplay between Eimeria and the host immune system is of great importance for the development of novel control strategies. Toll-like receptor 5 (TLR5) is a critical pattern recognition receptor in host innate immunity; however, research on its ligands has primarily focused on bacterial-derived molecules, and Eimeria-derived ligands along with their regulatory mechanisms remain largely uncharacterized. Using immunoprecipitation coupled with proteomics analysis, we identified a novel TLR5 ligand, E. maxima dihydrolipoyl dehydrogenase (EmDLD). In an in vitro macrophage model, recombinant EmDLD (rEmDLD) polarized chicken primary bone marrow-derived macrophages toward an M2-like phenotype. This polarization was characterized by the upregulation of TGFB1 and CD206, alongside the downregulation of TNFA, IL1B, and IL6, without affecting the production of nitric oxide (NO) or reactive oxygen species (ROS). Unexpectedly, in the chicken macrophage cell line HD11, rEmDLD activated the canonical NF-κB and MAPK signaling pathways. Furthermore, rEmDLD promoted maturation of primary bone marrow-derived dendritic cells in vitro, which enhanced T-cell proliferation and increased the proportion of CD4+CD25+ regulatory T cell‑like cells (Treg‑like cells). In vivo experiments demonstrated that immunization with rEmDLD induced the production of specific IgY antibodies in chickens. It moderately alleviated body weight loss following E. maxima infection and reduced oocyst shedding in the jejunum. Our results identify EmDLD as a novel ligand of chTLR5 that induces M2-like macrophage polarization and the generation of Treg-like cells. This study reveals for the first time that Eimeria may modulate host immune responses toward an immunoregulatory state through the EmDLD-TLR5 axis, offering important insights into the mechanisms of immune evasion by Eimeria and the development of novel anti-coccidial intervention strategies.

Toxoplasma gondii establishes infection in hosts by deploying effector proteins that reprogram cytokine-driven immunity. While protozoan parasite-encoded macrophage migration inhibitory factor (MIF) homologs exemplify cytokine mimicry, whether T. gondii targets additional host cytokine axes remains unclear. Here, we identify a T. gondii 3-ketoacyl-CoA reductase (KCR) as a noncanonical cytokine modulator that engages the granulocyte-macrophage colony-stimulating factor (CSF2) receptor alpha chain (CSF2Rα). In HEK293T cells, forward and reverse co-immunoprecipitation (Co-IP) assays demonstrated a specific interaction between KCR and murine CSF2Rα. The recombinant KCR triggered rapid activation of canonical CSF2 signaling in RAW264.7 macrophages, inducing phosphorylation of JAK2 and STAT5 to levels comparable to murine CSF2. Functionally, KCR enhanced NADPH oxidase-dependent oxidative responses, increasing intracellular reactive oxygen species (ROS) and upregulating transcripts encoding core oxidase subunits, including CYBB, CYBA, NCF1, and NCF2. KCR also promoted phagocytic capacity, elevating FITC-dextran uptake and inducing expression of complement, Fc, and scavenger receptor genes, including CR3, CD16, CD64, MSR1, and MARCO. Notably, KCR pretreatment attenuated CSF2-induced JAK2/STAT5 phosphorylation, ROS production, and phagocytosis, consistent with competitive interference with endogenous CSF2-CSF2R signaling. Together, these findings reveal KCR as a previously unrecognized T. gondii factor that targets the CSF2/CSF2R axis to recalibrate macrophage effector functions, expanding the repertoire of parasite strategies for cytokine pathway modulation and highlighting CSF2-CSF2R signaling as a potential interface for mechanistic and therapeutic investigation in toxoplasmosis.

Toxoplasmosis, a globally prevalent zoonosis caused by Toxoplasma gondii (T. gondii), poses major threats to both human and animal health, leading to reproductive losses in livestock and severe disease in immunocompromised individuals. Although enzyme-linked immunosorbent assay (ELISA) and PCR are widely used for diagnosis and surveillance, they may be limited by turnaround time, laboratory instrumentation, and, in the case of serological assays, the need for species-specific reagents. To enable rapid, equipment-minimal detection applicable to multiple host species, we developed a point-of-care (POC) double-antigen sandwich colloidal gold immunochromatographic assay (GICA) based on recombinant surface antigen 2 (rSAG2) of T. gondii. In this assay, rSAG2 served both as the capture antigen immobilized on the test line and as the colloidal gold-conjugated detection probe. Key parameters, including conjugation pH, antigen loading, and buffer composition, were systematically optimized. The resulting strip showed a detection limit of a 1:40 serum dilution, and no cross-reactivity was observed with sera positive for 23 common pathogens from different host species. Good repeatability and storage stability for 4 months at 4°C were also observed. For field evaluation, 409 clinical serum samples from six animal groups (100 chickens, 68 dogs, 30 cats, 81 pigs, 80 yaks, and 50 sheep) were tested, and seropositivity rates ranged from 2.9% to 31.3% across the sampled groups. In a subset of chicken (n = 46) and dog (n = 44) sera tested in parallel with the corresponding commercial ELISA kits, the rSAG2-GICA showed good preliminary agreement, with overall agreement rates of 91.3% and 97.7%, respectively. Collectively, this rSAG2-based GICA shows potential as a rapid and practical tool for on-site serological screening of T. gondii antibodies across multiple host species and may support epidemiological surveillance in diverse animal populations.

Abstract Aphid alarm pheromone, ( E )‐β‐farnesene (EβF), is a key chemical signal responding to predation threats, inducing alarm, escape, and wing differentiation in conspecifics. Beyond facilitating intraspecific communication, EβF also modulates interactions with natural enemies, playing a crucial role in defense. This review explores the chemical composition, biosynthesis pathways, release dynamics, and molecular perception mechanisms of EβF. Furthermore, we discuss its potential applications in pest management, including transgenic traits, slow‐release formulations, and synergistic deployment with plant‐derived enhancers (e.g., methyl salicylate). However, the incorporation of EβF into integrated pest management encounters several challenges, such as high volatility, environmental instability, and aphid adaptability. Future research should focus on optimizing slow‐release technologies, developing multifunctional EβF analogs, integrating gene editing and precision release strategies, and adopting interdisciplinary approaches to improve EβF stability and efficacy.

Chicken coccidia can suppress the host immune response through CD4+CD25+ T cells, compromising the effectiveness of immune prophylaxis and potentially leading to immune failure. However, the role of chicken CD4+CD25+ T cells in chicken coccidia infection is not well understood. This study aimed to elucidate the immunomodulatory function of CD4+CD25+ T cells during Eimeria maxima infection and assess the impact of CD25+ cell depletion on immune response and infection outcomes. The study comprised three trials: (1) examining CD4+CD25+ T cells and cytokine changes post-E. maxima infection, (2) assessing the impact of in vitro CD25+ cell depletion on the immunomodulatory function of peripheral blood mononuclear cells (PBMCs) and (3) evaluating the effects of in vivo CD25+ cell depletion on PBMC function and E. maxima infection. The results revealed that E. maxima infection significantly increased CD4+CD25+ T cell proportions in PBMCs and spleen, along with upregulated mRNA levels of IL-10, TGF-β and IL-4. In vitro CD25+ cell depletion enhanced PBMC proliferation as well as Th1, Th2 and Th17 response. In vivo CD25+ cell depletion partially disrupted E. maxima infection, as evidenced by reduced weight loss, alleviated intestinal lesions, lower oocyst shedding, and an anticoccidial index (ACI) exceeding 120. In conclusion, E. maxima infection upregulates CD4+CD25+ T cells along with their associated cytokines (IL-10 and TGF-β) and the surface molecule CTLA-4; and the depletion of CD25+ cells restores protective Th responses (Th1, Th2 and Th17), while blockade of CD25 in vivo mitigates the E. maxima infection process. This study demonstrates the immunomodulatory role of CD4+CD25+ T cells during E. maxima infection, providing key insights for elucidating the immune evasion mechanisms of this parasite.

Avian coccidiosis caused by Eimeria species threatens the global poultry industry. Current control measures rely mainly on anticoccidial drugs and live vaccines, but drug resistance and safety concerns drive the need for novel vaccines such as subunit vaccines. Among Eimeria species, Eimeria necatrix is one of the most pathogenic. Its life cycle involves sporozoites invading the jejunum and undergoing two generations of schizogony; the released second-generation merozoites then migrate specifically to the cecum for further development—a step essential for completing the life cycle. Previously, we identified EnMIC as the key molecule mediating this cecum-specific invasion, and its essential adhesive domain EnMAR2. In the present study, we evaluated the immunoprotective potential of EnMIC and EnMAR2. Recombinant subunit vaccines of EnMIC and EnMAR2 were administered to chickens. Humoral and cellular immune responses were assessed by measuring serum IgY, intestinal IgA, T-cell subsets (CD4⁺/CD8⁺), and cytokine transcripts (IL-2, IFN-γ, IL-4) in the spleen and cecal tonsils. After challenge with E. necatrix, protective effects were evaluated by survival rate, weight gain, lesion index, oocyst output, and the anticoccidial index (ACI). Both vaccines significantly elevated serum IgY and intestinal IgA levels. They also increased splenic IL‑2, IFN‑γ, and IL‑4 mRNA levels, while downregulating these cytokines in cecal tonsils. Furthermore, the rEnMIC group showed an increased proportion of CD4⁺ T cells in both the spleen and cecal tonsils. In the challenge trial, both the rEnMIC and rEnMAR2 groups exhibited significantly better weight gain, lower lesion index, and greater oocyst reduction than the non‑immunized infected group. Their ACI values were 168.92 and 166.60, respectively. These results demonstrate that EnMIC and EnMAR2, as key mediators of E. necatrix site-specific cecal invasion, can induce both humoral and cellular immune responses when delivered as recombinant protein vaccines. The vaccines effectively alleviated pathological damage, reduced oocyst output, and improved growth performance. Therefore, EnMIC and EnMAR2 represent promising novel vaccine candidates against E. necatrix infection in chickens.

Traditionally, the control of Sitobion avenae (Fabricius) relies heavily on chemical insecticides; however, the long-term use of chemical insecticides has caused hazards to the environment and human health. Eugenol and cinnamaldehyde are important active components of plant essential oils. In this study, the toxicity of these two compounds against S. avenae was determined via fumigation and contact bioassays, and repellent activity tests were conducted to clarify their control effects. The results showed that the contact KD50 values of eugenol and cinnamaldehyde against S. avenae through cuticular penetration were 0.25 μL/mL and 0.11 μL/mL, respectively (applied onto a treated surface area of 30 cm2 per replicate), while their fumigant KD50 values were 7.04 μL/mL and 2.55 μL/mL, respectively (tested in a sealed 125 mL glass vial). Both compounds exhibited repellent activity. At a concentration of 0.75 μL/mL, the repellency rate of cinnamaldehyde was 24.4%, while that of eugenol was 15.6%. However, both compounds displayed a certain attractive effect at the lowest concentration of 0.375 μL/mL. These findings demonstrate that eugenol and cinnamaldehyde exhibit high insecticidal activity against the wheat aphid under laboratory conditions, with dose-dependent repellency and toxicity in simple laboratory assays.

Trehalase can hydrolyze trehalose and is the first key enzyme in the chitin synthesis pathway of arthropods. However, little is known about the function of trehalase in Haemonchus contortus (HcTre). In this study, the purified recombinant HcTre protein (rHcTre) was obtained by prokaryotic expression technology, and it was proved that rHcTre protein has trehalase activity. Western blot results verified that HcTre protein belongs to the excretory/secretory proteins of H. contortus, and rHcTre protein can be recognized by goat serum infected with H. contortus. Moreover, Western blot results demonstrated the expression of the HcTre gene in various developmental stages of H. contortus, with the highest level observed during the egg stage. Meanwhile, the immunofluorescence results revealed a widespread distribution of HcTre protein in adult worms. Interestingly, we found that rat serum against rHcTre protein inhibited the development of larvae by blocking the activity of trehalase. Furthermore, the results showed that rHcTre protein significantly inhibited the proliferation and promoted the apoptosis of goat PBMCs in a dose-dependent manner. This study is expected to further understand the immune escape mechanism of H. contortus and provide new drug targets and vaccine candidate molecules for the prevention and control of the disease.

BackgroundTrehalose-6-phosphate synthase (HcTPS) and trehalose-6-phosphate phosphatase (HcGOB) are key enzymes for trehalose synthesis in Haemonchus contortus. In addition, previous studies have also demonstrated that HcTPS and HcGOB can regulate the function of host immune cells in vitro, and are important immunosuppressive molecules. Therefore, this study evaluated the potential of HcTPS and HcGOB as vaccine candidates through in vitro and in vivo experiments.MethodsTo evaluate the inhibitory effects of polyclonal antibodies on egg hatching and larval development, anti-rHcTPS and anti-rHcGOB antibodies were incubated separately with eggs and first-stage larvae (L1s) under controlled in vitro conditions. For immunization studies, recombinant proteins (rHcTPS and rHcGOB) were formulated with Quil-A adjuvant, and administered to goats through subcutaneous injection. Vaccine efficacy against Haemonchus contortus infection was determined through comprehensive analysis of multiple parasitological parameters, including: (1) egg abnormality rate, (2) hatching success rate, (3) reduction egg output rates, and (4) reduction in adult worm burden.ResultsThe results of in vitro experiments showed that polyclonal antibodies against HcTPS and HcGOB had no effect on the hatching rate of eggs, but significantly affected the development from L1s to infectious third stage larvae (L3s). After immunization with recombinant HcTPS protein (rHcTPS) and recombinant HcGOB protein (rHcGOB), high levels of antigen-specific immunoglobulin G (IgG) were produced in goats, and remained till the end of the experiment. Compared with the Quil-A adjuvant control group, the number of deformed eggs in the rHcTPS protein- immunized group and the rHcGOB protein- immunized group were significantly increased. In the rHcTPS protein-immunized group and the rHcGOB protein-immunized group, the deformity rate of eggs was 9.59% and 17.30%, respectively, and the hatching rate of eggs was reduced by 11.27% and 13.71%, respectively. Moreover, compared with the Quil-A adjuvant control group, the number of eggs and adults in the HcTPS protein- immunized group decreased by 64.47% and 60.93%, respectively, and the number of eggs and adults in the rHcGOB protein- immunized group decreased by 63.97% and 69.54%, respectively. Furthermore, compared with the control group (Quil-A adjuvant), the trehalose content in the rHcTPS protein- immunized group and the rHcGOB protein- immunized group was also significantly reduced.ConclusionsThese findings indicate that rHcTPS and rHcGOB exhibit superior immune protective effects, rendering them promising candidates for vaccine development.

The English green aphid, Sitobion avenae, a major pest of wheat, exhibits classical wing dimorphism. To support research and data sharing on the molecular basis of this trait, we generated full-length transcriptomes from three different developmental stages of winged and wingless morphs using PacBio SMRT and Illumina HiSeq sequencing platforms. The dataset comprises 2,309,013 circular consensus sequences (CCSs), with 85.29% identified as full-length non-chimeric reads (FLNC) reads after filtering. Approximately 282 Gb of PacBio subreads were obtained, with a total of 125,495,799 reads. Functional annotation was performed for 43,219 transcripts (44.3%). Across the developmental stages, differential expression analyses revealed numerous genes with varied expression patterns, with 71 genes identified as potential regulators of wing polymorphism. These candidates are associated with biological processes such as wing development, hormone biosynthesis, energy metabolism, and cell death pathways. This dataset provides a comprehensive molecular resource for investigating the transcriptional basis of wing polyphenism in aphids and may offer insights applicable to other insect systems.

(E)-β-farnesene (EβF), a sesquiterpene widely recognized for its role in aphid alarm signaling, triggers escape behaviors and influences aphid population dynamics. Despite its potential as a biological control agent, the effects of EβF on the English grain aphid Sitobion avenae (Fabricius) (Hemiptera: Aphididae), a major wheat pest, remain insufficiently explored. In this study, we topically applied EβF at a concentration gradient (10 to 1,000 ng/μl) to various developmental stages of S. avenae and assessed their behavioral responses, development, reproduction, and winged offspring ratio under different population densities. Our results revealed that EβF at 10 ng/μl induced significant behavioral changes, including leg shaking, fast walking, and falling from host plants, across all developmental stages. Exposure to 200 ng/μl EβF significantly reduced fecundity by 19.6% and shortened lifespan by 17.8%, while increasing the proportion of winged offspring by 19.8%, particularly under low parental density combined with high offspring density. Field trials further revealed that a higher concentration of EβF (1,000 ng/μl) led to a 25% increase in the proportion of winged offspring compared to controls, with environmental factors such as population density influencing the response. These findings confirm the insecticidal and density-dependent effects of EβF on S. avenae, with transgenerational impacts on wing dimorphism, highlighting its potential for the sustainable aphid control in wheat ecosystems.

Th17 cells play important roles in anti-infective responses. The 15 kDa excretory/secretory protein of Haemonchus contortus (HcES-15) has been identified as a promising immune-protective antigen against H. contortus infection capable of up-regulating IL-17, IL-4 and IL-10 production. To obtain the peptides that primarily induce the Th17 immune response, we amplified and expressed the peptides ES15-1, ES15-2 and ES15-3 from HcES-15. In vitro studies demonstrated that ES15-1 stimulated transcriptional activation of the STAT3/RORγt signaling pathway and induced IL-17 production in goat peripheral blood mononuclear cells (PBMCs). In vivo studies, flow cytometric analysis revealed that subcutaneous injection of PLGA-encapsulated ES15-1 peptide (PLGA-ES15-1, 50 μg) significantly enhanced Th17 cell differentiation in the spleens of BALB/c mouse. Consistent with these findings, ELISA quantification demonstrated that ES15-1 treatment significantly increased serum levels of pro-inflammatory cytokine (IL-17, IL-1, IL-6, and TNF-α). In goat immune protection studies, goats ( n = 6) were subcutaneously immunized with 500 μg of PLGA-ES15-1 on days 0 and 14, followed by infection with H. contortus infective third-stage larvae (iL3s) 1 week post-second immunization. ES15-1 significantly enhanced serum levels of pro-inflammatory cytokines (IL-17, IL-1, IL-6, TNF-α). At autopsy, vaccinated goats exhibited 69.0% ( p < 0.001) reduction of fecal egg counts (FEC) and 50.54% ( p < 0.05) reduction of worm burdens versus controls. Our findings suggested that peptide ES15-1 enhanced Th17 responses through regulation of the STAT3/RORγt pathway, conferring a certain immune protection against H. contortus infection.

Wheat aphids, including Sitobion miscanthi (Takahashi) and Rhopalosiphum padi (Linnaeus), inflict serious damage to wheat crops. Consequently, it is necessary to find a new management option to reduce the damage caused by aphids. Entomopathogenic fungi serve as a tool to control the aphid population build-up. The current study explores a new entomopathogenic fungus that, infests S. miscanthi in China. Using morphological and molecular methods, the isolated colonies were identified as Beauveria brongniartii Sacc. (Petc) (Ascomycota: Cordycypitaceae). Bioassay studies with purified conidial suspensions further confirmed the infectivity to the adult wheat aphids. The results showed that after 6 days of treatment with a conidia concentration of 1.0 x 107 spores/mL, the mortality rates of S. miscanti and R. padi were 97.78 % and 91.11 %, respectively. However, 52.22 % of S. miscanthi and 47.78 % of R. padi adults survived after 7 days of exposure to a conidia concentration of 1.0 x 103 spores/mL of B. brongniartii. Additionally, the semi-lethal time decreased with the increase of conidia concentration of the strain. To further understand and enhance the value of B. brongniartii, we performed whole-genome sequencing and an analysis of its strain. The genome length was 2,295,663,102 bp and 316 contigs, with an average length of 7,264,756.71 bp. Moreover, database alignment identified 455 CAZyme, 1643 TCDB, and 2850 PHI genes. The current study also explored five surface proteins of B. brongniartii Y618 that worked best against wheat aphids. To our knowledge, this is the first report of the pathogenicity of B. brongniartii against wheat aphids, and it could serve as a potential candidate for an integrated pest management plan.

Toxoplasma gondii infects nucleated cells of warm-blooded animals and cause zoonotic toxoplasmosis. Lysine lactylation, as a novel post-translational modification, is essential for epigenetic regulation and cellular processes, and proteomic analyses have shown that lactylated proteins are involved in a wide range of biological processes including energy metabolism, gene regulation, and protein biosynthesis. Additionally, protein lactylation is prevalent in T. gondii, while its regulatory mechanisms have not been fully understood. In this study, we investigated the role of T. gondii phosphofructokinase-2 (TgPFKII) and the adenosine-5'-monophosphate-activated protein kinase (AMPK) signaling pathway in the invasion, replication, and lactylation regulation of T. gondii. We localized TgPFKII in the cytoplasm of T. gondii tachyzoites and demonstrated its necessity for parasite growth and protein lactylation through auxin-induced degradation. Our results showed that inhibition of the AMPK pathway led to decreased TgPFKII expression and reduced protein lactylation levels. Furthermore, AMPK-specific inhibitors significantly impaired parasite invasion and proliferation. These findings highlight TgPFKII as a crucial regulator of lactylation and underscore the importance of the AMPK pathway in T. gondii's pathogenic mechanisms, offering potential targets for therapeutic intervention.IMPORTANCEUnderstanding the intricate mechanisms by which Toxoplasma gondii invades and proliferates within host cells is essential for developing novel therapeutic strategies against toxoplasmosis. This study focuses on the pivotal roles of T. gondii phosphofructokinase-2 (TgPFKII) and the adenosine-5'-monophosphate-activated protein kinase (AMPK) signaling pathway in regulating protein lactylation in association with parasite invasion and growth. By elucidating the cellular localization and functional importance of TgPFKII, as well as its regulation through AMPK-specific inhibitors, we provide comprehensive insights into the metabolic and signaling networks that underpin T. gondii pathogenicity. Our findings reveal that TgPFKII is a critical regulator of lactylation and that the AMPK pathway significantly influences T. gondii's ability to invade and replicate within host cells. These insights pave the way for targeted interventions aimed at disrupting key metabolic and signaling pathways in T. gondii, potentially leading to more effective treatments for toxoplasmosis.

Insect odorant-binding proteins (OBPs) are promising molecular targets for developing novel pest management strategies by modulating chemoreception-driven behaviors. The tea gray geometrid Ectropis grisescens (Lepidoptera, Geometridae) is a major pest in tea plantations, causing substantial economic losses in China. In this study, we identified 18 OBPs from E. grisescens antennal transcriptome. All of the encoded proteins possessed N-terminal signal peptides and conserved cysteine residues, behaviors which are characteristic of insect OBPs. Phylogenetic analysis categorized these proteins into plus-C, minus-C, and classic OBP subfamilies. MEME motif analysis identified conserved sequence features potentially involved in odor detection. Tissue- and sex-specific expression profiling showed that EgriGOBP1-2, OBP3, OBP8, and OBP13 were highly expressed in the antennae of both sexes, suggesting roles in olfactory communication. Among them, EgriGOBP1-2, OBP3, and OBP13 exhibited similar expression levels between males and females, while other EgriOBPs were predominantly expressed in the legs, wings, or other tissues, indicating additional physiological functions beyond chemoreception. To investigate functional specificity, we selected antenna-enriched EgriGOBP2 for ligand-binding analysis. Fluorescence binding assays demonstrated that EgriGOBP2 exhibited broad binding affinity toward 8 of 12 host volatiles and 11 of 12 plant essential oil-derived volatiles. These combined findings lay the foundation for mechanistic studies of chemical recognition in E. grisescens and provide insights into the development of ecologically friendly pest control alternatives.

Eimeria maxima (E. maxima) infection inhibits the expression of IFN-γ, a cytokine that is essential for the Th1 immune response and plays a key role in combating this parasite. In our preliminary investigations, we identified the E. maxima surface antigen (EmSAG) as an inhibitory molecule of IFN-γ. EmSAG was screened and characterised from an E. maxima sporozoite cDNA expression library. The present study aimed to evaluate the immunomodulatory effects of EmSAG on chicken peripheral blood mononuclear cells (PBMCs) and various T cell subsets. We analysed cell proliferation, nitric oxide (NO) release, and cytokine transcription. The results revealed that EmSAG boosts PBMC proliferation and promotes differentiation of CD4+/CD8+ T cells. Additionally, stimulation with EmSAG significantly inhibited NO release and IFN-γ transcription while enhancing the transcription of IL-4, IL-10, and TGF-β1 in chicken PBMCs. The sorting purity of T cell subsets was as follows: CD8+ (96.90

Toll-like receptor (TLR)-mediated recognition of specific ligands is critical for initiating innate immunity against Eimeria infections. However, the avian-specific TLR15 has unclear immunological functions, including its specific ligands and role in anti-coccidia immunity. In this study, an aspartyl protease from Eimeria tenella (EteASP) was identified as a potential TLR15 ligand by co-immunoprecipitation. Two distinct TLR15-expressing innate immune cell populations, macrophages and dendritic cells, were employed as models to investigate the immune responses triggered by recombinant EteASP protein (rEteASP). In macrophages, rEteASP induced robust immune activation, associated with the stimulation of both NF-κB and MAPK pathways. This activation correlated with increased production of pro-inflammatory cytokines (IL-1β, IL-6, TNF-α), nitric oxide, and reactive oxygen species, alongside enhanced phagocytosis. Furthermore, rEteASP promoted classical dendritic cell activation in chicken bone marrow-derived dendritic cells, marked by stellate morphology and upregulated CD11c and MHC II surface expression. The activation patterns in chBMDCs mirrored those in macrophages, characterized by increased production of immune mediators. A mixed lymphocyte reaction (MLR) further demonstrated that rEteASP-activated dendritic cells efficiently triggered naive T cell activation, driving a shift towards balanced Th1/Th2-type cellular immune response. Collectively, these findings establish EteASP as a potent immunomodulator capable of activating key innate immune effector functions in macrophages and dendritic cells, and bridging to adaptive immunity. Our data implicate TLR15 as a potential receptor contributing to these responses, broadening the investigation of TLR15 ligands in protozoa and offering novel insights into Eimeria-host immune interactions. However, the potential involvement of additional pattern recognition receptors in EteASP recognition and the definitive role of TLR15 requires further investigation.

Chicken coccidiosis caused by the Eimeria parasites, including E. acervuline, E. brunetti, E. maxima, E. mitis, E. necatrix, E. praecox and E. tenella, is one of the most economically important chicken diseases. The main measure to control chicken coccidiosis is chemoprophylaxis. However, the concerns of public about the over chemical residues in products and the strict legislation to limit the applications of drugs and the residues in products push chicken farmers to turn to the vaccination strategy to control coccidiosis. While the antigen diversity of Eimeria significantly decreased the traditional live vaccines. The cryptic strains of Eimeria, which have recently appeared and spread widely, can evade all commercial coccidiosis vaccines, thus becoming an emerging threat to global poultry production. For this reason, the development of universal subunit vaccines using the conserved proteins of Eimeria, effective against all species including the cryptic strains infecting chickens, is crucial for the sustainable development of global poultry industry. In this article, we reviewed the research progresses on the conserved proteins of Eimeria, including stage conserved proteins, species conserved proteins and both stage and species conserved proteins, with their possible applications in the development of universal subunit vaccines. Meanwhile, the cytokines and polymer-based nanomaterials used as adjuvants to enhance the protections of subunit vaccines were also summarized.