Cytomegalovirus Neutralization by Hyperimmune and Standard Intravenous Immunoglobulin Preparations

Background. Cytomegalovirus (CMV) remains one of the most important pathogens after transplantation, potentially leading to CMV disease, allograft dysfunction, acute, and chronic rejection and opportunistic infections. Immunoglobulin G (IgG) preparations with high antibody titers against CMV are a valuable adjunctive prevention and treatment option for clinicians and apart from standard intravenous immunoglobulin (IVIG), CMV hyperimmune preparations are available. The CMV antibody titer of these preparations is typically determined by Enzyme-linked immunosorbent assay (ELISA), also used for the selection of high titer plasma donors for the production of the CMV Hyperimmune product. However, CMV ELISA titers do not necessarily correlate with CMV antibody function which is determined by virus neutralization tests. Methods. CMV antibody titers were determined by both ELISA and virus neutralization assay and the IgG subclass distribution was compared between a CMV hyperimmune licensed in Europe and standard IVIG preparations. Results. Although the expected high CMV IgG ELISA antibody titers were confirmed for three lots of a CMV hyperimmune preparation, the functionally more relevant CMV neutralizing antibody titers were significantly higher for 31 lots of standard IVIG preparations. Moreover, considerably lower IgG3 levels were found for the CMV hyperimmune preparation compared with standard IVIG preparations. Conclusions. The higher functional CMV neutralization titers of standard IVIG preparations and the better availability of these preparations, suggest that these products could be a valuable alternative to the CMV hyperimmune preparation.