Prevalence of TT viral DNA in Italian blood donors with and without elevated serum ALT levels: molecular characterization of viral DNA isolates

Background and Objectives. A novel non-enveloped DNA virus, called TT virus (TTV), has been reported to be associated with post-transfusion hepatitis of unknown etiology. Although its clinical role still remains obscure, its presence in blood donations might cause problems. It, therefore, appeared o f interest to investigate TTV prevalence in voluntary blood donors. Design and Methods. A total of 595 Italian blood donors with and without el evated serum alanine aminotransferase (ALT) levels were tested by polymeras e chain reaction using two sets of semi-nested primers that amplify the wel l-known region in the N22 clone. The amplified products were then sequenced to assess the genotype by phylogenetic and restriction fragment length pol ymorphism analyses. Results. The prevalence of TW in blood donors was 5+/-1.9% (25 out of 500) with a 95% confidence limit. A similar prevalence was round in 95 selected blood donors with increased ALT levels. A viral load of 10(3)-10(4) viral D NA molecules/mL was found, thus indicating a rather narrow range of variabi lity. A phylogenetic tree built up on the basis of 210 base sequences of OR F1 allowed isolates to be classified into 2 groups corresponding, at least, to two of the putatives TTV genotypes, group 1 and group 2 of Okamoto's cl assification. A similar classification was also obtained by site restrictio n enzyme analysis. Interpretation and Conclusions. The results show that TTV infection is pres ent among Italian blood donors. No significant difference in prevalence of TTV infection was found between patients with normal and increased ALT, mak ing the association between TTV infection and human hepatitis questionable. (C) 2000, Ferrata Storti Foundation.