Removal of serine proteases by treatment with finely divided silicon dioxide

A plasma-derived immunoglobulin G (IgG) composition comprising an IgG concentration of at least 10% and a serine protease concentration that induces hydrolysis of the substrate S-2266 at a rate of less than 5 nmol/ml×min, and wherein said composition is prepared by a method comprising the steps of:

• (a) precipitating a cryo-poor plasma fraction, in a first precipitation step, with from about 6% to about 10% alcohol at a pH of from about 7.0 to 7.5 to obtain a first precipitate and a first supernatant;
• (b) precipitating IgG from the first supernatant, in a second precipitation step, with from about 23% to about 27% alcohol at a pH of from about 6.7 to about 7.3 to form a second precipitate;
• (c) suspending in a buffer the second precipitate to form a first suspension;
• (d) contacting the first suspension with finely divided silicon dioxide (SiO2) under a solution condition suitable to bind a serine protease or serine protease zymogen, wherein the solution condition suitable to bind the serine protease or serine protease zymogen comprises a pH between about 4.5 and about 6.0 and a conductivity of between about 0.1 mS/cm and about 3 mS/cm;
• and
• (e) separating the SiO2 from the first suspension to form a clarified suspension.