PRNP and scrapie: Differences were seen in relation to the reactivity with the N-terminal antibody P4, which was dependent on PRNP polymorphisms at codon 141: PrPres was detected with this antibody in VV and LL141 sheep, similar to the classical scrapie ovine and caprine control samples, whereas reactivity was reduced in LF141 sheep and greatly reduced or absent in FF141 sheep, similar to the classical BSE control sample.