Investigation of Torque Teno Virus (TTV) DNA as an immunological and virological marker in pediatric hematopoietic stem cell transplantation (HSCT) patients

High viral loads are observed in Torque Teno Virus (TTV) infection after hematopoietic stem cell transplantation (HSCT). We aimed to analyze the kinetics of plasma TTV-DNA load in pediatric patients who received immunosuppressive therapy and developed infection complications in the first 100 days after HSCT. As a patient group; 113 plasma samples taken from 33 pediatric HSCT recipients at a time interval after transplantation and as a control group; 38 plasma samples from 38 children without known chronic disease were included in the study. Viral nucleic acid isolation was performed by using the NucliSENS easyMAG (bioMerieux, France) system. A laboratory designed quantitative polymerase chain reaction process was performed on 7300 Real-Time PCR system (Applied Biosystems, CA, USA) with the amplification mixture containing primer and probe sequences for the UTR gene region. TTV-DNA was detected in all patient's samples and the median viral load was calculated as 7.67 Log10 copies/mL (range: 2.84–9.59). In the control group, the TTV-DNA median viral load was calculated as 5.51 Log10 copies/mL (range: 2.50–7.04), except for one negative sample. A significant difference was observed between the control group and the patient group in terms of TTV viral load levels. In nine patients, a median 2.15 Log10 copies/mL viral load increase was observed at 31–60 days post-transplant compared to the pre-transplant period. TTV-DNA levels should be closely monitored to understand the immune status of the first 100 days after transplantation and the effects of treatment regimens on patients with HSCT. •TTV is an immunological biomarker with the potential to improve treatment follow-up in HSCT patients.•TTV-DNA loads show fluctuations depending on the immunological status in the early period after transplantation.•Considering high viral shedding of TTV in pediatric age, cut-off values should be determined to guide follow-up in immunosuppressive patients.