Prion diseases are rare conditions characterized by the degeneration of the central nervous system and the formation of infectious aggregates of a specific protein known as the prion protein (PrP).
In the acquired forms that arise from oral or intravenous contamination, the prions first replicate in the lymphoid organs (lymph nodes and spleen) before invading the central nervous system. Researchers at the CEA-Jacob have identified a new mode of prion transmission using a non-human primate infected with the vCJD/BSE prion strain as an experimental model. More than seven years of silent incubation after inoculating a subject’s finger with an infectious specimen, the first behavioral and neurological signs have been observed. Biochemical studies confirmed the presence of the abnormal prion protein PrPd in the central nervous system. Histopathological analysis revealed the presence of lesions specific to prion diseases and a signature unique to vCJD.
Novel deposits of PrPd were found in Schwann cells (glial cells responsible for axon myelination) of the median nerve, satellite cells, and ganglion cells of the dorsal root ganglia. On the other hand, all lymphoid organs were devoid of PrPd, in contrast to individuals exposed orally or intravenously. The researchers therefore proposed a model of strict neurotransmission after contamination in a highly innervated area, which is at first slow and progressive along the infected nerve (step-by-step, via the Schwann cells) until the dorsal root ganglion relay (at the level of the spinal cord), and then stronger in the spinal cord and central nervous system, after the neuronal damage.