Genomic and evolutionary characterization of TT virus (TTV) in tupaias andcomparison with species-specific TTVs in humans and non-human primates

TT virus (TTV) was recovered from the sera of tupaias (Tupaia belangeri chi nensis) by PCR using primers derived from the noncoding region of the human TTV genome, and its entire genomic sequence was determined. One tupaia T-T V isolate (Tbc-TTV1 4) consisted of only 2199 nucleotides (nt) and had thre e open reading frames (ORFs), spanning 1506 nt (ORF1), 177 nt (ORF2) and 64 2 nt (ORF3), which were in the same orientation as the ORFs of the human pr ototype TTV (TA278). ORF3 was presumed to arise from a splicing of TTV mRNA , similar to reported human TTVs whose spliced mRNAs have been identified, and encoded a joint protein of 214 amino acids with a Ser-, Lys- and Arg-ri ch sequence at the C terminus. Tbc-TTV 14 was less than 50% similar to prev iously reported TTVs of 3.4-3.9 kb and TTV-like mini viruses (TLMVs) of 2.8 -3.0 kb isolated from humans and non-human primates, and known animal circo viruses. Although Tbc-TTV1 4 has a genomic length similar to animal circovi ruses (1.8-2.3 kb), Tbc-TTV1 4 resembled TTVs and TLMVs with regard to puta tive genomic organization and transcription profile. Conserved motifs were commonly observed in the coding and noncoding regions of the Tbc-TTV 14 gen ome and in all TTV and TLMV genomes. Phylogenetic analysis revealed that Tb c-TTV1 4 is the closest to TLMVs, and is closer to TTVs isolated from tamar in and douroucouli than to TTVs isolated from humans and chimpanzees. These results indicate that tupaias are naturally infected with a new TTV specie s that has not been identified among primates.