Augmentation of immune responses by a muramyl dipeptide analog, MDP-Lys(L18)

Induction of tumor necrosis factor-α in solid tumor region by the orally administered synthetic muramyl dipeptide analogue, romurtide

The novel applications of a muramyl dipeptide analogue, romurtide, were investigated. When mice were intravenously injected with 10-1000 micrograms/mouse of romurtide as a primer and 3 KE/mouse of OK-432 as a trigger, systemic tumor necrosis factor-alpha (TNF-alpha) activity was increased. Similar effects were also detected by oral administration of romurtide at 1000 to 10,000 micrograms/mouse. These effects reached maximum at 3 h (intravenous injection, i.v.) or 6 h (oral administration, p.o.) after administration and were sustained for 48 h. When romurtide was administered to MM46 tumor-bearing mice orally, the significant augmentation of TNF-alpha production could be detected in the solid tumor and the liver. When romurtide was intravenously injected to the tumor bearer, the TNF-alpha production was significantly augmented in the spleen. These findings suggest that romurtide can augment the host defense system by both the parenteral and oral route, and indicate the possibility of a new type of anti-tumor therapy to induce TNF-alpha in the tumor region.

Romurtide, a synthetic muramyl dipeptide derivative, promotes megakaryocytopoiesis through stimulation of cytokine production in nonhuman primates with myelosuppression

The response of megakaryocytes and cytokines to the administration of romurtide, a synthetic muramyl dipeptide derivative, was investigated in monkeys with myelosuppression by carboplatin-treatment. Romurtide increased the number of megakaryocytes and promoted the shift of megakaryocytes towards high ploidy class indicative of the promotion of the proliferation and maturation of megakaryocytes. The serum levels of interleukin-6, stem cell factor, and erythropoietin elevated significantly before the enhanced response of megakaryocytes induced by romurtide was observed. Romurtide also enhanced production of colony-stimulating factors (CSFs), such as granulocyte-CSF, macrophage-CSF, and granulocyte-macrophage CSF by monkey mononuclear cells. The stimulating effect of romurtide on the production of those cytokines and CSFs is likely to be responsible for the subsequent promotion of the proliferation and maturation of marrow megakaryocytes.

Romurtide, a synthetic muramyl dipeptide derivative, accelerates peripheral platelet recovery in nonhuman primate chemotherapy model

We investigated the therapeutic effects of romurtide, a synthetic muramyl dipeptide derivative, on experimental thrombocytopenia induced by carboplatin in cynomolgus monkeys. A prolonged thrombocytopenia due to a severe myelosuppression was induced by carboplatin. Romurtide given subcutaneously elevated significantly the peripheral platelet counts during both early initiation and later recovery phase of thrombocytopenia, thereby shortening the time required for recovery to a normal platelet level and the duration of thrombocytopenia. An oral administration of romurtide was also found to have a similar therapeutic efficacy to subcutaneous administration. These results demonstrated a possible therapeutic potential of romurtide in the management of thrombocytopenia associated with myelosuppression.

Inflammatory cytokine production induced by an analogue of muramyl dipeptide MDP-Lys(L18) in rat macrophage cultures and dog synovial fluid

To examine the involvement of cytokines in the mechanisms of N2-[(N-acetylmuramoyl)-L-alanyl-D-isoglutaminyl]-N6-stearoyl-L-lysine, MDP-Lys(L18)-induced arthritis, we analyzed interleukin-1 (IL-1), tumor necrosis factor (TNF), colony-stimulating factor (CSF), and neutrophil chemotactic factor (NCF) by bioassays in the rat macrophage-conditioned medium (Mluminal diameter-CM) stimulated by MDP-Lys(L18) in vitro and the synovial fluid from dogs treated subcutaneously with MDP-Lys(L18) for 14 days in vivo. The dog showed arthritis characterized by swelling of the knee joint, increased synovial fluid and thickened synovial membrane, and a single subcutaneous injection of MDP-Lys(L18) was previously shown to induced synovitis in rat tarsal joint. IL-1, TNF, CSF, and NCF activities in Mluminal diameter-CM were increased by MDP-Lys(L18), while only NCF activity was detected in the dog synovial fluid. Partial purification procedures revealed that NCF in Mluminal diameter-CM was not leukotriene B4 but a protein having heparin-affinity, and, in addition, immuno-reactive IL-8 was evident to be in Mluminal diameter-CM. The NCF activity in the dog synovial fluid was not inhibited by dialysis, showing that NCF is a protein substance, possibly a chemokine. These results suggest that MDP-Lys(L18) produces a chemokine, such as IL-8, which recruits neutrophils to the synovial membrane for subsequent development of synovitis in rats and dogs.

Pharmacological aspects of arthritis induced by a muramyl dipeptide analogue in rats

Fourteen consecutive daily subcutaneous injections of 4 mg/kg of the muramyl dipeptide analogue MDP-Lys(L18) into rats caused arthritis characterized by swelling of the tarsal joint, increases in lymphocytes and monocytes in the peripheral blood, and elevated serum immunoglobulin G (IgG). The present study was performed to evaluate the effects of indomethacin, phenylbutazone, dexamethasone, D-penicillamine, aurothioglucose, cyclophosphamide and cyclosporin A on this arthritis. Administration of indomethacin, phenylbutazone or dexamethasone inhibited the development of the tarsal joint swelling, suggesting that prostaglandins may be involved in the pathogenesis of the arthritis. Cyclophosphamide reduced the arthritis, together with decreases in the lymphocyte count and the serum IgG level. Cyclosporin A worsened the arthritis in a dose-dependent manner and increased the neutrophil count without raising the serum IgG level, but inhibited the induction of adjuvant arthritis in rats with Mycobacterium bacilli. MDP-Lys(L18) may therefore induce arthritis differing in mechanism from adjuvant arthritis.

Use of low toxicity adjuvants and killed virus to induce protective immunity against the Friend murine leukaemia retrovirus-induced disease

Low toxic and synthetic adjuvants were investigated in the induction of protective immunity against Friend murine retrovirus-induced erythroleukaemia by immunization with inactivated Friend murine leukaemia helper virus (F-MuLV). 6-O-(2-tetradecyl-hexadecanoyl)-N-acetylmuramyl-L-alanyl-D-isoglutamine (B30-MDP) showed a significant enhancement of the protective immunity against Friend virus-induced erythroleukaemia not only in H-2a/b mice known to make good immune responses to F-MuLV envelope, but also in H-2a/a mice which are usually unable to respond to F-MuLV envelope protein. Another analogue of N-acetylmuramyl-D-isoglutamine (MDP), N alpha-acetylmuramyl-L-alanyl-D-isoglutaminyl-N epsilon-stearoyl-L-lysine [MDP-Lys(L18)], which has been shown to enhance non-specific protective activity against bacterial and viral infections, however, showed no adjuvant activity in the present system. A combined adjuvant of the synthesized mycobacterial cord factor, trehalose dimycolate (TDM) and detoxified bacterial endotoxin, monophosphoryl lipid A from Salmonella minnesota, gave good protection which was comparable to complete Freund's adjuvant in both H-2a/b and H-2a/a mice.