Dynamics of lymphocyte subpopulation changes in the cecal tonsils of chickens infected with Salmonella enteritidis

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

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

PLGA Nanospheres as Delivery Platforms for Eimeria mitis 1a Protein: A Novel Strategy to Improve Specific Immunity

The infections of chicken coccidiosis impact the welfare of chickens and the economical production of poultry. Eimeria mitis is ubiquitous in chicken coccidiosis, and E. mitis infection can significantly affect the productivity of birds. Up to now, few efficient vaccines against E. mitis have been reported, whereas the recombinant subunit vaccines delivered by nanomaterials may elicit an encouraging outcome. Thus, in this study, we chose E. mitis 1a (Em1a) protein as the candidate antigen to generate Em1a preparations. The recombinant Em1a (rEm1a) protein was encapsulated with poly lactic-co-glycolic acid (PLGA) and chitosan (CS) nanospheres. The physical characterization of the rEm1a-PLGA and rEm1a-CS nanospheres was investigated, and the resulting nanospheres were proven to be nontoxic. The protective efficacy of rEm1a-PLGA and rEm1a-CS preparations was evaluated in E. mitis-challenged birds in comparison with two preparations containing rEm1a antigen emulsified in commercially available adjuvants. ELISA assay, flow cytometry analysis, and quantitative real-time PCR (qPCR) analysis indicated that vaccination with rEm1a-loaded nanospheres significantly upregulated the secretions of antibodies and cytokines and proportions of CD4⁺ and CD8⁺ T lymphocytes. Compared with the other three preparations, rEm1a-PLGA nanosphere was more effective in improving growth performance and inhibiting oocyst output in feces, indicating that the PLGA nanosphere was associated with optimal protection against E. mitis. Collectively, our results highlighted the advantages of nanovaccine in eliciting protective immunity and may provide a new perspective for developing effective vaccines against chicken coccidiosis.

An Eimeria maxima Antigen: Its Functions on Stimulating Th1 Cytokines and Protective Efficacy Against Coccidiosis

A consensus is that the Th1 immune response plays a predominant role against avian coccidiosis. Therefore, an antigen with the ability to induce Th1 cytokine responses is an ideal candidate for the development of coccidiosis vaccines. In our previous study, EmARM-β, a Th1 cytokines-stimulating antigen, was screened from the cDNA expression library of Eimeria maxima (E. maxima). Herein, we verified its stimulative effects on Th1 cytokine productions and evaluated its protective efficacy against E. maxima infection. Recombinant EmARM-β protein was expressed, and eukaryotic expression plasmid pVAX1-EmARM-β was also constructed for the immunization of birds. An immunofluorescence assay was performed to detect the native form of EmARM-β protein in the stage of sporozoites. Expressions of specific transcription factors and cytokines in immunized chickens were measured using qPCR and ELISA to verify its stimulating function on Th1 cytokines. Specific IgG antibody levels and T lymphocyte subpopulation in the immunized chickens were detected using ELISA and indirect flow cytometry to determine induced immune responses. The results showed that EmARM-β native protein is massively expressed in the sporozoites stage of E. maxima. Effective stimulation from the EmARM-β antigen to T-bet and Th1 cytokines (IL-2 and IFN-γ) was observed in vivo. After being immunized with rEmARM-β or pVAX1-EmARM-β, significant promotion to the proportion of CD4+ and CD8+ T cells and the level of antigen-specific IgG antibodies in immunized chickens was also observed. Furthermore, vaccination with rEmARM-β antigen or pVAX1-EmARM-β resulted in alleviated weight loss and enteric lesion, reduced oocyst output, and higher anticoccidial index (ACI) in challenged birds. These results indicate that EmARM-β antigen can effectively stimulate the expression of Th1 cytokines and initiate host immune responses, providing moderate protective efficacy against E. maxima. Notably, EmARM-β protein is a promising candidate for developing a novel anticoccidial vaccine.

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.

Toxoplasma gondii Proteasome Subunit Alpha Type 1 with Chitosan: A Promising Alternative to Traditional Adjuvant

As an important zoonotic protozoan, Toxoplasma gondii (T. gondii) has spread around the world, leading to infections in one-third of the population. There is still no effective vaccine or medicine against T. gondii, and recombinant antigens entrapped within nanospheres have benefits over traditional vaccines. In the present study, we first expressed and purified T. gondii proteasome subunit alpha type 1 (TgPSA1), then encapsulated the recombinant TgPSA1 (rTgPSA1) in chitosan nanospheres (CS nanospheres, rTgPSA1/CS nanospheres) and incomplete Freund’s adjuvant (IFA, rTgPSA1/IFA emulsion). Antigens entrapped in CS nanospheres reached an encapsulation efficiency of 67.39%, and rTgPSA1/CS nanospheres showed a more stable release profile compared to rTgPSA1/IFA emulsion in vitro. In vivo, Th1-biased cellular and humoral immune responses were induced in mice and chickens immunized with rTgPSA1/CS nanospheres and rTgPSA1/IFA emulsion, accompanied by promoted production of antibodies, IFN-γ, IL-4, and IL-17, and modulated production of IL-10. Immunization with rTgPSA1/CS nanospheres and rTgPSA1/IFA emulsion conferred significant protection, with prolonged survival time in mice and significantly decreased parasite burden in chickens. Furthermore, our results also indicate that rTgPSA1/CS nanospheres could be used as a substitute for rTgPSA1/IFA emulsion, with the optimal administration route being intramuscular in mass vaccination. Collectively, the results of this study indicate that rTgPSA1/CS nanospheres represent a promising vaccine to protect animals against acute toxoplasmosis.

Poly (D, L-lactide-co-glycolide) delivery system improve the protective efficacy of recombinant antigen TA4 against Eimeria tenella infection

Eimeria tenella is a protozoan parasite endemic in chickens and is one of the causative agents of avian coccidiosis. The aim of this research was to determine if poly (D, L-lactide-co-glycolide) (PLGA) nanoparticles carrying recombinant TA4 protein of E. tenella (rEtTA4) could improve the level of protective immunity against E. tenella challenge. Recombinant TA4 protein was expressed and purified. Poly (D, L-lactide-co-glycolide) loaded with rEtTA4 (PLGA-rEtTA4) nanoparticles was prepared and was delivered to 2-week-old layer chickens via intramuscular inoculation. Chickens injected with PBS and PLGA nanoparticles were served as control groups. The rEtTA4 and PLGA-rEtTA4 nanoparticles induced changes of serum cytokines, IgY levels, and T lymphocytes subpopulation, and the protective efficacy against E. tenella challenge was evaluated. Results showed that both rEtTA4 and PLGA-rEtTA4 vaccination groups induced significantly higher levels of specific EtTA4 IgY antibody and IL-17 and higher proportion of CD8⁺ T lymphocytes. However, no significant differences were observed in the proportion of CD4⁺ T lymphocytes compared with the PBS control. Chickens immunized with rEtTA4 and PLGA-rEtTA4 prominently increased the BW gains and decreased oocyst output compared with chickens immunized with PBS and PLGA after oral challenge with E. tenella. Poly (D, L-lactide-co-glycolide) encapsulated rEtTA4 nanoparticles–immunized chickens significantly induced higher levels of interferon gamma, IL-6, and IL-17 and a little bit higher proportion of CD8⁺ T lymphocytes compared with rEtTA4 subunit vaccine–immunized chickens. Thus, PLGA encapsulated rEtTA4 nanoparticles appeared to have great potential to enhance the immune response and improved the protective efficacy against E. tenella infection. Our results provided available protective subunit vaccine rEtTA4 and PLGA loaded with rEtTA4 nanoparticles against coccidiosis and suggested that PLGA nanoparticles could be an effective adjuvant to enhance the protective efficacy of rEtTA4 subunit vaccine.

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.

Protective immunity induced by Eimeria common antigen 14-3-3 against Eimeria tenella, Eimeria acervulina and Eimeria maxima

Background

Avian coccidiosis is often caused by co-infection with several species of Eimeria worldwide. Developing a multivalent vaccine with an antigen common to multiple Eimeria species is a promising strategy for controlling clinical common co-infection of Eimeria. In the previous study, 14–3-3 was identified as one of the immunogenic common antigen in E. tenella, E. acervulina and E. maxima. The aim of the present study was to evaluate the immunogenicity and protective efficacy of Ea14–3-3 in the form of DNA vaccine against infection with three species of Eimeria both individually and simultaneously.

Results

After vaccination with pVAX-Ea14–3-3, the Ea14–3-3 gene was transcribed and expressed in the injected muscles. Vaccination with pVAX-Ea14–3-3 significantly increased the proportion of CD4⁺ and CD8⁺ T lymphocytes and produced a strong IgY response in immunized chickens. Similarly, pVAX-Ea14–3-3 stimulated the chicken’s splenocytes to produce high levels of Th1-type (IFN-γ, IL-2) and Th2-type (IL-4) cytokines. The vaccine-induced immune response was responsible to increase weight gain, decreased the oocyst output, and alleviated enteric lesions significantly in immunized chickens as compared to control group, in addition to induce moderate anti-coccidial index (ACI).

Conclusion

These results indicate that Ea14–3-3 is highly immunogenic and capable to induce significant immune responses. Furthermore, Ea14–3-3 antigen can provide effective protection against infection with Eimeria tenella, Eimeria acervulina, Eimeria maxima both individually and in combination with three Eimeria species. Significant outcomes of our study provide an effective candidate antigen for developing a multivalent Eimeria vaccine against mixed infection with various Eimeria species under natural conditions.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1665-z) contains supplementary material, which is available to authorized users.

Effect of synbiotic supplementation on layer production and cecal Salmonella load during a Salmonella challenge

This study analyzed the inhibitory effects of a synbiotic product (PoultryStar® me) on production parameters, intestinal microflora profile, and immune parameters in laying hens with and without a Salmonella challenge. The synbiotic product contained 4 probiotic bacterial strains (Lactobacillus reuteri, Enterococcus faecium, Bifidobacterium animalis, and Pediococcus acidilactici) and a prebiotic fructooligosaccharide. Layers were supplemented with the synbiotic from d of hatch to 28 wk of age. At 16 wk of age, birds were either vaccinated with Salmonella enterica Enteritidis (SE) vaccine or left unvaccinated. At 24 wk of age, a portion of the birds was challenged with 1 × 109 CFU of SE or left unchallenged, resulting in a 3 (vaccinated, challenged, or both vaccinated and challenged) X 2 (control and synbiotics) factorial arrangement of treatments. At 18 and 20 wk of age, birds fed synbiotics in both vaccinated and unvaccinated groups had increased (P < 0.05) BW more than those in the un-supplemented groups. Birds fed synbiotics had 0.7, 17.8, 21.7, 3, and 4.2% higher (P < 0.05) hen d egg production (HDEP) at 19, 20, 21, 22, and 23 wk of age, compared to the birds without supplementation, respectively. After administering the SE challenge, supplemented birds had 3, 6.7, 4.3, 12.5, and 14.4% higher (P < 0.05) HDEP at 24, 25, 26, 27, and 28 wk of age, compared to the birds not supplemented, respectively. Irrespective of the vaccination status, birds fed synbiotics and challenged with SE had a lower (P < 0.05) SE cecal load compared to the un-supplemented groups. At 22 d post Salmonella challenge, birds supplemented, vaccinated, and challenged had the highest bile IgA content. It can be concluded that supplementation of the synbiotic product could be beneficial to layer diets as a growth promoter, performance enhancer, and for protection against SE infection.

The molecular characterization and protective efficacy of microneme 3 of Eimeria mitis in chickens

E. mitis is ubiquitous in clinical coccidiosis caused by mixed infection of Eimeria species and the infection by E. mitis usually significantly impairs productivity of the infected chickens. To date, however, few protective antigens from E. mitis have been reported. In this study, the molecular characterization and protective efficacy of microneme 3 of Eimeria mitis (EmiMIC3) were analyzed. EmiMIC3 gene was cloned from sporozoites of E. mitis and its MARs (microneme adhesive repeats domain) were predicted. Recombinant EmiMIC3 (rEmiMIC3) was expressed in E. coli and purified and then was analyzed by western blot with anti-E. mitis chicken serum. Meanwhile, native EmiMIC3 from sporozoites was analyzed by anti-rEmiMIC3 rat serum. The expressions of EmiMIC3 in E. mitis sporozoites and merozoites were analyzed by immunofluorescence assay. The rEmiMIC3-induced changes of T lymphocytes subpopulation, serum cytokines and IgY levels and the protective efficacy of rEmiMIC3 were determined in animal experiments. The results showed that the deduced open reading frame (ORF) of EmiMIC3 was composed of 1145 amino acids, possessing 9 MARs. EmiMIC3 gene was submitted to GenBank (accession number: MG888670). EmiMIC3 could express in sporozoites and merozoites respectively and located at the apex of E. mitis sporozoite. Western blot assay revealed that the rEmiMIC3 could be recognized by serum of chicken infected by E. mitis and the native EmiMIC3 from sporozoites could also be recognized by rat serum against rEmiMIC3. Following vaccination with rEmiMIC3, higher levels of IL-10, IFN-γ, TGF-βand IL-17, higher proportions of CD4+/CD3+ and CD8+/CD3 + T lymphocytes and higher level of IgY antibody were induced compared to the controls. Vaccination with rEmiMIC3 prominently increased the weight gains and decreased oocyst output of the vaccinated chickens after challenge infection. Our result not only enriches protective candidate antigen of E. mitis, but also provides available protective antigen of E. mitis for the development of multivalent vaccines against infection caused by mixture of Eimeria species in clinical coccidiosis.

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.

Protective immunity against Eimeria maxima induced by vaccines of Em14-3-3 antigen

Eimeria maxima 14-3-3 (Em14-3-3) open reading frame (ORF) which consisted of 861 bp encoding a protein of 286 amino acids was successfully amplified and sequenced. Subsequently, the Em14-3-3 ORF was subcloned into pET-32a (+) and pVAX1, respectively. RT-PCR and immunoblot analyses confirmed that the target gene was successfully transcribed and expressed in vivo. Immunofluorescence analysis showed that Em14-3-3 was expressed in both the sporozoites and merozoites. The animal experiments demonstrated that both rEm14-3-3 and pVAX1-14-3-3 could clearly alleviate jejunum lesions and body weight loss. The Em14-3-3 vaccines could increase oocyst decrease ratio, as well as produce an anticoccidial index of more than 165. The percentages of CD4⁺ in both the Em14-3-3 immunized groups were much higher, when compared with those of PBS, pET32a (+), and pVAX1 controls (P < 0.05). Similarly, the anti-Em14-3-3 antibody titers of both rEm14-3-3 and pVAX1-14-3-3 immunized groups showed higher levels compared with those of PBS, pET32a (+), and pVAX1 controls (P < 0.05). The IFN-γ and tumor growth factor-β (TGF-β) levels showed significant increments in the rEm14-3-3 and pVAX1-14-3-3 immunized groups, when compared with those in the negative controls (P < 0.05). These results demonstrated that Em14-3-3 could be used as a promising antigen candidate for developing vaccines against E. maxima.

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.

Toxoplasma gondii Elongation Factor 1-Alpha (TgEF-1α) Is a Novel Vaccine Candidate Antigen against Toxoplasmosis

Toxoplasma gondii (T. gondii) is an obligate intracellular parasite which can infect almost all warm-blood animals, leading to toxoplasmosis. Screening and discovery of an effective vaccine candidate or new drug target is crucial for the control of this disease. In this study, the recombinant T. gondii elongation factor 1-alpha (rTgEF-1α) was successfully expressed in in Escherichia coli. Passive immunization of mice with anti-rTgEF-1α polyclonal antibody following challenge with a lethal dose of tachyzoites significantly increased the survival time compared with PBS control group. The survival time of mice challenged with tachyzoites pretreated with anti-rTgEF-1α PcAb also was significantly increased. Invasion of tachyzoites into mouse macrophages was significantly inhibited in the anti-rTgEF-1α PcAb pretreated group. Mice vaccinated with rTgEF-1α induced a high level of specific anti-T. gondii antibodies and production of IFN-gamma, interleukin-4. The expression levels of MHC-I and MHC-II molecules as well as the percentages of CD4⁺ and CD8⁺ T cells in mice vaccinated with rTgEF-1α was significantly increased, respectively (P < 0.05), compared with all the controls. Immunization with rTgEF-1α significantly (P < 0.05) prolonged survival time (14.53 ± 1.72 days) after challenge infection with the virulent T. gondii RH strain. These results indicate that T. gondii EF-1α plays an essential role in mediating host cell invasion by the parasite and, as such, could be a candidate vaccine antigen against toxoplasmosis.

The Molecular Characterization and Immunity Identification of Microneme 3 of Eimeria acervulina

The gene of Eimeria acervulina microneme protein 3 (EaMIC3) was cloned and characterized. According to the conserved sequence, the 3'- and 5'-ends of EaMIC3 were amplified by the rapid amplification of cDNA ends (RACE). The full length cDNA of this gene was obtained by overlapping the sequences of 3'- and 5'-extremities and amplification by reverse transcription PCR. The sequence analysis revealed that the opening reading frame (ORF) of EaMIC3 was 2,607 bp and encoded a protein of 868 amino acids with 93.04 kDa. Western blotting assay showed that the recombinant protein was successfully recognized by the sera of chickens experimentally infected with E. acervulina, whereas the native protein in the somatic extract of sporozoites was as well detected by sera from rats immunized with the recombinant protein of EaMIC3. Immunofluorescence analysis indicated that EaMIC3 was expressed in the sporozoites and merozoites stages of E. acervulina. Animal challenge experiments demonstrated that the recombinant protein of EaMIC3 could significantly increase the average body weight gains, decrease the mean lesion scores and the oocyst outputs of the immunized chickens and presented anticoccidial index (ACI) more than 165. Moreover, EaMIC3 protein produced significantly high level of IgG antibody, IFN-γ, IL-10, IL-17 TGF-β, CD4⁺ , and CD8⁺ .

Immune Responses in Cecal Tonsils of Marek's Disease Virus-Infected Chickens

Marek's disease (MD) is a lymphoproliferative disease of domestic chickens that is caused by a highly cell-associated oncogenic α-herpesvirus, Marek's disease virus (MDV). MDV replicates in chicken lymphocytes and establishes a latent infection within CD4+ T cells. Clinical signs of MD include depression, crippling, weight loss, bursal/thymic atrophy, neurologic disorders, and rapid onset of T cell lymphomas that infiltrate lymphoid tissues, visceral organs, and peripheral nerves. The cecal tonsils (CTs) are considered the largest lymphoid aggregates of avian gut-associated lymphoid tissue. Along with Peyer's patches, CTs elicit protective immune responses against bacterial and viral pathogens in the intestinal tract of avian species. In this study, we investigated the effect of MDV infection on toll-like receptor (TLR) gene expression in CTs of MD-susceptible (72) and resistant (63) chicken lines. Real-time PCR gene expression profiling revealed that of the 10 TLRs tested, TLR2A, TLR3, TLR5, and TLR15 displayed significant differential expression patterns at different time points postinoculation. The expression levels of the remaining six genes were minimally affected by MDV infection in either line. Immunohistochemical analysis showed a severe depletion of B cells and CD4+ T cells in the CTs of susceptible line at 5 days postinfection (dpi), which recovered by 21 dpi. The destruction of B and T cells in the CTs of the resistant line was minimal at 5 dpi, which also recovered by 21 dpi. A significant infiltration of macrophages was observed after the depletion of B and T cells in the infected birds of both lines that could account for the differential TLR gene expression in the infected birds. The data presented provide further insight into the mechanism of MDV pathogenesis and tissue-specific immunologic responses to viral infection.

Protective immunity against acute toxoplasmosis in BALB/c mice induced by a DNA vaccine encoding Toxoplasma gondii elongation factor 1-alpha

BACKGROUND

Toxoplasma gondii can infect almost all warm-blood animals including human beings. The high incidence and severe damage that can be caused by T. gondii infection clearly indicates the need for the development of a vaccine. T. gondii elongation factor 1-alpha (TgEF-1α) plays an important role in pathogenesis and host cell invasion for this parasite. The aim of this study was to evaluate the immune protective efficacy of a DNA vaccine encoding TgEF-1α gene against acute T. gondii infection in mice.

METHODS

A DNA vaccine (pVAX-EF-1α) encoding T. gondii EF-1a (TgEF-1α) gene was constructed and its immune response and protective efficacy against lethal challenge in BALB/c mice were evaluated.

RESULTS

Mice inoculated with the pVAX-EF-1α vaccine had a high level of specific anti-T. gondii antibodies and produced high levels of IFN-gamma, interleukin (IL)-4, and IL-17. The expression levels of MHC-I and MHC-II molecules as well as the percentages of both CD4(+) and CD8(+) T cells in mice vaccinated with pVAX-EF-1α were significantly increased (p < 0.05), compared with those in all the mice from control groups (blank control, PBS, and pVAXI). Immunization with pVAX-EF-1α significantly (p < 0.05) prolonged mouse survival time to 14.1 ± 1.7 days after challenge infection with the virulent T. gondii RH strain, compared with mice in the control groups which died within 8 days.

CONCLUSIONS

DNA vaccination with pVAX-EF-1α triggered strong humoral and cellular responses and induced effective protection in mice against acute T. gondii infection, indicating that TgEF-1α is a promising vaccine candidate against acute toxoplasmosis.

Protective immunity against acute toxoplasmosis in BALB/c mice induced by a DNA vaccine encoding Toxoplasma gondii 10 kDa excretory-secretory antigen (TgESA10)

Toxoplasma gondii 10 kDa excretory-secretory antigen (TgESA10) is involved in the early stages of host invasion. The aim of this study was to evaluate the immune protective efficacy of a DNA vaccine encoding TgESA10 gene against acute T. gondii infection in mice. The gene sequence encoding TgESA10 was inserted into the eukaryotic expression vector pVAX I, and the efficacy of intramuscular vaccination of BALB/c mice with pVAX-ESA10 was analyzed. Mice immunized with pVAX-ESA10 elicited high titers of total IgG, IgG1, IgG2a, IgA and IgM antibodies, while IgE showed no changes. Analysis of cytokine profiles revealed significant increases of IFN-γ, IL-4 and IL-17, while no significant changes were detected in TGF-β1. Additionally, we found that pVAX-ESA10 enhanced the activation of CD4(+) and CD8(+) T cells and the expression of MHC-I and MHC-II molecules in spleen in mice. Immunization with pVAX-ESA10 significantly prolonged survival time (14.3 ± 1.7 days) after challenge infection with the virulent T. gondii RH strain, compared with the control groups which died within 8 days. These results suggested that TgESA10 DNA vaccine could trigger strong humoral and cellular responses and induce partial protection against acute toxoplasmosis.

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.

Avaliação da resposta imunológica da mucosa intestinal de frangos de corte desafiados com diferentes sorovares de Salmonella

Objetivou-se com o presente estudo comparar o efeito de diferentes sorovares de Salmonella na resposta imune local da mucosa do intestino de frangos de corte. Aos sete dias de idade, as aves foram desafiadas com os sorovares S. Enteritidis, S. Typhimurium, S. Senftenberg, S. Mbandaka e S. Minnesota. Foi observado que todos os sorovares testados foram capazes de colonizar o intestino das aves sendo possível o isolamento de Salmonella em suabes de cloaca, 48 h após inoculação. De maneira geral, as aves do grupo controle negativo, que não foram desafiados apresentaram quantidade significativamente menor de células imunológicas na mucosa intestinal do que as aves desafiadas. Porém, verificou-se que os sorovares de Salmonella, utilizados neste estudo, apresentaram diferentes efeitos sobre a dinâmica celular da mucosa do íleo e ceco e afetaram de modo diferente o ganho de peso e ganho médio diário das aves demonstrando distintos graus de patogenicidade. Os sorovares Enteritidis e Typhimurium apresentaram um efeito mais intenso tanto no desempenho quanto na mobilização de células imunológicas na mucosa intestinal de frangos de corte

Gene expression in the chicken caecum in response to infections with non-typhoid Salmonella

Chickens can be infected with Salmonella enterica at any time during their life. However, infections within the first hours and days of their life are epidemiologically the most important, as newly hatched chickens are highly sensitive to Salmonella infection. Salmonella is initially recognized in the chicken caecum by TLR receptors and this recognition is followed by induction of chemokines, cytokines and many effector genes. This results in infiltration of heterophils, macrophages, B- and T-lymphocytes and changes in total gene expression in the caecal lamina propria. The highest induction in expression is observed for matrix metalloproteinase 7 (MMP7). Expression of this gene is increased in the chicken caecum over 4000 fold during the first 10 days after the infection of newly hatched chickens. Additional highly inducible genes in the caecum following S. Enteritidis infection include immune responsive gene 1 (IRG1), serum amyloid A (SAA), extracellular fatty acid binding protein (ExFABP), serine protease inhibitor (SERPINB10), trappin 6-like (TRAP6), calprotectin (MRP126), mitochondrial ES1 protein homolog (ES1), interferon-induced protein with tetratricopeptide repeats 5 (IFIT5), avidin (AVD) and transglutaminase 4 (TGM4). The induction of expression of these proteins exceeds a factor of 50. Similar induction rates are also observed for chemokines and cytokines such as IL1β, IL6, IL8, IL17, IL18, IL22, IFNγ, AH221 or iNOS. Once the infection is under control, which happens approx. 2 weeks after infection, expression of IgY and IgA increases to facilitate Salmonella elimination from the gut lumen. This review outlines the function of individual proteins expressed in chickens after infection with non-typhoid Salmonella serovars.

Salmonella Virchow Infection of the Chicken Elicits Cellular and Humoral Systemic and Mucosal Responses, but Limited Protection to Homologous or Heterologous Re-Challenge

Salmonella enterica serovar Virchow usually causes mild gastroenteritis in humans; however, it is frequently invasive and many isolates are resistant to a broad-range of therapeutic antimicrobials. Poultry meat is considered a major source of human infection. In this study, we characterize the infection biology and immune response to S. Virchow in chickens and determine protection against homologous and heterologous re-challenge, with S. Virchow or S. Typhimurium. Following oral infection of 7-day-old chickens, S. Virchow colonized the gastrointestinal tract and the spleen. Infection elicited an increase in specific IgA, IgG, and IgM antibodies and relative quantitative changes in several leukocyte populations, including CD3, CD4, CD8α, CD8β, MHC II, KuL01, and γδ TCR positive cells, both in the gastrointestinal tract and systemically. Increased expression of pro-inflammatory cytokines IL-1β and IL-6 and the chemokine CXCLi2 was also found. Primary infection with S. Virchow offered limited systemic protection against re-challenge with S. Virchow or S. Typhimurium, but no protection against cecal colonization. In conclusion, S. Virchow exhibits similar infection biology and immune responses in the chicken to that previously described for S. Typhimurium. Unlike S. Typhimurium, S. Virchow infection is poorly protective to homologous and heterologous re-challenge. These findings suggest that S. Virchow is capable of colonizing the chicken well and therefore, presents a risk of entering the food chain in meat production. Furthermore, the development of vaccines that protect effectively against S. Virchow and indeed multivalent vaccines that protect across all Salmonella serogroups in the chicken would appear to remain a challenging proposition.

DNA vaccination with a gene encoding Toxoplasma gondii Deoxyribose Phosphate Aldolase (TgDPA) induces partial protective immunity against lethal challenge in mice

Background

Toxoplasma gondii is an obligate intracellular parasite that causes a pathological status known as toxoplasmosis, which has a huge impact on human and animal health. Currently, the main control strategy depends on the usage of drugs that target the acute stage of the infection, however, drawbacks were encountered while applying this method; therefore, development of an alternative effective method would be important progress. Deoxyribose Phosphate Aldolase (TgDPA) plays an important role supporting cell invasion and providing energy for the parasite.

Methods

TgDPA was expressed in Escherichia coli and the purified recombinant protein was used to immunize rats. The antibodies obtained were used to verify in vitro expression of TgDPA. The vector pVAX1 was utilized to formulate a DNA vaccine designated as pTgDPA, which was used to evaluate the immunological changes and the level of protection against challenge with the virulent RH strain of T. gondii.

Results

DNA vaccine, TgDPA revealed that it can induce a strong humoral as well as cellular mediated response in mice. These responses were a contribution of T_H1, T_H2 and T_H17 type of responses. Following challenge, mice immunized with TgDPA showed longer survival rates than did those in control groups.

Conclusions

Further investigation regarding TgDPA is required to shed more light on its immunogenicity and its possible selection as a vaccine candidate.

Pichia pastoris expressed EtMic2 protein as a potential vaccine against chicken coccidiosis

Chicken coccidiosis caused by Eimeria species leads to tremendous economic losses to the avian industry worldwide. Identification of parasite life cycle specific antigens is a critical step in recombinant protein vaccine development against Eimeria infections. In the present study, we amplified and cloned the microneme-2 (EtMIC2) gene from Eimeria tenella wild type strain SD-01, and expressed the EtMic2 protein using Pichia pastoris and Escherichia coli expression systems, respectively. The EtMic2 proteins expressed by P. pastoris and E. coli were used as vaccines to immunize chickens and their protective efficacies were compared and evaluated. The results indicated that both P. pastoris and E. coli expressed EtMic2 proteins exhibited good immunogenicity in stimulating host immune responses and the Pichia expressed EtMic2 provided better protection than the E. coli expressed EtMic2 did by significantly increasing growth rate, inducing high specific antibody response, reducing the oocyst output and cecal lesions. Particularly, the Pichia expressed EtMic2 protein exhibited much better ability in inducing cell mediated immune response than the E. coli expressed EtMic2.

Co-expression of EtMic2 protein and chicken interleukin-18 for DNA vaccine against chicken coccidiosis

In the present study, a naked EtMIC2 DNA vaccine, a ChIL-18 expression vector and a EtMIC2 and ChIL-18 co-expression DNA vaccine were constructed and their protective efficacies against homologous challenge were compared and evaluated by examining the body weight gain, oocyst shedding, cecal lesion, ACI as well as specific anti-EtMic2 antibody level, the proliferation ability and percentages of CD4+ and CD8+ of splenocytes. The results showed the naked EtMIC2 DNA vaccine could increase the weight gain and decrease the oocyst shedding, but could not alleviate the cecal lesion of immunized chickens compared to unimmunized chickens. Chickens immunized with the co-expression vector pVAX1-MIC2-IL-18 exhibited much improved immune protection against challenge compared to chickens immunized with naked EtMIC2 DNA vaccine, or with naked EtMIC2 DNA vaccine and ChIL-18 expression vector applied separately. These results suggest that the co-expression of ChIL-18 with EtMic2 together could significantly improve the immune protection of the EtMic2 protein.

Role of monochromatic light on development of cecal tonsil in young broilers

Previously, the different monochromatic lights have been demonstrated to affect splenocyte proliferation and melatonin (MEL) secretion in broilers. The present study was designed to evaluate the effects of different monochromatic lights on the development and immune function of broiler cecal tonsils, and to disclose the mechanisms underlying these phenomena. A total of 185 broilers (P0) including intact, sham-operated, and pinealectomized groups were exposed to blue light (BL), green light (GL), red light (RL), and white light (WL) by a light-emitting diode system for 14 days. Compared with RL groups, the GL in the intact and sham-operated groups showed larger follicle areas (66.70%), higher percentages of proliferating cell nuclear antigen (PCNA)-positive cells (33.33%), increased numbers of IgA(+) cells (48.60%), and increased antioxidase activity (33.33%-61.37%), whereas, the density of iNOS and MDA content in GL were lower (43.63%-54.43%) than that of RL. In contrast, after pinealectomy, the area of follicles, the percentage of PCNA-positive cells, the number of IgA(+) cells, and the antioxidase activity decreased in the different light treatments, but the density of iNOS and MDA content increased substantially. There was no significant difference in these parameters between broilers exposed to GL and other lights (P = 0.085-1.000). The results suggested that the enhanced effects of GL on the development and immune function of cecal tonsils in young broilers were mediated by elevated antioxidative status via up-regulation of MEL.

Early immune dynamics following infection with Salmonella enterica serovars Enteritidis, Infantis, Pullorum and Gallinarum: cytokine and chemokine gene expression profile and cellular changes of chicken cecal tonsils

Salmonella enterica subspecies enterica infection remains a serious problem in a wide range of animals and in man. Poultry-derived food is the main source of human infection with the non-host-adapted serovars while fowl typhoid and pullorum disease are important diseases of poultry. We have assessed cecal colonization and immune responses of newly hatched and older chickens to Salmonella serotypes Enteritidis, Infantis, Gallinarum and Pullorum. S. Enteritidis and S. Infantis colonized the ceca more efficiently than S. Gallinarum and S. Pullorum. Salmonella infection was also associated with increased staining for B-lymphocytes and macrophages in the cecal tonsils of infected birds. S. Enteritidis infection in newly hatched birds stimulated the expression of CXCLi1 and CXCLi2 chemokines in the cecal tonsils, while S. Gallinarum up-regulated the expression of LITAF. In older chickens, S. Enteritidis infection resulted in a significantly higher expression of CXCLi2, iNOS, LITAF and IL-10 while S. Pullorum appeared to down-regulate CXCLi1 expression in the cecal tonsils. Data from spleens showed either no expression or down-regulation of the tested genes.

Changes of cytokines and IgG antibody in chickens vaccinated with DNA vaccines encoding Eimeria acervulina lactate dehydrogenase

The aim of this study was to investigate the changes of cytokines and specific serum IgG in chickens following vaccination with DNA vaccines encoding either Eimeria acervulina (E. acervulina) lactate dehydrogenase (LDH) antigen or LDH and chicken IL-2 or IFN-γ. Two-week-old chickens were randomly divided into five groups. Experimental group of chickens were immunized with DNA vaccines while control group of chickens were injected with pVAX1 plasmid alone or sterile water. All immunizations were boosted 2 weeks later. The LDH-specific IgG antibody response was measured at weeks 1-6 post-second immunization. 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 (P<0.05) and reached the maximum values 3 weeks post-second immunization. The systemic and local cytokine mRNA expression was determined by quantitative RT-PCR 7 days post-second immunization. The specific IgG antibody levels against LDH of all chickens vaccinated with vaccines were increased compared to those of sterile water (H(2)O) and plasmid (pVAX1) control chickens 1-6 weeks post-second immunization (P<0.05). The mRNA levels of IFN-γ, IL-2, TNFSF15, IL-17D as well as TGF-β4 in both spleen and cecal tonsil were also increased in experimental chickens. In contrast, the only significant change of IL-4 mRNA level was observed in spleen of chickens immunized with pVAX-LDH-IL-2 compared with pVAX-LDH and control groups (P<0.05). These results suggested that DNA vaccines could increase the IgG antibody level and induce the expressions of cytokines.

Efficacy of DNA vaccines carrying Eimeria acervulina lactate dehydrogenase antigen gene against coccidiosis

The efficacies of DNA vaccines encoding either Eimeria acervulina lactate dehydrogenase (LDH) antigen or a combination of LDH antigen and chicken IL-2 or IFN-gamma were evaluated against chicken coccidiosis. Three vaccine plasmids pVAX-LDH, pVAX-LDH-IFN-gamma and pVAX-LDH-IL-2 were constructed using the eukaryotic expression vector pVAX1. Expressions of proteins encoded by plasmids DNA in vivo were detected by reverse transcription-polymerase chain reaction (RT-PCR) and western blot assay. Average body weight gain, oocyst output, survival rate and lesion scores were measured to evaluate the protective effects of vaccination on challenge infection. The results showed that DNA vaccines could obviously alleviate body weight loss, duodenal lesions, oocyst output and enhance oocyst decrease ratio. Anti-coccidial indexes (ACIs) of pVAX-LDH-IFN-gamma and pVAX-LDH-IL-2 groups were higher than that of other groups. Flow cytometric analysis of T lymphocytes in spleen and cecal tonsil demonstrated that DNA vaccines had significantly increased percentages of CD3(+) T cells compared with pVAX1 alone or TE buffer. The results provided the first proof that DNA vaccine carrying E. acervulina LDH antigen gene induced protective immunity against homologous infection and its effect could be enhanced by co-expression of chicken IL-2 or IFN-gamma.

Prebiotics modulate immune responses in the gut-associated lymphoid tissue of chickens

The recent European Union ban on the prophylactic use of in-feed antibiotics has escalated the search for alternatives for use within the poultry industry. When evaluating the efficacy of potential antibiotic alternatives on bird health and productivity, it is important to analyze the competence of the immune cells in the gut-associated lymphoid tissue (GALT), because it is routinely involved in the surveillance of colonizing microbes as well as in interacting with the ingested feed antigens. Therefore, we studied the effect of the prebiotics mannan-oligosaccharide (MOS) and fructo-oligosaccharide (FOS) on the phenotypic and functional competence of immune cells in cecal tonsil (CT), which is a major GALT. Day-old Cobb 500 male broilers were randomized to 4 groups. Control chickens were fed the basal diet only. Chickens in experimental groups received 0.05 g/kg zinc bacitracin or 5 g/kg of either FOS or MOS in addition to basal diet. At the end of 25 d, our comparison of the experimental groups with controls revealed that the addition of prebiotics to diet resulted in a significant reduction in the proportion of B cells and in mitogen responsiveness of lymphocytes in CT. Furthermore, FOS treatment significantly enhanced the IgM and IgG antibody titers in plasma. These findings emphasize the need for the analyses of the gut immune function following treatment with novel feed additives. The knowledge obtained from such analyses may aid in understanding the mechanisms underlying the immune competence of the birds, which needs consideration when selecting and optimizing new feed additives instead of antibiotics for poultry production.

Gene expression profiling of chicken lymphoid cells after treatment with Lactobacillus acidophilus cellular components

Lactobacillus acidophilus has been shown to exert immunostimulating activities in a number of species, including the chicken. To examine the molecular mechanisms of this phenomenon, we investigated spatial and temporal expression of immune system genes in chicken cecal tonsil and spleen mononuclear cells in response to structural constituents of L. acidophilus. Using a low-density chicken immune system microarray, we found that cecal tonsil cells responded more rapidly than spleen cells to the bacterial stimuli, with the most potent stimulus for cecal tonsil cells being DNA and for splenocytes being the bacterial cell wall components. We also discovered that in both splenocytes and cecal tonsil cells, STAT2 and STAT4 genes were highly induced. Given the close interactions between cecal tonsil cells and commensal bacteria, we further examined the involvement of STAT2 and STAT4 signaling pathways in cellular responses to bacterial DNA. Our results revealed that the expression of STAT2, STAT4, IL-18, MyD88, IFN-alpha, and IFN-gamma genes were up-regulated in cecal tonsil cells after treatment with L. acidophilus DNA.

Immunogenomic approaches to study host immunity to enteric pathogens

With increasing consumer demands for safe poultry products, effective control of disease-causing pathogens is becoming a major challenge to the poultry industry. Many chicken pathogens enter the host through the gastrointestinal tract, and over the past few decades, in-feed antibiotics and active vaccination have been the 2 main mechanisms of disease control. However, increasing public concerns are prompting government regulations on the use of growth-promoting drugs in animal production, and the ability of current vaccines to protect against emerging hypervirulent strains of pathogens is becoming an issue. Therefore, there is a need to develop alternative control strategies against poultry pathogens of economic importance as well as to carry out basic research to enhance understanding of host-pathogen interactions at local sites of infection. Effective control strategies against pathogens can only be accomplished by comprehensive analysis of the basic immunobiology of host-pathogen interactions. Recent sequencing of the poultry genome and the availability of several tissue-specific cDNA microarrays are facilitating the rapid application of functional immunogenomic technologies to poultry disease research. Studies using functional genomic, immunology, and bioinformatic approaches have provided novel insights into disease processes and protective immunity to chicken pathogens. In this review, we summarize recent published literature concerning the host response to Eimeria and Salmonella infections with emphasis on our studies using immunogenomic tools to investigate and characterize the mechanisms of avian immunity to these mucosal pathogens. The results clearly indicate that this immunogenomic approach will lead to increased understanding of immune responses to infectious agents that will enable the development of effective prevention strategies against mucosal pathogens.

Chicken cecum immune response to Salmonella enterica serovars of different levels of invasiveness

Day-old chicks are very susceptible to infections with Salmonella enterica subspecies. The gut mucosa is the initial site of host invasion and provides the first line of defense against the bacteria. To study the potential of different S. enterica serovars to invade the gut mucosa and trigger an immune response, day-old chicks were infected orally with Salmonella enterica serovar Enteritidis, S. enterica serovar Typhimurium, S. enterica serovar Hadar, or S. enterica serovar Infantis, respectively. The localization of Salmonella organisms in gut mucosa and the number of immune cells in cecum were determined by immunohistochemistry in the period between 4 h and 9 days after infection. Using quantitative real-time reverse transcription (RT)-PCR, mRNA expression of various cytokines, chemokines, and inducible nitric oxide synthase (iNOS) was examined in cecum. As a result, all S. enterica serovars were able to infect epithelial cells and the lamina propria. Notably, serovar Enteritidis showed the highest invasiveness of lamina propria tissue, whereas serovars Typhimurium and Hadar displayed moderate invasiveness and serovar Infantis hardly any invasion capabilities. Only a limited number of bacteria of all serovars were found within intestinal macrophages. Elevated numbers of granulocytes, CD8+ cells, and TCR1+ cells and mRNA expression rates for interleukin 12 (IL-12), IL-18, tumor necrosis factor alpha factor, and iNOS in cecum correlated well with the invasiveness of serovars in the lamina propria. In contrast, changes in numbers of TCR2+ and CD4+ cells and IL-2 mRNA expression seemed to be more dependent on infection of epithelial cells. The data indicate that the capability of Salmonella serovars to enter the cecal mucosa and invade lower regions affects both the level and character of the immune response in tissue.

Immunological and gene expression responses to a Salmonella infection in the chicken intestine

Besides infection in humans, Salmonella enteritidis can also cause serious illness in young chickens. However, the genetic and immunological parameters important for the disease in chickens are not well characterized. In this study, processes in the chicken intestine in response to a Salmonella infection were investigated in two different chicken lines. One-day-old chickens were orally infected with Salmonella. T-cell subpopulations, phagocytic properties of intestinal mononuclear cells and RNA expression levels of the jejunum were investigated. The two chicken lines differed in the amount of cfu in the liver and growth retardation after the infection. Differences in phagocytic activity of intestinal mononuclear cells were found between control and Salmonella infected chickens. The number of CD4+ T-cells of the intestine decreased after the Salmonella infection in one chicken line, while the number of CD8+ T-cells increased in both chicken lines, but the time post infection of this increase differed between the lines. In one chicken line the expression levels of the genes carboxypeptidase M and similar to ORF2 decreased after the Salmonella infection, which might be related to a decrease in the amount of macrophages. With the microarray, ten genes were found that were regulated in only one of the chicken lines, while we found six genes regulated in response to the infection in both chicken lines. So differences in genetic background of the chickens influence the intestinal host response of the Salmonella infection as observed by phagocytic activity, gene expression and changes in the number of T-cell subpopulations and macrophages.

Circulating gamma delta T cells in response to Salmonella enterica serovar enteritidis exposure in chickens

gammadelta T cells are considered crucial to the outcome of various infectious diseases. The present study was undertaken to characterize gammadelta (T-cell receptor 1(+) [TCR1(+)]) T cells phenotypically and functionally in avian immune response. Day-old chicks were orally immunized with Salmonella enterica serovar Enteritidis live vaccine or S. enterica serovar Enteritidis wild-type strain and infected using the S. enterica serovar Enteritidis wild-type strain on day 44 of life. Between days 3 and 71, peripheral blood was examined flow cytometrically for the occurrence of gammadelta T-cell subpopulations differentiated by the expression of T-cell antigens. Three different TCR1(+) cell populations were found to display considerable variation regarding CD8alpha antigen expression: (i) CD8alpha(+high) TCR1(+) cells, (ii) CD8alpha(+dim) TCR1(+) cells, and (iii) CD8alpha(-) TCR1(+) cells. While most of the CD8alpha(+high) TCR1(+) cells expressed the CD8alphabeta heterodimeric antigen, the majority of the CD8alpha(+dim) TCR1(+) cells were found to express the CD8alphaalpha homodimeric form. After immunization, a significant increase of CD8alphaalpha(+high) gammadelta T cells was observed within the CD8alpha(+high) TCR1(+) cell population. Quantitative reverse transcription-PCR revealed reduced interleukin-7 receptor alpha (IL-7Ralpha) and Bcl-x expression and elevated IL-2Ralpha mRNA expression of the CD8alphaalpha(+high) gammadelta T cells. Immunohistochemical analysis demonstrated a significant increase of CD8alpha(+) and TCR1(+) cells in the cecum and spleen and a decreased percentage of CD8beta(+) T cells in the spleen after Salmonella immunization. After infection of immunized animals, immune reactions were restricted to intestinal tissue. The study showed that Salmonella immunization of very young chicks is accompanied by an increase of CD8alphaalpha(+high) gammadelta T cells in peripheral blood, which are probably activated, and thus represent an important factor for the development of a protective immune response to Salmonella organisms in chickens.

Spreading of Salmonella enteritidis in the cecum of chickens

Adhesion and colonization of high (2 x 10(8) CFU) and low doses (2 x 10(2) CFU) of Salmonella enteritidis (phage type 4) was determined in the ceca collected 6 h-4 weeks after inoculation (pi), of 1-d-old White Plymouth Rock orally-inoculated chickens. S. enteritidis was associated with the epithelial surface of the villi in the low-dose group 18 h-7 d pi, the penetration in the cecal lamina propria was observed on day 1 and 10 pi. In the high-dose group, adhesion and colonization was observed in all birds killed 6 h-14 d pi; penetration of the bacteria into the cecal lamina propria was seen 1-21 d pi. Large numbers of macrophage-like cells containing S. enteritidis were observed in the cecal lamina propria on days 3-21 pi. Colonization and migration by S. enteritidis in the intestinal tract of chickens was shown to be dose dependent.

T lymphocyte subpopulations and B lymphocyte cells in caecum and spleen of chicks infected with Salmonella enteritidis

The effect of low and high doses of Salmonella enteritidis PT4 (SE) on immunocompetent cells in caecum and spleen of one-day-old chicks was investigated. Subsets of T lymphocytes positive for CD3, CD4, CD8 and B lymphocytes (Bu1b-positive cells) were counted in the caecum after immunohistochemical staining and the relative percentage of these cells in the spleen was analysed using a FACScan cytometer on days 7, 10, 14, 21, and 27 post-inoculation (pi). In the low dose group, the number of CD3+ and CD4+ cells in the caecum had significantly increased at day 10 pi. Both CD8+ and Bu1b+ cells were significantly higher on day 14 pi in this group. In the high-dose group, the number of CD4+ cells had significantly increased at day 7 pi. CD3+, CD8+, and Bu1b+ cells showed prolonged proliferation at days 7 up to 21 pi. Splenic lymphocytes demonstrated significant changes only in the high dose group. The percentage of splenic CD4+ cells was decreased at day 7 pi. A decrease in CD3+ and CD8+ cells was found at day 14 pi in this group.

Differential effects of age on chicken heterophil functional activation by recombinant chicken interleukin-2

Interleukin-2 (IL-2) exercises an array of biological effects on many cells including the functional activation of cells of the innate immune response. Heterophils, the avian equivalent of the neutrophil, function as professional phagocytes to aid in regulation of innate host defenses. The objective of the present studies was to examine the effects of recombinant chicken IL-2 (rChIL-2) on functional activities of heterophils from chickens during the first 3 weeks after hatch. Peripheral blood heterophils were isolated and incubated with either COS cell-derived rChIL-2 or supernatants from mock-transfected COS cells. rChIL-2 had no effect on the functional activities of heterophils from day-of-hatch chickens, but significantly increased the phagocytosis and bactericidal activity of heterophils from 7- and 14-day-old chickens. rChIL-2 induced no direct stimulation of the respiratory burst by heterophils, but primed heterophils from 7- and 14-day-old birds for an enhanced respiratory burst in response to phorbol ester stimulation. Lastly, rChIL-2 had neither direct nor priming effects on heterophil degranulation. The enhancing effects on heterophil functional activity by rChIL-2 were abated by a neutralizing anti-chicken IL-2 mAb and were therefore specific for this cytokine. These results show that rChIL-2 can directly activate chicken heterophils to exert effector functions, and that heterophil activation by rChIL-2 is also an age-dependent event.