The Purification and Concentration of Influenza-Virus by Means of Alcohol Precipitation

Summary Experiments are reported in which ethyl and methyl alcohol were used to concentrate and partially purify the PR-8, Weiss and Lee strains of influenza-virus under carefully controlled conditions of alcohol-concentration, temperature and pH. Of the two, methanol was found to be superior since the optimal concentration is of broader range and less denaturation of viral protein is encountered than with ethanol. The data indicate that methanol-precipitation under controlled conditions produces no virus-denaturation nor loss of activity as judged by CCA activity, infectivity titers in chick-embryos or immunizing potency of killed vaccines for mice. On the contrary, based on the CCA activity of the starting material, yields of virus equal to or exceeding 100 per cent are obtained. The methanol-precipitation method is readily applicable to the concentration and purification of influenza-virus using either the bucket, angle head or Sharples continuous-flow types of centrifuges. The method is particularly valuable from the standpoint of producing vaccines on a large scale since it may be combined readily with the Sharples centrifuge method and thus effect great savings in man and machine hours. Preliminary experiments also show that the method may have wide application in the concentration and purification of other viral and rickettsial agents.