Objective   To investigate the genomic structural characteristics of TT viruses isolated from China and their prevalence in patients with different types of viral hepatits.

  Methods   The phylogenetic tree analysis of complete sequence of 49 TTV-related viruses to compare the genomic structural characteristics of 3 Chinese TTV isolated with TTV prototype strain(TA278)and other TTV-related viruses.The nested polymerase chain reaction(nPCR)was used for detection of TTV DNA in sera of patients with different types of viral hepatitis.

  Results   The complete genome of 3 Chinese TTV isolated comprised of 3739 nucleotides with two open reading frames(ORFs).The ORF1 was located at 589-2901nt, encoding 770 amino acids, and the ORF2 at 107-715nt, encoding 202 amino acids.5.and 3.terminals of the genome were non-coding regions including 106 bp and 838 bp, respectiv ely.The nucleotide homology between the 3 Chinese isolated and TTV prototype strain(TA278)was 86%-96% in the complete nucleotides, 88%-97% and 79%-96% in ORF1 and ORF2 at the amino acid level, respectively.Phylogenetic tree analysis showed that 3 Chinese TTV isolated could be considered as a member of TTV prototype group.Of 180 patients with different types of viral hepatitis, 40(22.2%)were TTV DNA positive.The TTV DNA prevalence rates were 24.2% (29/120), 18.3% (11/60), 17.8% (106/595), 19.8% (19/96)in patients with hepatitis A to E, non-A to E hepatits, chronic hepatitis B and normal population.There were no differences between these four groups.

  Conclusion   Genomic structural characteristics of 3 Chinese TTV isolated were simlar to that of the TTV prototype strain(TA 278).The TTV DNA prevalence rates of patients with different types of viral hepatits, chronic hepatitis Band normal population were relatively high.