Transplantation of human peripheral blood stem cells into fetal rhesus monkeys (Macaca mulatta)

Background. Methods for assessing engraftment efficiency have been explored in a primate xenogeneic model of in utero hematopoietic stem cell transpla ntation, Methods, Human peripheral blood stem cells (PBSC) were obtained by leukapheresis from a human male donor after 4 days of administration of re combinant human granulocyte-colony stimulating factor (5 mu g/kg/day). PBSC were enriched for the CD34(+) population with and without T-cell depletion . The resulting mononuclear cells consisted of two cell populations, one th at was stem cell enriched (0.83% CD3(+) cells, 95% CD34(+); group 1) and on e that was stem cell enriched and T-cell depleted (<0,03% CD3(+) cells, 98% CD34(+); group 2), Four fetal monkeys (two per group) received either two or four i,p, injections (similar to 5x10(6) cells/injection) via ultrasound guidance every other day over a 7-day period (gestational days 50, 52, 54, and 56), One fetus in each group also received i.p. recombinant human stem cell factor (25 mu g/kg) and recombinant human granulocyte-colony stimulat ing factor (10 mu g/kg) posttransplant every 10 days from gestational day 6 0-150. Results. Four healthy newborns were delivered at term, and specimens were analyzed by polymerase chain reaction for the human Y chromosome (bir th, monthly to 6 months; blood, marrow, progenitor assays). Polymerase chai n reaction results were positive for all four newborns in all specimens ass essed, and flow cytometric analysis for human CD45 in marrow showed engraft ment ranging from 0.1-1,7%. There was no evidence of graft-versus-host dise ase in any of the animals. Conclusion. These studies show that (1) multilin eage engraftment of human PBSC can be achieved in the fetal rhesus recipien t, (2) the rhesus fetus appears to tolerate relatively high numbers of huma n CD3(+) cells, and (3) healthy chimeric rhesus infants can be delivered at term after multiple in utero procedures.