Contaminant viruses can be efficiently removed almost without losing the
activity of protein by subjecting a plasma protein composition having a
high risk of viral contamination to a treatment with a porous membrane
having a pore size greater than a single-particle size of the virus,
particularly by subjecting a plasma protein composition to a fractionation
treatment by precipitation, before the porous membrane treatment.
Particularly, a fibrinogen composition substantially free of non-enveloped
viruses, Parvovirus among others, can be provided. By the application of
the present invention, a safe plasma protein preparation free of viruses
can be conveniently provided.
