Transcriptional profiling of peripheral lymphoid tissue reveals genes and networks linked to SSBP/1 scrapie pathology in sheep

Transmissible spongiform encephalopathies (TSEs) are slow and progressive neurodegenerative diseases of humans and animals. The major target organ for all TSEs is the brain but some TSE agents are associated with prior accumulation within the peripheral lymphoid system. Many studies have examined the effects of scrapie infection on the expression of central nervous system (CNS) genes, but this study examines the progression of scrapie pathology in the peripheral lymphoid system and how scrapie infection affects the transcriptome of the lymph nodes and spleen.Infection of sheep with SSBP/1 scrapie resulted in PrPSc deposition in the draining prescapular lymph node (PSLN) by 25 days post infection (dpi) in VRQ/VRQ genotype sheep and 75 dpi in tonsils and spleen. Progression of PrPSc deposition in VRQ/ARR animals was 25 dpi later in the PSLN and 250 dpi later in spleen. Microarray analysis of 75 dpi tissues from VRQ/VRQ sheep identified 52 genes in PSLN and 37 genes in spleen cells that showed significant difference (P ≤ 0.05) between scrapie-infected and mock-infected animals. Transcriptional pathway analysis highlighted immunological disease, cell death and neurological disease as the biological pathways associated with scrapie pathogenesis in the peripheral lymphoid system. PrPSc accumulation of lymphoid tissue resulted in the repression of genes linked to inflammation and oxidative stress, and the up-regulation of genes related to apoptosis.

► PRNP genotype determines progressive lymphoid deposition of PrPSc.
► PrPSc deposition is associated with major changes to lymph node and spleen transcriptome.
► Lymphoid accumulation of PrPSc resulted in repression of inflammation and oxidative stress genes.
► Lymphoid accumulation of PrPSc resulted in up-regulation of apoptosis genes.
► This contrasts to the effects of PrPSc in the CNS.