In vivo effects of chicken interferon-gamma during infection with Eimeria

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.

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.

Simultaneous Expression of Chicken Granulocyte Monocyte Colony-Stimulating Factor and the Hemagglutinin-Neuraminidase Epitope of the Virulent Newcastle Disease Virus Genotype VII C22 Strain in a Functional Synthetic Recombinant Adenovirus as a Genotype-Matched Vaccine with Potential Antiviral Activity

When it comes to the prevention of clinical signs and mortality associated with infection of the Newcastle disease virus (NDV), vaccination has been very effective. However, recent evidence has proven that more highly virulent strains are emerging that bypass existing immune protection and pose a serious threat to the global poultry industry. Here, a novel rescued adenovirus 5-coexpressed chicken granulocyte monocyte colony-stimulating factor (ChGM-CSF) bio-adjuvant and C22-hemagglutinin-neuraminidase (HN) boosted chickens' immunological genetic resistance and thus improved the immunological effectiveness of the critical new-generation vaccine in vitro and in vivo. Accordingly, the hemagglutination inhibition (HI) titers (log2) of the recombinant adenovirus (rAdv)-ChGM-CSF-HN-immunized chickens had greater, more persistent, and longer-lasting NDV-specific antibodies than the La Sota and rAdv-HN-inoculated birds. Moreover, humoral and adaptive immunological conditions were shown to be in harmony after rAdv-ChGM-CSF-HN inoculation and uniformly enhanced the expression of alpha interferon (IFN-α), IFN-β, IFN-γ, interleukin-1β (IL-1β), IL-2, IL-16, IL-18, and IL-22. Postchallenge, the control challenge (CC), wild-type adenovirus (wtAdv), and rAdv-ChGM-CSF groups developed unique NDV clinical manifestations, significant viral shedding, high tissue viral loads, gross and microscopic lesions, and 100% mortality within 7 days. The La Sota, rAdv-HN, and rAdv-ChGM-CSF-HN groups were healthy and had 100% survival rates. The rAdv-ChGM-CSF-HN group swiftly regulated and stopped viral shedding and had lower tissue viral loads than all groups at 5 days postchallenge (dpc). Thus, the antiviral activity of ChGM-CSF offered robust immune protection in the face of challenge and reduced viral replication convincingly. Our advance innovation concepts, combining ChGM-CSF with a field-circulating strain epitope, could lead to the development of a safe, genotype-matched, universal transgenic vaccine that could eradicate the disease globally, reducing poverty and food insecurity. IMPORTANCE We studied the biological characterization of the developed functional synthetic recombinant adenoviruses, which showed a high degree of safety, thermostability, and genetic stability for up to 20 passages. It was demonstrated through both in vitro and in vivo testing that the immunogenicity of the proposed vaccine, which uses the T2A peptide from the Thosea asigna virus capsid protein supported by glycine and serine, helps with efficiency to generate a multicistronic vector, enables expression of two functional proteins in rAdv-ChGM-CSF-HN, and is superior to that of comparable vaccines. Additionally, adenovirus can be used to produce vaccines matching the virulent field-circulating strain epitope. Because there is no preexisting human adenoviral immunity detected in animals, the potency of adenoviral vaccines looks promising. Also, it ensures that the living vector does not carry the resistance gene that codes for the kanamycin antibiotic. Accordingly, a human recombinant adenoviral vaccine that has undergone biological improvements is beneficial and important.

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.

Coccidiosis: Recent Progress in Host Immunity and Alternatives to Antibiotic Strategies

Coccidiosis is an avian intestinal disease caused by several distinct species of Eimeria parasites that damage the host’s intestinal system, resulting in poor nutrition absorption, reduced growth, and often death. Increasing evidence from recent studies indicates that immune-based strategies such as the use of recombinant vaccines and various dietary immunomodulating feed additives can improve host defense against intracellular parasitism and reduce intestinal damage due to inflammatory responses induced by parasites. Therefore, a comprehensive understanding of the complex interactions between the host immune system, gut microbiota, enteroendocrine system, and parasites that contribute to the outcome of coccidiosis is necessary to develop logical strategies to control coccidiosis in the post-antibiotic era. Most important for vaccine development is the need to understand the protective role of the local intestinal immune response and the identification of various effector molecules which mediate anti-coccidial activity against intracellular parasites. This review summarizes the current understanding of the host immune response to coccidiosis in poultry and discusses various non-antibiotic strategies which are being developed for coccidiosis control. A better understanding of the basic immunobiology of pertinent host–parasite interactions in avian coccidiosis will facilitate the development of effective anti-Eimeria strategies to mitigate the negative effects of coccidiosis.

Em14-3-3 delivered by PLGA and chitosan nanoparticles conferred improved protection in chicken against Eimeria maxima

Eimeria maxima (E. maxima) are an intracellular apicomplexan protozoan that causes intestinal coccidiosis in chickens. The purpose of this research was to develop a novel delivery approach for recombinant E. maxima (rEm) 14-3-3 antigen to elicit enhanced immunogenic protection using poly (D, L-lactide-co-glycolide) (PLGA) and chitosan (CS) nanoparticles (NPs) against E. maxima challenge. The morphologies of prepared antigen-loaded NPs (PLGA/CS-rEm14-3-3 NPs) were visualized by a scanning electron microscope. The rEm14-3-3 and PLGA/CS-rEm14-3-3 NPs-immunized chicken-induced changes of serum cytokines, IgY-antibody level, and T-lymphocyte subsets and protective efficacies against E. maxima challenge were evaluated. The results revealed that encapsulated rEm14-3-3 in PLGA and CS NPs presented spherical morphology with a smooth surface. The chickens immunized with only rEm14-3-3 and PLGA/CS-rEm14-3-3 NPs elicited a significant (p<0.05) higher level of IFN-γ cytokine, stimulated the proportions of CD4⁺/CD3⁺, CD8⁺/CD3⁺ T-cells, and provoked sera IgY-antibody immune response compared to control groups (PBS, pET-32a, PLGA, and CS). Whereas, PLGA-rEm14-3-3 NP-immunized chicken provoked a higher level of IFN- γ production and IgY-antibody response rather than CS-rEm14-3-3 and bare antigen, relatively. The animal experiment results ratified that PLGA-rEm14-3-3 NP-immunized chicken significantly alleviated the relative body weight gain (%), decreased lesion score, and enhanced oocyst decrease ratio compared to CS-rEm14-3-3 NPs and only rEm14-3-3. The anti-coccidial index of the chicken vaccinated with the PLGA-rEm14-3-3 NPs was (180.1) higher than that of the Cs-rEm14-3-3 NPs (167.4) and bare antigen (165.9). Collectively, our statistics approved that PLGA NPs might be an efficient antigen carrier system (Em14-3-3) to act as a nanosubunit vaccine that can improve protective efficacies in chicken against E. maxima challenge.

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.

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

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

Effects of methylsulfonylmethane and neutralizing anti-IL-10 antibody supplementation during a mild Eimeria challenge infection in broiler chickens

A 28-day experiment was conducted in broilers to study the effects of feeding methylsulfonylmethane (MSM) and IL-10-neutralizing antibody from dried egg product (DEP) on the growth performance, immune responsivity, oxidative stress parameters, and gut health outcomes during a mild infection with mixed species of Eimeria. A total of 500 male Ross 308 chicks were allocated to five treatments: sham-inoculated (uninfected) chickens fed control diet (UCON), Eimeria-infected chickens fed control diet (ICON), and Eimeria-infected chickens fed control diet supplemented with 287 U/tonne of DEP (I-DEP), 0.4% MSM, or their combination (I-DEP-MSM), with 10 replicate cages of 10 birds per treatment. All infected groups received 1 mL of an oral inoculum containing Eimeria acervulina (10,000 oocysts), Eimeria maxima (5,000 oocysts), and Eimeria tenella (5,000 oocysts) on study days 7 and 14. Data were analyzed as a two-way ANOVA for all treatments including Eimeria-infected groups, in addition to a single degree of freedom contrast to compare uninfected and infected groups receiving the control diet. Mild Eimeria infection did not influence the growth performance in ICON compared with UCON at any time points. Overall (day 0-28) growth performance parameters were not influenced by either infection or dietary supplementation of MSM or DEP. However, birds in I-DEP-MSM showed improved ADG during study day 7 to 14 (i.e., 7 d after primary inoculation) indicating a beneficial effect immediately after Eimeria infection. Although MSM supplementation reduced thiobarbituric acid reactive substances (day 21 and 28), both MSM and DEP improved the total antioxidant capacity (day 21) in the plasma of infected birds. Histopathological outcomes were not influenced by treatments, and fecal oocyst output was higher in MSM- and DEP-supplemented groups than with ICON, indicating no beneficial effects. Similarly, expression of cecal inflammatory cytokines (IL-10, IL-1β, and interferon-γ) was not affected by MSM, DEP, or their combination. Overall, the current results suggest that both MSM and DEP supplementation may benefit birds during a mild Eimeria infection as indicated by improvements in ADG and oxidative stress outcomes.

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

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

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.

The Construction and Immunoadjuvant Activities of the Oral Interleukin-17B Expressed by Lactobacillus plantarum NC8 Strain in the Infectious Bronchitis Virus Vaccination of Chickens

Interleukin-17B (IL-17B) is a protective cytokine of the IL-17 family and plays an essential role in the regulation of mucosal inflammation. However, little is known about the role of IL-17B in the control of viral infections. In this study, a recombinant Lactobacillus plantarum, designated as NC8-ChIL17B, was constructed to express the chicken IL-17B (ChIL-17B) gene. The recombinant ChIL17B (rChIL17B) protein was about 14 kDa and was anchored to the surface of NC8 cells. In vitro, it was found that the rChIL17B protein inhibited the proliferation of the infectious bronchitis virus (IBV) through activation of nuclear factor kappa B (NF-κB) and the JAK (Janus kinase)-STAT (signal transducers and activators of transcription) signaling. Moreover, to evaluate the immunoadjuvant activities of NC8-ChIL17B, 40 three-day-old specific pathogen-free (SPF) chickens were divided into four groups. Three groups were orally vaccinated with fresh NC8, NC8-ChIL17B, and phosphate buffered saline (PBS), along with the infectious bronchitis virus vaccine, and the other group was the PBS-negative control. The results of the IBV-specific antibody titer and the concentration of the cytokines IL-2, IL-4, IL-6, and interferon gamma (IFN-γ) in sera, as well as the concentration of secretory immunoglobulin A (sIgA) in the tracheal and small intestinal mucosa, the number of cluster of differentiation 4 positive (CD4⁺) and cluster of differentiation 8 positive (CD8⁺) T cells in the blood, and the expression of immune-related genes all indicated that NC8-ChIL17B efficiently enhanced the humoral and cellular immune responses to IBV vaccine. Moreover, the viral loads in the NC8-ChIL17B- and IBV-vaccinated group were significantly lower than in the control groups, suggesting a significant promotion of the immunoprotection of IBV vaccination against the virulent IBV strain. Therefore, ChIL-17B is a promising, effective adjuvant candidate for chicken virus vaccines.

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

Dendritic cells (DCs) are key linkages between innate immunity and acquired immunity. The antigens that promote the functions of DCs might be the effective candidates of novel vaccine. In this research, the ability of ubiquitin-conjugating enzyme (UCE), a recognized common antigens among chicken Eimeria species, to stimulate DCs of chickens were evaluated. We cloned UCE gene from Eimeria maxima (EmUCE), and its protein expression was confirmed by SDS-PAGE and western-blot. Immunofluorescence assay confirmed the binding of rEmUCE on the surface of chicken splenic-derived DCs (ChSP-DCs). Flow cytometric analysis showed that rEmUCE-treated ChSP-DCs increased MHCII, CD1.1, CD11c, CD80, and CD86 phenotypes. qRT-PCR indicated that transcript levels of maturation markers CCL5, CCR7, and CD83 in ChSP-DCs were upregulated in response to rEmUCE. Following rEmUCE treatment, chSP-DCs activated TLR signaling and inhibited Wnt signaling. Moreover, rEmUCE promoted DC-mediated T-cell proliferation in DC/T-cell co-incubation. Interestingly, CD3⁺/CD4⁺ T-cells were significantly enhanced when rEmUCE-treated chSP-DCs were co-incubated with T-cells. Cytokine secretion pattern of rEmUCE-stimulated ChSP-DCs revealed that the production of IL-12 and IFN-γ was increased whereas IL-10 and TGF-β were unchanged. Likewise, the co-incubation of ChSP-DCs with T-cells indicated increased production of IFN-γ but not IL-4. Collectively, rEmUCE could polarize DCs to immunogenic phenotype and shift the immune cells towards Th1 response. Our observations provide valuable insight for future research aimed at vaccine development against avian coccidiosis.

Effect of TLR agonist on infections bronchitis virus replication and cytokine expression in embryonated chicken eggs

Avian infectious bronchitis (IB) is an acute, highly infectious and contagious viral disease of chickens caused by avian infectious bronchitis virus (IBV) belonging to the genus Coronavirus and family Coronaviridae. It can affect all age groups of birds. The toll-like receptors (TLRs) are a major class of innate immune pattern recognition receptors that have a key role in immune response and defense against various infections.The TLRs are essential for initiation of innate immune responses and in the development of adaptive immune responses. An in ovo model was employed to study the antiviral activity of TLR ligands (Pam3CSK4, LPS and CpG ODN) on replication of IBV. It was hypothesized that optimum dose and specific timing of TLR ligands may reduce viral load of IBV in specific pathogen free (SPF) embryonated chicken eggs (ECEs). Further, the mechanism involved in the TLR-mediated antiviral response in chorioallantoic membrane (CAM) of ECEs was investigated. The ECEs of 9-11 days old were treated with different doses (high, intermediate and low) of TLR-2 (Pam3CSK4), TLR-4 (LPS) and TLR-21 (CpG ODN) ligands. In addition, to know the timing of TLR ligand treatment, six time intervals were analyzed viz. 36, 24 and 12 h prior to infection, time of infection (co-administration of TLR ligands and avian IBV) and 12 and 24 h post-IBV infection. For studying the relative expression of immuno-stimulatory genes (IFN-α, IFN-β, IFN-γ, IL-1β, iNOS and OAS) in CAM, TLR ligands were administered through intra-allantoicroute and CAM were collected at 4, 8 and 16 h post treatment. The results demonstrated that intermediate dose of all the three TLR ligands significantly reduced virus titers and used in the present study. However, the LPS reduced virus titer pre- and post-IBV infection but Pam3CSK4 and CpG ODN reduced only pre-IBV infection. Further analysis showed that TLR ligands induced IFN-γ, IL-1β and IFN stimulated genes viz. iNOS and OAS genes in CAM. The present study pointed towards the novel opportunities for rational design of LPS as immuno-stimulatory agent in chickens with reference to IBV. It may be speculated that in ovo administration of these TLR ligands may enhance resistance against viral infection in neonatal chicken and may contribute towards the development of more effective and safer vaccines including in ovo vaccines.

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.

Oral inoculation of ultraviolet-irradiated Eimeria species oocysts protects chickens against coccidiosis

Prevention of coccidiosis is one of the best ways of controlling disease. Therefore, the present study was carried out to evaluate the protective effect of ultraviolet (UV)-irradiated sporulated oocysts of Eimeria species against coccidiosis in layer chickens. One hundred forty-four one-day-old layer chicks were randomly divided into 4 groups (n = 36), including non-immunized/non-challenged negative control group (NC group), non-immunized/challenged control group (NIC group), non-irradiated sporulated oocyst/challenged group (CA group), and UV-irradiated sporulated oocyst/challenged (UV group). At the age of 4 days, chickens in groups UV and CA were both orally inoculated with 1.0 × 10⁴ UV-irradiated and non-irradiated sporulated oocysts of Eimeria species, respectively. Chickens in groups NIC and NC were served as positive and negative controls, respectively. Chickens in all groups were orally challenged with 7.5 × 10⁴ sporulated oocysts of Eimeria species except the NC group at the age of 21 days. The results revealed that chicks receiving UV-irradiated sporulated oocysts had no signs of illness with minimal or no changes in the cecal integrity and a significantly lower oocyst shedding (OPG) than in the NIC group. Additionally, the cytokine gene expression profiles were evaluated. Expression levels of IL-2, IL-12, and IFN-γ were significantly higher in the spleen of chicks in the UV and CA groups than in the NC group post-challenge. As expected, treatment with irradiated oocysts resulted in a significant reduction in oocyst shedding and maintenance of cecal mucosal integrity. Furthermore, the body weight was higher in chickens inoculated with UV-irradiated oocysts than their non-irradiated counterparts. In conclusion, our results demonstrate that inoculation with UV-irradiated sporulated oocysts of Eimeria species can produce a substantial reduction in infection symptoms.

Protective potential of diclazuril-treated oocysts against coccidiosis in layer chicks

Diclazuril, which is widely used for the prevention of coccidiosis in chickens, has a lethal effect on asexual and sexual stages of Eimeria spp. However, little is known about its effect on the exogenous stages of Eimeria spp. In this study, we evaluated the effect of in vitro treatment with 0.2% diclazuril on unsporulated and sporulated oocysts of Eimeria spp. For this purpose, a total of 180 male layer chicks aged one day were randomly divided into 5 experimental groups. Each group was divided into 3 replicates of 12 chicks each. Group 1 (G1) and Group 2 (G2) were negative (non-immunized and non-challenged) and positive (non-immunized and challenged) controls, respectively. Group 3 (G3) was immunized per os with 1.0 × 10⁴ non-diclazuril treated-sporulated oocysts. Groups 4 (G4) was immunized per os with 0.2% diclazuril treated-unsporulated oocysts (1.0 × 10⁴) in which diclazzuril didn't affect sporulation. Group 5 (G5) was immunized per os with 0.2% diclazuril treated-sporulated oocysts (1.0 × 10⁴). Chicks of G2, G3, G4, and G5 were challenged with 7.5 × 10⁴ untreated sporulated oocysts at the age of 21 days, while the group 1 chicks remained unchallenged. G4 and G5 animals immunized with 0.2% diclazuril-treated oocysts showed a significant decrease in bloody diarrhea severity, lesion scores, and oocyst counts in comparison to those immunized with untreated oocysts. Furthermore, histopathologic findings showed a low number of parasitic stages in cecal tissues in G4 and G5. A significant increased body weight gain was observed in Gs 4 and 5 in comparison to G2. In addition, expression levels of IL-2, IL-12, and IFN-γ were significantly increased in G4 and G5. In conclusion, diclazuril is effective in attenuating Eimeria oocysts and thus provides an alternative approach for using diclazuril-treated oocysts to protect chicks against Eimeria challenge.

A Functional Food Mixture "Protector" Reinforces the Protective Immune Parameters against Viral Flu Infection in Mice

Background: Viral influenza infection causes serious health issues especially when an outbreak occurs. Although influenza virus vaccines are available and each year manufactures modify the vaccine depending on the expected mutated strain, it is still far from satisfactory, mainly in young children and older adults. Therefore, a product that can support and shape the immune system to protect against viral flu infections is highly essential. Methods: A functional food water-soluble mixture of pomegranate, red grape, dates, olive fruit, figs, and ginger extracts, termed herein “Protector”, was prepared and tested in stimulating/modulating the production of specific cytokines, and hemagglutinin inhibition (HAI) antibodies following viral flu vaccination in mice. Results: A single intraperitoneal or multiple oral administration for 1–7 days of “Protector” significantly increased the production of interferon (IFN)-γ and interleukin (IL)-12 in blood, spleen, and lungs of mice. When “Protector” was orally administered for one week following a single vaccine injection (primary immunization) or for two weeks (one week apart) following double vaccine injections (secondary immunization), mice significantly produced higher titers of HAI antibodies. This increase in HAI antibodies was associated with Pillow-inducing significant and different changes in vaccine-induced IFN-γ, IL-12, IL-6 and IL-22 following primary and secondary immunizations. Conclusions: “Protector” administration reinforces the protective immune parameters against viral flu infection. Therefore, after performing preclinical toxicology studies and ensuring its safety, “Protector” should be considered a potential product to be tested in clinical trials to conclude its efficacy in reducing the devastating effects of flu infection in humans and its outbreaks.

Molecular characterisation and the protective immunity evaluation of Eimeria maxima surface antigen gene

BACKGROUND

Coccidiosis is recognised as a major parasitic disease in chickens. Eimeria maxima is considered as a highly immunoprotective species within the Eimeria spp. family that infects chickens. In the present research, the surface antigen gene of E. maxima (EmSAG) was cloned, and the ability of EmSAG to stimulate protection against E. maxima was evaluated.

METHODS

Prokaryotic and eukaryotic plasmids expressing EmSAG were constructed. The EmSAG transcription and expression in vivo was performed based on the RT-PCR and immunoblot analysis. The expression of EmSAG in sporozoites and merozoites was detected through immunofluorescence analyses. The immune protection was assessed based on challenge experiments. Flow cytometry assays were used to determine the T cell subpopulations. The serum antibody and cytokine levels were evaluated by ELISA.

RESULTS

The open reading frame (ORF) of EmSAG gene contained 645 bp encoding 214 amino acid residues. The immunoblot and RT-PCR analyses indicated that the EmSAG gene were transcribed and expressed in vivo. The EmSAG proteins were expressed in sporozoite and merozoite stages of E. maxima by the immunofluorescence assay. Challenge experiments showed that both pVAX1-SAG and the recombinant EmSAG (rEmSAG) proteins were successful in alleviating jejunal lesions, decreasing loss of body weight and the oocyst ratio. Additionally, these experiments possessed anticoccidial indices (ACI) of more than 170. Higher percentages of CD4⁺ and CD8⁺ T cells were detected in both EmSAG-inoculated birds than those of the negative control groups (P < 0.05). The EmSAG-specific antibody concentrations of both the rEmSAG and pVAX1-EmSAG groups were much higher than those of the negative controls (P < 0.05). Higher concentrations of IL-4, IFN-γ, TGF-β1 and IL-17 were observed more in both the rEmSAG protein and pVAX1-SAG inoculated groups than those of negative controls (P < 0.05).

CONCLUSIONS

Our findings suggest that EmSAG is capable of eliciting a moderate immune protection and could be used as an effective vaccine candidate against E. maxima.

Allocation of Interferon Gamma mRNA Positive Cells in Caecum Hallmarks a Protective Trait Against Histomonosis

Histomonosis is a parasitic disease of gallinaceous birds characterized by necrotic lesions in cacum and liver that usually turns fatal in turkeys while it is less severe in chickens. Vaccination using in vitro attenuated Histomonas meleagridis has been experimentally shown to confer protection against histomonosis. The protective mechanisms that underpin the vaccine-induced immune response are not resolved so far. Therefore, the actual study aimed to evaluate the location and quantitative distribution patterns of signature cytokines of type 1 [interferon gamma (IFN-γ)] or type 2 [interleukin (IL)-13] immune responses in vaccinated or infected hosts. An intergroup and interspecies difference in the spatial and temporal distribution patterns of cytokine mRNA positive cells was evident. Quantification of cells showed a significantly decreased percentage of IFN-γ mRNA positive cells at 4 days post-inoculation (DPI) in caeca of turkeys inoculated exclusively with the attenuated or the virulent inocula, compared to control birds. The decrement was followed by a surge of cells expressing mRNA for IFN-γ or IL-13, reaching a peak of increment at 10 DPI. By contrast, turkeys challenged following vaccination showed a slight increment of cecal IFN-γ mRNA positive cells at 4 DPI after which positive cell counts became comparable to control birds. The increase in infected birds was accompanied by an extensive distribution of positively stained cells up to the muscularis layer of cecal tissue whereas the vaccine group maintained an intact mucosal structure. In chickens, the level of changes of positive cells was generally lower compared to turkeys. However, control chickens were found with a higher percentage of IFN-γ mRNA positive cells in cecum compared to their turkey counterparts indicating a higher resistance to histomonosis, similar to the observation in immunized turkeys. In chickens, it could be shown that the changes of cytokine-positive cells were related to variations of mononuclear cells quantified by immunofluorescence. Furthermore, gene expression measured by reverse transcription quantitative real time PCR confirmed variations in organs between the different groups of both bird species. Overall, it can be concluded that a proportionally increased, yet controlled, allocation of IFN-γ mRNA positive cells in caeca hallmarks a protective trait against histomonosis.

RNA sequencing demonstrates large-scale temporal dysregulation of gene expression in stimulated macrophages derived from MHC-defined chicken haplotypes

Discovering genetic biomarkers associated with disease resistance and enhanced immunity is critical to developing advanced strategies for controlling viral and bacterial infections in different species. Macrophages, important cells of innate immunity, are directly involved in cellular interactions with pathogens, the release of cytokines activating other immune cells and antigen presentation to cells of the adaptive immune response. IFNγ is a potent activator of macrophages and increased production has been associated with disease resistance in several species. This study characterizes the molecular basis for dramatically different nitric oxide production and immune function between the B2 and the B19 haplotype chicken macrophages.A large-scale RNA sequencing approach was employed to sequence the RNA of purified macrophages from each haplotype group (B2 vs. B19) during differentiation and after stimulation. Our results demonstrate that a large number of genes exhibit divergent expression between B2 and B19 haplotype cells both prior and after stimulation. These differences in gene expression appear to be regulated by complex epigenetic mechanisms that need further investigation.

Protective Efficacy of Coccidial Common Antigen Glyceraldehyde 3-Phosphate Dehydrogenase (GAPDH) against Challenge with Three Eimeria Species

Coccidiosis is an intestinal disorder of poultry and often caused by simultaneous infections of several Eimeria species. GAPDH is one of the immunogenic common antigens among Eimeria tenella, E. acervulina, and E. maxima identified in our previous study. The present study was performed to further evaluate its immunogenicity and protective efficacy. The genes of GAPDH cloned from E. acervulina and E. maxima were named as EaGAPDH and EmGAPDH, respectively. The immunogenicity of recombinant proteins of EaGAPDH and EmGAPDH were analyzed by Western blot. The transcription and expression of pVAX-EaGAPDH and pVAX-EmGAPDH in the injected muscles were detected by reverse transcription PCR (RT-PCR) and Western blot, respectively. GAPDH-induced changes of T lymphocytes subpopulation, cytokines production, and antibody were determined using flow cytometry, quantitative real-time PCR (qPCR), and ELISA, respectively. Finally, the protective efficacies of pVAX-EaGAPDH and pVAX-EmGAPDH were evaluated by vaccination and challenge experiments. The results revealed that the recombinant GAPDH proteins reacted with the corresponding chicken antisera. The EaGAPDH genes were successfully transcribed and expressed in the injected muscles. Vaccination with pVAX-EaGAPDH and pVAX-EmGAPDH significantly increased the proportion of CD4⁺ and CD8⁺ T lymphocytes, the cytokines productions of IFN-γ, IL-2, IL-4 et al., and IgG antibody levels compared to controls. The vaccination increased the weight gains, decreased the oocyst outputs, alleviate the enteric lesions compared to controls, and induced moderate anti-coccidial index (ACI). In conclusion, the coccidial common antigen of GAPDH induced significant humoral and cellular immune response and effective protection against E. tenella, E. acervulina, E. maxima, and mixed infection of the three Eimeria species.

Trends in recombinant protein use in animal production

Recombinant technologies have made possible the production of a broad catalogue of proteins of interest, including those used for animal production. The most widely studied proteins for the animal sector are those with an important role in reproduction, feed efficiency, and health. Nowadays, mammalian cells and fungi are the preferred choice for recombinant production of hormones for reproductive purposes and fibrolytic enzymes to enhance animal performance, respectively. However, the development of low-cost products is a priority, particularly in livestock. The study of cell factories such as yeast and bacteria has notably increased in the last decades to make the new developed reproductive hormones and fibrolytic enzymes a real alternative to the marketed ones. Important efforts have also been invested to developing new recombinant strategies for prevention and therapy, including passive immunization and modulation of the immune system. This offers the possibility to reduce the use of antibiotics by controlling physiological processes and improve the efficacy of preventing infections. Thus, nowadays different recombinant fibrolytic enzymes, hormones, and therapeutic molecules with optimized properties have been successfully produced through cost-effective processes using microbial cell factories. However, despite the important achievements for reducing protein production expenses, alternative strategies to further reduce these costs are still required. In this context, it is necessary to make a giant leap towards the use of novel strategies, such as nanotechnology, that combined with recombinant technology would make recombinant molecules affordable for animal industry.

Impact of Enteric Health and Mucosal Permeability on Skeletal Health and Lameness in Poultry

Intestinal barrier leakage and/or altered gut microbial composition has been shown to markedly impact both osteoblast and osteoclast activities, systemically through circulation of gut immune cells and cytokines and locally by causing inflammation of extraintestinal organs such as the liver and bone marrow. Mild cases of heightened intestinal inflammation can cause bone loss in male mice in the absence of any overt nutritional deficiencies or weight loss, which has also been shown in chickens that have been infected with Salmonella. For poultry, ingredients selected for feed formulation have also a significant impact on gut health, intestinal microbiota, bone quality, and performance parameters. Consumption of diets with a high content of soluble non-starch polysaccharides (NSP) can affect bone quality parameters by reducing the amount of conjugated bile acids in the intestine, therefore diminishing the absorption of fat-soluble vitamins such as vitamin D and minerals like calcium and phosphorus. Recent enteric inflammation studies have shown that high NSP-containing diets have effects on intestinal viscosity, bone mineral content, and breaking strength, along with increased fluorescein isothiocyanate-dextran (FITC-d) leakage. Other skeletal diseases, such as bacterial chondronecrosis with osteomyelitis and enterococcal spondylitis, have a microbial component that is associated with increased mucosal permeability of the gut. Probiotics targeted toward control of enteric inflammation, either created through infectious disease or poor diet, may serve as a strategy for control of predisposing factors that lead to bone disorders.

Pre-immune state induced by chicken interferon gamma inhibits the replication of H1N1 human and H9N2 avian influenza viruses in chicken embryo fibroblasts

Background

Interferon gamma (IFN-γ), an immunoregulatory cytokine, is known to control many microbial infections. In a previous study, chicken interferon gamma (chIFN-γ) was found to be up-regulated following avian influenza virus (AIV) infection in specific pathogen-free chickens. We aimed to investigate whether the pre-immune state induced by chIFN-γ could generate an antiviral response against influenza virus.

Methods

We generated a chIFN-γ-expressing plasmid and transfected it into chicken embryo fibroblasts (CEFs) and then infected the cells with human origin H1N1 or avian origin H9N2 influenza viruses. Viral titers of culture medium were evaluated in MDCK cell and the viral RNA and IFN-stimulated genes (ISGs) were then quantified by real-time reverse transcriptase polymerase. To further evaluate the role of the antiviral effect of chIFN-γ by using a backward approach, synthetic small interfering RNAs (siRNA) targeting chIFN-γ were used to suppress chIFN-γ.

Results

The chIFN-γ-stimulated CEFs inhibited the replication of viral RNA (vRNA) and showed a mild decrease in the infectious virus load released in the culture medium. Compared to the mock-transfected control, the messenger RNA (mRNA) levels of type I IFNs and IFN-stimulated genes were up-regulated in the cells expressing chIFN-γ. After treatment with the siRNA, we detected a higher expression of viral genes than that observed in the mock-transfected control.

Conclusions

Our results suggest that apart from the important role played by chIFN-γ in the antiviral state generated against influenza virus infection, the pre-immune state induced by chIFN-γ can be helpful in mitigating the propagation of influenza virus.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-016-0527-1) contains supplementary material, which is available to authorized users.

Identification and immunogenicity of microneme protein 2 (EbMIC2) of Eimeria brunetti

There have been only a few antigen genes of Eimeria brunetti reported up to now. In this study, the gene encoding the microneme protein 2 (EbMIC2) was isolated from oocysts of E. brunetti by RT-PCR and the immunogenicity of recombinant EbMIC2 was observed. The EbMIC2 was cloned into vector pMD19-T for sequencing. The sequence was compared with the published EbMIC2 gene from GenBank revealed homology of the nucleotide sequence and amino acids sequence were 99.43 and 98.63%, respectively. The correct recombinant pMD-EbMIC2 plasmid was inserted into the pET-28a (+) expressing vector and transformed into competent Escherichia coli BL21 cells for expression. The expressed product was analyzed using SDS-PAGE and Western-blot. The results indicated that the recombinant EbMIC2 protein was recognized strongly by serum from naturally infected chicken with E. brunetti. Rat rcEbMIC2 antisera bound to bands of about 36 kDa in the somatic extract of E. brunetti sporozoites. The recombinant plasmid pVAX1-EbMIC2 was constructed and then the efficacies of recombinant plasmid and recombinant protein were evaluated. The results of IgG antibody level and cytokines concentration suggested that recombinant EbMIC2 could increase the IgG antibody level and induce the expressions of cytokines. Animal challenge experiments demonstrated that the recombinant EbMIC2 protein and recombinant plasmid pVAX1-EbMIC2 could significantly increase the average body weight gains, decrease the mean lesion scores and the oocyst outputs of the immunized chickens and presented high anti-coccidial index. All results suggested that EbMIC2 could become an effective candidate for the development of new vaccine against E. brunetti infection.

Eimeria maxima microneme protein 2 delivered as DNA vaccine and recombinant protein induces immunity against experimental homogenous challenge

E. maxima is one of the seven species of Eimeria that infects chicken. Until now, only a few antigenic genes of E. maxima have been reported. In the present study, the immune protective effects against E. maxima challenge of recombinant protein and DNA vaccine encoding EmMIC2 were evaluated. Two-week-old chickens were randomly divided into five groups. The experimental group of chickens was immunized with 100 μg DNA vaccine pVAX1-MIC2 or 200 μg rEmMIC2 protein while the control group of chickens was injected with pVAX1 plasmid or sterile PBS. The results showed that the anti-EmMIC2 antibody titers of both rEmMIC2 protein and pVAX1-MIC2 groups were significantly higher as compared to PBS and pVAX1 control (P<0.05). The splenocytes from both vaccinated groups of chickens displayed significantly greater proliferation compared with the controls (P<0.05). Serum from chickens immunized with pVAX1-MIC2 and rEmMIC2 protein displayed significantly high levels of IL-2, IFN-γ, IL-10, IL-17, TGF-β and IL-4 (P<0.05) compared to those of negative controls. The challenge experiment results showed that both the recombinant protein and the DNA vaccine could obviously alleviate jejunum lesions, body weight loss, increase oocyst, decrease ratio and provide ACIs of more than 165. All the above results suggested that immunization with EmMIC2 was effective in imparting partial protection against E. maxima challenge and it could be an effective antigen candidate for the development of new vaccines against E. maxima.

Efficacy of chimeric DNA vaccines encoding Eimeria tenella 5401 and chicken IFN-γ or IL-2 against coccidiosis in chickens

Chimeric DNA vaccines encoding Eimeria tenella (E. tenella) surface antigen 5401 were constructed and their efficacies against E. tenella challenge were studied. The open reading frame (ORF) of 5401 was cloned into the prokaryotic expression vector pGEX-4T2 to express the recombinant protein and the expressed recombinant protein was identified by Western blot. The ORF of 5401 and chicken cytokine gene IFN-γ or IL-2 were cloned into the eukaryotic expression vector pVAX1 consecutively to construct DNA vaccines pVAX-5401-IFN-γ, pVAX-5401-IL-2 and pVAX-5401. The expression of aim genes in vivo was detected by reverse transcription-polymerase chain reaction and Western blot. Fourteen-day-old chickens were inoculated twice at an interval of 7 days with 100 µg of plasmids pVAX-5401, pVAX-5401-IFN-γ and pVAX-5401-IL-2 or 200 µg of recombinant 5401 protein by leg intramuscular injection, respectively. Seven days after the second inoculation, all chickens except the unchallenged control group were challenged orally with 5 × 10(4) sporulated oocysts of E. tenella. Seven days after challenge, all chickens were weighted and slaughtered to determine the effects of immunization. The results showed the recombinant protein was about 90 kDa and reacted with antiserum against soluble sporozoites. The animal experiment showed that all the DNA vaccines pVAX-5401, pVAX-5401-IFN-γ or pVAX-5401-IL-2 and the recombinant 5401 protein could obviously alleviate body weight loss and cecal lesions as compared with non-vaccinated challenged control and empty vector pVAX1control. Furthermore, pVAX-5401-IFN-γ or pVAX-5401-IL-2 induced anti-coccidial index (ACI) of 180.01 or 177.24 which were significantly higher than that of pVAX-5401. The results suggested that 5401 was an effective candidate antigen for vaccine. This finding also suggested that chicken IFN-γ or IL-2 could effectively improve the efficacies of DNA vaccines against avian coccidiosis.

Identification of differentially expressed genes that potentially confer pest resistance in transgenic ChIFN-γ tobacco

Chicken interferon-γ (ChIFN-γ) is both an inhibitor of viral replication and a regulator of numerous immunological functions. However, since little is known about the mechanisms underlying the insect-resistance of transgenic ChIFN-γ, a transgenic ChIFN-γ tobacco line was employed in the present study to explore this mechanism. A cDNA microarray (with 43,760 unigenes) was used to analyze the gene expression profiles of transgenic and wild-type (WT) tobacco leaves at two different growth stages. Compared with the WT, 1529 and 405 expressed sequence tags were significantly up- or downregulated on days 119 and 147, respectively. The differentially expressed genes (DEGs) are involved in metabolic regulation, cell division and differentiation, material synthesis and transport, signal transduction, and protein synthesis and degradation. Candidate genes that may increase cell density, thicken cell walls, promote secondary metabolite synthesis, and mediate plant hormone-induced resistance responses were used to identify the ChIFN-γ-mediated insect-resistance mechanisms. The insect-resistance of transgenic ChIFN-γ tobacco possibly involves unknown signaling pathways, which may directly or indirectly affect DEG expression-mediating genes. The degree of pest resistance increased as the plants grew. Three genes likely to be related to jasmonic acid- or salicylic acid-dependent plant defense responses, including CAF 1, Cop 8/CSN, and HD, are implicated in the insect-resistance of the transgenic plants. The mechanism of transgenic ChIFN-γ tobacco resistance also involves RPS20 and other genes that induce microRNA-based gene regulation. The ChIFN-γ-mediated DGEs contribute to insect-resistance in transgenic ChIFN-γ tobacco, which provides new insight into the role of ChIFN-γ.

Sulfated glucan can improve the immune efficacy of Newcastle disease vaccine in chicken

To evaluate the immune effect of sulfated glucan from saccharomyces cerevisiae (SGSC) on chickens, two experiments were researched. In vitro experiment, the effects of SGSC on chicken splenic lymphocyte proliferation were determined. The results displayed that SGSC could significantly stimulate chicken splenic lymphocyte proliferation. In vivo experiment, 200 14-day-old chickens were averagely divided into 5 groups. The chickens, except blank control (BC) group, were vaccinated with Newcastle disease (ND) vaccine, repeated vaccination at 28 days old. At the same time of the first vaccination, the chickens in three SGSC groups were injected, respectively, with the SGSC at low, medium and high concentrations, in vaccination control (VC) and BC group, with equal volume of physiological saline, once a day for three successive days. On days 7, 14, 21, 28, 35 and 42 after the first vaccination, the lymphocyte proliferation, serum antibody titer and interleukin-2 (IL-2) and interferon-gamma (IFN-γ) were measured. The results showed that SGSC at suitable dose could significantly promote lymphocyte proliferation, enhance serum antibody titer, and improve serum IL-2 and IFN-γ concentrations. It indicated that SGSC could significantly improve the immune efficacy of Newcastle disease vaccine, and would be as the candidate of a new-type immune adjuvant.

Analysis of humoral immune response and cytokines in chickens vaccinated with Eimeria brunetti apical membrane antigen-1 (EbAMA1) DNA vaccine

This study aimed to determine the changes of cytokines, specific serum IgG and several parameters in chickens vaccinated with DNA vaccine encoding Eimeria brunetti apical membrane antigen-1 (EbAMA1) antigen. Two-week-old chickens were divided into five groups (four groups for experiment) randomly. Experimental groups of chickens were immunized with DNA vaccine while control group of chickens were injected with pVAX1 plasmid alone or TE buffer solution. All immunizations were boosted 2 weeks later. The EbAMA1 specific IgG antibody responses were measured at weeks 1-6 post-second immunizations and several parameters were also identified. The result showed that the antibody titers in chickens vaccinated with DNA vaccines were significantly different from those of the control groups 1 week after the second immunization and reached the maximum values 3 weeks post-second immunization. IFN-γ concentration was increased the highest level against EbAMA1 of all chickens vaccinated with vaccines up to 56-fold, follow by the specific IgG antibody levels were increased 10-17-fold compared with those of TE solution and plasmid (pVAX1) control chickens 1-6 weeks post-second immunization. In case of the levels of IL-10 and IL-17 was increased in experimental chickens with 4-5-fold. Even though it was statistically significant, TGF-β and IL-4 levels were higher in vaccinated than unvaccinated chickens. The results suggested that DNA vaccines encoding E. brunetti apical membrane antigen-1 (EbAMA1) could increase serum specific IgG antibody and cytokines concentration and could give protection against E. brunetti infection.

QTL detection for coccidiosis (Eimeria tenella) resistance in a Fayoumi × Leghorn F₂ cross, using a medium-density SNP panel

BACKGROUND

Coccidiosis is a major parasitic disease that causes huge economic losses to the poultry industry. Its pathogenicity leads to depression of body weight gain, lesions and, in the most serious cases, death in affected animals. Genetic variability for resistance to coccidiosis in the chicken has been demonstrated and if this natural resistance could be exploited, it would reduce the costs of the disease. Previously, a design to characterize the genetic regulation of Eimeria tenella resistance was set up in a Fayoumi × Leghorn F2 cross. The 860 F2 animals of this design were phenotyped for weight gain, plasma coloration, hematocrit level, intestinal lesion score and body temperature. In the work reported here, the 860 animals were genotyped for a panel of 1393 (157 microsatellites and 1236 single nucleotide polymorphism (SNP) markers that cover the sequenced genome (i.e. the 28 first autosomes and the Z chromosome). In addition, with the aim of finding an index capable of explaining a large amount of the variance associated with resistance to coccidiosis, a composite factor was derived by combining the variables of all these traits in a single variable. QTL detection was performed by linkage analysis using GridQTL and QTLMap. Single and multi-QTL models were applied.

RESULTS

Thirty-one QTL were identified i.e. 27 with the single-QTL model and four with the multi-QTL model and the average confidence interval was 5.9 cM. Only a few QTL were common with the previous study that used the same design but focused on the 260 more extreme animals that were genotyped with the 157 microsatellites only. Major differences were also found between results obtained with QTLMap and GridQTL.

CONCLUSIONS

The medium-density SNP panel made it possible to genotype new regions of the chicken genome (including micro-chromosomes) that were involved in the genetic control of the traits investigated. This study also highlights the strong variations in QTL detection between different models and marker densities.

Poultry coccidiosis: recent advancements in control measures and vaccine development

Coccidiosis is recognized as the major parasitic disease of poultry and is caused by the apicomplexan protozoan Eimeria. Coccidiosis seriously impairs the growth and feed utilization of infected animals resulting in loss of productivity. Conventional disease control strategies rely heavily on chemoprophylaxis and, to a certain extent, live vaccines. Combined, these factors inflict tremendous economic losses to the world poultry industry in excess of USD 3 billion annually. Increasing regulations and bans on the use of anticoccidial drugs coupled with the associated costs in developing new drugs and live vaccines increases the need for the development of novel approaches and alternative control strategies for coccidiosis. This paper aims to review the current progress in understanding the host immune response to Eimeria and discuss current and potential strategies being developed for coccidiosis control in poultry.

The chicken TH1 response: potential therapeutic applications of ChIFN-γ

The outcomes of viral infections are costly in terms of human and animal health and welfare worldwide. The observed increase in the virulence of some viruses and failure of many vaccines to stop these infections has lead to the apparent need to develop new anti-viral strategies. One approach to dealing with viral infection may be to employ the therapeutic administration of recombinant cytokines to act as 'immune boosters' to assist in augmenting the host response to virus. With this in mind, a greater understanding of the immune response, particularly cell mediated T-helper-1 (TH1) type responses, is imperative to the development of new anti-viral and vaccination strategies. Following the release of the chicken genome, a number of TH1-type cytokines have been identified, including chicken interleukin-12 (ChIL-12), ChIL-18 and interferon-γ ChIFN-γ), highlighting the nature of the TH1-type response in this non-mammalian vertebrate. To date a detailed analysis of the in vivo biological function of these cytokines has been somewhat hampered by access to large scale production techniques. This review describes the role of TH-1 cytokines in immune responses to viruses and explores their potential use in enhancing anti-viral treatment strategies in chickens. Furthermore, this review focuses on the example of ChIFN-γ treatment of Chicken Anemia Virus (CAV) infection. CAV causes amongst other things thymocyte depletion and thymus atrophy, as well as immunosuppression in chickens. However, due to vaccination, clinical disease appears less often, nevertheless, the subclinical form of the disease is often associated with secondary complicating infections due to an immunocompromised state. Since CAV-induced immunosuppression can cause a marked decrease in the immune response against other pathogens, understanding this aspect of the disease is critically important, as well as providing insights into developing new control approaches. With increasing emphasis on developing alternative control programs for poultry diseases, novel therapeutic strategies provide one approach. We show here that the in ovo administration of ChIFN-γ impacts the depletion of T-cell precursors during CAV infection. Therefore, it appears that ChIFN-γ may have the potential to be used as a novel therapeutic reagent to impact virus infection and alter immunosuppression caused by CAV and potentially other pathogens.

Immunity to Marek's disease: where are we now?

Marek's disease (MD) in chickens was first described over a century ago and the causative agent of this disease, Marek's disease virus (MDV), was first identified in the 1960's. There has been extensive and intensive research over the last few decades to elucidate the underlying mechanisms of the interactions between the virus and its host. We have also made considerable progress in terms of developing efficacious vaccines against MD. The advent of the chicken genetic map and genome sequence as well as development of approaches for chicken transcriptome and proteome analyses, have greatly facilitated the process of illuminating underlying genetic mechanisms of resistance and susceptibility to disease. However, there are still major gaps in our understanding of MDV pathogenesis and mechanisms of host immunity to the virus and to the neoplastic events caused by this virus. Importantly, vaccines that can disrupt virus transmission in the field are lacking. The current review explores mechanisms of host immunity against Marek's disease and makes an attempt to identify the areas that are lacking in this field.

Effects of oligosaccharides in a soybean meal-based diet on fermentative and immune responses in broiler chicks challenged with Eimeria acervulina

Fermentable oligosaccharides, particularly those found in soybean meal (SBM), may modulate fermentation in the ceca, thus affecting intestinal immune responses to intestinal pathogens. We hypothesized that fermentable oligosaccharides found in SBM would positively affect cecal fermentation and intestinal immune status in chicks challenged with an acute coccidiosis (Eimeria acervulina) infection and fed either a SBM-based diet or a semi-purified soy protein isolate- (SPI) based diet. Using a completely randomized design, 1-d-old broiler chicks (n = 200; 5 replications/treatment; 5 chicks/replication) were assigned to 1 of 4 SBM- or SPI-based diets containing either dietary cellulose (4%) or a fermentable carbohydrate, galactoglucomannan oligosaccharide-arabinoxylan (GGMO-AX) complex (4%). On d 9 posthatch, an equal number of chicks on each diet were inoculated with either distilled water (sham control) or E. acervulina (1 × 10(6) oocysts) and then euthanized on d 7 postinoculation. Overall, body weight gain and feed intake were greater (P < 0.01) for SBM-fed chicks, regardless of infection status. Gain:feed ratio was greater (P ≤ 0.05) for SPI-fed chicks except during d 3-7 postinoculation. Infection status, but not fiber source, affected propionate, isobutyrate, isovalerate, and total branched-chain fatty acid concentrations (P ≤ 0.02). Soybean meal-based diets resulted in greater (P ≤ 0.04) short-chain fatty acid and branched-chain fatty acid concentrations than SPI-based diets. Messenger RNA fold changes relative to uninfected SBM-cellulose-fed chicks of all duodenal cytokines were greater (P ≤ 0.01) for infected chicks, and SBM-fed chicks had greater (P < 0.01) interferon-γ and interleukin-12β expression compared with SPI-fed chicks. Cecal tonsil cytokine expression was also affected (P ≤ 0.02) by infection; however, protein source only affected (P < 0.01) interleukin-1β expression in this tissue. Overall, a SBM-based diet, compared with a semi-purified SPI-based diet with a different ingredient composition, resulted in greater weight gain, feed intake, and short-chain fatty acid production regardless of infection status, and also greater duodenal cytokine expression in E. acervulina- infected chicks, which is hypothesized to be related to the nutrients and oligosaccharides found in SBM.

Immunomodulation of bivalent Newcastle disease DNA vaccine induced immune response by co-delivery of chicken IFN-γ and IL-4 genes

The basic objective of this study was to enumerate whether co-administration of interferon-γ (IFN-γ) and/or interleukin-4 (IL-4) gene along with a bivalent Newcastle disease (ND) DNA vaccine construct could modulate the immune response to the DNA vaccine in chickens. pVIVO2 vector carrying Haemaglutinin-Neuraminidase (HN) and Fusion (F) genes of Newcastle disease virus (NDV) at its two cloning sites was used as a DNA vaccine. The same vector was used to clone the chicken IFN-γ and IL-4 genes at the multiple cloning site-1 separately. In vitro expression of IFN-γ and IL-4 gene constructs was assessed by reverse transcriptase-polymerase chain reaction (RT-PCR) and that of HN and F genes by indirect fluorescent antibody technique (IFAT) in addition to RT-PCR. The chickens were immunized thrice intramuscularly at 21, 36 and 46 days of age with the bivalent DNA vaccine alone, or in combination with IFN-γ/IL-4 or both cytokine gene constructs. The bivalent DNA vaccine led to increase in both NDV specific antibodies as assessed by enzyme linked immunosorbent assay (ELISA) and haemagglutination inhibition test (HI) and cell mediated immune (CMI) response as assessed by lymphocyte transformation test (LTT) employing MTT assay. Co-administration of the DNA vaccine with IL-4 gene resulted in highest IgY levels while IFN-γ produced highest CMI response. The DNA vaccine alone could afford only 10% protection against challenge infection by velogenic NDV. This protection was increased to 40% when IL-4 gene construct was co-administered with the DNA vaccine. Co-injection of IFN-γ as well as the combination of IFN-γ and IL-4 gene constructs with the DNA vaccine yielded 20% protection. Our study suggests that IL-4 may prove to be more appropriate as a genetic adjuvant than IFN-γ for ND DNA vaccine.

Vaccination of chickens with DNA vaccine expressing Eimeria tenella MZ5-7 against coccidiosis

A chimeric DNA vaccine co-expressing Eimeria tenella MZ5-7 and chicken IL-17 gene was constructed and its efficacy against E. tenella challenge was evaluated. The ORF of MZ5-7 from E. tenella's second generation merozoite and the mature interleukin 17 gene of chicken were cloned into the expression vector of pcDNA4.0 to construct DNA vaccine pcDNA4.0-MZ and pcDNA4.0-MZ-IL17. The expression of aim gene products in vivo was detected by western blotting. The expression of IL-2 and IFN-γ in chicken splenocytes was detected by RT-PCR 7 days post-immunization. The expression levels of the two cytokines in the pcDNA4.0-MZ-IL17 DNA vaccine immunized group were significantly higher than that in the pcDNA4.0-MZ immunized group (p<0.05). Either pcDNA4.0-MZ or pcDNA4.0-MZ-IL17 DNA vaccine could obviously alleviate cecal lesions, body weight loss and increase oocyst decrease ratio. The ACI of pcDNA4.0-MZ-IL17 group was 190, which is higher than that of pcDNA4.0-MZ group and all the three control groups. In short, MZ5-7 was an effective candidate antigen for vaccine and co-expression of cytokine with antigen was an alternative method to enhance the immunity DNA vaccine.