Nihata A et al., PNAS - This PNAS study describes the development of EKV, a humanized dividing cell line that propagates bona fide sporadic CJD (sCJD) prions, and the Human Prion Assay (HPA), a cell-based method that quantifies infectivity with sensitivity comparable to transgenic mouse bioassay while enabling rapid therapeutic screening. Key terms: sCJD, EKV cells, Human Prion Assay, prion infectivity, anti-PrP antibody.

Study Highlights:
The authors engineered EKV cells by reconstituting CAD5 PrP-knockdown cells with human PrP (V129) and iterative single-cell cloning to enrich prion susceptibility. EKV cells propagate de novo infectious sCJD prions that reproduce strain-specific pathology when transmitted to humanized Tg152c mice. The Human Prion Assay (HPA) using EKV cells quantifies sCJD infectivity across a wide dynamic range with sensitivity comparable to mouse bioassay but in weeks rather than years. Persistently infected iEKV clones can be cured by the anti-PrP monoclonal antibody ICSM18, validating the platform for high-throughput therapeutic screens.

Conclusion:
EKV cells and the HPA provide a renewable, scalable, and faster alternative to animal bioassays for measuring authentic human sCJD infectivity and for screening and validating anti-prion therapeutics, while retaining strain-specific biological properties.

Music:
Enjoy the music based on this article at the end of the episode.

Article title:
A scalable, dividing cell model for the robust propagation and quantification of human sporadic Creutzfeldt–Jakob disease prions

First author:
Nihata A

Journal:
PNAS

DOI:
10.1073/pnas.2600341123

Reference:
Nihata A, Collinge J, Linehan J, Brandner S, Mead S, Schmidt C, Rayner MLD, Jat PS, Arora P, et al. A scalable, dividing cell model for the robust propagation and quantification of human sporadic Creutzfeldt–Jakob disease prions. PNAS. 2026;123(27):e2600341123. doi:10.1073/pnas.2600341123.

License:
This episode is based on an open-access article published under the Creative Commons Attribution 4.0 International License (CC BY 4.0) – https://creativecommons.org/licenses/by/4.0/

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Episode link: https://basebybase.com/episodes/ekv-human-prion-assay

QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-07-09.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Substantive audit focused on EKV cell development and validation, in vitro propagation of human sCJD prions, HPA implementation and benchmarking against mouse bioassay, drug-screening demonstration, and documented limitations (codon 129 mismatch, occult infectivity).
- transcript topics: Prion biology and strain concepts (PRNP codon 129 polymorphism); Historical barriers to human prion culture and need for cell-based infectivity assays; Engineering EKV cells: CAD5-KDB3, human PrP V129, mouse signal peptide; Iterative single-cell cloning and enrichment to EKV; Infectivity validation via transmission to Tg152c mice; Development and validation of the Human Prion Assay (HPA)

QC Summary:
- factual score: 10/10
- metadata score: 10/10
- supported core claims: 6
- claims flagged for review: 0
- metadata checks passed: 4
- metadata issues found: 0

Metadata Audited:
- article_doi
- article_title
- article_journal
- license

Factual Items Audited:
- EKV cells propagate de novo infectious human sCJD prions in culture
- Infectivity validated by transmission to Tg152c mice; 100% (18/18) succumbed to prion disease with incubation ~251 days
- Human Prion Assay (HPA) detects sCJD infectivity with titer ~5.66 logTCIU50/g, comparable to mouse bioassay ~5.88 logLD50/g
- HPA achieves detection across type 2 and 3 prion strains, with MM prions less efficiently propagated due to codon 129 mismatch
- Persistently infected iEKV lines (e.g., 1G2, 1E10) maintained infection over ≥15 passages; ICSM18 cures infection in iEKV
- Occult infectivity observed: KDB3 control exposed to brain homogenate still produced a single prion disease case after six passages

QC result: Pass.