Capsid and RNA stabilisation of the oral polio vaccine

The oral polio vaccine is the least stable vaccine of the common childhood vaccines. Two different inactivation mechanisms are responsible for the thermolability of the vaccine, i.e. denaturation of the viral capsid and degradation of the viral RNA within the capsid. Pirodavir, a capsid-binding compound, inhibits the viral capsid thermodenaturation. In this paper we show that deuterium oxide is able to stabilise the viral RNA against thermodegradation and that a combination of pirodavir and deuterium oxide leads to an additive effect indicating that both stabilisers work indeed on different inactivation mechanisms. Furthermore, it is shown that the variation in thermostability of the different vaccine strains is due to the different thermostability of their capsids.