Poliomyelitis virus is precipitated from virus-containing fluids by adding nucleic acid and adjusting the pH to 1 to 4. The polio virus may be purified by digestion with ribonuclease and/or desoxyribonuclease followed by digestion with papain or fisin, preferably activated with cysteine, to recover pure poliovirus which may be employed in the preparation of vaccines. The digestion takes place in buffered solution and the products of the digestion may be removed by dialysis, ultracentrifugation or precipitation of virus by an alcohol. Nucleic acid, e.g. yeast nucleic acid, is added in a quantity sufficient to provide at least the equivalent of 2.5 mg. of purified nucleic acid per ml. of virus-containing fluid. Vaccines may be prepared by inactivating the purified poliovirus.
展开▼
