Characterization of the murine BSE infectious agent

Bovine spongiform encephalopathy (BSE) is a prion-associated disease where the infectious agent is thought to be a host-encoded protein with a proteas e-resistant conformation (PrPSc). Here, data are presented on the solubiliz ation of purified murine BSE material, using guanidine-HCl as a denaturing agent. This treatment led to loss of infectivity, which was partially recov ered on renaturation after dialysis to remove the chaotropic agent. The ren atured product was then fractionated on an isopycnic sucrose-density gradie nt and the fractions were analysed for the presence of PrPSc, nucleic acids and infectivity, It was found that the major part of PrPSc (> 90%) and the endogenous nucleic acids did not contribute towards the formation of infec tious particles on renaturation. Infectivity was distributed in the top thr ee, low-density fractions. Among these, the presence of considerable infect ivity in the fraction of lowest density, with barely detectable PrPSc, is o f particular interest.