TT virus infection during childhood.

BACKGROUND: TT virus (TTV) is widespread in the general population, however, the mode of its transmission and the mechanism of maintaining it in the general population are unclear. STUDY DESIGN AND METHODS: To determine the possible mother-to-infant route of transmission, 54 infants born to 50 anti-HCV-positive mothers were assessed longitudinally. Nucleotide sequences amplified by seminested PCR with primers targeting the N22 variable coding region of genotypes 1 through 6 were compared in mothers and their infants. RESULTS: The prevalence of TTV DNA was 30 percent (15/50; 95% CI, 18-45) in mothers and 44 percent (24/54; 95% CI, 31-59) in their infants. TTV DNA was detected during a follow-up period in 13 (87%; 95% CI, 60–98) of 15 infants born to infected mothers and in 11 (28%; 95% CI, 15-45) of 39 infants born to DNA-negative mothers. None of 38 cord blood samples, but one of 14 blood samples, obtained at 1 month of age had detectable TTV DNA. The lowest infection rate at the earliest ages and the subsequent increasing prevalence of infection (22% at 6 months and 33%[43% cumulative rate] at 2 years) is consistent with an age-dependent acquisition of TTV by nonparenteral routes. In 13–mother-infant pairs positive for TTV DNA, six showed a high degree of nucleotide sequence similarity (99.1-100%), whereas the remaining seven pairs differed more than 10 percent from each other (46.8-89.2%). The viral load of maternal blood was not a plausible risk factor for transmission. Genotype 1, of which pathogenicity failed to be shown by measurement of hepatic enzymes, was more rapidly cleared (88 vs. 8% other genotypes, p < 0.001) among infants. CONCLUSIONS: These observations strongly suggest that the main factor for TTV acquisition in children involves their age-associated increase in environmental interactions with infectious materials. Genotype 1 might be involved in a weak or a limited pathologic role, which can possibly be diluted by other harmless genotypes.