<scp>HLA</scp> ‐B Leader Dimorphism Predicts <scp>BK</scp> Polyomavirus Replication After Kidney Transplant

BK polyomavirus (BKPyV) and Cytomegalovirus (CMV) often replicate after kidney transplantation, with management limited to reducing immunosuppression and risking rejection. Among genetic factors that may modulate the antiviral response, HLA evolutionary divergence (HED, allowing a greater diversity of antigen presentation) and the HLA-B leader dimorphism (MM, MT, TT, influencing NK cell-mediated immunity) are interesting. We aimed to compare these parameters between patients who experienced viral replication within the first post-transplant year and those who did not. We analysed 306 kidney transplants performed between 2019 and 2023 at Amiens University Hospital. HLA typing was performed in recipients and donors to determine HED (loci A, B, C, DRB1, DQB1) and HLA-B leader dimorphism. 22.5% of the recipients (69/306) developed BKPyV possible nephropathy (defined by urinary PCR > 7 log₁₀ copies/mL or DNAemia) and 40.2% (123/306) developed CMV infection during the first year. In a multivariate analysis, a donor-recipient HLA-B leader mismatch was protective against BKPyV replication (OR = 0.48; p = 0.02), whereas no similar association was observed for CMV replication (OR = 1.42; p = 0.169). HLA-B leader dimorphism could serve as a predictor of BKPyV replication risk, if confirmed in independent cohorts.