A self-complementary recombinant adeno-associated virus vector coding for an anchorless prion protein carrying the V127 mutation extends survival

Introduction: Current gene therapies for neurological conditions face the challenge that they reach only a small percentage of brain cells in non-human primates or humans. The V127 mutation in the human prion gene (PRNP) is protective against human prions even when expressed at sub-stoichiometric levels.

Objectives: We set out to explore whether disseminating an anchorless prion protein (PrP) harbouring the protective V127 residue across the brain could enhance survival in mice infected with prion disease, using a strategy we refer to as ‘enhanced cross-correction’ (ECC).

Methods: In this pilot study in mice, we prion-inoculated bank vole knock-in mice and tested if transduction with a vector coding for BvPrnp^V127 confers protection. Next to GPI-anchored PrP^V127, we tested if the reduced N-glycosylation observed with anchorless BvPrnp^V127ΔGPI, along with its improved half-life and brain-wide spread, can further enhance the protective capacity of V127 through ECC.

Results/Discussion: Prion-infected mice whose therapeutic payload coded for BvPrnp^V127ΔGPI survived longer than non-protected control mice or mice transduced with a vector coding for anchored BvPrnp^V127. A deep proteomic dive revealed that BvPrnp^V127ΔGPI slowed perturbations to the proteome observed in late-stage RML prion disease. Our analysis captured details of synaptic decay and depletion of proteins in proximity to PrP that may have value for diagnosis or as biomarkers.

Conclusion: This pilot implementation of ECC led to limited survival extension despite high expression of the therapeutic payload. We will discuss strategies and opportunities for how these limits may be overcome to harness the full therapeutic potential of ECC.