Mouse-Protective Potency Assay of Typhoid Vaccine: As Performed at the Army Medical Service Graduate School

Abstract

The need for an efficient, practical laboratory method for determining the potency of tvphoid vaccines long has been recognized by immunologists concerned with the development, production, and assay of the product. The need in relation to production and control in routine manufacture of typhoid vaccine is mainly for a testing method which will permit the ready demonstration that an individual lot, or successive lots, of vaccine equal or exceed an established level of potency. Researchers, on the other hand, require an assay method which, in addition to the foregoing, permits quantitative estimation of potency, i. e., which permits numerical expression of potency in absolute or relative terms with an estimable degree of uncertainty. Only by the use of such a method is the investigator enabled to detect or evaluate differences or changes in potency as effected by experimental treatments or conditions of interest. Methods early used in the determination of the potency of typhoid vaccines were based upon parenteral administration of the products to rabbits and subsequent in viro determination of the agglutinin response (15), or the actual protection of such immunized rabbits against subacute infection following injection of living, virulent Salmonella typhosa (18). It is beyond the scope of this report to discuss or criticize these tests in detail and it is considered sufficient to state that such methods have proved to be neither adequately definitive nor reproducible to warrant their continued use. Investigation and establishment by Siler and his associates at the Army Medical School (22) of the mouse-protection test for assessing the antibody response of humaDs to typhoid immunization stimulated

An Adaptation of Quality Control Chart Methods to Bacterial Vaccine Potency Testing

“…Potency assay procedure. The assay procedure employed was an active-immunity mouse-protection potency test based on the use of graded immunizing doses and a constant challenge dose (Batson, Brown, and Oberstein, 1951). In each instance, only 2 dilutions of vaccine, differing by a 10-fold increment, were administered intraperitoneally as a single dose in a total volume of 0.5 ml.…”