In vCJD challenged human PrP 200K-expressing transgenic mice Tg23 (data not shown) and Tg49 (Fig. 2i, l), abundant florid plaques were also observed that were indistinguishable from the florid plaques generated in transgenic mice expressing wild-type human PrP 129MM, Tg35 or Tg45 (Asante et al., 2002). This evidence concerns the gene PRNP and variant Creutzfeldt-Jakob disease.