Abstract: To investigate the infection of J subgroup avian leukosis virus (ALV-J)in local chicken breeds of Zhejiang Province, and to explore the molecular characterization of epidemic strains, infection of ALV-J was analyzed by detecting p27 antigen from samples collected from suspected infected chicken flocks of some area in Zhejiang Province. Five strains of ALV-J were isolated and GP85 genes were amplified by PCR and sequencing. Results demonstrated that ALV-J antigen positive occurred in all tested 19 lines of local chicken breeds, among of them, the positive rate of ALV p27 antigen was the highest in Line 101 and the positive rate was 40.48% in hen group, 16.54% in cock group; Line 126 took the second place, the positive rate was 28.87% in hen group, 3.30% in cock group; the positive rate was the lowest in Line171, the infection rate was 4.08% in hen group, and none was infected in cock group. Results of sequence determination and analysis demonstrated that GP85 amplified from 5 strains were all 924 bp in length, accord with the prediction; these sequences shared 90.8%-98.5% identification at nucleotide acid levels. The nucleotide similarity was 90.3%-97.0% with HPRS103, and 86.5%-99.0% with other domestic isolates. The isolates showed the highest homology with the isolates from Fujian FJ201308 strain and Guangdong WF13 strain. In conclusion, different lines of local chicken breeds in most parts of Zhejiang were infected with ALV-J to varying degrees, and the isolated strains showed different mutants to some extent, which suggested that the purification of ALV-J in Zhejiang Province should be strengthened.

Key words: avian leukemia virus, p27 antigen, GP85 gene, sequence analysis