Involvement of T Cell Immunity in Avian Coccidiosis

Effects of a laminarin-rich algal extract on caecal microbiota composition, leukocyte counts, parasite specific immune responses and growth rate during Eimeria tenella infection of broiler chickens

Coccidiosis, infection with protozoan parasites of genus Eimeria, is a major problem in poultry husbandry world-wide. The disease is currently managed by coccidiostats and live vaccines, but these approaches are not sustainable. Hence, it is important to identify new means to control the infection and/or ameliorate its detrimental effects on gut health. Laminarin, a β-glucan found in marine brown algae, has prebiotic and bioactive properties that could be beneficial in coccidiosis control. The present study aimed to examine the potential of laminarin as an immunostimulatory and microbiota-regulatory compound in broiler chickens infected with E. tenella. Chickens were continuously fed a diet supplemented with a laminarin-rich algal extract (AE) from first feed and subsequently infected with E. tenella at 19 days old. The outcome of infection including caecal microbiota and some immune parameters were monitored during the experiment. Results showed that AE supplementation affected some lymphocyte subpopulations, with increased numbers of TCRγ/δ+CD8-, B-cells and CD4-CD8αβ+ cells and lower numbers of CD4+CD8αα+ cells in blood and increased proportions of CD4-CD8αβ+ spleen cells compared to those in control chickens. The AE diet did not affect parasite excretion, lesion scores or E. tenella specific T-cell responses. However, reductions of E. tenella induced contraction of Bifidobacteriaceae and expansion of Clostridiaceae in caecal microbiota were observed for AE fed chickens compared to chickens fed the control diet. Thus, AE feed supplementation induced some immunostimulatory activity in chickens and affected some of the alterations in caecal microbiota evoked by E. tenella infection.

Growth performance and immune response of broilers during active Eimeria infection are modified by dietary inclusion of canola meal or corn-DDGS in reduced-protein corn-soybean meal diets

The objective of this experiment was to study the effects of partial replacement of soybean meal (SBM) with canola meal (CM) or corn-distillers' dried grains with solubles (cDDGS) in reduced-protein (RP) diets for Eimeria-infected broilers. A total of 1120 broiler chicks were distributed in a 4 × 2 (4 diets × with or without infection) factorial arrangement with 7 replicates per treatment and 20 birds per replicate. The 4 diets, fed between d 7 and 42, were (i) a standard diet with crude protein at 200 g/kg (SP); (ii) a RP (crude protein at 160 g/kg) corn-SBM diet (RP-SBM); (iii) a RP diet in which 80 g/kg CM replaced 60 g/kg SBM (RP-CM); and (iv) a RP diet in which 100 g/kg cDDGS replaced 50 g/kg SBM (RP-cDDGS). On d 15, birds were infected with mixed Eimeria (+E) oocysts. Birds and feed were weighed at intervals for growth performance, and samples for immunology responses were collected on d 21. The results showed as follows: 1) during the acute infection phase, diet × Eimeria infection was shown by the diets having no effect in the uninfected group. In contrast, the RP-SBM diet tended to produce higher (P < 0.10) weight gain among the infected birds. The d 42 body weight was greater (P = 0.001) for the uninfected birds. 2) There was a significant diet × Eimeria infection on bile anti-Eimeria immunoglobulin A (IgA) concentrations (P = 0.015), splenocyte proliferation, macrophage nitric oxide (NO) production (P < 0.001), and cecal tonsil interleukin (IL)-17 mRNA amounts (P < 0.001). Most of these responses were not influenced by the diets in the uninfected birds. However, among the infected birds, birds fed RP-SBM had higher (P < 0.05) bile IgA than those fed SP or RP-cDDGS. For the spleen, the interaction was that birds fed RP-SBM or RP-cDDGS diets had the highest or lowest NO production, respectively, and birds that received RP-SBM had greater (P < 0.05) splenic CD8+:CD4+ cell ratio than other diets. In conclusion, partial replacement of SBM with CM or cDDGS had only a marginal effect on d 42 body weight and FCR of the broiler chickens receiving the RP diets. In contrast, these had a negative impact on the immune responses of the broiler chickens.

Supplementation of Parachlorella sp. in feed promote the gut microbiome colonization and fecal IgA response of broiler in both early and late period

This study evaluated the effects of Parachlorella sp. KSN1 (PA) supplementation on the gut microbiota and intestinal immunity of broilers of different ages. A total of 180 Ross 308 broiler chicks were weighed and divided into early (1 to 10 days post hatch) and late (11 to 28 days post hatch) periods, with six replicates of 10 chicks per cage assigned to two dietary groups. The experimental diets included a corn-soybean meal-based control diet and a treatment diet supplemented with 0.5% PA, replacing corn or corn starch, and fed ad libitum for the assigned experimental period. On days 10 and 28, two broilers from each of the six replicate cages, with 7 broilers per cage in each group, were selected and euthanized, and cecal feces and intestinal tissue samples were collected. PA supplementation did not significantly affect broilers growth performance during both the early and the late periods. However, PA supplementation altered the cecal microbiome, with Clostridiaceae and Clostridium exhibiting prominent and consistent changes. In terms of intestinal immunity, PA supplementation significantly increased the number of CD3+ and CD4+ T cells when administered only during the early period. Cecal IgA levels were significantly increased by PA supplementation during both the early and late periods. A significant positive correlation was observed between IgA, Clostridiaceae and Clostridium during the early and late periods. Gene expression analysis identified 40 upregulated genes, including polymeric immunoglobulin receptor (pIgR), and 142 downregulated genes, including marginal zone B and B1 cell specific protein and immunoglobulin lambda-like polypeptide 1 that were associated with the IgA response in PA-treated broilers during the early period. This study demonstrated that PA supplementation promotes gut microbial colonization and intestinal immunity development during the early age of broilers. These findings suggest that the early growth period of broilers is the optimal time for dietary immunomodulation to promote gut health in broilers.

Eimeria: Navigating complex intestinal ecosystems

Eimeria is an intracellular obligate apicomplexan parasite that parasitizes the intestinal epithelial cells of livestock and poultry, exhibiting strong host and tissue tropism. Parasite-host interactions involve complex networks and vary as the parasites develop in the host. However, understanding the underlying mechanisms remains a challenge. Acknowledging the lack of studies on Eimeria invasion mechanism, we described the possible invasion process through comparative analysis with other apicomplexan parasites and explored the fact that parasite-host interactions serve as a prerequisite for successful recognition, penetration of the intestinal mechanical barrier, and completion of the invasion. Although it is recognized that microbiota can enhance the host immune capacity to resist Eimeria invasion, changes in the microenvironment can, in turn, contribute to Eimeria invasion and may be associated with reduced immune capacity. We also discuss the immune evasion strategies of Eimeria, emphasizing that the host employs sophisticated immune regulatory mechanisms to suppress immune evasion by parasites, thereby sustaining a balanced immune response. This review aims to deepen our understanding of Eimeria-host interactions, providing a theoretical basis for the study of the pathogenicity of Eimeria and the development of novel anticoccidial drugs.

Effect of orally administered B. subtilis-cNK-2 on growth performance, immunity, gut health, and gut microbiome in chickens infected with Eimeria acervulina and its potential as an alternative to antibiotics

This study investigated the best oral delivery strategy (gavage or feed) for the B. subtilis expressing the chicken anti-microbial peptide cNK-2 (B. subtilis-cNK-2) in comparison to monensin, in chickens challenged with Eimeria acervulina (E. acervulina). A total of 120 broiler chickens were randomly allocated into 5 treatment groups in a completely randomized design: 1) uninfected chickens fed with basal diet (NC), 2) E. acervulina-infected chickens fed a basal diet (PC), 3) E. acervulina-infected chickens fed a basal diet supplemented with 90 mg monensin/kg feed (MO), 4) E. acervulina-infected chickens fed a basal diet and orally gavaged with B. subtilis-cNK-2 at 1 × 1010 cfu/d (CNK-O), and 5) E. acervulina-infected chickens fed a basal diet mixed with B. subtilis-cNK-2 at 1 × 1010 cfu/kg feed (CNK-F). The challenge consisted of 5,000 sporulated E. acervulina oocysts through oral gavage on d 15. Body weights were measured on d 7, 14, 21, and 23. Duodenal tissue and digesta samples were collected at 6 d postinfection (dpi) to assess the gut integrity, oxidative stress, mucosal immunity, and the gut microbiome. Fecal samples were collected from 6 to 8 dpi to enumerate the oocyst shedding. Chickens in the CNK-O group showed improved (P < 0.05) growth performance, gut integrity, and mucosal immunity compared to PC, comparable to chickens in the MO group. Chickens in the MO, CNK-F, and CNK-O treatment groups all showed lower (P < 0.05) oocyst shedding compared to PC chickens. Moreover, distinct cytokine profile, oxidative stress measures, tight junction proteins, and shifts in the gut microbiome with associated functional changes were observed in all challenge groups. In conclusion, we showed that the oral administration of B. subtilis-cNK-2 improved growth performance, enhanced local protective immunity, and reduced fecal oocyst shedding in broiler chickens infected with E. acervulina, demonstrating potential use of B. subtilis-cNK-2 as an alternative to antibiotics to protect chickens against coccidiosis.

Transcriptomic analysis uncovers a biphasic response to precocious Eimeria acervulina infection in chicken duodenal tissue

Live anticoccidial vaccines, either formulated with unattenuated or attenuated Eimeria parasites, are powerful stimulators of chicken intestinal immunity. Little is known about the dynamics of gene expression and the corresponding biological processes of chicken responses against infection with precocious line (PL) of Eimeria parasites. In the present study, we performed a time-series transcriptomic analysis of chicken duodenum across 15 time points from 6 to 156 hours post-infection (p.i.) with PL of E. acervulina. A high-quality profile showing two distinct changes in chicken duodenum mRNA expression was generated during the infection of Eimeria. Early response revealed that activation of the chicken immune response was detectable from 6 h.p.i., prominent genes triggered during the initiation of asexual and sexual parasite growth encompass immune regulatory effects, such as interferon gamma (IFN-γ), interferon regulatory factor 1 (IRF1), and interleukin-10 (IL10). The late response was identified significantly associating with maintaining cellular structure and activating lipid metabolic pathways. These analyses provide a detailed depiction of the biological response landscape in chickens infected by the PL of E. acervulina, contributing significant insights for the investigation of the host-parasite interactions and the management of parasitic diseases.

Mycotoxins and coccidiosis in poultry - co-occurrence, interaction, and effects

Avian coccidiosis, a common disease caused by Eimeria species, results in significant losses in global poultry production. Mycotoxins are low-molecular-weight natural products (i.e., small molecules) produced as secondary metabolites by filamentous fungi and they have the potential to economically and significantly affect global poultry production. Little is known about the relationship between mycotoxins and avian coccidiosis, although they often co-occur in the field. This comprehensive review examines the intricate relationship between mycotoxins and avian coccidiosis, in particular how mycotoxins, including aflatoxins, ochratoxins, trichothecenes as well as Fusarium mycotoxins, compromise the health of the poultry flock and open the door to Eimeria parasites in the gut. In addition, this review sheds light on the immunosuppressive effects of mycotoxins, their disruption of cellular signaling pathways, and the consequent exacerbation of coccidiosis infections. The mechanisms of mycotoxin toxicity are also reviewed, emphasizing direct damage to intestinal epithelial cells, impaired nutrient absorption, inflammation, oxidative stress, and changes in the gut microbiota. Finally, the consequences for the prevention and treatment of coccidiosis when mycotoxins are present in the feed are discussed. This review emphasizes the need for effective management strategies to mitigate the combined risks of mycotoxins and coccidiosis and highlights the complexity of diagnosing and controlling these interrelated problems in poultry. The review advocates a holistic approach that includes strict feed management, disease prevention measures and regular monitoring to maintain the health and productivity of poultry against these significant challenges.

Aflatoxin B1 as a complicit in intestinal damage caused by Eimeria ovinoidalis in lambs: Novel insights to reveal parasite-gut battle

Mycotoxins, unavoidable contaminants in feed and feed ingredients, have the potential to influence the incidence and severity of various diseases upon ingestion. Sheep coccidiosis is an enteric disease caused by protozoa of Eimeria spp. However, the extent to which the presence of aflatoxin b1 (AFB1) synergistically exacerbates damage to intestinal health in lambs with Eimeria remains unclear. 50-day-old female lambs were randomly assigned to a 2 × 2 factorial arrangement of treatments for 15 days to assess the impact of AFB1 exposure on lambs with or without Eimeria (E.) ovinoidalis infection. Our findings reveal that AFB1 synergistically intensifies damage to intestinal health in lambs challenged by E. ovinoidalis. This is evidenced by disruptions to the intestinal microbiota and reductions in the production of short-chain fatty acids. AFB1 further aggravates damage to the cecal mechanical barrier. Additionally, AFB1 contributes to the entry of lipopolysaccharide into the bloodstream, activating the inflammatory response. Interestingly, AFB1 exposure history results in an early peak of oocyst excretion and a decreased number of oocyst excretion in E. ovinoidalis infected lambs. This may be closely linked to the destruction of the intestinal epithelial cell structure and its apoptosis, as indicated by a decreased ratio of Bcl-2 to Bax and increased caspase-3 levels. Mechanistically, proteomics analysis identified mitochondrial dysfunction (inhibition of the oxidative phosphorylation pathway) as the primary factor intensifying intestinal epithelial cell destruction caused by coccidia, exacerbated by AFB1 through the inhibiting the conversion of NADH to NAD+ in the cecum of lambs via down-regulation of the PGC-1α/NRF1/TFAM pathway. Overall, these results offer novel insights into the AFB1 complicity in accelerating intestinal damage caused by E. ovinoidalis in lambs. Targeting the mitochondrial oxidative phosphorylation pathway of the intestine may represent a new therapeutic strategy against the detrimental effects of mycotoxin and coccidia.

Protective efficacy of Eimeria maxima EmLPL and EmTregIM-1 against homologous challenge in chickens

Chicken coccidiosis has inflicted significant economic losses upon the poultry industry. The primary strategies for preventing and controlling chicken coccidiosis include anticoccidial drugs and vaccination. However, these approaches face limitations, such as drug residues and resistance associated with anticoccidial drugs, and safety concerns related to live vaccines. Consequently, the urgent development of innovative vaccines, such as subunit vaccines, is imperative. In previous study, we screened 2 candidate antigens: Eimeria maxima lysophospholipase (EmLPL) and E. maxima regulatory T cell inducing molecule 1 (EmTregIM-1). To investigate the immune protective effect of the 2 candidate antigens against Eimeria maxima (E. maxima) infection, we constructed recombinant plasmids, namely pET-28a-EmLPL and pET-28a-EmTregIM-1, proceeded to induce the expression of recombinant proteins of EmLPL (rEmLPL) and EmTregIM-1 (rEmTregIM-1). The immunogenic properties of these proteins were confirmed through western blot analysis. Targeting EmLPL and EmTregIM-1, we developed subunit vaccines and encapsulated them in PLGA nanoparticles, resulting in nano-vaccines: PLGA-rEmLPL and PLGA-rEmTregIM-1. The efficacy of these vaccines was assessed through animal protection experiments. The results demonstrated that rEmLPL and rEmTregIM-1 were successfully recognized by anti-E. maxima chicken sera and His-conjugated mouse monoclonal antibodies. Immunization with both subunit and nano-vaccines containing EmLPL and EmTregIM-1 markedly mitigated weight loss and reduced oocyst shedding in chickens infected with E. maxima. Furthermore, the anticoccidial indexes (ACI) for both rEmLPL and PLGA-rEmLPL exceeded 160, whereas those for rEmTregIM-1 and PLGA-rEmTregIM-1 were above 120 but did not reach 160, indicating superior protective efficacy of the rEmLPL and PLGA-rEmLPL formulations. By contrast, the protection afforded by rEmTregIM-1 and PLGA-rEmTregIM-1 was comparatively lower. Thus, EmLPL is identified as a promising candidate antigen for vaccine development against E. maxima infection.

Comprehensive analysis of differentially expressed mRNA profiles in chicken jejunum and cecum following Eimeria maxima infection

Coccidiosis, a protozoan disease that substantially impacts poultry production, is characterized by an intracellular parasite. The study utilized 48 one-day-old Horro chickens, randomly divided into the infected (I) and control (C) groups. The challenge group of chickens were administered Eimeria maxima oocysts via oral gavage at 21-days-old, and each chicken received 2 mL containing 7×104 sporulated oocysts. The total RNAs of chicken jejunum and cecum tissues were isolated from three samples, each from I and C groups. Our study aimed to understand the host immune-parasite interactions and compare immune response mRNA profiles in chicken jejunum and cecum tissues at 4 and 7 days postinfection with Eimeria maxima. The results showed that 823 up- and 737 down-regulated differentially expressed mRNAs (DEmRNAs) in jejunum at 4 d infection and control (J4I vs. J4C), and 710 up- and 368 down-regulated DEmRNAs in jejunum at 7 days infection and control (J7I vs. J7C) were identified. In addition, DEmRNAs in cecum tissue, 1424 up- and 1930 down-regulated genes in cecum at 4 days infection and control (C4I vs. C4C), and 77 up- and 191 down-regulated genes in cecum at 7 days infection and control (C7I vs. C7C) were detected. The crucial DEmRNAs, including SLC7A5, IL1R2, GLDC, ITGB6, ADAMTS4, IL1RAP, TNFRSF11B, IMPG2, WNT9A, and FOXF1, played pivotal roles in the immune response during Eimeria maxima infection of chicken jejunum. In addition, the potential detection of FSTL3, RBP7, CCL20, DPP4, PRKG2, TFPI2, and CDKN1A in the cecum during the host immune response against Eimeria maxima infection is particularly noteworthy. Furthermore, our functional enrichment analysis revealed the primary involvement of DEmRNAs in small molecule metabolic process, immune response function, inflammatory response, and toll-like receptor 10 signaling pathway in the jejunum at 4 and 7 days postinfection. Similarly, in the cecum, DEmRNAs at 4 and 7 days postinfection were enriched in processes related to oxidative stress response and immune responses. Our findings provide new insights and contribute significantly to the field of poultry production and parasitology.

Effects of in ovo injection of bacterial peptides and CpG-ODN on Salmonella enterica serovar Heidelberg infection in specific pathogen-free (SPF) chicks

RESEARCH HIGHLIGHTS

Peptides + CpG-ODN reduced SH in caeca at the first week post-infection.Administered formulations did not reduce SH-faecal excretion.Levels of intestinal IgA were similar between all groups.CpG-ODN improved some parameters associated with chick intestinal health.

Supplementing low protein diets with methionine or threonine during mixed Eimeria challenge

We investigated the effects of supplementing low protein diets with methionine (Met) or threonine (Thr) during a mixed Eimeria (consisting of E. acervulina, E. maxima and E. tenella) challenge in broilers. All birds were fed the same starter diet (d1-9) and finisher diet (d28-35) which met Cobb 500 nutrient specifications. Birds were allocated to 1 of 4 dietary treatments from d9 to 28: a standard protein diet (19% CP); a low protein diet (16% CP); or the low protein diet supplemented with Met or Thr at 50% above recommendations. On d14, half of the birds were challenged, and half of the birds were unchallenged. From d14 to 28, feed intake was recorded daily and BW every 3 or 4 d. Oocyst excretion was measured daily from d18 to 27. On d21 and 28, 3 birds per pen were euthanized to assess nutrient digestibility, cytokine expression and intestinal histology. During the acute stage of the challenge, challenged birds reduced ADFI and ADG (P < 0.05). In the pre-patent and recovery stages, birds given the 16% CP diets increased ADFI (P < 0.05), meanwhile there were no differences in ADG in these stages (P > 0.05). Nutrient digestibility was reduced in challenged birds in the acute stage (P < 0.05) but tended to be greater than in unchallenged birds during the recovery stage. There was no significant effect of diet on oocyst excretion or intestinal histology (P > 0.05). Interactions were observed between diet and challenge on IL-10 and IL-21 expression in the cecal tonsils during the acute stage of the challenge (P < 0.05), due to reduced IL-10 expression in challenged Thr birds and greater IL-21 expression in challenged Met birds. Supplementation with Thr or Met had limited effects on the outcomes of a mixed Eimeria challenge but provides benefits to the host by enhancing their immune response.

Correlation of caecal microbiome endotoxins genes and intestinal immune cells in Eimeria tenella infection based on bioinformatics

Introduction

The infection with Eimeria tenella (ET) can elicit expression of various intestinal immune cells, incite inflammation, disrupt intestinal homeostasis, and facilitate co-infection with diverse bacteria. However, the reciprocal interaction between intestinal immune cells and intestinal flora in the progression of ET-infection remains unclear.

Objective

The aim of this study was to investigate the correlation between cecal microbial endotoxin (CME)-related genes and intestinal immunity in ET-infection, with subsequent identification of hub potential biomarker and immunotherapy target.

Methods

Differential expression genes (DEGs) within ET-infection and hub genes related to CME were identified through GSE39602 dataset based on bioinformatic methods and Protein-protein interaction (PPI) network analysis. Moreover, immune infiltration was analyzed by CIBERSORT method. Subsequently, comprehensive functional enrichment analyses employing Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis along with Gene Ontology (GO), gene set enrichment analysis (GSEA), and gene set variation analysis (GSVA) were performed.

Results

A total of 1089 DEGs and 25 hub genes were identified and CXCR4 was ultimately identified as a essential CME related potential biomarker and immunotherapy target in the ET-infection. Furthermore, activated natural killer cells, M0 macrophages, M2 macrophages, and T regulatory cells were identified as expressed intestinal immune cells. The functional enrichment analysis revealed that both DEGs and hub genes were significantly enriched in immune-related signaling pathways.

Conclusion

CXCR4 was identified as a pivotal CME-related potential biomarker and immunotherapy target for expression of intestinal immune cells during ET-infection. These findings have significant implications in elucidating the intricate interplay among ET-infection, CME, and intestinal immunity.

Prophylactic and Therapeutic Efficacy of Ultrasonicated Rosmarinus officinalis Ethanolic Extract and its Chitosan-Loaded Nanoparticles Against Eimeria tenella Infected Broiler Chickens

PURPOSE

The in vivo efficacy of ultrasonicated Rosmarinus officinalis ethanolic extract (UROEE) and its chitosan-loaded nanoparticles (UROEE-CsNPs) was investigated as a dietary prophylactic agent and as a therapeutic treatment against Eimeria tenella infected broiler chickens.

METHODS

Chickens were infected with 4 × 104 E. tenella oocysts at 21 days old for primary infection and with 8 × 104 oocysts at 35 days old for secondary infection. Eleven experimental groups were conducted. Dietary addition of 100 mg/kg UROEE and 20 mg/kg for CsNPs as well as UROEE-CsNPs were included for prophylactic groups from day 1 to 42. The same doses were used for therapeutic treatment groups for 5 constitutive days. Oocyst output in feces was counted. Histopathological and immunohistochemical studies were conducted. Gene expression of pro-inflammatory cytokines as IFN-γ, IL-1β and IL-6 as well as anti-inflammatory cytokines as IL-10 and TGF-β4 was analyzed using semi-quantitative reverse transcriptase-PCR.

RESULTS

The results showed an efficacy of UROEE, CsNPs and UROEE-CsNPs in reduction of oocyst excretion and improving the cecal tissue architecture. CD4+ and CD8+ T lymphocytes protein expression were reduced. E. tenella infection lead to upregulation of pro-inflammatory cytokines as IFN-γ, IL-1β, IL-6 and anti-inflammatory cytokines as TGF-β4 following primary infection, while their expression was downregulated following secondary infection.

CONCLUSION

The dietary prophylactic additives and therapeutic treatments with UROEE, CsNPs and UROEE-CsNPs could decrease the inflammatory response to E. tenella as indicated by oocyst output reduction, histopathological improvements, CD4+ and CD8+ T cells protein expression reduction as well as reducing mRNA expression levels of the tested cytokines following primary and secondary infections. Consequently, these results will help to develop better-combating strategies for the control and prevention of coccidiosis on poultry farms as a dietary prophylactic agent or as a therapeutic treatment.

IFN-γ inhibitory molecules derived from Eimeria maxima inhibit IL-12 secretion by modulating MAPK pathways in chicken macrophages

IFN-γ plays a crucial role in resisting intracellular parasitic protozoa, such as Eimeria species. In our previous study, we identified 4 molecules derived from Eimeria maxima (E. maxima) that significantly inhibited IFN-γ production. However, the mechanism underlying this inhibitory effect remains unknown. In this study, we first investigated the effects of these 4 IFN-γ inhibitory molecules on the expression levels of chicken Toll-like receptors (chTLRs), IL-12, IL-10, TGF-β, and TNF-α in chicken macrophage HD11 and bone marrow-derived dendritic cells (BMDCs). The results demonstrated that these 4 inhibitory molecules significantly downregulated the mRNA levels of chTLR-2, chTLR-4, chTLR-21, and both mRNA and protein levels of IL-12. Subsequently, to clarify the effects of these 4 inhibitory molecules on the IL-12 secretion-related signaling pathways in chicken macrophages, qRT-PCR and Western blot were used to detect the changes of key molecules involved in the signaling pathways of IL-12 secretion (NF-κB, ERK1/2, p38, JNK, STAT3) following coincubation with these inhibitory molecules. Finally, RNAi was employed to verify the function of key molecules in the signaling pathway. The results revealed a significant upregulation in the expression of ERK1/2 phosphorylated protein induced by the 4 inhibitory molecules. Knockdown of the ERK1/2 gene significantly reduced the inhibitory effect of the 4 E. maxima inhibitory molecules on IL-12. These findings indicate that the 4 inhibitory molecules can inhibit the secretion of IL-12 by upregulating the expression of ERK1/2 phosphorylated protein, which is a key molecule in the ERK-MAPK pathway. Our study may contribute to elucidating the mechanisms underlying immune evasion during E. maxima infections, thereby providing new insights for the control of chicken coccidiosis.

A microbial muramidase improves growth performance and reduces inflammatory cell infiltration in the intestine of broilers chickens under Eimeria and Clostridium perfringens challenge

The objective of the present studies was to evaluate muramidase (MUR) supplementation in broilers under Eimeria and/or Clostridium perfringens challenge. For this, 2 experiments were conducted. Experiment 1. A total of 256 one-day old male Cobb 500 chicks were placed in battery cages in a completely randomized design, with 5 treatment groups, 7 replicate cages per treatment and 8 birds per cage. The treatments were: nonchallenged control (NC), challenged control (CC), CC + MUR at 25,000 or 35,000 LSU(F)/kg, and CC + Enramycin at 10 ppm (positive control-PC). Challenge consisted of 15× the recommended dose of coccidiosis vaccine at placement, and Clostridium perfringens (108 CFU/bird) inoculation at 10, 11, and 12 d. Macro and microscopic evaluation, immunohistochemistry, and gene expression were evaluated at 7, 14, 21, and 28 d of age. Experiment 2. A total of 1,120 one-day old male Cobb 500 chicks were placed in floor pens with fresh litter in a completely randomized design, with 4 treatment groups, 8 replicate pens per treatment, and 35 birds per pen. The treatments were: Control, supplementation of MUR at 25,000 or 45,000 LSU(F)/kg, and a positive control (basal diet plus Enramycin). At 10, 11, and 12 d of the experiment all the birds were inoculated by oral gavage with a fresh broth culture of a field isolate Clostridium perfringens (0.5 mL containing 106 CFU/bird). It was observed that in Experiment 1 MUR supplementation reduced the infiltration of macrophages and CD8+ lymphocytes in the liver and ileum of infected birds, downregulated IL-8 and upregulated IL-10 expression. In Experiment 2, MUR linearly improved the growth performance of the birds, increased breast meat yield, and improved absorption capacity. MUR supplementation elicited an anti-inflammatory response in birds undergoing a NE challenge model that may explain the improved growth performance of supplemented birds.

Coinfection of the gut with protozoal and metazoal parasites in broiler and laying chickens

The chicken business faces substantial economic losses due to the risk of parasitic coinfection. Because the current study aimed to investigate enteric parasitic coinfections problems among the suspected examined chicken farms, samples were collected during the field investigation from suspected freshly dead birds, clinically diseased, apparently healthy, and litter samples for further laboratory parasitological, histopathological, and immunological examinations. Variable mortalities with various clinical indicators, such as ruffled feathers, weight loss, diarrhea of various colors, and a decline in egg production, occurred on the farms under investigation. In addition, the treatment protocols of each of the farms that were evaluated were documented and the m-RNA levels of some cytokines and apoptotic genes among the infected poultry have been assessed. The prevalence rate of parasitic coinfection in the current study was found to be 8/120 (6.66%). Parasitological analysis of the samples revealed that they belonged to distinct species of Eimeria, cestodes, and Ascaridia galli. When deposited, A. galli eggs were nonembryonated and ellipsoidal, but cestodes eggs possessed a thin, translucent membrane that was subspherical. Eimeria spp. oocysts in layer chickens were identified as Eimeria acervulina and Eimeria maxima in broiler chickens. Our findings proved that coinfection significantly upregulated the IL-1β, BAX, and Cas-3 genes. Conversely, the IL-10, BCL-2, and AKT mRNA levels were downregulated, indicating that nematode triggered apoptosis. The existence of parasite coinfection was verified by histological investigation of the various intestinal segments obtained from affected flocks. A. galli and cestodes obstructed the intestinal lumen, causing different histological alternations in the intestinal mucosa. Additionally, the lamina propria revealed different developmental stages of Eimeria spp. It was determined that parasite coinfection poses a significant risk to the poultry industry. It was recommended that stringent sanitary measures management methods, together with appropriate treatment and preventative procedures, be employed in order to resolve such issues.

Vaccination Against Poultry Parasites

The complexity of parasites and their life cycles makes vaccination against parasitic diseases challenging. This review highlights this by discussing vaccination against four relevant parasites of poultry. Coccidia, i.e., Eimeria spp., are the most important parasites in poultry production, causing multiple billions of dollars of damage worldwide. Due to the trend of antibiotic-free broiler production, use of anticoccidia vaccines in broilers is becoming much more important. As of now, only live vaccines are on the market, almost all of which must be produced in birds. In addition, these live vaccines require extra care in the management of flocks to provide adequate protection and prevent the vaccines from causing damage. Considerable efforts to develop recombinant vaccines and related work to understand the immune response against coccidia have not yet resulted in an alternative. Leucozytozoon caulleryi is a blood parasite that is prevalent in East and South Asia. It is the only poultry parasite for which a recombinant vaccine has been developed and brought to market. Histomonas meleagridis causes typhlohepatitis in chickens and turkeys. The systemic immune response after intramuscular vaccination with inactivated parasites is not protective. The parasite can be grown and attenuated in vitro, but only together with bacteria. This and the necessary intracloacal application make the use of live vaccines difficult. So far, there have been no attempts to develop a recombinant vaccine against H. meleagridis. Inactivated vaccines inducing antibodies against the poultry red mite Dermanyssus gallinae have the potential to control infestations with this parasite. Potential antigens for recombinant vaccines have been identified, but the use of whole-mite extracts yields superior results. In conclusion, while every parasite is unique, development of vaccines against them shares common problems, namely the difficulties of propagating them in vitro and the identification of protective antigens that might be used in recombinant vaccines.

Effect of an Alliaceae Encapsulated Extract on Growth Performance, Gut Health, and Intestinal Microbiota in Broiler Chickens Challenged with Eimeria spp

This study analyzed the effects of an Alliaceae encapsulated extract (AE-e) on daily gain (ADG), feed intake (ADFI), feed conversion ratio (FCR), oocysts per gram of feces (OPG), intestinal lesion (LS), and microbiota composition in broilers challenged with Eimeria spp. A total of 4800 one day Cobb-500 were allotted into 10 treatment groups with 12 replicates of 40 birds in a 2 × 4 + 2 factorial arrangement. The first factor was non-challenged (NC) or challenged (C), the second was four levels of AE-e added in the basal diet, 0 (AE0), 250 (AE250), 500 (AE500), and 750 mg·kg-1 (AE750), plus two ionophore controls, non-challenged (NC-Ion) and challenged (C-Ion). No interactions were observed between factors (NC0, NC250, NC500, NC750, C0, C250, C500, and C750), while C-Ion improved FCR at 21 d. The challenge affected negatively ADG and FCR and promoted enteropathogens in cecum. AE750 improved FCR in the finisher and cumulative phases, while C-Ion had fewer total OPG than C0 and C250. Likewise, at 21d, C250, C500, and C-Ion had fewer LS than C0, while at 28 d, C750 showed lower than C-Ion. In the cecum microbiota, C500 had more Ruminococcus, Firmicutes b, and Intestinimonas than C-Ion. In summary, AE-e showed beneficial results in broilers infected with Eimeria spp.

Microbiota promotes recruitment and pro-inflammatory response of caecal macrophages during E. tenella infection

BACKGROUND

Eimeria genus belongs to the apicomplexan parasite phylum and is responsible for coccidiosis, an intestinal disease with a major economic impact on poultry production. Eimeria tenella is one of the most virulent species in chickens. In a previous study, we showed a negative impact of caecal microbiota on the physiopathology of this infection. However, the mechanism by which microbiota leads to the physiopathology remained undetermined. Macrophages play a key role in inflammatory processes and their interaction with the microbiota during E. tenella infection have never been investigated. We therefore examined the impact of microbiota on macrophages during E. tenella infection. Macrophages were monitored in caecal tissues by immunofluorescence staining with KUL01 antibody in non-infected and infected germ-free and conventional chickens. Caecal cells were isolated, stained, analyzed and sorted to examine their gene expression using high-throughput qPCR.

RESULTS

We demonstrated that microbiota was essential for caecal macrophage recruitment in E. tenella infection. Furthermore, microbiota promoted a pro-inflammatory transcriptomic profile of macrophages characterized by increased gene expression of NOS2, ACOD1, PTGS2, TNFα, IL1β, IL6, IL8L1, IL8L2 and CCL20 in infected chickens. Administration of caecal microbiota from conventional chickens to germ-free infected chickens partially restored macrophage recruitment and response.

CONCLUSIONS

Taken together, these results suggest that the microbiota enhances the physiopathology of this infection through macrophage recruitment and activation. Consequently, strategies involving modulation of the gut microbiota may lead to attenuation of the macrophage-mediated inflammatory response, thereby limiting the negative clinical outcome of the disease.

Protective efficacy of multiepitope vaccines constructed from common antigens of Eimeria species in chickens

Clinical avian coccidiosis is typically caused by coinfection with several Eimeria species. Recombinant protein and DNA vaccines have shown promise in controlling coccidiosis. On this basis, DNA vaccines that encode multiple epitopes from different Eimeria species may provide broad protection against coinfections. In this study, we designed a fusion gene fragment, 14EGT, that contained concentrated T-cell epitopes from four common antigens of Eimeria species (14-3-3, elongation factor 2, glyceraldehyde-3-phosphate dehydrogenase, and transhydrogenase). The multiepitope DNA vaccine pVAX1-14EGT and recombinant protein vaccine pET-32a-14EGT (r14EGT) were then created based on the 14EGT fragment. Subsequently, cellular and humoral immune responses were measured in vaccinated chickens. Vaccination-challenge trials were also conducted, where the birds were vaccinated with the 14EGT preparations and later exposed to single or multiple Eimeria species to evaluate the protective efficacy of the vaccines. According to the results, vaccination with 14EGT preparations effectively increased the proportions of CD4+ and CD8+ T cells and the levels of Th1 and Th2 hallmark cytokines. The levels of serum IgG antibodies were also significantly increased. Animal vaccination trials revealed alleviated enteric lesions, weight loss, and oocyst output compared to those of the control groups. The preparations were found to be moderately effective against single Eimeria species, with the anticoccidial index (ACI) ranging from 160 to 180. However, after challenge with multiple Eimeria species, the protection provided by the 14EGT preparations was not satisfactory, with ACI values of 142.18 and 146.41. Collectively, the results suggest that a multiepitope vaccine that encodes the T-cell epitopes of common antigens derived from Eimeria parasites could be a potential and effective strategy to control avian coccidiosis.

Probiotic Enterococcus faecalis surface-delivering key domain of EtMIC3 proteins: immunoprotective efficacies against Eimeria tenella infection in chickens

IMPORTANCE

Avian coccidiosis caused by Eimeria brings huge economic losses to the poultry industry. Although live vaccines and anti-coccidial drugs were used for a long time, Eimeria infection in chicken farms all over the world commonly occurred. The exploration of novel, effective vaccines has become a research hotspot. Eimeria parasites have complex life cycles, and effective antigens are particularly critical to developing anti-coccidial vaccines. Microneme proteins (MICs), secreted from microneme organelles located at the parasite apex, are considered immunodominant antigens. Eimeria tenella microneme 3 (EtMIC3) contains four conserved repeats (MARc1, MARc2, MARc3, and MARc4) and three divergent repeats (MARa, MARb, and MARd), which play a vital role during the Eimeria invasion. Enterococcus faecalis is a native probiotic in animal intestines and can regulate intestinal flora. In this study, BC1 and C4D domains of EtMIC3, BC1 or C4D fusing to dendritic cells targeting peptides, were surface-displyed by E. faecalis, respectively. Oral immunizations were performed to investigate immune protective effects against Eimeria infection.

Inhibitory effect of Eimeria maxima IFN-γ inhibitory molecules on the immune function of T cell subsets in chickens

It has been reported that infection of chicken coccidian could inhibit the production of Th1 cytokine IFN-γ, thereby evading clearance by the host immune system. The present study aimed to have a further investigation into the effects of Eimeria maxima IFN-γ inhibitory molecules (EmHPSP-2 and EmHPSP-3) on the immune function of chicken peripheral blood mononuclear cells (PBMC) and various T cell subsets. First, separated PBMC or sorted T cell subsets were used for incubation with recombinant proteins of EmHPSP-2 (rEmHPSP-2) and EmHPSP-3 (rEmHPSP-3). Subsequently, the effects of rEmHPSP-2 and rEmHPSP-3 on proliferative capacity, nitric oxide (NO) release and mRNA levels of cytokines of the above cells were detected. The sorting purity of CD8+, CD4+ CD25-, CD4+, and CD4+ CD25+ T cells was 93.01, 88.88, 87.04, and 81.26%, respectively. The NO release of PBMC was significantly inhibited by rEmHPSP-2 and rEmHPSP-3. The proliferation of PBMC and CD4+ T cells was significantly inhibited by rEmHPSP-2 and rEmHPSP-3, whereas CD8+, CD4+ CD25-, and CD4+ CD25+ T cells was significantly promoted by the 2 proteins. The 2 proteins significantly downregulated interferon-gamma (IFN-γ) mRNA level, upregulated the transcriptional levels of interleukin-10 (IL-10) and transforming growth factor-beta1 (TGF-β1) in PBMC. IFN-γ and IL-2 transcriptional levels were markedly inhibited in CD8+ T cells. IFN-γ transcriptional level was significantly inhibited, but IL-4 was promoted by rEmHPSP-2 and rEmHPSP-3 in CD4+ CD25- T cells. Meanwhile, the inhibitory effects of rEmHPSP-2 and rEmHPSP-3 on the transcriptional levels of IFN-γ and IL-2 were more obvious in CD4+ T cells containing CD25+ cells compared with the CD25+ cells depletion group. It was found that IL-10, TGF-β1, and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) mRNA levels were significantly upregulated upon stimulation of chicken CD4+ CD25+ T cells by proteins. This study is not only of great significance to clarify the immune evasion mechanism of chicken coccidia, but also provides candidate antigen molecules for development of a novel vaccine against chicken coccidiosis.

Dietary peptide-specific antibodies against interleukin-4 differentially alter systemic immune cell responses during Eimeria challenge with minimal impacts on the cecal microbiota

Eimeria spp. induce host interleukin (IL)-4 production, a potent immune regulator, during coccidiosis to evade immune responses. Dietary anti-IL-4 may preserve bird performance during challenge; however, specific mechanisms have not been investigated. Study objectives were to develop peptide-specific anti-IL-4 antibodies and evaluate immune cell profiles and the cecal microbiota during Eimeria challenge. Four candidate IL-4 peptides were selected based on antigenicity and location. Hens were injected with conjugated peptide or carrier-only control (3/injection), eggs were collected post-vaccination and yolks were pooled by peptide before freeze-drying. On d 0, 300 Ross 708 broilers were placed in floor pens (10/pen) and assigned to 5 diets consisting of basal diet + 2% egg yolk powder containing antibodies against 1 of 4 target peptides or carrier-only control for 14-d starter and grower periods (28 d total). Baseline blood and cecal contents were collected on d 14 (6 birds/diet) before half the remainder were inoculated with 10X Coccivac-B52 (Merck Animal Health, Kenilworth, NJ). Body weight (BW) and feed intake (FI) were recorded weekly and blood and cecal samples were collected at 3, 7, and 14 d post-inoculation (pi; 3/treatment). Immune cell profiles in peripheral blood mononuclear cells (PBMC) were evaluated flow cytometrically and cecal microbial communities determined by 16S/18S rRNA gene amplicon sequencing. Data were log-transformed when necessary and analyzed with diet, Eimeria, and timepoint fixed effects plus associated interactions (SAS 9.4; P ≤ 0.05). Anti-IL-4 did not alter baseline performance but generally increased PBMC Bu-1+ B cells 38.0 to 55.4% (P < 0.0001). Eimeria challenge reduced FI and BWG 16.1 and 30.3%, respectively, regardless of diet (P < 0.0001) with only birds fed peptide 4 antibodies not recovering feed conversion by d 28. Minimal diet-associated cecal microbiota changes were observed, indicating that anti-IL-4 effects were likely host-specific. Eimeria-challenged birds fed peptide 3 antibodies displayed minimal immune cell fluctuations compared to unchallenged counterparts, suggesting these antibodies potentially modulated intestinal immune responses to minimize systemic requirements, making them good candidates for further research.

Protection against Eimeria intestinalis infection in rabbits immunized with the recombinant elongation factors EF1α and EFG

Eimeria intestinalis is the most pathogenic species of rabbit coccidiosis, causing weight loss, diarrhea, and even acute death. The currently used anticoccidial drugs against E. intestinalis in rabbits are associated with drug resistance and residues. Immunological control might be a potential alternative. We cloned and expressed the E. intestinalis recombinant EF1α and EFG (rEi-EF1α and rEi-EFG, respectively). Rabbits were immunized subcutaneously every 14 days with 100 µg of rEi-EF1α and rEi-EFG and followed by 5 × 104 E. intestinalis sporulated oocysts orally challenge. Serum samples were collected every 7 days to measure the levels of specific antibodies and cytokines. On post-challenge day 14, rabbits were sacrificed and the anticoccidial index was evaluated. The rabbits of PBS challenged groups exhibited anorexia, diarrhea, marked intestinal wall thickening, and white nodules that formed patches, while rabbits from the rEi-EF1α or rEi-EFG challenged group exhibited milder symptoms. The rEi-EF1α group showed a 75.18% oocyst reduction and 89.01%wt gain; the rEi-EFG group had a 60.58% oocyst reduction and 56.04%wt gain. After vaccination, specific IgG levels increased and stayed high (P < 0.05). The IL-4 and IL-2 levels of rEi-EF1α immunized groups showed a significant increase after immunization (P < 0.05). Both rEi-EF1α and rEi-EFG could induce humoral and cellular immune responses. In contrast, rabbits immunized with rEi-EF1α were better protected from challenge by E. intestinalis than rEi-EFG.

Impact of a direct-fed microbial supplementation on intestinal permeability and immune response in broiler chickens during a coccidia challenge

Maintaining intestinal health supports optimal gut function and influences overall performance of broilers. Microlife® Prime (MLP) contains a unique combination of four strains of Bacillus spp. selected to support a healthy gut which may improve performance. The aim of this study was to determine the effects of MLP supplementation on intestinal health and immunity of broilers challenged with a mixed coccidia infection during peak [0 to 6-day post-infection (dpi)] and recovery phases (6 to 13 dpi). A total of 120 male, 4 days-old Ross 708, broiler chicks were allotted to 3 treatment groups (8 replicate cages; 5 birds/cage) in a randomized complete block design. Treatments included a non-challenge (NEG), a coccidia challenge (POS), and coccidia challenge fed MLP (5 × 105 CFU/g of diet). Diets were corn-soybean meal-based. At 11 days of age, all birds, except for NEG, were orally gavaged with 15 doses (3 × the recommended commercial dose). On 6, 9, and 13 dpi, birds were orally gavaged with fluorescein isothiocyanate conjugate dextran (FITC-d). Plasma and mid-jejunum tissues were collected 2 h later. On 6 dpi, duodenal lesions from 2 birds/cage were scored and droppings were collected for oocyst enumeration. Body weight gain (BWG) and feed conversion ratio (FCR) were calculated over the experimental period. Data were analyzed with GLIMMIX procedure of SAS. During the peak phase, POS birds had reduced BWG (23%) and FCR (15%) compared to NEG birds (P < 0.05), while birds fed MLP had similar BWG (209 and 208 g) and FCR (1.17 and 1.21) compared to NEG (P > 0.05). On 6 dpi, POS birds had higher lesion scores and oocyst shedding, 2 × increase in serum FITC-d, and higher jejunum IL-10, and IFN-γ mRNA compared to NEG (P < 0.05). Birds fed MLP had reduced plasma FITC-d compared to POS birds (P < 0.05) and similar IL-10 and IFN-γ mRNA. On 13 dpi, birds fed MLP had lower plasma FITC-d, jejunum IL-10 and IFN-γ mRNA compared to POS birds (P < 0.05), but similar IL-10 to NEG birds (P > 0.05). This study confirms MLP improves intestinal health and positively modulates mucosal immune response post-coccidia challenge.

Impacts of Eimeria coinfection on growth performance, intestinal health and immune responses of broiler chickens

Coccidiosis caused by Eimeria is one of the most severe chicken diseases and imposes huge economic losses to the poultry industry globally. Multi-Eimeria species coinfections are common with the most prevalent combination being mixtures of Eimeria acervulina and Eimeria tenella. Although detrimental impacts of either E. acervulina or E. tenella on chicken health are well recognized, no information is available regarding their coinfection effects so far. This study was designed to investigate the influence of coinfection with E. acervulina and E. tenella on broiler chickens. 144 one-day-old broiler chickens within each of trials (trial I or II) were divided into four groups, namely, control group (CG), E. acervulina infection group (EAIG), E. tenella infection group (ETIG) and dual (E. acervulina and E. tenella) infection group (DIG). Then, chickens were measured for weight loss, lesion scores, oocyst outputs, histological changes and expressions of pro-inflammatory (interleukin [IL]-6, IL-8 and IL-18), regulatory (IL-10 and IL-22) cytokines and Toll-like receptors (TLR; TLR2 and TLR4) as well as intestinal barrier (mucin 2 [MUC2] and fattey acid-bingding proteins 2 and 6 [FABP2 and FABP6])- and tight junction (TJ; zonula occluden-1 [ZO-1], occludin [OCLN], and claudins 1 and 5 [CLDN1 and CLDN5])-related proteins at 3, 5, 7, 10, 14 and 21 days post-infection, respectively. Our results consistently showed that although ETIG and DIG exhibited a higher level of weight loss and a more amount of oocyst excretion than EAIG, DIG had lighter lesions than EAIG in the early phase because of coinfection with E. tenella. A higher (P < 0.05) ratio of duodenal villous height to crypt depth was also observed in DIG than EAIG. Moreover, histological changes in the duodenum and cecum varied by single and dual Eimeria infections. Expressions of the intestinal barrier- and TJ-related genes of EAIG, ETIG and DIG were significantly (P < 0.05) upregulated but their levels exhibited differential changes among infected chickens. Similarly, the infected chickens showed significant (P < 0.05) inflammatory responses and higher (P < 0.05) expressions of TLRs in the intestines in comparison to CG. These results presented a comprehensive physiological, pathological and immunological characterization of E. acervulina and E. tenella coinfection in broiler chickens and also shed insights into pathogenesis of multi-coccidia coinfections.

The caecal microbiota promotes the acute inflammatory response and the loss of the intestinal barrier integrity during severe Eimeria tenella infection

Introduction

Coccidiosis, a disease caused by intestinal apicomplexan parasites Eimeria, is a threat to poultry production. Eimeria tenella is one of the most pathogenic species, frequently causing a high prevalence of opportunistic infections.

Objective

The objective of this study is to investigate the role of the microbiota in the pathogenesis of severe Eimeria tenella infection.

Methods

We have previously shown that microbiota can promote parasite development. To study the effect of the microbiota on the pathogenesis of this infection, we used an experimental condition (inoculum of 10 000 oocysts E. tenella INRAE) in which the parasite load is similar between germ-free and conventional broilers at 7 days post-infection (pi). Thirteen conventional and 24 germ-free chickens were infected. Among this latter group, 12 remained germ-free and 12 received a microbiota from conventional healthy chickens at 4 days pi. Caeca and spleens were collected at 7 days pi.

Results

Our results demonstrated caecal lesions and epithelium damage in conventional chickens at 7 days pi but not in germ-free infected chickens. Administration of conventional microbiota to germ-free chickens partially restored these deleterious effects. At day 7 pi, both infected conventional and germ-free chickens exhibited increased gene expression of inflammatory mediators, including IL15, IFNγ, TNFα and the anti-inflammatory mediator SOCS1, whereas the inflammatory mediators CXCLi2, CCL20, IL18, CSF1, NOS2, PTGS2, IL1β, IL6, the receptor CCR2, and the anti-inflammatory mediators TGFβ1 and IL10 were upregulated only in infected conventional chickens. Notably, the IL18, PTGS2 gene expression was significantly higher in the infected conventional group. Overall, the inflammatory response enhanced by the microbiota might be in part responsible for higher lesion scores. Epithelial tight junction protein gene expression analysis revealed a significant upregulation of CLDN1 with the infection and microbiota, indicating a potential loss of the intestinal barrier integrity.

Conclusion

These observations imply that, during E. tenella infection, the caecal microbiota could trigger an acute inflammatory response, resulting in a loss of intestinal integrity. Increase in bacterial translocation can then lead to the likelihood of opportunistic infections. Hence, modulating the microbiota may offer a promising strategy for improving poultry gut health and limiting caecal coccidiosis.

Development of a new immunodiagnostic tool for poultry coccidiosis using an antigen-capture sandwich assay based on monoclonal antibodies detecting an immunodominant antigen of Eimeria

This study was conducted to develop an antigen-capture ELISA that detects an immunodominant antigen of Eimeria, 3-1E which is present in all Eimeria species, using a set of 3-1E-specific mouse monoclonal antibodies (mAbs). Highly sensitive 3-1E-specific antigen-capture ELISA was established using compatible mAb pairs (#318 and #320) selected from 6 mAbs (#312, #317, #318, #319, #320, and #323) with high binding activity against recombinant 3-1E protein. These anti-3-1E mAbs specifically recognized E. tenella sporozoites and a higher level of 3-1E was detected in the lysate of sporozoites than in sporocysts. Immunofluorescence assay (IFA) using 2 mAbs (#318 and #320) showed specific staining around the membrane of E. tenella sporozoites. In order to measure the changes in the 3-1E level during in coccidiosis, serum, feces, jejunal, and cecal contents were individually collected daily for 7-days postinfection (dpi) with E. maxima and E. tenella. The new ELISA was sensitive and specific for 3-1E detection in all samples collected daily from E. maxima- and E. tenella-infected chickens for a week, and the detection sensitivity ranges were 2 to 5 ng/mL and 1 to 5 ng/mL in serum, 4 to 25 ng/mL and 4 to 30 ng/mL in feces, 1 to 3 ng/mL and 1 to 10 ng/mL in cecal contents, and 3 to 65 ng/mL and 4 to 22 ng/mL in jejunal contents. Following coccidiosis, the overall 3-1E levels started to increase from 4 dpi, and the highest production was shown on 5 dpi. Among the samples collected from Eimeria-infected chickens, the highest detection level was found in the jejunal contents of E. maxima-infected chickens. Furthermore, the level of IFN-γ in serum was significantly (P < 0.05) increased from 3 dpi and peaked on 5 dpi post E. maxima infection. Post E. tenella infection, the level of IFN-γ in serum gradually (P < 0.05) increased from 2 to 5 dpi and plateaued at 7 dpi. The level of TNF-α in serum was rapidly (P < 0.05) increased from 4 dpi and those levels were kept until 7 dpi post both Eimeria infections (E. maxima and E. tenella). More importantly, the daily changes in the 3-1E levels in different samples from E. maxima- and E. tenella-infected chickens were effectively monitored with this new antigen-capture ELISA. Therefore, this new immunoassay is a sensitive diagnostic tool to monitor coccidiosis in a large field population in the commercial poultry farms before clinical symptoms develop using serum, feces, and gut samples during the entire period of infection cycle starting from 1 d after infection.

Adapted tissue assay for the assessment of ileal granulocyte degranulation following in ovo inoculation with select bacteria or coccidial challenge in chickens

A previously described heterophil degranulation assay was adapted for use with ileal mucosal tissue via quantification of β-D-glucuronidase and assay end product 4-methylumbelliferone (4-MU). Three initial experiments evaluated the effect of in ovo inoculations of Citrobacter freundii (CF) or mixed lactic acid bacteria (LAB) on ileal granulocyte degranulation. Inoculations were administered on embryonic d18, body weights (BW) were recorded on day of hatch (DOH) and d10 to calculate body weight gain (BWG), and ileal mucosal scrapings were collected on DOH or d10 for the 4-MU assay. In all experiments, treatments were statistically analyzed relative to control groups. Treatments minimally affected BWG in all in ovo experiments (p > 0.05) relative to respective control groups. Similarly, ileal degranulation in in ovo treatments did not statistically differ (p > 0.05). Based on BWG, in ovo treatments may have induced low-level inflammation unable to elicit detectable changes via the 4-MU assay. Four subsequent experiments were conducted to evaluate effects of Eimeria maxima (EM) on ileal degranulation. Treatments included non-inoculated controls and low, medium, or high EM infection. Across all four experiments, final BW or BWG over the inoculation period were suppressed (p < 0.05) in EM groups relative to respective controls with the exception of EM-low (p = 0.094) and EM-medium (p = 0.096) in one trial. Ileal mucosal scrapings for the 4-MU assay were collected on day of peak lesions. Resulting values were reduced (p < 0.05) for EM treated birds in three experiments with the exception of EM-medium (p = 0.247). No differences were observed in one experiment (p = 0.351), which may have been attributed to a variation in strain of infecting Eimeria. Although refinement for low level inflammation is warranted, results indicate successful adaptation of the 4-MU assay for use with intestinal tissue during significant gastrointestinal inflammation.

Protective efficacy of recombinant proteins AMA1 and IMP1 in rabbits infected with Eimeria intestinalis

Eimeria intestinalis is one of the most pathogenic rabbit coccidia species causing severe intestinal damage and increased risk of secondary infection from opportunistic pathogens, which results in huge economic losses to the rabbit industry. Anticoccidial drugs are currently the main method to control coccidiosis; however, increasing resistance and drug residues have fueled research on anticoccidial vaccines. Apical membrane antigen 1 (AMA1) and immune mapped protein 1 (IMP1), as surface proteins, are associated with host invasion and might have the potential as candidate vaccine antigens. In the present study, recombinant IMP1 (rEiIMP1) and AMA1 (rEiAMA1) from E. intestinalis were expressed using Escherichia coli BL21. The immunoreactivity and immunoprotective effects of rEiIMP1 and rEiAMA1 were then analyzed. Fifty rabbits were grouped randomly (n = 10 per group): The unimmunized-unchallenged control group (sterilized phosphate-buffered saline (PBS)), the unimmunized-challenged control group (sterilized PBS), the vector protein-challenged control group (100 μg of pET-32a vector protein per rabbit), the rEiIMP1 immunized group (100 μg of rEiIMP1 per rabbit), and the rEiAMA1 immunized group (100 μg of rEiAMA1 per rabbit). After two immunizations, the rabbits were challenged with homologous oocysts (except for the unimmunized-unchallenged group). Serum specific antibody levels were assessed weekly throughout the experimental period; and the levels of different cytokines in the serum before the challenge were detected. The clinical symptoms, oocysts output, weight gain, feed conversion ratio (FCR), and lesion scores were recorded after experimental infection, and the anticoccidial indexes (ACIs) were calculated. The results showed that both rEiIMP1 and rEiAMA1 had good immunoreactivity. Rabbits immunized with rEiIMP1 and rEiAMA1 displayed 66.74 % and 63.14 % oocyst reduction, respective land 81.79 % and 78.87 % body weight gain, respectively. The rEiIMP1 and rEiAMA1 groups had lower FCRs (3.77:1 and 4.06:1, respectively) and lesion scores (P = 0.00). The rEiIMP1 and rEiAMA1 showed moderate effects, with an ACI of 152.09 and 147.17, respectively. Immunization induced high levels of anti-rEiIMP1 and -rEiAMA1 antibodies. Rabbits immunized with rEiIMP1 and rEiAMA1 displayed significantly increased interleukin (IL)- 2 (P = 0.00), interferon gamma (IFN)- γ (P = 0.00), and IL- 4 (P = 0.00) levels. Therefore, this study provided potential candidate vaccine antigens for E. intestinalis.

Effects of Different Eimeria Inoculation Doses on Growth Performance, Daily Feed Intake, Gut Health, Gut Microbiota, Foot Pad Dermatitis, and Eimeria Gene Expression in Broilers Raised in Floor Pens for 35 Days

The study was conducted to investigate the effects of different Eimeria inoculation doses on the growth performance, gut ecosystem, and body composition of broilers in floor pens for 35 days. A total of 750 15-day-old broilers were allocated to five experimental groups with six replicate pens. The five experimental groups included unchallenged control (CON); Eimeria dose 1 (ED1): E. acervulina: 31,250/E. maxima: 6250/E. tenella: 6250; Eimeria dose 2 (ED2): E. acervulina: 62,500/E. maxima: 12,500/E. tenella: 12,500; Eimeria dose 3 (ED3): E. acervulina: 125,000/E. maxima: 25,000/E. tenella: 25,000; and Eimeria dose 4 (ED4): E. acervulina: 250,000/E. maxima: 50,000/E. tenella: 50,000. On D 21, BW were linearly reduced by increased Eimeria inoculation doses (p < 0.01). On D 35, the Eimeria challenge groups had significantly lower BW compared to the CON group. Increased Eimeria inoculation doses linearly decreased crude fat (CF) (p < 0.01) on D 21. Increased Eimeria inoculation doses tended to increase the relative abundance of the phylum Proteobacteria (p = 0.098) on D 21. On D 35, lean:fat was linearly reduced by increased Eimeria inoculation doses (p < 0.05). Eimeria infection negatively influenced growth performance and gut health in broilers in the acute phase, and the negative effects were prolonged to D 35 in floor pen conditions.

Osteoimmunology: A Link between Gastrointestinal Diseases and Skeletal Health in Chickens

Bone serves as a multifunctional organ in avian species, giving structural integrity to the body, aiding locomotion and flight, regulating mineral homeostasis, and supplementing calcium for eggshell formation. Furthermore, immune cells originate and reside in the bone marrow, sharing a milieu with bone cells, indicating a potential interaction in functions. In avian species, the prevalence of gastrointestinal diseases can alter the growth and the immune response, which costs a great fortune to the poultry industry. Previous studies have shown that coccidiosis and necrotic enteritis can dramatically reduce bone quality as well. However, possible mechanisms on how bone quality is influenced by these disease conditions have not yet been completely understood, other than the reduced feed intake. On the other hand, several mediators of the immune response, such as chemokines and cytokines, play a vital role in the differentiation and activation of osteoclasts responsible for bone resorption and osteoblasts for bone formation. In the case of Eimeria spp./Clostridium perfringens coinfection, these mediators are upregulated. One possible mechanism for accelerated bone loss after gastrointestinal illnesses might be immune-mediated osteoclastogenesis via cytokines-RANKL-mediated pathways. This review article thus focuses on osteoimmunological pathways and the interaction between host immune responses and bone biology in gastrointestinal diseases like coccidiosis and necrotic enteritis affecting skeletal health.

The role of genetics in determining resistance to coccidiosis in goats a review of current research and future directions

Coccidiosis is a significant parasitic disease in goats, with significant impacts on animal health, productivity, and economic losses for producers. Although various management practices can help control and prevent coccidiosis, a growing body of research suggests that genetics play an important role in determining resistance to the disease. This review explores the current understanding of the genetics of coccidiosis resistance in goats, including the potential genetic factors and mechanisms involved, and the implications for breeding and selection programs. The review will also discuss current research and future directions in this field, including the use of genomic tools and technologies to better understand the genetics of resistance and to improve breeding programs for coccidiosis resistance in goats. This review will be of interest to veterinary practitioners, goat producers, animal breeders, and researchers working in the field of veterinary parasitology and animal genetics.

Effect of Dietary Chlorella vulgaris or Tetradesmus obliquus on Laying Performance and Intestinal Immune Cell Parameters

A feeding trial was conducted to investigate the effect of dietary supplementation of Chlorella vulgaris (CV) or Tetradesmus obliquus (TO) on laying performance, egg quality, and gut health indicators of laying hens. A total of 144 Hy-Line Brown laying hens aged 21 weeks were randomly assigned to one of three dietary treatments with eight replicates of six hens. Dietary treatments were as follows: CON, basal diet; CV, basal diet + 5 g C. vulgaris/kg of diet; TO, basal diet + 5 g T. obliquus/kg of diet. The results showed that diets supplemented with CV or TO had insignificant effects on laying performance, egg quality (i.e., Haugh unit and eggshell strength and thickness), jejunal histology, cecal short-chain fatty acids, and antioxidant/immune markers in ileal mucosa samples of laying hens. Compared with the control group, the egg yolk color score was higher (p < 0.05) in laying hens fed on diets containing CV and TO, although the former was a more intense yellow than the latter. Small intestinal lamina propria cells were isolated using flow cytometry to examine the percentages of immune cell subpopulations. Dietary microalgae did not affect B cells or monocytes/macrophages but altered the percentage of CD4+ T cells and CD8- TCR γδ T cells. Collectively, diets supplemented with C. vulgaris or T. obliquus can improve egg yolk color and would modulate host immune development and competence in laying hens.

Botanicals: A promising approach for controlling cecal coccidiosis in poultry

Avian species have long struggled with the problem of coccidiosis, a disease that affects various parts of the intestine, including the anterior gut, midgut, and hindgut. Among different types of coccidiosis, cecal coccidiosis is particularly dangerous to avian species. Chickens and turkeys are commercial flocks; thus, their parasites have remained critical due to their economic importance. High rates of mortality and morbidity are observed in both chickens and turkeys due to cecal coccidiosis. Coccidiostats and coccidiocidal chemicals have traditionally been added to feed and water to control coccidiosis. However, after the EU banned their use because of issues of resistance and public health, alternative methods are being explored. Vaccines are also being used, but their efficacy and cost-effectiveness remain as challenges. Researchers are attempting to find alternatives, and among the alternatives, botanicals are a promising choice. Botanicals contain multiple active compounds such as phenolics, saponins, terpenes, sulfur compounds, etc., which can kill sporozoites and oocysts and stop the replication of Eimeria. These botanicals are primarily used as anticoccidials due to their antioxidant and immunomodulatory activities. Because of the medicinal properties of botanicals, some commercial products have also been developed. However, further research is needed to confirm their pharmacological effects, mechanisms of action, and methods of concentrated preparation. In this review, an attempt has been made to summarize the plants that have the potential to act as anticoccidials and to explain the mode of action of different compounds found within them.

Bacillus subtilis Expressing Chicken NK-2 Peptide Enhances the Efficacy of EF-1α Vaccination in Eimeria maxima-Challenged Broiler Chickens

This study was conducted to investigate the synergistic effects of orally delivered B. subtilis-cNK-2 on vaccination with rEF-1α against E. maxima infection in broiler chickens. Chickens were assigned into the following five groups: control (CON, no Eimeria infection), non-immunized control (NC, PBS), component 1 (COM1, rEF-1α only), component 2 (COM2, rEF-1α plus B. subtilis empty vector), and component 3 (COM3, rEF-1α plus B. subtilis-NK-2). The first immunization was administered intramuscularly on day 4, and the second immunization was given one week later with the same concentration of components as the primary immunization. The immunization of B. subtilis spores (COM2 and COM3) was performed by oral administration given for 5 consecutive days a week later than the second immunization. On day 19, all the chickens except the CON group were orally challenged with E. maxima oocysts (1.0 × 10⁴/chicken). The results of the in vivo vaccination showed that all the chickens immunized with rEF-1α (COM1, COM2, and COM3) produced higher (p < 0.05) serum antibodies against EF-1α on 12 days post-E. maxima infection (dpi). The COM3 group showed a significantly (p < 0.05) higher average body weight gain (BWG) on 0-6, 6-9, and 0-12 dpi compared to those of the non-immunized chickens (NC). Immunization with rEF-1α alone (COM1) reduced the gut lesion score on 6 dpi and the fecal oocyst shedding on 9 dpi, whereas co-administration with B. subtilis spores (COM2 or COM3) led to further reduction in the lesion score. E. maxima infection increased the expression levels of IFN-γ and IL-17β in the jejunum, but these expressions were downregulated in the rEF-1α immunized (COM1) group and in the groups immunized with rEF-1α and orally treated with B. subtilis spores (COM2 or COM3) at 4 dpi. A reduced gene expression of occludin in the jejunum of the E. maxima-infected chickens on 4 dpi was upregulated following the immunization with COM2. Collectively, rEF-1α vaccination induced significant protection against E. maxima infection in the broiler chickens, and the efficacy of rEF-1α vaccination was further enhanced by co-administration with orally delivered B. subtilis spores expressing cNK-2.

Helminth-associated changes in host immune phenotype connect top-down and bottom-up interactions during co-infection

1. Within-host parasite interactions can be mediated by the host and changes in host phenotypes often serve as indicators of the presence or intensity of parasite interactions. 2. Parasites like helminths induce a range of physiological, morphological, and immunological changes in hosts that can drive bottom-up (resource-mediated) or top-down (immune-mediated) interactions with co-infecting parasites. Although top-down and bottom-up interactions are typically studied in isolation, the diverse phenotypic changes induced by parasite infection may serve as a useful tool for understanding if, and when, these processes act in concert. 3. Using an anthelmintic treatment study of African buffalo (Syncerus caffer), we tracked changes in host immunological and morphological phenotypes during helminth-coccidia co-infection to investigate their role in driving independent and combinatorial bottom-up and top-down parasite interactions. We also examined repercussions for host fitness. 4. Clearance of a blood-sucking helminth, Haemonchus, from the host gastrointestinal tract induced a systemic Th2 immune phenotype, while clearance of a tissue-feeding helminth, Cooperia, induced a systemic Th1 phenotype. Furthermore, the Haemonchus-associated systemic Th2 immune phenotype drove simultaneous top-down and bottom-up effects that increased coccidia shedding by changing the immunological and morphological landscapes of the intestine. 5. Higher coccidia shedding was associated with lower host body condition, a lower chance of pregnancy, and older age at first pregnancy, suggesting that coccidia infection imposed significant condition and reproductive costs on the host. 6. Our findings suggest that top-down and bottom-up interactions may commonly co-occur and that tracking key host phenotypes that change in response to infection can help uncover complex pathways by which parasites interact.

Poultry gut health and beyond

Intestinal health is critically important for the digestion and absorption of nutrients and thus is a key factor in determining performance. Intestinal health issues are very common in high performing poultry lines due to the high feed intake, which puts pressure on the physiology of the digestive system. Excess nutrients which are not digested and absorbed in the small intestine may trigger dysbiosis, i.e. a shift in the microbiota composition in the intestinal tract. Dysbiosis as well as other stressors elicit an inflammatory response and loss of integrity of the tight junctions between the epithelial cells, leading to gut leakage. In this paper, key factors determining intestinal health and the most important nutritional tools which are available to support intestinal health are reviewed.

The Development of Gut Microbiota and Its Changes Following C. jejuni Infection in Broilers

The gut is home to more than millions of bacterial species. The gut bacteria coexist with the host in a symbiotic relationship that can influence the host's metabolism, nutrition, and physiology and even module various immune functions. The commensal gut microbiota plays a crucial role in shaping the immune response and provides a continuous stimulus to maintain an activated immune system. The recent advancements in high throughput omics technologies have improved our understanding of the role of commensal bacteria in developing the immune system in chickens. Chicken meat continues to be one of the most consumed sources of protein worldwide, with the demand expected to increase significantly by the year 2050. Yet, chickens are a significant reservoir for human foodborne pathogens such as Campylobacter jejuni. Understanding the interaction between the commensal bacteria and C. jejuni is essential in developing novel technologies to decrease C. jejuni load in broilers. This review aims to provide current knowledge of gut microbiota development and its interaction with the immune system in broilers. Additionally, the effect of C. jejuni infection on the gut microbiota is addressed.

Orally delivered Bacillus subtilis expressing chicken NK-2 peptide stabilizes gut microbiota and enhances intestinal health and local immunity in coccidiosis-infected broiler chickens

We recently reported a stable Bacillus subtilis-carrying chicken NK-lysin peptide (B. subtilis-cNK-2) as an effective oral delivery system of an antimicrobial peptide to the gut with therapeutic effect against Eimeria parasites in broiler chickens. To further investigate the effects of a higher dose of an oral B. subtilis-cNK-2 treatment on coccidiosis, intestinal health, and gut microbiota composition, 100 (14-day-old) broiler chickens were allocated into 4 treatment groups in a randomized design: 1) uninfected control (CON), 2) infected control without B. subtilis (NC), 3) B. subtilis with empty vector (EV), and 4) B. subtilis with cNK-2 (NK). All chickens, except the CON group, were infected with 5,000 sporulated Eimeria acervulina (E. acervulina) oocysts on d 15. Chickens given B. subtilis (EV and NK) were orally gavaged (1 × 10¹² cfu/mL) daily from d 14 to 18. Growth performances were measured on d 6, 9, and 13 postinfection (dpi). Spleen and duodenal samples were collected on 6 dpi to assess the gut microbiota, and gene expressions of gut integrity and local inflammation makers. Fecal samples were collected from 6 to 9 dpi to enumerate oocyst shedding. Blood samples were collected on 13 dpi to measure the serum 3-1E antibody levels. Chickens in the NK group showed significantly improved (P < 0.05) growth performance, gut integrity, reduced fecal oocyst shedding and mucosal immunity compared to NC. Interestingly, there was a distinct shift in the gut microbiota profile in the NK group compared to that of NC and EV chickens. Upon challenge with E. acervulina, the percentage of Firmicutes was reduced and that of Cyanobacteria increased. In NK chickens, however, the ratio between Firmicutes and Cyanobacteria was not affected and was similar to that of CON chickens. Taken together, NK treatment restored dysbiosis incurred by E. acervulina infection and showed the general protective effects of orally delivered B. subtilis-cNK-2 on coccidiosis infection. This includes reduction of fecal oocyst shedding, enhancement of local protective immunity, and maintenance of gut microbiota homeostasis in broiler chickens.

Tissue-resident, memory CD8+ T cells are effective in clearing intestinal Eimeria falciformis reinfection in mice

Eimeria, a cousin of malarial parasites, causes coccidiosis that results in huge losses in the poultry industry. Although live coccidiosis vaccines have been developed and used widely for the successful control of the disease, the mechanism underlying protective immunity remains largely unknown. Using Eimeria falciformis as a model parasite, we observed that tissue-resident memory CD8⁺ T (Trm) cells accumulated in cecal lamina propria following E. falciformis infection in mice, especially after reinfection. In convalescent mice challenged with a second infection, E. falciformis burden diminished within 48-72 h. Deep-sequencing revealed that CD8⁺ Trm cells were characterized by rapid up-regulation of effector genes encoding pro-inflammatory cytokines and cytotoxic effector molecules. While FTY720 (Fingolimod) treatment prevented the trafficking of CD8⁺ T cells in peripheral circulation and exacerbated primary E. falciformis infection, such treatment had no impact on the expansion of CD8⁺ Trm cells in convalescent mice receiving secondary infection. Adoptive transfer of cecal CD8⁺ Trm cells conferred immune protection in naïve mice, indicating that these cells provide direct and effective protection against infection. Overall, our findings not only explain a protective mechanism of live oocyst-based anti-Eimeria vaccines but also provide a valuable correlate for assessing vaccines against other protozoan diseases.

Reduced bone formation and increased bone resorption drive bone loss in Eimeria infected broilers

Coccidiosis is an economically significant disease in the global poultry industry, but little is known about the mechanisms of bone defects caused by coccidiosis; thus, the study focused on effects of coccidiosis on the bone homeostasis of young broiler chickens. A total of 480 male Cobb500 broilers were randomly allocated into four treatment groups, including an uninfected control consuming diet ad libitum, two infected groups were orally gavaged with two different concentrations of sporulated Eimeria oocysts, and an uninfected pair-fed group fed the same amount of feed as the high Eimeria-infected group consumed. Growth performance and feed intake were recorded, and samples were collected on 6 days post infection. Results indicated that coccidiosis increased systemic oxidative status and elevated immune response in bone marrow, suppressing bone growth rate (P < 0.05) and increasing bone resorption (P < 0.05) which led to lower bone mineral density (P < 0.05) and mineral content (P < 0.05) under Eimeria infection. With the same amount of feed intake, the uninfected pair-fed group showed a distinguished bone formation rate and bone resorption level compared with the Eimeria infected groups. In conclusion, inflammatory immune response and oxidative stress in broilers after Eimeria infection were closely associated with altered bone homeostasis, highlighting the role of inflammation and oxidative stress in broiler bone homeostasis during coccidiosis.

Recombinant GMA56 and ROP17 of Eimeria magna conferred protection against infection by homologous species

One of the most common rabbits coccidia species, Eimeria magna is mainly parasitic in the ileal and jejunal epithelial cells. E. magna infection can affect the growth performance of rabbits or cause other secondary diseases. Traditional methods of anticoccidial treatment typically result in drug resistance and drug residue. Therefore, vaccination is a promising alternative. Gametocyte antigen 56 (GAM56) and rhoptry kinase family proteins (ROPs) are involved in oocyst wall formation and parasite invasion, respectively. A virulence factor, ROP17 contains a serine/threonine kinase catalytic domain. In this study, recombinant E. magna GAM56 (rEmGAM56) and ROP17 (rEmROP17) proteins were obtained from a prokaryotic expression system and their reactogenicity was investigated with immunoblotting. To assess the potential of rEmGAM56 and rEmROP17 as coccidiosis vaccines, New Zealand White rabbits were subcutaneously immunized with 100 μg rEmGAM56 (rGC group) or rEmROP17 (rRC group) twice at 2-week intervals followed by homologous oocyst challenge. The rabbit serum was collected weekly to detect the specific antibody levels. The cytokine levels of pre-challenge serum were measured by enzyme-linked immunosorbent assay and the rabbits were observed and recorded post-challenge for the onset of clinical symptoms. The weight gain, oocyst output, and feed conversion ratio were calculated at the end of the experiment. The results showed that both rEmGAM56 and rEmROP17 had good reactogenicity. The rEmGAM56- or rEmROP17-immunized rabbits had milder clinical symptoms and feed conversion ratios of 3.27:1 and 3.37:1, respectively. The rEmGAM56-immunized rabbits had 81.35% body weight gain and 63.85% oocyst output reduction; the rEmROP17-immunized rabbits had 79.03% body weight gain and 80.10% oocyst output reduction. The ACI of rGC and rRC groups were 162.35 and 171.03, respectively. The specific antibody levels increased rapidly after immunization. Significantly increased interleukin (IL)-2, interferon (IFN)-γ, and IL-17 levels were evident in the rGC and rRC groups (p < 0.05). The rEmGAM56 and rEmROP17 elicited humoral and cellular responses, which protected against E. magna infection in rabbits. Thus, rEmGAM56 and rEmROP17 are potential vaccine candidates against E. magna, and rEmROP17 performed better than rEmGAM56.

Evolution of developmental and comparative immunology in poultry: The regulators and the regulated

Avian has a unique immune system that evolved in response to environmental pressures in all aspects of innate and adaptive immune responses, including localized and circulating lymphocytes, diversity of immunoglobulin repertoire, and various cytokines and chemokines. All of these attributes make birds an indispensable vertebrate model for studying the fundamental immunological concepts and comparative immunology. However, research on the immune system in birds lags far behind that of humans, mice, and other agricultural animal species, and limited immune tools have hindered the adequate application of birds as disease models for mammalian systems. An in-depth understanding of the avian immune system relies on the detailed studies of various regulated and regulatory mediators, such as cell surface antigens, cytokines, and chemokines. Here, we review current knowledge centered on the roles of avian cell surface antigens, cytokines, chemokines, and beyond. Moreover, we provide an update on recent progress in this rapidly developing field of study with respect to the availability of immune reagents that will facilitate the study of regulatory and regulated components of poultry immunity. The new information on avian immunity and available immune tools will benefit avian researchers and evolutionary biologists in conducting fundamental and applied research.

Implementing real-time immunometabolic assays and immune cell profiling to evaluate systemic immune response variations to Eimeria challenge in three novel layer genetic lines

Introduction

Evaluating differences in immune responses to Eimeria spp. between poultry genetic lines could be valuable for understanding favorable traits to address coccidiosis, a costly poultry disease. The objective was to compare peripheral blood mononuclear cell (PBMC) immunometabolism and composition during Eimeria challenge in three distinct and highly inbred genetic lines; Leghorn Ghs6, Leghorn Ghs13, and Fayoumi M5.1.

Methods

At hatch, 180 chicks (60/ line) were placed in wire-floor cages (10 chicks/cage) and fed a commercial diet. Baseline PBMC were isolated on d21 (10 chicks/line) and 25 chicks/line were inoculated with 10X Merck CocciVac®-B52 (Kenilworth, NJ), creating 6 genetic line × Eimeria groups total. Chicks were euthanized on 1, 3, 7, and 10d post-inoculation (pi; 5 chicks/ line × Eimeria group) for PBMC isolation with body weight and feed intake recorded throughout. Immunometabolic assays to determine PBMC ATP production profiles and glycolytic activity were implemented along with flow cytometric immune cell profiling. Genetic line × Eimeria challenge, and line´challenge fixed effects were analyzed using the MIXED procedure (SAS 9.4; P ≤ 0.05).

Results and Discussion

Before inoculation, M5.1 chicks had 14.4-25.4% greater average daily gain (ADG) with 19.0-63.6% increased monocyte/macrophage⁺, Bu-1⁺ B cell, and CD3⁺ T cell populations compared to both Ghs lines (P < 0.0001) but similar immunometabolic phenotype. The Eimeria main effect reduced ADG by 61.3% from 3-7dpi (P = 0.009) except in M5.1 chicks, where no ADG difference due to challenge was found. At 3dpi, Eimeria-challenged M5.1 chicks had 28.9 and 33.2% reduced PBMC CD3⁺ T cells and CD3⁺CD8α⁺ cytotoxic T cells than unchallenged chicks, suggesting early and preferential recruitment from systemic circulation to tissues local to Eimeria challenge (i.e., intestine; P ≤ 0.01). Both Ghs lines displayed 46.4-49.8% T cell reductions at 10dpi with 16.5-58.9% recruitment favoring underlying CD3⁺CD4⁺ helper T cells. Immunometabolic responses in Eimeria-challenged Ghs6 and Ghs13 chicks were characterized by a 24.0-31.8% greater proportion of ATP from glycolysis compared to unchallenged counterparts at 10dpi (P = 0.04). These results suggest that variable T cell subtype recruitment timelines in addition to altered systemic immunometabolic requirements may work synergistically to determine favorable immune responses to Eimeria challenge.

Phenotypic characterization of Eimeria tenella-specific chicken T-cells responding to in vitro parasite antigen re-stimulation

Introduction. Coccidiosis, caused by protozoan parasites of genus Eimeria, is a disease with large impact on poultry production worldwide. It is well known that Eimeria immunity is dependent on Th1-type responses.Gap Statement. In vitro assessment of Eimeria-specific T-cell activity would therefore be a valuable research tool but has so far proven difficult to establish.Aim. The present study aimed to evaluate in vitro induced blast transformation and CD25 expression in defined chicken T-cell populations as a measure of Eimeria immunity.Methodology. Three E. tenella infection experiments were performed and PBMC and/or spleen cells were collected between 6 and 16 days after infection of chickens. Cells were stimulated in vitro with E. tenella antigens and T-cell activation was assessed by immunofluorescence labelling and flow cytometry.Results. The results consistently showed statistically significant E. tenella specific activation of TCRα/β+T cells within a 'window' from 8 to 14 days after infection for both spleen cells and PBMC. Responding T-cells were identified as CD4+CD8-, CD4+CD8αα+ and CD4-CD8αβ+ where the CD4+CD8αα+ cells generally showed the highest responses. All three of these TCRα/βT-cell subsets showed significant E. tenella induced blast transformation and/or CD25 expression albeit not always in concert on the same days after infection indicating complex kinetics of T-cell responses. In general, responses were higher for spleen cells compared to PBMC for all responding T-cell populations.Conclusions. This methodology shows promise to study Eimeria-specific T-cells, e.g. to evaluate vaccine responses. Results indicated that a Th1-type response was induced and suggested a role for CD4+CD8αα+ cells in Eimeria immunity.

Actin depolymerizing factor-based nanomaterials: A novel strategy to enhance E. mitis-specific immunity

The epidemic of avian coccidiosis seriously threatens the animals' welfare and the economic gains of the poultry industry. Widespread in avian coccidiosis, Eimeria mitis (E. mitis) could obviously impair the production performance of the infected chickens. So far, few effective vaccines targeting E. mitis have been reported, and the nanovaccines composed of nanospheres captured our particular attention. At the present study, we construct two kinds of nanospheres carrying the recombinant E. mitis actin depolymerizing factor (rEmADF), then the characterization was then analyzed. After safety evaluation, the protective efficacy of rEmADF along with its nanospheres were investigated in chickens. The promoted secretions of antibodies and cytokines, as well as the enhanced percentages of CD4⁺ and CD8⁺ T cells were evaluated by the ELISA and flow cytometry assay. In addition, the absolute quantitative real-time PCR (qPCR) assay implied that vaccinations with rEmADF-entrapped nanospheres could significantly reduce the replications of E. mitis in feces. Compared with the rEmADF-loaded chitosan (EmADF-CS) nanospheres, the PLGA nanospheres carrying rEmADF (EmADF-PLGA nanosphers) were more effective in up-regulating weight efficiency of animals and generated equally ability in controlling E. mitis burdens in feces, suggesting the PLGA and CS nanospheres loaded with rEmADF were the satisfactory nanovaccines for E. mitis defense. Collectively, nanomaterials may be an effective antigen delivery system that could help recombinant E. mitis actin depolymerizing factor to enhance immunoprotections in chicken against the infections of E. mitis.