TT virus infection in healthy children and in children with chronic hepatitis B or C

Background: The existence of a novel human virus, designated TT virus (TTV), has been reported in association with acute and chronic liver disease of unknown cause. Objectives: To evaluate the prevalence and clinical significance of TTV infection in childhood. Study design: Sera from 104 healthy children, 85 patients with chronic hepatitis B (HBV) and 29 with chronic hepatitis C (HCV), were tested by polymerase chain reaction with primers corresponding to conserved regions within a part of ORF 2. To characterize polymerase chain reaction products, TTV isolates from 15 subjects were directly sequenced. Results: TTV DNA was detected in 22 (21%) of 104 healthy children and in 55 (65%) of 85 and 20 (69%) of 29 HBV- and HCV-infected individuals, respectively. No significant difference was observed in aminotransferase levels of HBV- or HCV-infected patients with or without TTV coinfection. Sequence analysis showed a high degree of genetic heterogeneity between TTV isolates. Conclusions: A striking difference was found in the prevalence of TTV between healthy children and patients with chronic HBV or HCV infection (P < .0005). However, based on these results, TTV alone or as coinfection does not seem to cause or exacerbate liver damage in childhood.