Search

Background: Pigeon leukosis is primarily caused by avian leukosis virus subgroup A (ALV-A). It infects and transforms lymphoid cells, leading to the development of tumors in various lymphoid tissues and other organs especially the liver., Aim: This study was conducted to diagnose lymphoid leukosis in a naturally infected pigeon flock in Egypt., Methods: Tissue specimens from the liver, spleen, thymus, kidney, lung, proventriculus, gizzard, intestine, pancreas, heart, pectoral muscle, ovary, and testes were collected from infected birds for pathological and immunohistochemical examinations., Results: Clinical signs were generally nonspecific and comprised weakness, dehydration, and emaciation. Gross lesions were mostly in the liver and spleen, in the form of minute white nodules scattered on the liver surface. Microscopic examination of the liver, spleen, and kidneys showed masses of uniform sizes and the presence of differentiated lymphoid cells. These cells appeared as large mononuclear cells with poorly defined cell membranes. Immunohistochemical investigation exhibited that the ALV-A positive indicators were chiefly accessible in the liver, ovary, spleen, and kidney., Conclusion: Lymphoid leukosis in pigeons could be provisionally diagnosed by a pathological picture of characteristic tumors and confirmed by immunoreactivity of viral antigens in different tissues., Competing Interests: The authors claim no conflicts of interest in publishing this research.

Background: Avian leukosis virus Subgroup-J (ALV-J) is a rapidly oncogenic evolving retrovirus infecting a variety of avian species; causing severe economic losses to the local poultry industry., Methods: To investigate ALV-J, a total of 117 blood samples and 57 tissue specimens of different organs were collected for virological, and pathological identification, serological examinations, molecular characterization, and sequencing analysis. To the best of our knowledge, this is the first detailed report recorded in broiler flocks in Egypt. The present study targets the prevalence of a viral tumor disease circulating in broiler flocks in the El-Sharqia, El-Dakahliya, and Al-Qalyubiyya Egyptian governorates from 2021 to 2023 using different diagnostic techniques besides ALV-J gp85 genetic diversity determination., Result: We first isolated ALV-J on chicken embryo rough cell culture; showing aggregation, rounding, and degeneration. Concerning egg inoculation, embryonic death, stunting, and curling were observed. Only 79 serum samples were positive for ALV-J (67.52%) based on the ELISA test. Histopathological investigation showed tumors consist of uniform masses, usually well-differentiated myelocytes, lymphoid cells, or both in the liver, spleen, and kidneys. Immunohistochemical examination showed that the myelocytomatosis-positive signals were in the spleen, liver, and kidney. The PCR assay of ALV-J gp85 confirmed 545 base pairs with only 43 positive samples (75.4%). Two positive samples were sequenced and submitted to the Genbank with accession numbers (OR509852-OR509853). Phylogenetic analysis based on the gp85 gene showed that the ALV-J Dakahlia-2 isolate is genetically related to ALV-EGY/YA 2021.3, ALV-EGY/YA 2021.4, ALV-EGY/YA 2021.14, and ALV-EGY/YA 2021.9 with amino acid identity percentage 96%, 97%; 96%, 96%; respectively. Furthermore, ALV-J Sharqia-1 isolate is highly genetically correlated to ALV-EGY/YA 2021.14, and ALV-EGY/YA 2021.9, ALV-J isolate QL1, ALV-J isolate QL4, ALV-J isolate QL3, ALV-EGY/YA 2021.4 with amino acid identity percentage 97%, 97%; 98%, 97%, 97%, 95%; respectively., Conclusions: This study confirmed that ALV-J infection had still been prevalent in broilers in Egypt, and the genetic characteristics of the isolates are diverse., (© 2024. The Author(s).)

Tibetan chicken is found in China Tibet (average altitude; ˃4500 m). However, little is known about avian leukosis virus subgroup J (ALV-J) found in Tibetan chickens. ALV-J is a typical alpharetrovirus that causes immunosuppression and myelocytomatosis and thus seriously affects the development of the poultry industry. In this study, Tibet-origin mutant ALV-J was isolated from Tibetan chickens and named RKZ-1-RKZ-5. A Myelocytomatosis outbreak occurred in a commercial Tibetan chicken farm in Shigatse of Rikaze, Tibet, China, in March 2022. About 20% of Tibetan chickens in the farm showed severe immunosuppression, and mortality increased to 5.6%. Histopathological examination showed typical myelocytomas in various tissues. Virus isolation and phylogenetic analysis demonstrated that ALV-J caused the disease. Gene-wide phylogenetic analysis showed the RKZ isolates were the original strains of the previously reported Tibetan isolates (TBC-J4 and TBC-J6) (identity; 94.5% to 94.9%). Furthermore, significant nucleotide mutations and deletions occurred in the hr1 and hr2 hypervariable regions of gp85 gene, 3'UTR, Y Box, and TATA Box of 3'LTR. Pathogenicity experiments demonstrated that the viral load, viremia, and viral shedding level were significantly higher in RKZ-1-infected chickens than in NX0101-infected chickens. Notably, RKZ-1 caused more severe cardiopulmonary damage in SPF chickens. These findings prove the origin of Tibet ALV-J and provide insights into the molecular characteristics and pathogenic ability of ALV-J in the plateau area. Therefore, this study may provide a basis for ALV-J prevention and eradication in Tibet., Competing Interests: Declaration of Competing Interest The authors declare that they have no potential conflicts of interest., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Avian leukosis virus (ALV) causes various diseases associated with tumor formation and decreased fertility. Moreover, ALV induces severe immunosuppression, increasing susceptibility to other microbial infections and the risk of failure in subsequent vaccination against other diseases. There is growing evidence showing the interaction between ALV and the host. In this review, we will survey the present knowledge of the involvement of host factors in the important molecular events during ALV infection and discuss the futuristic perspectives from this angle., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Tang, Li, Chang and Lin.)

Fowl glioma-inducing virus (FGV), a strain of avian leukosis virus (ALV) subgroup A, is the causal agent of fowl glioma characterized by multiple nodular astrocytic growths, gliosis, and lymphocytic encephalitis. Also associated with FGV infection are cases of cerebellar hypoplasia, perineuromas, and nonsuppurative myocarditis. Though fowl glioma has been recognized in several countries, most reports of FGV infection come from Japan. A 9-mo-old brown leghorn from a German farm with nine leghorns was presented to a veterinarian with an impaired general health with torticollis, tremor, and incoordination. Histopathology revealed multifocal nodular astrocytic growths, gliosis, and a lymphoplasmacytic encephalitis. Immunohistochemically, neoplastic astrocytes showed positivity for anti-ALV antibody. FGV was detected in the brain with nested reverse transcription-polymerase chain reaction (RT-PCR) and subsequent sequencing of PCR product. The remaining eight birds were screened for the presence of ALV with real-time RT-PCR. Four leghorns tested positive for exogenous ALV in nested RT-PCR with an identical nucleotide sequence as the leghorn with neurological symptoms. To the authors' knowledge this is the first report of a natural FGV infection in a brown leghorn in Germany with clinical manifestation.

MicroRNAs (miRNAs) involved host-virus interaction, affecting the replication or pathogenesis of several viruses. Although avian leukosis virus subgroup J (ALV-J) has been one of the most studied avian viruses, the effects of various host miRNAs on ALV-J infection and its underlying molecular mechanisms are still unclear. Here, we reported that gga-miR-200b-3p acts as a positive host factor enhancing ALV-J replication. We found that gga-miR-200b-3p was increased in response to ALV-J infection in host cells, and that gga-miR-200b-3p effectively enhanced ALV-J replication via targeting host protein dual-specificity phosphatase 1 (DUSP1). Collectively, these findings highlight a crucial role of gga-miR-200b-3p in ALV-J replication., (Copyright © 2021 Elsevier B.V. All rights reserved.)

This study aimed to explore the mutual regulation between chicken telomerase reverse transcriptase (chTERT) and the Wnt/β-catenin signalling pathway and its effects on cell growth and avian leukosis virus subgroup J (ALV-J) replication in LMH cells. First, LMH cells stably overexpressing the chTERT gene (LMH-chTERT cells) and corresponding control cells (LMH-NC cells) were successfully constructed with a lentiviral vector expression system. The results showed that chTERT upregulated the expression of β-catenin, Cyclin D1, TCF4 and c-Myc. chTERT expression level and telomerase activity were increased when cells were treated with LiCl. When the cells were treated with ICG001 or IWP-2, the activity of the Wnt/β-catenin signalling pathway was significantly inhibited, and chTERT expression and telomerase activity were also inhibited. However, when the β-catenin gene was knocked down by small interfering RNA (siRNA), the changes in chTERT expression and telomerase activity were consistent with those in cells treated with ICG001 or IWP-2. These results indicated that chTERT and the Wnt/β-catenin signalling pathway can be mutually regulated. Subsequently, we found that chTERT not only shortened the cell cycle to promote proliferation but also inhibited apoptosis by downregulating the expression of Caspase 3, Caspase 9 and BAX; upregulating BCL-2 and BCL-X expression; and promoting autophagy. Moreover, chTERT significantly enhanced the migration ability of LMH cells, upregulated the protein and mRNA expression of ALV-J and increased the virus titre. ALV-J replication promoted chTERT expression and telomerase activity., (© 2021. The Author(s).)

Histomonas meleagridis is a trichomonad protozoan parasite that can cause an important poultry disease known as histomoniasis; Marek's disease virus (MDV) and subtype J avian leukosis virus (ALV-J) usually cause avian oncogenic diseases. Although these diseases have been reported in a single pathogen infection, information about their coinfection is scarce. This study reports a naturally occurring case of coinfection with H. meleagridis , MDV, and ALV-J in a local chicken flock at the age of 150 days. Necropsy revealed necrosis and swelling in the liver and spleen. Histologic analysis showed large areas of mild to severe necrosis of hepatocytes, with numerous intralesional trophozoites of H. meleagridis by H&E and periodic acid-Schiff staining; H&E staining showed pleomorphic and neoplastic lymphoid tumor cells in the liver and myeloid cells with eosinophilic cytoplasmic granules in the spleen. Coexpression of MDV and ALV-J antigens was detected in the liver by fluorescence multiplex immunohistochemistry staining. The 18S rRNA gene of H. meleagridis , meq gene of MDV, and gp85 gene of ALV-J were identified in mixed liver and spleen tissues by PCR and sequencing, respectively.

Avian leukosis caused by avian leukosis virus (ALV) is one of the most severe diseases endangering the poultry industry. When the eradication measures performed in commercial broilers and layers have achieved excellent results, ALV in some local chickens has gradually attracted attention. Since late 2018, following the re-outbreak of ALV-J in white feather broilers in China, AL-like symptoms also suddenly broke out in some local flocks, leading to great economic losses. In this study, a systematic epidemiological survey was carried out in eight local chicken flocks in Jiangxi Province, China, and 71 strains were finally isolated from 560 samples, with the env sequences of them being successfully sequenced. All of those new isolates belong to subgroup J but they have different molecular features and were very different from the strains that emerged in white feature broilers recently, with some strains being highly consistent with those previously isolated from commercial broilers, layers and other flocks or even isolated from USA and Russian, suggesting these local chickens have been acted as reservoirs to accumulate various ALV-J strains for a long time. More seriously, phylogenetic analysis shows that there were also many novel strains emerging and in a separate evolutionary branch, indicating several new mutated ALVs are being bred in local chickens. Besides, ALV-J strains isolated in this study can be further divided into ten groups, while there were more or fewer groups in different chickens, revealing that ALV may cross propagate in those flocks. The above analyses explain the complex background and future evolution trend of ALV-J in Chinese local chickens, providing theoretical support for the establishment of corresponding prevention and control measures.

Since subgroup J avian leukosis virus (ALV-J) was first isolated in the United Kingdom in 1988, it has seriously hindered the development of the poultry industry worldwide. Although cases of ALV-J infection have been reported as early as 2001 in Pakistan, there was no further research on the isolation and molecular characteristics of ALVs. In the present study, we first isolated two ALVs from suspicious clinical samples that were collected from a desi chicken farm in Pakistan. The results of multiplex PCR and indirect immunofluorescent antibody assays confirmed that the two isolates (PK19FA01 and PK19SA01) belonged to ALV-J. The complete genomes of the two isolates were amplified, sequenced, and systematically analyzed. We found that gp85 of PK19FA01 was more similar to that of the prototype strain HPRS103, whereas gp85 of PK19SA01 was more similar to that of American strains. The two isolates contained an intact E element of 147 residues and had a unique 135 bp deletion in the redundant transmembrane of the 3' untranslated region. The U3 region of the two isolates was highly homologous to that of American ALV-J strains. To our knowledge, this is the first report of the isolation, complete genome sequencing, and systematic molecular epidemiological investigation of ALV-J in Pakistan. Our findings could enrich epidemiological data and might contributed to more effective measures to prevent and control avian leukosis in Pakistan., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Different from other subgroups of avian leukosis viruses (ALVs), ALV-J is highly pathogenic. It is the main culprit causing myeloid leukemia and hemangioma in chickens. The distinctiveness of the env gene of ALV-J, with low homology to those of other ALVs, is linked to its unique pathogenesis, but the underlying mechanism remains unclear. Previous studies show that env of ALV-J can be grouped into three species based on the tyrosine motifs in the cytoplasmic domain (CTD) of Gp37, i.e., the inhibitory, bifunctional, and active groups. To explore whether the C terminus or the tyrosine motifs in the CTD of Gp37 affect the pathogenicity of ALV-J, a set of ALV-J infectious clones containing different C termini of Gp37 or the mutants at the tyrosine sites were tested in vitro and in vivo Viral growth kinetics indicated not only that ALV-J with active env is the fastest in replication and ALV-J with inhibitory env is the lowest but also that the tyrosine sites essentially affected the replication of ALV-J. Moreover, in vivo studies demonstrated that chickens infected by ALV-J with active or bifunctional env showed higher viremia, cloacal viral shedding, and viral tissue load than those infected by ALV-J with inhibitory env Notably, the chickens infected by ALV-J with active or bifunctional env showed significant loss of body weight compared with the control chickens. Taken together, these findings reveal that the C terminus of Gp37 plays a vital role in ALV-J pathogenesis, and change from inhibitory env to bifunctional or active env increases the pathogenesis of ALV-J. IMPORTANCE ALV-J can cause severe immunosuppression and myeloid leukemia in infected chickens. However, no vaccine or antiviral drug is available against ALV-J, and the mechanism for ALV-J pathogenesis needs to be elucidated. It is generally believed that gp85 and LTR of ALV contribute to its pathogenesis. Here, we found that the C terminus and the tyrosine motifs (YxxM, ITIM, and ITAM-like) in the CTD of Gp37 of ALV-J could affect the pathogenicity of ALV-J in vitro and in vivo The pathogenicity of ALV-J with Gp37 containing ITIM only was significantly less than ALV-J with Gp37 containing both YxxM and ITIM and ALV-J with Gp37 containing both YxxM and ITAM-like. This study highlights the vital role of the C terminus of Gp37 in the pathogenesis of ALV-J and thus provides a new perspective to elucidate the interaction between ALV-J and its host and a molecular basis to develop efficient strategies against ALV-J., (Copyright © 2020 American Society for Microbiology.)

In this study, a novel oral vaccine of recombinant Lactobacillus plantarum ( L. plantarum ) containing the gp85 protein was explored, and the effects of this vaccine on the prevention of subgroup J Avian Leukosis Virus (ALV-J) infection were assessed. In the current study, the gp85 protein of ALV-J was expressed on the surface of L. plantarum with the surface-display motif, pgsA , by constructing a shuttle vector pMG36e:pgsA:gp85 . Surface localization of the fusion protein was verified by western blotting and flow cytometry. Subsequently, Specific Pathogen Free Hy-Line Brown layer chickens were orally vaccinated with the recombinant L. plantarum and presented with high levels of serum immunoglobulin G (IgG) and secretory immunoglobulin A (sIgA) titers in bile and duodenal-mucosal fluid. After challenged with ALV-J of a 3 × 10 3 50% tissue culture infective dose (TCID50), serum samples of the chickens were collected and viremia was analyzed. Results showed that, compared to the L. plantarum and PBS control group, the recombinant L. plantarum group showed a significant rise in antibody levels after inoculation, and provide improved protection against ALV-J according to viremia detection. These results indicate that oral immunization with the recombinant L. plantarum provided an effective means for eliciting protective immune response against early ALV-J infection., (Copyright © 2019 Wang, Geng, Zhou, Qu, Shi, Xu, Liu, Liu and Liu.)

We investigated the histologic findings and viral antigen distribution in 3 cases of natural coinfection of layer hens with subgroup J avian leukosis virus (ALV-J), Marek's disease virus (MDV), and reticuloendotheliosis virus (REV) in hens. At autopsy, diseased hens were found to have hepatosplenomegaly and thickened proventriculi, with white tumor nodules in the liver, spleen, lung, kidney, and ovary. Microscopically, most tissues had been infiltrated by neoplastic lymphocytes; the spleen, lung, proventriculus, heart, and liver had been infiltrated by both neoplastic lymphocytes and myeloblastic cells and/or primitive reticular cells. Fluorescence multiplex immunohistochemistry staining revealed ALV-J, MDV, and REV antigens co-expressed in the same tissue, even the same cell.

Avian leukosis virus subgroup J has been found to infect many types of chickens with various genetic backgrounds. The ALV-J strain NX0101, which was isolated from broiler breeders in 2001, mainly induces the formation of myeloid cell tumors. However, strain HN10PY01, which was recently isolated from laying hens, mainly induces the formation of myeloid cell tumors and hemangioma. In order to determine the difference in pathogenicity of the 2 strains in broiler chickens, 2 groups of chicken embryos were infected with NA0101 and HN10PY01 separately. A comparison was made of the mortality, oncogenicity, body weights, indexes for immune organs, levels of ALV group-specific antigen p27, and mRNA expression levels of the tumor-related gene, p53, in ALV-J-infected birds and immune organs of theses chickens in response to Newcastle Disease Virus (NDV) and avian influenza virus subtype H9 (AIV-H9) vaccination. The results indicated that strain NX0101 was highly pathogenic in broiler chickens and led to a 30% mortality rate and 45% oncogenicity, compared with the HN10PY01-infected birds. Weight of chickens was also significantly lower after 15 wk (P < 0.05). In addition, the mRNA expression levels of tumor-related p53 in medulla, liver, and lung in broilers infected with strain NX0101 were significantly higher than those infected with strain HN10PY01 (P < 0.05). These results indicated that strain NX0101 had a higher replication ability in broiler chickens. The findings of this study will contribute to further elucidating the mechanisms underlying host susceptibility and tumor classification in ALV-J-infected chickens., (© 2019 Poultry Science Association Inc.)

Avian leukosis virus subgroup J (ALV-J) is an oncogenic retrovirus that causes severe economic losses to the poultry industry worldwide. Circular RNAs (circRNAs) are a class of non-coding RNAs that has been described in various biological systems and pathogenic processes. However, the immune mechanisms in response to circRNAs remain unknown. In this study, high-throughput transcriptome sequencing was used to detect circRNAs present in chicken macrophage (HD11) and chick embryo fibroblast (CEF) cells infected with ALV-J. We identified 7684 circRNAs from diverse genomic locations in CEF and HD11 after ALV-J infection, these RNAs showed complex expression patterns that differed based on the cells type and infection time. In total, 302 differentially expressed (DE) circRNAs and 164 DE circRNAs were identified in CEF and HD11 after ALV-J infection, respectively. CircRNA7419-associated with KDM4C- and circRNA6679 and circRNA6680-associated with TNFAIP6- were involved in the immune response upon ALV-J infection in CEF. Host genes were analyzed through further bioinformatics analysis. The result confirmed that a large number of DE circRNAs corresponded to several immune-associated or tumor-associated terms and pathways, such as Mucin type O-Glycan biosynthesis, MAPK signaling pathway, B cell receptor signaling, and Wnt signaling pathway in CEF, as well as Jak-STAT signaling pathway, apoptosis, and MAPK signaling pathway in HD11. CircRNAs related to the B cell receptor signaling pathway in CEF, and the Jak-STAT signaling pathway in HD11, were selected for circRNA-miRNA interaction network analyses. Our study indicates that circRNAs expression was altered by ALV-J infection in both CEF and HD11, and may play a key role in the progression of ALV-J infection., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Background: The pathogenesis of immunological tolerance caused by avian leukosis virus subgroup J (ALV-J), an oncogenic retrovirus, is largely unknown., Results: In this study, the development, differentiation, and immunological capability of B cells and their progenitors infected with ALV-J were studied both morphologically and functionally by using a model of ALV-J congenital infection. Compared with posthatch infection, congenital infection of ALV-J resulted in severe immunological tolerance, which was identified as the absence of detectable specific antivirus antibodies. In congenitally infected chickens, immune organs, particularly the bursa of Fabricius, were poorly developed. Moreover, IgM-and IgG-positive cells and total immunoglobulin levels were significantly decreased in these chickens. Large numbers of bursa follicles with no differentiation into cortex and medulla indicated that B cell development was arrested at the early stage. Flow cytometry analysis further confirmed that ALV-J blocked the differentiation of CD117 + chB6 + B cell progenitors in the bursa of Fabricius. Furthermore, both the humoral immunity and the immunological capability of B cells and their progenitors were significantly suppressed, as assessed by (a) the antibody titres against sheep red blood cells and the Marek's disease virus attenuated serotype 1 vaccine; (b) the proliferative response of B cells against thymus-independent antigen lipopolysaccharide (LPS) in the spleen germinal centres; and (c) the capacities for proliferation, differentiation and immunoglobulin gene class-switch recombination of B cell progenitors in response to LPS and interleukin-4(IL-4) in vitro., Conclusions: These findings suggested that the anergy of B cells in congenitally infected chickens is caused by the developmental arrest and dysfunction of B cell progenitors, which is an important factor for the immunological tolerance induced by ALV-J.

In recent years, cases of avian leukosis virus (ALV) infection have become more frequent in China. We isolated 6 ALV strains from yellow feather broiler breeders in south China from 2014 to 2016. Their full genomes were sequenced, compared, and analyzed with other reference strains of ALV. The complete genomic nucleotide sequences of GD150509, GD160403, GD160607, GDFX0601, and GDFX0602 were 7482 bp in length, whereas GDFX0603 was 7480 bp. They shared 99.7% to 99.8% identity with each other. Homology analysis showed that the gag , pol , long terminal repeats (LTRs), and the transmembrane region (gp37) of the env genes of the 6 viruses were well conserved to endogenous counterpart sequences (>97.8%). However, the gp85 genes displayed high variability with any known chicken ALV strains. Growth kinetics of DF-1 cells infected with the isolated ALV showed viral titers that were lower than those infected with the GD13 (ALV-A), CD08 (ALV-B), and CHN06 (ALV-J) on day 7 post-infection. The infected Specific-pathogen-free (SPF) chickens could produce continuous viremia, atrophy of immune organs, growth retardation and no tumors were observed. These subgroup ALVs are unique and may be common in south China. The results suggested that updating the control and eradication program of exogenous ALV for yellow feather broiler breeders in south China needs to be considered because of the emergence of the new subgroup viruses., Competing Interests: The authors declare no conflict of interest.

Avian leucosis virus (ALV) is an oncogenic retrovirus that induces tumours including lymphoid leucosis and myeloid leucosis. Pleomorphic malignant mesothelioma and myelocytoma, which were thought to be induced by ALV subgroup J (ALV-J) infection, were identified in a 432-day-old broiler breeder. The bird showed no clinical signs; however, at necropsy examination there were multiple nodules in the alimentary tract. Microscopical analysis showed that these consisted of pleomorphic cells and myelocyte-like cells. Immunohistochemistry revealed that the pleomorphic cells were atypical and expressed cytokeratin, vimentin, c-kit, calretinin and ALV. The myelocyte-like cells were also positive for ALV. Retroviral type C particles were observed by electron microscopy. ALV-E and ALV-J nucleotide sequences were detected in DNA extracted from formalin-fixed and paraffin wax-embedded small intestinal tissue. Based on these results, the tumours were diagnosed as pleomorphic malignant mesothelioma and myelocytoma and were thought to have been induced by ALV-J infection. This is the first report of malignant mesothelioma associated with naturally acquired ALV-J infection., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Background: In spite of the purification of the laying hens and broilers of avian leukosis virus (ALV) has made remarkable achievements, the infection of ALV was still serious in Chinese indigenous chickens., Methods: In order to assess the epidemic state of avian leukosis virus in indigenous chickens in China, 10 novel strains of ALV subgroup J (ALV-J), named JS16JH01 to JS16JH10, were isolated and identified by virus isolation and immunofluorescence antibody assays from a Chinese local breed farm with a sporadic incidence of tumors. To understand their virological characteristics further, the proviral genome of ENV-LTR was sequenced and compared with the reference strains., Results: The homology of the gp85 gene between the ten ALV-J strains and NX0101 was in the range from 89.7-94.8% at the nuclear acid level. In addition, their gp85 genes were quite varied, with identities of 92-98% with themselves at the nuclear acid level. There were several snp and indel sites in the amino acid sequence of gp85 genes after comparison with other reference strains of ALV. Interestingly, a novel insertion in the gp85 region was found in two strains, JS16JH01 and JS16JH07, compared with NX0101 and HPRS-103., Discussion: At present, owing to the large-scale purification of ALV in China, laying hens and broiler chickens with ALV infection are rarely detected, but ALVs are still frequently detected in the local chickens, which suggests that more efforts should be applied to the purification of ALV from indigenous chickens.

Avian leukosis virus (ALV) induces multiple avian tumors, growth decrease and immune suppression. Previously, a novel natural recombinant ALV isolate FJ15HT0 was proven to be associated with significant body weight decrease, immune suppression and lymphocytoma in infected SPF chickens. In order to uncover the interaction between virus and host, we compared differences in the transcriptomes of the thymuses from the mock chickens and simulated congenitally infected chickens at 5days (d), 13d and 21d of age by RNA-seq analysis of the thymuses. Signaling pathways including cytokine-cytokine receptor interactions, peroxisome proliferator-activated receptor (PPAR) signaling pathway, Janus tyrosine kinase/signal transducers and activators of transcription (Jak-STAT) signaling pathway and fatty acid degradation were involved in the interaction between FJ15HT0 and SPF chickens. Interestingly, fold change of ciliary neurotrophic factor receptor α (CNTFRα) in infected donor collected from 2d to 21d showed a significant positive correlation with the corresponding expression of the viral gp85 gene in thymuses (r=0.656, P<0.01) and in livers (r=0.525, P<0.05). It will provide new insights for the molecular pathogenesis of ALV infection., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Background: From 2014 to 2015 in China, many broiler breeder and layer hen flocks exhibited a decrease in egg production and some chickens developed hepatitis syndrome including hepatomegaly, hepatic necrosis and hemorrhage. Avian hepatitis E virus (HEV) and avian leucosis virus subgroup J (ALV-J) both cause decreasing in egg production, hepatomegaly and hepatic hemorrhage in broiler breeder and layer hens. In the study, the seroprevalence of avian HEV and ALV-J in these flocks emerging the disease from Shandong and Shaanxi provinces were investigated., Results: A total of 1995 serum samples were collected from 14 flocks with hepatitis syndrome in Shandong and Shaanxi provinces, China. Antibodies against avian HEV and ALV-J in these serum samples were detected using iELISAs. The seroprevalence of anti-avian HEV antibodies (35.09%) was significantly higher than that of anti-ALV-J antibodies (2.16%) (p = 0.00). Moreover, the 43 serum samples positive for anti-ALV-J antibodies were all also positive for anti-avian HEV antibodies. In a comparison of both provinces, Shandong chickens exhibited a significantly higher seroprevalence of anti-avian HEV antibodies (42.16%) than Shaanxi chickens (26%) (p = 0.00). In addition, the detection of avian HEV RNA and ALV-J cDNA in the liver samples from the flocks of two provinces also showed the same results of the seroprevalence., Conclusions: In the present study, the results showed that avian HEV infection is widely prevalent and ALV-J infection is endemic in the flocks with hepatitis syndrome from Shandong and Shaanxi provinces of China. These results suggested that avian HEV infection may be the major cause of increased egg drop and hepatitis syndrome observed during the last 2 years in China. These results should be useful to guide development of prevention and control measures to control the diseases within chicken flocks in China.

Subgroup J avian leukosis virus (ALV-J) is an oncogenic retrovirus known to induce tumor formation and immunosuppression in infected chickens. One of the organs susceptible to ALV-J is the bone marrow, from which specialized antigen-presenting cells named dendritic cells (BM-DCs) are derived. Notably, these cells possess the unique ability to induce primary immune responses. In the present study, a method of cultivating and purifying DCs from chicken bone marrow in vitro was established to investigate the effects of ALV-J infection on BM-DC differentiation or generation. The results indicated that ALV-J not only infects the chicken bone marrow mononuclear cells but also appears to inhibit the differentiation and maturation of BM-DCs and to trigger apoptosis. Moreover, substantial reductions in the mRNA expression of TLR1, TLR2, TLR3, MHCI, and MHCII and in cytokine production were detected in the surviving BM-DCs following ALV-J infection. These findings indicate that ALV-J infection disrupts the process of bone marrow mononuclear cell differentiation into BM-DCs likely via altered antigen presentation, resulting in a downstream immune response in affected chickens., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The subgroup J avian leukosis virus favors the myelocytic series cells and causes myeloid leukosis (myeloblastosis and myelocytomatosis). Natural cases of myeloblastosis (myeloblastic myeloid leukosis) are uncommon and usually occur in adult chickens. This paper describes clinical signs and gross and histopathologic features of myeloblastosis in an adult female budgerigar (Melopsittacus undulatus) that was infected naturally. At necropsy, the spleen was greatly enlarged (enlarged seven or eight times normal) while the other visceral organs were normal. Histologic examination of the spleen indicated a massive intravascular and extravascular accumulation of myeloblasts with a variable proportion of promyelocytes and myelocytes in the red pulp of the spleen.

Subgroup J avian leukosis virus (ALV-J) causes a neoplastic disease in infected chickens. Differential expression patterns of microRNAs (miRNAs) are closely related to the formation and growth of tumors. (1) BACKGROUND: This study was undertaken to understand how miRNAs might be related to tumor growth during ALV-J infection. We chose to characterize the effects of miR-221 and miR-222 on cell proliferation, migration, and apoptosis based on previous microarray data. (2) METHODS: In vivo, the expression levels of miR-221 and miR-222 were significantly increased in the liver of ALV-J infected chickens (p < 0.01). Over-expression of gga-miR-221 and gga-miR-222 promoted the proliferation, migration, and growth of DF-1 cells, and decreased the expression of BCL-2 modifying factor (BMF) making cells more resistant to apoptosis. (3) RESULTS: Our results suggest that gga-miR-221 and gga-miR-222 may be tumour formation relevant gene in chicken that promote proliferation, migration, and growth of cancer cells, and inhibit apoptosis. BMF expression was significantly reduced in vivo 70 days after ALV-J infection. They may also play a pivotal role in tumorigenesis during ALV-J infection.

Epidemiological studies suggest that retroviruses, including human immunodeficiency virus type 1, are associated with cardiomyopathy and myocarditis, but a causal relationship remains to be established. We encountered unusual cardiomyocyte hypertrophy and mitosis in Japanese native fowls infected with subgroup A of the avian leukosis viruses (ALVs-A), which belong to the genus Alpharetrovirus of the family Retroviridae and mainly induce lymphoid neoplasm in chickens. The affected hearts were evaluated by histopathology and immunohistochemistry, viral isolation, viral genome sequencing and experimental infection. There was non-suppurative myocarditis in eighteen fowls and seven of them had abnormal cardiomyocytes, which were distributed predominantly in the left ventricular wall and showed hypertrophic cytoplasm and atypical large nuclei. Nuclear chains and mitosis were frequently noted in these cardiomyocytes and immunohistochemistry for proliferating cell nuclear antigen supported the enhancement of mitotic activity. ALVs were isolated from all affected cases and phylogenic analysis of envSU genes showed that the isolates were mainly classified into two different clusters, suggesting viral genome diversity. In ovo experimental infection with two of the isolates was demonstrated to cause myocarditis and cardiomyocyte hypertrophy similar to those in the naturally occurring lesions and cardiac hamartoma (rhabdomyoma) in a shorter period of time (at 70 days of age) than expected. These results indicate that ALVs cause myocarditis as well as cardiomyocyte abnormality in chickens, implying a pathogenetic mechanism different from insertional mutagenesis and the existence of retrovirus-induced heart disorder.

In this study, the efficacy of a recombinant protein vaccine encoding the gp85 gene from the subgroup J avian leukosis virus (ALV-J) co-administered with cytosine-phosphate-guanine oligodeoxynucleotide (CpG-ODN) or Freund's adjuvants was investigated for the protection against early ALV-J infection in chickens. The gp85 gene from ALV-J was amplified using polymerase chain reaction (PCR), and the recombinant protein was expressed in Escherichia coli. The purified recombinant protein was injected intramuscularly into the breeder hens along with CpG-ODN or Freund's adjuvants, and the antibodies in the serum were assayed regularly post inoculation. The fertilized eggs from the vaccinated hens were hatched, the hatched chickens were challenged with 10(2.2) 50% tissue culture infective dose (TCID50) ALV-J on 1 day, and the maternal antibodies in the hatched chickens were examined regularly before and after the challenge. The viremia was determined weekly, and a histopathological analysis of the immunosuppressive lesions was performed. The results suggest that the gp85 recombinant protein was successfully prepared and was inoculated with CpG-ODN adjuvant into breeder hens to induce serological antibody against ALV-J in the hens and in the hatched chickens. The positive maternal antibodies in the hatched chickens provided effective protection for most chickens against viremia and dramatically decreased the number of immunosuppressive lesions; these protective effects were better than those of the gp85 recombinant protein plus Freund's adjuvant. The data will provide a scientific basis for the application of the ALV-J subunit vaccine to control ALV-J infection in chicken flocks., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Avian leukosis virus (ALV) is the most common oncogenetic retrovirus that emerges spontaneously as a result of recombination between exogenous viruses, exogenous viruses and endogenous viruses, and exogenous viruses and non-homologous cellular genes. In the present study, two natural recombinant avian leukosis viruses (rALVs) (LC110515-5 and LC110803-5) carrying a subgroup C gp85 gene, a subgroup E gp37 gene, and a subgroup J 3'UTR and 3'LTR were isolated from two different lines of layer flocks, Black-bone silky fowl (BSF) and commercial layer chicken, that suffered from myeloid leukosis. Although tumours were not observed in rALV-infected individual chickens, other non-neoplastic inflammatory lesions were evident. The two rALVs were cultured on DF-1 cells and identified by PCR, immunofluorescence assay and gene sequencing. The gp85 nucleotide sequence in the two isolates displayed a high identity (>95 %) with that of the gp85 gene in ALV-C, but the identity was less than 90 % with ALV-A/B/D/E and only 51 % with ALV-J. Phylogenetic analysis of the nucleotide and amino acid sequences confirmed that the two isolates were recombinant between ALV-C, ALV-E and ALV-J. Subgroup C ALV is rarely found in field cases. This report is the first to provide evidence that ALV-C has recombined with ALV-E and ALV-J in two different chicken lines. The source and characteristics of the two rALVs and ALV-C need to be further investigated.

Background: Clinical cases of hemangioma associated with subgroup J avian leukosis virus (ALV-J) have been reported in commercial chicken layer flocks since 2006. We attempted to reproduce hemangioma through experimental infection with ALV-J to evaluate viral pathogenicity in layer birds and their progenies., Results: Body weight and indexes for immune organs of chickens infected with ALV-J strain SCDY1 were lower than those in controls. Proliferation of lymphocytes was observed in many tissues, and viral integration was detected in the genome of lymphocytes at 14 days post-infection, along with virus shedding. ALV-J was also efficiently transmitted from eggs to progenies. Embryo hatchability and progeny mortality were lower than those for controls. The efficiencies of virus shedding and virus integration in the lymphocytes of progenies were higher than those in parents., Conclusions: ALV-J is able to inhibit the growth of infected chickens, and causes damage to immune organs. Vertical transmission of ALV-J appears to be more deleterious than horizontal transmission.

Background: Emaciation, depression and lethargy were observed in two flocks of Chinese local breed and one flock of commercial layer chicken infected naturally from 2010 to 2011. The aims of this study were to diagnose., Methods and Results: Gross observation showed that severe enlargement of liver, spleen and kidney, and hemorrhage of thymus, muscle and glandular stomach in all submitted birds. The liver and lung of one flock had diffuse, multifocal white raised foci on the surface as well as on the cut-surface. Numerous erythrocytoblasts with bigger volume, basophilic cytoplasm and round nucleus were observed in blood and bone marrow smears. The same erythrocytoblasts were also found crowded in blood vessels and mesenchym of tissues by histological examination, and some had mitotic figures. PCR results showed that three flocks were positive for ALV-J with specific fragment of 924 bp, negative for AEV, ALV-A, ALV-B, Marek's disease virus (MDV) and Reticuloendotheliosis virus (REV). The results of immunohistochemistry showed that cytoplasm of histiocytes and erythrocytoblasts in lung and spleen sections was positive for ALV-J antigen., Conclusion: These data demonstrated that erythroblastosis was all induced by ALV-J in the three different flocks. This is the first document report of erythroblastosis induced by ALV-J in China flocks.

Avian leukosis virus subgroup J (ALV-J) has become pandemic and induced serious clinical outbreaks in chickens in China. In particular, ALV-J induced various clinical tumors in infected chickens, which caused enormous economic losses to poultry. In this study, an infectious clone from an epidemic ALV-J Chinese isolate designated HLJ09SH01 was constructed and rescued. The rescued virus (named rHLJ09SH01) was inoculated into specific-pathogen-free (SPF) layer chickens, and infected chickens were observed for 238 days to explore the oncogenicity of rHLJ09SH01. As a result, 57.9% of rHLJ09SH01-infected chickens produced tumors. Accumulating evidence shows that microRNAs (miRNAs) have a close relationship with tumorigenesis. To gain more insight into the tumorigenesis of ALV-J, a miRNA microarray was performed as part of an investigation of changes in host miRNA expression in a liver tumor from ALV-J infected chickens. The results showed that four miRNAs were significantly differentially expressed; these data were verified using real-time PCR. Bioinformatics analysis showed the differentially expressed miRNAs to be involved in some tumorigenesis-related signaling pathways, such as the MAPK signaling pathway and the Wnt signaling pathway, which may represent a possible signaling pathway that was involved in the ALV-J-induced tumorigenesis., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Subgroup J avian leukosis virus (ALV-J) isolate GDKP1202 was isolated from a 50-day-old local yellow commercial broiler in the Guangdong province of China in 2012. Here we report the complete genomic sequence of the GDKP1202 isolate, which caused high mortality, serious growth suppression, thymic atrophy, and liver enlargement in commercial broilers. A novel potential binding site (5'-GGCACCTCC-3') for c-myb was identified in the GDKP1202 genome. These findings will provide additional insights into the molecular characteristics in the genomes and pathogenicity of ALV-J.

Subgroup J avian leukosis virus (ALV-J) is an oncogenic retrovirus primarily causing myeloid leukosis (ML) in broilers. Although ALV is well under control in a few countries including the USA, poultry industry in many parts of the world continues suffering from serious economic loss due to sporadic or widespread ALV infection, especially ALV-J infection. ALV-J infection of chickens is reportedly mediated by a cellular receptor. So far, however, no genetic variant of the receptor gene that confers resistance to ALV-J has been identified. To advance our understanding on epigenetic factors that are involved in the event of ALV-J infection, we examined the expression of miRNAs in livers of 10-week-old chickens uninfected or infected with ALV-J by miRNA microarray analysis. Our data showed there were 12 miRNAs differentially expressed in liver between the uninfected and infected groups (P<0.01). Of which, the expressions of seven miRNAs (gga-mir-221, gga-mir-222, gga-mir-1456, gga-mir-1704, gga-mir-1777, gga-mir-1790, and gga-mir-2127,) were upregulated by ALV-J infection and may be involved in oncogenicity. The other five miRNAs (gga-let-7b, gga-let-7i, gga-mir-125b, gga-mir-375, and gga-mir-458) were significantly downregulated. The downregulated miRNAs may play important roles in tumor suppression. This finding paves the way for further exploration of epigenetic influence on tumorigenicity upon ALV-J infection., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The effects of viral-induced immunosuppression on the infectious status (viremia and antibody) and shedding of avian leukosis virus (ALV) were studied. Experimental white leghorn chickens were inoculated with ALV subgroup J (ALV-J) and infectious bursal disease virus (IBDV) at day of hatch with the ALV-J ADOL prototype strain Hcl, the Lukert strain of IBDV, or both. Appropriate groups were exposed a second time with the Lukert strain at 2 wk of age. Serum samples were collected at 2 and 4 wk of age for IBDV antibody detection. Samples for ALV-J viremia, antibody detection, and cloacal shedding were collected at 4, 10, 18, and 30 wk of age. The experiment was terminated at 30 wk of age, and birds were necropsied and examined grossly for tumor development. Neoplasias detected included hemangiomas, bile duct carcinoma, and anaplastic sarcoma of the nerve. Control birds and IBDV-infected birds were negative for ALV-J-induced viremia, antibodies, and cloacal shedding throughout experiment. By 10 wk, ALV-J-infected groups began to develop antibodies to ALV-J. However, at 18 wk the incidence of virus isolation increased in both groups, with a simultaneous decrease in antibody levels. At 30 wk, 97% of birds in the ALV-J group were virus positive and 41% were antibody positive. In the ALV-J/IDBV group, 96% of the birds were virus positive at 30 wk, and 27% had antibodies to ALV-J. In this study, infection with a mild classic strain of IBDV did not influence ALV-J infection or antibody production.

Peripheral nerve sheath tumors (PNSTs) are rare in chickens and their etiology remains to be elucidated. In this study, a naturally occurring PNST in a Japanese native fowl (Gallus gallus domesticus) was pathologically examined and the strain of avian leukosis virus (ALV) isolated from the neoplasm was characterized by molecular biological analysis. The fowl presented with a firm subcutaneous mass in the neck. The mass, connected to the adjacent spinal cord (C9-14), was microscopically composed of highly cellular tissue of spindle cells arranged in interlacing bundles, streams, and palisading patterns with Verocay bodies and less cellular tissue with abundant collagen. Immunohistochemically, neoplastic cells were divided into two types: perineurial cells positive for vimentin, glucose transporter 1 (GLUT1), and claudin1; and Schwann cells positive for vimentin, occasionally positive for S-100 alpha/beta but negative for GLUT1. Based on these findings, a diagnosis of neurofibrosarcoma was made. The complete nucleotide sequence of an ALV strain, CTS&#95;5371, isolated from the neoplasm was determined and phylogenetic analysis indicated that the strain was a novel recombinant virus from avian leukosis/sarcoma viruses previously reported. Additionally, experimental infection revealed that CTS&#95;5371 induced the proliferation of Schwann cells and perineurial cells. These results suggest that this ALV strain has the ability to induce PNSTs in chickens.

Myeloblastosis-associated virus type 1 (MAV-1) is an exogenous avian retrovirus with oncogenic potential. MAV-1 was detected in young chicks hatching from eggs produced by an experimental genetic line of egg-type chickens. Transmissibility of MAV-1 had not been documented previously. This investigation was intended to partially characterize the virus involved and to study its transmissibility and oncogenicity in naturally and contact-infected chickens. Commercially produced white and brown layer pullets free of exogenous avian leukosis viruses were commingled at hatch with naturally MAV-1-infected chickens. The original MAV-1-infected chickens were discarded after approximately 8 wk, and the contact-exposed chickens were maintained in isolation for 36 wk. Young specific-pathogen-free (SPF) single comb white leghorn chickens were added to the group to study possible horizontal transmission of MAV-1 in young chickens. Upon weekly virus isolation attempts, MAV-1 was readily isolated from the contact-exposed white layers but not from the brown layers between 36 and 53 wk of age (18 wk in total). Three-week-old SPF chickens were readily infected with MAV-1 by contact as early as 1 wk postexposure. Throughout 22 hatches derived from the white and brown MAV-1-contact-exposed layers (between 36 and 53 wk of age), MAV-1 was frequently detected in the white layer progeny, whereas the virus was seldom isolated from the progeny produced by the brown layers during the same 18-wk period. MAV-1 induced a persistent infection in some of the SPF chickens that were exposed by contact at 3 wk of age. Gross tumors were not detected in any of the originally infected experimental chickens at 8 wk of age, in the contact-exposed brown or white layers at the termination of the study at 53 wks of age, or in the contact-exposed SPF chickens at the end of the study at 12 wk of age. Exogenous avian leukosis-related viruses may still be detected in egg-type chickens, emphasizing the importance of thorough screening before incorporation of experimental genetic material into commercial genetic lines of egg-type chickens.

The present review is aimed at the non-specialist reader and is one of a number being written on important diseases of poultry to celebrate the 40th anniversary of the birth of Avian Pathology, the journal of the World Veterinary Poultry Association. The diseases of the avian leukosis complex have a number of features of distinction. They were the first neoplastic diseases in any species to be shown, 100 years ago, to be transmissible and caused by viruses, and have consequently been studied extensively by biomedical scientists as models for the role of viruses in cancer. They also became, from around the 1920s, the major cause of mortality and economic loss to the developed poultry industry, and were studied by agricultural scientists searching to understand and control them. The remit of the review is to cover research carried out over the 40 years since 1971, when the journal was founded. In this review on avian leukosis, an introductory summary is given of knowledge acquired over the preceding 60 years. Subsequently a selection is provided of discoveries, both fundamental and more applied, that seem to us to be of particular importance and interest. Much of the work was carried out by biomedical scientists interested in cancer. Probably the most significant was the discovery in the avian retroviruses of oncogenes that cause leukosis and other tumours and of their origin from proto-oncogenes in normal cells. These oncogenes are involved in cancer in many species, including chickens and humans. Other work was performed by agricultural scientists interested in poultry disease. Interests of the two groups have overlapped, particularly as a result of a shift of emphasis to molecular biology research.

Fowl glioma-inducing virus (FGV), which belongs to avian leukosis virus subgroup A, causes the so-called fowl glioma and cerebellar hypoplasia in chickens. In the present study, the complete nucleotide sequences of four isolates (Tym-43, U-1, Sp-40 and Sp-53) related to the FGV prototype were determined and their pathogenicity was investigated. Phylogenetic analysis showed that the 3'-long terminal repeat of all isolates grouped together in a cluster, while sequences of the surface (SU) proteins encoded by the env gene of these viruses had 85 to 96% identity with the corresponding region of FGV. The SU regions of Tym-43, U-1 and FGV grouped together in a cluster, but those of Sp-40 and Sp-53 formed a completely separate cluster. Next, C/O specific-pathogen-free chickens were inoculated in ovo with these isolates as well as the chimeric virus RCAS(A)-(FGVenvSU), constructed by substituting the SU region of FGV into the retroviral vector RCAS(A). The four variants induced fowl glioma and cerebellar hypoplasia and the birds inoculated with Sp-53 had the most severe lesions. In contrast, RCAS(A)-(FGVenvSU) provoked only mild non-suppurative inflammation. These results suggest that the ability to induce brain lesions similar to those of the FGV prototype is still preserved in these FGV variants.

Subgroup J avian leukosis virus (ALV-J), first isolated in 1989, predominantly causes myeloid leukosis (ML) in meat-type or egg-type chicken. Since 2006, the clinical cases of hemangioma rather than ML in commercial layer flocks associated with ALV-J have been reported, but it was still not clear whether the novel oncogenic ALV-J had emerged. We characterized SCAU-HN06 isolate of ALV-J from hemangioma in commercial Roman layers through animal experiment and full-length proviral genome sequence analysis. The SPF white leghorn egg-type chickens infected with SCAU-HN06 in ovo at day 11 of incubation showed an overall incidence of 56% hemangioma and 8% renal tumor throughout the 22-week trial, the mortality rate was 16%. Most genes of SCAU-HN06 isolate showed high nucleotide sequence identity to JS09GY6 which was isolated from Hy-Line Variety Brown layers suffering hemangioma. The 19-bp insertion in leader sequence and one key deletion in E element were the common features of SCAU-HN06 and JS09GY6. SCAU-HN06 and those ALV-Js associated with hemangioma, possibly recombinants of ALV-J and other avian retrovirus, may share the same ancestor., (Copyright © 2011 Elsevier B.V. All rights reserved.)

An outbreak of simultaneously occurring haemangiomas, leiomyosarcoma and myeloma was observed in a commercial layer flock in China. The sick chickens were extremely thin and dehydrated. Scattered haemangiomas were found on the claws, breast and wings. At necropsy, haemangiomas and some other nodular tumours were also found in the internal organs. In addition, diffuse enlargement of the liver and spleen appeared in some birds. Histopathologically, haemangiomas were typically cavernous haemangiomas and haemangioendothelioma. In the diffusely swollen liver and spleen, multifocal or widespread marrow tumour cells filled with ball-like acidophilic particles in cytosol were observed, which are the characteristic pathological changes of avian myelocytomatosis. The nodular tumour cells formed by muscle bundles were of variable size, irregular shape, poorly differentiated and malaligned. Immunohistochemistry for vimentin, cytokeratin, actin (smooth muscle) and actin (sarcomeric) and Masson's staining confirmed the different cell lineage of the nodular tumour, thus leading to the diagnosis of leiomyosarcoma. The seroprevalence of avian leukosis subgroup J (ALV-J) antibodies was 13.46% (7/52), while ALV-A/B and reticuloendotheliosis virus (REV) antibodies were not detectable. The DF-1 cells inoculated by virus extracted from liver samples from 24 infected chickens were cultured and the group-specific antigen (GSA) was identified by ELISA. All samples were positive for ALV, which was further identified as ALV-J by immunofluorescence assay (IFA). PCR analysis revealed that three isolates of ALV-J proviral sequence were close to the HPRS-103 prototype strain and other Chinese field strains isolated in recent years, while one isolate (DP01) had a lower homology with them. This is the first report that ALV-J infection caused the simultaneous occurrence of haemangiomas, leiomyosarcoma and myeloma in a commercial layer flock.

Two strains of Avian leukosis virus subgroup B (ALV-B) were isolated for the first time in China Hy-line White on the cultured DF-1 cells which were inoculated tissue samples from by an ELISA assay, a histopathology examination and a PCR-based diagnosis. The results from the ELISA assay indicated that the positive rate of serum antibodies to ALV-B and ALV-J virus were 16.3% (15/92) and 13% (12/92), respectively. The histopathological examination indicated that two types of tumor cells existed at same focus in liver and spleen, which mainly were myelocytoma cells and lymphosarcoma cells. The PCR-based diagnosis were performed as follows: the cellular DNA was extracted from the inoculated DF-1 cells; the specific fragments of 1100 bp and 924 bp were obtained by a PCR system with the diagnostic primers of ALV-B and ALV-J; and the PCR results for ALV-A, MDV and REV were all negative. Then, the amplified fragments of the two ALV-B stains were partially sequenced and shown an identity of 92.8%,94.7% with the prototype strain of ALV-B (RSV Schmidt-ruppin B). The identities of two ALV-J strains with the prototype strain HPRS-103 at 96.9%, 91.5%; The identities of two ALV-J strains with the American prototype strain at 85.9%, 81.5%. Our study had shown that ALV-B was isolated for the first time from the ALV-J infected commercial layer flocks in China. It also indicated that the chance of genetic recombination among various subgroups of ALV was increased.

A 2-year-old, male Japanese native fowl (Gallus gallus domesticus) was presented with an inability to feed and torticollis. At a necropsy, there were cylindrical enlargements and yellow discoloration of multiple peripheral nerves, including nerves of the lumbosacral plexus, brachial plexus, and spinal ganglia. On histologic examination, these lesions consisted of diffuse proliferations of spindle cells with characteristic onion bulb-like structures around residual axons. The spindle cells were immunohistochemically positive for glucose transporter 1 (GLUT1) and negative for S-100 alpha/beta proteins. On the basis of microscopic, histologic, and immunohistochemical findings, the tumors were diagnosed as multiple perineuriomas.

Fowl glioma-inducing virus (FGV), which belongs to subgroup A of avian leukosis virus (ALV), is tumorigenic in the nervous system. In a zoological garden in Japan, approximately 40% of chickens, including Japanese fowls, were infected with FGV. Because this zoological garden plays a role as a major supplier of Japanese fowl for other zoological gardens, FGV infection is suspected to have spread among ornamental chickens. In this study, the prevalence of the disease was examined in a total of 129 chickens in three other zoological gardens by nested polymerase chain reaction (PCR), reverse transcription nested PCR and enzyme-linked immunosorbent assay. Twenty-six to 56 percent of the fowls in each of the examined gardens were positive by nested PCR. The phylogenetic analysis revealed that the 3' untranslated region, including the specific sequence of FGV, of the 14 isolated ALVs showed high sequence identity and a close relationship with FGV. In addition, the env gene of the isolates frequently showed mutations and deletions of nucleotides. These results suggest that FGV is prevalent among ornamental chickens kept in zoological gardens in Japan.

Fowl glioma is characterized by multiple nodular growth of astrocytes, and fowl glioma-inducing virus belonging to avian leukosis virus has been isolated from Japanese bantam as a causal agent. Subcutaneous neoplasms of the head and neck have been reported in layer chickens since 2003 in Japan, and fowl glioma concurred in these affected layers. In the present study, the histopathology of 240 layers, including 18 layers with subcutaneous neoplasms and 222 layers kept with the affected layers, was performed to clarify the characteristics of fowl glioma in layers. Microscopically, 103 layers showed non-suppurative encephalitis, and four layers had locally extensive proliferation or multiple nodules of astrocytes. Gliomas concurred in 11 layers with subcutaneous neoplasms and occurred independently in three layers. In addition, two layers had locally extensive proliferation of small, round cells in the cerebrum. The fowl glioma-inducing virus genome was not detected in the affected brains by nested polymerase chain reaction. Ten isolates were obtained from the affected brains. By nucleotide sequencing of the env gene, SU coding regions of these isolates were most closely related to myeloblastosis-associated virus-like viruses, but TM regions showed the highest similarity to endogenous viral (ev) loci. The genome of one isolate mainly consisted of ev loci and contained several parts of other avian leukosis/sarcoma viruses. These results show that the causal avian leukosis virus of fowl glioma is not just fowl glioma-inducing virus and that different avian leukosis virus strains having oncogenicity in the central nervous system by recombination are spread in layers in Japan.

Epidemiological, pathological and molecular studies indicate that subgroup J avian leukosis virus (ALV-J) infections are widely spread in "yellow chickens" of local breeds in China. ALV-J induced tumour mortality and the serological conversion rates to ALV-J were very high in some breeder flocks. Typical myelocytomatosis was demonstrated not only in livers, spleens, kidneys, and sternums, as in white meat-type chickens, but also in thymuses and the bursa of Fabricius. Especially, severe myeloid cell infiltration was found throughout the whole enlarged thymuses of some birds. ALV-J was isolated at high positive rates from both liver tumour samples and embryos collected from breeder flocks with tumours. At the same time, reticuloendotheliosis virus was also co-isolated with ALV-J in some tumour samples and embryos. Sequence analysis of env genes demonstrated that the gp85 and gp37 among six ALV-J isolates from "yellow chickens" of Chinese local breeds varied as highly as among ALV-J strains isolated from white meat-type chickens worldwide. But strain GD0512 isolated in 2005 from a "yellow chicken" farm in southern China had high identity of 95.1% for gp85 or 99.5% for gp37 to strain HN0001 isolated in 2000 from a white meat-type breeder farm in northern China, a much higher identity than to other yellow chicken and white chicken strains. This is the first report of the isolation and identification of ALV-J from yellow chickens of Chinese local breeds and also the first report of vertical co-infection of ALV-J and reticuloendotheliosis virus. The significance of co-infection of ALV-J and reticuloendotheliosis virus in pathogenesis is discussed.

The study describes a highly productive myotropic avian leukosis virus infection (ALV) in a 3-month-old female chicken. At necropsy, ascites, hepatic fibrosis and cardiomegaly were seen. Histologically, the most striking lesion was the presence of cytoplasmic basophilic inclusions in myocardial fibers. Immunostaining for ALV group specific antigen p27 revealed a diffuse presence of virus antigen in cardiac myofibers, in smooth muscle fibers of most of the organs, and in rare, pancreatic and ovarian theca cells. Ultrastructurally, myocardial inclusions consisted of clusters of 50-60 nm round particles with interspersed ribosome-like granules. Numerous C-type particles were found in intercellular spaces of ALV p27 positive tissues. PCR analyses revealed the presence of both ALV-E and ALV-J related sequences. In chicken genome, ALV-E is usually present as endogenous provirus therefore, the pathological findings observed in this case are considered to be related with the ALV-J infection. The results of this report further confirm that ALV-J may be responsible for highly productive myotropic infections.

Among the six subgroups of Avian leukosis virus (ALV) that infect chickens, subgroup J (ALV-J) was isolated from meat-type chickens where it predominantly induces myeloid leukosis (ML) and erythroblastosis (EB). The sequence of HPRS-103, the ALV-J prototype virus, shows several distinct features, one of which is the presence of a distinct hairpin stem-loop structure called the E (also called XSR) element in the 3' untranslated region. In order to determine the role of the E element in ALV-induced pathogenicity, a comparison was made of the oncogenicity of viruses derived from the provirus clones of parental and E element-deleted HPRS-103 viruses in two genetically distinct lines of birds. In line 15I birds, deletion of the E element had profound effects on virus replication in vivo, as only 55 % of birds showed evidence of infection, compared with 100 % infection by the parental virus. Furthermore, none of the line 15I birds infected with this virus developed tumours, indicating that the E element does contribute to the oncogenicity of the virus. On the other hand, deletion of the E element had only a marginal effect on the incidence of tumours in line 0 birds. These results indicate that, although the E element per se is not absolutely essential for tumour induction by this subgroup of viruses, it does contribute to oncogenicity in certain genetic lines of chicken.

Myeloid leukosis (ML) cases were first diagnosed in a chicken flock of Chinese local breed in Shan dong province. The main symptom included wasting, weight loss, anemia. It caused about 10% mortality of about 15000 birds at the age of 120-day. In the necropsy, gray-white nodules and protrusions in various sizes were commonly observed on the surface of the sternum, intestine and trachea. Almost all viscera tissues showed moderate to severe enlargement with diffuse gray-white nodules. Histological examination indicated that the tumor cells proliferated in tissues were myelocytes with eosinophilic granules in cytoplasm. In PCR with a pair of ALV-J-specific primers, 15 of 17 liver samples were positive. PCR product of one positive sample was sequenced and demonstrated 98.05% and 97.4% identity with ALV-J HPRS-103 strain at nuclei acid and amino acids level, respectively. By immunohistochemistry (IHC) technique with ALV-J monoclonal antibody, the most intense staining was in the tumor tissue, liver, spleen, kidney, bone marrow, and proventriculus. The results indicate that ALV-J already caused chickens infection and dead in Chinese local breed.

The major organs and tissues of 24 broiler chickens (70 or 71 days old) suspected of spindle-cell proliferative disease (SPD) because of showing the tumorous lesions distributed throughout the body at meat inspection were collected for histopathological and immunohistochemical examination. Macroscopically, liver, spleen and cecal tonsil showed severe enlargement and white nodules or plaques were observed in the liver, spleen, kidney, intestine and bone marrow of the femur. All chickens were diagnosed with SPD based on the histopathological examination. The lesions of SPD were observed in the liver, spleen, kidney, heart, lung, pancreas, proventriculus, gizzard, duodenum, jejunum, ileum, rectum, cecal tonsil, bursa of Fabricius, bone marrow of the femur and skin. Hemangioma was observed in the lung of 1 bird. Eight 1-day-old specific pathogen-free chicks were inoculated intraperitoneally with 0.25 ml of a 20% homogenate of the affected spleens of three naturally occurring cases. One inoculated bird, necropsied at 10 weeks of age, macroscopically had a white nodule in the kidney and histopathologically had spindle-cell proliferative lesions, a pattern similar to that seen in the naturally occurring cases, in the liver, spleen, kidney, heart, lung, pancreas, proventriculus, duodenum, cecal tonsil and bone marrow of the femur, and was diagnosed with SPD. Immunohistochemically, significant positive reactions with a rabbit antiserum against avian leukosis virus antigens were detected in all spindle cells in the proliferative lesions of all examined SPD cases and in tumor cells of the hemangioma of a field case.

In Experiment 1, a monoclonal antibody against the envelope glycoprotein (gp85) of subgroup J avian leukosis virus (ALV-J) was used to study the distribution of ALV-J in various tissues of White Leghorn chickens inoculated as embryos with the strain ADOL-Hcl of ALV-J. At 2 and 6 wk of age, various tissues from infected and control uninfected chickens were tested for the presence of ALV-J gp85 by immunohistochemistry. In Experiment 2, using the methyl green-pyronine (MGP) stain, sections of bursa of Fabricius (BF) from chickens of line 15I5 x 7(1), inoculated with ALV-J or Rous-associated virus-1 (RAV-1), a subgroup A ALV, at hatch were examined for transformation of bursal follicles at 4 and 10 wk of age. In Experiment 1, specific staining indicative of the presence of ALV-J gp85 was noted at both 2 and 6 wk of age in the adrenal gland, bursa, gonads, heart, kidney, liver, bone marrow, nerve, pancreas, proventriculus, spleen, and thymus. In Experiment 2, by 10 wk of age, transformed bursal follicles were detected in MGP-stained sections of BF in only one of five (20%) chickens inoculated with ALV-J at hatch, compared with five of five (100%) chickens inoculated with RAV-1. The data demonstrate distribution of ALV-J gp85 in various tissues of White Leghorn chickens experimentally inoculated as embryos with the virus. The data also confirm our previous observation that ALV-J is capable of inducing transformation of bursal follicles, albeit the incidence is less frequent than that induced by subgroup A ALV.