The Effect of Human Leukocyte Antigen-A1 and B35-cw4 on Sustained BK Polyomavirus DNAemia after Renal Transplantation.

Human leukocyte antigens (HLA) class I presentation pathway plays a central role in natural killer (NK) cell and cytotoxic T cell activities against BK polyomavirus (BKPyV) DNAemia. We determined the risk of sustained BKPyV DNAemia in 175 consecutive renal transplant recipients considering the simultaneous effect of donor/recipient HLA class I antigens and pre- or post-transplant variables. Median (IQR) age was 53 (44-64) years and 37% of patients were female. 40 patients (22.9%) developed sustained BKPyV DNAemia [median (IQR) viral load:9,740 (4,350-17,125) copies/ml]. In Cox proportional hazard analysis, HLA-A1 (HR: 3.06, 95% CI: 1.51-6.17) and HLA-B35-Cw4 (HR: 4.63, 95% CI: 2.12-10.14) significantly increased the risk of sustained BKPyV DNAemia while 2 HLA-C mismatches provided a marginally protective effect (HR: 0.32, 95% CI: 0.10-0.98). HLA-Cw4 is a ligand for NK cell inhibitory receptor and HLA-B35 is in strong linkage disequilibrium with the -Cw4 allele. The association between HLA-B35-Cw4 expression and sustained BKPyV DNAemia supports the important role of cytotoxic T cells and NK cells that would normally control BKPyV virus activation through engagement with immunoglobulin-like killer receptors (KIR). Further studies are required to investigate the effect of HLA-C alleles along with NK cell activity against BKPyV DNAemia.