Know more

Our use of cookies

Cookies are a set of data stored on a user’s device when the user browses a web site. The data is in a file containing an ID number, the name of the server which deposited it and, in some cases, an expiry date. We use cookies to record information about your visit, language of preference, and other parameters on the site in order to optimise your next visit and make the site even more useful to you.

To improve your experience, we use cookies to store certain browsing information and provide secure navigation, and to collect statistics with a view to improve the site’s features. For a complete list of the cookies we use, download “Ghostery”, a free plug-in for browsers which can detect, and, in some cases, block cookies.

Ghostery is available here for free:

You can also visit the CNIL web site for instructions on how to configure your browser to manage cookie storage on your device.

In the case of third-party advertising cookies, you can also visit the following site:, offered by digital advertising professionals within the European Digital Advertising Alliance (EDAA). From the site, you can deny or accept the cookies used by advertising professionals who are members.

It is also possible to block certain third-party cookies directly via publishers:

Cookie type

Means of blocking

Analytical and performance cookies

Google Analytics

Targeted advertising cookies


The following types of cookies may be used on our websites:

Mandatory cookies

Functional cookies

Social media and advertising cookies

These cookies are needed to ensure the proper functioning of the site and cannot be disabled. They help ensure a secure connection and the basic availability of our website.

These cookies allow us to analyse site use in order to measure and optimise performance. They allow us to store your sign-in information and display the different components of our website in a more coherent way.

These cookies are used by advertising agencies such as Google and by social media sites such as LinkedIn and Facebook. Among other things, they allow pages to be shared on social media, the posting of comments, and the publication (on our site or elsewhere) of ads that reflect your centres of interest.

Our EZPublish content management system (CMS) uses CAS and PHP session cookies and the New Relic cookie for monitoring purposes (IP, response times).

These cookies are deleted at the end of the browsing session (when you log off or close your browser window)

Our EZPublish content management system (CMS) uses the XiTi cookie to measure traffic. Our service provider is AT Internet. This company stores data (IPs, date and time of access, length of the visit and pages viewed) for six months.

Our EZPublish content management system (CMS) does not use this type of cookie.

For more information about the cookies we use, contact INRA’s Data Protection Officer by email at or by post at:

24, chemin de Borde Rouge –Auzeville – CS52627
31326 Castanet Tolosan CEDEX - France

Dernière mise à jour : Mai 2018

Menu Logo Principal AgroParisTech Université Paris-Saclay


GABI : Génétique Animale et Biologie IntégrativeUnité Mixte de Recherche INRA - AgroParisTech

New clue towards understanding why prion strain virulence varies depending on which cells are infected

Prion strains are more or less virulent depending on the population of cells they infect
The reason for these different virulence levels remains largely unknown. Researchers at INRA recently took a decisive step closer to explaining these variations. They observed that certain strains were favoured over others depending on the level of PrP protein, which forms the substrate of brain cells in mice. This research, published in the 23 January 2017 edition of Nature Communications, provides new clues to understanding why each prion strain targets specific cells in the nervous systems of mammals

Prions are definitely the most mysterious pathogens in the living world. Bereft of genetic matter, they are composed of a single, abnormally replicated protein which ‘recruits’ other proteins by transferring this deviant conformation. Diseases caused by prions are especially common in ruminants: cows, sheep, goats and deer. But they can also cause human diseases such as Creutzfeldt-Jakob disease, Kuru and Fatal familial insomnia.

As is the case with bacteria and viruses, there are several strains of prions. The sequencing of their component amino acids is the same, but their three-dimensional structure differs. Each strain has its own characteristics: the incubation period, virulence, symptoms triggered, and the ability to cross the species barrier varies from one strain to another. Furthermore, certain strains are better than others at infecting certain brain regions or cell populations. So while some prions can infect non-nervous tissue, such as lymphatic tissue, others cannot.

Currently, it is unknown why activity differs depending on the cells infected. It is one of the questions that INRA teams are trying to answer. To study the problem, they created several transgenic mouse lines with ovine PrP protein expression. Prions target this protein, and change its conformation upon contact with the pathogen. Once its structure has been modified, it accumulates in brain cells, with fatal consequences. The mouse lines were designed so that PrP expression levels differed in each line. As a result, PrP concentration in certain lines was similar to that found in a healthy animal, while in the others, levels were ten times higher.

The researchers then infected these mice with a sample taken from a sheep with scrapie (a prion-caused disease). This isolate was found to contain several prion strains. Results show that certain strains were more often found in mouse lines with high levels of PrP, and less common in lines with a low concentration of this protein. Therefore, the virulence of each strain varies depending on the quantity of substrate present.

This new finding raises another question: is the ‘preference’ of certain strains for certain brain cells the result of PrP concentration levels in these cells? If so, the research has identified a potential factor in the increase or slowdown of prion activity. It will also shed light on the question of how prion strains naturally evolve, on which INRA teams will now focus their research.


Annick Le Dur, Thanh Lan Laï, Marie-George Stinnakre, Aude Laisné, Nathalie Chenais, Sabine Rakotobe, Bruno Passet, Fabienne Reine, Solange Soulier, Laetitia Herzog, Gaëlle Tilly, Human Rézaei, Vincent Béringue, Jean-Luc Vilotte, Hubert Laude, Divergent prion strain evolution driven by PrPC expression level in transgenic mice. ¶Nature Communications. 14170

See also

... Press releases Inra

Scientific contact

  • Hubert Laude Molecular Virology and Immunology Research Unit
  • Jean-Luc Vilotte Animal Genetics and Integrative Biology Unit

Presse relations

Associated division

  • Animal Health
  • Animal Genetics

Associated centre

  • Jouy-en-Josas