NR AOVD
AU Kretzschmar,H.A.
TI Insights into autocatalysis of PrPres amplification and prion propagation after oral and intra peritoneal inoculation
QU International Conference - Prion diseases: from basic research to intervention concepts - TSE-Forum, 08.10.-10.10.2003, Gasteig, München - Oral sessions OS-13
PT Konferenz-Vortrag
AB
Prions are thought to replicate in an autocatalytic process that converts PrPc into the misfolded PrPsc isoform. Protein misfolding cyclic amplification (PMCA) (Saborio et al., 2001) was used in a serial in-vitro transmission experiment to test this hypothesis. In this set-up we found that newly formed misfolded and PK-resistant PrP (PrPres) catalyzed the structural conversion of PrPc as efficiently as PrPsc seeds, which confirms an autocatalytic PrP misfolding cascade as postulated by the prion hypothesis. However, the autocatalytic formation of PrPres was not paralleled by replication of biological infectivity.
How prions spread to the CNS after uptake by the GI tract is not well understood. Using the intraperitoneal route a crucial role for B lymphocytes and FDCs has been implicated. However, it is quite unclear whether data derived from experiments after intraperitoneal (ip) inoculation can be transferred to the oral route. We aimed to investigate the role of B cells, FDCs and dendritic cells (DC) using a novel mouse model in which mice are infected that are transgenic for dominant negative variants of small GTPases (Th. Brocker, 2003). These inhibitory transgenes are expressed in either DC (CD11c-promoter) or B cells/follicular DC (CD19-promoter). CD19-N17Rac1 low copy mice and CD11c-N17Rac1 mice were inoculated ip and orally. While ip infection resulted in longer survival of transgenic mice, oral infection did not reveal strong differences. From these results it seems that the role of B cells and dendritic cells differs between prion infection after ip and oral inoculation.
Recent findings have indicated that stimulation of innate immunity, which does not seem to be activated in natural prion infection due to the lack of pathogen-associated molecular patterns in this class of novel pathogens, leads to longer survival times (Sethi et al., 2002). We investigated whether the prolongation of survival time is correlated with the induction of anti-prion PrP antibodies. We found a markedly increased anti-PrP seroreactivity in groups that received CpG oligodeoxynucleotides correlating with longer survival times. These findings indicate that immunotherapeutic strategies based on active stimulation of innate immunity lead to a protective humoral immune response after prion infection.
These studies were supported by the Bavarian Prion Research Fund.
AD Hans A. Kretzschmar, LMU Munich, Germany
SP englisch
PO Deutschland