Torque Teno Virus Control by the Classical Pathway of Complement Activation—A Retrospective Analysis From a First-in-Human Trial Utilizing Sutimlimab

Torque Teno virus (TTV) load is linked with the functionality of its host's immune system and has been proposed as a potential monitoring tool for immune-modulating therapy. However, the immunological mechanisms of TTV control are incompletely understood. To assess the effect of the classical complement pathway on TTV, 64 healthy volunteers and 10 kidney transplant recipients treated with the anti-C1s antibody sutimlimab were analyzed for serum TTV copy numbers (c/mL) by qPCR. Overall, a correlation was observed between the decrease in complement activity caused by sutimlimab and the TTV load increase (ρ = −0.367, p < 0.001). Subgroup analysis indicated a trend toward TTV load increase in healthy volunteers following the highest sutimlimab dose compared to baseline (100 mg/kg body weight; median 3.5 log₁₀ c/mL, interquartile range [IQR] 2.8–4.4 vs. 2.9 log₁₀ c/mL, 0.8–3.5; p = 0.063). Administering multiple lower doses (30 mg/kg) also showed a trend toward TTV load increase in healthy volunteers (1.8 log₁₀ c/mL, 0–2.3 vs. 1.9, 1.3–2.8; p = 0.054) and a significant increase in transplant recipients (3.5 log₁₀ c/mL, 3.0–6.1 vs. 4.1, 3.5–6.4; p = 0.004). This report suggests a role for the classical complement pathway in controlling TTV load.