Stability of BK polyomavirus IgG seroreactivity and its correlation with preceding viremia.

Background: Recently we showed that the level of BK polyomavirus (BKPyV) IgG seroreactivity in kidney donors predicted viremia and BKPyV-associated nephropathy in kidney transplant recipients (KTRs). This observation could be explained by assuming a direct association between BKPyV seroreactivity and the amount of persistent infectious virus in the renal allograft.

Objectives: Since the renal BKPyV reservoir is probably sowed by viremia during primary BKPyV infection, we systematically analysed the dynamics of BKPyV IgG seroreactivity in relation to preceding BKPyV viremia in KTRs and healthy individuals.

Study Design: A cohort of 85 KTRs consisting of BKPyV viremic and nonviremic subjects was analysed for BKPyV IgG seroreactivity at five fixed time points until one year after transplantation. A cohort of 87 healthy blood donors (HBDs) was used as controls.

Results: Baseline BKPyV seropositivity was high in both KTRs and HBDs, and the baseline mean BKPyV IgG level comparable. BKPyV IgG levels in nonviremic KTRs and HBDs remained stable during follow-up, while a considerable increase was observed in viremic KTRs (p=0.015). The increase of BKPyV seroreactivity in viremic KTRs was associated with the duration and peak level of BKPyV viremia.

Conclusions: BKPyV IgG seroreactivity was stable over time in immunocompetent subjects, which enables the use of this potential pretransplantation biomarker in kidney donors. The observed dose-dependent relationship of BKPyV IgG seroreactivity with preceding BKPyV replication is in agreement with the assumption that BKPyV seroreactivity reflects past BKPyV activity and correlates with the amount of latent BKPyV residing within a kidney allograft.