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United States Department of Agriculture

Agricultural Research Service

Title: Hypervariability in the Envelope Genes of Subgroup J Avian Leukosis Viruses Obtained from Different Farms in the United States

Authors
item Silva, Robert
item Fadly, Aly
item Hunt, Henry

Submitted to: Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 6, 2000
Publication Date: N/A

Interpretive Summary: Subgroup J avian leukosis virus (ALV-J) is an emerging economically important virus infection that can cause cancer-like disease and other production problems in meat-type chickens. The virus was first reported in 1991 in the United Kingdom and in 1993 in the United States. Previous observations suggest that the virus is mutating at a higher rate, however, information regarding the relationship between ALV-J isolated from various flocks and at various times is not known. Understanding the molecular structure and relationships among strains of ALV-J is an important component of any effort to develop specific diagnostics and effective control programs. Our data show that the molecular structure of ALV-J isolates from flocks in the U.S. are changing over time and that such strains have evolved independently from the ALV-J in the United Kingdom. This new information is significant and should be useful to scientists who are studying the basic principals of mutation and transmission of this emerging virus; the information should also be useful to manufacturers of ALV-J vaccines and diagnostic kits.

Technical Abstract: Avian leukosis virus, subgroup J (ALV-J), has a wide host range, preferentially infecting meat type birds and produces a high incidence of myelocytomatosis and nephromas. Using the published sequences from HPRS-103 (ALV-J isolated in 1989 in Great Britain), we designed a set of PCR primers that amplified proviral DNA from nine US field samples. The primers were specific for ALV-J, not amplifying DNA from uninfected cells or cells infected with ALV subgroups A-E. These primers expanded a 2.4 kb fragment that encompasses gp85, gp37, the E element and most of the 3' LTR. We also developed a set of PCR primers that amplified a 2.1 kb from ALV-J infected cells and a 1.6 kb fragment from uninfected ev- chicken embryo fibroblasts (Line 0). Upon cloning and DNA sequencing, we determined that the 2.1 and 1.6 kb fragments contained ALV-J gp85- and gp37-like sequences. Comparison of the amino acid sequences demonstrated that the Line 0 sequences were 97.5% identical with the gp85 and gp37 of HPRS-103, and some what less identical with the other nine US isolates. This suggests that the envelope genes of ALV-J may have risen as a result of a recombination event between exogenous ALV and Line 0-like sequences in the chicken. Phylogenetic analysis also showed that the US field isolates were closely related to each other and more distantly related to the European

Last Modified: 4/23/2014
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