Methods for reducing levels of protein-contaminant complexes and aggregates in protein preparations by treatment with electropositive organic additives

A method of reducing the aggregate content of a sample, wherein the sample comprises a target antibody and aggregates comprising nucleic acid contaminants associated with the target antibody, the method comprising:

• (a) contacting the sample having a conductivity value of 5 mS/cm or higher with an electropositive organic additive at a non-zero amount of 0.1% weight/volume or less, and an undissolved allantoin, thereby forming a mixture comprising allantoin and precipitated nucleic acid contaminants, wherein allantoin is supersaturated in the mixture and the electropositive organic additive comprises ethacridine or polyethyleneimine;
• and
• (b) removing the undissolved allantoin and precipitated nucleic acid contaminants from the sample,
• wherein the sample, after (b) comprises the target antibody and a reduced amount of the aggregates, wherein the sample is derived from a cell culture or cell culture supernatant, and the target antibody is a recombinant antibody.