Supplementary Material for: Retrospective analysis of graft loss risk in patients with BK Polyomavirus associated nephropathy in relation to rejection status in a multicenter cohort with regular surveillance of BK Polyomavirus and donor specific antibody

Introduction: BK polyomavirus (BKPyV) in kidney transplant associated with adverse graft outcome. The aim of this study was to examine graft loss risk of BK polyomavirus associated nephropathy (BKPyVAN) and BKPyV-DNAemia in relation with de novo donor specific antibody and rejection status.
Methods: Two hundred and forty patients from a multicenter cohort who had regular BKPyV and donor specific antibody (DSA) surveillance were retrospectively reviewed and stratified according to the presence of BKPyV-DNAemia and rejection.
Results: BKPyV-DNAemia did not associate with de novo DSA development (Hazard Ratio [HR] 1.15, 95% confidence interval [CI] 0.50-2.67, p=0.74) but de novo DSA was more commonly observed in patients who developed rejection (BKV+/Rejection- 4.3% (n=2) vs BKV+/Rejection+ 57.1% (n=4), p<0.001). BKPyV-DNAemia (adjusted HR 4.02, 95%CI 1.30-12.43, p=0.016) and de novo DSA (adjusted HR 6.76, 95%CI 2.51-18.24, p<0.001) were independent factors associated with antibody mediated rejection. Patients with BKPyV-DNAemia who were further complicated with rejection had approximately 6-fold risk of graft loss (adjusted HR 6.24, 95% CI 2.04-19.09, p=0.001), whereas patient with BKPyV-DNAemia alone did not experience significant increase graft loss risk (adjusted HR 1.76, 95% CI 0.64-4.81, p=0.27).
Conclusions: Our study suggested that DSA monitoring would be warranted during immunosuppressant reduction for BKPyV-DNAemia and less aggressive reduction of when DSA emerges might be a reasonable strategy to avoid overzealous reduction of immunosuppressant that could precipitate allograft rejection.