Abstract: Avian leukosis virus （ALV） was isolated from the tumors of Chinese native breed “Luhua” chicken， and was confirmed by RT\|PCR and DNA sequencing. Then， a virus strain， named SDJN2012， was confirmed by detection of P27 antigen from the virus supernatant via inoculation of DF1 cells （C/E）. The gene of envelope protein gp85 were cloned and sequenced by designing specific primers of gp85 motif from ALV reference strains in GenBank， and the nucleotide and amino acid homologies were compared. The results showed that the SDJN2012 had the highest nucleotide （amino acid） homology 934% （926%） with SD0001 strain， the first viruses of the subtype J strains discovered in Shandong. Besides， SDJN2012 shared 886%～933% （882%～906%） nucleotide （amino acid） homologies with different subtypes of J strains， and 197%～322% （102%～322%） homologies of A， C， D， E subtypes of ALV homolog， which further confirmed that the isolated virus was J subtype ALV. The positive rate of P27 antigen was 376%. The antibodies of ALV J subtype were negative before onset， and were only 935% positive after onset. While， the positive rate of A/B subtype from climbed to 754% after onset from 98%， which indicated the complexity of ALV clinical etiology， serology and molecular epidemiology.

Key words: Avian leukosis virus, gp85 gene, J subtype