After removal of the dicyclohexylurea precipitate with centrifugation, the supernatant may be transferred to an aqueous solution of an immunogenic carrier, usually a protein such as keyhole limpet hemocyanin, bovine serum albumin, ovalbumin or the like as well as polysaccharides modified to introduce free amine functional groups, or synthetic polymers such as dextrans, sepharoses, latex or the lik