Development of Shortened Recombinant Flagellin and Study of Its Radioprotective Efficacy in Mice with Acute Radiation Injury

The aim of this work is an experimental study of the radioprotective effect of shortened recombinant flagellin under conditions of total body irradiation of mice by survival rates and the effect on hemo- and immunopoiesis. A new recombinant shortened derivative of Salmonella enterica, the dFliC protein obtained by structure-oriented reengineering of a previously developed molecule, was used. The radioprotective effect of dFliC was studied in the mouse model of hematopoietic acute radiation syndrome. The 30-day survival of irradiated mice was analyzed using the Kaplan–Meier method. The effect of the dFliC protein on the number of splenic colony-forming units (CFUs) and myelokaryocytes in the bone marrow, peripheral blood parameters, and the cytokine profile in the blood serum of mice was assessed. Statistica 8.0 software was used for statistical processing of the results. A purification test record for the recombinant flagellin dFliC was developed, and protein samples with a purity of 92.79% according to HPLC were obtained. Administration of dFliC at a dose of 1 mg/kg 15–30 min prior to 7.8 Gy X-rays increased 30-day survival of mice by 38% (p < 0.05 compared to the vehicle control). On day 9 after X-ray irradiation at a dose of 7 Gy, the number of colonies increased 2.8 times in dFliC-treated mice (p < 0.05), the viability of hematopoietic progenitor cells increased and the severity of thrombocytopenia decreased. An increase in the production of IL-3 and GM-CSF involved in the regulation of the early stages of hematopoietic cell development and the macrophage chemoattractant IL-12p40 was recorded; the content of proinflammatory cytokines IL-1β and IL-33 was maintained at a lower level than during irradiation without the use of dFliC. Deimmunization and structural rearrangement of the flagellin molecule did not lead to a decrease in the radioprotective effect of the recombinant protein. The radioprotective efficacy of dFliC is provided by a protective effect on bone marrow hematopoietic cells and stimulation of postradiation restoration of hemo- and immunopoiesis by regulating the expression of cytokines with a wide range of biological activity.