prions

[Joao Vasconcelos Costa]

Martin Cann wrote:
> 
> In article <316B77D5.7FEC at pen.gulbenkian.pt>, jcosta at pen.gulbenkian.pt wrote:
> 
> > It seems well established that prions "replicate" in the spleen and =
> >
> > other lymphoid organs before reaching the central nervous system. If
> > we accept the prion model, this should mean that the PrP gene is normal-
> > ly expressed in those organs. However, I don't remember having ever read
> > any paper on the expression of PrP genes in other tissues than the =
> >
> > nervous tissues. Does someone know such studies?
> >
(...)
> 
> I can't think of any studies that show that the agent actually replicates
> in the spleen on its way to the CNS.  Some of the old Scrapie pathology
> papers by Dickinson, Kimberlin and the crew probably cover this ground.
> The mode of transmission to the CNS, as I recall from some of this work,
> is that the agent uses the Splanchnic Nerve Expressway.  As you probably
> know, however, cutting the splanchnic nerve or splenectomy will only
> increase the incubation period of the disease and will not affect the
> overall disease process and pathology.
> 
(...)

Eklund et al. (1967). J. Inf. Dis., 117:15-22
Eklund et al. 81969). J. Am. Vet. Med Assoc., 155:2094-2099

Mice were inoculated ic with 10^5.7 LD50 of scrapie agent. Infectivity 
in spleen:
1 week p.i. - 10^5 (uptake of inoculum)
2 weeks - no infectivity detected
4 weeks - 10^7.2 

Isn't this replication? These papers are rather old but I don´t know
any more recent paper contradicting these results. Of course, they do
not mean obligatory that the situation in natural infection of sheep or 
in BSE is the same.

Joao

-- 
*****   JOAO VASCONCELOS COSTA, MD, PhD
*****   Instituto Gulbenkian de Ciencia - Oeiras, Portugal
*****   mailto:jcosta at pen.gulbenkian.pt
*****   http://www.pen.gulbenkian.pt/v2/jvc.html