Isolation and identification of avian leukosis virus subgroup J from Luohé Ma chicken.

Henan Province is rich in livestock and poultry resources, home to well-known local breeds, including Gushi, Lushi, and Luohé Ma chickens. These breeds are of substantial agricultural and economic importance and play a pivotal role in preserving biodiversity as well as fostering genetic innovation. Avian leukosis (AL) is a major viral disease affecting the poultry industry, with the J subgroup of avian leukosis virus (ALV-J) emerging as a significant cause of economic losses. In this study, we performed reverse transcription -polymerase chain reaction (RT-PCR) identification on chickens suspected of ALV infection based on clinical symptoms and pathological changes in the parent stock breeder farm of Luohé Ma chicken in Henan Province, and isolated the virus from the samples initially identified as positive. Indirect enzyme-linked immunosorbent assay (ELISA), indirect immunofluorescent antibody (IFA), transmission electron microscopy (TEM), and phylogenetic tree analysis were used to further determine whether ALV infection existed and its infection subtype. The results demonstrated that ALV infection did exist in the breeding farm of the Luohé chicken parents, and we successfully isolated and obtained an ALV strain, which was named HN-1. The RT-PCR results showed that only the gp85 gene sequence of the ALV-J subtype was amplified, and the nucleotide sequence was submitted to GenBank, where it was assigned the accession number PQ010741.1. Its genetic evolutionary relationship was most closely related to the ALV-J subtype strain FJ201307. In conclusion, our findings indicate the presence of ALV-J infection in this chicken farm and remind us that appropriate measures should be taken before ALV-J outbreaks to minimize economic losses.