Commercially available immunoglobulins contain virus neutralizing antibodies against all major genotypes of polyomavirus BK

Abstract

Neutralizing antibodies (NAbs) form the basis of immunotherapeutic strategies against many important human viral infections. Accordingly, we studied the prevalence, titer, genotype-specificity, and mechanism of action of anti-polyomavirus BK (BKV) NAbs in commercially available human immune globulin (IG) preparations designed for intravenous (IV) use. Pseudovirions (PsV) of genotypes Ia, Ib2, Ic, II, III, and IV were generated by co-transfecting a reporter plasmid encoding luciferase and expression plasmids containing synthetic codon-modified VP1, VP2, and VP3 capsid protein genes into 293TT cells. NAbs were measured using luminometry. All IG preparations neutralized all BKV genotypes, with mean EC50 titers as high as 254 899 for genotype Ia and 6,666 for genotype IV. Neutralizing titers against genotypes II and III were higher than expected, adding to growing evidence that infections with these genotypes are more common than currently appreciated. Batch to batch variation in different lots of IG was within the limits of experimental error. Antibody mediated virus neutralizing was dose dependent, modestly enhanced by complement, genotype-specific, and achieved without effect on viral aggregation, capsid morphology, elution, or host cell release. IG contains potent NAbs capable of neutralizing all major BKV genotypes. Clinical trials based on sound pharmacokinetic principles are needed to explore prophylactic and therapeutic applications of these anti-viral effects, until effective small molecule inhibitors of BKV replication can be developed.

Keywords: Editorial / personal viewpoint; disparities; liver transplantation/hepatology; organ allocation.

Figure 1:. Titers of anti-BKV genotype Ia neutralizing antibodies in commercial preparations of human intravenous immunoglobulin (IVIG) and cytomegalovirus hyperimmune intravenous immunoglobulin (CMVIG).

The x-axis depicts serial dilutions (log₁₀) of IVIG and CMVIG added to the culture of 293TT cells exposed to BKV genotype Ia reporter vector. Luciferase release measured in relative light intensity units (RLUs) is plotted on the y-axis. Fifty percent inhibition (EC50) was obtained at a dilution of 1:51814 for IVIG and 1:18349 for CMVIG. Data is expressed as mean ± SE from triplicate wells of one representative experiment. The curves were plotted using Graph Pad Prism software.

Figure 2:. Scatter plot of the geometric means of neutralizing antibodies to the pseudovirions panel in two different lots of IVIG.

Lot 1 is represented on x-axis and lot 2 on y-axis.

Figure 3:

The effect of complement on neutralization of pseudovirions Ia (A) and 1Vc (B) by IVIG. Neutralizing experiments described in the Methods section were performed in the presence of two different dilutions of antibody (1: 6400 and 1:102,400) and thee concentrations of C3 (10×, 5× and 3× times the molar concentration of immunoglobulin in the culture wells). The luminescence signal obtained is expressed as a percentage of the maximal signal obtained in the presence of IVIG alone (without C3). Data represents mean +/− SD of 4 experiments for each condition evaluated. p-values refer to comparisons of the individual signals with the maximum signal. p < 0.05, ##p = 0.06, ###p = 0.07.