Characterization of cloned chicken anemia virus DNA that contains all elements for the infectious replication cycle

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Abstract
Circular double-stranded replication intermediates were identified in low-molecular-weight DNA of cells of the avian leukemia virus-induced lymphoblastoid cell line 1104-X-5 infected with chicken anemia virus (CAV). To characterize the genome of CAV, we cloned linearized CAV DNA into the vector pIC20H. Transfection of the circularized cloned insert into chicken cell lines caused a cytopathogenic effect, which was arrested when a chicken serum with neutralizing antibodies directed against CAV was added. Chickens inoculated at 1 day of age with CAV collected from cell lines transfected with cloned CAV DNA developed clinical signs of CAV. The 2,319-bp cloned CAV DNA contained all the genetic information needed for the complete replication cycle of CAV. The CAV DNA sequence has three partially overlapping major reading frames coding for putative peptides of 51.6, 24.0, and 13.6 kDa. The CAV genome probably contains only one promoter region and only one poly(A) addition signal. Southern blot analysis using oligomers derived from the CAV DNA sequence showed that infected cells contained double- and single-stranded CAV DNAs, whereas purified virus contained only the minus strand. It is the first time that the genome of one of the three known single-stranded circular DNA viruses has been completely analyzed.