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Reticuloendotheliosis virus (REV), an avian retrovirus is able to infect a variety of birds and can cause immunosuppression. The aim of this study was to investigate the relationship of thymic lymphocytes apoptosis, proliferation and T cell subtype with immunosuppression. In this study, a hundred and twenty one-day old SPF chickens were randomly divided into control groups (group C) and a REV infection groups (group I). The chickens of group I received intraperitoneal injections of REV with 10 4.62 /0.1 ml TCID 50 . On day 14, 21, 28 and 35 post-inoculation, the chickens of C group and I group were sacrificed by cardiac puncture blood collection, and the thymic lymphocytes was sterile collected. The proliferation ability of lymphocytes was tested by Cell Counting Kit-8. Flow cytometry was performed to detect apoptosis, cell cycle stage and the change in T cell subtype. The RNA genome copy numbers of REV virus were detected using real-time PCR. Real-time PCR and western blotting were performed to analyze the expression of CyclinD1 and Bcl-2. Our results showed that REV genome copy number steadily declined, the proliferation potential of thymic lymphocytes was inhibited, lymphocytes apoptosed, the ratio of CD4+/CD8+ decreased and the expression of CyclinD1 and Bcl-2 were firstly inhibited, then rapidly recovered. Thus, immunosuppression lead by REV is closely related to the change of T cell subtype, apoptosis, and proliferation of thymic lymphocytes., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Neddylation is a new type of protein post-translational modification which adds the ubiquitin-like molecule Nedd8 to target proteins. The well-identified targets of neddylation are cullins, which serve as essential components of Cullin-RING E3 ligases (CRL). It is reported that inhibition of neddylation repressed NF-κB-mediated proinflammatory cytokine production in macrophages. However, the role of neddylation in the proliferation and survival of macrophages has not been well defined. Here we report that partial inactivation of the neddylation pathway by a specific Nedd8-activating enzyme E1 (NAE) inhibitor MLN4924 reduced LPS-induced production of the proinflammatory cytokines TNF-α and IL-6 without obvious impairment of cell viability. However, persistent and severe inactivation of neddylation by MLN4924 significantly inhibited cell proliferation by inducing G2 phase cell-cycle arrest and further triggered cell death by inducing apoptosis in RAW264.7 macrophages. Mechanistic analysis revealed that inactivation of neddylation blocked cullin neddylation, inhibited CRL E3 ligase activity, and thus led to the accumulation of CRL substrates, resulting in cell-cycle arrest, DNA damage response and apoptosis. The findings revealed that neddylation serves as an important signaling pathway regulating the proliferation and survival of macrophages., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Alternative splicing (AS) plays a significant role in regulation of genomic expression at the transcriptional level and is involved in many important biological functions of cells, thus a gene can be spliced into distinct transcript variants then translated to many different kinds of protein. Reticuloendotheliosis virus (REV) is a kind of retrovirus that can infect multiple avian species, leading to runting syndrome, immunosuppression and oncogenesis. In this present study, we analyzed AS in REV-infected chicken embryo fibroblasts (CEFs) which were inoculated with the second generation of REV (group VB) and compared with normal CEFs (group C) by high-throughput RNA sequencing technology. A total of 6,939 genes which were alternatively spliced were detected, among them, skipped exon (SE) was the most common pattern. Moreover, 5,607 AS genes were detected as differentially expressed; compared with group C, group VB has 2,825 genes upregulated significantly and 2,782 genes downregulated significantly. These 5,607 differentially expressed AS genes are involved in many important biological processes. Many of them are involved in apoptosis and tumourigenesis. We also proved, by agarose gel electrophoresis, that AS events predicted by our study are authentic and AS is closely related with apoptosis and tumourigenesis in REV-infected CEFs. Our study provides the best analysis to date of the potential link between AS and CEFs in response to REV infection. Research highlights Transcriptomics analysis of REV-infected CEFs using high-throughput sequencing. Potential link between alternative splicing and CEFs in response to REV infection. Skipped exon is the most common spliced pattern in REV-infected CEFs. Differentially expressed genes mainly involved in apoptosis and tumourigenesis. [ABSTRACT FROM AUTHOR]

In this study, we found a much higher proportion of reticuloendotheliosis virus (REV) infected chicken embryo fibroblasts (CEF) were in active cell division phase than that of control cells which indicated that REV can affect the fate of CEF. So, we performed high-throughput sequencing and transcriptomic analysis to identify functional miRNAs, in order to figure out the possible mechanism in the interaction of REV with CEF. In total, 50 differentially expressed miRNAs (DEmiRNAs) were identified. Then target genes of DEmiRNAs were predicted and identified by transcriptome profile results. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment were conducted to analyze the identified target genes of miRNAs which showed that metabolism, cell cycle, and apoptosis were the most related pathways involved in infection of REV. We analyzed the genes related to cell cycle which indicated that CyclinD1-CDK6 complex played an important role in regulating the transition of the cell cycle from G1 phase to S phase during REV infection. Fluorescence microscope identification showed that REV inhibited the apoptosis of CEF which was in accordance with transcriptome results. A novel miRNA, named novel-72 was found, KEGG analysis was conducted to predict the biological function of its target genes which showed that those target genes were significantly enriched in mTOR signaling pathway and functioned to promote cell cycle and cell growth during the REV infection. In conclusion, REV could induce the up-regulation of cell metabolism, cell cycle and mTOR signaling pathway while inhibit apoptosis of the cell. [ABSTRACT FROM AUTHOR]

• Expression of miR-155 was upregulated in REV-infected CEFs in time- and dose-dependent manner. • Overexpression of miR-155 increased viability of REV-infected CEFs. • miR-155 inhibited apoptosis and promoted cell cycle of REV-infected CEFs. • miR-155 inhibited expression of caspase-6 and FOXO3a in REV-infected CEFs. Reticuloendotheliosis virus (REV) infection of multiple avian species can lead to a number of diseases such as runting syndrome, immunosuppression and oncogenesis, causing major economic losses. MicroRNAs play important roles in post-transcriptional regulation, effectively inhibiting protein synthesis, and participating in many biological processes in cells, including proliferation, differentiation, apoptosis, lipometabolism, virus infection and replication, and tumorigenesis. Based on our previous high-throughput sequencing results, we explore the regulatory mechanisms of microRNA-155(miR-155) in chicken embryo fibroblasts (CEFs) in response to REV infection. Our results revealed expression of miR-155 in CEFs after REV infection upregulated in a time- and dose-dependent manner, indicating miR-155 plays a role in REV infection in CEFs indeed. After transfected with miR-155-mimic and miR-155-inhibitor, we found overexpression of miR-155 targeted caspase-6 and FOXO3a to inhibit apoptosis and accelerate cell cycle, thus improving viability of REV-infected CEFs. This result also verified the protective role of miR-155 in the viability of CEFs in the presence of REV. Knockdown of miR-155 also supported these above conclusions. Our findings uncover a new mechanism of REV pathogenesis in CEFs, and also provide a theoretical basis for uncovering new effective treatment and prevention methods for RE based on miR-155. [ABSTRACT FROM AUTHOR]