Comparison of cytomegalovirus (CMV)-specific neutralization capacity of hyperimmunoglobulin (HIG) versus standard intravenous immunoglobulin (IVIG) preparations: Impact of CMV IgG normalization

Abstract

Background: Based on a non-randomized study of Nigro et al. (2005) the intravenous administration of hyperimmunoglobulins (HIGs) is applied frequently to women with primary CMV-infection as "off-label use" in Germany.

Objectives: In order to describe their CMV-specific neutralization-capacity in vitro, we analyzed the HIG preparations Cytotect^®, and Cytogam^® as well as the standard intravenous immunoglobulins (IVIG) Octagam^®, Gamunex^®, Kiovig^®.

Study design: We performed short-term cell-free CMV neutralization assays (CFNT) and long-term cell-adapted neutralization-plaque-reduction assays (PRANT). Human retinal epithelial cells (ARPE-19) were used as target cells. A clinical CMV primary-isolate from amnion fluid propagated in epithelial cells without any initial fibroblast adaption was used. For calibration we previously generated serum-pools (N=100) from two cohorts of mothers at birth: seronegative and latently CMV-infected mothers. Biochemical analysis included total protein, albumin, Ig-class, and IgG-subclasses. Additionally, CMV antibody-reactivity was checked using recombinant immunoblotting.

Results: HIG and IVIG preparations showed differences in levels and patterns of protein, Ig-class and CMV-specific antibody concentrations. All IgG-preparations showed high in vitro NT-capacity and high IgG-avidity. The NT₉₀-values for HIGs and IVIGs and our seropositive reference-pool showed similar NT-capacity at a dilution of (1:100) which corresponded well to 4.1 PEI-Units/ml.

Conclusion: All HIG- and IVIG-preparations showed similar NT-capacity following CMV IgG-normalization. Our in vitro results are in strong contrast to former findings suggesting higher functional CMV NT titers in IVIG-preparations compared to HIGs.

Keywords: CMV primary infection; Hyperimmunogloblulin (HIG); Neutralizing antibodies; Pregnancy; Recombinant immunoblot; Standard immunoglobulin.