A NEW WHO INTERNATIONAL REFERENCE REAGENT FOR USE IN POTENCY ASSAYS OF INACTIVATED POLIOMYELITIS VACCINE

Assays of the potency of inactivated poliovirus vaccine require the us e of an appropriate reference reagent. Preparation 91/574 was shown by international collaborative study to be suitable for determination of antigenic content and immunogen!city of inactivated poliovirus vaccin es by in vitro and in vivo assays, respectively.(1.2) The reagent is a trivalent blend of formaldehyde-inactivated monovalent pools of polio virus type 1 (Mahoney), poliovirus type 2 (MEF-1) and poliovirus type 3 (Saukett). Studies by antigen-capture ELISA showed that the componen t monovalent pools contained high titres of D antigen and trace amount s of C antigen. Sucrose gradient analysis showed that the D antigenici ty was almost exclusively associated with 150S virus particles. Low le vels of procapsids (75S particles with D antigenicity) were detected i n the type 1 and 2 monovalent pools. The profile of intact virions and procapsids in 91/574 in sucrose gradients was very similar to PU78-02 , a previously used inactivated trivalent poliovirus vaccine reference . The World Health Organization (WHO) Expert Committee on Biological S tandardization at its 1994 meeting established preparation 91/574 as t he 2nd WHO international Reference Reagent for poliomyelitis vaccine ( inactivated). A potency of 430, 95, 285 D antigen units per ml was ass igned to poliovirus type 1, 2 and 3, respectively. A separate aliquot of this preparation, established by the European Pharmacopeia Commissi on as a Biological Reference Preparation, has an identical assigned ti tre. The 2nd WHO International Reference Reagent 91/574 is intended fo r calibration of secondary reference reagents. (C) 1997 The Internatio nal Association of Biological Standardization.