Ovotransferrin expression and release by chicken cell lines infected with Marek's disease virus

Current Findings on Gut Microbiota Mediated Immune Modulation against Viral Diseases in Chicken

Chicken gastrointestinal tract is an important site of immune cell development that not only regulates gut microbiota but also maintains extra-intestinal immunity. Recent studies have emphasized the important roles of gut microbiota in shaping immunity against viral diseases in chicken. Microbial diversity and its integrity are the key elements for deriving immunity against invading viral pathogens. Commensal bacteria provide protection against pathogens through direct competition and by the production of antibodies and activation of different cytokines to modulate innate and adaptive immune responses. There are few economically important viral diseases of chicken that perturb the intestinal microbiota diversity. Disruption of microbial homeostasis (dysbiosis) associates with a variety of pathological states, which facilitate the establishment of acute viral infections in chickens. In this review, we summarize the calibrated interactions among the microbiota mediated immune modulation through the production of different interferons (IFNs) ILs, and virus-specific IgA and IgG, and their impact on the severity of viral infections in chickens. Here, it also shows that acute viral infection diminishes commensal bacteria such as Lactobacillus, Bifidobacterium, Firmicutes, and Blautia spp. populations and enhances the colonization of pathobionts, including E. coli, Shigella, and Clostridial spp., in infected chickens.

Ovotransferrin ameliorates the dysbiosis of immunomodulatory function and intestinal microbiota induced by cyclophosphamide

In this study, the regulative effects of ovotransferrin (OVT) on immunomodulatory function and intestinal microbial dysbiosis in a mouse model injected with cyclophosphamide (CP) were investigated. The immunomodulatory effect of OVT was determined by enzyme-linked immune sorbent assay (ELISA). Gut microbial composition was determined by high-throughput sequencing of the V3-V4 region of the 16S rDNA gene. The changes in the relative abundance of the dominant microbiota were analyzed at different taxonomic levels. The results showed that OVT alleviated the immune dysfunction caused by CP. OVT improved the spleen and thymus indices and enhanced the secretion of tumor necrosis factor alpha (TNF-α), interleukin-10 (IL-10), and immunoglobulin A (IgA). In addition, OVT increased the indexes of Shannon and Simpson, suggesting the enhancement of the diversity and richness of intestinal microflora. The relative abundance of Lachnospiraceae_NK4A136_group was also increased. However, the relative abundance of Helicobacter and Desulfovibrio was significantly decreased. These results indicated that OVT, a food-derived functional component, has effects on immune regulation in the organism and ameliorates the gut microbiota disorders induced by CP, which provides a potential therapeutic utilization of avian eggs by targeting the gut microbiome.

The Golden Egg: Nutritional Value, Bioactivities, and Emerging Benefits for Human Health

Egg is an encapsulated source of macro and micronutrients that meet all requirements to support embryonic development until hatching. The perfect balance and diversity in its nutrients along with its high digestibility and its affordable price has put the egg in the spotlight as a basic food for humans. However, egg still has to face many years of nutritionist recommendations aiming at restricting egg consumption to limit cardiovascular diseases incidence. Most experimental, clinical, and epidemiologic studies concluded that there was no evidence of a correlation between dietary cholesterol brought by eggs and an increase in plasma total-cholesterol. Egg remains a food product of high nutritional quality for adults including elderly people and children and is extensively consumed worldwide. In parallel, there is compelling evidence that egg also contains many and still-unexplored bioactive compounds, which may be of high interest in preventing/curing diseases. This review will give an overview of (1) the main nutritional characteristics of chicken egg, (2) emerging data related to egg bioactive compounds, and (3) some factors affecting egg composition including a comparison of nutritional value between eggs from various domestic species.

Synergistic Viral Replication of Marek's Disease Virus and Avian Leukosis Virus Subgroup J is Responsible for the Enhanced Pathogenicity in the Superinfection of Chickens

Superinfection of Marek's disease virus (MDV) and avian leukosis virus subgroup J (ALV-J) causes lethal neoplasia and death in chickens. However, whether there is synergism between the two viruses in viral replication and pathogenicity has remained elusive. In this study, we found that the superinfection of MDV and ALV-J increased the viral replication of the two viruses in RNA and protein level, and synergistically promoted the expression of IL-10, IL-6, and TGF-β in chicken embryo fibroblasts (CEF). Moreover, MDV and ALV-J protein expression in dual-infected cells detected by confocal laser scanning microscope appeared earlier in the cytoplasm and the nucleus, and caused more severe cytopathy than single infection, suggesting that synergistically increased MDV and ALV-J viral-protein biosynthesis is responsible for the severe cytopathy. In vivo, compared to the single virus infected chickens, the mortality and tumor formation rates increased significantly in MDV and ALV-J dual-infected chickens. Viral loads of MDV and ALV-J in tissues of dual-infected chickens were significantly higher than those of single-infected chickens. Histopathology observation showed that more severe inflammation and tumor cells metastases were present in dual-infected chickens. In the present study, we concluded that synergistic viral replication of MDV and ALV-J is responsible for the enhanced pathogenicity in superinfection of chickens.

The Nutraceutical Properties of Ovotransferrin and Its Potential Utilization as a Functional Food

Ovotransferrin or conalbumin belong to the transferrin protein family and is endowed with both iron-transfer and protective activities. In addition to its well-known antibacterial properties, ovotransferrin displays other protective roles similar to those already ascertained for the homologous mammalian lactoferrin. These additional functions, in many cases not directly related to iron binding, are also displayed by the peptides derived from partial hydrolysis of ovotransferrin, suggesting a direct relationship between egg consumption and human health.

Comparison of chicken and pheasant ovotransferrin N-glycoforms via electrospray ionization mass spectrometry and liquid chromatography coupled with mass spectrometry

Species-specific ovotransferrin features a highly conservative protein sequence, but it varies in the structure of the attached oligosaccharides, which may contribute to the differences observed in its bioactivity and nutritional value. Herein, chicken ovotransferrin (COT) and pheasant ovotransferrin (POT) isolated by repeated ethanol precipitation of egg white were digested with peptide N-glycosidase F to release N-glycans. The obtained N-glyans were isotopically labeled with aniline and analyzed via electrospray ionization mass spectrometry and online hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry (HILIC-MS/MS). Relative quantitation based on isotopic aniline labeling and HILIC-MS/MS analysis revealed in detail the conspicuous difference between COT and POT in the abundance of their N-glycan compositions and isomers. In total, 16 COT N-glycans were observed, including 1 core structure (3.18%), 3 hybrid type (5.42%), and 12 complex type (91.40%), whereas 21 POT N-glycans were found, including 1 truncated structure (1.88%), 1 core structure (6.26%), 3 high mannose type (5.20%), 6 hybrid type (19.14%), and 10 complex type (67.52%). To our knowledge, this study is the first qualitative and quantitative comparison of COT and POT N-glycosylation patterns. These results suggest that POT has a different glycosylation pattern compared to that of COT and thus the effect of its glycosylation pattern on its bioactivity is worthy of further exploration.

Unraveling molecular mechanistic differences in liver metabolism between lean and fat lines of Pekin duck (Anas platyrhynchos domestica): a proteomic study

Duck is one of the major poultry meat sources for human consumption. To satisfy different eating habits, lean and fat strains of Pekin ducks have been developed. The objective of this study was to determine the molecular mechanistic differences in liver metabolism between two duck strains. The liver proteome of the Pekin duck lines was compared on days 1, 14, 28, and 42 posthatching using 2-DE based proteomics. There was a different abundance of 76 proteins in the livers of the two duck lines. Fat ducks strongly expressed proteins related to pathways of glycolysis, ATP synthesis, and protein catabolism, suggesting enhanced fat deposition rather than protein retention. In contrast, highly expressed proteins in lean ducks improved protein anabolism and reduced protein catabolism, resulting in an enhancement of lean meat deposition. Along with the decrease in fat deposition, the immune system of the lean duck strain may be enhanced by enhanced expression of proteins involved in stress response, immune defense, and antioxidant functions. These results indicate that selection pressure has shaped the two duck lines differently resulting in different liver metabolic capacities. These observed variations between the two strains at the molecular level are matched with physiological changes in growth performance and meat production. This information may have beneficial impacts in areas such as genetic modification through the manipulation of target proteins or genes in specific pathways to improve the efficiency of duck meat production.

BIOLOGICAL SIGNIFICANCE

The objective of this study was to unravel molecular mechanistic differences in liver metabolism between lean and fat Pekin duck (Anas platyrhynchos domestica) strains. There was a different abundance of 76 proteins in the livers of the two duck lines. Enhanced protein expression in the fat ducks related to pathways of glycolysis, ATP synthesis and protein catabolism suggesting increased fat deposition rather than protein retention. In contrast, highly expressed proteins in the lean ducks facilitated protein deposition by increasing protein anabolism and reducing protein catabolism to enhance the lean meat percentage. Along with the decrease of fat deposition, the immunity of lean duck appeared to be enhanced by increased expression of proteins involved in stress response, defense and antioxidant function. This study provides potential target proteins or genes for further functional analysis and genetic manipulation to increase the efficiency of duck meat production and help satisfy the global demand for poultry meat.

Effect of high pressure treatment on ovotransferrin

High pressure processing of ovotransferrin was carried out to study the structural and physiochemical changes of ovotransferrin under various pressure levels. At pH 8 and pressures higher than 200 MPa, a decrease in total sulfhydryl groups and an increase in surface hydrophobicity were observed along with a partial aggregation. A gradual shift of denaturation peak towards higher temperature was noticed up to 500 MPa, leading to a total loss of the enthalpy of denaturation at pressures of 600 and 700 MPa, where a significant decrease in intrinsic fluorescence was also observed. At pH 3, the ovotransferrin adopted a molten globule state, associated with a significant increase in surface hydrophobicity and reactive sulfhydryl content; structurally, no clear denaturation peaks in differential scanning calorimetry (DSC) were detected at any level of pressure treatment whereas a noticeable decrease in intrinsic fluorescence was evidenced up to 600 MPa and then increased at 700 MPa pressure treatment. Fourier transform infrared spectroscopy (FT-IR) revealed that the conformational structure were changed from helices, sheets, turns, and aggregated strand to mostly intermolecular β-sheets or aggregated strands at pH 8 at 200 MPa but switched back to original structure at higher pressures.

Physiological roles of ovotransferrin

BACKGROUND

Ovotransferrin is an iron-binding glycoprotein, found in avian egg white and in avian serum, belonging to the family of transferrin iron-binding glycoproteins. All transferrins show high sequence homology. In mammals are presents two different soluble glycoproteins with different functions: i) serum transferrin that is present in plasma and committed to iron transport and iron delivery to cells and ii) lactoferrin that is present in extracellular fluids and in specific granules of polymorphonuclear lymphocytes and committed to the so-called natural immunity. To the contrary, in birds, ovotransferrin remained the only soluble glycoprotein of the transferrin family present both in plasma and egg white.

SCOPE OF REVIEW

Substantial experimental evidences are summarized, illustrating the multiple physiological roles of ovotransferrin in an attempt to overcome the common belief that ovotransferrin is a protein dedicated only to iron transport and to iron withholding antibacterial activity.

MAJOR CONCLUSIONS

Similarly to the better known family member protein lactoferrin, ovotransferrin appears to be a multi-functional protein with a major role in avian natural immunity.

GENERAL SIGNIFICANCE

Biotechnological applications of ovotransferrin and ovotransferrin-related peptides could be considered in the near future, stimulating further research on this remarkable protein. This article is part of a Special Issue entitled Transferrins: Molecular mechanisms of iron transport and disorders.

Transcriptional profiling of host gene expression in chicken embryo lung cells infected with laryngotracheitis virus

Background

Infection by infectious laryngotracheitis virus (ILTV; gallid herpesvirus 1) causes acute respiratory diseases in chickens often with high mortality. To better understand host-ILTV interactions at the host transcriptional level, a microarray analysis was performed using 4 × 44 K Agilent chicken custom oligo microarrays.

Results

Microarrays were hybridized using the two color hybridization method with total RNA extracted from ILTV infected chicken embryo lung cells at 0, 1, 3, 5, and 7 days post infection (dpi). Results showed that 789 genes were differentially expressed in response to ILTV infection that include genes involved in the immune system (cytokines, chemokines, MHC, and NF-κB), cell cycle regulation (cyclin B2, CDK1, and CKI3), matrix metalloproteinases (MMPs) and cellular metabolism. Differential expression for 20 out of 789 genes were confirmed by quantitative reverse transcription-PCR (qRT-PCR). A bioinformatics tool (Ingenuity Pathway Analysis) used to analyze biological functions and pathways on the group of 789 differentially expressed genes revealed that 21 possible gene networks with intermolecular connections among 275 functionally identified genes. These 275 genes were classified into a number of functional groups that included cancer, genetic disorder, cellular growth and proliferation, and cell death.

Conclusion

The results of this study provide comprehensive knowledge on global gene expression, and biological functionalities of differentially expressed genes in chicken embryo lung cells in response to ILTV infections.

Differential regulation of transferrin 1 and 2 in Aedes aegypti

Available evidence has shown that transferrins are involved in iron metabolism, immunity and development in eukaryotic organisms including insects. Here we characterize the gene and message expression profile of Aedes aegypti transferrin 2 (AaTf2) in response to iron, bacterial challenge and life stage. We show that AaTf2 shares a low similarity with A. aegypti transferrin 1 (AaTf1), but higher similarity with mammalian transferrins and avian ovotransferrin. Iron-binding pocket analysis indicates that AaTf2 has residue substitutions of Y188F, T120S, and R124S in the N lobe, and Y517N, H585N, T452S, and R456T in the C lobe, which could alter or reduce iron-binding activity. In vivo studies of message expression reveal that AaTf2 message is expressed at higher levels in larva and pupa, as well as adult female ovaries 72h post blood meal (PBM) and support that AaTf2 could play a role in larval and pupal development and in late physiological events of the gonotrophic cycle. Bacterial challenge significantly increases AaTf1 expression in ovaries at 0 and 24h PBM, but decreases AaTf2 expression in ovaries at 72h PBM, suggesting that AaTf1 and AaTf2 play different roles in immunity of female adults during a gonotrophic cycle.

Evaluation of the prophylactic use of ovotransferrin against chlamydiosis in SPF turkeys

Chlamydophila (C.) psittaci infections are highly prevalent in turkeys and the economical and public health importance of these infections has been recognized since 1950. As there are no vaccines, antibiotic treatment (tetracylines, enrofloxacine) is often needed to allow marketing of poultry. In this study, we explored the use of ovotransferrin (ovoTF), a natural anti-microbial protein, in preventing an experimental C. psittaci infection in specific pathogen free (SPF) turkeys. Turkeys were treated with aerosolized ovoTF prior to the infection. Groups 1 and 2 received a single dose of 10 and 5 mg ovoTF per turkey, respectively. Group 3 received a daily dose of 5mg ovoTF per turkey during 12 days. Group 4 served as untreated, infected control group. Turkeys were aerosol infected using 10(6) TCID(50) of the virulent C. psittaci serovar/genotype D strain 92/1293. Birds were monitored (clinical signs, bacterial excretion) during 12 subsequent days before being necropsied. At necropsy, pathology and C. psittaci replication in various tissues was examined. A single dose of 10mg ovoTF and a repeated daily dose of 5mg ovoTF could not prevent the birds from becoming infected with C. psittaci, but they significantly reduced the outcome of the infection. A single dose of 5mg ovoTF had no influence on the outcome of the infection as compared to the non-treated infected controls. Our results demonstrate the anti-chlamydial effect of ovoTF in vivo and present a base for further research on practical applications of ovoTF on turkey farms.