Avian Leukosis: Will We Be Able to Get Rid of It?

Abstract

Avian leukosis viruses (ALVs) have been virtually eradicated from commercial poultry. However, some niches remain as pockets from which this group of viruses may reemerge and induce economic losses. Such is the case of fancy, hobby, backyard chickens and indigenous or native breeds, which are not as strictly inspected as commercial poultry and which have been found to harbor ALVs. In addition, the genome of both poultry and of several gamebird species contain endogenous retroviral sequences. Circumstances that support keeping up surveillance include the detection of several ALV natural recombinants between exogenous and endogenous ALV-related sequences which, combined with the well-known ability of retroviruses to mutate, facilitate the emergence of escape mutants. The subgroup most prevalent nowadays, ALV-J, has emerged as a multi-recombinant which uses a different receptor from the previously known subgroups, greatly increasing its cell tropism and pathogenicity and making it more transmissible. In this review we describe the ALVs, their different subgroups and which receptor they use to infect the cell, their routes of transmission and their presence in different bird collectivities, and the immune response against them. We analyze the different systems to control them, from vaccination to the progress made editing the bird genome to generate mutated ALV receptors or selecting certain haplotypes.

Immunoinformatics, molecular docking and dynamics simulation approaches unveil a multi epitope-based potent peptide vaccine candidate against avian leukosis virus

“…The most common avian retrovirus that causes a variety of neoplastic diseases in chicken is the avian leukosis virus (ALV) 2 . Globally, the ALV morbidity and mortality rates contributed to the poultry industry’s economic decline 1 , 3 .…”

“…Avian leukosis virus (ALV) is one of the most prevalent retroviruses causing neoplasms in chickens 1 , 2 . ALV related to the genus Alpharetrovirus and subfamily Orthoretrovirinae 3 .…”

Comparison of Endogenous Alpharetroviruses (ALV-like) across Galliform Species: New Distant Proviruses

“…Avian Leukosis Virus (ALV) is a globally distributed pathogen that mainly affects chickens, causing oncogenesis and immunosuppression in a fraction of infected individuals as well as a decrease in several productivity indicators [ 1 , 2 ]. ALV is an Alpharetrovirus ; as such, infection is permanent among individuals and easily transmitted, especially in industrial poultry settings where chickens may be crowded.…”

“…The LTR has three regions: U3 contains enhancer elements and the promoter; R is where transcription starts; and U5 contains post-translation regulatory elements [ 2 ]. LTRs and env are the major pathogenic determinants in retroviruses, including Alpharetrovirus , with relevance in the replication cycle and in tropism [ 7 , 8 , 9 ].…”

“…ALV-J was first described in the early 1990s and expanded worldwide. ALV-K was first described in 2012 in China as an emerging subgroup and is mainly isolated in the poultry of this country, though it also occurs sporadically in other parts of the world (reviewed in [ 2 ]). ALV-E is an endogenous subgroup widely distributed in the chicken ( Gallus gallus ) genome (reviewed in [ 2 ]).…”