Acute cellular uptake of abnormal prion protein is cell type and scrapie strain independent.

Transmissible spongiform encephalopathies (TSEs) are fatal neurodegenerative diseases that include Creutzfeldt-Jakob disease, bovine spongiform encephalopathy and sheep scrapie.

TSE disease pathology and mechanisms within the central nervous system (CNS) of an infected host largely remains unclear.

At the cellular level, the uptake of protease resistant prion protein (PrP-res), which strongly correlates with infectivity and is a valid marker for TSE infection, is one of the earliest events that must occur during TSE infection.

Given the difficulty of clearly distinguishing input PrP-res from either PrP-res or protease-sensitive PrP (PrP-sen) made by the cell, the uptake of PrP-res from an infectious inoculum into the host cell remains a poorly understood process.

Through the development of a novel assay to exclusively detect input PrP-res we hypothesized that the acute infection of cells by PrP-res is mediated through general processes such as endocytosis, whereas internalization, retention, and propagation of PrP-res are dictated by specific characteristics of both the host cell and PrP-res.

Using PrP-res tagged with a unique epitope to the mouse monoclonal antibody 3F4, we developed a detection system to specifically follow the acute cellular uptake of PrP-res.

Mouse neural and fibroblast cells were exposed to three different mouse scrapie strains and PrP-res from the inoculum monitored.

For all strains, PrP-res uptake was rapid and independent of both cellular prion protein expression and cell type.

However, only 30%-40% of the cells were able to internalize PrP-res and PrP-res aggregate size influenced PrP-res uptake.

Furthermore, infectious brain homogenate PrP-res was taken up more efficiently then PrP-res in either microsome or partially purified preparations. Our results suggest that PrP-res aggregate size, the PrP-res microenvironment, and/or host cell-specific factors can all influence whether or not a cell takes up PrP-res following exposure to TSE infectivity.