Influence of different ionic and pH environments on structural alterations of poliovirus and their possible relation to virus uncoating.

Poliovirus eclipse products were totally precipitated from infected HeLa cells after different times of infection by using TCA, suggesting that cellular enzymic digestion of parental proteins was not involved in virus uncoating. In an investigation of poliovirus thermal stability in vitro, progressive degradation of native virus into 80S empty capsids occurred upon incubation at 37 degrees C in a buffer of low ionic strength containing 20 mM-Tris-HCl pH 7.5, whereas in Eagle's medium or in the presence of L cells degradation was very slow. Degradation was faster at alkaline than at acid pH. Furthermore, liberation of the viral RNA was prevented and 135S particles were produced upon treatment of virus at 37 degrees C in 20-mM-Tris-HCl pH 7.5 containing 2 mM-CaCl2. Although the poliovirus receptor is able to induce conformational alterations of the capsid, low ion concentration could contribute to virus uncoating as well.