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.

Designing multiepitope-based vaccine against Eimeria from immune mapped protein 1 (IMP-1) antigen using immunoinformatic approach.

Drug resistance against coccidiosis has posed a significant threat to chicken welfare and productivity worldwide, putting daunting pressure on the poultry industry to reduce the use of chemoprophylactic drugs and live vaccines in poultry to treat intestinal diseases. Chicken coccidiosis, caused by an apicomplexan parasite of Eimeria spp., is a significant challenge worldwide. Due to the experience of economic loss in production and prevention of the disease, development of cost-effective vaccines or drugs that can stimulate defence against multiple Eimeria species is imperative to control coccidiosis. This study explored Eimeria immune mapped protein-1 (IMP-1) to develop a multiepitope-based vaccine against coccidiosis by identifying antigenic T-cell and B-cell epitope candidates through immunoinformatic techniques. This resulted in the design of 7 CD8+, 21 CD4+ T-cell epitopes and 6 B-cell epitopes, connected using AAY, GPGPG and KK linkers to form a vaccine construct. A Cholera Toxin B (CTB) adjuvant was attached to the N-terminal of the multiepitope construct to improve the immunogenicity of the vaccine. The designed vaccine was assessed for immunogenicity (8.59968), allergenicity and physiochemical parameters, which revealed the construct molecular weight of 73.25 kDa, theoretical pI of 8.23 and instability index of 33.40. Molecular docking simulation of vaccine with TLR-5 with binding affinity of - 151.893 kcal/mol revealed good structural interaction and stability of protein structure of vaccine construct. The designed vaccine predicts the induction of immunity and boosted host's immune system through production of antibodies and cytokines, vital in hindering surface entry of parasites into host. This is a very important step in vaccine development though further experimental study is still required to validate these results.

Development of a Coccidiosis Disease Challenge Model Using a Commercially Available Live Oocyst Vaccine.

With growing cross-disciplinary collaboration among researchers, it is increasingly important to record detailed methodology to prevent the repetition of preliminary experiments. The purpose of this paper is to explain the development of a coccidiosis challenge model for the investigation of dietary interventions to coccidiosis in broiler chickens. The objectives are to select a dose of mixed species coccidial vaccine and evaluate the suitability (ability to produce a consistent, marked change) of selected response variables important to nutritional studies at different times postinfection (PI). Coccivac-B and Coccivac-B52 (Merck Animal Health) were evaluated as the source of coccidia in three trials. Trials 1 and 2 were randomized complete block designs with four doses (0, 10, 20, or 30 times (×) label dose) of Coccivac-B administered to 12 replicate cages of six birds by repeater pipette (Trial 1) or gavaging needle (Trial 2). Trial 3 used a completely randomized design with 0× or 30× label dose of Coccivac-B52 administered by gavaging needle to six replicate cages of six birds. Birds were gavaged at 15 days of age, and response criteria were evaluated 7 days PI in all trials and again at 10 days PI in Trials 1 and 2. All means are reported in order of increasing coccidia dose with significance accepted at P ≤ 0.05. Broiler performance was not affected by coccidia in Trials 1 or 3 but grew poorer with increasing dose from 0 to 7 days PI in Trial 2 (body weight gain, 465, 421, 388, 365 g; feed to gain, 1.37, 1.47, 1.52, 1.58). As coccidia dose increased, nitrogen corrected apparent metabolizable energy decreased (Trial 1, 3387, 3318, 3267, 3170 kcal kg-1; Trial 2, 3358, 2535, 2422, 2309 kcal kg-1; Trial 3, not measured), while relative weight, length, and content for intestinal sections increased (Trials 1through 3). Gross lesion (duodenum, jejunum/ileum, ceca) and oocyst count scores (jejunum/ileum, ceca) increased with dose; however, gross scoring often suggested infection in unchallenged birds, a finding unsupported by oocyst count scores. At 7 days PI there was no correlation between midgut gross lesion score and midgut oocyst count score (r = 0.06, P = 0.705), but cecal scores were weakly correlated (r = 0.55, P < 0.001). Administering coccidia via repeater pipette (Trial 1) resulted in respiratory distress in some birds, while use of the gavaging needle (Trials 2 and 3) successfully induced intestinal damage in chickens without resulting in coccidia related mortality. Thirty times the label dose at 7 days PI resulted in the greatest number of response variables that produced a consistent, marked change. Therefore, consideration should be given to these conditions when designing future coccidiosis challenge models using vaccines as a source of coccidia.

Artículo regular­Desarrollo de un modelo de desafío para coccidiosis utilizando una vacuna de ooquistes vivos disponible comercialmente. Con la creciente colaboración interdisciplinaria entre investigadores, es cada vez más importante registrar la metodología detallada para evitar la repetición de experimentos preliminares. El propósito de este artículo es explicar el desarrollo de un modelo de desafío de coccidiosis para la investigación de intervenciones dietéticas para coccidiosis en pollos de engorde. Los objetivos son seleccionar una dosis de vacuna coccidial de especies mixtas y evaluar la idoneidad (capacidad de producir un cambio marcado y consistente) de las variables de respuesta seleccionadas que son importantes para los estudios nutricionales en diferentes momentos posteriores a la infección (PI). Las vacunas Coccivac-B o Coccivac B-52 (Merck Animal Health) se evaluaron como fuente de coccidias en tres ensayos. Los ensayos 1 y 2 fueron diseños de bloques completamente aleatorios con cuatro dosis (0, 10, 20 o 30 veces (×) la dosis indicada en la etiqueta) de Coccivac-B administradas a 12 jaulas repetidas de seis aves mediante una pipeta repetidora (ensayo 1) o por sonda oral. (Prueba 2). El ensayo 3 utilizó un diseño completamente aleatorio con una dosis de etiqueta de 0 × o 30 × de Coccivac-B52 administrada con una sonda oral en seis jaulas repetidas de seis aves. Las aves fueron inoculadas por sonda a los 15 días de edad y los criterios de respuesta se evaluaron a los 7 días postinoculación en todos los ensayos y nuevamente a los 10 días postinoculación en los ensayos 1 y 2. Todos los promedios se reportan en orden de dosis crecientes de coccidias con significancia aceptada en P ≤ 0.05. El rendimiento de los pollos de engorde no se vio afectado por las coccidias en los Ensayos 1 o 3, pero empeoró al aumentar la dosis de los cero a 7 días después de la inoculación en el Ensayo 2 (aumento de peso corporal, 465, 421, 388, 365 g; alimento para ganar, 1.37, 1.47, 1.52, 1.58). A medida que aumentaba la dosis de coccidia, la energía metabolizable de nitrógeno aparente y corregida disminuyó (Prueba 1, 3387, 3318, 3267, 3170 kcal kg-1; Prueba 2, 3358, 2535, 2422, 2309 kcal kg-1; Prueba 3, no medida), mientras que el peso relativo, la longitud y el contenido de las secciones intestinales aumentaron (ensayos 1 a 3). La lesión macroscópica (duodeno, yeyuno/íleon, ciego) y las puntuaciones del recuento de oocistos (yeyuno/íleon, ciego) aumentaron con la dosis; sin embargo, la puntuación bruta a menudo sugirió infección en aves no desafiadas, un hallazgo que no está respaldado por las puntuaciones del recuento de ooquistes. A los 7 días después de la infección no hubo correlación entre la puntuación de la lesión macroscópica del intestino medio y la puntuación del recuento de oocistos del intestino medio (r= 0,06, P= 0,705), pero las puntuaciones cecales se correlacionaron débilmente (r = 0.55, P <0.001). La administración de coccidias a través de una pipeta repetidora (Ensayo 1) provocó dificultad respiratoria en algunas aves, mientras que el uso de la sonda oral (Ensayos 2 y 3) indujo con éxito el daño intestinal en los pollos sin dar como resultado mortalidad relacionada con los coccidias. Treinta veces la dosis de la etiqueta a los 7 días después de la infección resultó en el mayor número de variables de respuesta que produjeron un cambio marcado y consistente. Por lo tanto, deben tenerse en cuenta estas condiciones al diseñar futuros modelos de exposición a la coccidiosis que utilicen vacunas como fuente de coccidias.

Kinetics of the Cellular and Transcriptomic Response to Eimeria maxima in Relatively Resistant and Susceptible Chicken Lines.

Eimeria maxima is a common cause of coccidiosis in chickens, a disease that has a huge economic impact on poultry production. Knowledge of immunity to E. maxima and the specific mechanisms that contribute to differing levels of resistance observed between chicken breeds and between congenic lines derived from a single breed of chickens is required. This study aimed to define differences in the kinetics of the immune response of two inbred lines of White Leghorn chickens that exhibit differential resistance (line C.B12) or susceptibility (line 15I) to infection by E. maxima. Line C.B12 and 15I chickens were infected with E. maxima and transcriptome analysis of jejunal tissue was performed at 2, 4, 6 and 8 days post-infection (dpi). RNA-Seq analysis revealed differences in the rapidity and magnitude of cytokine transcription responses post-infection between the two lines. In particular, IFN-γ and IL-10 transcript expression increased in the jejunum earlier in line C.B12 (at 4 dpi) compared to line 15I (at 6 dpi). Line C.B12 chickens exhibited increases of IFNG and IL10 mRNA in the jejunum at 4 dpi, whereas in line 15I transcription was delayed but increased to a greater extent. RT-qPCR and ELISAs confirmed the results of the transcriptomic study. Higher serum IL-10 correlated strongly with higher E. maxima replication in line 15I compared to line C.B12 chickens. Overall, the findings suggest early induction of the IFN-γ and IL-10 responses, as well as immune-related genes including IL21 at 4 dpi identified by RNA-Seq, may be key to resistance to E. maxima.

Response of broiler chickens fed diets supplemented with a bioactive olive pomace extract from Olea europaea to an experimental coccidial vaccine challenge.

This study aimed to investigate an experimental procedure of coccidial challenge in battery cages and the anticoccidial effect of a bioactive olive pomace extract from Olea europaea (OE) in broiler chickens. To this end, four hundred 1-day-old male chicks were randomly assigned to 5 experimental treatments (10 cages/treatment; 8 birds/cage). One group was fed the control diet without any additives and not challenged (NCU). The other 4 groups were challenged and fed the control diet with no additives (NCC) or supplemented with 500 ppm of coccidiostat or with 500 or 1,500 ppm of OE. At 0, 7, and 14 d, all challenged birds, except the NCC group, were orally gavaged with a live Eimeria spp. oocyst vaccine at 1x, 4x, and 16x of the manufacturer's recommended dose, respectively. Feed intake (FI), body weight gain (BWG), and feed conversion ratio (FCR) were determined at 7, 14, 20, and 28 d. At 20 d of age, 1 bird per cage was euthanized to analyze duodenum and jejunum morphology, ileal mucosa gene expression, and plasma cytokine, alpha-1-acid glycoprotein, and carotenoid (CAR) concentrations. Coccidial vaccine challenge lowered BW (P < 0.05) throughout the trial, and reduced FI and BWG, except from 20 to 28d, and increased FCR from 0 to 7, 0 to 14, and 0 to 20 d. Birds in the NCC group had higher (P < 0.05) oocyst counts and lower (P < 0.05) CAR and villus height to crypt depth ratios compared with NCU birds. Overall, coccidia challenge caused the expected reductions in growth performance and gut integrity. While the coccidiostat reduced oocysts excretion, dietary OE or coccidiostat had no effects on performance or gut integrity. The attenuated inflammatory response observed for all the treatments following the third infection can be attributed to the adaptation or immunization to the repetitive exposure to Eimeria spp.

Restoration of anticoccidial sensitivity to a commercial broiler chicken facility in Canada.

Increasing resistance of Eimeria species to anticoccidial medications is an issue in the broiler chicken industry. Using drug-sensitive strains in live-coccidiosis vaccines has been shown to improve anticoccidial effectiveness in US-based broiler production. In Canada, litter is removed between flocks, which differ from the US industry practice. Thus, we investigated the use of drug-sensitive vaccine strains in a Canadian broiler production facility with suspected anticoccidial resistance. Weekly fecal samples were collected from flocks before, during, and after vaccine seeding to determine oocyst shedding patterns; following the vaccine seeding, OPG counts from similar aged birds were lower than flocks before live-coccidiosis vaccine use. Eimeria species isolates, collected before and after vaccine seeding, were used in 2 anticoccidial sensitivity tests to evaluate their susceptibility to commercially available anticoccidial medications; a low-dose challenge to define parasite replication, and a high-dose challenge to monitor broiler performance. In both experiments, isolates collected after seeding were more susceptible to almost every anticoccidial medication evaluated compared with the isolates collected before seeding. These results demonstrate an improvement in sensitivity to many anticoccidials after the use of live-coccidiosis vaccines at this facility. However, the regulated removal of litter at the end of each flock required under Canadian broiler chicken production management rules could limit the establishment of vaccine-strain Eimeria species in broiler facilities and could shorten the longevity of improved drug sensitivity observed in this study.

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

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

Spotlight on avian pathology: the importance of recombinant vector platform technologies in poultry vaccination.

The use of novel vector vaccines (viral, bacterial and apicomplexan) can have a significant impact on the control of poultry disease. They offer a cost effective, convenient and effective means of mass vaccine delivery combined with the ability to switch on both antibody and cell-mediated immunity. In addition, recent viral vector constructs have enabled farmers to vaccinate against up to three important pathogens with a single in ovo administration. As the technology develops, it is likely that this means of vaccine administration will be utilized further and it will play a key role in the control of both existing and new emerging diseases of poultry in the future.

Eimeria ninakohlyakimovae casts NOX-independent NETosis and induces enhanced IL-12, TNF-α, IL-6, CCL2 and iNOS gene transcription in caprine PMN.

Eimeria ninakohlyakimovae represents a highly pathogenic coccidian parasite causing severe haemorrhagic typhlocolitis in goat kids worldwide. NETosis was recently described as an efficient defense mechanism of polymorphonuclear neutrophils (PMN) acting against different parasites in vitro and in vivo. In vitro interactions of caprine PMN with parasitic stages of E. ninakohlyakimovae (i. e. oocysts and sporozoites) as well as soluble oocyst antigens (SOA) were analyzed at different ratios, concentrations and time spans. Extracellular DNA staining was used to illustrate classical molecules induced during caprine NETosis [i. e. histones (H3) and neutrophil elastase (NE)] via antibody-based immunofluorescence analyses. Functional inhibitor treatments with DPI and DNase I were applied to unveil role of NADPH oxidase (NOX) and characterize DNA-backbone composition of E. ninakohlyakimovae-triggered caprine NETosis. Scanning electron microscopy (SEM)- and immunofluorescence-analyses demonstrated that caprine PMN underwent NETosis upon contact with sporozoites and oocysts of E. ninakohlyakimovae, ensnaring filaments which firmly entrapped parasites. Detailed co-localization studies of E. ninakohlyakimovae-induced caprine NETosis revealed presence of PMN-derived DNA being adorned with nuclear H3 and NE corroborating molecular characteristics of NETosis. E. ninakohlyakoimovae-induced caprine NETosis was found to be NOX-independent since DPI inhibition led to a slight decrease of NETosis. Exposure of caprine PMN to vital E. ninakohlyakimovae sporozoites as well as SOA resulted in up-regulation of IL-12, TNF-α, IL-6, CCL2 and iNOS gene transcription in stimulated PMN. Since vital E. ninakohlyakimovae-sporozoites induced caprine NETosis, this effective entrapment mechanism might reduce initial sporozoite epithelial host cell invasion during goat coccidiosis ultimately resulting in less macromeront formation and reduced merozoites I production.

Identification and characterization of a cDNA encoding a gametocyte-specific protein of the avian coccidial parasite Eimeria necatrix.

Gametocyte proteins of Eimeria spp. are essential components of the oocyst wall, and some of these proteins have been analysed to identify targets of transmission-blocking vaccines against avian coccidiosis. In the present study, a cDNA from E. necatrix gametocytes was cloned and sequenced. The cDNA is 1473 bp in length and encodes a 490-amino-acid protein containing a tyrosine-serine (Tyr/Ser)-rich domain and a proline-methionine (Pro/Met)-rich domain. A quantitative real-time PCR (qPCR) analysis showed that the cDNA is expressed only during gametogenesis. A fragment containing the Tyr/Ser-rich domain (rEnGAM59) was expressed in Escherichia coli BL21 (DE3) cells. Immunoblotting showed that rEnGAM59 was recognized by the serum of convalescent chickens after infection with E. necatrix, and that an anti-rEnGAM59 antibody recognized a ∼59 kDa protein and two other proteins (∼35 kDa and ∼33 kDa) in gametocyte extracts. An immunofluorescence assay showed that the anti-rEnGAM59 antibody recognized wall-forming bodies in the macrogametocytes and oocyst walls. An in vivo vaccination and challenge trial was conducted to test the potential utility of rEnGAM59 as a vaccine. Immunized chickens performed better than the unimmunized and challenged (positive control) chickens. The intestinal lesion scores were significantly lower in the immunized groups than in the positive control group (P < 0.05). In contrast, the body weight gains (BWG) were significantly higher in the immunized groups than in the positive control group (P < 0.05). There were no significant differences in the lesion scores and BWG between the groups immunized with rEnGAM59 protein or with live oocysts (P> 0.05). Chickens immunized with rEnGAM59 protein had a significantly higher antigen-specific serum IgY response (P < 0.05). rEnGAM59 protein can be used as candidate antigen to develop a recombinant coccidiosis vaccine.

Modulation of the intestinal microbiota of broilers supplemented with monensin or functional oils in response to challenge by Eimeria spp.

The objective of this study was to evaluate the effect of supplementation with 100ppm sodium monensin or 0.15% of a blend of functional oils (cashew nut oil + castor oil) on the intestinal microbiota of broilers challenged with three different Eimeria spp. The challenge was accomplished by inoculating broiler chicks with sporulated oocysts of Eimeria tenella, Eimeria acervulina, and Eimeria maxima via oral gavage. A total of 864, day-old male broiler chicks (Cobb) were randomly assigned to six treatments (eight pens/treatment; 18 broilers/pen) in a 3 × 2 factorial arrangement, composed of three additives (control, monensin or blend), with or without Eimeria challenge. Intestinal contents was collected at 28 days of age for microbiota analysis by sequencing 16s rRNA in V3 and V4 regions using the Illumina MiSeq platform. Taxonomy was assigned through the SILVA database version 132, using the QIIME 2 software version 2019.1. No treatment effects (p > 0.05) were observed in the microbial richness at the family level estimated by Chao1 and the biodiversity assessed by Simpson's index, except for Shannon's index (p < 0.05). The intestinal microbiota was dominated by members of the order Clostridiales and Lactobacillales, followed by the families Ruminococcaceae, Bacteroidaceae, and Lactobacillaceae, regardless of treatment. When the controls were compared, in the challenged control group there was an increase in Erysipelotrichaceae, Lactobacillaceae, Bacteroidaceae, Streptococcaceae, and Peptostreptococcaceae, and a decrease in Ruminococcaceae. Similar results were found for a challenged group that received monensin, while the blend partially mitigated this variation. Therefore, the blend alleviated the impact of coccidiosis challenge on the microbiome of broilers compared to monensin.

Vaccination with transgenic Eimeria tenella expressing Eimeria maxima AMA1 and IMP1 confers partial protection against high-level E. maxima challenge in a broiler model of coccidiosis.

BACKGROUND: Poultry coccidiosis is a parasitic enteric disease with a highly negative impact on chicken production. In-feed chemoprophylaxis remains the primary method of control, but the increasing ineffectiveness of anticoccidial drugs, and potential future restrictions on their use has encouraged the use of commercial live vaccines. Availability of such formulations is constrained by their production, which relies on the use of live chickens. Several experimental approaches have been taken to explore ways to reduce the complexity and cost of current anticoccidial vaccines including the use of live vectors expressing relevant Eimeria proteins. We and others have shown that vaccination with transgenic Eimeria tenella parasites expressing Eimeria maxima Apical Membrane Antigen-1 or Immune Mapped Protein-1 (EmAMA1 and EmIMP1) partially reduces parasite replication after challenge with a low dose of E. maxima oocysts. In the present study, we have reassessed the efficacy of these experimental vaccines using commercial birds reared at high stocking densities and challenged with both low and high doses of E. maxima to evaluate how well they protect chickens against the negative impacts of disease on production parameters. METHODS: Populations of E. tenella parasites expressing EmAMA1 and EmIMP1 were obtained by nucleofection and propagated in chickens. Cobb500 broilers were immunised with increasing doses of transgenic oocysts and challenged two weeks later with E. maxima to quantify the effect of vaccination on parasite replication, local IFN-γ and IL-10 responses (300 oocysts), as well as impacts on intestinal lesions and body weight gain (10,000 oocysts). RESULTS: Vaccination of chickens with E. tenella expressing EmAMA1, or admixtures of E. tenella expressing EmAMA1 or EmIMP1, was safe and induced partial protection against challenge as measured by E. maxima replication and severity of pathology. Higher levels of protection were observed when both antigens were delivered and was associated with a partial modification of local immune responses against E. maxima, which we hypothesise resulted in more rapid immune recognition of the challenge parasites. CONCLUSIONS: This study offers prospects for future development of multivalent anticoccidial vaccines for commercial chickens. Efforts should now be focused on the discovery of additional antigens for incorporation into such vaccines.

Influence of coccidiosis vaccination on nutrient utilization of corn, soybean meal, and distillers dried grains with solubles in broilers.

Two experiments were conducted to determine the impact of coccidiosis vaccination on the apparent ileal digestibility (AID) of nutrients and ileal digestible energy (IDE) in commonly used feed ingredients in broilers. Eight experimental treatments based on a factorial arrangement of coccidiosis vaccination (control with in-feed diclazuril [CTL] or vaccinated [VAC]) and 4 different diets were administered to male Cobb 500 broilers in floor pens containing 12 birds per pen. For the vaccinated group, a 3× dose of a live coccidiosis vaccine was given via oral gavage on the day of hatch. Experimental diets consisted of a basal diet and 3 test diets in which 30% of the basal diet was replaced with either corn, soybean meal (SBM), or distillers dried grains with solubles (DDGS) to allow for calculation of nutrient digestibility of individual ingredients by difference. Broilers were fed a common diet from 0 to 7 D and experimental diets from 7 to 12 D. On day 12, blood and ileal digesta were collected to measure plasma carotenoids and determine AID of nitrogen, ether extract, IDE (experiments 1 and 2), and amino acids (AA) (experiment 2). Vaccination increased (P < 0.05) excreta oocyst counts and decreased (P < 0.05) plasma carotenoids when compared with CTL birds. Interactive effects (P < 0.05) were observed for AID of nitrogen (experiment 1) which was reduced by vaccination in birds fed the corn diet and increased for birds fed DDGS. No differences (P > 0.05) in IDE were observed between VAC and CTL birds in either experiment, whereas vaccination decreased (P < 0.05) AID of ether extract independently of diet. Interactive effects (P < 0.05) were observed for AA digestibility, whereby digestibility of all AA was reduced by VAC in corn diets but generally increased AA digestibility of DDGS diets, with minimal impact on SBM diets. In conclusion, the impact of coccidiosis vaccination on nutrient and energy digestibility varied among ingredients; however, digestibility was minimally impacted or improved with DDGS.

Expression Analysis and Serodiagnostic Potential of Microneme Proteins 1 and 3 in Eimeria stiedai.

Eimeria stiedai is an apicomplexan protozoan parasite that invades the liver and bile duct epithelial cells in rabbits and causes severe hepatic coccidiosis, resulting in significant economic losses in the domestic rabbit industry. Hepatic coccidiosis lacks the typical clinical symptoms and there is a lack of effective premortem tools to timely diagnose this disease. Therefore, in the present study we cloned and expressed the two microneme proteins i.e., microneme protein 1 (EsMIC1) and microneme protein 3 (EsMIC3) from E. stiedai and used them as recombinant antigens to develop a serodiagnostic method for an effective diagnosis of hepatic coccidiosis. The cDNAs encoding EsMIC1 and EsMIC3 were cloned and the mRNA expression levels of these two genes at different developmental stages of E. stiedai were determined by quantitative real-time PCR analysis (qRT-PCR). The immunoreactivity of recombinant EsMIC1 (rEsMIC1) and EsMIC3 (rEsMIC3) proteins were detected by Western blotting, and indirect enzyme-linked immunosorbent assays (ELISAs) based on these two recombinant antigens were established to evaluate their serodiagnostic potential. Our results showed that the proteins encoded by the ORFs of EsMIC1 (711 bp) and EsMIC3 (891 bp) were approximately 25.89 and 32.39 kDa in predicted molecular weight, respectively. Both EsMIC1 and EsMIC3 showed the highest mRNA expression levels in the merozoites stage of E. stiedai. Western blotting analysis revealed that both recombinant proteins were recognized by E. stiedai positive sera, and the indirect ELISAs using rEsMIC1 and rEsMIC3 were developed based on their good immunoreactivity, with 100% (48/48) sensitivity and 97.9% (47/48) specificity for rEsMIC1 with 100% (48/48) sensitivity and 100% (48/48) specificity for rEsMIC3, respectively. Moreover, rEsMIC1- and rEsMIC3-based indirect ELISA were able to detect corresponding antibodies in sera at days 6, 8, and 10 post E. stiedai infection, with the highest positive diagnostic rate (62.5% (30/48) for rEsMIC1 and 66.7% (32/48) for rEsMIC3) observed at day 10 post infection. Therefore, both EsMIC1 and EsMIC3 can be used as potential serodiagnostic candidate antigens for hepatic coccidiosis caused by E. stiedai.

Still naïve or primed: Anticoccidial vaccines call for memory.

Despite decades of investigation to clarify protective mechanisms of anticoccidial responses, one crucial field is neglected, that is, protective memory responses in primed birds. Protective memory immunity is critical for host resistance to reinfection and is the basis of modern vaccinology, especially in developing successful subunit vaccines. There are important differences between the immune responses induced by infections and antigens delivered either as killed, recombinant proteins or as live, replicating vector vaccines or as DNA vaccines. Animals immunized with these vaccines may fail to develop protective memory immunity, and is still naïve to Eimeria infection. This may explain why limited success is achieved in developing next-generation anticoccidial vaccines. In this review, we try to decipher the protective memory responses against Eimeria infection, assess immune responses elicited by various anticoccidial vaccine candidates, and propose possible approaches to develop rational vaccines that can induce a protective memory response to chicken coccidiosis.

Type 1 Treg cells promote the generation of CD8+ tissue-resident memory T cells.

Tissue-resident memory T (TRM) cells, functionally distinct from circulating memory T cells, have a critical role in protective immunity in tissues, are more efficacious when elicited after vaccination and yield more effective antitumor immunity, yet the signals that direct development of TRM cells are incompletely understood. Here we show that type 1 regulatory T (Treg) cells, which express the transcription factor T-bet, promote the generation of CD8+ TRM cells. The absence of T-bet-expressing type 1 Treg cells reduces the presence of TRM cells in multiple tissues and increases pathogen burden upon infectious challenge. Using infection models, we show that type 1 Treg cells are specifically recruited to local inflammatory sites via the chemokine receptor CXCR3. Close proximity with effector CD8+ T cells and Treg cell expression of integrin-ß8 endows the bioavailability of transforming growth factor-ß in the microenvironment, thereby promoting the generation of CD8+ TRM cells.

Effects of stage of broiler embryo development on coccidiosis vaccine injection accuracy, and subsequent oocyst localization and hatchling quality.

Control of coccidiosis in broiler chickens continues to pose challenges to commercial poultry producers, especially in an era of increased consumer demand for antibiotic-free broiler production. As a result, coccidiosis vaccines are now commonly used in rotation programs to achieve effective coccidiosis control. Inovocox EM1 vaccine (EM1) is a coccidiosis vaccine that allows for earlier immune acquisition through oocyst cycling, which reduces the effects of wild-type coccidia. The EM1 vaccine is administered to embryonated broiler hatching eggs between 18 and 19 D of incubation (doi). In the U.S., commercial broiler hatcheries vaccinate embryonated eggs at either 18.5 or 19 doi. However, it is unclear whether a difference in embryo age at the time of in ovo injection can impact the actual site of vaccine delivery. In addition, it is unclear where oocysts eventually become localized within the embryo following the in ovo injection of EM1. Therefore, the objective of this study was to determine the effects of stage of embryonic development on the actual deposition site of the EM1 vaccine oocysts when they are in ovo injected and to subsequently investigate the movement and eventual location of EM1 oocysts after in ovo injection. Because all eggs were injected at the same time, a 12-h difference in set time was a means to derive 18.5 and 19.0 incubation age of injection (IAN) treatments. The experimental design was a 3 injection treatment (noninjected, diluent-injected, and vaccine-injected) × 2 IAN factorial. There was a significant main effect of IAN on site of vaccine oocysts delivery, and subsequent hatching chick quality. Qualitative histological evaluation revealed the oral uptake of vaccine oocysts through the amnion, with their subsequent presence in the gizzard and intestinal lumen by 24 to 36 h postinjection. In conclusion, physiological development influenced the site of injection, and oocysts imbibed along with the amniotic fluid in late stage broiler embryos are subsequently transported to the gastrointestinal tract.

Immunoproteomic and mass spectrometric analysis of Eimeria acervulina antigens recognized by antisera from chickens infected with E. acervulina, E. tenella or E. necatrix.

BACKGROUND: Coccidiosis is caused by Eimeria spp. and can result in severe economic losses to the global poultry industry. Due to anticoccidial drug resistance rapidly developing in the parasites and drug residues in poultry products, efficacious and safe alternative coccidia control measures are needed. The objective of the present study was to identify common protective antigens which may be used as vaccine candidates in the development of subunit, multivalent, cross-protective vaccines against most of the economically important Eimeria species. METHODS: Whole sporozoite proteins of Eimeria acervulina were prepared and analyzed by 2-dimensional gel electrophoresis (2-DE) followed by western blotting using immune sera specific to E. tenella, E. acervulina, or E. necatrix. The protein spots detected by all three immune sera were then excised from the preparative gel and protein ID was performed by MALDI-TOF-MS/MS. RESULTS: Approximately 620 E. acervulina sporozoite protein spots were demonstrated by 2-DE with silver staining, among which 23 protein spots were recognized by immune sera specific to all three Eimeria species. The results showed that 21 putative E. acervulina proteins were identified, which include proteins with known enzymatic properties, and those which are involved in protein translation, transport and trafficking, and ribosomal biogenesis and functions. There is one protein which may be involved in transcription and one heat-shock protein. Two proteins contain predicted domains, but with no apparent functions known. There were 2 protein spots which had no detectable proteins. None of the proteins has a predicted signal peptide or a transmembrane domain; however, 6 of the 21 putative proteins were predicted to be potentially secretory through the non-classical pathway. CONCLUSIONS: Our study identified a diverse group of antigens immunologically common to all three Eimeria species, none of which was previously characterized and tested as a vaccine candidate. Further research on immunogenicity and cross-protective potential of these individual proteins as vaccine candidates will aid the development of vaccines against the most common and pathogenic Eimeria spp.

Involvement of T Cell Immunity in Avian Coccidiosis.

Avian coccidiosis is caused by Eimeria, which is an intracellular apicomplexan parasite that invades through the intestinal tract to cause devastating disease. Upon invasion through the intestinal epithelial cells, a strong inflammatory response is induced that results in complete villous destruction, diarrhea, hemorrhage, and in severe cases, death. Since the life cycle of Eimeria parasites is complex and comprises several intra- and extracellular developmental stages, the host immune responses are diverse and complex. Interferon-γ-mediated T helper (Th)1 response was originally considered to be the predominant immune response in avian coccidiosis. However, recent studies on other avian T cell lineages such as Th17 and T regulatory cells have implicated their significant involvement in maintaining gut homeostasis in normal and disease states including coccidiosis. Therefore, there is a need to understand better their role in coccidiosis. This review focuses on research findings concerning the host immune response induced by avian coccidiosis in the context of T cell immunity, including expression of T-cell-related cytokines and surface molecules that determine the phenotype of T lymphocytes.

Immune protection provided by a precocious line trivalent vaccine against rabbit Eimeria.

A pilot study was conducted to evaluate the pathogenicity and immunogenicity of vaccinated rabbits with different doses of oocysts (5 × 102, 1 × 103, 1 × 104, and 5 × 104) of a precocious line, including Eimeria magna, E. intestinalis or E. media following the challenge with their corresponding parent strains. Our results showed that each precocious line had weak pathogenicity but good immunogenicity in terms of clinical symptoms, average daily weight gains (ADGs), and oocyst outputs. Therefore, a precocious line trivalent vaccine, including E. magna, E. intestinalis, and E. media was formulated. A total of sixty 40-day-old coccidia-free rabbits were allocated to ten treatments with a 2 × 3 factorial arrangement that included 2 vaccination doses (5 × 102 or 1 × 103 oocysts of the precocious line). Groups I to Ⅷ and Unimmunized Challenged Control group were challenged with mixed oocysts of their corresponding parent strains (1 × 104 oocysts of each parent strain) 14 days after vaccination. No clinical symptoms were observed in the immunized groups after vaccination. Average daily weight gains (ADGs) were similar to those of unimmunized unchallenged controls (P > 0.05) after vaccination or after challenge. Oocyst outputs in the vaccinated challenged groups were significantly different from those of unimmunized challenged controls (P < 0.01) after challenge. These results indicated that the trivalent vaccine could provide immune protection against coccidiosis and therefore, it could be used as a candidate vaccine.