Induction of cytotoxic T lymphocyte and antibody responses to enhanced green fluorescent protein following transplantation of transduced CD34(+) hematopoietic cells

Genetic modification of hematopoietic stem cells often results in the expre ssion of foreign proteins in pluripotent progenitor cells and their progeny . However, the potential for products of foreign genes introduced into hema topoietic stem cells to induce host immune responses is not well understood . Gene marking and induction of immune responses to enhanced green fluoresc ent protein (eGFP) were examined in rhesus macaques that underwent nonmyelo ablative irradiation followed by infusions of CD34(+) bone marrow cells tra nsduced with a retroviral vector expressing eGFP, CD34(+) cells were obtain ed from untreated animals or from animals treated with recombinant human gr anulocyte colony-stimulating factor (G-CSF) alone or G-CSF and recombinant human stem cell factor. Levels of eGFP-expressing cells detected by flow cy tometry peaked at 0.1% to 0.5% of all leukocytes 1 to 4 weeks after transpl antation. Proviral DNA was detected in 0% to 17% of bone marrow-derived col ony-forming units at periods of 5 to 18 weeks after transplantation. Howeve r, 5 of 6 animals studied demonstrated a vigorous eGFP-specific cytotoxic T lymphocyte (CTL) response that was associated with a loss of genetically m odified cells in peripheral blood, as demonstrated by both flow cytometry a nd polymerase chain reaction. The eGFP-specific CTL responses were MHC-rest ricted, mediated by CD8(+) lymphocytes, and directed against multiple epito pes, eGFP-specific CTLs were able to efficiently lyse autologous CD34(+) ce lls expressing eGFP, Antibody responses to eGFP were detected in 3 of 6 ani mals. These data document the potential for foreign proteins expressed in C D34(+) hematopoietic cells and their progeny to induce antibody and CTL res ponses in the setting of a clinically applicable transplantation protocol. (Blood, 2001;97:1951-1959) (C) 2001 by The American Society of Hematology.