Genoepidemiology of TT virus infection in hepatitis B virus carriers with high sensitivity PCR

Abstract

We employed a PCR assay system TaKaRa Ex Taq™ (heat-resistant DNA polymerase), which has 3′→5′ exonuclease activity to increase the sensitivity for TT virus (TTV) DNA detection. Sera obtained from 95 hepatitis B virus carriers without hepatitis C virus coinfection were tested for TTV DNA and the sensitivity of this assay system was compared with the PCR systems reported previously. Of the 95 individuals, TTV DNA was identified in 14 (14.7%) with the PCR reported by Nishizawa et al., in 66 (69.5%) with the PCR reported by Okamoto et al., in 80 (84.2%) by our assay system, and in 86 (90.5%) with the PCR reported by Takahashi et al. Phylogenetic analysis of nucleotide sequences amplified by the PCR revealed that genotypes 1a, 1b, 2, 3, 4, 5 were amplified efficiently by our assay system, while only a part of TTV DNA clone of genotype 1a was amplified by the PCR reported by Nishizawa et al. The prevalence of circulating TTV DNA became higher with age. These results indicate that our assay system with TaKaRa Ex Taq™ has confirmed high prevalence of TTV infection and that at least five genotypes prevail in Japan. In addition, acute TTV infection is supposed to cause long-standing viremia.