Prion 2024 Conference Abstracts

Aims:To determine the structures of infectious brainderived prions to understand the molecular foundations of prion propagation and strain variation Materials and Methods: Prion fibril purification from brain (mouse and deer); bioassays of purified fibrils; real time quaking induced conversion (RT-QuIC) assays; negative stain transmission electron microscopy (EM); cryo-electron tomography; cryo-EM; singleparticle analysis; and 3D image reconstruction.Results: SDS-PAGE and immunoblots of purified preparations showed high purity with respect to PrP content.Negative stain EM showed predominantly fibrillar morphology with mixtures of isolated, laterally associated, and crossed fibrils.Cryo-electron tomography showed that 263k, aRML and a22L rodent prion fibrils had left-handed twists.We also observed globules of unknown composition along the sides of some of the fibrils.Structural details of prion fibrils were obtained by single particle acquisitions and helical reconstruction.So far, all brain-derived prion fibrils parallel in-register intermolecular -sheets (PIRIBS)-based architectures.The rodent prions have a single PrP monomer spanning the fibril cross-section with N-, middle, and disulphide arch motifs and a steric zipper near the N-terminus of the ordered core.However, conformational differences within these motifs arches and other regions distinguish these strains, including the a22L and aRML prion strains isolated from the same genotype of mouse.We currently have slightly lower-resolution data on a CWD prion.Clearly, it has a PIRIBS architecture and both similarities and differences to the known rodent prion strains.However, like the rodent scrapie strains, the CWD core structure is much larger than that of human GSS F198S prion fibrils.Conclusions: The prion strains that have solved to date each have unique conformational templates on the fibril ends that dictates the fold of incoming PrP monomers as the prions grow, even when isolated from hosts of the same genotype.Our findings are providing structural insights into the molecular bases of prion strain propagation and transmission barriers.Precise knowledge of prion structures should also help in drug discovery and the design vaccine against prion diseases of animals and humans.