ARS | Publication request: Diversity in Avian Leukosis Virus Isolates From Single Outbreak of Myelocytomatosis in Commercial Layers

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: September 20, 2009
Publication Date: N/A

Technical Abstract: In 1997, three white leghorn flocks were diagnosed with the first reported case of myelocytomatosis in commercial and field layer flocks. Moreover, the first naturally occurring recombinant avian leukosis virus (ALV) termed AF 115-4 (ALV-B/J) containing the envelope of ALV-B and long terminal repeat (LTR) of ALV-J was isolated from these flocks. Seven other isolates (AF 115-1, AF 115-5, AF 115-7, AF 115-10, AF 115-13, AF 115-14 and AF 115-16) from the same field case were shown to be similar to ALV-B/J (AF 115-4) by biological assays. PCR amplification results suggested the presence of ALV-J and ALV-B sequences in these isolates. Four isolates (AF 115-1, AF 115-13, AF 115-14 and AF 115-16) showed identical PCR amplification to ALV-B/J (AF 115-4); while the remaining three (AF 115-5, AF 115-7 and AF 115-10) were more diverse. The proviral DNA sequences of these seven isolates were compared with those of ALV-B/J (AF 115-4) and prototypes of various ALV subgroups. Sequence analysis revealed that AF 115-5 had significant amino acid differences in gp85 SU (surface) protein; while AF 115-10 had nucleotide variations in 3’ UTR (untranslated region) and LTR regions. However, TM (transmembrane) gp37 proteins of all seven isolates were identical to that of ALV-B/J. In addition, AF 115-5 was shown to be a mixture of two different recombinant ALVs (ALV-B/J and ALV-A/J). It is not known if the genomic variations and viral diversity exhibited by these isolates influence their pathogenicity. However, this will be later assessed by experimental inoculation studies in susceptible chickens.