Comparison of antibody activity against various microorganisms in intravenous immunoglobulin preparations determined by ELISA and opsonic assay.

In the present study the level of antimicrobial antibodies and the phagocytosis-promoting activity in immunoglobulin preparations produced for intravenous use were assessed. The level of antibodies directed against various microorganisms in six immunoglobulin preparations was determined by using an enzyme-linked immunosorbent assay (ELISA) and was shown to be either equal to or higher than that of pooled normal human serum. All preparations were able to promote phagocytosis of Staphylococcus aureus, Escherichia coli K12, and Streptococcus pyogenes by human granulocytes. Substantial differences among the various preparations in antibody activity were noted. In particular, Intraglobulin, chemically modified by beta-propiolactone treatment, exhibited little activity in both the ELISA and the phagocytosis assay. In contrast, IVIG SRC, Gamimmune, Sandoglobulin (treated at low pH in presence or absence of trace amounts of pepsin), and Gammagard (treated by ion-exchange chromatography) showed good activity in both assays. Comparison of the results of the ELISA and phagocytosis assay for the various preparations indicated a good correlation except for S. aureus with a moderate (strain 42D) or high (strain Cowan I) protein A content. These data indicate that the antibody activity of immunoglobulin preparations against various microorganisms determined by ELISA can be used to predict their opsonic activity.