Hypervariability in the envelope genes of subgroup J avian leukosis viruses obtained from different farms in the United States.
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 U.S. 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 fragment 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 somewhat less identical with the other nine U.S. isolates. This suggests that the envelope genes of ALV-J may have arisen as a result of a recombination event between exogenous ALV and Line 0-like sequences in the chicken. Phylogenetic analysis also showed that the U.S. field isolates were closely related to one another and more distantly related to the European HPRS-103. The pattern of mutations in the U.S. field isolates suggests that the U.S. strains are slowly drifting away from their progenitor Line 0-like sequences. The development of effective vaccines and diagnostic tests is likely to become more problematic as the viruses continue to mutate.
Silva
R F
RF
Avian Disease and Oncology Laboratory, Agricultural Research Service, U.S.D.A., East Lansing, Michigan 48823, USA. silvar@msu.edu
Fadly
A M
AM
Hunt
H D
HD
D000595:Amino Acid Sequence; D000818:Animals; D000829:Animals, Domestic / Q000821:virology*; D001354:Avian Leukosis Virus / Q000737:chemistry / Q000145:classification* / Q000235:genetics*; D002460:Cell Line; D002642:Chick Embryo; D002645:Chickens / Q000821:virology; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D005347:Fibroblasts / Q000166:cytology / Q000821:virology; D015686:Gene Products, env / Q000737:chemistry / Q000235:genetics*; D005814:Genes, Viral / Q000235:genetics*; D014644:Genetic Variation / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D011995:Recombination, Genetic / Q000235:genetics; D016415:Sequence Alignment; D014481:United States
D017931:DNA Primers; D015686:Gene Products, env