High sequence diversity among TT virus (TTV) and TTVlike viruses (TTLVs) is an obstacle to PCR detection of the entire spectrum of existing genotypes. To determine which primers are needed to detect all know genotypes of these viruses, an alignment of commonly used primer sequences with sequences of all known viral genotypes was performed to predict theoretically amplifiable genotypes. The results predicted that all TTV genotypes (except genotype 21), all SEN virus (SENV) genotypes (A to H), and three known TTVL minivirus (TLMV) groups would be detectable by TTV primers NG054/ NG147/133/132 (NG) and TT6/7/8/9 (TT), combined with two TLMV primer sets (TLMV-S and TLMV-L). To confirm these findings, we genetically characterized 420 clones of NG primer products from 32 thalassemia patients and 8 healthy individuals, as well as 50 PCR products amplified by TT and RD037/

As a consequence of the high prevalence of TorqueTeno virus (TTV) in blood donors, thalassemia patients frequently acquire various genotypes of this virus through therapeutic blood transfusions. At present, the clinical consequences of TTV infection remain indeterminate for these patients. Here, several hundred thalassemia patients were tested for the presence of TTV and its genotypes using a combination of PCR and clone-based DNA sequencing. Approximately 10% (12/118) of the patients aged 2-20 years remained negative for TTV including eight genotypes of SENV. Ferritin, aspartate-aminotransferase (AST) and alanine-aminotransferase (ALT) levels were invariably lower in TTV-negative patients (P = 0.02, <0.01, and 0.06, respectively) than in TTV-positive patients. Patients with TTV-HCV co-infection showed elevated ferritin and ALT levels compared with patients with TTV infection alone (P < 0.02 and P < 0.01). AST and ALT levels were within the normal range for all TTV-negative patients, whereas abnormal levels of AST and ALT were seen in a significant proportion of TTV-positive patients (30.7% and 33.6%, respectively) and patients with TTV-HCV co-infections (70.0% and 56.6%, respectively). Only TTV-positive patients (28.0%) and patients with TTV-HCV co-infections (36.3%) had hyper-ferritin levels (> or =3,000 ng/ml). The genotype(s) of TTV responsible for the liver dysfunction could not be determined. However, high levels of AST and ALT were found to be correlated with detection of a higher number of TTV genotypes in the patients. The data suggests that frequent and persistent TTV infection through blood transfusion is associated with hepatic dysfunction and/or damage in transfusion dependent thalassemia patients.