Fig. 5

A MR100-based assay can differentiate between prion-infected and normal brain homogenates without proteinase K digestion. a Schematic description of the RCA protocol to test brain homogenates without PK digestion. Brain tissues were freshly homogenized in microbead-containing tubes. Normal brain homogenates (NBH) or prion-infected brain homogenates (IBH) were incubated with MR100 for 1 h, at room temperature, leading to a precipitation of PrP isoforms. After a short centrifugation step, the pellet with MR100 (orange tube) concentrates PrP isoforms, whereas no pellet is detectable with DMSO. b Comparison of DMSO, P30 and MR100 precipitation capabilities using the RCA protocol. Fifty μL of 10 % 22 L infected brain homogenates were diluted in 300 μL of PBS/2 % sarcosyl and incubated using either 1.5 mM of P30 or MR100 or an equivalent volume of the solvent alone (DMSO), at room temperature for 1 h. Then, samples were centrifuged at 8000 g for 5 min. Supernatants (S) were collected and 30 μL of each supernatant was mixed with an equivalent volume of 2X loading buffer. Pellets (P) were resuspended in 30 μL PBS/2 % Sarcosyl, and mixed with an equal volume of 2X loading buffer. Thirty microliters of each sample were loaded on 12 % Bis-Tris gels (Criterion, Biorad) and immunoblotting was carried out with the SAF mix according to standard procedures [16]. The samples (S/P) were analyzed by western blotting using SAF mix anti-PrP antibodies. c Comparison of infected versus non-infected brain homogenates processed with the RCA protocol. Fifty microliters of 10 % freshly homogenized brain tissues from normal (NBH) or 22 L prion-infected (IBH) mice were processed according to the RCA protocol described in A and B. Thirty microliters of supernatant (S) or pellet (P) were loaded on 12 % Bis-Tris gels (Criterion, Biorad) and immunoblotting was carried out with the SAF mix as described above. Molecular masses (20–75 kDa) are indicated on the left side of the panels