Résumé
Propagation of the agents responsible for transmissible spongiform encephalopathies (TSEs) in cultured cells has been achieved for only a few cell lines. To establish efficient and versatile models for transmission, we developed neuroblastoma cell lines overexpressing type A mouse prion protein, MoPrP
C
-A, and then tested the susceptibility of the cells to several different mouse-adapted scrapie strains. The transfected cell clones expressed up to sixfold-higher levels of PrP
C
than the untransfected cells. Even after 30 passages, we were able to detect an abnormal proteinase K-resistant form of prion protein, PrP
Sc
, in the agent-inoculated PrP-overexpressing cells, while no PrP
Sc
was detectable in the untransfected cells after 3 passages. Production of PrP
Sc
in these cells was also higher and more stable than that seen in scrapie-infected neuroblastoma cells (ScN2a). The transfected cells were susceptible to PrP
Sc
-A strains Chandler, 139A, and 22L but not to PrP
Sc
-B strains 87V and 22A. We further demonstrate the successful transmission of PrP
Sc
from infected cells to other uninfected cells. Our results corroborate the hypothesis that the successful transmission of agents ex vivo depends on both expression levels of host PrP
C
and the sequence of PrP
Sc
. This new ex vivo transmission model will facilitate research into the mechanism of host-agent interactions, such as the species barrier and strain diversity, and provides a basis for the development of highly susceptible cell lines that could be used in diagnostic and therapeutic approaches to the TSEs.