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

Introduction: 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 & REG;PCR; the TTV viral load kinetics in renal transplant recipients and the association with graft rejection.Materials and methods: 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 & REG;PCR). Associations of TTV viral load with graft rejections were analyzed.Results: 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 & REG;PCR) compared to patients without graft rejection (6.14 and 5.96 Log10 copies/mL, respectively).Conclusions: 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, cutoff values for risk stratification to predict rejection might be determined in relation to the post-transplant period.