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Isolation and antigenic characterization of dense particles of swine enteroviruses.

Dense particles (buoyant density in CsCI: 1.45-1.47 g/cm3) were isolated from HeLa cells infected with swine enteroviruses and coxsackievirus type B5. These dense particles had important properties which were different from those of poliovirus and other picornaviruses described previously; for instance, they could be isolated under various conditions of virus growth. The smallest capsid polypeptide, VP4, was not detected by SDS-PAGE analysis. The preparations of dense particles were non-infectious and showed H antigenicity by a modified enzyme immunoassay. Judging from these properties, dense particles might be equivalent to "A particles". These findings suggest that the VP4 polypeptide is responsible for the conformational stabilization of the intact virion.