Chicken innate immune response to oral infection with Salmonella enterica serovar Enteritidis

Quercetin attenuates lipopolysaccharide-induced hepatic inflammation by modulating autophagy and necroptosis

Lipopolysaccharide (LPS) from Gram-negative bacteria initially induces liver inflammation with proinflammatory cytokines expressions. However, the underlying hepatoprotective mechanism of quercetin on LPS-induced hepatic inflammation remains unclear. Specific pathogen-free chicken embryos (n = 120) were allocated control vehicle, PBS with or without ethanol vehicle, LPS (125 ng/egg) with or without quercetin treatment (10, 20, or 40 nmol/egg, respectively), quercetin groups (10, 20, or 40 nmol/egg). Fifteen-day-old embryonated eggs were inoculated abovementioned solutions via the allantoic cavity. At embryonic d 19, the livers of the embryos were collected for histopathological examination, RNA extraction, real-time polymerase chain reaction, and immunohistochemistry investigation. We found that the liver presented inflammatory response (heterophils infiltration) after LPS induction. The LPS-induced mRNA expressions of inflammation-related factors (TLR4, TNFα, IL-1β, IL-10, IL-6, MYD88, NF-κB1, p38, and MMP3) were upregulated after LPS induction when compared with the PBS group, while quercetin could downregulate these expressions as compared with the LPS group. Quercetin significantly decreased the immunopositivity to TLR4 and MMP3 in the treatment group when compared with the LPS group. Quercetin could significantly downregulate the mRNA expressions of autophagy-related genes (ATG5, ATG7, Beclin-1, LC3A, and LC3B) and necroptosis-related genes (Fas, Bcl-2, Drp1, and RIPK1) after LPS induction. Quercetin significantly decreased the immunopositivity to LC3 in the treatment group when compared with the LPS group; meanwhile, quercetin significantly decreased the protein expressions of LC3-I, LC3-II, and the rate of LC3-II/LC3-I. In conclusions, quercetin can alleviate hepatic inflammation induced by LPS through modulating autophagy and necroptosis.

Identification of novel biomarkers of acute phase response in chickens challenged with Escherichia coli lipopolysaccharide endotoxin

BACKGROUND

The chicken's inflammatory response is an essential part of the bird's response to infection. A single dose of Escherichia coli (E. coli) lipopolysaccharide (LPS) endotoxin can activate the acute phase response (APR) and lead to the production of acute phase proteins (APPs). In this study, the responses of established chicken APPs, Serum amyloid A (SAA) and Alpha-1-acid-glycoprotein (AGP), were compared to two novel APPs, Hemopexin (Hpx) and Extracellular fatty acid binding protein (Ex-FABP), in 15-day old broilers over a time course of 48 h post E.coli LPS challenge. We aimed to investigate and validate their role as biomarkers of an APR. Novel plant extracts, Citrus (CTS) and cucumber (CMB), were used as dietary supplements to investigate their ability to reduce the inflammatory response initiated by the endotoxin.

RESULTS

A significant increase of established (SAA, AGP) and novel (Ex-FABP, Hpx) APPs was detected post E.coli LPS challenge. Extracellular fatty acid binding protein (Ex-FABP) showed a similar early response to SAA post LPS challenge by increasing ~ 20-fold at 12 h post challenge (P < 0.001). Hemopexin (Hpx) showed a later response by increasing ∼5-fold at 24 h post challenge (P < 0.001) with a similar trend to AGP. No differences in APP responses were identified between diets (CTS and CMB) using any of the established or novel biomarkers.

CONCLUSIONS

Hpx and Ex-FABP were confirmed as potential biomarkers of APR in broilers when using an E. coli LPS model along with SAA and AGP. However, no clear advantage for using either of dietary supplements to modulate the APR was identified at the dosage used.

Transcriptional responses of cytokines, immunoglobulin A, and nitric oxide genes in 1-day-old chicks post Salmonella typhimurium infection: An experimental study

Background

Salmonella has become one of the hazards prevalent foodborne pathogens causing different diseases in chickens. However, Salmonella typhimurium (ST), a nonhost-specific serovar, is a major avian agent that causes severe disturbance in young chicken wellness.

Aim

The occurrence of Salmonella in chickens and their antimicrobial resistance were explored in this study. In addition, the immune response of 1-day-old broiler chicks, against multidrug resistant (MDR) ST infection, was also assessed at 4 and 24 hours post infection (pi) in the cecum and spleen, representing their mucosal and systemic immune responses, respectively.

Methods

A total of 375 samples from 130 diseased and apparently healthy broiler and layer chickens were randomly collected for Salmonella isolation, identification, and resistance profile evaluation, from farms and different clinical laboratories. The immune response of 1-day-old broiler chicks, Ross 308, against in-vivo ST infection was ascertained through the evaluation of heterophile phagocytosis and s expression of cytokines, immunoglobulin A and other immune-regulating genes in the cecum and spleen. Twenty-four, 1-day-old nonvaccinated broiler chicks were used and divided into two groups. The chicks in the infected group were orally inoculated with 0.5 ml of 2 × 108 colony forming units (CFU)/ml of MDR ST suspension, while those in the control group were taken nutrient broth.

Results

Seven out of 130 (5.38%) examined chickens were positive for Salmonella. All isolates (100%) were resistant to amoxicillin-clavulanic acid (AMC), cefazolin (CZ), cefoxitin (FOX), ciprofloxacin (CIP), nalidixic acid (NA), tetracycline (TE), fosfomycin (FOS), and colistin (CT) with multiple antimicrobial resistances (MARs) index range of 0.72-0.83, where none of them was resistant to meropenem (MEM). The results of immune response revealed that chicks infected with ST showed significantly different phagocytosis percentages and index values compared to controls. According to the real-time quantitative polymerase chain reaction (RT-qPCR) results, the transcription of IL-8, iNOS, IL-18, IgA, and IFN-γ for chicks infected by ST showed a significantly increased trend (p < 0.01) with increasing chicken age and was higher in the cecum than spleen compared to controls (p < 0.05) during 24 hours after infection.

Conclusion

The findings indicated a strong mucosal immune response in the chicks after the ST challenge, which reflects humoral and cellular responses. Our insight recommended the occurrence of a natural immune response stimulator at 1 day age to face the infection, and this can prevent the resistance transfer, with efficient control measures.

Controlling Salmonella: strategies for feed, the farm, and the processing plant

Controlling Salmonella in poultry is an ongoing food safety measure and while significant progress has been made, there is a need to continue to evaluate different strategies that include understanding Salmonella-poultry interaction, Salmonella-microbiota interactions, Salmonella genetics and response to adverse conditions, and preharvest and postharvest parameters that enable persistence. The purpose of this symposium is to discuss different strategies to consider from feed milling to the farm to the processing environment. This Poultry Science Association symposium paper is divided into 5 different sections that covers 1) immunological aspects of Salmonella control, 2) application of Salmonella genetics for targeted control strategies in poultry production, 3) improving poultry feed hygienics: utilizing feed manufacture techniques and equipment to improve feed hygienics, 4) practical on farm interventions for controlling Salmonella-what works and what may not work, and 5) monitoring and mitigating Salmonella in poultry. These topics elucidate the critical need to establish control strategies that will improve poultry gut health and limit conditions that exposes Salmonella to stress causing alterations to virulence and pathogenicity both at preharvest and postharvest poultry production. This information is relevant to the poultry industry's continued efforts to ensure food safety poultry production.

Fructose-enabled killing of antibiotic-resistant Salmonella enteritidis by gentamicin: Insight from reprogramming metabolomics

Salmonella enterica is a food-borne pathogen that poses a severe threat to both poultry production and human health. Antibiotics are critical for the initial treatment of bacterial infections. However, the overuse and misuse of antibiotics results in the rapid evolution of antibiotic-resistant bacteria, and the discovery and development of new antibiotics are declining. Therefore, understanding antibiotic resistance mechanisms and developing novel control measures are essential. In the present study, GC-MS-based metabolomics analysis was performed to determine the metabolic profile of gentamicin sensitive (SE-S) and resistant (SE-R) S. enterica. Fructose was identified as a crucial biomarker. Further analysis demonstrated a global depressed central carbon metabolism and energy metabolism in SE-R. The decrease in the pyruvate cycle reduces the production of NADH and ATP, causing a decrease in membrane potential, which contributes to gentamicin resistance. Exogenous fructose potentiated the effectiveness of gentamicin in killing SE-R by promoting the pyruvate cycle, NADH, ATP and membrane potential, thereby increasing gentamicin intake. Further, fructose plus gentamicin improved the survival rate of chicken infected with gentamicin-resistant Salmonella in vivo. Given that metabolite structures are conserved across species, fructose identified from bacteria could be used as a biomarker for breeding disease-resistant phenotypes in chicken. Therefore, a novel strategy is proposed for fighting against antibiotic-resistant S. enterica, including exploring molecules suppressed by antibiotics and providing a new approach to find pathogen targets for disease resistance in chicken breeding.

Dietary supplemental coated essential oils and organic acids mixture improves growth performance and gut health along with reduces Salmonella load of broiler chickens infected with Salmonella Enteritidis

BACKGROUND

Reducing Salmonella infection in broiler chickens by using effective and safe alternatives to antibiotics is vital to provide safer poultry meat and minimize the emergence of drug-resistant Salmonella and the spread of salmonellosis to humans. This study was to first evaluate the protective efficacy of feeding coated essential oils and organic acids mixture (EOA) on broiler chickens infected with Salmonella Enteritidis (S. Enteritidis, SE), and then its action mechanism was further explored.

METHODS

A total of 480 1-day-old Arbor Acres male chickens were randomly assigned into five treatments with six replicates, including non-challenged control fed with basal diet (A), SE-challenged control (B), and SE-infected birds fed a basal diet with 300 mg/kg of EOA (BL), 500 mg/kg of EOA (BM) and 800 mg/kg of EOA (BH), respectively. All birds on challenged groups were infected with Salmonella Enteritidis on d 13.  RESULTS: Feeding EOA showed a reversed ability on negative effects caused by SE infection, as evidenced by decreasing the feed conversion rate (FCR) and the ratio of villus height to crypt depth (VH/CD) (P < 0.05), obviously decreasing intestinal and internal organs Salmonella load along with increasing cecal butyric acid-producing bacteria abundance (P < 0.05). Moreover, supplemental different levels of EOA notably up-regulated claudin-1 (CLDN-1), occludin (OCLN), zonula occludens-1 (ZO-1), mucin-2 (MUC-2), fatty acid binding protein-2 (FABP-2), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), myeloid differential protein-88 (MyD88) and interleukin-6 (IL-6) mRNA levels in the ileum of the infected chickens after challenge, whereas down-regulated toll-like receptor-4 (TLR-4) mRNA levels (P < 0.05). Linear discriminant analysis combined effect size measurements analysis (LEfSe) showed that the relative abundance of g_Butyricicoccus, g_Anaerotruncus and g_unclassified_f_Bacillaceae significantly was enriched in infected birds given EOA. Also, phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) analysis showed that alpha-linolenic acid metabolism, fatty acid metabolism and biosynthesis of unsaturated fatty acids were significantly enriched in the EOA group.

CONCLUSION

Our data suggest that the essential oils and organic acids mixture can be used as an effective strategy to ameliorate and alleviate Salmonella Enteritidis infection in broilers.

Serum amyloid A regulates TLR2/4-mediated IFN-β signaling pathway against Marek's disease virus

Serum amyloid A (SAA), an acute response phase protein (APP), is crucial for the innate immune response during pathogenic microorganisms' invasion. Marek's disease virus (MDV) is a highly oncogenic alphaherpesvirus that activates multiple innate immune molecules, including SAA, in the host during infection. However, the pathway through which SAA participates in MDV-induced host innate immunity remains unknown. The present study aimed to elucidate the pathway through which SAA exerts its anti-MDV function. We observed that MDV infection in vivo and in vitro significantly elevated SAA expression. Furthermore, through SAA overexpression and knockdown experiments, we demonstrated that SAA could inhibit MDV replication. Subsequently, we found that SAA activated Toll-Like Receptor 2/4 (TLR2/4) -mediated Interferon Beta (IFN-β) promoter activity and IFN regulatory factor 7 (IRF7) promoter activity. During MDV infection, SAA enhanced TLR2/4-mediated IFN-β signal transduction and messenger RNAs (mRNAs) expression of type I IFN (IFN-I) and interferon-stimulated genes (ISGs). Finally, TLR2/4 inhibitor OxPAPC inhibits the anti-MDV activity of SAA. These results demonstrated that SAA inhibits MDV replication and enhancing TLR2/4-mediated IFN-β signal transduction to promote IFNs and ISGs expression. This finding is the first to demonstrate the signaling pathway by which SAA exerts its anti-MDV function. It also provides new insights into the control of oncogenic herpesviruses from the perspective of acute response phase proteins.

Evolution of developmental and comparative immunology in poultry: The regulators and the regulated

Avian has a unique immune system that evolved in response to environmental pressures in all aspects of innate and adaptive immune responses, including localized and circulating lymphocytes, diversity of immunoglobulin repertoire, and various cytokines and chemokines. All of these attributes make birds an indispensable vertebrate model for studying the fundamental immunological concepts and comparative immunology. However, research on the immune system in birds lags far behind that of humans, mice, and other agricultural animal species, and limited immune tools have hindered the adequate application of birds as disease models for mammalian systems. An in-depth understanding of the avian immune system relies on the detailed studies of various regulated and regulatory mediators, such as cell surface antigens, cytokines, and chemokines. Here, we review current knowledge centered on the roles of avian cell surface antigens, cytokines, chemokines, and beyond. Moreover, we provide an update on recent progress in this rapidly developing field of study with respect to the availability of immune reagents that will facilitate the study of regulatory and regulated components of poultry immunity. The new information on avian immunity and available immune tools will benefit avian researchers and evolutionary biologists in conducting fundamental and applied research.

Regulation of mRNA and miRNA in the response to Salmonella enterica serovar Enteritidis infection in chicken cecum

BACKGROUND

Salmonella enterica, serovar Enteritidis (SE) is a food-borne pathogen, which can cause great threat to human health through consumption of the contaminated poultry products. Chicken is the main host of SE. The mRNA and microRNA (miRNA) expression profiles were analyzed on cecum of Shouguang chicken via next-generation sequencing and bioinformatics approaches. The treated group was inoculated SE, and the control group was inoculated with phosphate buffer saline (PBS).

RESULTS

There were 1760 differentially expressed mRNAs in the SE-infected group, of which 1046 were up-regulated mRNA, and 714 were down-regulated mRNA. In addition, a total of 821 miRNAs were identified, and 174 miRNAs were differentially expressed, of which 100 were up-regulated and 74 were down-regulated. Functional enrichment of differentially expressed mRNAs was similar to miRNA target genes. The functional analysis results of differentially expressed mRNAs and miRNAs were performed. Immune-related processes and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways were enriched by up-regulated mRNA. The down-regulated mRNAs were enriched in tissue development and metabolic-related KEGG pathways. The functional analysis of up-regulated miRNA target genes was similar to the down-regulated mRNAs. The down-regulated miRNA target genes were enriched in metabolic-related GO (Gene Ontology) -BP (Biological process) terms and KEGG pathways. The overlap of the up-regulated mRNA and the up-regulated miRNA target genes (class I) was 325, and the overlap of the down-regulated miRNA target genes (class II) was 169. The class I enriched in the immune-related GO-BP terms and KEGG pathways. The class II mainly enriched in metabolic-related GO-BP terms and KEGG pathways. Then we detected the expression of mRNA and miRNA through qRT-PCR. The results shown that the expression of HHIP, PGM1, HTR2B, ITGB5, RELN, SFRP1, TCF7L2, SCNN1A, NEK7, miR-20b-5p, miR-1662, miR-15a, miR-16-1-3p was significantly different between two groups. Dual-luciferase reporter assay was used to detect the relationship between miR-20b-5p and SCNN1A. The result indicated that miR-20b-5p regulate immune or metabolic responses after SE infection in Shouguang chickens by directly targeting SCNN1A.

CONCLUSIONS

The findings here contribute to the further analysis of the mechanism of mRNA and miRNA defense against SE infection, and provide a theoretical foundation for the molecular disease-resistant breeding of chickens.

Symbiotic bacteria stabilize the intestinal environment by producing phenylpropanoids

Salmonella enterica serovar Enteritidis (S. Enteritidis) can colonize in the intestinal tract of chickens and transmit to humans. In order to decrypt the mechanism of avian resistance to S. Enteritidis, we utilized two China local chicken breeds to generate the reciprocal crosses (the Cross and the Reverse-cross). The two lines of hybrids were orally inoculated with S. Enteritidis at 2-day old and sampled at 3 days post-inoculation. Along the analysis direction of multi-omics, differential metabolites, functional pathways and correlated microbes, we found that 12 species of microbes thrived upon S. Enteritidis challenge and probably contributed to the intestinal stability in the Cross by enhancing the production of phenylpropanoids. Our findings can help to understand the symbiotic and resistant mechanisms derived from the intestinal microbiota.

Screening of interferon-stimulated genes against avian reovirus infection and mechanistic exploration of the antiviral activity of IFIT5

Avian reovirus (ARV) infection can lead to severe immunosuppression, complications, and secondary diseases, causing immense economic losses to the poultry industry. In-depth study of the mechanism by which the innate immune system combats ARV infection, especially the antiviral effect mediated by interferon, is needed to prevent and contain ARV infection. In this study, ARV strain S1133 was used to artificially infect 7-day-old specific pathogen–free chickens. The results indicated that ARV rapidly proliferated in the immune organs, including the spleen, bursa of Fabricius, and thymus. The viral load peaked early in the infection and led to varying degrees of pathological damage to tissues and organs. Real-time quantitative PCR revealed that the mRNA levels of interferon and multiple interferon-stimulated genes (ISGs) in the spleen, bursa of Fabricius, and thymus were upregulated to varying degrees in the early stage of infection. Among the ISGs, IFIT5, and Mx were the most upregulated in various tissues and organs, suggesting that they are important ISGs for host resistance to ARV infection. Further investigation of the role of IFIT5 in ARV infection showed that overexpression of the IFIT5 gene inhibited ARV replication, whereas inhibition of the endogenously expressed IFIT5 gene by siRNA promoted ARV replication. IFIT5 may be a positive feedback regulator of the innate immune signaling pathways during ARV infection and may induce IFN-α production by promoting the expression of MAD5 and MAVS to exert its antiviral effect. The results of this study help explain the innate immune regulatory mechanism of ARV infection and reveal the important role of IFIT5 in inhibiting ARV replication, which has important theoretical significance and practical application value for the prevention and control of ARV infection.

Comparative RNA-Seq analysis reveals insights in Salmonella disease resistance of chicken; and database development as resource for gene expression in poultry

Salmonella, one of the major infectious diseases in poultry, causes considerable economic losses in terms of mortality and morbidity, especially in countries that lack effective vaccination programs. Besides being resistant to diseases, indigenous chicken breeds are also a potential source of animal protein in developing countries. For understanding the disease resistance, an indigenous chicken line Kashmir faverolla, and commercial broiler were selected. RNA-seq was performed after challenging the chicken with Salmonella Typhimurium. Comparative differential expression results showed that following infection, a total of 3153 genes and 1787 genes were differentially expressed in the liver and spleen, respectively. The genes that were differentially expressed included interleukins, cytokines, NOS2, Avβ-defensins, toll-like receptors, and other immune-related gene families. Most of the genes and signaling pathways involved in the innate and adaptive immune responses against bacterial infection were significantly enriched in the Kashmir faverolla. Pathway analysis revealed that most of the enriched pathways were MAPK signaling pathway, NOD-like receptor signaling pathway, TLR signaling pathway, PPAR signaling pathway, endocytosis, etc. Surprisingly some immune-related genes like TLRs were upregulated in the susceptible chicken breed. On postmortem examination, the resistant birds showed small lesions in the liver compared to large necrotic lesions in susceptible birds. The pathological manifestations and RNA sequencing results suggest a balancing link between resistance and infection tolerance in Kashmir faverolla. Here we also developed an online Poultry Infection Database (https://skuastk.org/pif/index.html), the first publicly available gene expression resource for disease resistance in chickens. The available database not only shows the data for gene expression in chicken tissues but also provides quick search, visualization and download capacity.

Comparative analysis of the caecal tonsil transcriptome in two chicken lines experimentally infected with Salmonella Enteritidis

Managing Salmonella enterica Enteritidis (SE) carriage in chicken is necessary to ensure human food safety and enhance the economic, social and environmental sustainability of chicken breeding. Salmonella can contaminate poultry products, causing human foodborne disease and economic losses for farmers. Both genetic selection for a decreased carriage and gut microbiota modulation strategies could reduce Salmonella propagation in farms. Two-hundred and twenty animals from the White Leghorn inbred lines N and 61 were raised together on floor, infected by SE at 7 days of age, transferred into isolators to prevent oro-fecal recontamination and euthanized at 12 days post-infection. Caecal content DNA was used to measure individual Salmonella counts (ISC) by droplet digital PCR. A RNA sequencing approach was used to measure gene expression levels in caecal tonsils after infection of 48 chicks with low or high ISC. The analysis between lines identified 7516 differentially expressed genes (DEGs) corresponding to 62 enriched Gene Ontology (GO) Biological Processes (BP) terms. A comparison between low and high carriers allowed us to identify 97 DEGs and 23 enriched GO BP terms within line 61, and 1034 DEGs and 288 enriched GO BP terms within line N. Among these genes, we identified several candidate genes based on their putative functions, including FUT2 or MUC4, which could be involved in the control of SE infection, maybe through interactions with commensal bacteria. Altogether, we were able to identify several genes and pathways associated with differences in SE carriage level. These results are discussed in relation to individual caecal microbiota compositions, obtained for the same animals in a previous study, which may interact with host gene expression levels for the control of the caecal SE load.

Chicken-Specific Kinome Analysis of Early Host Immune Signaling Pathways in the Cecum of Newly Hatched Chickens Infected With Salmonella enterica Serovar Enteritidis

Poultry is a major source of human foodborne illness caused by broad host range Salmonella serovars (paratyphoid), and developing cost-effective, pre-harvest interventions to reduce these pathogens would be valuable to the industry and consumer. Host responses to infectious agents are often regulated through phosphorylation. However, proteomic mechanisms of Salmonella acute infection biology and host responses to the bacteria have been limited concentrating predominately on the genomic responses of the host to infection. Our recent development of chicken-specific peptide arrays for kinome analysis of host phosphorylation-based cellular signaling responses provided us with the opportunity to develop a more detailed understanding of the early (4-24 h post-infection) host-pathogen interactions during the initial colonization of the cecum by Salmonella. Using the chicken-specific kinomic immune peptide array, biological pathway analysis showed infection with S. Enteritidis increased signaling related to the innate immune response, relative to the non-infected control ceca. Notably, the acute innate immune signaling pathways were characterized by increased peptide phosphorylation (activation) of the Toll-like receptor and NOD-like receptor signaling pathways, the activation of the chemokine signaling pathway, and the activation of the apoptosis signaling pathways. In addition, Salmonella infection induced a dramatic alteration in the phosphorylation events of the JAK-STAT signaling pathway. Lastly, there is also significant activation of the T cell receptor signaling pathway demonstrating the initiation of the acquired immune response to Salmonella infection. Based on the individual phosphorylation events altered by the early Salmonella infection of the cecum, certain conclusions can be drawn: (1) Salmonella was recognized by both TLR and NOD receptors that initiated the innate immune response; (2) activation of the PPRs induced the production of chemokines CXCLi2 (IL-8) and cytokines IL-2, IL-6, IFN-α, and IFN-γ; (3) Salmonella infection targeted the JAK-STAT pathway as a means of evading the host response by targeting the dephosphorylation of JAK1 and TYK2 and STAT1,2,3,4, and 6; (4) apoptosis appears to be a host defense mechanism where the infection with Salmonella induced both the intrinsic and extrinsic apoptotic pathways; and (5) the T cell receptor signaling pathway activates the AP-1 and NF-κB transcription factor cascades, but not NFAT.

The control of poultry salmonellosis using organic agents: an updated overview

Salmonellosis is a severe problem that threatens the poultry sector worldwide right now. Salmonella gallinarium and Salmonella pullorum (Fowl typhoid) are the most pathogenic serovars in avian species leading to systemic infection resulting in severe economic losses in the poultry industry. Nontyphoidal serotypes of Salmonella (Paratyphoid disease) constitute a public health hazard for their involvement in food poisoning problems in addition to their zoonotic importance. Also, Salmonella species distribution is particularly extensive. They resisted environmental conditions that made it difficult to control their spread for a long time. Therefore, the current review aimed to through light on Salmonellosis in poultry with particular references to its pathogenesis, economic importance, immune response to Salmonella, Salmonella antibiotics resistance, possible methods for prevention and control of such problems using promising antibiotics alternatives including probiotics, prebiotics, symbiotics, organic acids, essential oils, cinnamaldehyde, chitosan, nanoparticles, and vaccines.

High Affinity Iron Acquisition Systems Facilitate but Are Not Essential for Colonization of Chickens by Salmonella Enteritidis

The roles of TonB mediated Fe³⁺ (ferric iron) uptake via enterobactin (involving biosynthesis genes entABCDEF) and Fe²⁺ (ferrous iron) uptake through the FeoABC transporter are poorly defined in the context of chicken-Salmonella interactions. Both uptake systems are believed to be the major contributors of iron supply in the Salmonella life cycle. Current evidence suggests that these iron uptake systems play a major role in pathogenesis in mammals and as such, they represent promising antibacterial targets with therapeutic potential. We investigated the role of these iron uptake mechanisms regarding the ability of Salmonella Enteritidis (SEn) strains to colonize in a chicken infection model. Further we constructed a bioluminescent reporter to sense iron limitation during gastrointestinal colonization of Salmonella in chicken via ex vivo imaging. Our data indicated that there is some redundancy between the ferric and ferrous iron uptake mechanisms regarding iron acquisition during SEn pathogenesis in chicken. We believe that this redundancy of iron acquisition in the host reservoir may be the consequence of adaptation to unique avian environments, and thus warrants further investigation. To our knowledge, this the first report providing direct evidence that both enterobactin synthesis and FeoABC mediated iron uptake contribute to the virulence of SEn in chickens.

Avian Cell Culture Models to Study Immunomodulatory Properties of Bioactive Products

Simple Summary

Bioactive products have an effect on the molecular and biochemical functions of a living organism, causing a physiological response of the given tissue. Such a products are biologically active. Depending on the active component and amount, the effects of such products can be positive or negative. Bioactive products can be food ingredients or dietary supplements, and while they are not required for survival, they are responsible for changes in the body’s health. Poultry farming struggles with zoonoses and other infectious diseases that require the use of veterinary drugs such as antibiotics. However, it is preferable to increase the natural potential of the poultry to cope with the burden of innate immune responses. Bioactive products can be used as an alternative to microbial or antiparasitic agents. Over 400,000 different plant species contain bioactive chemicals, yet only a portion of them have been examined. To examine and describe their therapeutic capabilities, more scientific analyses and characterizations are required. The use of in vitro and ex vivo models enables the evaluation of the immunomodulatory effect of bioactive molecules derived from substances such as plant extracts, essential oils, probiotics, prebiotics, and synbiotics. This article presents several studies on bioactive products and their immunomodulatory effects tested in vitro and ex vivo using various avian models.

Abstract

Antimicrobial resistance is becoming a greater danger to both human and animal health, reducing the capacity to treat bacterial infections and increasing the risk of morbidity and mortality from resistant bacteria. Antimicrobial efficacy in the treatment of bacterial infections is still a major concern in both veterinary and human medicine. Antimicrobials can be replaced with bioactive products. Only a small number of plant species have been studied in respect to their bioactive compounds. More research is needed to characterize and evaluate the therapeutic properties of the plant extracts. Due to the more and more common phenomenon of antimicrobial resistance, poultry farming requires the use of natural alternatives to veterinary antibiotics that have an immunomodulatory effect. These include a variety of bioactive products, such as plant extracts, essential oils, probiotics, prebiotics, and synbiotics. This article presents several studies on bioactive products and their immunomodulatory effects tested in vitro and ex vivo using various avian cell culture models. Primary cell cultures that have been established to study the immune response in chickens include peripheral blood mononuclear cells (PBMCs), intestinal epithelial cells (IEC), and bone marrow-derived dendritic cells (BMDCs). Chicken lymphatic lines that can be used to study immune responses are mainly: chicken B cells infected with avian leukemia RAV-1 virus (DT40), macrophage-like cell line (HD11), and a spleen-derived macrophage cell line (MQ-NCSU). Ex vivo organ cultures combine in vitro and in vivo studies, as this model is based on fragments of organs or tissues grown in vitro. As such, it mimics the natural reactions of organisms, but under controlled conditions. Most ex vivo organ cultures of chickens are derived from the ileum and are used to model the interaction between the gastrointestinal tract and the microbiota. In conclusion, the use of in vitro and ex vivo models allows for numerous experimental replications in a short period, with little or no ethical constraints and limited confounding factors.

Bacillus-based probiotics affect gut barrier integrity in different ways in chickens subjected to optimal or challenge conditions

Dietary supplementation with spore-forming Bacillus-based probiotics represents an efficient means to improve gut health while maintaining good broiler performance. This study investigated the potential of two probiotic products in chickens subjected to optimal (Experiment 1) and Clostridium perfringens-challenged (Experiment 2) conditions. The treatments in Experiment 1 were as follows: (i) CON (no probiotic additive), (ii) One-strain Pro (supplemented with Bacillus licheniformis) or (iii) Multi-strain Pro (supplemented with a multistrain Bacillus-based probiotic). The treatment groups in Experiment 2 received the same diets as those in Experiment 1 but were subjected to C. perfringens challenge. Both experiments lasted 35 days. Both products marginally affected broiler performance in the optimal or challenge conditions. In Experiment 1, Multi-strain Pro upregulated the mRNA expression level of 11 out of 15 selected genes, whereas in Experiment 2, this was less evident, and One-strain Pro was more effective. The multistrain probiotic was effective in maintaining gut morphostructure indices and increasing gut wall thickness, which was particularly evident in challenged birds. Neither additive induced bacterial activity (assessed by measuring enzymatic activity and short-chain fatty acid production) in the cecum, and Multi-strain Pro maintained the cecal butyrate concentration in challenged birds as in the challenged CON treatment, in which butyrate concentration was significantly higher than in the One-strain Pro treatment. Our findings indicated that the activity of these single- and multistrain probiotic products varies depending on rearing conditions, and the effect is highly strain- and product-specific. However, the multistrain probiotic apparently had more beneficial effects than the one-strain probiotic in the maintenance of gut functional status under optimal and challenge conditions.

The Interplay between Salmonella and Intestinal Innate Immune Cells in Chickens

Salmonellosis is a common infection in poultry, which results in huge economic losses in the poultry industry. At the same time, Salmonella infections are a threat to public health, since contaminated poultry products can lead to zoonotic infections. Antibiotics as feed additives have proven to be an effective prophylactic option to control Salmonella infections, but due to resistance issues in humans and animals, the use of antimicrobials in food animals has been banned in Europe. Hence, there is an urgent need to look for alternative strategies that can protect poultry against Salmonella infections. One such alternative could be to strengthen the innate immune system in young chickens in order to prevent early life infections. This can be achieved by administration of immune modulating molecules that target innate immune cells, for example via feed, or by in-ovo applications. We aimed to review the innate immune system in the chicken intestine; the main site of Salmonella entrance, and its responsiveness to Salmonella infection. Identifying the most important players in the innate immune response in the intestine is a first step in designing targeted approaches for immune modulation.

Itaconate regulates macrophage function through stressful iron-sulfur cluster disrupting and iron metabolism rebalancing

Lipopolysaccharide (LPS)-stimulated macrophages express an aconitate decarboxylase (IRG1, also called ACOD1), leading to accumulation of the endogenous metabolite itaconate. However, the precise mechanisms by which elevated itaconate levels alter macrophage function are not clear. Our hypothesis is itaconate affects macrophage function through some uncertain mechanism. Based on this, we established a transcriptional and proteomic signature of macrophages stimulated by itaconate and identified the pathways of IL-1β secretion and altered iron metabolism. Consistently, the effect of IRG1 deficiency on IL-1β secretion and iron metabolism was confirmed in IRG1 knockout THP-1 cell lines. Several common inhibitors and other compounds were used to examine the molecular mechanisms involved. Only cysteine and antioxidants (catechin hydrate) could inhibit caspase-1 activation and IL-1β secretion in itaconate-stimulated macrophages. We further found that aconitase activity was decreased by itaconate stimulation. Our results demonstrate the counteracting effects of overexpression of mitochondrial aconitase (ACO2, a tricarboxylic acid cycle enzyme) or cytosolic aconitase (ACO1, an iron regulatory protein) on IL-1β secretion and altered iron metabolism. Both enzyme activities were inhibited by itaconate because of iron-sulfur (Fe-S) cluster destruction. Our findings indicate that the immunoregulatory functions of IRG1 and itaconate in macrophages are stressful Fe-S cluster of aconitases disrupting and iron metabolism rebalancing.

Intra- and inter-breed variation in immune response to acute and sub-chronic Salmonella infection and commercial immune-stimulant in two-layer breeds

Salmonella is one of the most hazardous diseases in poultry farms. Markedly, the application of active immunostimulants is illustrated as potential protective agents against infection in poultry farms. Thus, this work aimed to explore inter- and intra-breed variation in response to acute and subchronic Salmonella enteritidis infection in two-layer breeds (one commercial [Hy-line strain] and another native [Fayoumi breed]). Besides exploring the possible protective effect of a commercial immune modulator (STIMULAN) on the two breeds during the acute infection. The ELISA antibody titer in sub-chronic infections and the expression analysis of some selected genes (IL-1β, LITAF, TGF-β, HSP90 and HSP70) are used as the clinical signs for acute infections to assess the possible protective role of a commercial immunomodulator (STIMULAN). Five groups were used during the acute experiment: G1-control; G2a-susceptible; G2b-resistant birds, G3-which received STIMULAN and G4-which received the infection + STIMULAN. The groups with sub-chronic infections include G1 (control), G2 (high antibody titer) and G3 (low antibody titer). The gene expressions among the susceptible birds during acute infection of both breeds are nearly similar. They only differ in the expression of HSP90 in the Fayoumi breed. However, the resistant birds vary in their gene expression profile. The effect of STIMULAN as a feed additive in non-infected birds was an up-regulation of LITAF, TGF-β, HSP90 in Fayoumi. Moreover, a powerful stimulatory role was observed when both breeds were infected. Both breeds were asymptomatic during the sub-chronic infection. Although, the increased expression of inflammatory-related genes in the Hy-line was considered as an indication of infection persistence. Fayoumi is capable of immune clearance for this infection. Thus, the Fayoumi breed is more resistant to acute Salmonella infection. HSP90 plays a vital role in its resistance. We recommend the use of STIMULAN as an immunomodulator during Salmonella infection.

Ovarian transcriptome profile from pre-laying period to broody period of Xupu goose

Xupu goose, a breed from Hunan province, produces high quality and quantity of meat and liver. However, its egg production rate is low, with poor reproductive traits but strong broody performance. These characteristics decrease the economic value of Xupu goose significantly. Here, RNA-seq was used to analyze the transcriptome changes of ovaries of Xupu goose at different stages to explore the molecular mechanism of reproduction from the pre-laying period to the broody period. A total of 258 genes were differentially expressed in the 3 stages. These genes are associated with inflammation, reproduction, mutual recognition and adhesion between cells, and cytoskeleton formation, and so on. In particular, we report, for the first time, the expression patterns of MRP126, serglycin, TXNIP, and FZD2 during the pre-laying, egg-laying, and broody periods of goose ovaries. Functional analysis by GO annotation revealed that GO terms were mainly involved in actin, cell signal transduction and regulation, and cellular components. Three pathways, including focal adhesion (gga04510), ECM-receptor interaction (gga04512), and N-Glycan biosynthesis (gga00510), were significantly enriched in the three groups. These findings provide a basis for further exploration of profiles of goose ovaries to improve egg production of Xupu goose.

Dual Transcriptomic Analyses Unveil Host-Pathogen Interactions Between Salmonella enterica Serovar Enteritidis and Laying Ducks (Anas platyrhynchos)

Salmonella enteritidis (SE) is a pathogen that can readily infect ovarian tissues and colonize the granulosa cell layer such that it can be transmitted via eggs from infected poultry to humans in whom it can cause food poisoning. Ducks are an important egg-laying species that are susceptible to SE infection, yet the host–pathogen interactions between SE and ducks have not been thoroughly studied to date. Herein, we performed dual RNA-sequencing analyses of these two organisms in a time-resolved infection model of duck granulosa cells (dGCs) by SE. In total, 10,510 genes were significantly differentially expressed in host dGCs, and 265 genes were differentially expressed in SE over the course of infection. These differentially expressed genes (DEGs) of dGCs were enriched in the cytokine–cytokine receptor interaction pathway via KEGG analyses, and the DEGs in SE were enriched in the two-component system, bacterial secretion system, and metabolism of pathogen factors pathways as determined. A subsequent weighted gene co-expression network analysis revealed that the cytokine–cytokine receptor interaction pathway is mostly enriched at 6 h post-infection (hpi). Moreover, a number of pathogenic factors identified in the pathogen–host interaction database (PHI-base) are upregulated in SE, including genes encoding the pathogenicity island/component, type III secretion, and regulators of systemic infection. Furthermore, an intracellular network associated with the regulation of SE infection in ducks was constructed, and 16 cytokine response-related dGCs DEGs (including IL15, CD40, and CCR7) and 17 pathogenesis-related factors (including sseL, ompR, and fliC) were identified, respectively. Overall, these results not only offer new insights into the mechanisms underlying host–pathogen interactions between SE and ducks, but they may also aid in the selection of potential targets for antimicrobial drug development.

A detailed analysis of innate and adaptive immune responsiveness upon infection with Salmonella enterica serotype Enteritidis in young broiler chickens

Salmonella enterica serotype Enteritidis (SE) is a zoonotic pathogen which causes foodborne diseases in humans as well as severe disease symptoms in young chickens. More insight in innate and adaptive immune responses of chickens to SE infection is needed to understand elimination of SE. Seven-day-old broiler chickens were experimentally challenged with SE and numbers and responsiveness of innate and adaptive immune cells as well as antibody titers were assessed. SE was observed in the ileum and spleen of SE-infected chickens at 7 days post-infection (dpi). At 1 dpi numbers of intraepithelial cytotoxic CD8⁺ T cells were significantly increased alongside numerically increased intraepithelial IL-2Rα⁺ and 20E5⁺ natural killer (NK) cells at 1 and 3 dpi. At both time points, activation of intraepithelial and splenic NK cells was significantly enhanced. At 7 dpi in the spleen, presence of macrophages and expression of activation markers on dendritic cells were significantly increased. At 21 dpi, SE-induced proliferation of splenic CD4⁺ and CD8⁺ T cells was observed and SE-specific antibodies were detected in sera of all SE-infected chickens. In conclusion, SE results in enhanced numbers and activation of innate cells and we hypothesized that in concert with subsequent specific T cell and antibody responses, reduction of SE is achieved. A better understanding of innate and adaptive immune responses important in the elimination of SE will aid in developing immune-modulation strategies, which may increase resistance to SE in young broiler chickens.

Tolerogenic Immunoregulation towards Salmonella Enteritidis Contributes to Colonization Persistence in Young Chicks

Long-term survival and the persistence of bacteria in the host suggest either host unresponsiveness or induction of an immunological tolerant response to the pathogen. The role of the host immunological response to persistent colonization of Salmonella Enteritidis (SE) in chickens remains poorly understood. In the current study, we performed a cecal tonsil transcriptome analysis in a model of SE persistent infection in 2-week-old chickens to comprehensively examine the dynamics of host immunological responses in the chicken gastrointestinal tract. Our results revealed overall host tolerogenic adaptive immune regulation in a major gut-associated lymphoid tissue, the cecal tonsil, during SE infection. Specifically, we observed consistent downregulation of the metallothionein 4 gene at all four postinfection time points (3, 7, 14, and 21 days postinfection [dpi]), which suggested potential pathogen-associated manipulation of the host zinc regulation as well as a possible immune modulatory effect. Furthermore, delayed activation in the B cell receptor signaling pathway and failure to sustain its active state during the lag phase of infection were further supported by an insignificant production of both intestinal and circulatory antibodies. Tug-of-war for interleukin 2 (IL-2) regulation between effector T cells and regulatory T cells appears to have consequences for upregulation in the transducer of ERBB2 (TOB) pathway, a negative regulator of T cell proliferation. In conclusion, this work highlights the overall host tolerogenic immune response that promotes persistent colonization by SE in young layer chicks.

Molecular mechanisms of growth depression in broiler chickens (Gallus Gallus domesticus) mediated by immune stress: a hepatic proteome study

Background

Immunological stress decreases feed intake, suppresses growth and induces economic losses. However, the underlying molecular mechanism remains unclear. Label-free liquid chromatography and mass spectrometry (LC-MS) proteomics techniques were employed to investigate effects of immune stress on the hepatic proteome changes of Arbor Acres broilers (Gallus Gallus domesticus) challenged with Escherichia coli lipopolysaccharide (LPS).

Results

Proteomic analysis indicated that 111 proteins were differentially expressed in the liver of broiler chickens from the immune stress group. Of these, 28 proteins were down-regulated, and 83 proteins were up-regulated in the immune stress group. Enrichment analysis showed that immune stress upregulated the expression of hepatic proteins involved in defense function, amino acid catabolism, ion transport, wound healing, and hormone secretion. Furthermore, immune stress increased valine, leucine and isoleucine degradation pathways.

Conclusion

The data suggests that growth depression of broiler chickens induced by immune stress is triggered by hepatic proteome alterations, and provides a new insight into the mechanism by which immune challenge impairs poultry production.

Proteomic analysis of chicken bone marrow-derived dendritic cells in response to an inactivated IBV + NDV poultry vaccine

Inactivated poultry vaccines are subject to routine potency testing for batch release, requiring large numbers of animals. The replacement of in vivo tests for cell-based alternatives can be facilitated by the identification of biomarkers for vaccine-induced immune responses. In this study, chicken bone marrow-derived dendritic cells were stimulated with an inactivated vaccine for infectious bronchitis virus and Newcastle disease virus, as well as inactivated infectious bronchitis virus only, and lipopolysaccharides as positive control, or left unstimulated for comparison with the stimulated samples. Next, the cells were lysed and subjected to proteomic analysis. Stimulation with the vaccine resulted in 66 differentially expressed proteins associated with mRNA translation, immune responses, lipid metabolism and the proteasome. For the eight most significantly upregulated proteins, mRNA expression levels were assessed. Markers that showed increased expression at both mRNA and protein levels included PLIN2 and PSMB1. Stimulation with infectious bronchitis virus only resulted in 25 differentially expressed proteins, which were mostly proteins containing Src homology 2 domains. Stimulation with lipopolysaccharides resulted in 118 differentially expressed proteins associated with dendritic cell maturation and antimicrobial activity. This study provides leads to a better understanding of the activation of dendritic cells by an inactivated poultry vaccine, and identified PLIN2 and PSMB1 as potential biomarkers for cell-based potency testing.

Characteristics of systemic infection and host responses in chickens experimentally infected with Salmonella enterica serovar Gallinarum biovar Gallinarum

Salmonella enterica serovar Gallinarum biovar Gallinarum (S. Gallinarum) is a host-specific pathogen causing systemic infection in poultry, which leads to significant economic losses due to high mortality. However, little is known about the dynamic process of systemic infection and pathogenic characteristics of S. Gallinarum in chickens. In the present study, we developed an oral infection model that reproduces the pathology of S. Gallinarum and clarified the host immune response of the infected chickens. Chickens at 20 days of age orally inoculated at a dose of 10⁸ colony forming unit (CFU) showed typical clinical signs of fowl typhoid and died between 6 and 10 days post infection. The inoculated S. Gallinarum rapidly disseminated to multple organs and the bacterial counts increased in the liver and spleen at 3 days post infection. Pathological changes associated wirh inflammation in the liver and spleen became apparent at 4 days post infection, and increased expression of interferon (IFN)-γ and interleuikin (IL)-12 in the liver and spleen did not observed until 3 days post infection. These results indicate that S. Gallinarum rapidly spread to entire body through intestine, and the low-level of inflammatory responses in the liver during the early stage of infection may contribute to rapid, systemic dissemination of the bacteria. Our infection model and findings will contribute to the better understanding of the pathogenic mechanism of S. Gallinarum, and provide new insights into the prevention and control of fowl typhoid.

Health monitoring in birds using bio-loggers and whole blood transcriptomics

Monitoring and early detection of emerging infectious diseases in wild animals is of crucial global importance, yet reliable ways to measure immune status and responses are lacking for animals in the wild. Here we assess the usefulness of bio-loggers for detecting disease outbreaks in free-living birds and confirm detailed responses using leukocyte composition and large-scale transcriptomics. We simulated natural infections by viral and bacterial pathogens in captive mallards (Anas platyrhynchos), an important natural vector for avian influenza virus. We show that body temperature, heart rate and leukocyte composition change reliably during an acute phase immune response. Using genome-wide gene expression profiling of whole blood across time points we confirm that immunostimulants activate pathogen-specific gene regulatory networks. By reporting immune response related changes in physiological and behavioural traits that can be studied in free-ranging populations, we provide baseline information with importance to the global monitoring of zoonotic diseases.

Dietary Bacillus subtilis C-3102 Supplementation Enhances the Exclusion of Salmonella enterica from Chickens

Among the reported probiotic Bacillus strains, B. subtilis C-3102 has the unique potential to improve feed uptake under stress conditions in the broilers, piglets, and cows. In this study, we sought to evaluate the protective effect of feed additive probiotic Bacillus subtilis C-3102 against Salmonella enterica infection of specific pathogen-free (SPF) chicks in floor pens in two experiments. In the experiment-1, the chicks in the control group (n=32) were fed a basal diet and those in the C-3102 group (n=32) were fed a basal diet supplemented with 1×106 CFU/g of feed for 28 days. On day 7 post-challenge with S. enterica, there was no significant change in the body weight between both the groups throughout the test period, whereas detection rates of S. enterica in the C-3102 group were significantly lower in the cecum and liver on days 21 and 14 post-challenge, respectively. In the experiment-2, minimum dosage of C-3102 cells required to protect Salmonella infection was evaluated using 3 dosages. Chicks were divided into four groups, fed with different dosages of C-3102 (1×106, 5×105, 3×105, and 0 CFU/g of feed), and challenged with S. enterica (2.8×108 CFU/chicken). S. enterica infection was completed within 7 days post- challenge and was almost excluded from the liver and spleen on day 21 post- challenge in the control group. Average values showed a trend for higher infection rates in the control group >3×105>5×105>1×106 CFU/g on days 14 and 21 post-challenge. These results suggest that B. subtilis C-3102 supplementation has the potential to reduce S. enterica infection rates and/or to accelerate the exclusion of S. enterica from the chicks.

Effects of Essential Oils-Based Supplement and Salmonella Infection on Gene Expression, Blood Parameters, Cecal Microbiome, and Egg Production in Laying Hens

One of the main roles in poultry resistance to infections caused by Salmonella is attributed to host immunity and intestinal microbiota. We conducted an experiment that involved challenging Lohmann White laying hens with Salmonella Enteritidis (SE), feeding them a diet supplemented with an EOs-based phytobiotic Intebio^®. At 1 and 7 days post-inoculation, the expression profiles of eight genes related to immunity, transport of nutrients in the intestine, and metabolism were examined. Cecal microbiome composition and blood biochemical/immunological indices were also explored and egg production traits recorded. As a result, the SE challenge of laying hens and Intebio^® administration had either a suppressive or activating effect on the expression level of the studied genes (e.g., IL6 and BPIFB3), the latter echoing mammalian/human tissue-specific expression. There were also effects of the pathogen challenge and phytobiotic intake on the cecal microbiome profiles and blood biochemical/immunological parameters, including those reflecting the activity of the birds' immune systems (e.g., serum bactericidal activity, β-lysine content, and immunoglobulin levels). Significant differences between control and experimental subgroups in egg performance traits (i.e., egg weight/number/mass) were also found. The phytobiotic administration suggested a positive effect on the welfare and productivity of poultry.

Transcriptional response of blood leukocytes from turkeys challenged with Salmonella enterica serovar Typhimurium UK1

Non-typhoidal Salmonella is one of the most common causes of bacterial foodborne disease and consumption of contaminated poultry products, including turkey, is one source of exposure. Minimizing Salmonella colonization of commercial turkeys could decrease the incidence of Salmonella-associated human foodborne illness. Understanding host responses to these bacteria is critical in developing strategies to minimize colonization and reduce food safety risk. In this study, we evaluated bacterial load and blood leukocyte transcriptomic responses of 3-week-old turkeys challenged with the Salmonella enterica serovar Typhimurium (S. Typhimurium) UK1 strain. Turkeys (n = 8/dose) were inoculated by oral gavage with 10⁸ or 10¹⁰ colony forming units (CFU) of S. Typhimurium UK1, and fecal shedding and tissue colonization were measured across multiple days post-inoculation (dpi). Fecal shedding was 1-2 log₁₀ higher in the 10¹⁰ CFU group than the 10⁸ CFU group, but both doses effectively colonized the crop, spleen, ileum, cecum, colon, bursa of Fabricius and cloaca without causing any detectable clinical signs in either group of birds. Blood leukocytes were isolated from a subset of the birds (n = 3-4/dpi) both pre-inoculation (0 dpi) and 2 dpi with 10¹⁰ CFU and their transcriptomic responses assayed by RNA-sequencing (RNA-seq). At 2 dpi, 647 genes had significant differential expression (DE), including large increases in expression of immune genes such as CCAH221, IL4I1, LYZ, IL13RA2, IL22RA2, and ACOD1. IL1β was predicted as a major regulator of DE in the leukocytes, which was predicted to activate cell migration, phagocytosis and proliferation, and to impact the STAT3 and toll-like receptor pathways. These analyses revealed genes and pathways by which turkey blood leukocytes responded to the pathogen and can provide potential targets for developing intervention strategies or diagnostic assays to mitigate S. Typhimurium colonization in turkeys.

mRNA expression and functional analysis of chicken IFIT5 after infected with Newcastle disease virus

Innate immunity is the first line against the invasion of pathogenic microorganisms. Over the past several years, the antiviral activity and mechanisms of the IFIT5 gene have been confirmed in mammals. However, more information is needed on the role of IFIT5 in response to viral infection in chickens. In this study, we examined the mRNA expression profile of chicken IFIT5 (chIFIT5) in different tissues and explored how chIFIT5 transduces upstream signaling to the downstream adaptor. Relative mRNA expression level of chIFIT5 was the highest in spleen and expression level of chIFIT5 was significantly up-regulated following Newcastle disease virus (NDV) infection, and polyinosinic:polycytidylic acid [poly (I:C)]- and poly(deoxyadenylic-thymidylic) [poly (dA:dT)]-triggered antiviral immune responses. Chicken MDA5, MAVS, and IRF7 positively regulated the mRNA expression of chIFIT5. Overexpression of chIFIT5 could promote IRF7- and NF-κB-mediated gene expression following NDV infection or transfection with poly (I:C). These results suggested that chIFIT5 is an important enhancer of the innate immunity response.

Transcriptome profiling analysis of caeca in chicks challenged with Salmonella Typhimurium reveals differential expression of genes involved in host mucosal immune response

Temporal regulation of global gene expression in the caeca of chickens infected with Salmonella Typhimurium has not been investigated previously. In this study, we performed the transcriptome analysis of the caeca of Salmonella Typhimurium challenged chicks to understand the regulation of the mucosal immune system in a temporal manner. The Salmonella infection resulted in the activation of the caecal immune system by the upregulation of the differentially expressed genes (DEGs; false discovery rate (FDR) < 0.05; log₂ fold change > 1) involved in biological pathways such as Toll-like receptor signaling pathway, Salmonella infection, cytokine-cytokine receptor interaction, phagosome, apoptosis and intestinal immune network for IgA production. The activation of biological pathways such as RIG-I-like receptor signaling pathway, ErbB signaling pathway and cellular senescence showed a time-dependent response of the host immune system. A 49% increase in the DEGs on day 7 compared with day 3 post-infection (p.i.) suggested a time-dependent role of multiple genes such as AvBD1, AvBD2, AvBD7, IL2, IL10, IL21, SIVA1, CD5, CD14 and GPR142 in the regulation of the immune system. Nested network analysis of the individual biological pathways showed that IL6 played a significant role in the immune system regulation by activating the pathways, including Toll-like receptor signaling pathway, Salmonella infection, intestinal immune network for IgA production and C-type lectin receptor signaling pathway. The downregulated DEGs (FDR < 0.05; log₂ fold change < -1) showed that Salmonella challenge affected the functions of pathways, such as tryptophan metabolism, retinol metabolism, folate biosynthesis and pentose and glucoronate interconversions, suggesting the disruption of cellular mechanisms involved in nutrient synthesis, absorption and metabolism. Overall, the immune response was temporally regulated through the activation of Toll-like signaling receptor pathway, cytokine-cytokine interactions and Salmonella infection, where IL6 played a significant role in the modulation of caecal immune system against Salmonella Typhimurium. KEY POINTS: • The immune response to Salmonella Typhimurium challenge was temporally regulated in the caeca of chickens. • Many newly identified genes have been shown to be involved in the activation of the immune system. • Toll-like receptors and interleukins played a key role in immune system regulation.

Iron-Uptake Systems of Chicken-Associated Salmonella Serovars and Their Role in Colonizing the Avian Host

Iron is an essential micronutrient for most bacteria. Salmonella enterica strains, representing human and animal pathogens, have adopted several mechanisms to sequester iron from the environment depending on availability and source. Chickens act as a major reservoir for Salmonella enterica strains which can lead to outbreaks of human salmonellosis. In this review article we summarize the current understanding of the contribution of iron-uptake systems to the virulence of non-typhoidal S. enterica strains in colonizing chickens. We aim to address the gap in knowledge in this field, to help understand and define the interactions between S. enterica and these important hosts, in comparison to mammalian models.

The correlated expression of immune and energy metabolism related genes in the response to Salmonella enterica serovar Enteritidis inoculation in chicken

Background

Salmonella enterica serovar Enteritidis (SE) is one of the food-borne pathogenic bacteria, which affects poultry production and poses severe threat to human health. The correlation of immune system and metabolism in chicken after SE inoculation is important but not clear. In the current study, we identified the expression of immune and energy metabolism related genes using quantitative PCR to evaluate the correlation between immune system and energy metabolism against SE inoculation in Jining Bairi chicken.

Results

ATP5G1, ATP5G3 and ND2 were significantly up-regulated at 1 dpi (day post inoculation), and ATP5E, ATP5G1, ATP5G3 were significantly down-regulated at 7 dpi (P < 0.05). IL-8 and IL-1β were significantly down-regulated at 1 dpi, IL-8 and IL-18 were significantly down-regulated at 3 dpi, IL-8 and BCL10 were significantly up-regulated at 7 dpi (P < 0.05).

Conclusions

These findings indicate that the correlation between immune and energy metabolism related genes gradually change with time points post SE inoculation, from one homeostasis to an opposite homeostasis with 3 dpi as a turning point. These results will pave the foundation for the relationship between immune system and energy metabolism in the response to SE inoculation in chicken.

The Differential Phosphorylation-Dependent Signaling and Glucose Immunometabolic Responses Induced during Infection by Salmonella Enteritidis and Salmonella Heidelberg in Chicken Macrophage-like cells

Salmonella is a burden to the poultry, health, and food safety industries, resulting in illnesses, food contamination, and recalls. Salmonella enterica subspecies enterica Enteritidis (S. Enteritidis) is one of the most prevalent serotypes isolated from poultry. Salmonella enterica subspecies enterica Heidelberg (S. Heidelberg), which is becoming as prevalent as S. Enteritidis, is one of the five most isolated serotypes. Although S. Enteritidis and S. Heidelberg are almost genetically identical, they both are capable of inducing different immune and metabolic responses in host cells to successfully establish an infection. Therefore, using the kinome peptide array, we demonstrated that S. Enteritidis and S. Heidelberg infections induced differential phosphorylation of peptides on Rho proteins, caspases, toll-like receptors, and other proteins involved in metabolic- and immune-related signaling of HD11 chicken macrophages. Metabolic flux assays measuring extracellular acidification rate (ECAR) and oxygen consumption rate (OCR) demonstrated that S. Enteritidis at 30 min postinfection (p.i.) increased glucose metabolism, while S. Heidelberg at 30 min p.i. decreased glucose metabolism. S. Enteritidis is more invasive than S. Heidelberg. These results show different immunometabolic responses of HD11 macrophages to S. Enteritidis and S. Heidelberg infections.

ACOD1 in immunometabolism and disease

Immunometabolism plays a fundamental role in health and diseases and involves multiple genes and signals. Aconitate decarboxylase 1 (ACOD1; also known as IRG1) is emerging as a regulator of immunometabolism in inflammation and infection. Upregulation of ACOD1 expression occurs in activated immune cells (e.g., macrophages and monocytes) in response to pathogen infection (e.g., bacteria and viruses), pathogen-associated molecular pattern molecules (e.g., LPS), cytokines (e.g., TNF and IFNs), and damage-associated molecular patterns (e.g., monosodium urate). Mechanistically, several immune receptors (e.g., TLRs and IFNAR), adapter proteins (e.g., MYD88), ubiquitin ligases (e.g., A20), and transcription factors (e.g., NF-κB, IRFs, and STATs) form complex signal transduction networks to control ACOD1 expression in a context-dependent manner. Functionally, ACOD1 mediates itaconate production, oxidative stress, and antigen processing and plays dual roles in immunity and diseases. On the one hand, activation of the ACOD1 pathway may limit pathogen infection and promote embryo implantation. On the other hand, abnormal ACOD1 expression can lead to tumor progression, neurodegenerative disease, and immune paralysis. Further understanding of the function and regulation of ACOD1 is important for the application of ACOD1-based therapeutic strategies in disease.

Impact of Dietary Manganese on Intestinal Barrier and Inflammatory Response in Broilers Challenged with Salmonella Typhimurium

Growing concern for public health and food safety has prompted a special interest in developing nutritional strategies for removing waterborne and foodborne pathogens, including Salmonella. Strong links between manganese (Mn) and intestinal barrier or immune function hint that dietary Mn supplementation is likely to be a promising approach to limit the loads of pathogens in broilers. Here, we provide evidence that Salmonella Typhimurium (S. Typhimurium, 4 × 10⁸ CFUs) challenge-induced intestinal injury along with systemic Mn redistribution in broilers. Further examining of the effect of dietary Mn treatments (a basal diet plus additional 0, 40, or 100 mg Mn/kg for corresponding to Mn-deficient, control, or Mn-surfeit diet, respectively) on intestinal barrier and inflammation status of broilers infected with S. Typhimurium revealed that birds fed the control and Mn-surfeit diets exhibited improved intestinal tight junctions and microbiota composition. Even without Salmonella infection, dietary Mn deficiency alone increased intestinal permeability by impairing intestinal tight junctions. In addition, when fed the control and Mn-surfeit diets, birds showed decreased Salmonella burdens in cecal content and spleen, with a concomitant increase in inflammatory cytokine levels in spleen. Furthermore, the dietary Mn-supplementation-mediated induction of cytokine production was probably associated with the nuclear factor kappa-B (NF-κB)/hydrogen peroxide (H₂O₂) pathway, as judged by the enhanced manganese superoxide dismutase activity and the increased H₂O₂ level in mitochondria, together with the increased mRNA level of NF-κB in spleen. Ingenuity-pathway analysis indicated that acute-phase response pathways, T helper type 1 pathway, and dendritic cell maturation were significantly activated by the dietary Mn supplementation. Our data suggest that dietary Mn supplementation could enhance intestinal barrier and splenic inflammatory response to fight against Salmonella infection in broilers.

Interleukin 4 inducible 1 gene (IL4I1) is induced in chicken phagocytes by Salmonella Enteritidis infection

In attempt to identify genes that are induced in chickens by Salmonella Enteritidis we identified a new highly inducible gene, interleukin 4 induced 1 gene (IL4I1). IL4I1 reached its peak expression (458× induction) in the cecum of newly hatched chickens 4 days post-infection and remained upregulated for an additional 10 days. IL4I1 was expressed and induced in macrophages and granulocytes, both at the mRNA and protein level. IL4I1 was expressed and induced also in CD4 and γδ T-lymphocytes though at a 50-fold lower level than in phagocytes. Expression of IL4I1 was not detected in CD8 T lymphocytes or B lymphocytes. Mutation of IL4I1 in chicken HD11 macrophages did not affect their bactericidal capacity against S. Enteritidis but negatively affected their oxidative burst after PMA stimulation. We therefore propose that IL4I1 is not directly involved in bactericidal activity of phagocytes and, instead, it is likely involved in the control of inflammatory response and signaling to T and B lymphocytes.

Tissue-, age- and dose-dependent changes in avian β-defensin and LEAP2 mRNA abundance in the intestines of Salmonella Typhimurium challenged broilers

Salmonella is a pathogen normally found in the gastrointestinal tract of poultry. The objective of this study was to determine changes in avian β-defensin (AvBD) and liver-enriched antimicrobial peptide 2 (LEAP2) mRNA following Salmonella challenge. Day of hatch chicks were challenged with 10⁶, 10⁷ or 10⁸ colony-forming units (cfu) of Salmonella typhimurium. There were dose-, tissue- and age-specific changes in AvBD and LEAP2 mRNA. At 1-day post-infection (dpi) there was a transient upregulation of AvBD1, 8, 10 and 12 mRNA in the 10⁸ cfu group. At 5 dpi, all seven AvBD mRNA were downregulated in the ileum, while only AvBD1, 6, 10 and 11 mRNA were downregulated in the jejunum and AvBD6, 8, 10, 12 and 13 were downregulated in the cecum. At 7 dpi, there was downregulation of all seven AvBD mRNA in the duodenum and downregulation of selected AvBD in the jejunum, ileum and cecum. LEAP2 mRNA was downregulated at all doses of Salmonella in the cecum at 1 dpi and in the ileum at 5 dpi. In summary, Salmonella infection caused an initial upregulation followed by a downregulation of AvBD mRNA.

Avian MRP126 Restricts Microbial Growth through Ca(II)-Dependent Zn(II) Sequestration

The calgranulins form a class of S100 proteins in higher vertebrates that innate-immune cells release in abundance at infection sites. These proteins function by binding transition metal ions to prevent microbial pathogens from obtaining those essential nutrients. Mammals express three distinct members of this family: S100A8 (calgranulin A), S100A9 (calgranulin B, which heterooligomerizes with S100A8 to form calprotectin), and S100A12 (calgranulin C), that exhibit Ca(II)-dependent transition metal binding properties. Human calprotectin effectively sequesters Mn(II), Fe(II), Ni(II), and Zn(II), whereas human S100A12 selectively sequesters Zn(II) over these other metal ions. Birds and reptiles express a single calgranulin homologue named MRP126, which we reasoned could have properties more similar to those of either calprotectin or S100A12. Here we present the purification and biophysical characterization of recombinant chicken MRP126 and, to the best of our knowledge, provide the first assessment of the metal binding and antimicrobial properties of an avian MRP126. We show that MRP126 is a homodimer that selectively sequesters Zn(II) and restricts the growth of certain microbes. MRP126 binds Zn(II) at two canonical His₃Asp sites. The presence of excess Ca(II) increases the affinity of the His₃Asp sites from the low-nanomolar to the low-picomolar range, thereby enhancing antimicrobial activity. Chicken MRP126 also binds additional Zn(II) equivalents with low-nanomolar affinity at two nonconserved dicysteine sites and with high-nanomolar affinity using a histidine-rich C-terminal tail that is a hallmark of this clade of calgranulins. Our results with chicken MRP126 suggest that Ca(II)-dependent Zn(II) sequestration was a role of the last common ancestor of calgranulin proteins, with mammalian calprotectin subsequently evolving a broader metal binding repertoire.

Global Mapping of H3K4 Trimethylation (H3K4me3) and Transcriptome Analysis Reveal Genes Involved in the Response to Epidemic Diarrhea Virus Infections in Pigs

Porcine epidemic diarrhea virus (PEDV) is currently detected as the main pathogen causing severe diarrhea in pig farms. The phenotypic alterations induced by pathogenic infections are usually tightly linked with marked changes in epigenetic modification and gene expression. We performed global mapping of H3K4 trimethylation (H3K4me3) and transcriptomic analyses in the jejunum of PEDV-infected and healthy piglets using chromatin immunoprecipitation sequencing and RNA-seq techniques. A total of 1885 H3K4me3 peaks that are associated with 1723 genes were characterized. Moreover, 290 differentially expressed genes were identified, including 104 up-regulated and 186 down-regulated genes. Several antiviral genes including 2'-5'-oligoadenylate synthetase 1 (OAS1), 2'-5'-oligoadenylate synthetase 2 (OAS2), ephrin B2 (EFNB2), and CDC28 protein kinase regulatory subunit 1B (CKS1B) with higher H3K4me3 enrichment and expression levels in PEDV-infected samples suggested the potential roles of H3K4me3 deposition in promoting their expressions. Transcription factor annotation analysis highlighted the potential roles of two transcription factors interferon regulatory factor 8 (IRF8) and Kruppel like factor 4 (KLF4) in modulating the differential expression of genes involved in PEDV infection. The results provided novel insights into PEDV infection from the transcriptomic and epigenetic layers and revealed previously unknown and intriguing elements potentially involved in the host responses.

Changes in the intestinal mucosal proteome of turkeys (Meleagris gallopavo) infected with haemorrhagic enteritis virus

Haemorrhagic enteritis (HE) is a viral disease affecting intestinal integrity and barrier function in turkey (Meleagris gallopavo) and resulting in a significant economic loss. Sequential Windowed Acquisition of All Theoretical Fragment Ion Mass Spectra (SWATH-MS) was applied to identify crucial proteins involved in HE infection. A total of 938 proteins were identified and used to generate a reference library for SWATH-MS analysis. In total, 523 proteins were reliably quantified, and 64 proteins were found to be differentially expressed, including 49 up-regulated and 15 down-regulated proteins between healthy and HE-affected intestinal mucosa. Functional analysis suggested that these proteins were involved in the following categories of cellular pathways and metabolisms: 1) energy pathways; 2) intestine lipid and amino acid metabolism; 3) oxidative stress; 4) intestinal immune response. Major findings of this study demonstrated that natural HE infection is related to the changes in abundance of several proteins involved in cell-intrinsic immune defense against viral invasion, systemic inflammation, modulation of excessive inflammation, B and T cell development and function and antigen presentation. mRNA quantitative expression demonstrated that most of the proteins involved in innate immunity that were found to be differentially abundant were produced by intestinal mucosa, suggesting its direct involvement in immune defences against HE infection.

Conserved, breed-dependent, and subline-dependent innate immune responses of Fayoumi and Leghorn chicken embryos to Newcastle disease virus infection

Newcastle disease virus (NDV) is a threat to the global poultry industry, but particularly for smallholder farmers in low- and middle-income countries. Previous reports suggest that some breeds of chickens are less susceptible to NDV infection, however, the mechanisms contributing to this are unknown. We here examined the comparative transcriptional responses of innate immune genes to NDV infection in inbred sublines of the Fayoumi and Leghorn breeds known to differ in their relative susceptibility to infection as well as at the microchromosome bearing the major histocompatability complex (MHC) locus. The analysis identified a set of five core genes, Mx1, IRF1, IRF7, STAT1, and SOCS1, that are up-regulated regardless of subline. Several genes were differentially expressed in a breed- or subline-dependent manner. The breed-dependent response involved TLR3, NOS2, LITAF, and IFIH1 in the Fayoumi versus IL8, CAMP, and CCL4 in the Leghorn. Further analysis identified subline-dependent differences in the pro-inflammatory response within the Fayoumi breed that are likely influenced by the MHC. These results have identified conserved, breed-dependent, and subline-dependent innate immune responses to NDV infection in chickens, and provide a strong framework for the future characterization of the specific roles of genes and pathways that influence the susceptibility of chickens to NDV infection.

Evaluation of the Dietary Supplementation of a Formulation Containing Ascorbic Acid and a Solid Dispersion of Curcumin with Boric Acid against Salmonella Enteritidis and Necrotic Enteritis in Broiler Chickens

Two experiments were conducted to evaluate the effect of the prophylactic or therapeutic administration of a 0.1% mixture containing ascorbic acid and a solid dispersion of curcumin with polyvinylpyrrolidone and boric acid (AA-CUR/PVP-BA) against Salmonella Enteritidis (S. Enteritidis) in broiler chickens. A third experiment was conducted to evaluate the impact of the dietary administration of 0.1% AA-CUR/PVP-BA in a necrotic enteritis (NE) model in broiler chickens. The prophylactic administration of 0.1% AA-CUR/PVP-BA significantly decreased S. Enteritidis colonization in cecal tonsils (CT) when compared to the positive control group (PC, p < 0.05). The therapeutic administration of 0.1% AA-CUR/PVP-BA significantly reduced the concentration of S. Enteritidis by 2.05 and 2.71 log in crop and CT, respectively, when compared with the PC on day 10 post-S. Enteritidis challenge. Furthermore, the serum FITC-d concentration and total intestinal IgA levels were also significantly lower in chickens that received 0.1% AA-CUR/PVP-BA. Contrary, the PC group showed significantly higher total intestinal IgA levels compared to the negative control or AA-CUR/PVP-BA groups in the NE model. However, 0.1% AA-CUR/PVP-BA showed a better effect in reducing the concentration of S. Enteritidis when compared to the NE model. Further studies with higher concentration of AA-CUR/PVP-BA into the feed to extend these preliminary results are currently being evaluated.

Gene expression and antibody response in chicken against Salmonella Typhimurium challenge

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a primary avian pathogen responsible for severe intestinal pathology in younger chickens and economic losses to poultry industry. Furthermore, S. Typhimurium is also able to cause infection in humans, characterized by acute gastrointestinal disease. A study was conducted to investigate antibody response and expression kinetics of interferon gamma (IFNγ), interleukin (IL-12, and IL-18) genes in broiler chicken at 0, 1, 3, 5, 7, 9, 11, 13, and 15 D post infection following experimental infection of S. Typhimurium. Immunological studies showed higher titres of IgG and IgM in the infected group as compared to the age-matched un-infected control group. The Real-Time PCR-based gene expression analysis revealed significant increase of IFNγ, IL-12, and IL-18 mRNA levels in the infected group as compared to their respective controls (P < 0.05). The present study shall help in understanding the immune responses in birds, thus allowing development of more effective vaccines and vaccination strategies.

Contact with adult hen affects development of caecal microbiota in newly hatched chicks

Chickens in commercial production are hatched in a clean hatchery environment in the absence of any contact with adult hens. However, Gallus gallus evolved to be hatched in a nest in contact with an adult hen which may act as a donor of gut microbiota. In this study, we therefore addressed the issue of microbiota development in newly hatched chickens with or without contact with an adult hen. We found that a mere 24-hour-long contact between a hen and newly hatched chickens was long enough for transfer of hen gut microbiota to chickens. Hens were efficient donors of Bacteroidetes and Actinobacteria. However, except for genus Faecalibacterium and bacterial species belonging to class Negativicutes, hens did not act as an important source of Gram-positive Firmicutes. Though common to the chicken intestinal tract, Lactobacilli and isolates from families Erysipelotrichaceae, Lachnospiraceae and Ruminococcaceae therefore originated from environmental sources instead of from the hens. These observation may have considerable consequences for the evidence-based design of the new generation of probiotics for poultry.

Patterns of community assembly in the developing chicken microbiome reveal rapid primary succession

The fine‐scale temporal dynamics of the chicken gut microbiome are unexplored, but thought to be critical for chicken health and productivity. Here, we monitored the fecal microbiome of healthy chickens on days 1–7, 10, 14, 21, 28, and 35 after hatching, and performed 16S rRNA amplicon sequencing in order to obtain a high‐resolution census of the fecal microbiome over time. In the period studied, the fecal microbiomes of the developing chickens showed a linear‐log increase in community richness and consistent shifts in community composition. Three successional stages were detected: the first stage was dominated by vertically transmitted or rapidly colonizing taxa including Streptococcus and Escherichia/Shigella; in the second stage beginning on day 4, these taxa were displaced by rapid‐growing taxa including Lachnospiraceae and Ruminococcus‐like species variants; and in the third stage, starting on day 10, slow‐growing, specialist taxa including Candidatus Arthrobacter and Romboutsia were detected. The patterns of displacement and the previously reported ecological characteristics of many of the dominant taxa observed suggest that resource competition plays an important role in regulating successional dynamics in the developing chicken gut. We propose that the boundaries between successional stages (3–4 and 14–21 days after hatching) may be optimal times for microbiome interventions.