[Detection of TT virus DNA by nested-PCR method in non A-E hepatitis cases]

TT virus (TTV) is the unique single stranded circular DNA virus, isolated from humans. Viral DNA is shown to be present not only in patients with hepatitis of unknown etiology but also in apparently healthy populations. TTV's role as a causative agent for non A-E hepatitis is widely questioned. In this study, 23 non A-E hepatitis patients (mean age: 46.8 yrs), 21 chronic hepatitis B (CHB) patients (mean age: 41.0 yrs), 28 chronic hepatitis C (CHC) patients (mean age: 48.1yrs) have been investigated, together with 90 healthy blood donors (mean age: 33.4 yrs), for the presence of TTV-DNA by nested polymerase chain reaction (PCR). Two sets of primers targeting different regions (N22 and NCR) of the viral genome were combined to enhance the detection sensitivity. TTV-DNA was detected in 10 (43.5%) of non A-E hepatitis, 10 (35.7%) of CHC, 4 (19.1%) of CHB patients, and 16 of studied 52 (30.8%) blood donors, by N22-PCR. Viral DNA positivity rates by using NCR-PCR were found as follows for the groups respectively; 65.2% (15/23), 50% (14/28), 42.9% (9/21) and 57.8% (52/90). The differences of TTV-DNA positivity rates between study groups were found statistically insignificant, when data from each set of primer were compared (p>0.05). However, the positivity rate of non A-E hepatitis group (91.3%) was significantly higher than CHC (64.2%), CHB (47.6%), and control (57.8%) groups, when the detection sensitivities of both sets were combined (p=0.002 and p=0.046, respectively). The study also revealed that the prevalence of TTV might be underestimated if appropriate molecular methods were not employed. DNA sequencing and genotyping are required to establish TTV's role as a causative agent of non A-E hepatitis and to identify certain genotypes that might have a role in the pathogenesis of hepatitis.