New biomarkers reflecting the degree of immunosuppression in transplant recipients are needed to provide an optimal personalized balance between rejection and infection risks.

For this purpose, we investigated TTV viremia dynamics in 66 kidney transplant recipients followed up for two years after transplantation, in relation to BK virus infection and graft rejection.

After transplantation, TTV viremia rose by ≥2 log₁₀ copies/mL from baseline to month 3, then declined by ≥1 log₁₀ copies/mL thereafter. Higher TTV viremia was associated with recipients of a deceased donor, a lower count of CD8+ T cells and a higher BKV viremia. Importantly, TTV loads were significantly lower in KTR who would later display graft rejection; indeed, patients with TTV viremia lower than 3.4 log₁₀ copies/mL at transplantation or lower than 4.2 log₁₀ copies/mL at month 1 had a higher risk of developing graft rejection in the two following years (hazard ratio (HR) at D0 = 7.30, p = 0.0007 and HR at M1 = 6.16, p = 0.001).

TTV viremia measurement at early times post transplantation predicts graft rejection and would represent a useful tool to improve kidney transplant monitoring.