Radioprotective effects of CBLB502 on γ-radiated Rhesus monkey

Objective　A Rhesus monkey model was employed to study the radioprotective effects of a Toll-like receptor 5 agonist, CBLB502, against 7.0Gy whole-body irradiation of 60Co gamma-rays. Methods　Thirty animals were assigned to a placebo treatment group, a WR-2721 positive control group, and three CBLB502 treatment groups (n=6 animals/group). Each animal was irradiated with 7.0Gy 60Co γ and given CBLB502 at 2.5, 10 and 40μg/kg, respectively in treatment groups, or WR-2721 at 30mg/kg, or physiological saline 0.3ml/kg for the placebo treatment group. The treatment was given once by intramuscular injection 30 min before irradiation. All irradiated animals received symptomatic treatment based on same guidelines. General observation, peripheral blood tests, hemopoietic progenitor cell colony-counting, and histopathological examination were performed. Results　We found that 10 or 40μg/kg CBLB502 treatment resulted in 100% survival, while the survival rate was 33% in placebo treatment group. Hematopoietic recovery in the WR-2721 treatment group was marginally superior to the irradiation control group. Nadirs of peripheral white cell and platelet counts of animals treated with 40μg/kg of CBLB502 were significantly higher than those of the placebo treatment group (P<0.05). CBLB502 at 40μg/kg also gave a shortened duration of low platelet count, earlier recovery time, reduced the amount of blood transfusion and damage to the bone marrow and intestine. Conclusion　All Rhesus monkeys irradiated with 7.0Gy 60Co γ-rays would suffer from severe acute radiation sickness of hematopoietic system. CBLB502 at 40μg/kg is radioprotective in this model and a single intramuscular injection of CBLB502 in a dose of 40μg/kg 30min before irradiation gives better radioprotective effects than WR-2721. DOI: 10.11855/j.issn.0577-7402.2015.04.07