Stimulation of nonspecific immunity, haemopoiesis and protection of mice against radiation injury by 1-adamantylamide-L-alanyl-D-isoglutamine incorporated in liposomes.

1-Adamantylamide-L-alanyl-D-isoglutamine (adamantylamide dipeptide (AdDP)) belongs to a group of desmuramyl muramyl peptide derivatives which are able to protect an organism from some viral infections. Encapsulation of AdDP to egg phosphatidyl choline liposomes and the targeting of this drug to lymphatic node macrophages via subcutaneous (s.c.) administration proved to be the efficient way to protect mice against irradiation when administered s.c., 24 h prior to lethal gamma-irradiation (long-term survival rate in the range of 40% compared with 0% in saline or free drug control). Parameters characteristic for the recovery of haemopoiesis in the bone marrow (number of granulocyte-macrophage haemopoietic progenitor cells, granulocyte-macrophage colony forming cells (GM-CFC)) were significantly improved in comparison with the controls and free drug on day 10 after 6.5 Gy irradiation. The haemopoietic effect was observed in the broad application time window (72 h before and 48 h after irradiation). Very high radioprotective effect of s.c. administered liposomal AdDP (L-AdDP) can be explained (together with induction of haemopoiesis) by the effective and long-lasting activation of nonspecific immunity, which withholds the onset of septicemia in early days after irradiation. Induction of nonspecific immunity was proven in Candida albicans infectious model. L-AdDP significantly increased both the survival time and score (about 40% survival compared with 0% in controls and free drug). In conclusion, L-AdDP could be therapeutically beneficial to moderate the haemopoietic damage (undesirable effect of radiotherapy or chemotherapy) and induce the non-specific immunity to support the antimicrobial treatment of immunocompromised patients.