Expression characteristics of miR-222b-5p/MAPK10 in major immune organs of SPF chickens infected with avian reticuloendotheliosis virus strain SNV (REV-SNV)

Reticuloendotheliosis virus (REV) is a retrovirus in poultry that can atrophy immune organs and cause immunosuppression and tumor diseases. Our previous results revealed that, in the spleen of SPF chickens infected with REV-SNV, gga-miR-222b-5p expression was upregulated at 7, 14 and 21 dpi, and MAPK10 expression was downregulated, both of which were negatively correlated, with a targeted relationship between the two at 28, 35 and 42 dpi. To understand and analyze the expression patterns of MAPK10 and gga-miR-222b-5p in infected chickens at different times and in different immune organs, qRT-PCR was used to analyze the spleen, bursa of Fabricius and thymus samples of SPF chickens at 7, 14, 21, 28, 35 and 42 dpi. The results revealed that, in the spleen, MAPK10 gene expression was highly significantly downregulated at 7, 14, 21, 35 and 42 dpi, and gga-miR-222b-5p expression was significantly upregulated at six-time points. In the bursa of Fabricius, MAPK10 expression was significantly downregulated at six-time points, and gga-miR-222b-5p expression was upregulated at 7, 21, 28, 35 and 42 dpi. In the thymus, MAPK10 and gga-miR-222b-5p expression was upregulated at six-time points. A negative regulatory relationship was evident in the spleen and bursa of Fabricius but not in the thymus. This study suggested that gga-miR-222b-5p may induce the downregulation of MAPK10 in the spleen and bursa of Fabricius and promote tumor formation.

Molecular characterization and immunopathological investigation of Avian reticuloendotheliosis virus in breeder flocks in Egypt

BACKGROUND

Reticuloendotheliosis virus (REV) is an oncogenic immunosuppressive retrovirus that infects different kinds of avian species; posing significant economic losses to the poultry industry worldwide.

METHODS

In Egypt, there is an unidentified disease associated with the runting-stunting syndrome with neoplasia, suspected to be REV, that has been continuously monitored in several breeder flocks. To diagnose and analyze REV by cell cultures, enzyme-linked immunosorbent assay (ELISA), histopathological investigation, the polymerase chain reaction (PCR) test, and sequencing analysis, 200 blood samples, and 50 tissue specimens were collected. The current study targets the occurrence and genetic characteristics of a viral neoplastic disease, resembling REV infection, circulating in breeder flocks from 2022 to 2023 in the Ismailia, El-Sharqia, and El-Dakahliya governorates.

RESULT

Here, REV was isolated on chicken embryo fibroblast cell culture; exhibiting cell aggregation, rounding, and cell detachments. Collectively, only 70 serum samples were positive for anti-REV antibodies with seroprevalence rates of 35% based on the ELISA test. The histopathological observation demonstrated lymphoreticular tumors in the liver, spleen, and other examined organs. The immunohistochemical staining method confirmed the REV-positive signals in all examined organs (liver, kidney, spleen, bursa, ovaries) except for the heart. The PCR assay of the LTR gene assessed 370 base pairs with only 5 positive samples with a percentage of 16.6%. Three positive samples were further sequenced and submitted to the Genbank under accession numbers (PP763709, PP763710, PP763711). Phylogenetic analysis of the REV-LTR gene showed that our three isolates (Sharquia-1-REV, Ismilia-2-REV, Mansoura-3-REV) are REV subtype III which predominantly circulated in breeders in Egypt. These three isolates are highest similar to American, Chinese, and Taiwanese REV reference strains, and other Egyptian strains with nucleotide identity percentages of 100%, 99%, and 99%; respectively, and on the amino acid identity level were with (99-100%), (98%, 99%), (99%, 100%); respectively.

CONCLUSIONS

This study established that REV infection was extensively distributed in the breeders and became one of the causes of the clinical outbreaks of tumors, raising awareness of REV as the causative agent of avian oncogenic disease in Egypt.

Semen-Derived Exosomes Mediate Immune Escape and Transmission of Reticuloendotheliosis Virus

Reticuloendotheliosis virus (REV) causes immune-suppression disease in poultry, leading to a significant economic burden worldwide. Recent evidence demonstrated that the REV can enter the semen and then induce artificial insemination, but how the virus gets into semen was little known. Accumulating studies indicated that exosomes serve as vehicles for virus transmission, but the role of exosomes in viral shedding through the semen remains unclear. In this study, exosomes purified from the REV-positive semen were shown with reverse transcription-PCR and mass spectrometry to contain viral genomic RNA and viral proteins, which could also establish productive infections both in vivo and in vitro and escape from the REV-specific neutralizing antibodies. More importantly, compared with the infection caused by free virions, the exosome is more efficient for the virus to ensure effective infection and replication, which can also help the REV compromise the efficacy of the host immune response. In summary, this study demonstrated that semen-derived exosomes can medicate the transmission and immune escape of REV, implicating a novel mechanism for REV entering the semen and leading to vertical transmission.

Poly (I: C) inhibits reticuloendothelial virus replication in chicken macrophage-like cells through the activation of toll-like receptor-3 signaling

Reticuloendothelial virus (REV) is widely found in many domestic poultry areas and results in severe immunosuppression of infected chickens. This increases the susceptibility to other pathogens, which causes economic losses to the poultry industry. The aim of our study was to determine whether polyinosinic-polycytidylic acid [Poly (I: C)] treatment could inhibit REV replication in chicken macrophage-like cell line, HD11. We found that Poly (I: C) treatment could markedly inhibit REV replication in HD11 from 24 to 48 h post infection (hpi). Additionally, Poly (I: C) treatment could switch HD11 from an inactive type into M1-like polarization from 24 to 48 hpi. Furthermore, Poly (I: C) treatment promoted interferon-β secretion from HD11 post REV infection. Moreover, Toll-like receptor-3 (TLR-3) mRNA and protein levels in HD11 treated with Poly (I: C) were markedly increased compared to those of HD11 not treated with Poly (I: C). The above results suggested that Poly (I: C) treatment switches HD11 into M1-like polarization to secret more interferon-β and activate TLR-3 signaling, which contributes to block REV replication. Our findings provide a theoretical reference for further studying the underlying pathogenic mechanism of REV and Poly (I: C) as a potential therapeutic intervention against REV infection.

Reemergence of reticuloendotheliosis virus and Marek's disease virus co-infection in Yellow-Chickens in Southern China

The reticuloendotheliosis virus (REV) and the Marek's disease virus (MDV) cause reticuloendotheliosis (RE) and Marek's disease (MD) in poultry, respectively. According to epidemiological results obtained in our laboratory from 2010 to 2017, the positive rates of REV and MDV co-infection remained at low levels. In the present study, during the period of October 2018 to July 2020, 4 clinical cases with high morbidity (5%-20%) and mortality (2%-10%), caused by the co-infection of REV and vv+ MDV-like strains, were diagnosed and analyzed by histopathological observation, cell cultures and detection with ELISA and IFA, and the PCR and by sequencing of the isolates’ genes. Sequencing and the sequence analysis on the complete genomes of the REV strains and the meq genes of the MDV strains were performed. The results, based on the complete genome, LTR, gag, pol, and env genes’ nucleotide sequences of the REV strains, showed that the REV isolates and 68.0 % (17/25) of the reference strains were in a same branch, and all had a high sequence similarity (>99.0%). The similarities between the four isolates and a vv+MDV strain GX18NNM4 were very high, up to 99.3-99.8%. Also, the amino acid residuals at locations 71, 77, 80, 115, 139, 176, and 217 were all the same as A, E, Y, A, A, R, and A, respectively, in the meq gene of the four MDV isolates. In addition, the substitutes at P176R and P217A interrupted the stretches of the proline-rich repeat PPPP, indicating that these strains belonged to the vv+ MDV-like category. Our findings indicated that the more recent and frequent reemergence of REV and the subsequent co-infection with vv+ MDV-like strain has become one of the causes of the clinical outbreaks of tumors and is undoubtedly a threat to the poultry industry in southern China.

An optimized secretory expression system and immunogenicity evaluation for glycosylated gp90 of avian reticuloendotheliosis virus

Reticuloendotheliosis is an important immunosuppressive disease, associated with avian reticuloendotheliosis virus (REV) infection, and causes notable economic losses worldwide. Glycoprotein gp90 is an important structural protein of REV, and considered to be the most important immunogenic antigen, which can induce neutralizing antibodies against REV. In this study, an optimized suspension culture system was developed and applied to secretory express the immunogenic surface antigen gp90. To achieve an optimal glycosylation, the gp90 was designed to secretory expressed into the supernatant of the cell culture, which also occurs in the natural protein maturation procedure of REV. Serum-free culture medium was introduced to simplify the purification process and reduce the production costs. Based on the purified glycosylated gp90, an oil-emulsion subunit REV vaccine candidate was developed and evaluated in chickens. The subunit gp90-based vaccine induced fast immune responses, high levels of antibodies (REV-specific antibody, gp90-specific antibody, and neutralizing antibody against REV), and preferential T helper 2 (Th2) (interleukin-4 secretion) not Th1 (interferon-γ secretion) response. Furthermore, the viremia induced by REV infection was significantly reduced in chickens immunized with the glycosylated gp90. Overall, an optimized secretory expression system for glycosylated gp90 was developed, and the glycosylated gp90 obtained in this study retained good immunogenicity and could be an attractive vaccine candidate to protect chickens against REV horizonal infection.

Development and Application of an MRT-qPCR Assay for Detecting Coinfection of Six Vertically Transmitted or Immunosuppressive Avian Viruses

Marek's disease virus (MDV), reticuloendotheliosis virus (REV), avian reovirus (ARV), chicken infectious anemia virus (CIAV), infectious bursal disease virus (IBDV), and fowl adenovirus (FAdV) are important causes of disease in poultry. To investigate the infection status of the above six viruses in chickens in China, 1,187 samples from chicken flocks were collected and tested using a newly developed multiplex reverse-transcription quantitative real-time PCR (MRT-qPCR) assay in the study. A series of validation tests confirmed that the MRT-qPCR assay has high specificity, sensitivity, and repeatability. As for six detected pathogens, CIAV had the highest detection ratio, while ARV was not detected in any samples. In the spleen samples, the coinfection rate for MDV and CIAV was 1.6%, and that for REV and CIAV was 0.4%. In the bursa samples, the coinfection rate for FAdV and CIAV was 0.3%, and that for IBDV and CIAV was 1%. In the thymus samples, the coinfection rates for MDV and CIAV and for REV and CIAV were both 0.8%. Our study indicates that the coinfection of these viruses was existing in chickens in China. Through the detection of clinical samples, this study provides data on the coinfections of the above six pathogens and provides a basis for the further study of viral coinfection in chickens.

Gut microbiota profiles of commercial laying hens infected with tumorigenic viruses

BACKGROUND

Studies have shown that some viral infections cause structural changes in the intestinal microflora, but little is known about the effects of tumorigenic viral infection on the intestinal microflora of chickens.

RESULTS

A 29-week commercial layer flock positive for avian leukosis virus-J (ALV-J), Marek's disease virus (MDV) and avian reticuloendotheliosis virus (REV) was selected, and fresh fecal samples were collected and examined for the composition of the gut microflora by Illumina sequencing of the V3-V4 region of the 16S rRNA gene. The operational taxonomic units (OTUs) of the fecal microbiota differentiated the chickens infected with only ALV-J and those coinfected with ALV-J and MDV or REV from infection-negative chickens. The enrichment and diversity of cloacal microflora in chickens infected with ALV-J alone were slightly different from those in the infection-negative chickens. However, the diversity of cloacal microflora was significantly increased in chickens coinfected with both ALV-J and MDV or REV.

CONCLUSIONS

The intestinal microbiota was more strongly disturbed in chickens after coinfection with ALV-J and MDV or REV than after infection with ALV-J alone, and there may be underlying mechanisms by which the capacity for the stabilization of the intestinal flora was impaired due to viral infection and tumorigenesis.

Genetic characterization of reticuloendotheliosis virus in chickens in Thailand

Reticuloendotheliosis virus (REV) causes an immunosuppressive, runting, and oncogenic disease in poultry, posing a significant threat to the poultry industry. In Thailand, an unidentified disease associated with runting-stunting syndrome and neoplasia, resembling REV infection, has been continuously observed in several chicken farms. However, REV infection in Thailand has never been reported. In this study, we investigated the occurrence and genetic characteristics of REVs in chickens in Thailand from 2013 to 2016. Of the 130 clinical samples obtained from 29 chicken farms from 9 provinces located in the major chicken-raising regions of Thailand, including the central, eastern, northern, and northeastern parts of Thailand, 51 samples (39.23%) and 21 farms (72.41%) were REV-positive. REV-positive samples were detected in all 9 provinces tested. Our results demonstrated that REV was extensively distributed in the major chicken-raising regions of Thailand. Phylogenetic analysis of the whole genome sequence showed that Thai REV was most closely related to Chinese, Taiwanese, and the US REV strains isolated from different avian species and clustered into REV subtype III. This finding indicates that REV subtype III was predominantly circulated in Thai chicken flocks. This study is the first report on REV infection in chickens in Thailand. Our findings raise the awareness of REV as another causative agent of runting and oncogenic disease in chickens in Thailand and highlight the wide distribution of REV infection among chickens worldwide.

Transcriptional analysis of host responses related to immunity in chicken spleen tissues infected with reticuloendotheliosis virus strain SNV

In avian species, the Reticuloendotheliosis virus (REV) causes severe immunosuppression and other symptoms, including avian dwarfing syndrome, and chronic tumors in lymphoid and other tissues. The pathogenesis of REV and its interaction with the host have yet to be fully elucidated with transcriptional studies on the changes in host gene expression after REV infection at the body level. In this study, the Spleen Necrosis Virus (SNV) was used to inoculate the one-day-old specific pathogen free (SPF) chicken to simulate congenital infection. We identified 1507 differentially expressed genes (DEGs) at 7, 14 and 21 dpi using Next Generation Sequencing (NGS) technology. Through the Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of these DEGs, it was found that DEGs were mainly involved in the categories of signal transduction, immune system and signaling molecules and interaction. Among them, Pattern recognition receptors (PRRs), chemokine, T cell receptor, JAK-STAT, TNF, and NF-kappa B signaling pathway, and the Hematopoietic cell lineage play an important role in the tumorigenic and immunosuppressive regulation of REV. In addition, a series of DEGs associated with inflammatory factors (CCL4, TNFRSF18, CDKN2), apoptosis (IRF1, PDCD1, WNT5A), innate immunity (TLR, MAD5, TRIM25), and adaptive immunity (LY6E, CD36, LAG3) were also discovered. We further verified 33 selected immune- relevant DEGs using quantitative RT-PCR (qRT-PCR). These findings provide new insights and research directions for revealing the pathogenesis of REV infection and the interaction between REV and the chicken immune system.

Changes in apoptosis, proliferation and T lymphocyte subtype on thymic cells of SPF chickens infected with reticuloendotheliosis virus

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 TCID₅₀. 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.

The experimental transmission of reticuloendotheliosis virus by cock semen

Following artificial insemination, the egg-laying rate of a large-scale breeder chicken flock declined by10-15 %. Real-time quantitative polymerase chain reaction (qPCR) analysis detected the presence of reticuloendotheliosis virus (REV) in semen from the breeder cocks used. Six REV strains were successfully isolated from semen randomly extracted from those cocks. Additionally, the whole sequence of SDAUR-S1 was sequenced and analysed. Cock models with continuous production of REV-positive semen were established by intravenous injection with SDAUR-S1. Eggs were then collected from hens after artificial insemination with REV-positive semen, for virus detection. The positive REV antibody rate for egg albumen was 58.3 % and the REV-positive rate for hatched embryos was 8.3 %, which suggested not only that REV can infect cock semen, but can also infect the offspring. In conclusion, the present study is the first to report on the isolation, genome analysis and transmission of REV in cock semen.