Innate antiviral immune response against infectious bronchitis virus and involvement of prostaglandin E2 in the uterine mucosa of laying hens

A Cyclic Peptide Based on Pheasant Cathelicidin Inhibits Influenza A H1N1 Virus Infection

Influenza viruses are the leading cause of upper respiratory tract infections, leading to several global pandemics and threats to public health. Due to the continuous mutation of influenza A viruses, there is a constant need for the development of novel antiviral therapeutics. Recently, natural antimicrobial peptides have provided an opportunity for the discovery of anti-influenza molecules. Here, we designed several peptides based on pheasant cathelicidin and tested their antiviral activities and mechanisms against the H1N1 virus. Of note, the designed peptides Pc-4 and Pc-5 were found to inhibit replication of the H1N1 virus with an IC50 = 8.14 ± 3.94 µM and 2.47 ± 1.95 µM, respectively. In addition, the cyclic peptide Pc-5 was found to induce type I interferons and the expression of interferon-induced genes. An animal study showed that the cyclic peptide Pc-5 effectively inhibited H1N1 virus infection in a mouse model. Taken together, our work reveals a strategy for designing cyclic peptides and provides novel molecules with therapeutic potential against influenza A virus infection.

Fermented calcium butyrate supplementation in post-peak laying hens improved ovarian function and tibia quality through the "gut-bone" axis

The compromised egg quality and leg abnormality during the end of the laying cycle (after 40 weeks) have been leading to poor animal welfare and substantial economic losses. Therefore, the effects of fermented calcium (Ca) butyrate, produced by fermentation by Clostridium butyricum, on production, eggshell quality, and tibial property of hens were explored. A total of 192 Hy-line brown laying hens at 50-week-old were assigned to a basal diet or the basal diet with 300 mg/kg of the fermented Ca butyrate from 50 to 58 weeks of age. Each treatment had 6 replicates with 16 hens each. The diet supplemented with 300 mg/kg fermented Ca butyrate notably increased egg weight, ovarian follicle number, and eggshell strength (P = 0.072) as compared to the basal diet, which were associated with cytokine secretion, toll-like receptor signaling pathways, and intestinal immunity based on the RNA-seq data from the granulosa. Dietary Ca butyrate inclusion decreased the expression of ileal tumor necrosis factor-alpha and serum pro-inflammatory cytokine concentration, as well as increased the content of serum immunoglobulin A when compared to the basal diet (both P < 0.05). The birds that received fermented Ca butyrate diets exhibited higher villus height (P < 0.05) and upregulated expression of tight junction proteins, whereas it did not alter the composition of cecal microbiota (P > 0.05). In addition, the diet with fermented Ca butyrate reduced the number of osteoclasts in the proximal tibia and the level of C-terminal cross-linked telopeptide of type I collagen, a bone resorption marker (P < 0.05), whereas it tended to increase the concentration of the procollagen type I N-terminal propeptide that reflects bone formation marker in serum. Moreover, the layers fed fermented Ca butyrate diets possessed higher (P < 0.05) bone area and trabecular number of the proximal tibia, yield load, and ultimate load than those that consumed basal diets. Collectively, dietary fermented Ca butyrate supplementation in post-peak layer diets improved the ovarian function and tibia quality, which might be related to enhancing intestinal integrity and consequently decreasing inflammation mediated bone resorption.

Cyclooxygenase-2/prostaglandin E2 pathway regulates infectious bronchitis virus replication in avian macrophages

Infectious bronchitis virus (IBV) is a significant respiratory pathogen that affects chickens worldwide. As an avian coronavirus, IBV leads to productive infection in chicken macrophages. However, the effects of IBV infection in macrophages on cyclooxygenase-2 (COX-2) expression are still to be elucidated. Therefore, we investigated the role of IBV infection on the production of COX-2, an enzyme involved in the synthesis of prostaglandin E2 (PGE2) in chicken macrophages. The chicken macrophage cells were infected with two IBV strains, and the cells and culture supernatants were harvested at predetermined time points to measure intracellular and extracellular IBV infection. IBV infection was quantified as has been the COX-2 and PGE2 productions. We found that IBV infection enhances COX-2 production at both mRNA and protein levels in chicken macrophages. When a selective COX-2 antagonist was used to reduce the COX-2 expression in macrophages, we observed that IBV replication decreased. When IBV-infected macrophages were treated with PGE2 receptor (EP2 and EP4) inhibitors, IBV replication was reduced. Upon utilizing a selective COX-2 antagonist to diminish PGE2 expression in macrophages, a discernible decrease in IBV replication was observed. Treatment of IBV-infected macrophages with a PGE2 receptor (EP2) inhibitor resulted in a reduction in IBV replication, whereas the introduction of exogenous PGE2 heightened viral replication. Additionally, pretreatment with a Janus-kinase two antagonist attenuated the inhibitory effect of recombinant chicken interferon (IFN)-γ on viral replication. The evaluation of immune mediators, such as inducible nitric oxide (NO) synthase (iNOS), NO, and interleukin (IL)-6, revealed enhanced expression following IBV infection of macrophages. In response to the inhibition of COX-2 and PGE2 receptors, we observed a reduction in the expressions of iNOS and IL-6 in macrophages, correlating with reduced IBV infection. Overall, IBV infection increased COX-2 and PGE2 production in addition to iNOS, NO, and IL-6 expression in chicken macrophages in a time-dependent manner. Inhibition of the COX-2/PGE2 pathway may lead to increased macrophage defence mechanisms against IBV infection, resulting in a reduction in viral replication and iNOS and IL-6 expressions. Understanding the molecular mechanisms underlying these processes may shed light on potential antiviral targets for controlling IBV infection.

Transcriptome and histological analyses on the uterus of freckle egg laying hens

BACKGROUND

In this study, we explored the characteristics and causes of freckle formation. We collected 15 normal and freckled eggs each for eggshell index testing and hypothesized that the structure and function of the uterus would have a direct effect on freckled egg production given that eggshells are formed in the uterus. To test this hypothesis, we collected uterine tissue from laying hens (418 days of age) that laid normal (Group C, n = 13) and freckled (Group T, n = 16) eggs for 7 consecutive days.

RESULTS

When we examined the eggshell quality, we found that the L value was significantly lower (P < 0.05) in the freckled site group of freckled eggs compared to the normal egg group during the detection of blunt pole, equator, and sharp pole of the eggshell color. The a-values of the three positions were significantly higher (P < 0.05) in the freckled site group of freckled eggs, and the a-values of the blunt pole were significantly lower (P < 0.05) in the background site group of freckled eggs, compared to the normal egg group. The b-values were significantly higher (P < 0.05) at three locations in the freckled site group of freckled eggs compared to the normal egg group. During the detection of eggshell thickness, the blunt pole was significantly higher (P < 0.05) in the freckled egg site group of freckled eggs compared to the normal egg group, and there was no significant difference between the other groups (P > 0.05). There was no significant difference (P > 0.05) between the transverse and longitudinal diameters of the eggs in each group.We then performed histopathology and transcriptome analyses on the collected tissue. When compared with group C, uterine junctional epithelial cells in group T showed significant defects and cilia loss, and epithelial tissue was poorly intact. From transcriptomics, genes that met (|log2FC|) ≥ 1 and P < 0.05 criteria were screened as differentially expressed genes (DEGs). We identified a total of 136 DEGs, with 101 up- and 35 down-regulated genes from our RNA-seq data. DEGs identified by enrichment analyses, which were potentially associated with freckled egg production were: IFI6, CCL19, AvBD10, AvBD11, S100A12, POMC, and UCN3. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses showed that pathways were associated with immunoreaction and stress stimulation, e.g., complement activation, interleukin-1 cell reactions, viral responses, cell reactions stimulated by corticotropin releasing hormone, steroid hormone mediated signaling pathways, staphylococcal infections, B cell receptor signaling pathways, and natural killer cell mediated cytotoxicity.

CONCLUSIONS

From these data, freckled areas deepen freckled eggshell color, but background areas are not affected. At the same time,we reasoned that freckle eggs may result from abnormal immune responses and impaired uterine functions induced by stress. Therefore, the uterus of laying hens in a state of stress and abnormal immune function can cause the appearance of freckled eggs.

Aging-associated increased nitric oxide production is a potential cause of inferior eggshell quality produced by aged laying hens

It is important to prolong the productive life of laying hens without compromising their welfare. Therefore, in this study, we aimed to identify the cause for inferior quality egg production of aged hens by investigating the aging-associated molecular changes related to eggshell formation in the isthmic and uterine mucosae and determining whether nitric oxide plays a role in decreasing the quality of eggs produced by aged hens. Young (35 weeks old) and aged (130 weeks old) White Leghorn laying hens were used in this study to determine the effects of age on the expression of proteins related to eggshell membranes formation in the isthmus and eggshell biomineralization and nitric oxide production in the uterus. Nitric oxide synthesis during the ovulatory cycle was examined in twenty-five laying hens (46-52 weeks old) euthanized at 0, 4, 7, 16, and 24 h after oviposition. S-Nitroso-N-acetylpenicillamine (a nitric oxide donor) was added to the cultured isthmic and uterine mucosal cells to examine the effects of nitric oxide on the expression of genes related to eggshell membranes formation and eggshell biomineralization, respectively. The results showed that the protein abundance of collagen I and V in the isthmic mucosa and collagen V in the eggshell membranes were lower in aged hens than in young hens. The mRNA expression levels of calbindin, osteopontin, and ovocalyxin-36 and the protein abundance of calbindin and carbonic anhydrase-2 were lower in the uterine mucosa of aged hens than in that of young hens. Nitric oxide synthesis was higher in the uterine mucosa of aged hens than in that of young hens. Nitric oxide downregulated the mRNA expression levels of osteopontin and ovocalyxin-36 in cultured uterine mucosal cells. Our results indicated that the eggshell quality decreases with aging due to molecular changes in the uterine mucosa affecting the eggshell membrane formation and eggshell biomineralization. Moreover, nitric oxide overproduction may play a role in this dysfunction.

Modulation of the innate immune system by lipopolysaccharide in the proventriculus of chicks inoculated with or without Newcastle disease and infectious bronchitis vaccine

This study aimed to determine whether the innate immune system in the proventriculus of broiler chicks responds to lipopolysaccharide (LPS) and whether this response is affected by Newcastle disease and infectious bronchitis (ND/IB) vaccination. Chicks were divided into 4 groups: nonvaccinated and injected with PBS or LPS (V-L- and V-L+), and vaccinated and injected with PBS or LPS (V+L- and V+L+). Vaccination was performed on d 1, and LPS was intraperitoneally injected on d 11 of age. The gene expression and protein levels of immune molecules, including toll-like receptors (TLRs), antimicrobial peptides, interleukin-1β (IL-1B), and immunoglobulin A (IgA) in the proventriculus and serum were analyzed. The results showed that the expression levels of TLR21 were higher in vaccinated (V+L-) group than in nonvaccinated (V-L-) group. Gene expression levels of avian β-defensin (AvBDs) and cathelicidin1 (Cath1) were not different among the 4 groups. However, the results of LC/MS analysis showed that the levels of AvBD2, 6, and 7 significantly increased after the LPS challenge in nonvaccinated and vaccinated chicks; the levels were higher in V-L+ and V+L+ than in V-L- and V+L-, respectively. Immunohistochemistry analysis revealed the localization of AvBD1 protein in the epithelial cells of the surface glands and AvBD2 and CATH1 in the heterophil-like cells in the lamina propria of surface glands. Although IL-1B gene expression and protein concentration in the proventriculus tissues were not different among the 4 groups, serum IL-1B levels were upregulated by LPS in both the nonvaccinated and vaccinated groups (V-L- vs. V-L+, V+L- vs. V+L+). Moreover, IgA levels in the proventriculus and serum were not affected by vaccination or LPS challenge. Taken together, we conclude that LPS derived from gram-negative bacteria upregulates the innate immune system, including antimicrobial peptide synthesis in the proventriculus. ND/IB vaccination may not significantly affect antimicrobial peptide synthesis in response to LPS; however, TLR21 expression is upregulated by that vaccination. The antimicrobial peptides synthesized in the proventriculus probably prevent pathogenic microbes from entering the intestine.

Towards Improved Use of Vaccination in the Control of Infectious Bronchitis and Newcastle Disease in Poultry: Understanding the Immunological Mechanisms

Infectious bronchitis (IB) and Newcastle disease (ND) are two important diseases of poultry and have remained a threat to the development of the poultry industry in many parts of the world. The immunology of avian has been well studied and numerous vaccines have been developed against the two viruses. Most of these vaccines are either inactivated vaccines or live attenuated vaccines. Inactivated vaccines induce weak cellular immune responses and require priming with live or other types of vaccines. Advanced technology has been used to produce several types of vaccines that can initiate prime immune responses. However, as a result of rapid genetic variations, the control of these two viral infections through vaccination has remained a challenge. Using various strategies such as combination of live attenuated and inactivated vaccines, development of IB/ND vaccines, use of DNA vaccines and transgenic plant vaccines, the problem is being surmounted. It is hoped that with increasing understanding of the immunological mechanisms in birds that are used in fighting these viruses, a more successful control of the diseases will be achieved. This will go a long way in contributing to global food security and the economic development of many developing countries, given the role of poultry in the attainment of these goals.

Age-related modulation of the isthmic and uterine mucosal innate immune defense system in laying hens

Sustained production of good quality eggs for longer production cycles is a challenge for poultry farms. The impact of aging on the mucosal immune defense in the isthmus and uterus of hens, where the eggshell membrane and eggshell are formed, remains obscure. Thus, the aim of this study was to determine whether aging affects the mucosal tight junction (TJ) proteins, the synthesis of antimicrobial peptides including avian β-defensins (AvBDs) and cathelicidins (CATHs), and Toll-like receptors (TLRs) in the isthmus and uterus of laying hens. Young and aged White Leghorn laying hens (35 and 130 wk old, respectively) were used. Total RNA and protein contents were isolated from the isthmic and uterine mucosae of these hens to examine the expression of TJ proteins, AvBD, and CATH genes and AvBD proteins by the real-time polymerase chain reaction and western blotting. The results showed that the mRNA expression of TJ proteins, namely zonula occludin 2 in the isthmus and occludin in the uterus, was higher in aged hens than in young hens. Expression of 2 AvBD genes in the isthmus and 4 AvBD genes in the uterus was higher in aged hens than in young hens. However, the expression of AvBD proteins 1 and 11 was not altered by aging. Expressions of CATH genes were not affected by aging in the isthmus or uterus. Expression of TLR genes was higher in aged hens than in young hens in the isthmus, while their expression in the uterus was not affected by aging. It can be concluded that aged hens have a higher potential ability to express TJ proteins and AvBDs for mucosal defense in the isthmic and uterine mucosae than in young hens.

Expression of pro- and anti-inflammatory cytokines and chemokines during the ovulatory cycle and effects of aging on their expression in the uterine mucosa of laying hens

The aim of this study was to examine whether cytokines and chemokines expressed in the uterine mucosa play a role in the process of eggshell formation in the chicken uterus. Changes in the expression levels of pro- and anti-inflammatory cytokines and chemokines in the uterine mucosa during an ovulatory cycle (experiment 1) and effects of aging on their expression (experiment 2) were examined. In experiment 1, the expression of the pro-inflammatory cytokines IL1β, IL6, TNFSF15, and IFNγ, and a chemokine CX3CL1 was found to increase during eggshell biomineralization (16 h following oviposition), while anti-inflammatory TGFβ2 expression was found to increase at 4 h following oviposition. In experiment 2, a higher expression of the anti-inflammatory cytokines TGFβ2 and TGFβ3, and chemokines CXCLi2 and CX3CL1, was observed in aged hens than in young hens. A significantly higher number of macrophages and CD8+ T cells were observed in the uterine tissue of aged hens than in young hens. Furthermore, the expression of adhesion molecules associated with leukocytic infiltration was found to be higher in aged hens than in young hens. We conclude that the eggshell formation process may be affected by the pro- and anti-inflammatory cytokines and chemokines. The balanced expressions of these molecules might be disrupted in aged hens.