Although it is possible the protease in human HEK293 cells that cleaves cp-B/2 to cp-A/1 is not the same protease that is responsible for generating the cp-A/1 sized pathologic fragment in human HD brains, the antibody binding characteristics of the cp-A/1 fragment found in HEK293 cells is very similar to that of the pathologic fragment in inclusions [7], [8]. This evidence concerns the gene CPA1 and Huntington disease.