Dense Particles and Slow Sedimenting Particles Produced by Ultraviolet Irradiation of Poliovirus

Abstract

Low doses of UV radiation rapidly inactivate poliovirus, and the virus is progressively converted into dense particles (DP) of buoyant density 1.44 g/ml in CsCl. The DP are structurally and antigenically related to standard virus (N-antigen), i.e., they are indistinguishable from virus in their RNA and protein content and in their sedimentation properties. There is no difference in reactivity of the structural proteins of virus and DP with the monofunctional reagent [3H]N-succinimidyl propionate (3H-NSP). DP differ from virus in that their capsids are permeable to several ions, and they can be degraded by RNase and protease. Increasing the radiation dose causes a successive transformation of DP into 105S slow-sedimenting particles (SSP). The SSP are antigenically related to 76S artifical empty capsids (AEC) or H-antigen, but they differ physically and structurally from them. The SSP have a higher S value than AEC and contain all the capsid proteins, including VP4, and the RNA, both of these macromolecules being absent from AEC. Evidently, transformation from N- to H-antigenicity by UV radiation does not require release of RNA and VP4. Conversion of virus particles to SSP correlates with altered reactivity of VP2 and to a lesser extent VP1 and VP3, with the monofunctional reagent 3H-NSP.