Mice Treated Subcutaneously with Mouse LPS-Converted PrP(res) or LPS Alone Showed Brain Gene Expression Profiles Characteristic of Prion Disease

Previously, we showed that bacterial lipopolysaccharide (LPS) converts mouse PrP(C) protein to a beta-rich isoform (moPrP(res)) resistant to proteinase K. In this study, we aimed to test if the LPS-converted PrP(res) is infectious and alters the expression of genes related to prion pathology in brains of terminally sick mice. Ninety female FVB/N mice at 5 weeks of age were randomly assigned to 6 groups treated subcutaneously (sc) for 6 weeks either with: (1) Saline (CTR); (2) LPS from Escherichia coli 0111:B4 (LPS), (3) one-time sc administration of de novo generated mouse recombinant prion protein (moPrP; 29-232) rich in beta-sheet by incubation with LPS (moPrP(res)), (4) LPS plus one-time sc injection of moPrP(res), (5) one-time sc injection of brain homogenate from Rocky Mountain Lab (RLM) scrapie strain, and (6) LPS plus one-time sc injection of RML. Results showed that all treatments altered the expression of various genes related to prion disease and neuroinflammation starting at 11 weeks post-infection and more profoundly at the terminal stage. In conclusion, sc administration of de novo generated moPrPres, LPS, and a combination of moPrP(res) with LPS were able to alter the expression of multiple genes typical of prion pathology and inflammation.