Detection of avian leukosis virus subgroup J in albumen of commercial and native fowl eggs using RT-PCR in Fars province of Iran

The subgroup J of ALV [ALV-J] has emerged as an important pathogen of meat-type chickens since 1989. This virus is responsible for economic losses due to both mortality and depressed performance in chickens. So, the objective of this study is the detection of ALV-J in the albumen of commercial and native fowl eggs using RT-PCR. Three hundred and seventy egg albumens were randomly selected from different farms of Fars province, Iran. These eggs were obtained from the flocks of two research centers on native fowl production [70 eggs], a broiler grandparent farm [60 eggs], three broiler breeder farms [180 eggs], and a commercial layer flock [60 eggs]. RT-PCR was undertaken on isolated RNA from egg samples using a pair of ALV-J specific primers H5/H7 that produced a 545 basepair fragment. RT-PCR analyses detected ALV-J in 15 of 180 [8.33%] samples from three broiler breeders farms, 17 of 70 [24.28%] samples from flocks of two research centers of native fowls production, and none of the samples of commercial layer and broiler grandparent farms. Direct sequencing using primers specific for subgroup ALV-J verified the viral subgroup in the RT-PCR amplification products. This is the first report of the ALV-J in egg albumen in Iran which indicates the necessity to apply eradication programs for ALV-J in the poultry industry and native fowls in Iran

The effects of cyclophosphamide treatment on the pathogenesis of subgroup J avian leukosis virus (ALV-J) infection in broiler chickens with Marek's disease virus exposure

Studies were performed to determine the effects of Bcell suppression on the pathogenesis of Subgroup J avian leukosis virus (ALV-J) in broiler chickens. Neonatal chickens were treated with cyclophosphamide (CY) or PBS, and then infected with ALV-J (ADOL-7501) at 2 weeks of age. CY treatment induced B cell specific immunosuppression throughout the experiment confirmed by decreased bursal weight, intact lymphocyte mitogenetic activity stimulated by Con A and increased relative subpopulation of CD3-positive cells as measured by flow cytometry. Chickens in this experiment had Mareks disease virus exposure prior to three weeks of age as determined by the presence of lymphocytic infiltration and antibody. Virus neutralizing antibody against ALV-J was first observed at 6 weeks post-infection in some of the infected chickens in the PBS group. As expected, none of the chickens from the CY group and uninfected chickens developed virus-neutralizing antibody. The viremic status was measured by real time RT-PCR using SYBR green I dye. The percentage of viremic chickens was significantly higher, and more chickens had high titered viremia, in the CY treated group. No neoplastic foci consistent with ALVJ infection were observed in any of the experimental chickens. The frequency and intensity of viral antigen expression determined by immunohistochemistry was significantly higher in tissues from CY treated birds than those of PBS treated chickens at 3 weeks post-infection. This study showed that B cell specific immunosuppression with CY treatment in chickens resulted in increase in viremia and viral antigen load in tissues.

Effects of cyclosporin A treatment on the pathogenesis of avian leukosis virus subgroup J infection in broiler chickens with Marek's disease virus exposure

In this study, we investigated the effects of T-cell suppression on the pathogenesis of subgroup J avian leukosis virus (ALV-J). Chickens were treated with cyclosporin A (CSP) 50 mg/Kg body weight or a corresponding volume of olive oil per every three days after hatching until the end of experiment. Some of the chickens from each treatment group were infected with an isolate of ALV-J, ADOL-7501, at 2 weeks of age. The effects of viral infection were compared to uninfected birds in same treatment group. Intramuscular injection of CSP induced significant T-cell specific immunosuppression determined by decreased cutaneous basophilic hypersensitivity response and decreased lymphocyte mitogenic activity using concanavalin A. Most of the chickens examined had Marek's disease virus infection prior to 3 weeks of age. The percentage of antibody-positive birds and antibody titers were similar in infected chickens between both treatment groups. The ratio of viremic chickens was significantly higher in CSP treated group than that of the Oil treated group. Microscopically, one CSP treated chicken had a nephroblastoma at 10 weeks post infection. At 7 and 10 weeks post-infection, more chickens had myeloid cell infiltrations in multiple organs including heart, liver and occasionally lung. Expression of ALV-J viral antigen determined by immunohistochemical staining was significantly higher in CSP treated chickens than Oil treated chickens at 10 weeks post-infection. This study indicated that chemically-induced T-cell suppression may enhance pathogenicity of the AVL-J virus in broilers.