Neutralization of human parvovirus B19 by plasma and intravenous immunoglobulins

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Abstract
BACKGROUND: Human parvovirus B19 (B19V) is a highly prevalent pathogen, and plasma pools for manufacturing of plasma-derived products have been shown to contain antibodies against B19V (B19V immunoglobulin G [IgG]). STUDY DESIGN AND METHODS: The megakaryoblastic cell line UT7/Epo-S1 can be infected with B19V Genotype 1 and as demonstrated here by immunocytochemistry, Western blot, and reverse transcription–polymerase chain reaction (RT-PCR) of B19V-specific mRNA, also with the more recently discovered Genotype 2. Based on B19V RT-PCR analysis of infected UT7/Epo-S1 cells, an infectivity assay was established and implemented for a B19V neutralization assay. To investigate the role of B19V neutralization in relation to B19V IgG titers, more than 1000 manufacturing plasma pools were tested by enzyme-linked immunosorbent assay. RESULTS: Plasma pools were found to contain a mean B19V IgG titer of 33 ± 9 IU per mL, with the lowest titer at 11 IU per mL. These 11 IU per mL B19V IgG neutralized 4.6 log B19V Genotype 1 and greater than 3.9 log Genotype 2 infectivity. Accordingly, a 10 percent intravenous immunoglobulin (IVIG) product prepared from such pools was found to contain an even higher B19V neutralization capacity. CONCLUSION: A high capacity of B19V Genotypes 1 and 2 neutralization was demonstrated in plasma pools for fractionation, an inherent feature based on the constantly high titer of B19V IgG in these pools. The neutralizing activity of B19V IgG was shown to be maintained in the 10 percent IVIG product tested.