Avian Leukosis Virus
Yongxiu Yao and Venugopal Nair
from: Avian Virology: Current Research and Future Trends (Edited by: Siba K. Samal). Caister Academic Press, U.K. (2019) Pages: 231-248.
The leukosis/sarcoma (L/S) group of diseases comprise of a variety of transmissible benign and malignant neoplasms, such as lymphoid, myeloid and erythroid leukosis, caused by avian leukosis viruses (ALV), belonging to the family Retroviridae. Extensive research in the last several decades have uncovered interesting biology of these viruses and their pathogenic mechanisms. ALV are characterized by the unique possession of a reverse transcriptase enzyme that drives the generation of the DNA provirus, which is integrated into the host genome during viral replication, and induction of diseases is from insertional activation as well as transduction of oncogenes such as c-myc. ALV-associated diseases are widespread with significant economic losses resulting from tumors and subclinical infections and loss of productivity. ALVs infecting chickens belong to six envelope subgroups A, B, C, D, E (endogenous retroviruses) and J, with A, B and J subgroups the most important ones in terms of distribution and induction of diseases. While A and B subgroups are primarily associated with lymphoid leukosis, ALV-J primarily induces myeloid leukosis, currently a major problem in countries such as China. With the virus transmitted both vertically through the eggs from infected hens and horizontally, prevention of the disease is mainly by preventing the introduction of viruses and by eradication, taking advantage of the diagnostic tests to identify and disrupt the infection cycle. Genetic resistance to ALV infection has also been observed primarily based on the presence or absence of specific receptor sequences. Recent advances in genome editing offers the possibility of exploiting genetic resistance in the fight against ALV read more ...