Unique responses of the avian macrophage to different species of Eimeria

Krameria lappacea roots extract to rescue coccidiosis-mediated inflammation in the jejunum of C57BL/6 mice

Introduction

Coccidiosis is a protozoan disease caused by Eimeria species, which multiply in the intestinal tract and lead to severe inflammatory responses. While coccidiostats are available for control, resistance to these treatments has been confirmed, underscoring the need for new eco-friendly approaches. In recent years, natural plant sources have gained attention as effective alternatives for treating various parasitic diseases. Krameria lappacea has been used in traditional medicine due to its pharmacological properties. This study examined the effects of the aqueous methanolic extract of K. lappacea roots (KLRE) on jejunal inflammation and immune response in a murine model infected with Eimeria papillata.

Methods

Twenty-five male C57BL/6 mice were randomly divided into five groups. The first group received only distilled water, while the second group was administered 200 mg/kg of KLRE for 5 days. The third, fourth, and fifth groups were orally injected with 103 sporulated oocysts of the Eimeria parasite. For treatment, the fourth group received KLRE (200 mg/kg), and the fifth group received amprolium (120 mg/kg) orally for 5 days. All mice were euthanized on day 5 post-infection (p.i.), and blood samples and jejunum were collected. Investigations were conducted to assess oocyst shedding, cellular immune response, and the histological changes in the jejunum of the mice. Levels of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α were measured using an enzyme-linked immunosorbent assay (ELISA). Additionally, the mRNA expression of CXC motif chemokine ligand 10 (CXCL10), interferon-inducible gene 202b (IFi202b), and secreted phosphoprotein 1 (SPP-1) was analyzed using quantitative reverse transcription polymerase chain reaction (qRT-PCR).

Results

Our study demonstrated that mice infected with E. papillata produced an average of 5.387 × 106 ± 4.29 × 105 oocysts per gram of feces by day 5 post-infection. In contrast, the output was significantly reduced to 1.308 × 106 ± 1.36 × 105 oocysts per gram of feces in mice treated with KLRE. These findings suggest that the host immune response to the intracellular Eimeria parasite triggers inflammation and injury in the jejunum of the mice. This was evidenced by several factors: (i) an elevated inflammatory histological score, (ii) an increased cellular immune response characterized by neutrophils and lymphocytes, (iii) elevated protein levels of IL-1β, IL-6, and TNF-α, measured at approximately 13.67 ± 2.07, 78.98 ± 4.17, and 222.28 ± 10.18 pg/ml, respectively, and (iv) upregulated expression of the mRNA genes CXCL10, IFi202b, and SPP-1, which showed fold changes of approximately 2.83, 3.55, and 3.07-fold, respectively. Our study found that all parameters associated with the infection were significantly altered during treatment with KLRE.

Conclusion

Our data showed that KLRE treatment significantly reduced inflammation and histological damage in the jejunum caused by E. papillata infections.

Alternatives to antibiotics against coccidiosis for poultry production: the relationship between immunity and coccidiosis management – a comprehensive review

Avian coccidiosis is a protozoan infection caused by numerous Eimeria parasitic species and mainly affects the bird’s gastrointestinal tract and results in a reduction of the bird ‘ability to absorb nutrients, slower growth, with a higher mortality rate. According to recent research, immune-based treatments, such as dietary immunomodulating feed additives and recombinant vaccines, can help the hosts protect themselves from intracellular parasites and reduce inflammatory reactions caused by parasites. Coccidiosis control in the post-antiparasitic stage requires thoroughly investigation of the intricate relationships between the parasites, host defense system, enteroendocrine system, and gut microbiome contributing to coccidian infections. To produce a vaccine, it is crucial to explore the defense mechanism of the intestine’s immune machinery and to identify many effector molecules that act against intracellular parasites. Due to the massive usage of chemical anticoccidial drugs, coccidiosis developed resistant against most commonly used anticoccidials; therefore, numerous researches focused on the usage of safe natural anticoccidials such as probiotics, prebiotics, organic acids, and essential oils to counteract such resistance problem. This review describes how host immunity responds to coccidial infection in chickens and the use of some nonantiparasitic safe natural alternative controls to counter the disease. It would throw the light on the possibility of developing effective therapies against Eimeria to alleviate the detrimental effects of avian coccidiosis.

Citrus pectins impact the function of chicken macrophages

The restrictions on excessive use of antimicrobials in the poultry industry have led to the search for alternative strategies including nutritional interventions to enhance gut health with the ultimate aim to prevent gut infections. Pectins as prebiotics have shown beneficial effects on gut health in humans and mice by improving the gut barrier function, altering the gut microbiota, and by modulating the gut immune response. However, little is known about immunomodulatory properties of pectins in chickens. The present in vitro study assessed the effect of three pectins (SPE6, SPE7, SPE8) differing in methyl esterification, on responsiveness of the chicken macrophage cell line HD11 cells and primary monocyte derived macrophage from the blood, through interaction with chicken TLRs. All three pectins increased gene expression of iNOS and IL10 in chicken macrophages. Differences in immunomodulatory activity between the three pectins were observed in other assays. The low methoxyl pectin (SPE8) interacted with TLR4 leading to the production of NO, but also to increased phagocytosis of E. coli, while high methoxyl pectins SPE6 and SPE7 did not activate TLR4. All three pectins were able to attenuate PAM3CSK4 induced activation of chicken macrophages as measured by decreased NO production and phagocytosis. Additional studies using ITC and flow cytometry suggest that the inhibiting properties of pectins (SPE6, SPE7) on macrophages are due to pectins occupying TLR2 and blocking PAM3CSK4 to activate chicken macrophages, whereas SPE8 actually binds to the TLR2 ligand and that way attenuates the PAM3CSK4 induced activation. Based on these immunomodulatory properties observed in this study, these pectins may in the future be suitable as feed additive for the treatment and prevention of inflammatory disorders in poultry.

Krameria lappacea root extract's anticoccidial properties and coordinated control of CD4 T cells for IL-10 production and antioxidant monitoring

Introduction

Recently, the use of botanicals as an alternative to coccidiostats has been an appealing approach for controlling coccidiosis. Therefore, this study was conducted to evaluate the potential role of aqueous methanolic extract (200 mg/kg) of Krameria lappacea (roots) (KLRE) against infection induced by Eimeria papillata.

Methods

A total of 25 male C57BL/6 mice were divided into five groups (I, II, III, IV, and V). On 1st day of the experiment, all groups except groups I (control) and II (non-infected-treated group with KLRE), were inoculated orally with 103 sporulated E. papillata oocysts. On the day of infection, group IV was treated with KLRE. Group V served as an infected-treated group and was treated with amprolium (coccidiostat).

Results

Treatment with extract and coccidiostat was continued for five consecutive days. While not reaching the efficacy level of the reference drug (amprolium), KLRE exhibited notable anticoccidial activity as assessed by key criteria, including oocyst suppression rate, total parasitic stages, and maintenance of nutrient homeostasis. The presence of phenolic and flavonoid compounds in KLRE is thought to be responsible for its positive effects. The Eimeria infection increased the oxidative damage in the jejunum. KLRE treatment significantly increased the activity of catalase and superoxide dismutase. On the contrary, KLRE decreased the level of malondialdehyde and nitric oxide. Moreover, KLRE treatment decreased macrophage infiltration in the mice jejunal tissue, as well as the extent of CD4 T cells and NFkB. E. papillata caused a state of systemic inflammatory response as revealed by the upregulation of inducible nitric oxide synthase (iNOs)-mRNA. Upon treatment with KLRE, the activity of iNOs was reduced from 3.63 to 1.46 fold. Moreover, KLRE was able to downregulate the expression of pro-inflammatory cytokines interferon-γ, nuclear factor kappa B, and interleukin-10 -mRNA by 1.63, 1.64, and 1.38 fold, respectively. Moreover, KLRE showed a significant reduction in the expression of IL-10 protein level from 104.27 ± 8.41 pg/ml to 62.18 ± 3.63 pg/ml.

Conclusion

Collectively, K. lappacea is a promising herbal medicine that could ameliorate the oxidative stress and inflammation of jejunum, induced by E. papillata infection in mice.

Microbiota promotes recruitment and pro-inflammatory response of caecal macrophages during E. tenella infection

BACKGROUND

Eimeria genus belongs to the apicomplexan parasite phylum and is responsible for coccidiosis, an intestinal disease with a major economic impact on poultry production. Eimeria tenella is one of the most virulent species in chickens. In a previous study, we showed a negative impact of caecal microbiota on the physiopathology of this infection. However, the mechanism by which microbiota leads to the physiopathology remained undetermined. Macrophages play a key role in inflammatory processes and their interaction with the microbiota during E. tenella infection have never been investigated. We therefore examined the impact of microbiota on macrophages during E. tenella infection. Macrophages were monitored in caecal tissues by immunofluorescence staining with KUL01 antibody in non-infected and infected germ-free and conventional chickens. Caecal cells were isolated, stained, analyzed and sorted to examine their gene expression using high-throughput qPCR.

RESULTS

We demonstrated that microbiota was essential for caecal macrophage recruitment in E. tenella infection. Furthermore, microbiota promoted a pro-inflammatory transcriptomic profile of macrophages characterized by increased gene expression of NOS2, ACOD1, PTGS2, TNFα, IL1β, IL6, IL8L1, IL8L2 and CCL20 in infected chickens. Administration of caecal microbiota from conventional chickens to germ-free infected chickens partially restored macrophage recruitment and response.

CONCLUSIONS

Taken together, these results suggest that the microbiota enhances the physiopathology of this infection through macrophage recruitment and activation. Consequently, strategies involving modulation of the gut microbiota may lead to attenuation of the macrophage-mediated inflammatory response, thereby limiting the negative clinical outcome of the disease.

Interplay between Eimeria acervulina and Cryptosporidium parvum during In Vitro Infection of a Chicken Macrophage Cell Line (HD11)

BACKGROUND

Eimeria acervulina is a frequent intestinal pathogen of chickens, causing economic impact on the poultry industry. Cryptosporidium parvum is a neglected parasite in chickens. However, because of its zoonotic potential, poultry cryptosporidiosis may pose a risk to public health. Little is known about the parasite-host interactions during coinfection with both parasites. In this study, we investigated the possible interactions during in vitro coinfection of E. acervulina and C. parvum in a chicken macrophage cell line (HD11).

METHODS

HD11 cells were inoculated with E. acervulina and C. parvum sporozoites and incubated 2, 6, 12, 24, and 48 h post infection (hpi). Mono-infections for each parasite were also investigated. Real-time PCR was used to quantify parasite replication. Additionally, macrophage mRNA expression levels of IFN-γ, TNF-α, iNOS, and IL-10 were measured.

RESULTS

For both parasites, multiplication was, in most groups, lower in the coinfection group (COIG) compared with mono-infections. However, at 6 hpi, the number of C. parvum copies was higher in co-infections. Intracellular replication started to decrease from 12 hpi onward, and it was almost undetectable by 48 hpi in all groups. Infections resulted in low expression of all cytokines, except at 48 hpi.

CONCLUSIONS

Infection of avian macrophages with both E. acervulina and C. parvum seemed to hinder intracellular replication for both parasites in comparison to mono-infection. A clear reduction in intracellular parasites from 12 hpi onward details the important role potentially played by macrophages in host control of these parasites.

Dietary tea tree (Melaleuca alternifolia) essential oil as alternative to antibiotics alleviates experimentally induced Eimeria tenella challenge in Japanese quails

Coccidiosis is one of the most common infectious diseases seen in Japanese quails. The current study was conducted to evaluate the impact of tea tree essential oil (TTEO) on growth performance and intestinal health of quails in response to Eimeria tenella challenge. A total of 250 Japanese quails were divided into five treatments: untreated uninfected (negative control); untreated infected (positive control); infected + Amprolium; infected and 1% TTEO; infected and 2% TTEO. Except negative control, all groups were orally dosed with 5 × 10⁴ sporulated oocysts of E. tenella. The results revealed that supplementation of 1% TTEO and treatment of amprolium improved feed intake, weight gain and feed conversion ratio in infected quails compared to the positive control. Similarly, lesion score and mortality was significantly (p < 0.01) reduced in quails supplemented with 2% TTEO and amprolium treated birds. Moreover, oocysts counts and histological features of caecum in infected birds were reversed in 1% TTEO and amprolium treatment. The histological findings of amprolium and 1% TTEO supplemented quails showed intact intestinal villi with mild sloughed epithelium. In conclusion, 1% TTEO can be safely used to control coccidiosis in Japanese quails as natural effective compound.

Characterization of vaccine-induced immune responses against coccidiosis in broiler chickens

Coccidiosis, caused by Eimeria protozoan species, is an economically important enteric disease of poultry. Although commercial live vaccines are widely used for disease control, the vaccine-induced protective immune mechanisms are poorly characterized. The present study used a commercial broiler vaccine containing a mixture of E. acervulina, E. maxima, and E. tenella. One-day-old chicks were vaccinated by spray followed by a challenge at 21 days of age with a mixture of wild type Eimeria species via oral gavage. Oocyst shedding, immune gene expression and cellular responses in the spleen and cecal tonsils were measured at pre- (days 14 and 21) and post-challenge (days 24, 28 and 35) time points. Results showed that the oocyst counts were significantly reduced in the vaccinated chickens at post-challenge compared to unvaccinated control group. While the vaccinated birds had a significantly increased toll-like receptor (TLR) 21 gene expression at pre-challenge, the transcription of interferon (IFN)γ, Interleukin (IL)-12 and CD40 genes in spleen and cecal tonsils of these birds was significantly higher at post-challenge compared to unvaccinated chickens. Cellular immunophenotyping analysis found that vaccination led to increased frequency of macrophages and activated T cells (CD8⁺CD44⁺ and CD4⁺CD44⁺) in the spleen and cecal tonsils at post-challenge. Furthermore, in vitro stimulation of chicken macrophages (MQ-NCSU cells) with purified individual species of E. acervulina, E. maxima, and E. tenella showed a significantly increased expression of TLR21, TLR2 and IFNγ genes as well as nitric oxide production. Collectively, these findings suggest that TLR21 and TLR2 may be involved in the immune cell recognition of Eimeria parasites and that the vaccine can induce a robust macrophage activation leading to a T helper-1 dominated protective response at both local and systemic lymphoid tissues.

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

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

Relationship between Eimeria tenella associated-early clinical signs and molecular changes in the intestinal barrier function

The major clinical signs of coccidiosis in chickens due to Eimeria parasite are diarrhea and bloody feces. Previous studies showed that the impairment of the intestinal epithelial barrier and the elevation of the intestinal permeability are causes of clinical signs associated with coccidia challenges. Nevertheless, the information about molecular changes of the epithelial barrier at the early stage of the infection with a specific Eimeria species has not been mentioned. Hence, this study aims to elucidate the temporal relationships between epithelial barrier conditions and clinical signs in chickens infected with Eimeria tenella over the time from the earliest stages of infection. White Leghorn chickens were inoculated with 1 × 10⁴ oocysts of E. tenella. Thereafter the chickens were monitored for their daily clinical signs through observation, and between 5 dpi to 10 dpi, feces were collected for oocysts counting. Chickens were then administrated with fluorescein isothiocyanate-dextran (FITC-d) for gastrointestinal permeability test and tissues were collected each day for histopathological observation and total RNA extraction. Finally, the mRNA expression levels of the tight and adherens junction genes and cytokine genes were evaluated using the quantitative real-time polymerase chain reaction (qRT-PCR). In this study, clinical signs such as diarrhea and bloody feces were observed concurrently from 3 to 8 dpi. Histopathology changes such as severe inflammation, hemorrhage, and epithelial desquamation were identified in the cecum specimens. The FITC-d level in the E. tenella-infected group was significantly higher than in the control group. In the infected group, the expression of claudin-2 gene was also upregulated, whereas the expressions of claudin-3 and E-cadherin genes were decreased as compared to the control group. These results implied that clinical signs of avian coccidiosis were associated with the intestinal barrier disruption via changes in expression levels of claudins and E-cadherin at the intestine.

Reduction of macrophages by carrageenan decreases oocyst output and modifies local immune reaction in chick cecum with Eimeria tenella

This study aimed to evaluate the disease severity and local immune responses in macrophage-depleted chicks with Eimeria tenella. Macrophages were reduced by intraperitoneal injection of a carrageenan solution at 12, 13, and 16 days old, whereas the control group received intraperitoneal phosphate-buffered saline. Both chick groups were orally inoculated with E. tenella sporulated oocysts at 14 days old. Feces were collected daily, which were then quantified for oocysts. The chicks were sacrificed on day 5, and the ceca were collected for histopathological observation. The gene expression levels were measured using real-time quantitative reverse transcription-polymerase chain reaction. Macrophage-depleted chicks have been observed to shed a significantly reduced number of fecal oocysts compared to the infected control group. The parasite burden score in cecum specimens of macrophage-depleted chicks was significantly lower than those of infected control on day 5 after infection. Furthermore, macrophage reduction yielded significantly lower cecum histopathological scores and CD4 expression than those of the infected control group. The expression of interleukin (IL)-18, IL-22, interferon-γ, and inducible nitric oxide synthase was also noted to be significantly upregulated in both infected control and macrophage-depleted chicks compared to uninfected chicks. IL-4, IL-13, IL-17, and perforin expressions were also higher with macrophage depletion than in both control groups. These results suggest that macrophages serve as an invasive gate or a transporting vehicle to the site of first merogony. Furthermore, mononuclear phagocytes may play an important role in local immune responses, thus contributing to parasite development during early E. tenella infection.

Efficacy of immunization compared to an anticoccidial drug combination in the management of challenged coccidiosis in Japanese quail

This study was carried out to compare the efficacy of immunization, by a low-dose of live sporulated oocysts of different Eimeria species separately, with the efficacy of amprolium plus sulphaquinoxaline in the management of challenged coccidiosis in Japanese quail. Dropping samples were collected and sent to the laboratory for isolation and identification of Eimeria species. Three Eimeria species were isolated and identified as E. bateri, E. uzura, and E. tsunodai. Single oocyst isolation and propagation were done successfully for each species. For the experimental trial, Japanese quails were divided into 11 groups of thirty birds each and given different treatments. The assessment of each treatment relied on clinical signs, mortality, lesion score, oocyst output, weight gain, feed conversion ratio, and hematological parameters. The results revealed that immunization, with any isolated species, gave the best results regarding all tested parameters. Thus, we concluded that immunization by a low-dose of live sporulated oocysts was better compared to amprolium plus sulphaquinoxaline in the management of coccidiosis in Japanese quail.

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.

Modulatory Effect of Dietary Polyunsaturated Fatty Acids on Immunity, Represented by Phagocytic Activity

Lately, dietary polyunsaturated fatty acids (PUFAs) have shown substantial importance in human and animal nutrition, especially those of the n-3 group. Development and optimal functioning of the immune system are directed affected by diet. These dietary fatty acids have an important impact on the health and immune competence of various species including human beings. They are essential for the modulation of immune responses in health and disease. Fatty acid composition of immune cells can be modulated by the action of dietary fats and the outcomes in the composition can produce functional effects on reactivity and functioning of immune cells in a short period. There are several mechanisms involved in impacting dietary fatty acids on immune function; however, lipid mediator synthesis from PUFAs is of great importance in terms of inflammation. The objectives of this article are reviewing studies on the impact of PUFA in the diet on phagocytosis of chickens, murine, rats, ruminants, and humans. It also sheds light on the possible mechanism by which this immunomodulation occurs.

Mucosal Delivery of a Self-destructing Salmonella-Based Vaccine Inducing Immunity Against Eimeria

A programmed self-destructive Salmonella vaccine delivery system was developed to facilitate efficient colonization in host tissues that allows release of the bacterial cell contents after lysis to stimulate mucosal, systemic, and cellular immunities against a diversity of pathogens. Adoption and modification of these technological improvements could form part of an integrated strategy for cost-effective control and prevention of infectious diseases, including those caused by parasitic pathogens. Avian coccidiosis is a common poultry disease caused by Eimeria. Coccidiosis has been controlled by medicating feed with anticoccidial drugs or administering vaccines containing low doses of virulent or attenuated Eimeria oocysts. Problems of drug resistance and nonuniform administration of these Eimeria resulting in variable immunity are prompting efforts to develop recombinant Eimeria vaccines. In this study, we designed, constructed, and evaluated a self-destructing recombinant attenuated Salmonella vaccine (RASV) lysis strain synthesizing the Eimeria tenella SO7 antigen. We showed that the RASV lysis strain χ11791(pYA5293) with a ΔsifA mutation enabling escape from the Salmonella-containing vesicle (or endosome) successfully colonized chicken lymphoid tissues and induced strong mucosal and cell-mediated immunities, which are critically important for protection against Eimeria challenge. The results from animal clinical trials show that this vaccine strain significantly increased food conversion efficiency and protection against weight gain depression after challenge with 105E. tenella oocysts with concomitant decreased oocyst output. More importantly, the programmed regulated lysis feature designed into this RASV strain promotes bacterial self-clearance from the host, lessening persistence of vaccine strains in vivo and survival if excreted, which is a critically important advantage in a vaccine for livestock animals. Our approach should provide a safe, cost-effective, and efficacious vaccine to control coccidiosis upon addition of additional protective Eimeria antigens. These improved RASVs can also be modified for use to control other parasitic diseases infecting other animal species.

Impact of dietary chitosan oligosaccharide and its effects on coccidia challenge in broiler chickens

1. Two experiments were conducted, the first to determine the optimum inclusion of chitosan oligosaccharide (COS) in broiler diets to support growth performance, digestive functions, intestinal morphology, and immune organs. The second experiment evaluated the immune-protective properties of COS on broiler chickens during coccidia challenge (CC).2. Experiment 1 investigated the effect of graded dietary concentration of COS in the diets of broiler chickens using eight cage replicates for each of the six diets. A corn-soybean meal-based diet was used as the basal diet and supplemented with 0.0, 0.5, 1.0, 1.5, 2.0, or 2.5 g of COS/kg feed to form the six treatments.3. The diet supplemented with 1.0 g COS/kg of feed provided the optimal inclusion level for broiler chickens regarding body weight (BW) gain, jejunal villus height, villus height to crypt depth ratio, and ileal energy digestibility at d 22 of age.4. Experiment 2 investigated the immune-protective properties of COS in broiler chickens during CC. A total of 224 male broiler chicks were randomly assigned to eight replicate cages in a 2 × 2 factorial arrangement of treatments with two COS concentrations (0 or 1 g of COS/kg of diet), with or without CC.5. On d 18 of age, birds in the CC group received twice the recommended coccidia vaccine dose of 30 doses/kg BW.6. Coccidia challenge reduced (P < 0.05) and dietary COS increased (P < 0.05) BW gain, and feed intake. Dietary COS mitigated (P < 0.05) the CC-induced effects on gain:feed. Dietary COS supplementation attenuated the CC-induced effects (P < 0.05) on the expression of occludin genes.7. In conclusion, dietary COS improved performance, and the immune-related beneficial impact of COS supplementation was associated with reduced expression of pro-inflammatory cytokine genes.

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.

Expression of host defense peptides in the intestine of Eimeria-challenged chickens

Avian coccidiosis is caused by the intracellular protozoan Eimeria, which produces intestinal lesions leading to weight gain depression. Current control methods include vaccination and anticoccidial drugs. An alternative approach involves modulating the immune system. The objective of this study was to profile the expression of host defense peptides such as avian beta-defensins (AvBDs) and liver expressed antimicrobial peptide 2 (LEAP2), which are part of the innate immune system. The mRNA expression of AvBD family members 1, 6, 8, 10, 11, 12, and 13 and LEAP2 was examined in chickens challenged with either E. acervulina, E. maxima, or E. tenella. The duodenum, jejunum, ileum, and ceca were collected 7 d post challenge. In study 1, E. acervulina challenge resulted in down-regulation of AvBD1, AvBD6, AvBD10, AvBD11, AvBD12, and AvBD13 in the duodenum. E. maxima challenge caused down-regulation of AvBD6, AvBD10, and AvBD11 in the duodenum, down-regulation of AvBD10 in the jejunum, but up-regulation of AvBD8 and AvBD13 in the ceca. E. tenella challenge showed no change in AvBD expression in any tissue. In study 2, which involved challenge with only E. maxima, there was down-regulation of AvBD1 in the ileum, AvBD11 in the jejunum and ileum, and LEAP2 in all 3 segments of the small intestine. The expression of LEAP2 was further examined by in situ hybridization in the jejunum of chickens from study 2. LEAP2 mRNA was expressed similarly in the enterocytes lining the villi, but not in the crypts of control and Eimeria challenged chickens. The lengths of the villi in the Eimeria challenged chickens were less than those in the control chickens, which may in part account for the observed down-regulation of LEAP2 mRNA quantified by PCR. Overall, the AvBD response to Eimeria challenge was not consistent; whereas LEAP2 was consistently down-regulated, which suggests that LEAP2 plays an important role in modulating an Eimeria infection.

Anticoccidial activity of fruit peel of Punica granatum L

In the interests of food safety and public health, plants and their compounds are now re-emerging as an alternative approach to treat parasitic diseases. Here, we studied the anticoccidial effect of different solvent extracts of the fruit peel of Punica granatum-a commercial waste from pomegranate juice industries. The hope underlying these experiments was to find a sustainable natural product for controlling coccidiosis. The plant extracts were prepared using solvents of different polarity. Acute oral toxicity study was first carried out to see the safety of crude extracts. A high dose of crude extracts (300 mg/kg body weight) was tested for possession of anticoccidial activity against experimentally induced coccidial infection in broiler chicken. Activity was measured in comparison to the reference drug amprolium on the basis of oocyst output reduction, mean weight gain of birds and feed conversion ratio. Oocyst output was measured using Mc-Masters counting technique. Acute oral toxicity study showed that crude extracts of P. granatum are safe up to dosage of 2000 mg/kg body weight. LD⁵⁰ was not determined as mortalities were not recorded in any of the five groups of chicken. For anticoccidial activity crude methanolic extract (CME) of the fruit peel of P. granatum showed the maximum effect as evident by oocyst output reduction (92.8 ± 15.3), weight gain of birds (1403.0 ± 11.9 g) and feed conversion ratio (1.66 ± 0.04), thereby affirming the presence of alcohol soluble active ingredients in the plant. We also tested different doses (100-400 mg/kg body weight) of the CME of the fruit peel of P. granatum, the most active extract on E. tenella and observed a dose dependent effect. From the present study it can be concluded that alcoholic extract of the fruit peel of P. granatum has significant potential to contribute to the control of coccidian parasites of chicken.

Transcriptome analysis of a wild bird reveals physiological responses to the urban environment

Identifying the molecular basis of environmentally induced phenotypic variation presents exciting opportunities for furthering our understanding of how ecological processes and the environment can shape the phenotype. Urban and rural environments present free-living organisms with different challenges and opportunities, which have marked consequences for the phenotype, yet little is known about responses at the molecular level. We characterised transcriptomes from an urban and a rural population of great tits Parus major, demonstrating striking differences in gene expression profiles in both blood and liver tissues. Differentially expressed genes had functions related to immune and inflammatory responses, detoxification, protection against oxidative stress, lipid metabolism, and regulation of gene expression. Many genes linked to stress responses were expressed at higher levels in the urban birds, in accordance with our prediction that urban animals are exposed to greater environmental stress. This is one of the first studies to reveal transcriptional differences between urban- and rural-dwelling animals and suggests an important role for epigenetics in mediating environmentally induced physiological variation. The study provides valuable resources for developing further in-depth studies of the mechanisms driving phenotypic variation in the urban context at larger spatial and temporal scales.

Expression of digestive enzymes and nutrient transporters in Eimeria-challenged broilers

Avian coccidiosis is a disease caused by the intestinal protozoa Eimeria. The site of invasion and lesions in the intestine is species-specific, for example E. acervulina affects the duodenum, E. maxima the jejunum, and E. tenella the ceca. Lesions in the intestinal mucosa cause reduced feed efficiency and body weight gain. The growth reduction may be due to changes in expression of digestive enzymes and nutrient transporters in the intestine. The objective of this study was to compare the expression of digestive enzymes, nutrient transporters and an antimicrobial peptide in broilers challenged with either E. acervulina, E. maxima or E. tenella. The genes examined included digestive enzymes (APN and SI), peptide and amino acid transporters (PepT1, ASCT1, b(0,+)AT/rBAT, B(0)AT, CAT1, CAT2, EAAT3, LAT1, y(+)LAT1 and y(+)LAT2), sugar transporters (GLUT1, GLUT2, GLUT5 and SGLT1), zinc transporter (ZnT1) and an antimicrobial peptide (LEAP2). Duodenum, jejunum, ileum and ceca were collected 7 days post challenge. E. acervulina challenge resulted in downregulation of various nutrient transporters or LEAP2 in the duodenum and ceca, but not the jejunum or ileum. E. maxima challenge produced both downregulation and upregulation of nutrient transporters and LEAP2 in all three segments of the small intestine and ceca. E. tenella challenge resulted in the downregulation and upregulation of nutrient transporters and LEAP2 in the jejunum, ileum and ceca, but not the duodenum. At the respective target tissue, E. acervulina, E. maxima and E. tenella infection caused common downregulation of APN, b(0,+)AT, rBAT, EAAT3, SI, GLUT2, GLUT5, ZnT1 and LEAP2. The downregulation of nutrient transporters would result in a decrease in the efficiency of protein and polysaccharide digestion and uptake, which may partially explain the weight loss. The downregulation of nutrient transporters may also be a cellular response to reduced expression of the host defense protein LEAP2, which would diminish intracellular pools of nutrients and inhibit pathogen replication.

Downregulation of chicken interleukin-17 receptor A during Eimeria infection

Both interleukin-17A (IL-17A) and IL-17F are proinflammatory cytokines that have an important role in intestinal homeostasis via receptor signaling. These cytokines have been characterized in chickens, but very little is known about their receptors and their functional activity. We provide here the first description of the sequence analysis, bioactivity, and comparative expression analysis of chicken IL-17RA (chIL-17RA) in chickens infected with Salmonella and Eimeria, two major infectious agents of gastrointestinal diseases of poultry of economic importance. A full-length chIL-17RA cDNA with a 2,568-bp coding region was identified from chicken thymus cDNA. chIL-17RA shares ca. 46% identity with mammalian homologues and 29.2 to 31.5% identity with its piscine counterparts. chIL-17RA transcript expression was relatively high in the thymus and in the chicken macrophage cell line HD11. The chIL-17RA-specific small interfering RNA inhibits interleukin-6 (IL-6), IL-8, and IL-1β mRNA expression in chicken embryo fibroblast cells (but not in DF-1 cells) stimulated with chIL-17A or chIL-17F. Interaction between chIL-17RA and chIL-17A was confirmed by coimmunoprecipitation. Downregulation of chIL-17RA occurred in concanavalin A- or lipopolysaccharide-activated splenic lymphocytes but not in poly(I·C)-activated splenic lymphocytes. In Salmonella- and Eimeria-infected chickens, the expression levels of the chIL-17RA transcript were downregulated in intestinal tissues from chickens infected with two Eimeria species, E. tenella or E. maxima, that preferentially infect the cecum and jejunum, respectively. However, chIL-17RA expression was generally unchanged in Salmonella infection. These results suggest that chIL-17RA has an important role in mucosal immunity to intestinal intracellular parasite infections such as Eimeria infection.

Expression of digestive enzymes and nutrient transporters in Eimeria acervulina-challenged layers and broilers

Avian coccidiosis is a disease caused by intestinal protozoa in the genus Eimeria. Clinical signs of coccidiosis include intestinal lesions and reduced feed efficiency and BW gain. This growth reduction may be due to changes in expression of digestive enzymes and nutrient transporters in the intestine. The objective of this study was to examine the differential expression of digestive enzymes, transporters of amino acids, peptides, sugars, and minerals, and an antimicrobial peptide in the small intestine of Eimeria acervulina-infected broilers and layers. Uninfected broilers and layers, in general, expressed these genes at comparable levels. Some differences included 3-fold and 2-fold greater expression of the peptide transporter PepT1 and the antimicrobial peptide LEAP2 (liver expressed antimicrobial peptide 2), respectively, in the jejunum of layers compared with broilers and 17-fold greater expression of LEAP2 in the duodenum of broilers compared with layers. In the duodenum of Eimeria-infected broilers and layers, there was downregulation of aminopeptidase N; sucrase-isomaltase; the neutral, cationic, and anionic amino acid transporters b(o,+)AT/rBAT, B(o)AT, CAT2, and EAAT3; the sugar transporter GLUT2; the zinc transporter ZnT1; and LEAP2. In the jejunum of infected layers there was downregulation of many of the same genes as in the duodenum plus downregulation of PepT1, b(o,+)AT/rBAT, and the y(+) L system amino acid transporters y(+) LAT1 and y(+) LAT2. In the ileum of infected layers there was downregulation of CAT2, y(+)LAT1, the L type amino acid transporter LAT1, and the sugar transporter GLUT1, and upregulation of APN, PepT1, the sodium glucose transporter SGLT4, and LEAP2. In E. acervulina-infected broilers, there were no gene expression changes in the jejunum and ileum. These changes in intestinal digestive enzyme and nutrient transporter gene expression may result in a decrease in the efficiency of protein digestion, uptake of important amino acids and sugars, and disruption of mineral balance that may affect intestinal cell metabolism and Eimeria replication.

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.

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

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

Transcriptome analysis in chicken cecal epithelia upon infection by Eimeria tenella in vivo

Coccidiosis, caused by various Eimeria species, is a major parasitic disease in chickens. However, our understanding on how chickens respond to coccidian infection is highly limited at both molecular and cellular levels. The present study employed the Affymetrix chicken genome array and performed transcriptome analysis on chicken cecal epithelia in response to infection for 4.5 days in vivo by the cecal-specific species E. tenella. By Significance Analysis of Microarrays (SAM), we have identified 7,099 probe sets with q-values at <0.05, in which 4,033 and 3,066 genes were found to be up- or down-regulated in response to parasite infection. The reliability of the microarray data were validated by real-time qRT-PCR of 20 genes with varied fold changes in expression (i.e., correlation coefficient between microarray and qRT-PCR datasets: R (2) = 0.8773, p<0.0001). Gene ontology analysis, KEGG pathway mapping and manual annotations of regulated genes indicated that up-regulated genes were mainly involved in immunity/defense, responses to various stimuli, apoptosis/cell death and differentiation, signal transduction and extracellular matrix (ECM), whereas down-regulated genes were mainly encoding general metabolic enzymes, membrane components, and some transporters. Chickens mustered complex cecal eipthelia molecular and immunological responses in response to E. tenella infection, which included pathways involved in cytokine production and interactions, natural killer cell mediated cytotoxicity, and intestinal IgA production. In response to the pathogenesis and damage caused by infection, chicken cecal epithelia reduced general metabolism, DNA replication and repair, protein degradation, and mitochondrial functions.

Enhanced expression of IL-10 in contrast to IL-12B mRNA in poultry with experimental coccidiosis

Interleukin (IL)-12 and IL-10 are immunoregulatory cytokines with an antagonistic effect on the T-helper (Th)1/Th2 cytokine balance and they provide a functional link between innate resistance and the adaptive immune response. This investigation was conducted to determine the expression of IL-10 and IL-12B mRNA levels in chickens' gut mucosa infected with Eimeria tenella and in sulfachlorpyrazine-sodium treated animals after infection. Broiler chickens were randomly allocated in three groups: healthy untreated control; infected untreated animals and infected, treated with sulfachlorpyrazine sodium chickens 6 days after the challenge with an E. tenella. Quantitative real time PCR analysis was performed using specific primer pairs and probes for IL-10 and IL-12B. The expression of IL-10 mRNA was greater in the duodenum then in the caecum and the liver of healthy chickens. E. tenella infection led to significant up-regulation of IL-10 mRNA in the caecum, followed by mRNA in the liver. A significant down regulation was observed mainly in the caecum after the treatment with sulfachlorpyrazine. In contrast, IL-12B expression in all investigated tissues remained insignificantly affected in the studied groups of animals. Distinct up-regulation of IL-10 mRNA, after the challenge with E. tenella, in the caecum can be attributed to the tissue tropism of Eimeria spp. The production of IL-12 is regulated by negative feedback through IL-10 which explains lack of increase in IL-12B mRNA. Sulfonamide treatment resulted in clinical improvement and restoration of IL-10 mRNA to the levels observed in healthy chickens.

Immunogenic Eimeria tenella glycosylphosphatidylinositol-anchored surface antigens (SAGs) induce inflammatory responses in avian macrophages

BACKGROUND

At least 19 glycosylphosphatidylinositol (GPI)-anchored surface antigens (SAGs) are expressed specifically by second-generation merozoites of Eimeria tenella, but the ability of these proteins to stimulate immune responses in the chicken is unknown.

METHODOLOGY/PRINCIPAL FINDINGS

Ten SAGs, belonging to two previously defined multigene families (A and B), were expressed as soluble recombinant (r) fusion proteins in E. coli. Chicken macrophages were treated with purified rSAGs and changes in macrophage nitrite production, and in mRNA expression profiles of inducible nitric oxide synthase (iNOS) and of a panel of cytokines were measured. Treatment with rSAGs 4, 5, and 12 induced high levels of macrophage nitric oxide production and IL-1β mRNA transcription that may contribute to the inflammatory response observed during E. tenella infection. Concomitantly, treatment with rSAGs 4, 5 and 12 suppressed the expression of IL-12 and IFN-γ and elevated that of IL-10, suggesting that during infection these molecules may specifically impair the development of cellular mediated immunity.

CONCLUSIONS/SIGNIFICANCE

In summary, some E. tenella SAGs appear to differentially modulate chicken innate and humoral immune responses and those derived from multigene family A (especially rSAG 12) may be more strongly linked with E. tenella pathogenicity associated with the endogenous second generation stages.

Development and characterization of mouse monoclonal antibodies specific for chicken interleukin 18

Four mouse monoclonal antibodies (mAbs) which are specific for chicken interleukin 18 (chIL18) were produced and characterized by enzyme-linked immunosorbent assay (ELISA), Western blotting, quantitative real-time PCR and neutralization assays. Using Western blot analysis, monoclonal antibodies specific for chIL18 identified a 23 kDa Pichia pastoris-expressed chIL18 and 66 kDa E. coli-derived MBP fusion protein of chIL18. Bioassays for chIL18 using primary chicken spleen cells showed dose-dependent IFN-γ mRNA expression and induction of IFN-γ from primary splenocytes, and triggered nitric oxide (NO) production in the HD11 macrophage cell line. These mAbs showed neutralizing chIL18 activity. Taken together, these mouse mAbs which detect chicken IL-18 will be significant new immune reagents and useful tools for basic and applied research in poultry.

Microarray analyses of mouse responses to infection by Neospora caninum identifies disease associated cellular pathways in the host response

Neospora caninum is a coccidian cyst-forming parasite found in a wide range of host species such as mice, dogs and cattle. The development of methods such as vaccines to prevent abortion and fetal loss due to neosporosis would be greatly assisted by further knowledge on immunity and host responses to infection. In this study we used microarray technology to investigate the protective host responses occurring at 6h post infection in the spleen of mice infected with a prototype live N. caninum vaccine. Naive non-pregnant mice were infected with the NC-Nowra isolate as such infections are known to induce protective host responses that will prevent transplacental transmission of a challenge given using pregnancy. The expression data was analysed by SAM (significance of microarrays), ANOVA and clustering methods. Gene lists were investigated for enrichment of gene ontology terms by functional annotation using hypergeometric tests. The results show that Qs and BALB/c mice infected with NC-Nowra differ in their transcriptional responses to infection and these affect a wide range of biological and molecular processes. Transcriptional changes in the Jak-STAT signaling pathway (as well as Irf and other IFN-γ regulated molecules such as GTPases) confirmed the influence of IFN-γ in the mouse response to N. caninum. Gene ontology analyses also assigned some of the molecules involved to well known disease pathways associated with cancer, Parkinson's and Alzheimer's diseases, which were linked to the cell cycle, mitochondrial electron transport chain and coupled proton transport pathways amongst others. Although infection of mice with NC-Nowra causes little or no signs of clinical disease, the molecular functions, processes and pathways identified through these studies clearly warrant further investigation for their role in the development of protective immunity as well as pathogenesis. These studies therefore provide new, exciting leads by which to study neosporosis.

Light microscopic study on Eimeria species infecting Japanese quails reared in Saudi Arabian farms

Japanese quails Coturnix coturnix japonica reared in economic farms were individually investigated for coccidian infections. The results indicated the absence of infections in birds younger than 1 month. An Eimeria infection rate of up to 80% was detected in birds 7-9 weeks old with a general infection rate of 29%. The infection rate decreased to 21.42% in birds older than 10 weeks. Morphometric characteristics of freshly shed, unsporulated oocysts were taken. These oocysts appeared pale yellow in color, were oval to subspherical in shape being limited by a bilayered oocyst wall of 1.2 microm. The unsporulated oocysts measured 17.73 +/- 12.92 x 12.79 +/- 1.69 microm (mean of 100) and possessed a polar granule, a micropyle and an oocyst residuum. The sporulation took 72 h and resulted in the formation of four elongated sporocysts containing two sporozoites, in addition to a stieda body and a sporocyst residuum. The life cycle of this Eimeria species was followed in experimentally infected quails. Three asexual generations (at 60, 78, and 96 h p.i.) were detected in the epithelium of the small intestine before the sexual cycle started at 84 h p.i. The prepatent period was 5 days, while the patent period covered 6-7 days. Besides this well-defined species, another Eimeria species occurred, the oocysts of which were excreted in low numbers and were characterized by the absence of a micropyle and an oocyst residuum. These oocysts measured 15.73 +/- 2.22 x 14.18 +/- 1.89 microm (mean of 100) and sporulated already within 60 h.

Comparison of global transcriptional responses to primary and secondary Eimeria acervulina infections in chickens

In the current study, we compared chicken gene transcriptional profiles following primary and secondary infections with Eimeria acervulina using a 9.6K avian intestinal intraepithelial lymphocyte cDNA microarray (AVIELA). Gene Ontology analysis showed that primary infection significantly modulated the levels of mRNAs for genes involved in the metabolism of lipids and carbohydrates as well as those for innate immune-related genes. By contrast, secondary infection increased the levels of transcripts encoded by genes related to humoral immunity and reduced the levels of transcripts for the innate immune-related genes. Because the observed modulation in transcript levels for gene related to energy metabolism and immunity occurred concurrent with the clinical signs of coccidiosis, these results suggest that altered expression of a specific set of host genes induced by Eimeria infection may be responsible, in part, for the observed reduction in body weight gain and inflammatory gut damage that characterizes avian coccidiosis.

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.

Immunopathology and cytokine responses in broiler chickens coinfected with Eimeria maxima and Clostridium perfringens with the use of an animal model of necrotic enteritis

The incidence of necrotic enteritis (NE) due to Clostridium perfringens (CP) infection in commercial poultry has been increasing at an alarming rate. Although pre-exposure of chickens to coccidia infections is believed to be one of the major risk factors leading to NE, the underlying mechanisms of CP virulence remain undefined. The objectives of this study were to utilize an experimental model of NE produced by Eimeria maxima (EM) and CP coinfection to investigate the pathologic and immunologic parameters of the disease. Broilers coinfected with EM plus CP exhibited more severe gut pathology compared with animals given EM or CP alone. Additionally, EM/CP coinfection increased the numbers of intestinal CP bacteria compared with chickens exposed to an identical challenge of CP alone. Coinfection with EM and CP repressed nitric oxide synthase gene expression that was induced by EM alone, leading to lower plasma NO levels. Intestinal expression of a panel of cytokine and chemokine genes following EM/CP coinfection showed a mixed response depending on the transcript analyzed and the time following infection. In general, IFN-alpha, IFN-gamma, IL-1beta, IL-2, IL-12, IL-13, IL-17, and TGF-beta4 were repressed, whereas IL-8, IL-10, IL-15, and LITAF were increased during coinfection compared with challenge by EM or CP alone. These results are discussed in the context of EM and CP to act synergistically to create a more severe disease phenotype leading to an altered cytokine/chemokine response than that produced by infection with the individual pathogens.

The role of chicken IL-1beta, IL-6 and TNF-alpha in the occurrence of amyloid arthropathy

In this study, the roles of IL-1beta, IL-6 and TNF-alpha in amyloid arthropathic chickens with variable amounts (severe, moderate and mild) of amyloid accumulation were investigated. The presence and the levels of cytokines were evaluated in serum and in joint tissues by using ELISA and immunohistochemistry, respectively. One hundred brown layer chicks were allocated into four groups and intra-articular injections of Freund's adjuvant were used to induce amyloid arthropathy in Groups II, III and IV. Vitamin A in group II, and methylprednisolone in Group IV were added to enhance and to reduce the severity of amyloidosis, respectively. At the end of the study, a positive correlation was observed among the incidence and severity of amyloidosis, the serum amyloid A levels and the IL-1beta values both in the serum and tissues. Elevation in the tissue TNF-alpha levels in parallel with the severity of amyloidosis has also been noted. As a conclusion, IL-1beta appears to play an important role in avian AA amyloidosis either alone or in combination with TNF-alpha. Further investigation is needed for understanding the role of the pro-inflammatory cytokines in avian AA amyloidosis.

Expression profiling of the solute carrier gene family in chicken intestine from the late embryonic to early post-hatch stages

Intestinal development during late embryogenesis and early post-hatch has a long-term influence on digestive and absorptive capacity in chickens. The objective of this research was to obtain a global view of intestinal solute carrier (SLC) gene family member expression from late embryogenesis until 2 weeks post-hatch with a focus on SLC genes involved in uptake of sugars and amino acids. Small intestine samples from male chicks were collected on embryonic days 18 (E18) and 20 (E20), day of hatch and days 1, 3, 7 and 14 post-hatch. The expression profiles of 162 SLC genes belonging to 41 SLC families were determined using Affymetrix chicken genome microarrays. The majority of SLC genes showed little or no difference in level of expression during E18-D14. A number of well-known intestinal transporters were upregulated between E18 and D14 including the amino acid transporters rBAT, y(+)LAT-2 and EAAT3, the peptide transporter PepT1 and the sugar transporters SGLT1, GLUT2 and GLUT5. The amino acid transporters CAT-1 and CAT-2 were downregulated. In addition, several glucose and amino acid transporters that are novel to our understanding of nutrient absorption in the chicken intestine were discovered through the arrays (SGLT6, SNAT1, SNAT2 and AST). These results represent a comprehensive characterization of the expression profiles of the SLC family of genes at different stages of development in the chicken intestine and lay the ground work for future nutritional studies.

Transcriptional analysis of host responses to Marek's disease virus infection in genetically resistant and susceptible chickens

Marek's disease virus (MDV) is a cell-associated oncogenic herpesvirus that targets B cells and T cells, inducing lymphoid tumours in chickens. Genetic resistance to Marek's disease (MD) is regulated in a polygenic fashion. In this study, we sought to compare the gene expression profiles following infection of birds that are genetically resistant or susceptible to MD (with the B21 and B19 haplotypes respectively at the MHC locus), including comparisons to uninfected controls. On days 4, 7, 14 and 21 post-infection, gene expression profiles in spleen tissue were obtained using a chicken immune-specific microarray. A number of genes showed significant (P <or= 0.05) differential expression across time and treatments. These included the chemokine AH221, B-cell marker Bu-1, IgG, IgA, IgM, MHC class II beta chain, granzyme A (GZMA) and signal transducers and activators of transcription 2 (STAT2) genes. In several comparisons, genes such as GZMA and STAT2 were induced in infected birds regardless of their genetic background. However, only immunoglobulin genes were differentially expressed by >or=2-fold in resistant compared with susceptible infected chickens. IgM and IgG were significantly induced on day 7 post-infection in susceptible chickens compared to resistant birds, whereas both of these genes were repressed in susceptible birds on day 14 post-infection. Overall, gene expression profiles in the chicken spleen observed after MDV infection were dependent on time and host genetic background. These gene expression profiles provide a platform for defining novel candidate genes for resistance or susceptibility to MD.

Functional genomics of the chicken--a model organism

Since the sequencing of the genome and the development of high-throughput tools for the exploration of functional elements of the genome, the chicken has reached model organism status. Functional genomics focuses on understanding the function and regulation of genes and gene products on a global or genome-wide scale. Systems biology attempts to integrate functional information derived from multiple high-content data sets into a holistic view of all biological processes within a cell or organism. Generation of a large collection ( approximately 600K) of chicken expressed sequence tags, representing most tissues and developmental stages, has enabled the construction of high-density microarrays for transcriptional profiling. Comprehensive analysis of this large expressed sequence tag collection and a set of approximately 20K full-length cDNA sequences indicate that the transcriptome of the chicken represents approximately 20,000 genes. Furthermore, comparative analyses of these sequences have facilitated functional annotation of the genome and the creation of several bioinformatic resources for the chicken. Recently, about 20 papers have been published on transcriptional profiling with DNA microarrays in chicken tissues under various conditions. Proteomics is another powerful high-throughput tool currently used for examining the dynamics of protein expression in chicken tissues and fluids. Computational analyses of the chicken genome are providing new insight into the evolution of gene families in birds and other organisms. Abundant functional genomic resources now support large-scale analyses in the chicken and will facilitate identification of transcriptional mechanisms, gene networks, and metabolic or regulatory pathways that will ultimately determine the phenotype of the bird. New technologies such as marker-assisted selection, transgenics, and RNA interference offer the opportunity to modify the phenotype of the chicken to fit defined production goals. This review focuses on functional genomics in the chicken and provides a road map for large-scale exploration of the chicken genome.

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.

Dosage compensation is less effective in birds than in mammals

BACKGROUND

In animals with heteromorphic sex chromosomes, dosage compensation of sex-chromosome genes is thought to be critical for species survival. Diverse molecular mechanisms have evolved to effectively balance the expressed dose of X-linked genes between XX and XY animals, and to balance expression of X and autosomal genes. Dosage compensation is not understood in birds, in which females (ZW) and males (ZZ) differ in the number of Z chromosomes.

RESULTS

Using microarray analysis, we compared the male:female ratio of expression of sets of Z-linked and autosomal genes in two bird species, zebra finch and chicken, and in two mammalian species, mouse and human. Male:female ratios of expression were significantly higher for Z genes than for autosomal genes in several finch and chicken tissues. In contrast, in mouse and human the male:female ratio of expression of X-linked genes is quite similar to that of autosomal genes, indicating effective dosage compensation even in humans, in which a significant percentage of genes escape X-inactivation.

CONCLUSION

Birds represent an unprecedented case in which genes on one sex chromosome are expressed on average at constitutively higher levels in one sex compared with the other. Sex-chromosome dosage compensation is surprisingly ineffective in birds, suggesting that some genomes can do without effective sex-specific sex-chromosome dosage compensation mechanisms.