PARTIAL SIMILAR-TO-2.4-KB SEQUENCES OF TT-VIRUS (TTV) GENOME FROM 8 JAPANESE ISOLATES - DIAGNOSTIC AND PHYLOGENETIC IMPLICATIONS

Recently, a new single-stranded DNA virus, TT virus (TTV), was molecul arly cloned from a patient with posttransfusion hepatitis of unknown e tiology, and its causal relationship to non-A-G hepatitis is being inv estigated. However, the only method to diagnose TTV infection has been polymerase chain reaction (PCR) on the basis of very limited informat ion on its genome. To improve diagnostic efficiency as well as to unde rstand better the genetic characteristics of TTV, we determined a part ial similar to 2.4-kb sequence of the TTV genome from eight Japanese i solates. The sequenced region covered a long open reading frame (ORF-L ) coding for a protein of 768-770 amino acids, which was highly argini ne-rich in its N-terminus and had three or four asparagine-linked glyc osylation sites clustered in its central portion. Our eight sequences and the prototype TTV sequence (TA278) taken together, these Japanese isolates of TTV were classified under two distinct genotypes. Using PC R primers designed on the observed heterogeneity among separate isolat es, we identified an extreme variant whose nucleotide similarity to ot her isolates was only about 65%. Comparison of the ORF-L-encoded prote in of TTV with those of known single-stranded DNA viruses suggested a possibility that TTV might be related to chicken anemia virus belongin g to the Circoviridae family rather than to the Parvoviridae. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.