Dynamics of Torque Teno virus plasma DNAemia in allogeneic stem cell transplant recipients

- Plasma TTV DNA load decreases after conditioning.
- Plasma TTV DNA load increases after engraftment.
- TTV DNA load increases in parallel to lymphocyte counts.
- Higher TTV DNA load increases in the setting of severe aGvHD.

BackgroundTorque Teno virus (TTV) plasma DNA load directly correlate with the level of immunosuppresion in different clinical settings. It is uncertain whether this may be the case in allogeneic hematopoietic stem cell transplant recipients (allo-HSCT).ObjectivesWe characterized the dynamics of TTV DNAemia in patients undergoing T-cell replete allo-SCT.Study designRetrospective single-center observational study including 72 allo-HSCT patients. Plasma TTV DNA loads were quantified before initiating the conditioning regimen and at different time-points after transplant by real-time PCR. White blood cells (WBC) and absolute lymphocyte counts (ALC) were measured by flow cytometry.ResultsA dramatic drop in plasma TTV DNA load was observed shortly after conditioning. The TTV DNA load increased steadily after engraftment reaching its peak at day +90 after transplant. The increase in TTV DNA load paralleled that of ALC, and was of greater magnitude in patients who developed severe (grades II-IV) acute graft vs. host disease.ConclusionRepopulation of lymphocytes early after allo-HSCT correlates with an increase of plasma TTV DNA load. Prospective studies are nevertheless needed to determine whether the kinetics of TTV DNAemia may allow inference of the degree of overall immunocompetence in these patients.