PRNP and infection: This mouse line over-expresses ovine VRQ PrP (containing amino acids VRQ at positions 136, 156 and 171 respectively) and whilst conventional inbred wild type mice are refractory to infection by atypical/Nor98 scrapie isolates, tg338 mice are highly sensitive and replicate the PrPSc molecular phenotype that is seen in small ruminants with atypical/Nor98 scrapie [47].