Prevalence of TT virus in healthy children and thalassemic pediatric and young adult patients.

Background: The recently discovered TT virus (TTV) has been shown to be highly prevalent in patients with cryptogenetic chronic liver disease and fulminant hepatitis. To study the frequency of TTV and to evaluate the possible association with liver disease, 37 pediatric and young adult patients with thalassemia, and 36 healthy children were included in the study. The sera of 100 blood donors selected randomly in the same period were also tested for TTV DNA.

Methods: The TTV amplification by polymerase chain reaction (PCR) was performed using a first set of primers that recognize an internal sequence into N22 and a second set of primers amplifying a sequence within 5;NCR (5; noncoding region).

Results: The first set of primers revealed TTV DNA in 73% of thalassemic patients, in 8% of healthy children, and in 5% of healthy blood donors. With the second set of primers, the prevalence of TTV DNA was, respectively, 100% in thalassemic patients, 44.5% in healthy pediatric patients, and 87% in healthy blood donors. All individuals who tested positive for TTV by the first set of primers were also positive by the second primer set. The TTV infection seemed not to be the cause of altered transaminase levels. Sequencing of TTV clones from thalassemic patients showed the presence of different TTV variants in the same serum.

Conclusion: The prevalence of TTV in polytransfused children is similar to that detected in blood donors. Moreover, TTV can be detected in healthy children of all ages. The presence of TTV seems to have no clinical significance.