Capture, concentration and quantitation of abnormal prion protein from biological fluids using depth filtration
Methods for producing biological solutions such as immunoglobulins and in particular anti-D immunoglobulin substantially free of abnormal prion protein resulting therefrom. Specifically provided are methods for aggregation of prions and depth filtration of the biological solution to capture and remove abnormal and if desired, normal prion protein. The prion protein may then be eluted from the depth filter and filter washes and concentrated sufficient for detection at limits currently required by available assays.
1. A method of removing prion protein from a aqueous pharmaceutical composition comprising an IgG anti-D immunoglobulin, wherein the pharmaceutical composition comprises from about 4.0 to 6.0% immunoglobulin by weight, and from about 80 to 200 ppm polysorbate 80, comprising:
(a) admixing the aqueous composition with from about 2% to about 10% methanol; and
(b) filtering the admixture of step (a) through a depth filter having a pore size providing a retention of less than about 0.6 microns,
thereby removing the prion protein, wherein the recovery of the biological protein in its original biological state is substantially maintained at least to a level in excess of about 50%, and wherein the removal of the abnormal infective prion protein may be achieved to an extent of at least about 10 2.5 .