Kinetics of torque teno virus DNA load in saliva and plasma following allogeneic hematopoietic stem cell transplantation

Plasma torque teno virus (TTV) DNA load directly correlates with the degree of T-cell immune reconstitution early after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Here, the kinetics of oral TTV DNA shedding was examined to assess whether quantitation of TTV DNA load in saliva may either replace or complement that in plasma for predicting lymphocyte (ALC) reconstitution after engraftment. This prospective observational study enrolled 38 nonconsecutive allo-HSCT recipients. Saliva and plasma specimens were collected at baseline (pretransplant) and at around days +30, +50, and +90 after allo-HSCT. TTV DNA was quantitated in both specimen types by real-time PCR. ALCs were measured by cytometry. A total of 104 paired saliva and plasma specimens were available for TTV PCR analyses. TTV DNA was detected more frequently in saliva than in plasma specimens at all time points (overall, 94.2% vs 86.5%). Increasing levels of TTV DNA were seen in both specimen types from day +30 to day +90 after transplantation. Overall, TTV DNA loads were significantly higher in saliva than in plasma specimens (P=.0002) and correlated significantly (P≤.0001). A direct correlation between TTV DNA loads in saliva and plasma and ALCs was observed after engraftment (P=.034 and P=.002, respectively). Future studies should be aimed at determining whether monitoring of oral TTV DNA shedding may be of any utility for inference of immune reconstitution after allo-HSCT.