DISCREPANCY BETWEEN INFECTIVITY AND ANTIGENICITY STABILIZATION OF ORAL POLIOVIRUS VACCINE BY A CAPSID-BINDING COMPOUND

Two hundred forty pyridazinamine derivatives were tested for the abili ty to stabilize the antigenicity and infectivity of oral poliovirus va ccine subjected to 45 degrees C for 2 h. Seven compounds stabilized th e antigenicity of all three vaccine strains and neutralized the viral particles in a way that is reversible by dilution. Of these, R 77975 ( pirodavir) was selected for vaccine potency tests. Sabin type 2 and ty pe 3 strains were subjected to 4, 25, 42, and 45 degrees C for 1 week in the presence and absence of R 77975. Although R 77975 particularly stabilized the infectivity of the most thermolabile vaccine strain (Sa bin type 3), the protection did not exceed that of 1 M MgCl2. When vir us was inactivated in the absence of R 77975, the native or N antigeni city changed in H antigenicity. However, in the presence of the capsid -binding compound, N antigenicity was preserved in particles that had lost infectivity.