Prospective cohort study of Torque Teno Virus (TTV) viral load kinetics and the association with graft rejection in renal transplant patients

Graft survival is mainly determined by rejections and infectious complications in transplant recipients. Torque Teno Virus (TTV), a nonpathogenic and ubiquitous single-stranded DNA virus, has been proposed as a biomarker of the immune status in transplant patients. This study aimed to determine the correlation between a Home-Brew TTV PCR and R-GENE®PCR; the TTV viral load kinetics in renal transplant recipients and the association with graft rejection. Prospective cohort study on 107 adult renal transplant recipients. TTV viral load was determined in 746 plasma samples collected before and after renal transplantation by a Home-Brew PCR and a commercial PCR (R-GENE®PCR). Associations of TTV viral load with graft rejections were analyzed. Agreement of both PCR assays was 93.2% and Pearson correlation coefficient was r: 0.902 (95%CI: 0.8881–0.9149, p < 0.0001). TTV viral load kinetics showed an initial gradual increase reaching a peak at 3 months. This highest value was followed by a slight decrease, reaching a plateau significantly higher than the initial baseline at 6 months (p < 0.0001). Between (181–270) days post-transplantation, TTV median viral load in patients with graft rejection was significantly lower, 3.59 Log10 copies/mL (by Home-Brew PCR) and 3.10 Log10 copies/mL (by R-GENE®PCR) compared to patients without graft rejection (6.14 and 5.96 Log10 copies/mL, respectively). Significantly lower TTV viral load was observed in patients with renal rejection occurring at a median of 243 days post-transplantation. Given the dynamic behavior of TTV viral load post-transplantation, cut-off values for risk stratification to predict rejection might be determined in relation to the post-transplant period.