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This work investigated the possible use of AdDP as adjuvant therapy to praziquantel (PZQ) in mice infected with PZQ-insusceptible Schistosoma mansoni isolate in a trial to increase the susceptibility of this isolate to the drug. Two batches of C57 BL/6 mice were infected with PZQ-susceptible and -insusceptible S. mansoni isolates, and each batch was divided into five groups. Seven weeks postinfection, the experimental group received AdDP (5 mg/kg) in addition to PZQ in reduced dose (3x100 mg/kg). Three of the remaining four groups were treated controls; they received AdDP, PZQ in reduced dose and in full dose (2x500 mg/kg), and the fourth group was infected untreated. In mice infected with PZQ-susceptible or -insusceptible S. mansoni isolate, praziquantel alone, and in addition to AdDP, reduced worm and egg loads and increased percentage dead eggs. Also, they improved the histopathological changes (reduction in granuloma diameter, percentage fibrotic area with increased percentage degenerated eggs). Inducible nitric oxide synthase (iNOS), nitric oxide (NO) in culture of peritoneal macrophages, and number of CD68-positive cells were decreased with improved alanine amino transaminase. In mice receiving combined therapy AdDP+PZQ, the antischistosomal efficacy and the reductions in the inflammatory granulomatous reactions, NO in cultured peritoneal macrophages, percentage fibrotic areas recorded, were comparable to that in mice receiving full dose of PZQ, with significantly higher reduction in CD68 cells denoting enhanced antischistosomal efficacy and healing of the inflammatory reactions in the liver.

In this study we tested the stimulatory effect of adamantylamide-l-alanyl-d-isoglutamine (AdDP) or its liposomal formulation (L-AdDP) on recovery of the granulocyte-macrophage hemopoietic progenitor cells in the bone marrow of sublethally irradiated mice of various ages. Number of GM-CFC progenitors in femur on day 10 was used as a parameter reflecting the stimulatory activity. Mice (aged 3-5 month) pre-treated with AdDP or L-AdDP via s.c. route displayed enhanced recovery of the granulocyte-macrophage hemopoietic progenitor cells at the dose of 5.5 Gy. Overaged mice (2 years) responded to the treatment when the dose was increased to 6.5 Gy, while radiation doses below 5.5 Gy should be used to see the stimulation effect in young mice (6 weeks). Entrapment of AdDP into liposomes enhanced costimulatory activity of sera of treated mice and prolongated this activity at least for 30 h after stimulation, in comparison to the mice treated with free AdDP where the costimulatory activity was spanned only up to 12 h. In conclusion, L-AdDP represents a suitable formulation of AdDP that induced recovery of GM-CFC progenitors in the femur of irradiated mice of various ages. The stimulatory effect depends on the extent of injury to bone marrow hemopoietic microenvironments caused by various doses of gamma-irradiation.

Chief part of hemopoietic stromal cells in mediating hemopoiesis-stimulating effects of adamantylamide dipeptide (AdDP), a synthetic immunomodulatory compound, has been determined in a series of combined in vivo/in vitro studies. Indirect stimulatory effect of AdDP on proliferation of hemopoietic progenitor cells for granulocytes and macrophages (GM-CFC) was proved to be mediated by the cells of hemopoietic microenvironment growing as adherent stromal cell populations in vitro. These results supplement previously reported findings of a positive role which is played by AdDP at modulating the interplay among stimulatory cytokines and their cellular sources, and are in consent with the idea to introduce AdDP as a constituent of the hemopoiesis- and immunity-stimulating supportive medical care.

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.

It has been demonstrated that the synthetic immunostimulatory compound, adamantylamide dipeptide (AdDP) produces hematopoiesis-stimulating effects in mice exposed to sublethal doses of ionizing radiation and increases survival in experimental animals irradiated with a lethal dose. These findings might suggest contingent extension of clinical indications for the administration of AdDP for the conditions of hematopoietic suppression, especially in oncology.

Adamantylamide dipeptide (AdDP), muramyl dipeptide (MDP), and glucan were shown to increase significantly the numbers of granulocyte-macrophage hemopoietic progenitor cells (GM-CFC) in the bone marrow of mice. However, whereas the sera of mice given MDP or glucan were found to stimulate the growth of colonies from GM-CFC in vitro, i.e. to produce a colony-stimulating activity (CSA), administration of AdDP did not lead to this effect. Nevertheless, when serum of mice given AdDP was added to the cultures concomitantly with a suboptimal concentration of mouse interleukin-3 (mIL-3), a broad spectrum hemopoietic stimulator, counts of colonies from GM-CFC were significantly increased, and accelerated growth of the colonies was found as well. This property of AdDP, i.e. its ability to exhibit co-stimulating activity (CoSA) without being able to exhibit CSA, suggests that AdDP acts in hemopoietic tissues differently as compared with the two other immunomodulators studied. It can be hypothesized that the action of AdDP is more specific when compared with its natural related compound, MDP, as well as with glucan. Our findings prove the possibility to stimulate by AdDP the granulopoietic compartment of hemopoiesis and are in agreement with previous observations concerning the absence of systemic side effects of AdDP. Both these qualities of AdDP may be advantageous when pondering over contingent clinical utilization of AdDP as hemopoietic stimulator.

The immunomodulatory effect of adamantylamide dipeptide (AdDP) was tested in Schistosoma mansoni-infected challenged mice and infected praziquantel-treated (2 x 500 mg/kg) challenged animals. In AdDP-treated mice, the drug was given 58 days post infection of mice with 120 S. mansoni cercariae, challenged with 240 cercariae one day after treatment, while in praziquantel-treated mice, the drug was given 44 days post infection, two weeks post treatment (58 days post infection) they were given AdDP in the same dose and one day later challenged with the same cercarial load. AdDP increased the resistance against reinfection (90.3% vs. 83.5% in infected challenged control). The significant increase in resistance against reinfection was accompanied by significant increase in the percentage of lymphocytes forming EAC rosettes. Mice cured of their primary infection by praziquantel showed a significant reduction in percent resistance, hepatic granuloma size and intragranulomal Thy+ 1,2 and Lyt+ 1 T cells. In mice treated with both praziquantel and AdDP, resistance to reinfection was significantly higher than in mice treated with praziquantel only (89.29% vs. 62.13%) reaching a level comparable to that recorded in infected-challenged controls. Meanwhile granuloma size was not significantly different from that in the infected-challenged controls with a significant rise in Lyt+ 1 T cells. Data may suggest a role for granuloma as a mechanical obstacle and/or as a T cell-mediated reaction in maintenance of resistance to reinfection. A role for B lymphocytes should be considered as the rise of percent resistance to reinfection in mice treated with AdDP alone was accompanied by a significant increase in the percentage of B lymphocytes forming EAC rosettes. Moreover, findings may suggest the use of AdDP together with specific chemotherapy in endemic areas where reinfection and repeated treatment with its consequences are of common occurrence.

The present experiments demonstrate that, similar to immunomodulatory muramyl dipeptide, its desmuramyl analog adamantylamide dipeptide is able to induce mild and fully reversible paw edema in mice. This effect is an immune-related phenomenon depending on the activation of T-cell/macrophage interactions and on production of prostaglandins. Possible involvement of certain immunoregulatory/inflammatory cytokines (e.g. IL-1, IL-2) has been suggested. The most probable intrinsic moiety of the adamantylamide dipeptide molecule responsible for triggering the edema formation is obviously D-isoglutamine.

The incorporation of equimolar doses of [14C]-palmitic and [3H]-oleic acids into the lipid moiety of hepatocytes after muramyl dipeptide (MDP), adamantylamide dipeptide (AdDP) and levamisole (LM) administration were investigated. The utilization of [14C]-palmitic acid for the synthesis of neutral lipids and phospholipids of crude nuclear fraction increased significantly after MDP and AdDP administration and to a lesser extent after LM. While the incorporation of [3H]-oleic acid did not change significantly after MDP and AdDP, LM significantly increased the incorporation of this acid into the phospholipids of nuclear and microsomal fractions. The changes in the incorporation of saturated palmitic and unsaturated oleic acids suggest a possible influence on deacylation-reacylation mechanisms. These changes could alter the physical properties of membrane and affect certain membrane functions, including the activity of membrane bound enzymes and transport mechanisms.

A pharmacokinetic profile of 14C-AdDP with uniformly labelled alanine was investigated. It was shown that the distribution phase after an i.v. administration is very short with a half-life of 2.1 min. The half-life of elimination phase after the i.v. administration is about 2.85 hours, that is longer than those of MDP and its derivatives. The total body clearance (30 ml/min/kg) is caused predominantly by metabolism of the compound. All the radioactivity found in urine in a 48 hours interval after a s.c. administration represents only 3.1% of the administered dose. Only a smaller part of the excreted radioactivity is formed by unmetabolised AdDP. The concentration curve after a s.c. administration is characterized by a very fast absorption with a half-life shorter than 1 minute. The distribution and elimination phases are prolonged (20 min, 11 hours respectively) in comparison with an i.v. injection. The decreased absolute bioavailability after a s.c. administration (65%) is probably not biologically significant because of a slower release of the compound from the site of the s.c. administration. A relatively very high radioactivity was found in liver, kidney, thymus, spleen and brain very soon which suggest a very good penetration into tissues. It is an agreement with the high apparent distribution volume of peripheral compartment and higher lipophilicity of AdDP as compared to MDP.

Adamantylamide dipeptide (AdDP) is a novel synthetic compound combining the antiviral properties of amantadine and the essential adjuvant activity of immunomodulator muramyl dipeptide. Mice were immunized with influenza A/Taiwan/1/86 (H1N1), A/Sichuan/2/87 (H3N2) and influenza B/Beijing/1/87 subunit vaccines containing AdDP or aluminium hydroxide (Al(OH)3). Induction of homologous haemagglutination-inhibition (HI) antibodies and correlation to protection against lethal aerosol influenza A/PR/8/34 (H1N1) infection were investigated. Subunit vaccine containing A/Sichuan (H3N2) and Al(OH)3 stimulated high HI antibody titres but failed to provide protection against heterologous influenza A (H1N1) challenge infection following either the primary or the secondary immunizations. In contrast, similar treatment with A/Sichuan subunit vaccine containing AdDP conferred significant protection against heterologous challenge despite low levels of circulating antibody. Primary immunization with even influenza B/Beijing subunit vaccine containing AdDP, but not Al(OH)3, provided partial protection against influenza A challenge. These results suggest that appropriate immunomodulators like AdDP can convert restricted homotypic immunity induced by inactivated influenza subunit vaccines to advantageous cross-reacting type of heterologous response.

The adjuvant effect of a novel synthetic compound adamantylamide dipeptide (AdDP) was tested in a model of delayed hypersensitivity to ovalbumin in guinea pigs, and of immunostimulatory activity in the experiments with 3H thymidine where DNA biosynthesis was measured in several immunocompetent organs after administration of adamantylamide dipeptide. In both tests, the compound proved to be active since delayed hypersensitivity was potentiated and a marked increase in the utilization of 3H thymidine in liver, thymus and spleen has been observed. The novel compound appeared to be devoid of other effects of MDP such as pyrogenicity and arthritogenicity.

The potency of two synthetic immunomodulators, muramyl dipeptide and adamantylamide dipeptide, which have the immunoadjuvant and immunomodulatory activity on pain threshold was studied. Two different analgesiometric procedures were employed: hot plate test and acetic acid writhing test in mice and rats. Both compounds were injected intravenously (1-4 mg/kg), intraperitoneally (5-50 mg/kg) and intracerebroventricularly (0.5-4 mg/kg) and were able to produce mild transient analgesia in both species. Writhing response was more influenced after systemic administration of drugs while hot plate latencies was not. On the contrary, latencies in hot plate test were more affected than the writhing response after intracerebroventricular administration. Dose response curve showed a bell shaped feature typical for peptides. Pretreatment with naltrexone, an opiate antagonist, did not prevent the analgesic action of tested compounds. The hyperalgesia induced by administration of parachlorophenylalanine, a serotonin depletor, could be prevented by administration of a nonanalgesic dose of MDP (0.025 mg/kg). At higher dosages (1 mg/kg) MDP was able to antagonize also general toxic effects of pCPA. These results support the possibility of participation of central serotonergic structures in MDP and AdDP induced analgesia. The peripheral mechanism of action, however, can not be completely ruled out.