Toll-like receptors gene expression in the gastrointestinal tract of Salmonella serovar Pullorum-infected broiler chicken

Differential expression of Toll-like receptors and associated cytokines in the bursa of Eimeria tenella infected chickens

Chicken coccidiosis, caused by Eimeria spp., is an economically important disease of commercial poultry. Innate immunity ensures an immediate response to invading parasites, and Toll-like receptors (TLRs) are major components of the innate immune system. However, few systematic studies have been reported on the roles of TLRs in chickens infected with Eimeria. In the present study, 14-day-old chickens were infected orally with 50,000 E. tenella oocysts and the bursa of Fabricius was dissected at different time points. Expression profiles of 10 chicken TLRs (chTLRs) and associated cytokines were determined by quantitative real-time PCR. The results showed that chTLR1a and chTLR2a peaked significantly at 3 h post-infection (p < 0.05), while other chTLRs displayed different expression profiles; chTLR1b, chTLR2b, chTLR5, and chTLR15 peaked at 48 h post-infection, while chTLR4, chTLR7, and chTLR21 peaked at 144 h post-infection. ChTLR3 expression was the highest among chTLRs, peaking at 96 h post-infection (p < 0.05). For cytokines, interleukin (IL)-6, IL-12, IL-17, and interferon-γ peaked at 12 h post-infection, while IL-4 peaked at 24 h post-infection. The results provide a valuable overview of the expression profiles of innate immune molecules during E. tenella infection in chicken bursa, and indicate that innate immune responses may mediate resistance to chicken coccidiosis.

The host susceptibility/resistance-related genes and gut microbial characteristics in Salmonella pullorum-infected chickens

Pullorum disease is a bacterial disease caused by Salmonella pullorum in chickens, which is characterized by gastrointestinal infection and diarrhea. In traditional perspectives, research on pullorum disease primarily focused on clinical symptoms, epidemiological characteristics, and the pathogenic sites. This study, however, approaches the subject from the standpoint of host genetic basis and gut microbiota. For the positive and negative offspring chicks, which are the offspring of positive roosters and hens and negative roosters and hens, respectively, we conducted whole-genome association analysis and identified 195 SNPs and 79 significant InDels on the host genome that were associated with susceptibility/resistance to pullorum disease. A total of 77 genes were annotated, among which MYH7, ATP2A3, and CACNA1S exhibited variations in the exons. After infection with S. pullorum, the diversity and community structure of the gut microbiota in the chicken also underwent significant changes. Lactobacillus, Escherichia_Shigella, and Klebsiella were dominant bacteria in the dead negative offspring chicks with significantly higher abundance compared to the survival negative offspring chicks. These significant changes in host genome and bacterial abundance suggest that they may be associated with the susceptibility/resistance of pullorum disease.IMPORTANCEPullorum disease can be transmitted vertically and horizontally. Population purification and antibiotic treatment are the main methods for preventing and treating this disease, but they are associated with issues, such as high cost, poor accuracy, bacterial resistance, and overused antibiotics. In traditional perspectives, research on pullorum disease primarily focused on clinical symptoms, epidemiological characteristics, and the pathogenic sites. This study, however, approaches the subject from the standpoint of host genetic basis and gut microbiota. Using the genome-wide association analysis and microbiome comparison analysis, with chicken death and survival following Salmonella pullorum infection as phenotypes, we identified significant genetic variations (e.g., MYH7, ATP2A3, and CACNA1S) and gut microbiota (e.g., Lactobacillus, Escherichia_Shigella, Bacillus, and Enterococcus_cecorum) that may relate to susceptibility/resistance of pullorum disease. These results indicate that the infection of chickens with S. pullorum and the achievement of vertical transmission may be related to the host genome and gut microbiota.

Bacteriophage-based control of Salmonella on table eggs and breeding eggs in poultry

Salmonella is a major foodborne pathogen, that poses a serious threat to poultry farm production. Phage-based biocontrol offered a promising alternative strategy to eradicate the persistent and challenging infections caused by Salmonella in this setting. This study isolated and purified the lytic Salmonella phage vB_SenM_BP13076 (simple as BP13076) using its host strain Salmonella Enteritidis ATCC 13076. Its genome was extensively analyzed, and its potential biocontrol application towards eggs was investigated. Morphological analyses revealed that phage BP13076 is characterized by an icosahedral head and a contractile tail, placing it among Caudoviricetes. The phage demonstrated a broad host range, lysing 66 out of 68 tested Salmonella strains, including eight globally prevalent serovars. Moreover, it also exhibited a short latent period of approximately 5 min and a burst size of about 105 PFU/cell. It also demonstrates good thermal stability and a wide pH range tolerance. The genome of phage BP13076 consists of 160, 318 bp of dsDNA with a G + C content of 37.13% with nucleotide homology placing it among phages of the genus Gelderlandvirus. Notably, the genomic analysis revealed no known genes associated with virulence, antibiotic resistance, or lysogeny, making it a safe candidate for biocontrol applications. In vitro, bacteriostatic tests indicated higher MOI (multiplicity of infection), resulting in a more significant reduction in Salmonella counts. When applied to table and breeding eggs, phage BP13076 at MOIs of 100 and 1000 resulted in a significant decrease in Salmonella levels compared to the positive control groups. These findings highlight the efficacy of phage BP13076 as a promising biocontrol agent for managing Salmonella contamination and transmission for table and breeding eggs, offering a foundation for its potential application in the prevention and control of Salmonella in the poultry industry.

The Combined Use of Cinnamaldehyde and Vitamin C Is Beneficial for Better Carcass Character and Intestinal Health of Broilers

The use of cinnamaldehyde and Vitamin C can improve immunity and intestinal health. A two-way factorial design was employed to investigate the main and interactive effects of cinnamaldehyde and vitamin C on the growth, carcass, and intestinal health of broiler chickens. A total of 288 one-day-old female Arbor Acres broiler chicks were randomly distributed among four treatment groups, consisting of six replicate cages with 12 birds each. Four treatments were basal diet or control (CON), supplemental cinnamaldehyde (CA) 300 g/ton (g/t), vitamin C (VC) 300 g/t, and cinnamaldehyde 300 g/t, and vitamin C 300 g/t (CA + VC), respectively. The results showed that supplemental CA did not affect the growth performance or slaughter performance of broilers at 21 days (d), 42 days (d), and 1-42 days (d); however, it could improve intestinal barrier function at 42 d of age and reduce the mRNA expression of inflammatory factors in the intestine at 21 d and 42 d of age. Supplemental VC showed a trend towards increasing body weight gain (BWG) at 21 d (p = 0.094), increased breast muscle rate (at 21-d 5.33%, p < 0.05 and at 42-d 7.09%, p = 0.097), and decreased the abdominal fat (23.43%, p < 0.05) and drip loss (20.68%, p < 0.05) at 42-d. Moreover, VC improves intestinal morphology and intestinal barrier function and maintains a balanced immune response. The blend of CA and VC significantly upregulated the mRNA expression of myeloid differentiation factor 88 (MyD-88) in the intestine at 21 d of age, the mRNA expression of catalase (CAT), Occludin, Claudin-1, Mucin-2, nuclear factor-kappa B (NF-κB) and toll-like receptor 4 (TLR-4) in the intestine at 42 d of age (p < 0.01), and downregulated the mRNA expression of interleukin 10 (IL-10), interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-α) in the intestine at 21-d and 42-d of age, and interleukin-1 beta (IL-1β) mRNA in intestine at 42 d of age (p < 0.01). This study suggested that the combination of CA and VC had the potential to regulate intestinal health and result in better carcass character of broilers.

Expression of Toll-like receptors and host defence peptides in the cecum of chicken challenged with Eimeria tenella

Chicken coccidiosis, caused by Eimeria protozoa, affects poultry farming. Toll-like receptors (TLRs) and host defence peptides (HDPs) help host innate immune responses to eliminate invading pathogens, but their roles in Eimeria tenella infection remain poorly understood. Herein, 14-day-old chickens were treated orally with 50,000 E. tenella oocysts and the cecum was dissected at different timepoints. mRNA expression of 10 chicken TLRs (chTLRs) and five HDPs was measured by quantitative real-time PCR. chTLR7 and chTLR15 were upregulated significantly at 3 h post-infection while other chTLRs were downregulated (p < .05). chTLR1a, chTLR1b, chTLR2b and chTLR4 peaked at 36 h post-infection, chTLR3, chTLR5 and chTLR15 peaked at 72 h post-infection and chTLR21 expression was highest among chTLRs, peaking at 48 h post-infection (p < 0.05). For HDPs, cathelicidin (CATH) 1 to 3 and B1 peaked at 48 h post-infection, liver-expressed antimicrobial peptide 2 peaked at 96 h post-infection, and CATH 2 expression was highest among HDPs. CATH2 and CATH3 were markedly upregulated at 3 h post-infection (p < .05). The results provide insight into innate immune molecules during E. tenella infection in chicken, and indicate that innate immune responses may mediate resistance to chicken coccidiosis.

Quercetin Ameliorates Lipopolysaccharide-Induced Duodenal Inflammation through Modulating Autophagy, Programmed Cell Death and Intestinal Mucosal Barrier Function in Chicken Embryos

Diarrhea has been a global health problem for centuries, and the treatment has become increasingly difficult duo to the antibiotics overuse and resistance. Quercetin is a common flavonoid of extracts of vegetables, fruits, and traditional Chinese herbs, however, the mechanism of quercetin alleviating LPS-induced duodenal inflammation remains elusive. Specific pathogen-free chicken embryos (n = 120) were allocated to groups including control, PBS with or without alcohol, LPS (125 ng/egg) with or without quercetin (10, 20, or 40 nmol/egg, respectively), and quercetin groups (10, 20, or 40 nmol/egg). Fifteen day-old embryonated eggs were inoculated with abovementioned solutions via the allantoic cavity. At embryonic day 19, the duodena of the embryos were collected for histopathological examination, RNA extraction and real-time polymerase chain reaction, immunohistochemical investigations, and Western blotting. The results demonstrated quercetin enhanced the inflammatory cell infiltration in the Peyer's patch of the intestinal mucosa after LPS induction. The LPS-induced expressions of these inflammation-related factors (TLR4, IL-1β, MMP3, MMP9, NFKB1, IFNγ, IL-8, IL-6) were completely blocked by quercetin. Quercetin also decreased the protein expression of TLR4, IL-1β, MMP3, and MMP9 after LPS induction. Quercetin could down-regulate autophagy gene expression (ATG5, LC3-1, LC3-2, and LKB1), and decreased the protein expression of ATG5, and LC3-1/LC3-2 after LPS induction. Quercetin treatment prevented LPS-induced increases of the gene expressions of programmed cell death factors (TNFα, Fas, CASP1, CASP3, CASP12, Drp1, and RIPK1); meanwhile, quercetin decreased the protein expression of CASP1 and CASP3 after LPS challenge. LPS reduced the gene expression of mucin 2, but upregulated the mRNA and protein expression of claudin 1, occludin, and ZO-1, and this was balanced by quercetin. This evidence suggests that quercetin can alleviate duodenal inflammation induced by LPS through modulating autophagy, programmed cell death, intestinal barrier function.

Salmonella infection may alter the expression of toll like receptor 4 and immune related cells in chicken bursa of Fabricius

Toll like receptor 4 (TLR4), eosinophils and mast cells play significant role in host immunity during several pathogenic infections. However in vivo tissue expression of TLR4 and distribution pattern of eosinophils and mast cells in chicken bursa of Fabricius (BF) during Salmonella enterica serovar Typhimurium (STm) infection is poorly studied. Therefore, herein, following immunostaining, we found localization of TLR4 in follicular cortex and medulla and its expression was statistical increased after 36 h and 72 h of STm stimulation. Chromotrope 2R staining revealed that eosinophils were mostly distributed in follicular cortex, inter-follicular spaces and in or around blood vessels and their number in BF were statistical increased after 72 h of STm stimulation. The presence of eosinophils was confirmed using immunostaining with anti-rabbit eosinophil cationic protein antibody. Toluidine blue stained mast cells were mostly distributed in connective tissues between inter-follicular spaces while some were also present in follicular cortex of BF. However, STm stimulation illustrated non-significant effect on the number of mast cells or their de-granulation, instead their number were gradually decreased in BF with advancement in age of chickens. Hence, this study provided novel information about in vivo tissue distribution of TLR4, eosinophils and mast cells in BF during STm infection.

Immunomodulatory effects of phytogenics in chickens and pigs - A review

Environmental stressors like pathogens and toxins may depress the animal immune system through invasion of the gastrointestinal tract (GIT) tract, where they may impair performance and production, as well as lead to increased mortality rates. Therefore, protection of the GIT tract and improving animal health are top priorities in animal production. Being natural-sourced materials, phytochemicals are potential feed additives possessing multiple functions, including: anti-inflammatory, anti-fungal, anti-viral and antioxidative properties. This paper focuses on immunity-related physiological parameters regulated by phytochemicals, such as carvacrol, cinnamaldehyde, curcumin, and thymol; many studies have proven that these phytochemicals can improve animal performance and production. On the molecular level, the impact of inflammatory gene expression on underlying mechanisms was also examined, as were the effects of environmental stimuli and phytochemicals in initiating nuclear factor kappa B and mitogen-activated protein kinases signaling pathways and improving health conditions.

Genetic differences in ChTLR15 gene polymorphism and expression involved in Salmonella enterica natural and artificial infection respectively, of Chinese native chicken breeds, with a focus on sexual dimorphism

Chicken Toll-like receptor 15 (ChTLR15) has been shown to participate in immune activation in response to various pathogens and in the innate defence against infection. Two genetically distinct Chinese breeds of chicken (Qinyuan Partridge and Baier breeds) were used to study the correlation between ChTLR15 single nucleotide polymorphisms and the natural infection status of salmonella in hens, and also to examine genetic and sex-specific effects on ChTLR15 mRNA expression in heterophils and spleen during acute infection with Salmonella enterica serovar Enteritidis (SE) from 1 to 10 days after experimental infection. Three single-nucleotide polymorphisms (G168A, C726T and A1166G) in a single exon of ChTLR15 were identified in the two breeds, but only C726T showed a significant association with salmonella infection. Compared with layer-type Baier chicks, meat-type Qingyuan chicks showed a higher tolerance for capture stress and (SE) infection, as measured, respectively, by the modified body weight of chicks in the control group and in the infection group. Meanwhile, ChTLR15 down-regulation in heterophils and up-regulation in spleen were involved in the response to pathogenic SE colonization during the acute infection period. These significant genetic effects in females led to greater differences in both innate and adaptive immune responses than those exhibited in males. These results suggest that genetics, time and gender play important roles in the modulation of ChTLR15 mRNA level elicited by the SE-mediated immune response differentially in the two genetically distinct breeds, with a focus on sexual dimorphism.

Inductive expression of the NOD1 signalling pathway in chickens infected with Salmonella pullorum

1. The aim of this study was to describe the role of Nucleotide-binding oligomerization domain-containing protein 1 (NOD1) receptor signalling in chicken. 2. Tissue-specific expression analysis of NOD1, receptor-interacting serine-threonine kinase 2 (RIPK2), nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase 11 (MAPK11 or p38) by quantitative real-time PCR (qRT-PCR) revealed their wide distribution in various organs and tissues. 3. Salmonella pullorum infection activated NOD1 receptor signalling in vivo and in vitro, resulting in significant induction of downstream signalling molecules RIPK2, NF-κB/p65, MAPK11/p38 and the effector molecules IL-1b and IL-8. 4. Activation of NOD1 by its agonist bacterial γ-D-glutamyl-meso-diaminopimelic acid (iE-DAP) in HD11 cells induced the adapter molecular RIPK2 and activated the NF-κB/p65 and MAPK11/p38 pathways, resulting in an increase in IL-8 but not IL-1β. Additionally, inhibition of NOD1 using NOD1-shRNA resulted in downregulation of RIPK2, MAPK11 and IL-8, while NF-κB/p65 and IL-1β were unaltered. 5. These results highlight the important role of NOD1 receptors in eliciting the innate immune response following pathogenic invasion in chicken.

RNA-seq Profiles of Immune Related Genes in the Spleen of Necrotic Enteritis-afflicted Chicken Lines

The study aimed to compare the necrotic enteritis (NE)-induced transcriptome differences between the spleens of Marek’s disease resistant chicken line 6.3 and susceptible line 7.2 co-infected with Eimeria maxima/Clostridium perfringens using RNA-Seq. Total RNA from the spleens of two chicken lines were used to make libraries, generating 42,736,296 and 42,617,720 usable reads, which were assembled into groups of 29,897 and 29,833 mRNA genes, respectively. The transcriptome changes were investigated using the differentially expressed genes (DEGs) package, which indicated 3,255, 2,468 and 2,234 DEGs of line 6.3, line 7.2, and comparison between two lines, respectively (fold change ≥2, p<0.01). The transcription levels of 14 genes identified were further examined using qRT-PCR. The results of qRT-PCR were consistent with the RNA-seq data. All of the DEGs were analysed using gene ontology terms, the Kyoto Encyclopedia of Genes and Genomes (KEGG) database and the DEGs in each term were found to be more highly expressed in line 6.3 than in line 7.2. RNA-seq analysis indicated 139 immune related genes, 44 CD molecular genes and 150 cytokines genes which were differentially expressed among chicken lines 6.3 and 7.2 (fold change ≥2, p<0.01). Novel mRNA analysis indicated 15,518 novel genes, for which the expression was shown to be higher in line 6.3 than in line 7.2 including some immune-related targets. These findings will help to understand host-pathogen interaction in the spleen and elucidate the mechanism of host genetic control of NE, and provide basis for future studies that can lead to the development of marker-based selection of highly disease-resistant chickens.