Immune responses to BK virus in renal transplant recipients receiving IVIG treatment

Background BK polyomavirus (BKPyV) DNAemia in renal transplant recipients increases risk of allograft failure, but BKPyV-specific therapies are not available. While treatment with intravenous immune globulin (IVIG) has been reported, safety in a prospective randomized controlled setting is uncertain, and host immune response to BKV after IVIG is not well characterized. Methods We investigated host immune responses to BKPyV in a multicenter, prospective, randomized, double-blinded, placebo-controlled pilot study of IVIG with protocolized immunosuppression reduction in adult kidney transplant recipients with BK DNAemia. Participants received two infusions of 1g/kg up to 70 g each, one month apart, of IVIG or placebo and were followed for one year with adverse event monitoring. The primary endpoint was safety and tolerability of IVIG. Neutralizing antibody (nAb) to common BKPyV strains and BK-specific CD4+/CD8+ T-cell and natural killer cell (NKC) responses were evaluated. Results There were no adverse events. 40.0% of recipients in the treatment arm and 44.4% in the control arm cleared BK DNAemia at three months (RR 0.90; 95% CI, 0.23-2.89). Overall, 80% of recipients with a sequenced BK genotype possessed cognate nAb at baseline, and 100% acquired them by three months. Viral clearance was associated with higher percentages of BKPyV-specific CD8+ T-cells prior to IVIG (0.19% vs 3.01%, p < 0.01). Conclusions In this pilot study, two doses of IVIG were safe, but its impact on viral clearance is unclear; control of DNAemia may depend upon intrinsic virus-specific host cellular and humoral response, but further studies are needed.