Prion infection, transmission, and cytopathology modeled in a low-biohazard human cell line.

Merve Avar,Rita Moos,Daniel Heinzer,Nicolas Steinke,Adriano Aguzzi,Berre Doğançay,Simone Hornemann,Severine Lugan,Olivier Andréoletti,Claudia Cosenza

doi:10.26508/lsa.202000814

Abstract

Transmission of prion infectivity to susceptible murine cell lines has simplified prion titration assays and has greatly reduced the need for animal experimentation. However, murine cell models suffer from technical and biological constraints. Human cell lines might be more useful, but they are much more biohazardous and are often poorly infectible. Here, we describe the human clonal cell line hovS, which lacks the human PRNP gene and expresses instead the ovine PRNP VRQ allele. HovS cells were highly susceptible to the PG127 strain of sheep-derived murine prions, reaching up to 90% infected cells in any given culture and were maintained in a continuous infected state for at least 14 passages. Infected hovS cells produced proteinase K-resistant prion protein (PrPSc), pelletable PrP aggregates, and bona fide infectious prions capable of infecting further generations of naïve hovS cells and mice expressing the VRQ allelic variant of ovine PrPC Infection in hovS led to prominent cytopathic vacuolation akin to the spongiform changes observed in individuals suffering from prion diseases. In addition to expanding the toolbox for prion research to human experimental genetics, the hovS cell line provides a human-derived system that does not require human prions. Hence, the manipulation of scrapie-infected hovS cells may present fewer biosafety hazards than that of genuine human prions.

Highlights

Prions, the causative agent of transmissible spongiform encephalopathies, are devoid of nucleic acids and consist primarily of a protein termed PrPSc
Most of the in vitro models are based on mouse cell lines such as N2a subclone PK1 (Klohn et al, 2003), CAD5, and GT-1/7 (Solassol et al, 2003), which may not reproduce all characteristics of human prions
We isolated a polyclonal cell line, hereafter referred to as “povS” and a monoclonal cell line obtained through limiting dilution and referred to as “hovS”

Summary

Introduction

The causative agent of transmissible spongiform encephalopathies, are devoid of nucleic acids and consist primarily of a protein termed PrPSc. PrPSc cannot be reliably distinguished from its cellular precursor PrPC in living cells, making it impossible to assess prion replication in real time. Cellular models of human prion replication and toxicity are crucial to advancing our understanding of human prion diseases. Most of the in vitro models are based on mouse cell lines such as N2a subclone PK1 (Klohn et al, 2003), CAD5, and GT-1/7 (Solassol et al, 2003), which may not reproduce all characteristics of human prions. With few exceptions (Schatzl et al, 1997), the infection of these cell lines with prions does not result in a measurable pathological phenotype, a finding that limits their usefulness for disease research

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Conclusion