Intracerebral Infusion of Antisense Oligonucleotides Into Prion-infected Mice

Abstract

Mice deficient for the cellular prion protein (PrPC) do not develop prion disease; accordingly, gene-based strategies to diminish PrPC expression are of interest. We synthesized a series of chemically modified antisense oligonucleotides (ASOs) targeted against mouse Prnp messenger RNA (mRNA) and identified those that were most effective in decreasing PrPC expression. Those ASOs were also evaluated in scrapie-infected cultured cells (ScN2a) for their efficacy in diminishing the levels of the disease-causing prion protein (PrPSc). When the optimal ASO was infused intracerebrally into FVB mice over a 14-day period beginning 1 day after infection with the Rocky Mountain Laboratory (RML) strain of mouse prions, a prolongation of the incubation period of almost 2 months was observed. Whether ASOs can be used to develop an effective therapy for patients dying of Creutzfeldt–Jakob disease remains to be established.

Antisense oligonucleotides in therapy for neurodegenerative disorders

“…Reducing protein expression by antisense oligonucleotides was recently also shown as proof-ofprinciple for patients with Creutzfeldt-Jakob disease (CJD) [153]. CJD is caused by a conformational change of the harmless cellular prion protein (PrP c ) into an infectious and pathogenic insoluble isoform scrapie PrP (PrP Sc ) and subsequent deposition of extracellular aggregated prion proteins.…”

“…The infectious PrP Sc has the unique characteristic that it spreads throughout the brain and can be transmitted between people as well as between different species [154]. ICV infusion in PrP Sc infected mice of MOE-PS gapmer antisense oligonucleotides for 14 days resulted in reduced PrP c as well as reduced disease-causing PrP Sc levels [153]. This reduction in disease-causing PrP Sc is probably not due to decreased PrP c , but due to a, yet unknown, anti-prion action of PS modified antisense oligonucleotides [155,156].…”

Prion-Like Propagation of Protein Aggregation and Related Therapeutic Strategies

“…Given the recent work regarding mechanisms of transcellular propagation, treatment strategies may soon be expanded to include extracellular clearance, inhibiting secretion and preventing uptake of pathological protein aggregate seeds. Endogenous expression of PrP is required for the spread of pathology, and decreasing either the endogenous or misfolded form of this protein is a viable treatment strategy [82,83]. Given the current evidence for prion-like spread of the proteins implicated in other neurodegenerative diseases, decreased production may also have special benefit in this regard.…”

“…These molecules have some advantages over RNAi-based approaches, as they are readily modified to improve their stability and decrease their susceptibility to exonuclease degradation, leading to increased longevity in vivo. Specific modifications can also improve their solubility and tissue distribution, which will allow for decreased concentrations to be used in vivo [83,85].…”

“…ASOs were used to decrease PrP in a mouse model of prion disease, and led to a dramatic increase in the length of survival compared to control mice [83]. ASO-mediated decrease of huntingtin protein in a mouse model of Huntington's disease delayed and even reversed pathology.…”