Exploring the Association Between Torquetenovirus Viral Load and Immunosuppressive Drug Exposure in Lung Transplantation

To improve lung transplant recipient (LungTx) outcome, it would be of great interest to measure the net state of immunosuppression to avoid both infection and rejection. Measurement of <i>Torquetenovirus</i> load (TTV load) has been proposed as a biomarker to monitor solid organ transplantation, but its relationship with immunosuppressive drugs, particularly mycophenolic acid (MPA), is not well understood. We performed a prospective study of 53 LungTx, measuring TTV load before transplantation, at week 3, and at month 3. Tacrolimus and MPA doses and levels were recorded, and an area under the MPA curve (AUC-MPA) was calculated at the third month. LungTx in the fourth quartile of TTV load at the third week and the third month exhibited a low risk of acute rejection (OR 0.113, 95% CI 0.013-0.953, <i>p</i> = 0.045) and a high risk of opportunistic infection from month 3 to 6 (OR 15.200, 95% CI 1.525-151.511, <i>p</i> = 0.020), respectively. TTV load was weakly related to tacrolimus trough level at month 3 (rho = 0.283, <i>p</i> = 0.040). Neither MPA blood levels nor AUC-MPA were related to TTV load, although only patients with a reduction in MPA dose from month 1 to 3 showed a smaller increase in TTV load (0.86, IQR 2.58 log10 copies/mL vs. 2.26, IQR 3.02 log10 copies/mL, <i>p</i> = 0.026). In conclusion, TTV load in LungTx is only partially related to exposure to immunosuppressive drugs. Other variables, such as inflammation, immunosenescence, and frailty, may influence the overall level of immunosuppression and TTV load.