The concentration of poliovirus antigens for D-antigen determination.

A study was made of the concentration procedures which are necessary in order to determine the D-antigen content of poliomyelitis vaccines by means of the gel-diffusion method. The most suitable methods were considered to be the aluminium-phosphate method developed by Fantes, and ultrafiltration. The AlPO(4) method was found to be superior in precision to ultrafiltration, but the latter was more convenient for small samples. The AlPO(4) method usually gave about 10%-20% lower D-antigen values than the filtration method, probably owing to incomplete elution of antigen from the precipitate.A two-step concentration procedure involving AlPO(4) precipitation followed by ultrafiltration was employed for determining the D-antigen content of combined and/or adsorbed vaccines.The importance of the different variables which occur in D-antigen determination by these methods is discussed.