Simple Method for Obtaining Antisera in a Dry State

Abstract

Several reports deal with the preparation of dry antisera. Evaporation in vacuo and precipitation in the cold with alcohol or acetone are the methods most used. According to reports dealing with the latter method, the low temperature has been assumed to be the factor preventing denaturation and loss of antibody activity. We have found that the concentration of the organic precipitant is an equally important factor. There exists a critical concentration of the organic solvents methyl, ethyl and propyl alcohol and acetone, in the range of 60% to 75% concentration at which denaturation of serum proteins is maximal. As the concentration is increased from about 75% the degree of denaturation is decreased until at final concentrations of 90% or above serum proteins can be precipitated by these organic solvents at room temperatures without loss in solubility or antibody activity. Applying this phenomenon the following method has been used to prepare dry immune sera. To 10 or more (but not less) volumes of acetone add slowly with shaking one volume of the serum. Collect the precipitate on a filter, wash once with acetone followed by 3 washings with anhydrous ether, the precipitated mass being stirred with a wooden spatula after each ether addition. Approximately 5 volumes of ether to each original volume of serum is required for each washing. The final white mass is spread out on the filter paper and placed in the 37°C. incubator for about one hour. The resulting dry mass is readily pulverized with the wooden spatula to an extremely light, white, fluffy powder. This powder is slowly (due to slow wetting) though completely soluble in distilled water or physiological sodium chloride solution. There has been detected no loss in agglutinating activity, hemolytic activity or antitoxin content.