Inhibition of Eimeria tenella replication after recombinant IFN-gamma activation in chicken macrophages, fibroblasts and epithelial cells

Study on the alleviative effect of Lactobacillus plantarum on Eimeria falciformis infection

Coccidia of the genus Eimeria are specialized intracellular parasitic protozoa that cause severe coccidiosis when they infect their hosts. Animals infected with Eimeria develop clinical symptoms, such as anorexia, diarrhea, and hematochezia, which can even cause death. Although the current preferred regimen for the treatment of coccidiosis is antibiotics, this treatment strategy is limited by the ban on antibiotics and the growing problem of drug resistance. Therefore, the exploration of alternative methods for controlling coccidiosis has attracted much attention. Lactobacillus plantarum has been shown to have many beneficial effects. In this study, L. plantarum M2 was used as a research object to investigate the effect of L. plantarum on intestinal inflammation induced by infection with Eimeria falciformis in mice by detecting indicators, such as oocyst output, serum cytokines, and the intestinal microbiota. Compared with that in the infection group, the percent weight loss of the mice that were administered with L. plantarum M2 was significantly reduced (P < 0.05). Supplemented L. plantarum M2 and probiotics combined with diclazuril can reduce the total oocyst output significantly (P < 0.05, P < 0.001). L. plantarum M2 had outstanding performance in maintaining intestinal barrier function, and the levels of the mucin MUC1 and the tight junction protein E-cadherin were significantly elevated (P < 0.01, P < 0.05). Studies have shown that probiotic supplementation can alleviate adverse reactions after infection and significantly improve intestinal barrier function. In addition, probiotics combined with diclazuril could optimize the partial efficacy of diclazuril, which not only enhanced the effect of antibiotics but also alleviated their adverse effects. This study expands the application of probiotics, provides new ideas for alternative strategies for coccidia control, and suggests a basis for related research on lactobacilli antagonizing intracellular pathogen infection.IMPORTANCECoccidia of the genus Eimeria are specialized intracellular parasitic protozoa, and the current preferred regimen for the treatment of coccidiosis is antibiotics. However, due to antibiotic bans and drug resistance, the exploration of alternative methods for controlling coccidiosis has attracted much attention. In this work, we focused on Lactobacillus plantarum M2 and found that probiotic supplementation can alleviate adverse reactions after infection and improve intestinal barrier function. This study proposes the possibility of using lactic acid bacteria to control coccidiosis, and its potential mechanism needs further exploration.

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

Introduction

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

Objective

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

Methods

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

Results

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

Conclusion

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

Transcriptional changes in LMH cells induced by Eimeria tenella rhoptry kinase family protein 17

Though a number of Eimeria tenella rhoptry kinase family proteins have been identified, little is known about their molecular functions. In the present study, the gene fragment encoding the matured peptide of E. tenella rhoptry kinase family protein 17 (EtROP17) was used to construct a recombinant vector, followed by transfection into leghorn male hepatoma (LMH) cells. Then, the transcriptional changes in the transfected cells were determined by RNA-seq. The expression of EtROP17 in LMH cells was validated by both Western blot and indirect immunofluorescence analysis. Our analysis showed that EtROP17 altered the expression of 309 genes (114 downregulated genes and 195 upregulated genes) in LMH cells. The quantitative real-time polymerase chain reaction (qRT-PCR) results of the selected differentially expressed genes (DEGs) were consistent with the RNA-seq data. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that DEGs were significantly enriched in nine pathways, such as toll-like receptor signaling pathway, ECM-receptor interaction, intestinal immune network for IgA production and focal adhesion. These findings reveal several potential roles of EtROP17, which contribute to understanding the molecular mechanisms underlying the host-parasite interplay.

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.

Dual RNA-Seq transcriptome analysis of chicken macrophage-like cells (HD11) infected in vitro with Eimeria tenella

The study aimed to monitor parasite and host gene expression during the early stages of Eimeria tenella infection of chicken cells using dual RNA-Seq analysis. For this, we used chicken macrophage-like cell line HD11 cultures infected in vitro with purified E. tenella sporozoites. Cultures were harvested between 2 and 72 h post-infection and mRNA was extracted and sequenced. Dual RNA-Seq analysis showed clear patterns of altered expression for both parasite and host genes during infection. For example, genes in the chicken immune system showed upregulation early (2–4 h), a strong downregulation of genes across the immune system at 24 h and a repetition of early patterns at 72 h, indicating that invasion by a second generation of parasites was occurring. The observed downregulation may be due to immune self-regulation or to immune evasive mechanisms exerted by E. tenella. Results also suggested pathogen recognition receptors involved in E. tenella innate recognition, MRC2, TLR15 and NLRC5 and showed distinct chemokine and cytokine induction patterns. Moreover, the expression of several functional categories of Eimeria genes, such as rhoptry kinase genes and microneme genes, were also examined, showing distinctive differences which were expressed in sporozoites and merozoites.

Apicomplexan co-infections impair with phagocytic activity in avian macrophages

Mixed infections of Toxoplasma gondii and Eimeria tenella are likely to occur frequently due to the high prevalence of both pathogens in free-ranging chickens. In this study, we investigated the co-occurrence of the two parasites in the same immune-competent host cell towards altered patterns of parasite-host interactions. Chicken blood monocyte-derived macrophages were co-infected with T. gondii RH tachyzoites and E. tenella Houghton sporozoites in vitro for 24 h. Through monitoring the uptake of pH-sensitive pHrodo™ Zymosan BioParticles ("Zymosan") by macrophages, we created a three-dimensional model and to analyze quantitatively phagocytosis using confocal laser scanning microscopy. Assessments of parasite populations were performed by qPCR at 2, 6, 12, and 24 h post-infection (hpi). At 6 hpi, phagocytosis was inhibited in the E. tenella-infected cultures while no inhibition of phagocytosis was observed due to T. gondii. Phagocytosis activity revealed more complex interactions during co-infection. At 12 and 24 hpi, phagocytosis response to "Zymosan" was distinctly weaker in co-infected cells than in all other groups except for cells mono-infected with high doses of E. tenella at 24 hpi. By qPCR, significantly reduced numbers of both intracellular parasites were recorded (10-fold) in all infected groups at 2 hpi. At 12 hpi, the T. gondii population reached lowest values but dramatically increased by 24 hpi. Our data confirm that macrophage phagocytosis is involved in the control of invasion by apicomplexan parasites in chicken which particularly applies to E. tenella infection and it was able to be altered by the co-existing parasites.

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.

Mutual interactions of the apicomplexan parasites Toxoplasma gondii and Eimeria tenella with cultured poultry macrophages

BACKGROUND

Toxoplasma gondii and Eimeria tenella are two common parasites in poultry. Mixed infections are likely to occur frequently in chickens due to the high prevalence of both pathogens. In this study, we investigate the co-occurrence of the two pathogens in the same immunocompetent host cell population towards potential parasite-parasite as well as altered patterns of parasite-host interactions.

METHODS

Primary macrophages from chicken blood were co-infected in vitro with T. gondii tachyzoites (RH strain) and E. tenella sporozoites (Houghton strain) for 72 h. Morphological observations by light microscopy and assessments of parasite replication by quantitative real-time PCR (qPCR) were performed at 24, 48 and 72 h post-infection (hpi). Six host cell immune factors previously linked to T. gondii or E. tenella infection were selected for gene expression analysis in this study.

RESULTS

Distinct morphological changes of macrophages were observed during mixed infection at 24 hpi and immunological activation of host cells was obvious. Macrophage mRNA expression for iNOS at 48 hpi and for TNF-α at 72 hpi were significantly elevated after mixed infection. Distinct upregulation of IL-10 was also present during co-infection compared to Eimeria mono-infection at 48 and 72 hpi. At 72 hpi, the total number of macrophages as well as the number of both parasites decreased markedly. As measured by qPCR, E. tenella population tended to increase during T. gondii co-infection, while T. gondii replication was not distinctly altered.

CONCLUSIONS

Mutual interactions of T. gondii and E. tenella were observed in the selected co-infection model. The interactions are supposed to be indirect considering the observed changes in host cell metabolism. This study would thus help understanding the course of co-infection in chickens that may be relevant in terms of veterinary and zoonotic considerations.

Coccidiosis: recent advancements in the immunobiology of Eimeria species, preventive measures, and the importance of vaccination as a control tool against these Apicomplexan parasites

Coccidiosis, caused by parasites of the genus Eimeria, is probably the most expensive parasitic disease of poultry. Species of Eimeria are ubiquitous where poultry are raised and are known to cause drastic reductions in performance and induce mortality, thereby affecting the overall health status of poultry. Chemotherapy has been the predominant form of disease control for many years, even though vaccination is steadily gaining importance as a feasible control method. The objective of this review is to highlight recent advancements in understanding the role of host immunity against coccidiosis. In addition, pros and cons associated with chemotherapy and the role of vaccination as an increasingly popular disease control method are discussed. Finally, the role played by recombinant vaccines as a potential vaccination tool is highlighted. With interest growing rapidly in understanding host–parasite biology, recent developments in designing recombinant vaccines and potential epitopes that have shown promise are mentioned.

MOLECULAR CLONING, SEQUENCING, EXPRESSION AND BIOLOGICAL ACTIVITY OF GIANT PANDA (AILUROPODA MELANOLEUCA) INTERFERON-GAMMA

The giant panda (Ailuropoda melanoleuca) is an endangered species and indigenous to China. Interferon-gamma (IFN-γ) is the only member of type □ IFN and is vital for the regulation of host adapted immunity and inflammatory response. Little is known aboutthe FN-γ gene and its roles in giant panda.In this study, IFN-γ gene of Qinling giant panda was amplified from total blood RNA by RT-CPR, cloned, sequenced and analysed. The open reading frame (ORF) of Qinling giant panda IFN-γ encodes 152 amino acidsand is highly similar to Sichuan giant panda with an identity of 99.3% in cDNA sequence. The IFN-γ cDNA sequence was ligated to the pET32a vector and transformed into E. coli BL21 competent cells. Expression of recombinant IFN-γ protein of Qinling giant panda in E. coli was confirmed by SDS-PAGE and Western blot analysis. Biological activity assay indicated that the recombinant IFN-γ protein at the concentration of 4-10 µg/ml activated the giant panda peripheral blood lymphocytes,while at 12 µg/mlinhibited. the activation of the lymphocytes.These findings provide insights into the evolution of giant panda IFN-γ and information regarding amino acid residues essential for their biological activity.

Antigen-induced cytokine production in lymphocytes of Eimeria bovis primary and challenge infected calves

Cellular immune responses against Eimeria bovis are highly specific and a key factor for the development of protection against challenge infections. In this study we investigate the cellular immune responses of E. bovis primary and challenge infected calves stimulated in vitro by E. bovis merozoite I-antigen. Primary infection was accompanied by an increase of IFN-gamma and IL-2 gene transcription in whole blood samples, peaking during prepatency (8-12 days p.i.) and declining thereafter, whereas IL-4 gene transcription was induced predominantly in patency. IL-10 mRNA was not influenced by E. bovis infection. Both CD4+ and CD8+ T cells were identified as source of IFN-gamma gene transcripts, whilst IL-2 and IL-4 gene transcription was enhanced mainly in CD4+ T cells. Increased levels of IFN-gamma transcripts and protein were also found in lymphocytes isolated from ileocaecal lymph node biopsy 8 days p.i., and in cell culture supernatants obtained from antigen-stimulated peripheral blood mononuclear cells (PBMC) at days 8 and 12 p.i., respectively. Challenge infections of calves influenced neither IFN-gamma nor IL-2 gene transcription in peripheral blood or in lymph node-derived lymphocytes. In contrast, IL-4 gene transcription was increased in lymphocytes isolated from draining lymph nodes. Besides antigen-specific reactions we also found an infection-triggered induction of the non-specific activation state of PBMC in the course of primary infection as measured by the intracellular IFN-gamma and IL-4 content of phorbol-12-myristate-13-acetate/ionomycin-stimulated PBMC. This may represent a new mechanism of immune cells of E. bovis-infected calves contributing to ongoing immune reactions.

Immune-related gene expression in two B-complex disparate genetically inbred Fayoumi chicken lines following Eimeria maxima infection

To investigate the influence of genetic differences in the MHC on susceptibility to avian coccidiosis, M5.1 and M15.2 B-haplotype-disparate Fayoumi chickens were orally infected with live Eimeria maxima oocysts, and BW gain, fecal oocyst production, and expression of 14 immune-related genes were determined as parameters of protective immunity. Weight loss was reduced and fecal parasite numbers were lower in birds of the M5.1 line compared with M15.2 line birds. Intestinal intraepithelial lymphocytes from M5.1 chickens expressed greater levels of transcripts encoding interferon-gamma (IFN-gamma), interleukin-1beta (IL-1beta), IL-6, IL-8, IL-12, IL-15, IL-17A, inducible nitric oxide synthase, and lipopolysaccharide-induced tumor necrosis factor-alpha factor and lower levels of mRNA for IFN-alpha, IL-10, IL-17D, NK-lysin, and tumor necrosis factor superfamily 15 compared with the M15.2 line. In the spleen, E. maxima infection was associated with greater expression levels of IFN-gamma, IL-15, and IL-8 and lower levels of IL-6, IL-17D, and IL-12 in M5.1 vs. M15.2 birds. These results suggest that genetic determinants within the chicken MHC influence resistance to E. maxima infection by controlling the local and systemic expression of immune-related cytokine and chemokine genes.

Downregulation of the goat β-defensin-2 gene by IL-4 in caprine intestinal epithelial cells infected with Eimeria spp

Defensins are antimicrobial peptides that are produced by leukocytes and epithelial cells. Recent advances indicate that these peptides play an important role in innate immune responses. Nonetheless, the role of defensins in caprine eimeriosis remains unknown. Therefore, this study investigated the expression of a goat beta-defensin, named GBD-2 in caprine intestinal epithelial cells (CIEC) stimulated with recombinant bovine interferon-gamma (IFN-gamma) in the presence or absence of recombinant bovine interleukin-4 (IL-4) by a reverse transcriptase-polymerase chain reaction (RT-PCR) assay. GBD-2 mRNA was clearly expressed in IFN-gamma-stimulated CIEC. On the other hand, the direct addition of IL-4 showed no significant effect on GBD-2 expression in CIEC. However, when supernatants from peripheral blood mononuclear cells (PBMC) cultured with IL-4 were added to CIEC, the expression of GBD-2 decreased. To elucidate if IFN-gamma functions as a signaling molecule that facilitates the generation of GBD-2 against Eimeria spp. in goats, anti- IL-4 was added to PBMC from Eimeria-infected goats and levels of IFN-gamma in culture supernatants were determined by an enzyme-linked immunosorbent assay test. Results showed that IFN-gamma secretion increased when anti-IL-4 was added to PBMC. It then appears safe to suggest that IL-4 may be a further factor in the pathogenesis of goat coccidiosis and its induction may be part of an evasion strategy of the parasite to avoid pro-inflammatory responses.

Challenges in the successful control of the avian coccidia

Eimeria species infect livestock in a host-specific manner and are the cause of the disease, coccidiosis. Control of Eimeria species is essential and is currently dominated by chemotherapy; with vaccination using formulations of live wild-type or attenuated parasites an increasing option. A new generation of subunit, live-vector or DNA vaccination strategies is being sought and determining the identity of suitable antigens remains difficult. Some past and present methods of controlling avian coccidia are discussed briefly and we describe progress with a novel approach to identify immunoprotective antigens as vaccine candidates.

Changes in immune-related gene expression and intestinal lymphocyte subpopulations following Eimeria maxima infection of chickens

Coccidiosis, a major intestinal parasitic disease of poultry, induces a cell-mediated immune response against the etiologic agent of the disease, Eimeria. In the current study, the expression levels of gene transcripts encoding pro-inflammatory, Th1, and Th2 cytokines, as well as chemokines were measured in intestinal intraepithelial lymphocytes (IELs) after Eimeria maxima infection. In addition, changes in IEL numbers were quantified following E. maxima infection. Transcripts of the pro-inflammatory and Th1 cytokines IFN-gamma, IL-1beta, IL-6, IL-12, IL-15, IL-17, and IL-18 were increased 66- to 8 x 10(7)-fold following primary parasite infection. Similarly, mRNA levels of the Th2 cytokines IL-3, IL-10, IL-13, and GM-CSF were up-regulated 34- to 8800-fold, and the chemokines IL-8, lymphotactin, MIF, and K203 were increased 42- to 1756-fold. In contrast, IFN-alpha, TGF-beta4, and K60 transcripts showed no increased expression, and only the level of the Th2 cytokine IL-13 was increased following secondary E. maxima infection. Increases in intestinal T cell subpopulations following E. maxima infection also were detected. CD3(+), CD4(+), and CD8(+) cells were significantly increased at days 8, 6, and 7 post-primary infection, respectively, but only CD4(+) cells remained elevated following secondary infection. TCR1(+) cells exhibited a biphasic pattern following primary infection, whereas TCR2(+) cells displayed a single peak in levels. Taken together, these data indicate a global chicken intestinal immune response is produced following experimental Eimeria infection involving multiple cytokines, chemokines, and T cell subsets.

Genetic identification of antigens protective against coccidia

The Eimeria species, causative agents of the disease coccidiosis, are genetically complex protozoan parasites endemic in livestock. Drug resistance remains commonplace among the Eimeria, and alternatives to chemotherapeutic control are being sought. Vaccines based upon live formulations of parasites are effective, but production costs are high, stimulating demand for a recombinant subunit vaccine. The identity of antigens suitable for inclusion in such vaccines remains elusive. Selection of immunoprotective antigens of the Eimeria species as vaccine candidates based upon recognition by the host immune system has been unsuccessful, obscured by the considerable number of molecules that are immunogenic but not immunoprotective. This is a common problem which characterizes work with most eukaryotic parasites. The identification of a selective criterion to directly access genetic loci that encode immunoprotective antigens of Eimeria maxima using a mapping strategy based upon parasite genetics, immune selection and DNA fingerprinting promises to revolutionize the process of antigen discovery. Linkage analyses of DNA markers amplified from populations of recombinant parasites defined by an ability to escape parent-specific deleterious selection by strain-specific immunity and chemotherapy has revealed four discrete regions within the E. maxima genome linked to escape from a protective immune response. These regions now form the basis of detailed study to identify antigens as candidates for inclusion in future vaccination strategies.

Resistance to intestinal coccidiosis following DNA immunization with the cloned 3-1E Eimeria gene plus IL-2, IL-15, and IFN-gamma

A cloned Eimeria acervulina gene (3-1E) was used to vaccinate chickens in ovo against coccidiosis, both alone and in combination with genes encoding interleukin (IL)-1, IL-2, IL-6, IL-8, IL-15, IL-16, IL-17, IL-18, or interferon (IFN)-gamma. Vaccination efficacy was assessed by increased serum anti-3-1E antibody titers, reduced fecal oocyst shedding, and enhanced body weight gain following experimental infection with E. acervulina. When used alone, anti-3-1E antibody titers were transiently, but reproducibly, increased at 2 wk and 3 wk posthatching in a dose-dependent manner. Similarly, significantly reduced oocyst shedding and increased weight gain were observed at relatively high-dose 3-1E vaccinations (> or =25 microg/egg). Combined immunization with the 3-1E and IL-1, IL-2, IL-15, or IFN-gamma genes induced higher serum antibody responses compared with immunization with 3-1E alone. Following parasite infection, chickens hatched from embryos given the 3-1E gene plus the IL-2 or IL-15 genes displayed significantly reduced oocyst shedding compared with those given 3-1E alone, while 3-1E plus IL-15 or IFN-gamma significantly increased weight gain compared with administration of 3-1E alone. Taken together, these results indicate that in ovo immunization with a recombinant Eimeria gene in conjunction with cytokine adjuvants stimulates protective intestinal immunity against coccidiosis.

Chicken Primary Enterocytes: Inhibition ofEimeria tenellaReplication After Activation with Crude Interferon-γ Supernatants

A reproducible and original method for the preparation of chicken intestine epithelial cells from 18-day-old embryos for long-term culture was obtained by using a mechanical isolation procedure, as opposed to previous isolation methods using relatively high concentrations of trypsin, collagenase, or EDTA. Chicken intestine epithelial cells typically expressed keratin and chicken E-cadherin, in contrast to chicken embryo fibroblasts, and they increased cell surface MHC II after activation with crude IFN-gamma containing supernatants, obtained from chicken spleen cells stimulated with concanavalin A or transformed by reticuloendotheliosis virus. Eimeria tenella was shown to be able to develop until the schizont stage after 46 hr of culture in these chicken intestinal epithelial cells, but it was not able to develop further. However, activation with IFN-gamma containing supernatants resulted in strong inhibition of parasite replication, as shown by incorporation of [3H]uracil. Thus, chicken enterocytes, which are the specific target of Eimeria development in vivo, could be considered as potential local effector cells involved in the protective response against this parasite.

Immune modulation of the pulmonary hypertensive response to bacterial lipopolysaccharide (endotoxin) in broilers

The lungs of broilers are constantly challenged with lipopolysaccharide (LPS, endotoxin) that can activate leukocytes and trigger thromboxane A2 (TxA2)- and serotonin (5HT)-mediated pulmonary vasoconstriction leading to pulmonary hypertension. Among broilers from a single genetic line, some individuals respond to LPS with large increases in pulmonary arterial pressure, whereas others fail to exhibit any response to the same supramaximal dose of LPS. This extreme variability in the pulmonary hypertensive response to LPS appears to reflect variability in the types or proportions of chemical mediators released by leukocytes. Our research has confirmed that TxA2 and 5HT are potent pulmonary vasoconstrictors in broilers and that broilers hatched and reared together consistently exhibit pulmonary hypertension after i.v. injections of TxA2 or 5HT. Previous in vitro studies conducted using macrophages from different lines of chickens demonstrated innate variability in the LPS-stimulated induction of nitric oxide synthase (iNOS) followed by the onset of an LPS-refractory state. The NOS enzyme converts arginine to citrulline and nitric oxide (NO). It is known that NO produced by endothelial NOS serves as a key modulator of flow-dependent pulmonary vasodilation, and it is likely that NO generated by iNOS also contributes to the pulmonary vasodilator response. Accordingly, it is our hypothesis that the pulmonary hypertensive response to LPS in broilers is minimal when more vasodilators (NO, prostacyclin) than vasoconstrictors (TxA2, 5HT) are generated during an LPS challenge. Indeed, inhibiting NO production through pharmacological blockade of NOS with the inhibitor Nomega-nitro-L-arginine methyl ester modestly increased the baseline pulmonary arterial pressure and dramatically increased the pulmonary hypertensive response to LPS in all broilers evaluated. Innate differences in the effect of LPS on the pulmonary vasculature may contribute to differences in susceptibility of broilers to pulmonary hypertension syndrome (ascites).