The role of human leukocyte antigen matching in the development of multiethnic "haplobank" of induced pluripotent stem cell lines.

Among the tools of regenerative medicine, induced pluripotent stem cells (iPSCs) are interesting because the donor genotype can be selected. The construction of banks of iPSC cell lines selected from human leukocyte antigen (HLA) homozygous donors has been proposed to be an effective way to match a maximal number of patients receiving cell therapy from iPSC lines. However, what effort would be required to constitute such a bank for a worldwide application has remained unexplored. We developed a probabilistic model to compute the number of donors to screen for constituting banks of best-chosen iPSC lines with homozygous HLA haplotypes (haplobanks) in four ancestry backgrounds. We estimated what percentage of the patients would be provided with single HLA haplotype matched cell lines. Genetic diversity leads to different outcomes for the four sets in all terms. A bank comprising iPSC lines representing the 20 most frequent haplotypes in each population would request quite different number of donors to screen, between 26,000 for European Americans and 110,000 for African Americans. It would also match different fractions of the recipient population, namely, more than 50% of the European Americans and 22% of African Americans. Conversely, a bank comprising the 100 iPSC lines with the most frequent HLA in each population would leave out only 22% of the European Americans, but 37% of the Asians, 48% of the Hispanics, and 55% of the African Americans. The constitution of a haplobank of iPSC lines is achievable through a large-scale concerted worldwide collaboration.