Quantification of Torque Teno Virus Load to Monitor Short-term Changes in Immunosuppressive Therapy in Kidney Transplant Recipients

Abstract

Background. Quantification of torque teno virus (TTV) has been proposed as a surrogate parameter to monitor immunocompetence in kidney transplant recipients (KTRs) early after transplantation. However, its use in monitoring short-term changes of immunosuppression in KTRs late after transplantation requires further investigation. Methods. In this post hoc analysis, we quantified TTV load in sera of 76 KTRs, with 43 pausing mycophenolic acid (MPA) 1 wk before to 4 wk after COVID-19 vaccination to increase vaccine response. TTV load was quantified before, 4 wk, and 3 mo postvaccination. Results were compared to 33 KTRs with continued standard immunosuppressive therapy and with 18 hemodialysis as well as 18 healthy control subjects. Results. TTV load before vaccination was with a median (interquartile range) of 1.39 × 104 copies/milliliter (c/mL) (9.17 × 101–2.66 × 105 c/mL) highest in KTRs compared to 1.73 × 103 c/mL (1.07 × 103–1.31 × 104 c/mL) in hemodialysis patients and 1.53 × 102 c/mL (6.38–1.29 × 103 c/mL) in healthy controls. In KTRs with MPA withdrawal, TTV load decreased significantly from a median (interquartile range) of 1.11 × 104 c/mL (4.75 × 102–1.92 × 105 c/mL) to 5.24 × 103 c/mL (6.92 × 102–6.91 × 104 c/mL) 4–5 wk after initiation of MPA withdrawal (P = 0.003). In patients with MPA withdrawal, TTV load was significantly inversely correlated with COVID-19 or SARS-CoV-2–specific antibodies 4 wk and 3 mo postvaccination (P = 0.009 and P = 0.004). Conclusions. TTV load reflects changes in immunosuppressive therapy even late after transplantation, supporting its use to monitor immunocompetence in KTRs.