| College of Animal Science and Veterinary Medicine,Shandong Agricultural University, Taian,Shandong , 271018, China Abstract:Avian leukosis virus Subgroup J (ALV-J) is a retrovirus that infects meat-type chickens. ALV-J was first reported as a new subgroup of ALV by Payne in 1991. It induced avian myelcytomatosis (ML) in broiler. ALV-J was isolated and identified in 1999 from two broiler breeder farms with suspected lesions and 2 of 25 commercial broiler flocks by Prof. Cui ZhiZHong's laboratory in China. Subsequently, more strains of ALV-J were identified in different lines of broiler. 2 strains of ALV-J were isolated from broiler breeder (BB) flocks experiencing clinical symptoms of myeloid leukosis (ML) at 28 wk of age and 38wk of age. The isolates were named as YT0201 and YT0202, they have the ability of propagation in chicken embryo fibroblasts (CEF) from SPF chickens. Positive reaction in a polymerase chain reaction with primers specific for ALV-J, and they showed positive reaction on examination by fluoroscope in the indirect fluorescence antibody assay(IFA) with ALV-J specific monoclonal antibody JE9, These results indicate the isolation from these meat-type chickens flocks were ALV-J.The effect of an artificial infection with a China isolate(NX0101 strain) of avian leukosis virus subgroup J (ALV-J) on the growth of commercialbroiler chickens was analysed. During this study, possible immune suppressive effects of ALV-J were assessed by measuring on indexes of immune organs to body weight, and humoral immune response against Newcastle and infectious bursal disease vaccine viruses. Three experiments were conducted. In experiment 1, Negative control chickens uninfected ALV-J were compared with ALV-J-injected chickens in ovo at 11 day and chickens ALV-J injected by hyodermic at 1 day age. In experiment 2, Negative control chickens uninfected ALV-J were compared with chickens were only injected with ALV-J and another group chikens were co-infected with ALV-J and REV by hyodermic at 1 day age. In experiment 3, 275 1-day-age chikens were devided randomly into 5 groups. Group 1: infected with ALV-J NX0101 strain; Group 2: co-infected with ALV-J NX0101 strain and REV SD9901 strain; Group 3: infected with REV SD9901 strain; Group 4: infected with REV HA9901 strain; Group 5: uninfected as control.In experiment 1, Chickens were injected in ovo at day 7 of incubation with 10-3.46 median tissue culture infectious dose (TCID50) ALV-J NX0101 strain or ALV-J injection by hyodermic at 1 day age, Significant growth suppression compared with Negative control chickens was found, . atrophy in the bursa and thymus was detected, at the same time, indexes of immune organs to body weight showed a tendency to a lower response in ALV-J-infected birds. In addition, antibody reaction to Newcastle disease virus vaccines was inhibited, hile compared to the control birds (P<0.05). otherwise ALV-J infection gave no influence on reaction to IBDV vaccination in birds.In experiment 2, when 1-day-old broilers were infected with avian leukosis virus of subgroup J (ALV-J) strain NX0101,the body weight was significantly reduced, atrophy in the bursa and thymus was detected, and antibody reaction to Newcastle disease virus vaccines was inhibited, while compared to the control birds (P<0.05). such phenomen were even moreserious when birds were co-infected with ALV-J strain NX0101 and 103.01 TCID50 Reticuloendotheliosis virus (REV) strain SD9901, compared to controls (P<0.01) or to birds infected with ALV-J alone (P<0.05).ALV-J infection alone gave no influence on reaction to IBDV vaccination in birds, but co-infection of ALV-J and REV apparently delayed antibody reactions to IBDV. This is the first report to demonstrate the immunosuppression of ALV-J infection on broilers especially when co-infected with REV.In experiment 3, the occurrence of Avian Infectious Bronchitis (IB) in REV HA9901 strain group at 12 days age. Other three groups except the control were showed similar clinical symptoms in th... |
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