The entire nucleotide sequence of a TT virus isolate from the United States (TUS01): comparison with reported isolates and phylogenetic analysis.

A nonenveloped and single-stranded DNA virus designated TT virus (TTV) has been reported from Japan in association with hepatitis of unknown etiology. Very recently, the prototype TTV isolate (TA278) of genotype 1 is proven to have a circular genome with 3852 nucleotides. A TTV isolate (TUS01) was recovered from a blood donor in the United States, and its entire circular nucleotide sequence of 3818 nucleotides was determined. It possessed two open reading frames coding for 761 and 156 amino acids, respectively. TUS01 shared 60.5% of the nucleotide sequence with the TA278 isolate from Japan that was longer by 35 nt. The sequence of the noncoding region of 1203 nt was conserved with a similarity of 83.4%. Sequence preservation was much lower for the two open reading frames; nucleotide and amino acid sequences were 54.8 and 37.0% similar, respectively, for one and 55.5 and 38.8% similar for the other. By comparison of a partial sequence of 222 nucleotides among 239 TTV isolates available from various countries, at least 11 genotypes with sequence divergence of >30% were recognized. TUS01 was deduced to be of genotype 11, which has not been reported before. Conserved sequences in the noncoding region could be used as primers for sensitively detecting TTV DNA by polymerase chain reaction. Divergent sequences in coding regions would be useful as primers for distinguishing various TTV genotypes. Copyright 1999 Academic Press.