title: TT virus infection during childhood.
abstract: 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.
  
  
  METHODS
  To determine the possible mother-to-infant route of transmission, 54 infants bom 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 bom 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 matemal 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.
authors.affiliation: Division of Blood Transfusion and Transplantation Immunology, Fukushima Medical University School of Medicine, Fukushima City, Japan. hit-ohto@fmu.ac.jp
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Ohto
authors.forename: Niro
authors.initials: N
authors.lastname: Ujiie
authors.forename: Chikako
authors.initials: C
authors.lastname: Takeuchi
authors.forename: Akira
authors.initials: A
authors.lastname: Sato
authors.forename: Akio
authors.initials: A
authors.lastname: Hayashi
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Ishiko
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Nishizawa
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Okamoto
mesh_terms: D000328:Adult; D002675:Child, Preschool; D015897:Comorbidity; D004266:DNA Virus Infections / Q000150:complications / Q000453:epidemiology / Q000635:transmission*; D004279:DNA, Viral / Q000097:blood / Q000235:genetics; D005260:Female; D005838:Genotype; D016174:Hepacivirus / Q000235:genetics; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D018445:Infectious Disease Transmission, Vertical / Q000706:statistics & numerical data*; D008107:Liver Diseases / Q000821:virology; D008297:Male; D009035:Mothers; D011247:Pregnancy; D012367:RNA, Viral / Q000097:blood; D017422:Sequence Analysis, DNA; D016036:Seroepidemiologic Studies; D022783:Torque teno virus / Q000235:genetics; D019562:Viral Load / Q000639:trends
chemical_list: D004279:DNA, Viral; D012367:RNA, Viral