Protective immunity induced by a DNA vaccine encoding Eimeria tenella rhomboid against homologous challenge

Effects of prebiotic (lactoferrin) and diclazuril on broiler chickens experimentally infected with Eimeria tenella

Introduction

Avian coccidiosis presents a significant challenge to the poultry industry in Egypt, highlighting the urgent need for validating new drug targets offering promising prospects for the development of advanced anticoccidials. Although numerous reports highlight the activity of lactoferrin (LF) against various microorganisms, its potential against Eimeria has not been explored. The present study evaluated the potential anticoccidial effect of LF and diclazuril in broiler chickens experimentally infected with Eimeria tenella.

Methods

A total of 100 one-day-old broiler chicks were divided into five equal groups (20 each) as follows: Group 1 (G1) served as the normal healthy control group, Group 2 (G2) consisted of chickens infected with 1 × 105 sporulated E. tenella oocysts at 14 days of age, Group 3 (G3) comprised infected chickens treated with diclazuril (0.5 mL/L in drinking water) for 3 days successively, Group 4 (G4) included infected chickens treated with LF (at a dose of 250 mg/kg of diet) from one day of age until the end of the study, and Group 5 (G5) comprised infected chickens treated with both LF and diclazuril.

Results

The positive control group (G2) experienced significant reductions in body weight (BW), BW gain, serum glucose, lipase, amylase, total antioxidant capacity, several hematological indices, and total proteins, along with alterations in various antioxidant enzymes. Conversely, serum levels of aspartate aminotransferase (AST), Alanine aminotransferase (ALT), Alkaline phosphatases (ALP), urea, creatinine, nitric oxide, mean corpuscular volume (MCV), White blood cells (WBCs), heterophils, alpha 2, beta 1, and liver contents of malondialdehyde were elevated in this group. Moreover, higher oocyst counts and lesion scores, along with histopathological alterations, were observed in G2. Remarkably, treatment with diclazuril and/or LF demonstrated potent antioxidant and anticoccidial effects, resulting in reduced shedding of oocysts, lesion scores, and lymphocytic infiltrates in the cecum. Additionally, these treatments improved the antioxidant and immune systems in chickens and restored all histopathological changes reported in the infected non-treated group (G2).

Conclusion

This study offers novel perspectives on the potential anticoccidial effects of the combination of LF and diclazuril in broiler chickens infected with E. tenella, highlighting the potential synergistic actions of LF in treating poultry coccidiosis.

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.

Construction of a Lactobacillus plantarum-based claudin-3 targeting delivery system for the development of vaccines against Eimeria tenella

Avian coccidiosis causes huge economic losses to the poultry industry worldwide and currently lacks effective live vector vaccines. Achieving efficient antigen delivery to mucosa-associated lymphoid tissue (MALT) is critical for improving the effectiveness of vaccines. Here, chicken claudin-3 (CLDN3), a tight junction protein expressed in MALT, was identified as a target, and the C-terminal region of Clostridium perfringens enterotoxin (C-CPE) was proven to bind to chicken CLDN3. Then, a CLDN3-targeting Lactobacillus plantarum NC8-expressing C-CPE surface display system (NC8/GFP-C-CPE) was constructed to successfully express the heterologous protein on the surface of L. plantarum. The colonization level of NC8/GFP-C-CPE was significantly increased compared to the non-targeting strain and could persist in the intestine for at least 72 h. An oral vaccine strain expressing five EGF domains of Eimeria tenella microneme protein 8 (EtMIC8-EGF) (NC8/EtMIC8-EGF-C-CPE) was constructed to evaluate the protective efficacy against E. tenella infection. The results revealed that CLDN3-targeting L. plantarum induced stronger mucosal immunity in gut-associated lymphoid tissues (GALT) as well as humoral responses and conferred better protection in terms of parasite replication and pathology than the non-targeting strain. Overall, we successfully constructed a CLDN3-targeting L. plantarum NC8 surface display system characterized by MALT-targeting, which is an efficient antigen delivery system to confer enhanced protective efficacy in chickens against E. tenella infection.

Protective efficacy induced by Eimeria maxima rhomboid-like protein 1 against homologous infection

Introduction

Avian coccidiosis, caused by apicomplexan protozoa belonging to the Eimeria genus, is considered one of the most important diseases in the intensive poultry industry worldwide. Due to the shortcomings of live anticoccidial vaccines and drugs, the development of novel anticoccidial vaccines is increasingly urgent.

Methods

Eimeria maxima rhomboid-like protein 1 (EmROM1), an invasion-related molecule, was selected as a candidate antigen to evaluate its protective efficacy against E. maxima in chickens. Firstly, the prokaryotic recombinant plasmid pET-32a-EmROM1 was constructed to prepare EmROM1 recombinant protein (rEmROM1), which was used as a subunit vaccine. The eukaryotic recombinant plasmid pVAX1.0-EmROM1 (pEmROM1) was constructed as a DNA vaccine. Subsequently, 2-week-old chicks were separately vaccinated with the rEmROM1 and pEmROM1 twice every 7 days. One week post the booster vaccination, induced cellular immune responses were determined by evaluating the mRNA level of cytokines including IL-2, IFN-γ, IL-4, IL-10, TGF-β, IL-17, and TNFSF15, as well as the percentages of CD4⁺ and CD8⁺ T cells from spleens of vaccinated chickens. Specific serum antibody level in the vaccinated chickens was determined to assess induced humoral immune responses. Finally, the protective efficacy of EmROM1 was evaluated by a vaccination-challenge trial.

Results

EmROM1 vaccination significantly upregulated the cytokine transcription levels and CD4⁺/CD8⁺ T cell percentages in vaccinated chickens compared with control groups, and also significantly increased the levels of serum-specific antibodies in vaccinated chickens. The animal trial showed that EmROM1 vaccination significantly reduced oocyst shedding, enteric lesions, and weight loss of infected birds compared with the controls. The anticoccidial index (ACI) from the rEmROM-vaccination group and pEmROM1-vaccination group were 174.11 and 163.37, respectively, showing moderate protection against E. maxima infection.

Discussion

EmROM1 is an effective candidate antigen for developing DNA or subunit vaccines against avian coccidiosis.

Vaccines against chicken coccidiosis with particular reference to previous decade: progress, challenges, and opportunities

Chicken coccidiosis is an economically significant disease of commercial chicken industry accounting for losses of more than £10.4 billion (according to 2016 prices). Additionally, the costs incurred in prophylaxis and therapeutics against chicken coccidiosis in developing countries (for instance Pakistan according to 2018 prices) reached US $45,000.00 while production losses for various categories of chicken ranges 104.74 to US $2,750,779.00. The infection has been reported from all types of commercial chickens (broiler, layer, breeder) having a range of reported prevalence of 7-90%. The concern of resistance towards major anticoccidials has provided a way forward to vaccine research and development. For prophylaxis of chicken coccidiosis, live virulent, attenuated, ionophore tolerant strains and recombinant vaccines have been extensively trialed and commercialized. Eimeria antigens and novel vaccine adjuvants have elicited the protective efficacy against coccidial challenge. The cost of production and achieving robust immune responses in birds are major challenges for commercial vaccine production. In the future, research should be focused on the development of multivalent anticoccidial vaccines for commercial poultry. Efforts should also be made on the discovery of novel antigens for incorporation into vaccine designs which might be more effective against multiple Eimeria species. This review presents a recap to the overall progress against chicken Eimeria with particular reference to previous decade. The article presents critical analysis of potential areas for future research in chicken Eimeria vaccine development.

A multiepitope vaccine encoding four Eimeria epitopes with PLGA nanospheres: a novel vaccine candidate against coccidiosis in laying chickens

With a worldwide distribution, Eimeria spp. could result in serious economic losses to the poultry industry. Due to drug resistance and residues, there are no ideal drugs and vaccines against Eimeria spp. in food animals. In the current study, a bioinformatics approach was employed to design a multiepitope antigen, named NSLC protein, encoding antigenic epitopes of E. necatrix NA4, E. tenella SAG1, E. acervulina LDH, and E. maxima CDPK. Thereafter, the protective immunity of NSLC protein along with five adjuvants and two nanospheres in laying chickens was evaluated. Based on the humoral immunity, cellular immunity, oocyst burden, and the coefficient of growth, the optimum adjuvant was evaluated. Furthermore, the optimum immune route and dosage were also investigated according to the oocyst burden and coefficient of growth. Accompanied by promoted secretion of antibodies and enhanced CD4⁺ and CD8⁺ T lymphocyte proportions, NSLC proteins entrapped in PLGA nanospheres were more effective in stimulating protective immunity than other adjuvants or nanospheres, indicating that PLGA nanospheres were the optimum adjuvant for NSLC protein. In addition, a significantly inhibited oocyst burden and growth coefficient promotion were also observed in animals vaccinated with NSLC proteins entrapped in PLGA nanospheres, indicating that the optimum adjuvant for NSLC proteins was PLGA nanospheres. The results also suggested that the intramucosal route with PLGA nanospheres containing 300 μg of NSLC protein was the most efficient approach to induce protective immunity against the four Eimeria species. Collectively, PLGA nanospheres loaded with NSLC antigens are potential vaccine candidates against avian coccidiosis.

Evaluation of immunoprotective effects of recombinant proteins and DNA vaccines derived from Eimeria tenella surface antigen 6 and 15 in vivo

Coccidiosis is an intestinal parasitic disease that causes huge economic losses to the poultry industry globally. Eimeria tenella belonging to protozoon is the causative agent of cecal coccidiosis in chicken, and it causes enormous damage to poultry industry. The surface antigens (SAGs) of apicomplexan parasites have functions of attachment and invasion in host-parasite interaction. As a result of parasitic invasion, host immune response is triggered. However, the immunogenicity and potency of E. tenella surface antigen 6 and 15 (EtSAG 6 and 15), as vaccinal candidate antigen, remain largely unknown. Therefore, gene fragments of E. tenella EtSAG 6 and 15 were amplified and transformed to pET28a prokaryotic vector for recombinant protein expression. The pEGFP-N1 eukaryotic vectors with EtSAG 6 and 15 amplification fragments (pEGFP-N1-EtSAG 5 and 16) were transformed into 293 T cell line. The results of reverse transcription-polymerase chain reaction (RT-PCR) and western blot analysis revealed successful expressions of EtSAG 6 and 15 in Escherichia coli and 293 T cells. Subsequently, animal experiments of 49 cobb broilers were performed to evaluate immunoprotection of recombinant proteins and DNA vaccines derived from E. tenella EtSAG 5 and 16 with an immunizing dose of 100 μg, respectively. Chickens vaccinated with rEtSAG 6 protein, rEtSAG 15 protein, pEGFP-N1-EtSAG 6 plasmid, or pEGFP-N1-EtSAG 15 plasmid showed no significant increase in IFN-γor interleukin-4 (IL-4) level compared with control groups. Chickens vaccinated with protein rEtSAG 6, protein rEtSAG 15, pEGFP-N1-EtSAG 6 plasmid, or pEGFP-N1-EtSAG 15 exhibited higher weight gains, lower oocyst output, and lower mean lesion scores, compared with infection control group. Among the four immunized groups, plasmid EGFP-N1-EtSAG 6 (100 μg) group exhibited the highest anticoccidial index (ACI) value (150.20). Overall, plasmids EGFP-N1-EtSAG 6 and 15, as DNA vaccines, provided a more effective immunoprotection for chickens against E. tenella than protein rEtSAG 6 and protein rEtSAG 15 as subunit vaccines. EtSAG 6 and 15 are promising candidate antigen genes for developing coccidiosis vaccine.

Transcriptome Analysis Revealed Ameliorative Effects of Bacillus Based Probiotic on Immunity, Gut Barrier System, and Metabolism of Chicken under an Experimentally Induced Eimeria tenella Infection

In this study, we performed transcriptome analysis in the cecum tissues of negative control untreated non-challenged (NC), positive control untreated challenged (PC), and Bacillus subtilis (B. subtilis) fed challenged chickens (BS + ET) in order to examine the underlying potential therapeutic mechanisms of Bacillus based probiotic feeding under an experimental Eimeria tenella (E. tenella) infection. Our results for clinical parameters showed that birds in probiotic diet decreased the bloody diarrhea scores, oocyst shedding, and lesion scores compared to positive control birds. RNA-sequencing (RNA-seq) analysis revealed that in total, 2509 up-regulated and 2465 down-regulated differentially expressed genes (DEGs) were detected in the PC group versus NC group comparison. In the comparison of BS + ET group versus PC group, a total of 784 up-regulated and 493 down-regulated DEGs were found. Among them, several DEGs encoding proteins involved in immunity, gut barrier integrity, homeostasis, and metabolism were up-regulated by the treatment of probiotic. Functional analysis of DEGs also revealed that some gene ontology (GO) terms related with immunity, metabolism and cellular development were significantly affected by the exposure of probiotic. Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis showed that the DEGs in the cecum of B. subtilis-fed challenged group were mainly participated in the pathways related with immunity and gut barrier integrity, included mitogen-activated protein kinase (MAPK) signaling pathway, toll-like receptor (TLR) signaling pathway, extracellular matrix (ECM)–receptor interaction, tight junction, and so on. Taken together, these results suggest that Bacillus based probiotic modulate the immunity, maintain gut homeostasis as well as barrier system and improve chicken metabolism during E. tenella infection.

Evaluation of immunoprotective effects of recombinant protein and DNA vaccine based on Eimeria tenella surface antigen 16 and 22 in vivo

Coccidiosis triggered by Eimeria tenella is accompanied by haemorrhagic caecum and high morbidity. Vaccines are preferable choices to replace chemical drugs against coccidiosis. Surface antigens of apicomplexan parasites can adhere to host cells during the infection process. Therefore, truncated fragments coding E. tenella surface antigen 16 (EtSAG16) and 22 (EtSAG22) were cloned into pET-28a prokaryotic vector to express recombinant protein 16 (rEtSAG16) and 22 (rEtSAG22), respectively. Likewise, pEGFP-N1-EtSAG16 and pEGFP-N1-EtSAG22 plasmids were constructed using pEGFP-N1 eukaryotic vector. Further, pEGFP-N1-EtSAG4-16-22 multiple gene plasmid carrying EtSAG4, 16 and 22 were designed as cocktail vaccines to study integral immunoprotective effects. Western blot and RT-PCR (reverse transcription) assay were performed to verify expressions of EtSAG16 and 22 genes. Immunoprotective effects of recombinant protein or DNA vaccine were evaluated using different doses (50 or 100 μg) in vivo. All chickens in the vaccination group showed higher cytokine concentration (IFN-γ and IL-17), raised IgY antibody level, increased weight gain, lower caecum lesion score and reduced oocyst shedding compared with infection control groups (p < 0.05). The highest anticoccidial index (ACI) value 173.11 was from the pEGFP-N1-EtSAG4-16-22 plasmid (50 μg) group. In conclusion, EtSAG16 and 22 might be alternative candidate genes for generating vaccines against E. tenella infection.

Rhomboid protein 2 of Eimeria maxima provided partial protection against infection by homologous species

Rhomboid-like proteases (ROMs) are considered as new candidate antigens for developing new-generation vaccines due to their important role involved in the invasion of apicomplexan protozoa. In prior works, we obtained a ROM2 sequence of Eimeria maxima (EmROM2). This study was conducted to evaluate the immunogenicity and protective efficacy of EmROM2 recombinant protein (rEmROM2) and EmROM2 DNA (pVAX1-EmROM2) against infection by Eimeria maxima (E. maxima). Firstly, Western blot assay was conducted to analyze the immunogenicity of rEmROM2. The result showed that rEmROM2 was recognized by chicken anti-E. maxima serum. Reverse transcription-polymerase chain reaction (RT-PCR) and Western blot assay revealed apparent transcription and expression of EmROM2 at the injection site. qRT-PCR (quantitative real-time PCR), flow cytometry and indirect ELISA indicated that vaccination with rEmROM2 or EmROM2 DNA significantly upregulated the transcription level of cytokines (IFN-γ, IL-2, IL-4, IL-10, IL-17, TGF-β and TNF SF15), the proportion of CD8⁺ and CD4⁺ T lymphocytes and serum IgG antibody response. Ultimately, a vaccination-challenge trial was performed to evaluate the protective efficacy of rEmROM2 and pVAX1-EmROM2 against E. maxima. The result revealed that vaccination with rEmROM2 or pVAX1-EmROM2 significantly alleviated enteric lesions, weight loss, and reduced oocyst output caused by challenge infection of E. maxima, and provided anticoccidial index (ACI) of more than 160, indicating partial protection against E. maxima. In summary, vaccination with rEmROM2 or pVAX1-EmROM2 activated notable humoral and cell-mediated immunity and provided partial protection against E. maxima. These results demonstrated that EmROM2 protein and DNA are promising vaccine candidates against E. maxima infection.

Pharmacokinetics and anticoccidial activity of ethanamizuril in broiler chickens

The treatment effect of ethanamizuril (EZL) to broiler chickens experimentally infected with 8 × 104Eimeria tenella was evaluated. On the third day after infection, the broiler chickens were treated with EZL by gavage at doses of 2, 4, and 8 mg/kg body weight (bw) for once. For double administration, the challenged broiler chickens were administered EZL at doses of 1, 2, 4, and 8 mg/kg bw by gavage continually on the third day and fourth day and once a day. Throughout the experimental period, performance parameters including body weight gain, mortality, cecal lesion score, bloody diarrhoea and oocyst output were recorded. The anticoccidial efficacy was evaluated using the anticoccidial index (ACI). Meanwhile, the concentrations of EZL in chicken cecal contents were measured, and the data were analyzed with a non-compartmental model. The results indicated that EZL showed good anticoccidial activity at single dose of 4 mg/kgbw, with the corresponding ACI of 175.73. When the challenged chickens were treated with EZL under double administration, the EZL showed a medium level of anticoccidial activity at a dose of 2 mg/kg bw, with the corresponding ACI of 162.48. The maximum concentrations (Cmax) of EZL in content were 2.43 ± 1.16, 4.28 ± 1.56, and 8.57 ± 1.33 mg/kg after the chickens were administrated at doses of 2, 4, and 8 mg/kg bw, respectively. The respective areas under the curve were 36.93 ± 8.91, 96 ± 16.31, and 262.76 ± 51.52 mg/kg h. The respective half-lives (T1/2) were 10.82 ± 2.02, 10.53 ± 2.23, and 10.60 ± 1.50 h. The results show that when the concentrations of EZL in chicken cecal contents reached 4.28 ± 1.56 mg/kg, there is a significant therapeutic effect on chicken coccidiosis.

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.

In vivo immunoprotective comparison between recombinant protein and DNA vaccine of Eimeria tenella surface antigen 4

Eimeria tenella, belonging to protozoon, is the causative agent of cecal coccidiosis in chicken and causes enormous impacts for poultry industry. The surface antigens of apicomplexan parasites function as attachment and invasion in host-parasite interaction. Meanwhile, host immune response is triggered as a result of parasitic invasion. Immunogenicity and potency as a vaccinal candidate antigen of E. tenella surface antigen 4 (EtSAG4) have been unknown. Therefore, a gene segment of E. tenella EtSAG4 was amplified and transplanted to pET28a prokaryotic vector for recombinant protein expression. Similarly, pEGFP-N1 eukaryotic vectors with EtSAG4 gene segment (pEGFP-N1-EtSAG4) amplified in 293 T cells as DNA vaccines. Reverse transcription-polymerase chain reaction (RT-PCR) assay and western blot analysis were used to demonstrate successful expressions of EtSAG4 in Escherichia coli or 293 T cells. Subsequently, animal experiments (72 cobb broilers) were performed to evaluate immunoprotective between recombinant protein and DNA vaccine of E. tenella EtSAG4 using different immunizing doses (50 or 100 μg), respectively. Serum from chickens infected with E. tenella identified recombinant EtSAG4 (rEtSAG4) protein. Chickens vaccinated with either rEtSAG4 protein or pEGFP-N1-EtSAG4 plasmids both shown a significant increase in concentration of IFN-γ (p < 0.05) compared with control groups indicating production of cell-mediated immunity. Besides, pEGFP-N1-EtSAG4 plasmids motivated more intense immune responses for immunoglobulin Y (IgY) and interleukin 17 (IL-17) (p < 0.05) contrast to control groups. However, there was no increase in concentration of interleukin 10 (IL-10) and interleukin 4 (IL-4) for both rEtSAG4 protein and pEGFP-N1-EtSAG4 plasmids. Chickens vaccinated with rEtSAG4 protein or pEGFP-N1-EtSAG4 plasmids both show higher weight, lower oocyst output and mean lesion scores compared with infection control groups. The highest anticoccidial index (ACI) value of immunized groups was 168.24 from EGFP-N1-EtSAG4 plasmids (100 μg) group. Generally, EGFP-N1-EtSAG4 plasmids as DNA vaccines provided a more effective immunoprotective for chickens against E. tenalla than that of rEtSAG4 protein as subunit vaccines. EtSAG4 is a promising candidate antigen gene for development of coccidiosis vaccine.

A review of Eimeria antigen identification for the development of novel anticoccidial vaccines

Coccidiosis is a major poultry disease which compromises animal welfare and costs the global chicken industry a huge economic loss. As a result, research entailing coccidial control measures is crucial. Coccidiosis is caused by Eimeria parasites that are highly immunogenic. Consequently, a low dosage of the Eimeria parasite supplied by a vaccine will enable the host organism to develop an innate immune response towards the pathogen. The production of traditional live anticoccidial vaccines is limited by their low reproductive index and high production costs, among other factors. Recombinant vaccines overcome these limitations by eliciting undesired contaminants and prevent the reversal of toxoids back to their original toxigenic form. Recombinant vaccines are produced using defined Eimeria antigens and harmless adjuvants. Thus, studies regarding the identification of potent novel Eimeria antigens which stimulate both cell-mediated and humoral immune responses in chickens are essential. Although the prevalence and risk posed by Eimeria have been well established, there is a dearth of information on genetic and antigenic diversity within the field. Therefore, this paper discusses the potential and efficiency of recombinant vaccines as an anticoccidial control measure. Novel protective Eimeria antigens and their antigenic diversity for the production of cheap, easily accessible recombinant vaccines are also reviewed.

RNA Sequencing Analysis of Chicken Cecum Tissues Following Eimeria tenella Infection in Vivo

Eimeria tenella (E. tenella) is one of the most frequent and pathogenic species of protozoan parasites of the genus Eimeria that exclusively occupies the cecum, exerting a high economic impact on the poultry industry. To investigate differentially expressed genes (DEGs) in the cecal tissue of Jinghai yellow chickens infected with E. tenella, the molecular response process, and the immune response mechanism during coccidial infection, RNA-seq was used to analyze the cecal tissues of an E. tenella infection group (JS) and an uninfected group (JC) on the seventh day post-infection. The DEGs were screened by functional and pathway enrichment analyses. The results indicated that there were 5477 DEGs (p-value < 0.05) between the JS and the JC groups, of which 2942 were upregulated, and 2535 were downregulated. GO analysis indicated that the top 30 significantly enriched GO terms mainly involved signal transduction, angiogenesis, inflammatory response, and blood vessel development. KEGG analysis revealed that the top significantly enriched signaling pathways included focal adhesion, extracellular matrix-receptor interaction, and peroxisome proliferator-activated receptor. The key DEGs in these pathways included ANGPTL4, ACSL5, VEGFC, MAPK10, and CD44. These genes play an important role in the infection of E. tenella. This study further enhances our understanding of the molecular mechanism of E. tenella infection in chickens.

Effect of Dual Infection with Eimeria tenella and Subgroup J Avian Leukosis Virus on the Cecal Microbiome in Specific-Pathogen-Free Chicks

Understanding gut microflora alterations associated with gut parasites and other pathogens that drive these alterations may help to promote the understanding of intestinal flora's role in multiple-infected individuals. This study examined the effects of dual infection with Eimeria tenella and subgroup J avian leukosis virus (ALV-J) on the chick cecal microbiome. Specific-pathogen-free (SPF) chicks were infected with either ALV-J strain NX0101 at 1 day of age or E. tenella at 14 days of age, another group was infected with both pathogens. Cecal contents from chicks were extracted at the 21 days of age and examined using 16S rRNA genes illumina sequencing. A genus-level opportunistic pathogen enrichment and a decrease in possible resident probiotics were observed in response to all infection groups. Of note, E. tenella mainly induced a sharp decrease in the richness and diversity of cecal microflora from infected chicks because of the serious E. tenella-induced damage to intestinal tissues. ALV-J infection led to structural changes and increased the richness and diversity of the cecal microflora. As for E. tenella and ALV-J dual infected chicks, a marked enrichment of opportunistic pathogens in addition to some other bacteria that may play a role involving cecal microbiota carbohydrate transport and metabolic functions were also found compared to single pathogen-infected chicks. Overall, this study provides valuable insights into the SPF chick cecal microbial community, the modulations of this community in response to different pathogenic infections of single or dual infections, and the interactions between different pathogens and hosts from the perspective of intestinal microflora.

Efficacy of a potential DNA vaccine encoding Cryptosporidium baileyi rhomboid protein against homologous challenge in chickens

The parasite Cryptosporidium baileyi can infect the larynx, trachea, bursa and cloaca of poultry, causing high mortality during severe infection and leading to substantial economic losses of the poultry industry. The rhomboid protein is very important in Cryptosporidium infection. In this study, a nucleic acid based vaccine candidate pEGFP-CbROM was constructed. After orally challenging with C. baileyi oocysts, the corresponding immune responses induced were analyzed and the immunoprotective effect evaluated in chickens. Obtained results revealed that this nucleic acid based vaccine could induce antibody responses and peripheral blood T lymphocytes proliferation significantly (P<0.05), while the peripheral blood B lymphocyte proliferation increased significantly (P<0.05) only at a high dose of 100μg of pEGFP-CbROM, compared with the PBS control group. After C. baileyi infection, the duration of oocysts shedding was shortened by 2days in the 100μg pEGFP-CbROM group, and the rate of reduction could reach to around 71.3%. While no significant difference in body weight gain was observed among the immunized groups (P>0.05), the differences between the immunized and the non-immunized groups were found to be significant (P<0.05). Our data provides a useful basis for further work in cryptosporidiosis prevention and treatment.

DNA vaccination of poultry: The current status in 2015

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Poultry DNA vaccination studies are regularly being published since 1993.

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These studies are mainly, but not only, concerned with vaccination against viruses.

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The different strategies of improving DNA vaccine efficacies are presented.

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The fate of the vaccine plasmid, immune properties and other applications are described.

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Despite the compiling preclinical reports, a poultry DNA vaccine is yet unavailable in the market.

DNA vaccination is a promising alternative strategy for developing new human and animal vaccines. The massive efforts made these past 25 years to increase the immunizing potential of this kind of vaccine are still ongoing. A relatively small number of studies concerning poultry have been published. Even though there is a need for new poultry vaccines, five parameters must nevertheless be taken into account for their development: the vaccine has to be very effective, safe, inexpensive, suitable for mass vaccination and able to induce immune responses in the presence of maternal antibodies (when appropriate). DNA vaccination should meet these requirements. This review describes studies in this field performed exclusively on birds (chickens, ducks and turkeys). No evaluations of avian DNA vaccine efficacy performed on mice as preliminary tests have been taken into consideration. The review first describes the state of the art for DNA vaccination in poultry: pathogens targeted, plasmids used and different routes of vaccine administration. Second, it presents strategies designed to improve DNA vaccine efficacy: influence of the route of administration, plasmid dose and age of birds on their first inoculation; increasing plasmid uptake by host cells; addition of immunomodulators; optimization of plasmid backbones and codon usage; association of vaccine antigens and finally, heterologous prime-boost regimens. The final part will indicate additional properties of DNA vaccines in poultry: fate of the plasmids upon inoculation, immunological considerations and the use of DNA vaccines for purposes other than preventing infectious diseases.

Protective efficacy in chickens of recombinant plasmid pET32a(+)-ADF-3-1E of Eimeria acervulina

This experiment was conducted to study the protective efficacy of recombinant plasmid pET32a(+)-ADF-3-1E in coccidian-infected breeding chickens. The 7-day-old chickens were randomly divided into five groups: a recombinant plasmid pET32a(+)-ADF-3-1E group, a pET32a(+)-ADF group, a pET32a(+)-3-1E group, a control group, and an infection control group. The chickens were immunized intramuscularly with recombinant plasmid DNA in a dose of 200 μg, respectively, and a booster vaccination was given at the same dosage 1 week later. The peripheral blood T lymphocyte proliferation, serum IgG antibody response, and levels of interleukin 2 (IL-2) and interferon gamma (IFN-γ) were detected, respectively. The chickens were inoculated with 4 × 10(6) Eimeria acervulina-sporulated oocysts (Baoding strain) on the seventh day after the last immunization to evaluate the protective efficiency of the recombinant plasmid DNA. The results showed that the lymphocyte proliferation, serum IgG antibody, and IL-2 and IFN-γ levels in recombinant plasmid DNA group were significantly higher than those in control group (P < 0.01). The lymphocyte proliferation, serum IgG antibody, and IL-2 and IFN-γ levels in pET32a(+)-ADF-3-1E group were significantly higher than those in pET32a(+)-3-1E group and pET32a(+)-ADF group, respectively (P < 0.05). It indicated that the pET32a(+)-ADF-3-1E could produce stronger immune responses. The relative body weight gain rate in pET32a(+)-ADF-3-1E group was 88.36 %, which was significantly higher than that in control group (P < 0.05) and infection control group (P < 0.01). The reductions of oocyst production and lesion scores in pET32a(+)-ADF-3-1E group were 67.88 and 67.13 %, respectively. The oocyst excretion and the lesion score of chickens in pET32a(+)-ADF-3-1E group were lower than those in infection control group, respectively. Anticoccidial index (ACI) value in group immunized with pET32a(+)-ADF-3-1E was 169.82. ACI value of 160-179 was considered as effective. These results demonstrated that the pET32a(+)-ADF-3-1E recombinant plasmid DNA could effectively improve the cellular responses and humoral immune responses of the chickens, and it might provide protection against coccidiosis in chickens.

Display of Eimeria tenella EtMic2 protein on the surface of Saccharomyces cerevisiae as a potential oral vaccine against chicken coccidiosis

S. cerevisiae is generally regarded as safe and benign organism and its surface display system may be used as a unique eukaryotic expression system that is suitable for expressing eukaryotic antigen. In addition to the convenience of vaccine delivery, the yeast cell wall has been shown to enhance the innate immunity when immunized with the yeast live oral vaccine. In the present study, we expressed the chicken coccidian E. tenella EtMic2, a microneme protein, on the surface of the S. cerevisiae and evaluated it as a potential oral vaccine for chicken against E. tenella challenge. The protective efficacy against a homologous challenge was evaluated by body weight gains, lesion scores and fecal oocyst shedding. The results showed that the live oral vaccine can improve weight gains, reduced cecal pathology and lower oocyst fecal shedding compared with non immunized controls. In addition, the yeast oral vaccine could stimulate humoral as well as cell mediate immune responses. These results suggested that EtMic2 displayed on the cell surface of S. cerevisiae could be used as potential live vaccine against chicken coccidiosis.

Effect of dinitolmide intercalated into Montmorillonite on E. tenella infection in chickens

To enhance the anti-coccidial effect of dinitolmide and reduce its residual, the dinitolmide/MMT compounds were synthesized by the method of solution intercalation via dinitolmide intercalated into Na + -montmorillonite (Na + -MMT). The structure of compounds was characterized by X-ray diffraction and Fourier transformed infrared. Its anti-coccidial effect was examined by Eimeria tenella infection experiment. One hundred fifty AA broiler chickens were divided into five groups. Chickens were orally inoculated with 5 × 10(4) E. tenella oocysts after dinitolmide was given. Their curative effects were observed. The results showed that intercalated dinitolmide expanded the basal spacing (d 001) of MMT from 12.6 to 15.2 Å. The IR bands of amide group in dinitolmide/MMT were detected at 1,533 cm(-1) which showed that dinitolmide was successfully intercalated into the interlayer spaces of MMT. The dinitolmide/MMT showed higher anti-coccidian oocyst activity compared with dinitolmide (p < 0.05). The dinitolmide/MMT compound can significantly increase body weight gains and reduce bloody diarrhea, lesion score, and oocyst excretion. The anti-coccidia index of dinitolmide/MMT group (165.21) is much higher than dinitolmide group (88.84). The dinitolmide/MMT hybrid systems can be more effective in control of coccidiosis in comparison to dinitolmide.

Eimeria maxima: efficacy of recombinant Mycobacterium bovis BCG expressing apical membrane antigen1 against homologous infection

Coccidiosis is one of the most important protozoan diseases and inflicts severe economic losses on the poultry industry. The aim of this study was to evaluate the capacity of Bacillus Calmette-Guerin (BCG) to deliver apical membrane antigen1 (AMA1) of Eimeria maxima to stimulate specific cellular and humoral immune responses in chickens. Day-old birds were immunized twice with rBCG/pMV261-AMA1, rBCG/pMV361-AMA1, or BCG via oral, intranasal, and subcutaneous routes and then orally challenged with homologous E. maxima sporulated oocysts. Gain of body weight, fecal oocyst output, lesion scores, serum antibody responses, numbers of splenocyte CD4(+) and CD8(+) T cells, and gut cytokine transcript levels were assessed as measures of protective immunity. Challenge experiments demonstrated that rBCG vaccination via intranasal or subcutaneous routes could increase weight gain, decrease intestinal lesions, and reduce fecal oocyst shedding, and the subcutaneous and intranasal routes were superior to the oral route based on the immune effects. Furthermore, intranasal rBCG immunization could also lead to a significant increase in serum antibody, the percentage of CD4+ and CD8+ T lymphocyte cells, and the levels of IL-1β, IFN-γ, IL-15, and IL-10 mRNAs compared with the control group. These results suggested that intranasal rBCG immunization could induce a strong humoral and cellular response directed against homologous E. maxima infection. This study provides data for the use of rBCG to develop a prophylactic vaccine against coccidiosis.

Partial protective of chickens against Eimeria tenella challenge with recombinant EtMIC-1 antigen

Eimeria tenella microneme protein 1 (EtMIC-1) is highly conserved with TgMIC-2, which is involved in parasite binding specifically to host cells. Little is known about the immune responses and protective efficacy against E. tenella infection with EtMIC-1 antigen. In the present study, the recombinant proteins of E. tenella mature MIC-1 and adhesive domain (von Willebrand factor type A domain, EtMIC-1-VD) were obtained, protective efficacy against E.tenella infection and the mucosal immune response, which is induced in broilers was evaluated. The antibody levels and the transcription profiles of cytokine of chickens, such as interleukin-12 (IL-12) and interferon-γ (IFN-γ), were detected after being immunized three times with the recombinant EtMIC-1 and EtMIC-1-VD by ELISA assay and quantitative real-time PCR, respectively. The results showed that both groups of chickens, after being immunized with 100 μg EtMIC-1 or EtMIC-1-VD antigen, induced about tenfold higher IgG levels compared to the nonimmune groups. The transcription profiles of IL-12 and IFN-γ of the immunized groups were significantly higher than the control groups as well. The anticoccidial index of the group immunized with 100 μg EtMIC-1 and the group immunized with 100 μg EtMIC-1-VD were 167.2 and 165.5, respectively, which are significantly higher than low-dose immunized groups and challenged control groups. Our data suggests that VD domain is the key functional structure of EtMIC-1 that could trigger a significant humoral and cellular response against E. tenella infection, and EtMIC-1 had the potential in imparting partial protection in chickens against homologous challenge.