Unlocking the impact of BK virus in renal transplant recipients in North India: viral load dynamics, genotypes, and clinical outcomes.

BACKGROUND: BK polyomavirus (BKPyV) reactivation post kidney transplant patients can lead to graft-damaging nephropathy. This exploratory study evaluated the prevalence of BKPyV infection, clinical characteristics, and the association of transplant related clinical parameters and plasma viral load in kidney transplant recipients from North India. METHODS: Ninety kidney transplant recipients were screened for plasma BKPyV DNA by real-time PCR. Clinical follow-up and tacrolimus trough concentration data were available for 57 recipients. Recent tacrolimus exposure was estimated as the mean tacrolimus trough concentration during the six months preceding BKPyV testing (Tac C₀-6 m) while intrapatient variability (IPV) was assessed using the coefficient of variation (%CV). BKPyV genotyping was performed in representative 3 BKPyV positive samples. For statistical analysis, GraphPad PRISM v8.0.1 was used and figures were generated using ggplot2 package in R. A two-sided P values <0.05 was considered statistically significant. RESULTS: BKPyV DNA was detected in 13/90 (14.4%) recipients. BKPyV(+) patients had significantly higher mean Tac C₀-6 m than BKPyV(-) recipients (median 7.38 vs. 5.30 ng/mL; P = 0.002). Mean Tac C₀-6 m correlated positively with plasma BKPyV viral load (Spearman's ρ = 0.588, P = 0.035). Neither time from transplantation to BKPyV positivity (ρ = 0.356, P = 0.232), nor tacrolimus IPV (ρ = 0.505, P = 0.078) showed significant correlations with viral load. No significant differences were observed in acute rejection, calcineurin inhibitor toxicity, decoy cells, or transplant-related death between BKPyV(+) and BKPyV(-) recipients. CONCLUSIONS: In this exploratory study, higher recent tacrolimus exposure was associated with BKPyV positivity and viral load, supporting individualized immunosuppression management and routine BKPyV surveillance in kidney transplant recipients.