The effect of ghrelin on bursa and cecal tonsils of chickens infected with an attenuated virus strain of infectious bursal disease virus

Infectious bursal disease (IBD) significantly affects the poultry industry, causing substantial economic losses. This study aimed to investigate the effects of ghrelin on chicks infected with an attenuated virus strain of IBDV (aIBDV). Chicks were divided into 3 groups: a control group (group I), an aIBDV infection group (group II), and a ghrelin + aIBDV infection group (group III). Mice in groups II and III were fed until they reached 19 d of age and then inoculated with aIBDV to establish a subclinical infection model. Group III received an intraperitoneal injection of 0.5 nmol/100 g ghrelin from d 17 to 23. The present study utilized paraffin sectioning, H&E staining, and immunohistochemical staining to examine the effects of ghrelin on the bursa of fabricius and cecum tonsils in aIBDV-infected chicks. The results indicated that at 3 d postinfection (dpi), the average body weight of group III was significantly greater than that of group II (P < 0.05). At 3 and 7 dpi, the proportion of large lymphoid follicles in the bursa of fabricius in group III was notably greater than that in group II (P < 0.05). aIBDV infection resulted in bleeding, edema, and fibrosis in the cecal mucosal layer of chicks, but ghrelin administration mitigated these pathological changes. At 3 and 7 dpi, the thickness of the lamina propria in the cecal tonsils of group III was significantly lower than that in the cecal tonsils of group II (P < 0.05). Additionally, the percentage of large lymphoid follicles in the cecal tonsils of group III was significantly greater than that in group II at 3 and 5 dpi (P < 0.05). There were significantly fewer macrophages in the cecal tonsils of group III than in those of group II at 1, 3, and 5 dpi (P < 0.05). In conclusion, ghrelin supplementation improved performance and mitigated bursal atrophy in aIBDV-infected chicks. It also reduced histological lesions and immune responses in the cecum tonsil. Notably, the reduction in macrophages in the cecum tonsil following ghrelin administration may decrease the risk of aIBDV spread.

Gene expression response to Salmonella Typhimurium in the cecal tonsil reveals a potential mechanism of resistance in chickens

Salmonella has been one of the most important factors restricting the development of the poultry industry and also poses great threat to public health. To get insight into molecular alterations that occur during bacterial infection, we sequenced the cecal tonsil transcriptome in 2 chicken breeds (Beijing-You and Cobb) known to have differing resistance to Salmonella. The 28-day-old chickens were orally challenged by 1.83 × 1011 CFU Salmonella Typhimurium, and the cecal tonsil transcriptome was sequenced 3 d postinfection. Analysis identified 201 and 170 differentially expressed genes response to Salmonella in 2 chicken breeds, respectively. They were involved in the Toll-like receptor signaling pathway and activated the production of pro-inflammatory cytokines and chemokines. The protein-protein interaction (PPI) network suggested MMP9 as a crucial protein that may be involved in extracellular matrix breakdown and leukocyte migration in the resistant breed (Beijing-You). Meanwhile, in susceptible chickens (Cobb), ACOD1 was the key gene in the PPI network and might promote the expression of genes related to oxidative stress response and gastrointestinal tract function. These findings provide insight into the differing resistance of these 2 chicken breeds.

The Acute Host-Response of Turkeys Colonized With Campylobacter coli

Consumption of contaminated poultry products is one of the main sources of human campylobacteriosis, of which Campylobacter jejuni subsp. jejuni (C. jejuni) and C. coli are responsible for ~98% of the cases. In turkeys, the ceca are an important anatomical site where Campylobacter asymptomatically colonizes. We previously demonstrated that commercial turkey poults colonized by C. jejuni showed acute changes in cytokine gene expression profiles, and histological intestinal lesions at 2 days post-inoculation (dpi). Cecal tonsils (CT) are an important part of the gastrointestinal-associated lymphoid tissue that surveil material passing in and out of the ceca, and generate immune responses against intestinal pathogens. The CT immune response toward Campylobacter remains unknown. In this study, we generated a kanamycin-resistant C. coli construct (CcK) to facilitate its enumeration from cecal contents after experimental challenge. In vitro analysis of CcK demonstrated no changes in motility when compared to the parent isolate. Poults were inoculated by oral gavage with CcK (5 × 107 colony forming units) or sterile-media (mock-colonized), and euthanized at 1 and 3 dpi. At both time points, CcK was recovered from cecal contents, but not from the mock-colonized group. As a marker of acute inflammation, serum alpha-1 acid glycoprotein was significantly elevated at 3 dpi in CcK inoculated poults compared to mock-infected samples. Significant histological lesions were detected in cecal and CT tissues of CcK colonized poults at 1 and 3 dpi, respectively. RNAseq analysis identified 250 differentially expressed genes (DEG) in CT from CcK colonized poults at 3 dpi, of which 194 were upregulated and 56 were downregulated. From the DEG, 9 significantly enriched biological pathways were identified, including platelet aggregation, response to oxidative stress and negative regulation of oxidative stress-induced intrinsic apoptotic signaling pathway. These data suggest that C. coli induced an acute inflammatory response in the intestinal tract of poults, and that platelet aggregation and oxidative stress in the CT may affect the turkey's ability to resist Campylobacter colonization. These findings will help to develop and test Campylobacter mitigation strategies to promote food safety in commercial turkeys.

Probiotic Lactobacilli Limit Avian Influenza Virus Subtype H9N2 Replication in Chicken Cecal Tonsil Mononuclear Cells

Low pathogenic avian influenza virus (LPAIV) H9N2 poses significant threat to animal and human health. The growing interest in beneficial effects of probiotic bacteria on host immune system has led to research efforts studying their interaction with cells of host immune system. However, the role of lactobacilli in inducing antiviral responses in lymphoid tissue cells requires further investigation. The objective of the present study was to examine the antiviral and immunostimulatory effects of lactobacilli bacteria on chicken cecal tonsils (CT) cells against H9N2 LPAIV. CT mononuclear cells were stimulated with probiotic Lactobacillus spp mixture either alone or in combination with a Toll-like receptor (TLR)21 ligand, CpG oligodeoxynucleotides (CpG). Pre-treatment of CT cells with probiotic lactobacilli, alone or in combination with CpG, significantly reduced H9N2 LPAIV replication. Furthermore, lactobacilli alone elicited cytokine expression, including IL-2, IFN-γ, IL-1β, IL-6, and IL-12, and IL-10, while when combined with CpG, a significantly higher expression of (interferon-stimulated gene (viperin)), IL-12, IL-6, CXCLi2, and IL-1β was observed. However, none of these treatments induced significant changes in nitric oxide production by CT cells. In conclusion, probiotic lactobacilli demonstrated a modulatory effect on CT cells, and this correlated with enhanced antiviral immunity and reduced H9N2 LPAIV viral replication.

Genotype-dependent development of cellular and humoral immunity in the spleen and cecal tonsils of chickens stimulated in ovo with bioactive compounds

Prebiotics, probiotics, and synbiotics, delivered in ovo influence the colonization and development of the peripheral immune system in poultry. This study aimed to investigate the influence of the host genotype (broiler chickens [Ross 308] and old native Polish breed Green-legged Partridgelike [GP] chickens) on the number of B and T cells in the spleen and cecal tonsils (CT). The solution of a bioactive compound was injected in ovo on day 12 of egg incubation: prebiotics (galactooligosaccharides [GOS]), probiotics (Lactococcus lactis subsp. cremoris IBB477), and synbiotics (GOS + L. lactis). The samples were collected on day 7, day 21, and day 42 after hatching (n = 8). The number of Bu-1⁺ (B) cells, CD4⁺ cells, and CD8⁺ cells in the spleen and CT was estimated using immunohistochemistry. The number of germinal centers (GC) was determined in the spleen. In broilers, probiotics increased (P < 0.05) the number of CD4⁺ cells in the CT on day 7. On day 21, prebiotics raised (P < 0.01) the number of cells involved in cellular immunity in the CT (CD4⁺ and CD8⁺ cells) and spleen (CD8⁺ cells). On day 42, it was synbiotics that stimulated the colonization of both the CT and spleen by B cells, but colonization of the spleen only by CD4⁺ and CD8⁺ cells. In GP chickens, synbiotics enforced the cellular immunity (CD4⁺ or CD8⁺ cells) in the spleen at all time points. Synbiotics also stimulated the GC appearance on day 21 and day 42. In GP chickens, the influence of bioactive compounds on colonization of the CT was very limited. In broilers, we determined pronounced and age-dependent effects of prebiotics and synbiotics on the number of B and T cells in both the CT and spleen. In GP chickens, the most potent compound was synbiotics, which stimulated cellular immunity in the spleen but not in the CT. However, given the long-term effects on adaptive immune cells, synbiotics were the most potent compounds in both chicken genotypes.

Transcriptome Analysis of the Cecal Tonsil of Jingxing Yellow Chickens Revealed the Mechanism of Differential Resistance to Salmonella

Salmonella is one of the most common food-borne pathogens. It can be transmitted between chickens, as well as to people by contaminated poultry products. In our study, we distinguished chickens with different resistances mainly based on bacterial loads. We compared the cecal tonsil transcriptomes between the susceptible and resistant chickens after Salmonella infection, aiming to identify the crucial genes participating in the antibacterial activity in the cecal tonsil. A total of 3214 differentially expressed genes (DEGs), including 2092 upregulated and 1122 downregulated genes, were identified between the two groups (fold change ≥ 2.0, padj < 0.05). Many DEGs were mainly involved in the regulation of two biological processes: crosstalk between the cecal tonsil epithelium and pathogenic bacteria, such as focal adhesion, extracellular-matrix-receptor interaction, and regulation of the actin cytoskeleton and host immune response including the cytokine-receptor interaction. In particular, the challenged resistant birds exhibited strong activation of the intestinal immune network for IgA production, which perhaps contributed to the resistance to Salmonella infection. These findings give insight into the mRNA profile of the cecal tonsil between the two groups after initial Salmonella stimulation, which may extend the known complexity of molecular mechanisms in chicken immune response to Salmonella.

Sodium selenite prevents suppression of mucosal humoral response by AFB1 in broiler's cecal tonsil

Aflatoxin B₁ (AFB₁), the most common mycotoxin in human food and animal feed, produces hepatotoxic, genotoxic and immunosuppressive effects in multiple species. Selenium (Se) has emerged as an important element in the dietary prevention of various toxic agents. The present study was designed to scrutinize the protective effects of sodium selenite on the histological lesions and suppression of mucosal humoral response in the cecal tonsil generated by AFB₁. A total of 156 one-day-old broilers were divided into four groups and fed on basal diet (control group), 0.6 mg/kg AFB₁ (AFB₁ group), 0.4 mg/kg Se supplement (+Se group), and 0.6 mg/kg AFB₁ + 0.4 mg/kg Se supplement (AFB₁+Se group) respectively for 21 days. Our results showed that 0.4 mg/kg Se supplement in broiler's diets could improve the AFB₁-induced histological lesions in the cecal tonsils including the depletion of lymphocytes in the lymphatic nodules as well as the shedding of microvilli in the absorptive cells. Moreover, Se could restore the decreased number of IgA+ cells and expression levels of pIgR, IgA, IgG, and IgM mRNA induced by AFB₁ to be close to those in the control group. These results demonstrated that 0.4 mg/kg supplemented dietary Se in the form of sodium selenite could protect the cecal tonsils from the histological lesions and suppression of the mucosal humoral response provoked by 0.6 mg/kg AFB₁. Our study may provide new experimental evidences for better understanding of AFB₁-induced damage of mucosal immunity and protective effect of Se against this toxin.

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

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

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

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

Chinese goose (Anser cygnoides) CD8a: cloning, tissue distribution and immunobiological in splenic mononuclear cells

CD8 molecule is a cell membrane glycoprotein, which plays an important role in cell-mediated immunity. Here, we identified Chinese goose CD8α (goCD8α) gene for the first time. The full-length cDNA of goCD8α is 1459bp in length and contains a 711bp open reading frame. Phylogenetic analysis shows that the waterfowl CD8α formed a monophyletic group. Semi-quantitative RT-PCR analysis showed that transcripts of goCD8α mRNA were high in the immune-related organs and mucosal immune system in gosling, and high in thymus and spleen comparing to other immune-related tissues in goose. The obvious increase of CD8α expression was observed in spleen of acute new type gosling viral enteritis virus (NGVEV) infected bird, while the increase of CD8α were observed in the thymus, bursa of fabricius, and cecum of chronic infected bird. The CD8α mRNA transcription level in spleen mononuclear cells was significantly up-regulated when stimulated by phytohemagglutinin, but not by lipopolysaccharide in vitro.