Isoproterenol infusion enhances composition and function of G-CSF mobilized allogeneic peripheral blood hematopoietic cell grafts

Background: Graft-versus-host disease (GvHD) and relapse remain critical challenges in allogeneic hematopoietic cell transplantation (alloHCT). Graft composition is pivotal, with naïve T cells increasing GvHD risk and NK cells improving graft-versus-leukemia (GvL) effects. Acute beta-adrenergic receptor activation mobilizes effector lymphocytes, favorably altering circulating immune cell composition. This study investigated whether infusing the non-selective beta-agonist isoproterenol (ISO) after granulocyte colony-stimulating factor (G-CSF) mobilization enhances peripheral blood hematopoietic cell (PBHC) graft composition and outcomes. Methods: Ten healthy volunteers received a 20-minute ISO infusion before and after five days of G-CSF hematopoietic cell mobilization. G-CSF and G-CSF + ISO mobilized PBHCs were phenotyped and assessed for in vitro cytotoxicity. NSG leukemia-bearing mice were injected with G-CSF or G-CSF + ISO mobilized PBHCs and monitored for GvHD, tumor burden, and overall survival. Results: After G-CSF mobilization, ISO increased the numbers of CD34 + cells in the blood and favorably altered graft composition, increasing NK (9.5% to 27.9%) and TCR-γδ T cells (5.0% to 7.5%) while reducing naïve CD4 (18.1% to 11.2%) and CD8 (8.9% to 5.8%) T cells. Effector lymphocytes mobilized by G-CSF + ISO, particularly effector-memory CD8 + T-cells and NK-cells, exhibited upregulated genes and enriched gene sets linked to anti-tumor activity (e.g. NKG7, GZMB, NK cells cytotoxicity). This resulted in an 8-fold increase in cytolysis against the K562 leukemia cell line compared to PBHC mobilized by G-CSF only. In xenogeneic mice, G-CSF + ISO grafts reduced GvHD, extended survival, and improved GvL effects, with 42% of mice surviving at day 40 compared to 21% for G-CSF grafts. Conclusions: ISO infusion post-G-CSF mobilization favorably enhances graft composition, mitigates GvHD, prolongs survival, and augments GvL effects. Our findings suggest that acute systemic beta-adrenergic receptor activation could be a valuable strategy to enhance outcomes in alloHCT.