Characteristics And Transcriptomics Analysis Of Avian Leukosis Virus Subgroup J Infection

Avian leukosis is a kind of tumorigenic infectious disease which is caused by avian leukosis virus (ALV). Avian leukosis can cause series of clinical syndromes including lymphoblastic leukemia, erthroblastosis, myeloid leukemia, hemangioma, nephroma, sarcoma and osteopetrosis. Additionally, ALV can cause the decrease in body weight or egg production, and immunosuppression in ALV-infected chicken flocks. The virus can be divided into six subgroups, through A to E and J. Subgroup E is the endogenous ALV, and other subgroups ALV are exogenous. In1988, Subgroup J ALV (ALV-J) was first reported in meat chickens in UK, then it was rapidly spread to other countries and caused serious economic losses. In China’s mainland, ALV-J was firstly isolated from broiler chicken in1999. Currently, ALV-J is commonly infected in Chinese chicken flocks, and the ocurance of ALV-J related tumor clinical cases was incresing. Thus, research on the pathogenicity of Chinese specific ALV-J strains would make us better understand the pathogenic mechanism of ALV. This study observed the variation of antigens and antibodies in ALV-J (JS09GY3) infected chickens, and the clinical symptoms and histopathology and tumor types, also analyzed the gene transcripts of bursa using gene expression profile microarray. The findings of this study would provide new insights for a better understanding the pathogenic mechanism of ALV-J.1. Variation of antigen and antibodies in different age chickens infected with ALV-J strain JS09GY3To observe the variation of antigen and antibody of ALV-J infected chickens, specific pathogen free (SPF) white leghorn chicken embryos were infected with ALV-J (JS09GY3) at the sixth day of embryonation by yolk sac and infected SPF chickens with ALV-J (JS09GY3) at31st and56th day old by intramuscular injection. Then, we detected p27antigen and antibodies to ALV-J at different days. The results showed that p27antigen was positive in embryo infection group during all tested time points except one chicken at the1day old. It was interesting that p27 antigen was negative in other two groups (31th and56th day infection) in all time. The p27antibody was negative in embryo group in all time. However, p27antibody was positive for most chickens (4/5) in31day old group after three superinfection and most chickens (6/10) positive in56-day old group after first infection. ALV-J antibody in three tested groups was negative except one chicken. Theses results suggested that chickens infected with ALV-J strain JS09GY3at embryo period could produce virus, but no antibodies against p27antigen and gp85protein. And, chickens infected with ALV-J at31and56days old could not produce virus, however, after recurrent infection, almost no chickens could produce antibodies against gp85protein, but most chickens could produce antibodies against p27antigen.2. Comparison of different methods for early detection of subgroup J avian leukosisAvian leukosis is a kind of important viral tumorigenic diseases which threats a lot to poultry industry. On the early stage of ALV infection, fast and accurate diagnosis is great important for the eradication of avian leukosis. This study compared PCR method, virus isolation and histopathology for the detection of avian leukosis at different time points of20SPF chickens infected with ALV-J JS09GY3strain via yolk sac at sixth embryo-day. The results showed that total positive rate of virus isolation was65%or75%in ELISA or IFA for ALV-J. The positive rate of PCR for ALV-J was95%. The histopathology analysis results showed that two ALV-J infected chickens had macroscopic lesions on the liver; several ALV-J infected chickens had microscopic lesions on the liver, kidney, heart and lung. However, there was no lesion on the spleen. These findings suggested that three diagnosis methods (PCR, virus isolation and histopathology) had different result in the early diagnosis of avian leukosis. PCR method showed a high positive rate which may be important in early diagnosis of avian leukosis.3. Characteristic of ALV-J strain JS09GY3infection in SPF chickensTo explore the characteristic of ALV-J strain JS09GY3infection, SPF white leghorn chicken embryos at sixth embryo-day was infected with ALV-J strain JS09GY3via yolk sac to stimulate the vertical transmission of ALV. From1day-old to20weeks-age, clinical signs and pathology changes at macro or microscopy were observed. The p27antigens in cloaca, antibodies against p27antigen and gp85protein in sera were detected and virus in blood was isolated. The results showed that ALV-J strain JS09GY3could cause chickens died and growth retuning, particularly at8-12weeks-ages (p<0.05); Total rate of tumor was72.22%. Tumor emerged after4weeks-age, and more and more tumors could be found with the increasing of age. Haemangioma was main kind of tumor in pathology changes and have58.33%of incidence rate in whole trial. Except haemangioma, adenoccarcinoma of ovary and muscle fibroma were observed in tissue sections. p27antigen in cloaca could be detected and virus could be isolated from blood; The antibodies against gp85protein of ALV-J were not detected, while antibodies against p27antigen could be detected in partial chickens at16and20weeks-age. These findings suggested that ALV-J strain JS09GY3was high pathogenicity and might be used for the development of living model of ALV-J infection.4. Transcription analysis of the response of chicken bursa of Fabricius to ALV-J strain JS09GY3ALV-J causes tumor, immunosuppression and result in high susceptibility to other infectious agents with high morbidity and mortality in chickens. However, the systematical response of chickens to ALV infection remains unknown. In this study, gene expression profiling response induced by ALV-J strain JS09GY3in chickens was investigated. A total of594gene transcripts showing differential expression (DE) after infection were identified comparing with the controls (Fold change≥2, p<0.05). The DE genes were associated with many important functions, mainly including cellular process, binding, biological regulation, metabolic process, response to stimulus and immune system process. Further analysis showed those genes were majorly involved in notable signaling pathway like cytokine-cytokine receptor interaction, JAK-STAT signaling pathway, RIG-I-like receptor signaling pathway, etc. These differentially expressed genes were mainly distributed in chr1、 chrUn_random、 chr2、chr4、chr7, etc. After analysing interaction network of these DE genes encoding proteins with String9.1, the interactions existed between many proteins. This study showed an outline of gene profile in host response to ALV-J infection in chickens. The gene expression profile could provide us a better understand the molecular pathogenesis of ALV-J infection in chickens.