Evaluation of Torque Teno Virus DNA Load as a Predictive Biomarker in Kidney Transplant Recipients Converted from Calcineurin Inhibitors to Belatacept

Introduction: Belatacept is a relevant alternative to calcineurin inhibitors (CNIs) after kidney transplantation (KT). Circulating Torque Teno virus (TTV) DNA load is correlated to infections and rejection risks post -KT in patients treated with CNIs. The aim of this study was to assess the TTV DNA load pro fi le in kidney transplant recipients converted from CNIs to belatacept and explore its use as a predictive biomarker. Methods: Sixty-eight single -center kidney transplanted recipients who were converted from CNIs to belatacept between June, 2015 and December, 2020 were included in this study. Whole blood TTV DNA load was measured before, at 3, 6, and 12 months post-belatacept conversion. Our primary end point was to assess the TTV DNA load pro fi le and correlate the results with rejection and opportunistic infection (OPI). Results: TTV DNA load remained stable after belatacept conversion, that is, 3.8 (3.1 - 4.9), 4.4 (3.2 - 5.4), 4.0 (3.0 - 5.7) and 4.2 (3.0 - 5.2) log 10 copies/ml at baseline, 3, 6, and 12 months, respectively. No correlation was found between TTV DNA load and post -KT complications. Chronic allograft dysfunction at 1 year postconversion was associated with a lower TTV DNA load after 6 and 12-months ( P = 0.014 and P = 0.021, respectively). A higher TTV DNA load was found in older patients and in those with higher body mass index (BMI) ( P = 0.023 and P = 0.005, respectively). Conclusion: Conversion from CNIs to belatacept did not affect TTV DNA load. OPIs or acute rejection occurrences were not associated with TTV DNA load. However, low TTV (lTTV) DNA load after 6 months postconversion may be a promising tool to predict graft dysfunction risk at 1 -year postconversion.