Stabilization by host cell components and Mg2+ of the neutralization epitopes of poliovirus.

When type 1 poliovirions were extracted from infected HeLa cells and heated at 56 degrees C in the presence of 1 mM-Mg2+, RNA-free, pluri-antigenic particles were formed. These particles possessed neutralization epitopes as well as epitopes associated with H antigen and with the isolated capsid protein VP3. The heating caused the formation of exclusively H antigenic particles when the Mg2+ concentration was 10(-4) M or lower, or when the virus was further purified in order to remove remaining cellular components. The ability of purified virus to form pluri-antigenic particles upon heating could be restored by incubation at 37 degrees C with infected cell extract.