| Avian leukosis is a variety of tissues and organs tumor disease caused by avian leukosis virus (ALV). Besides tumorigenic death, the greatest harm of ALV is subclinical symptoms, including immune suppression, production performance decrease and so on. ALV has a capacity of vertical and horizontal transmission; the population cleaning is the most effective way to prevent it by now. In recent years, the infection of subgroup J ALV (ALV-J) which has high pathogenicity in Chinese layer flocks is serious, subgroup A (ALV-A) and subgroup B ALV (ALV-B) are also infect seriously. Therefore, it is necessary to establish a method for ALV detection, and carry out a molecular epidemiological investigation of ALV infection in layer flocks inChina.In the first study, the most sensitive and specific monoclonal antibody (MAb)4C7against for ALV p27antigen was screened from5MAbs, then an indirect immunofluorescence assay (IFA) method for ALV detection was established with it. The results showed that the IFA method had good specificity for subgroup A, B and J ALV detection, and no cross-reactivity with other poultry oncogenic viruses (REV and MDV). It also had high sensitivity; DF1cells infected with10TCID50ALV can be detected24hours later. The minimum amount of virus detection of this method was1TCID50when DF1cells infected with ALV5days later.In the second study,15strains of ALV include3strains of ALV-A,4strains of ALV-B,8strains of ALV-J were isolated from layer flocks in China, gp85nucleotide sequence homology displayed. Phylogenetic analysis of gp85gene of ALV isolates showed that the genetic variation of ALV-A and ALV-B in Chinese layer flocks were relatively stable, which had a high homology with their prototype strains. But ALV-J mutated greatly, the genetic relationship with the prototype strain HPRS-103were distant, also distantly related to the isolates from Chinese layer flocks in recent years, but closed to ADOL-Hc1, ADOL-7501isolated from early United States and broiler isolates in early china (1999to2003). ALV-J isolates WX-J1216and JS-J1210were closely related to SCAU11-H isolated from white meat-type breeder in China in2011. These findings suggest that ALV-J in Chinese layer flocks in recent years might be derived from the early broiler isolates.4ALV-J isolates (SQ-J1211, CZ-J1212, WX-J1214, WX-J1215) had high degree of genetic relationship with the strain HR332isolated from HR local layer chicken in China, indicating that the scope infection of ALV-J is still expanding now. |
