Research Progress on Pathogenesis and Prevention of Avian Leukosis Virus J Subgroup (ALV-J)

As a major retrovirus threatening global poultry farming, Avian Leukosis Virus Subgroup J (ALV-J) has expanded its host range since discovery, extending from conventional broilers to layer chickens and native breeds. Its diverse oncogenic manifestations, including myeloid leukemia, hemangiomas, and tumors of immune and visceral organs, have led to increased mortality, reduced productivity, and substantial economic losses in the poultry industry. Based on the current body of literature, this review summarizes and synthesizes advances in the etiological characteristics, infection and pathogenic mechanisms, host resistance, and research progress in prevention and control of ALV-J. Accumulating evidence indicates that viral evolution driven by mutations and recombination—particularly in the env gene and LTR regions—plays a central role in host range expansion, tumor diversity, and immune evasion. Current studies consistently demonstrate that host resistance to ALV-J is a multifactorial process involving genetic polymorphism, innate immune responses, and cellular autonomous defense systems. In this context, recent advances in disease-resistant breeding highlight CRISPR-Cas9-mediated gene editing as a promising strategy for blocking viral entry or replication. Despite these advances, major gaps remain, including an incomplete understanding of virus–host interaction networks, limited insight into co-infection-mediated synergistic pathogenicity, the absence of effective vaccines, and insufficient large-scale epidemiological surveillance and purification systems. Addressing these challenges will be critical for the development of integrated prevention strategies and the sustainable control of ALV-J in poultry production.