Therapeutic Effect of Combined Cytokines on Nonhuman Primate Model of Severe Haemopoietic Acute Radiation Sickness

Abstract

To evaluate the therapeutic effects of combined administration of recombinant human granulocyte colony-stimulating factor (rhG-CSF), recombinant human thrombopoietin (rhTPO) and recombinant human interleukin-2 (rhIL-2) on radiation-induced severe haemopoietic acute radiation sickness (ARS) in rhesus monkeys, so as to provide experimental evidences for the effective clinical treatment. Seventeen rhesus monkeys were exposed to 7.0 Gy (60)Co γ-ray total body irradiation (TBI) to establish severe haemopoietic ARS model, and were randomly divided into supportive care group, rhG-CSF+rhTPO treatment group and rhG-CSF+rhTPO+rhIL-2 treatment group. Survival time, general signs such as bleeding and infections, and peripheral blood cell counts in each group were monitored. Bone marrow cells were cultivated to examine the colony formation ability. The histomorphology changes of bone marrow were observed at 45 d post irradiation. After 7.0 Gy (60)Co γ-ray TBI, monkeys of supportive care group underwent tarry stool and emesis, then died in 12~18 d. The overall survival rate in this group was 16.7%. Gastrointestinal reactions of monkeys in two combined-cytokines treatment groups were inapparent. Combined-cytokines treatment induced 100% survival. Complete blood cells declined sharply after irradiation in each group, but two combined-cytokines treatment schemes could elevate the nadir of all blood cells, shorten the duration of pancytopenia and accelerate the recovery of hemogram. Compared with rhG-CSF+ rhTPO treatment, rhG-CSF+ rhTPO+ rhIL-2 treatment could increase the counts of lymphocytes and monocytes. The colony-formation rate of haemopoietic stem/progenitor cells in bone marrow dropped markedly at 2 d after irradiation. Combined-cytokines treatment promoted the ability of colony formation on day 29. Hematopoietic cells mostly disappeared in bone marrow of animals in supportive care group, but hematopoietic functions were recovered after cytokines were administrated. rhG-CSF+ rhTPO and rhG-CSF+ rhTPO+ rhIL-2 treatment can significantly promote hematopoiesis recovery, improve the quantity of life, simplify the supportive therapy, and enhance the survival rate of rhesus monkeys with severe haemopoietic ARS induced by 7.0 Gy (60)Co γ-ray exposure. Especially the application of rhIL-2 can accelerate the recovery of lymphocytes and monocytes and restore the immunological function. Thus, combination of rhG-CSF, rhTPO and rhIL-2 on the basis of supportive care is an efficient strategy to treat severe haemopoietic ARS.