Torque Teno Virus: any pathological role in liver transplanted patients?

Few studies have been performed on the prevalence of Torque Teno Virus (TTV) infection in liver transplant (LT) recipients. The aim of this study was to assess the prevalence, viremia and genogroup pattern of TTV among LT patients and to ascertain whether TTV causes liver damage in liver transplanted patients with biochemical and histological changes of unknown origin. Twenty-five patients were evaluated before and after LT; 80 healthy subjects were considered as controls. Serum samples were serially obtained from all the patients before LT and thereafter at 3, 6 and 12 months post-transplant. Serum TTV-DNA and genogroups were assessed by PCR. Patients underwent protocol serial liver biopsies at 6 and 12 months after LT. Results were compared using the Chi-squared tests, McNemar's and Student's t-tests. TTV-DNA was found in 25/25 patients before LT and in 60/80 blood donors (P < 0.01). The TTV-DNA load increased significantly after LT (P < 0.001). TTV-DNA was significantly higher in patients on calcineurin inhibitors (CNI) and azathioprine or mycophenolate mofetil than in patients on CNI alone (P = 0.04) at 3 months after LT. Genogroup analysis showed a significant increase in genogroup 5 positivity after LT. No differences were seen in the viremia of patients compared according to their viral versus other etiologies of their liver disease before transplantation. Viremia and TTV genotype patterns did not correlate with the presence of hypertransaminasemia or histological liver damage of unknown etiology. The prevalence of TTV-DNA was significantly higher in patients with liver cirrhosis than in controls and the viral load was significantly higher after LT than beforehand. On the basis of our data, TTV does not seem to cause liver damage following LT, although larger studies with a long-term follow up are needed to confirm these findings.