Transcriptomic analysis of early B-cell development in the chicken embryo

How to Break through the Bottlenecks of in Ovo Vaccination in Poultry Farming

Poultry farming is one of the pillar industries of global animal husbandry. In order to guarantee production, poultry are frequently vaccinated from the moment they are hatched. Even so, the initial immunity of chicks is still very poor as they are in the "window period" of immune protection. In ovo vaccination pushes the initial immunization time forward to the incubation period, thereby providing earlier immune protection for chicks. In ovo vaccination is currently a research hotspot of poultry disease prevention and control, which is in line with the intensification of poultry production. However, the vaccines currently available for in ovo vaccination are limited and cannot meet the needs of industrial development, so how to efficiently activate the adaptive immune response of chicken embryos becomes the key to restrict product development and technological progress of in ovo vaccination. Its breakthrough, to a large extent, depends on systematic illustration of the mechanism underlying the adaptive immune response post immunization. Clarification of this issue will provide us with theoretical support and potential solutions for the development of novel vaccines for in ovo vaccination, the augmentation of efficacy of current vaccines and the optimization of immune programs.

Transcriptome analysis revealed the roles of long non-coding RNA and mRNA in the bursa of Fabricius during pigeon (Columba livia) development

The bursa of Fabricius (BF) is the critical humoral immune organ to birds, playing an essential role in B lymphocyte differentiation. However, unlike other poultries, surgical removal of pigeon BF did not limit humoral immune responsiveness. To investigate the expression profiles and the potential role of mRNA and long non-coding RNA (LncRNA) in squab BFs, transcriptome analysis was performed by RNA-Sequencing (RNA-Seq) over three developmental stages (1-day, 13 and 26 days old). We identified 13,072 mRNAs and 19,129 lncRNAs, of which 2,752 mRNAs and 1,515 lncRNAs were differential expressed (DE) in pigeon BFs over three developmental stages. Cluster analysis presented different expression patterns in DE mRNAs and lncRNAs. Functional enrichment analysis revealed that DE lncRNAs and mRNAs with distinct expression patterns might play crucial roles in the immune system process and tissue morphogenesis. In particular, some DE genes and lncRNAs with higher expression levels in 13D or 26D are related to lymphocyte activation and differentiation, adaptive immune response, positive regulation of immune response, leukocyte migration, etc. Protein-protein interaction (PPI) network and Molecular Complex Detection (MCODE) analysis sreened six significant modules containing 37 genes from immune-related DE gene cluster, which is closely linked in B cell activation, lymphocyte differentiation, B cell receptor signaling pathway, etc. Our study characterizes mRNA and lncRNA transcriptomic variability in pigeon BFs over different developmental stages and enhances understanding of the mechanisms underlying physiological functions of pigeon BF.

Transcriptomic analysis of spleen B cell revealed the molecular basis of bursopentin on B cell differentiation

The bursa of Fabricius, the acknowledged humoral immune organ unique to birds, plays a vital role in B cell development. Bursopentin (BP5) derived from the bursa is reported to induce the development and formation of B cells. However, the mechanism of BP5 on B cell differentiation is still unclear. In this paper, total B lymphocytes from mice immunized with H9N2 subtype AIV vaccine were stimulated with BP5. The results show that BP5 at the experimental dosages promoted B cell differentiation, including the total B cells, activated B cells, differentiated B cells, mature B cells and plasma cells. Then, the in vivo immune experiment proved that the percentages of activated and differentiated B cells from mice immunized with AIV vaccine and 0.25 mg/mL BP5 were increased. To investigate the molecular mechanism of BP5 on B cell differentiation, the gene expression profiles of B cells purified from the spleen cells of mice immunized with AIV vaccine and BP5 were detected following RNA sequencing technology. The results show that BP5 at 0.05 and 0.25 mg/mL induced the enrichment of various biological functions, and stimulated five common significant enrichment pathways in B cells from the immunized mice. Additionally, 120 and 59 differentially expressed genes (DEG) represented transcriptional factors in B cells following 0.05 and 0.25 mg/mL BP5 immunization, respectively. In summary, these results suggest that BP5 regulates various gene expression involved in regulation of B cell development, which provides the knowledge required for additional studies on B cell differentiation in response to bursal-derived peptides and also provides an important experimental basis for improving vaccine immunity.

The Chicken Embryo Model: A Novel and Relevant Model for Immune-Based Studies

Dysregulation of the immune system is associated with many pathologies, including cardiovascular diseases, diabetes, and cancer. To date, the most commonly used models in biomedical research are rodents, and despite the various advantages they offer, their use also raises numerous drawbacks. Recently, another in vivo model, the chicken embryo and its chorioallantoic membrane, has re-emerged for various applications. This model has many benefits compared to other classical models, as it is cost-effective, time-efficient, and easier to use. In this review, we explain how the chicken embryo can be used as a model for immune-based studies, as it gradually develops an embryonic immune system, yet which is functionally similar to humans'. We mainly aim to describe the avian immune system, highlighting the differences and similarities with the human immune system, including the repertoire of lymphoid tissues, immune cells, and other key features. We also describe the general in ovo immune ontogeny. In conclusion, we expect that this review will help future studies better tailor their use of the chicken embryo model for testing specific experimental hypotheses or performing preclinical testing.

Characterization of the exosomes in the allantoic fluid of the chicken embryo

The embryo stage is critical for chicken development. Numerous studies have been conducted to clarify the dynamic changes and functions of various proteins and the composition of amino acids during embryo development. However, the physiological characteristics of extraembryonic fluid (allantoic and amniotic), especially allantoic fluid (AF), remain largely unexplored; furthermore, how information is transmitted from embryonic fluid is unknown. In this study, AF-derived exosomes ranging from 60 to 160 nm in diameter from fertilized eggs at 13 d of incubation of fast-growth chickens (WG chicken), medium-growth chickens (Silky N4 chicken), and slow-growth chickens (Huiyang Beard chicken) were isolated and purified by different ultra-centrifugations and further verified by transmission electron microscopy and a flow nano-analyzer. Expression of the exosomal positive biomarkers of ALIX and HSP70 as well as lack of the epithelium marker GRP78 was observed by Western blotting. In addition, small RNA sequencing revealed that AF-derived exosomes at 13 d of incubation contained a large number of known miRNAs (32.62%–65.83%). The top 10 most abundant and co-expressed miRNAs were primarily related to development, growth, and immunity. In addition, AF-derived exosomes promoted DF-1 cell migration. These findings broadened our understanding of the characteristic of AF-derived exosomes.

A Green and Blue Monochromatic Light Combination Therapy Reduces Oxidative Stress and Enhances B-Lymphocyte Proliferation through Promoting Melatonin Secretion

Artificial illumination may interfere with biological rhythms and distort physiological homeostasis in avian. Our previous study demonstrated that 660 nm red light exacerbates oxidative stress, but a combination of green and blue lights (G→B) can improve the antibody titer in chickens compared with single monochromatic light. Melatonin acts as an antioxidant which is a critical signaling to the coordination between external light stimulation and the cellular response from the body. This study further clarifies the potential role of melatonin in monochromatic light combination-induced bursa B-lymphocyte proliferation in chickens. A total of 192 chicks were exposed to a single monochromatic light (red (R), green (G), blue (B), or white (W) lights) or various monochromatic light combinations (B→G, G→B, and R→B) from P0 to P42. We used qRT-PCR, MTT, western blotting, immunohistochemistry, and Elisa to explore the effect of a combination of monochromatic light on bursa B-lymphocytes and its intracellular signal pathways. With consistency in the upregulation in melatonin level of plasma and antioxidant enzyme ability, we observed increases in organ index, follicle area, lymphocyte density, B-lymphocyte proliferation, PCNA-positive cells, and cyclin D1 expression in bursa of the G→B group compared with other light-treated groups. Melatonin bound to Mel1a and Mel1c and upregulated p-AKT, p-PKC, and p-ERK expression, thereby activating PI3K/AKT and PKC/ERK signaling and inducing B-lymphocyte proliferation. Overall, these findings suggested that melatonin modulates a combination of green and blue light-induced B-lymphocyte proliferation in chickens by reducing oxidative stress and activating the Mel1a/PI3K/AKT and Mel1c/PKC/ERK pathways.

Blocking of the CXCR4-CXCL12 Interaction Inhibits the Migration of Chicken B Cells Into the Bursa of Fabricius

B cells have first been described in chickens as antibody producing cells and were named after the Bursa of Fabricius, a unique organ supporting their development. Understanding different factors mediating the early migration of B cells into the bursa of Fabricius is crucial for the study of B cell biology. While CXCL12 (stromal derived factor 1) was found to play an important role in B lymphocyte trafficking in mammals, its role in the chicken is still unknown. Previous studies indicated that chicken CXCL12 and its receptor CXCR4 are simultaneously expressed during bursal development. In this study, we investigated whether the CXCR4/CXCL12 interaction mediates B cell migration in chicken embryo. We used the CRISPR/Cas9 system to induce a CXCR4 knockout in chicken B cells which led to chemotaxis inhibition toward CXCL12. This was confirmed by adoptive cell transfer and inhibition of the CXCR4/CXCL12 interaction by blocking with the small inhibitor AMD3100. In addition, we found that the chicken exhibits similarities to mice when it comes to CXCR4 being dependent on B cell receptor expression. B cells lacking the B cell receptor failed to migrate toward CXCL12 and showed no response upon CXCL12 stimulation. Overall, we demonstrated the significance of CXCR4/CXCL12 in chicken B cell development in vivo and the importance of the B cell receptor in CXCR4 dependent signaling.