Role of pentamer complex-specific and IgG subclass 3 antibodies in HCMV hyperimmunoglobulin and standard intravenous IgG preparations.

BACKGROUND: HCMV hyperimmunoglobulin-preparations (HIG) contain high concentrations of HCMV-specific IgG. The reduced maternofetal-HCMV-transmission rate of IgG may be due to HCMV-specific neutralizing antibodies against the HCMV pentameric complex (PC). In contrast to HIG, standard intravenous immunoglobulin (IVIG) may have more neutralization (NT) capacity than HIG due to higher IgG subclass 3 levels (Planitzer et al., 2011).

METHODS: We investigated the HCMV-specific NT-capacity of HIG Cytotect® , using a recombinant pentameric complex (gHgLUL128-131A) for specific antibody-depletion. We used a modified UL130-peptide (TANQNPSPPWSKLTYSKPH) based on original-sequence of Saccoccio et al. (Vaccine 29(15):2705-2711, 2011) (SWSTLTANQNPSPPWSKLTY) as neutralization target. Both UL130-peptides and the PC were bound via sixfold HisTag and anti-HisTag mAbs to magnetic beads to deplete HCMV-specific IgGs from HIG (Cytotect® ). Modifying this depletion strategy, we analyzed the role of IgG subclass 3 in both HIG and IVIG.

RESULTS: After CMV IgG-normalization of HIG and IVIG, we found a significant trend towards a decrease (16%) of neutralization-capacity for the UL130 TAN-peptide, but not for the original UL130 SWS-peptide. However, highly significant loss of NT-capacity could be only observed by PC depletion (42%). The IgG subclass 3 depletion revealed no significant reduction of NT-capacity in both HIG and IVIG.

CONCLUSION: Via specific antibody depletion, we could demonstrate that pentameric complex-specific antibodies are present in HIG and bind to the recombinant PC resulting in a highly significant reduction of NT-capacity compared to the UL130 TAN-and SWS-peptides. We could not confirm the functional role of IgG subclass 3 neutralizing antibodies in IgG-preparations.