Genomic and molecular evolutionary analysis of a newly identified infectious agent (SEN virus) and its relationship to the TT virus family

A new group of transmissible single-stranded (ss) DNA viruses (SENV) distan tly related to the large TT virus (TTV) family was recently identified. Eig ht different SENV isolates have been found, some with an association with p osttransfusion hepatitis. A phylogenetic analysis of near-complete open-rea ding frame 1, including conserved motifs and excluding recombinant regions, was performed. The analysis used TTV-like minivirus as an outgroup, to det ermine a root of the phylogenetic tree, and compared 8 SENV isolates, 6 pro totype TTV isolates, and 7 TTV variants (including SANBAN, TUS01, PMV, and YONBAN). Four distinct clusters separated by a bootstrap value of 100% were observed. YONBAN isolates formed a distinct outer group, representing the earliest recognized phylogenetic divergence (group 1). Prototype TTV formed group 2, PMV formed group 3, and SENV, SANBAN, and TUS01 isolates formed g roup 4, the most recently evolved group. This taxonomic classification sugg ests that these circular ssDNA viruses probably evolved from a common ances tor virus.