Intravenous Immunoglobulin Administration Significantly Increases BKPyV Genotype-Specific Neutralizing Antibody Titers in Kidney Transplant Recipients.

BK polyomavirus (BKPyV)-associated nephropathy (BKPyVAN) is one of the major causes of kidney graft dysfunction, and there are no BKPyV-specific antiviral therapies available. BKPyV neutralizing antibodies (NAbs) play key roles in protecting against BKPyV replication and represent a potential therapeutic or preventive strategy. In this study, we evaluated NAb titers in intravenous immunoglobulin (i.v. Ig) preparations and in kidney transplant recipients (KTR) before and after i.v. Ig administration. NAb titers directed against major BKPyV genotypes were measured using a BKPyV pseudovirion system. Thirty-three KTR receiving high (1 g/kg of body weight/day; n = 17) or low (0.4 g/kg/day; n = 16) i.v. Ig doses were included. Median NAb titers in i.v. Ig preparations ranged from 5.9 log10 50% inhibitory concentration (IC50) for genotype I to 4.1 log10 IC50 for genotype IV. A mean of 90% of patients (range, 88% to 100%) displaying low or negative BKPyV NAb titers against genotype I reached 4 log10 IC50 after the first i.v. Ig administration. This value was reached by a mean of 44% (range, 13% to 83%) and 19% (range, 0% to 38%) of patients against genotype II and genotype IV, respectively. The benefit of i.v. Ig administration persisted until the following course of treatment (day 22 ± 7 days) for genotypes I and II, and no cumulative effect was observed through the three doses. Our findings demonstrate that i.v. Ig administration results in a significant increase in BKPyV NAb titers in KTR. These in vitro and in vivo pharmacokinetic data provide the rationale for a proof-of-concept study investigating the efficacy of i.v. Ig for the prevention of BKPyV infection in KTR.