Abstract:

The objective of the study is to explore co-infection of reticuloendothelial hyperplasia virus (REV) and avian leukemia virus (ALV) inWannan yellow feather broilers. In addition, the sequence variations in the envelope glycoprotein gene (env) and the 3′UTR and the 5′LTR non-coding sequences of ALV-J collected in the last decade were analyzed. Seven 300-d old chickens suffering from neoplastic diseases were subjected to histopathology examination. Cell cultures were established for viral detection and quantification using PCR and IFA. The result showed that 6 of the 7 animals were co-infected with both viruses, while ALV-A and ALV-B were not detected. Furthermore, both viruses were detected in the same liver cells. Sequence analysis showed that the full-length of the env gene and the 3′UTR region were 1 704 bp and 400 bp, respectively, and both the rTM and the E elements in the 3′UTR region were deleted. Sequence comparison showed that the deletion of the 3′UTR-E element of ALV-J from Wannan yellow-feather broilers is also shared among the ALV-J isolates collected by the authors from the white-feather broilers in the past decade, whereas the deletion of the 3′UTR-rTM element was variable. The 5′LTR conserved sequence had an 11 bp deletion compared to the previously analyzed strains. The remarkably high frequency (6/7) of REV and ALV-J co-infection in association with the high tumor occurrence in Wannan yellow-feather chickens suggest that such co-infection may be an important contributing factor for the tumor epidemic. The fact that the deletion in the 3′UTR-E element is shared by the ALV-J isolates from both Wannan yellow-feather broilers and the white-feather broilers indicates that these ALV-J isolates are of a common origin.

Key words: Wannan Yellow feather broilers, ALV-J, co-infection status, genetic variation