Protective and opsonic activities of a native, pH 4.25 intravenous immunoglobulin G preparation against common bacterial pathogens.

The in vitro opsonic activity of a native, pH 4.25 immunoglobulin G preparation modified for intravenous use (IGIV pH 4.25) was compared with the activities of a standard reduced and alkylated, pH 6.8 preparation (IGIV-R/A pH 6.8) and a reduced and alkylated, pH 5.25 preparation (IGIV-R/A pH 5.25) against a variety of common bacterial pathogens. In most instances the opsonic titers of IGIV pH 4.25 equaled or exceeded that of IGIV-R/A pH 6.8; IGIV-R/A pH 5.25 usually had an intermediate level of activity. The protective activity of IGIV pH 4.25 against Escherichia coli in a neonatal rat model was also greater than that of IGIV-R/A pH 6.8. Thus, the functional activity of the new IGIV pH 4.25 apparently equals or exceeds that of standard reduced and alkylated preparations.