New approaches for control of infections using synthetic or semi-synthetic constructs containing MDP.
Explore the source record for details and available documents.
Acetylmuramyl-Alanyl-Isoglutamine↗
Biomedical subjects
L Chedid
Publications and source records attributed to L Chedid.
Immunological castration by a totally synthetic vaccine: modification of biological properties of LH-RH after conjugation to adjuvant-active muramyl peptide.
Recently, we demonstrated that immunological castration of male mice can be obtained by immunization with Luteinizing Hormone-Releasing Hormone (LH-RH) directly coupled to NAcMur-L-Ala-D-isoGln-L-Lys (MDP-Lys) without carrier and Freund's Complete Adjuvant (FCA) but in the presence of Polyvinyl-Pyrrolidone (PVP). In the present report, we have observed that: (a) immunization by the conjugate, LH-RH-MDP-Lys, was very effective even in absence of PVP, and this conjugate was more active than other conjugates containing MDP coupled to LH-RH fragments; (b) a strong secondary response could be observed by the administration of free LH-RH suggesting that the endogenous secretion of LH-RH might elicit a boosting effect; (c) administration of MDP-Lys coupled to LH-RH decreased the pyrogenicity of the glycopeptide; (d) such a conjugation also decreased the hormonal activity of the antigen although it enhanced its immunogenicity. These results show that a conjugate (2000 dalton) of a decapeptide hormone with a synthetic adjuvant glycopeptide can induce immunological castration in mice after administration in saline. The immunopharmacological properties of the conjugate and its conditions of efficacy suggest that such an approach could find clinical application.
Acetylmuramyl-Alanyl-Isoglutamine↗
Increased synthesis of fibrinolytic inhibitor induced by muramyl dipeptide derivatives in human cultured endothelial cells.
A decreased fibrinolytic activity induced by bacterial products and some muramyl peptides has been previously demonstrated in macrophages preparations. Since vascular endothelial cells are important for the fibrinolytic balance, we have studied the effects of MDP derivatives on cultured endothelial cells. The supernatant of MDP and murabutide treated cell cultures exhibited an increased fibrinolytic inhibitory activity when tested with urokinase. The MDP(D-D)-treatment had no effect. This increased inhibitory activity was detectable in the supernatant after a 6 h treatment and was suppressed by the addition of puromycin to the cell cultures. Furthermore, the endothelial cell culture supernatant also reduced the lytic activity of the human plasma plasminogen activator induced by venostasis. This was enhanced by MDP treatment of the cultures. These in vitro results suggested that adjuvant-active muramyl peptides may regulate the fibrinolytic balance at the vessel wall level. This could be of possible significance in the transendothelial cell migration where the role of plasminogen activator(s) has been involved.
Acetylmuramyl-Alanyl-Isoglutamine↗
In vitro inhibition of murine B-cell tumor growth by MDP, MDP(D-D) and Vaccin is mediated by macrophages.
The effect of two muramyl dipeptides, N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) and N-acetylmuramyl-D-alanyl-D-isoglutamine (MDP(D-D)), on the in vitro growth of two murine ascitic plasmacytomas, MOPC 173 and TEPC 15, and on an ascitic lymphoma cell line, ABPL2, was studied. The ability of the muramyl dipeptides to inhibit tumor cell growth was compared with a sonicated antigenic preparation of Mycobacterium vaccae (Vaccin), known to have macrophage stimulation activity. The growth of all three ascitic cell lines was inhibited by both muramyl dipeptides and Vaccin. Macrophage-depletion of the ascitic cell populations led to an increase in cell growth of TEPC 15 and MOPC 173, and a decrease in ABPL2. A reduction or loss of the inhibitory activity of the muramyl dipeptides or Vaccin was also observed, and no inhibitory activity was found when the tumor cell lines were cultured in vitro to render them macrophage-free. The inhibitory activity of MDP or MDP(D-D) was restored when purified ascitic macrophages were added to the in vitro cultured cell lines. It was demonstrated that a minimum number of macrophages were necessary for the expression of inhibitory activity. Indomethacin, a PG-synthetase inhibitor, was found to act in a synergistic manner with MDP and MDP(D-D) in inhibiting TEPC 15, but antagonized the effect of these two agents on ABPL2. The lymphoma cell line ABPL2 appeared to be the most sensitive to inhibition by MDP(D-D), a nonpyrogenic, adjuvant-inactive stereoisomer of MDP.
Acetylmuramyl-Alanyl-Isoglutamine↗
Attempts to induce resistance to Schistosoma mansoni and S. haematobium in Kenyan baboons (Papio anubis) using non-specific immunostimulants.
Non-specific immunostimulants were used in an attempt to protect baboons from infection by schistosomes. Subcutaneous vaccination with cord factor (4.50 mg) and muramyl dipeptide (4.56 mg) 6 days before percutaneous exposure to 3000 Schistosoma haematobium cercariae/baboon (c.p.b.) failed to protect naive baboons: baboons with a 7-month-old, 5000 c.p.b. S. haematobium primary infection had developed too strong a natural immunity to detect any protection attributable to vaccination. Subcutaneous vaccination with 0.4 ml of Bacillus Calmette-Guerin (BCG, 1-8 X 10(8) colony forming units/ml) 4 days before exposure to 1000 c.p.b. S. mansoni gave a significant (38%) reduction in worm load compared with controls. However, vaccination with 0.8 (intramuscular) and 0.2 (intradermal) ml of BCG 11 days before exposure to S. mansoni 800 c.p.b. did not protect naive baboons, nor did it significantly reduce challenge worm recovery from baboons with a 13-week-old, 500 c.p.b. S. mansoni primary infection. Obvious pathology was seen at the site of vaccination in the first but not the second BCG experiment. These results partly support the findings in mice that non-specific macrophage and monocyte activators give partial protection against schistosome infections but they also illustrate that rodents and primates do not necessarily react identically. Hence, findings from rodent models should be extrapolated to man with some caution.
Acetylmuramyl-Alanyl-Isoglutamine↗
Effects of natural or synthetic microbial adjuvants on induction of autoimmune thyroiditis.
Natural and synthetic adjuvants of microbial origin were compared for their capacity to potentiate the induction of experimental autoimmune thyroiditis (EAT) with the autoantigen mouse thyroglobulin (MTg). Regardless of the immunomodulator used, severe thyroiditis was observed only in EAT-susceptible strains of the k haplotype and not in EAT-resistant strains of the d haplotype. Compared to phenol-extracted lipopolysaccharide, a potent adjuvant for enhancing EAT induction, phthalyl-substituted, detoxified lipopolysaccharide, even at doses 15- to 50-fold greater, led to only low anti-mouse thyroglobulin titers and mild thyroid infiltration. The synthetic adjuvant N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) and three of its analogs, N-acetylmuramyl-L-alanyl-D-isoglutamine-L-alanyl-D-glycerol mycolate (MDP-L-Ala-Glyc-Myc), N-acetylmuramyl-L-alanyl-D-glutamyl-(decyl)methyl ester [MDP(decyl)methyl], and N-acetylmuramyl-L-alanyl-D-glutamine-alpha n-butyl ester [MDP-(Gln)-OnBu], designated murabutide, were tested in incomplete Freund adjuvant or in saline. In incomplete Freund adjuvant, MDP-L-Ala-Glyc-Myc was inefficient in inducing EAT, murabutide induced very mild involvement, and MDP and, more so, MDP(decyl)methyl were active but to a lesser degree than CFA. When saline was used, low levels of thyroid infiltration were observed in a few of the MDP-treated animals in only one experiment, whereas no lesions were observed when murabutide was used.
Acetylmuramyl-Alanyl-Isoglutamine↗
Depressed chemiluminescence response by influenza virus is enhanced after conjugation of viral subunits to muramyl dipeptide.
The effect on respiratory burst of murine spleen cells after in vitro exposure to influenza virus, subunits, or subunits conjugated to muramyl dipeptide (MDP) was studied by luminol-dependent chemiluminescence (CL) in response to stimulation by zymosan. CL induced by infectious influenza A virus was depressed but could be elevated to normal levels when MDP was added together with a low, but not with a high, dose of the virus. Profound depression of CL was induced by high doses of influenza A/Brazil, A/Bangkok, and B/Singapore subunits. The same amounts of viral subunits conjugated to MDP restored or even enhanced the CL responses of spleen cells from BALB/c and C57BL/6 mice. Splenic cells from BALB/c mice generated higher levels of CL than did cells from C57BL/6 mice.
Acetylmuramyl-Alanyl-Isoglutamine↗
Carrier-induced epitopic suppression, a major issue for future synthetic vaccines.
Synthetic antigens have been shown, in experimental models, to induce protective immunity against a variety of pathogens. These studies have demonstrated that, due to their low immunogenicity, these synthetic antigens required conjugation to carrier molecules. Therefore, the choice of appropriate carriers for human immunization by future synthetic vaccines is a major issue. Tetanus toxoid is generally considered to be an effective potential carrier devoid of side-effects. However, the present study performed in mice with two synthetic vaccine models demonstrates that the immune response against the synthetic epitopes conjugated to tetanus toxoid can be suppressed by pre-existing immunity against this same carrier. Because most humans have been exposed to this antigen, this effect may have important implications for the development of synthetic vaccines.
Animals↗
Activation of alveolar macrophage tumoricidal activity and eradication of experimental metastases by freeze-dried liposomes containing a new lipophilic muramyl dipeptide derivative.
The ability of a member of a new class of lipophilic muramyl dipeptide (MDP) derivative, muramyl dipeptide-glyceryldipalmitate (MDP-GDP), to induce alveolar macrophage cytotoxic activity in vitro towards B16 melanoma cells when incorporated into two types of liposome was studied. MDP-GDP incorporated into conventionally prepared liposomes formulated from distearoylphosphatidylcholine and phosphatidylserine (7:3 molar ratio) was 10-fold more effective than liposomes containing MDP, and 7000-fold more effective than free MDP in inducing macrophage cytotoxic activity. MDP-GDP incorporated into freeze-dried liposomes was 50,000- to 100,000-fold more effective than free MDP in inducing such activity. Freeze-dried liposomes containing MDP-GDP were efficiently localized in the lungs of normal mice, and induced cytotoxic activity in the alveolar macrophages. Such liposomes were able to significantly reduce the pulmonary metastatic burden of mice carrying the B16 melanoma. These data provide evidence that this class of lipophilic MDP derivative, when incorporated into freeze-dried liposomes, is a potent inducer of macrophage cytotoxic activity in vitro and in situ, and has antitumor activity in vivo. In addition, the use of a freeze-drying procedure allows the preparation and long-term storage of reproducible liposome formulations.
Acetylmuramyl-Alanyl-Isoglutamine↗
Strain dependence of muramyl dipeptide-induced LAF(IL 1) release by murine-adherent peritoneal cells.
The capacity of MDP to stimulate LAF(IL 1) production by adherent peritoneal cells (APC) from different strains of mice was examined. It was observed that MDP could stimulate thioglycollate-induced APC from DBA/2, C57B1/6, and CBA/CA mice, but not from C3H mice. Resident APC from DBA/2 or C3H/HeJ mice were also responders and nonresponders, respectively, to MDP for LAF(IL 1) production, the positive effect of MDP being more marked on DBA/2 cells in the presence of indomethacin. Because a LPS high-responder C3H substrain (C3HeB/Fe) did not respond to MDP, it was concluded that the strain dependence with respect to the induction of LAF(IL 1) seen with both MDP and LPS was not linked. Moreover, the unresponsiveness of C3H mice to MDP was not linked to their MHC haplotype, because a second H-2k strain (CBA/CA) was a good responder to MDP stimulation.
Acetylmuramyl-Alanyl-Isoglutamine↗
Production of differentiation-stimulating factor for murine leukemic myeloblast line by monocytic cells stimulated by a nonpyrogenic muramyl dipeptide derivative.
Muramyl dipeptide (MDP) and adjuvant-active derivatives were confirmed as unable directly to induce differentiation of mouse myeloid leukemia M1 cells. They were, however, found effective in stimulating either rabbit macrophages or human blood monocytes to produce differentiation-stimulating activity (D factor). The various conditioned media (CM) thus obtained were able to induce differentiation of the myeloblastic M1 cell line as indicated by the appearance of Fc receptors and inhibition of cell proliferation. Among the synthetic glycopeptides inducing the production of D factor, murabutide (MDP[Gln]-OnBu) was as effective as MDP, although it did not stimulate monocytes to simultaneously release endogenous pyrogen. The absence of pyrogenicity in murabutide CM was attested by IV or intracerebroventricular administration to rabbits. However, in the same CM, LAF(IL1) activity estimated by potentiation of the in vitro proliferative response to phytohemagglutinin of mouse thymocytes was usually higher than that induced by MDP.
Acetylmuramyl-Alanyl-Isoglutamine↗
Stimulation of human endothelial cells by synthetic muramyl peptides: production of colony-stimulating activity (CSA).
The in vivo induction of colony-stimulating activity (CSA) by well-defined immunomodulatory synthetic muramyl peptides has been demonstrated recently in mice. In the present study, we tested the capacities of three muramyl peptides to induce CSA production in human endothelial cell (HEC) cultures. Two adjuvant-active peptides (MDP and Murabutide) induced CSA in the supernatant of cultured endothelial cells, whereas an adjuvant-inactive compound had no effect. This effect of MDP and Murabutide appeared to be time and concentration dependent and was not secondary to decreased production of inhibitors of colony formation. CSA secretion by stimulated HEC required de novo protein synthesis and did not result from the release of preformed active CSA. Maximal concentration appeared in the supernatant media within the first 24 h after addition of muramyl peptides, and a substantial second CSA secretion could be observed after a subsequent 24 h reexposure. This CAS was not dialyzable and promoted granulocyte-macrophage formation of nonadherent human marrow and unfractionated murine marrow. Our data demonstrate that the human endothelial cell is a target cell for MDP and Murabutide and suggest that in vivo endothelium might play an active role in muramyl peptide-induced modulation of hematopoiesis.
Acetylmuramyl-Alanyl-Isoglutamine↗
Activation of macrophage cytostatic and cytotoxic activity in vitro by liposomes containing a new lipophilic muramyl peptide derivative, MDP-L-alanyl-cholesterol (MTP-CHOL).
The ability of liposomes containing a new lipophilic muramyl peptide derivative, MDP-L-alanyl-cholesterol (MTP-CHOL), to induce peritoneal macrophage cytostatic activity and alveolar macrophage cytotoxic activity toward tumor cell targets in vitro was determined. MTP-CHOL was shown to be efficiently incorporated and subsequently retained in distearoylphosphatidylcholine/phosphatidylserine liposomes (DSPC/PS; 7:3 molar ratio), whereas hydrosoluble muramyl dipeptide (MDP) was rapidly lost due to leakage. Liposomes containing MTP-CHOL were able to stimulate mouse peritoneal macrophage cytostatic activity under conditions where free MDP was without effect. MTP-CHOL incorporated into liposomes was approximately eightfold more effective than liposomes containing entrapped MDP and 7,400-fold more effective than free MDP in inducing rat alveolar macrophage cytotoxic activity. These results provide evidence that the coupling of MDP to a lipophilic molecule, cholesterol, results in the formation of a viable liposome formulation that is a potent inducer of macrophage-mediated antitumor activity.
Acetylmuramyl-Alanyl-Isoglutamine↗
Muramyl peptides. Variation of somnogenic activity with structure.
Sleep-promoting activities of muramyl dipeptide (MDP) (NAc-Mur-L-ala-D-isogln) and the naturally occurring muramyl peptide(s), factor S, have recently been demonstrated. We now have amplified our understanding of structural requirements for somnogenic activity. The effects of several analogs of MDP on rabbit slow-wave sleep are presented and these results are compared to the dose-response relationship for MDP. Some tentative conclusions as to structural requirements for somnogenic activity are presented; most notably, amidation of the free gamma-carboxyl of MDP and several of its analogs resulted in the loss of somnogenic activity. MDP also can induce febrile and immunostimulatory responses. In the present paper, we show that some analogs possess immunostimulatory and pyrogenic activity but not somnogenic activity, thus suggesting that these biological activities of muramyl peptides may, in part, be mediated by separate mechanisms.
Acetylmuramyl-Alanyl-Isoglutamine↗
Changes in rabbit febrile responses to muramyl dipeptide (MDP) after coupling to a synthetic carrier.
Muramyl dipeptide (MDP) is a small molecular weight synthetic glycopeptide (less than 500), which has been shown to be an immunoadjuvant, and to induce a biphasic febrile response in the rabbit--probably via the release of endogenous pyrogen--accompanied by a marked leukopenia. Macromolecularization by coupling to a synthetic carrier (MW approximately or equal to 60,000) potentiates the immunostimulant properties of MDP but also its pyrogenicity. The present study demonstrates that such a conjugate induced the release of endogenous pyrogen in vivo and in vitro at lower dosage levels than free MDP. Further experiments showed that there existed several differences between free and conjugated MDP. Thus, after intravenous administration of the conjugate, the fever pattern was monophasic with a prompt defervescence and not accompanied by leukopenia at dosage levels inducing similar increase in body temperature. In addition, when fever was recorded after intracerebroventricular administration, the increase in sensitivity was much greater in the case of free MDP than of MDP-A--L.
Acetylmuramyl-Alanyl-Isoglutamine↗
Marked enhancement of macrophage activation induced by synthetic muramyl dipeptide (MDP) conjugate using monoclonal anti-MDP antibodies.
Activation of peritoneal exudate macrophages of mice to inhibit the in vitro proliferation of tumor target cells was achieved with low concentrations of N-acetyl-L-alanyl-D-isoglutamine (MDP for muramyl dipeptide) conjugated to a synthetic carrier. Addition to the cultures of monoclonal anti-MDP or anti-carrier antibodies renders a thousandfold-smaller concentration of the conjugate highly effective in activating macrophages. This synergistic effect was observed neither with a control monoclonal antibody of different specificity nor with an F(ab)2 fragment of the monoclonal anti-MDP antibody. Other controls, such as addition to the cultures of the carrier alone with its specific monoclonal antibodies, also demonstrated that there exists a requirement for the presence of MDP in the conjugate. The possible uses of such a system as well as the underlying mechanisms are discussed.
Acetylmuramyl-Alanyl-Isoglutamine↗
Modulation of the growth of murine thymoma cell lines having different Lyt-phenotypes by MDP and MDP(D-D): macrophage-mediated inhibition of in vitro cell growth.
The ability of N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) and its adjuvant-inactive stereoisomer, N-acetylmuramyl-D-alanyl-D-isoglutamine, (MDP(D-D] to inhibit the in vitro growth of 3 murine ascitic thymoma lines, expressing different Lyt-phenotypes, was studied. MDP inhibited the growth of all 3 cell lines. MDP(D-D) inhibited the 2 cell lines expressing Lyt-1+2- or Lyt-1+2+ phenotypes, but not the third cell line which expressed the Lyt-1-2+ phenotype. The ability of MDP or MDP(D-D) to inhibit thymoma growth was lost when the ascitic cell populations were depleted of macrophages. MDP could be replaced by a supernatant derived from an ascitic Lyt-1+2- cell population exposed to MDP. The supernatant required the presence of macrophages for activity. The inhibition by MDP of the growth of the Lyt-1-2+ cell line was prostaglandin synthetase dependent: indomethacin antagonized the inhibitory activity of MDP. The inhibition by MDP of the Lyt-1+2- cell line was partially antagonized by indomethacin, and no antagonism was observed with the Lyt-1+2+ cell line.
Acetylmuramyl-Alanyl-Isoglutamine↗
In vivo effects of ovalbumin-conjugated muramyl peptides on the anti-ovalbumin IgE and IgG responses in mice.
The effects of pretreatments of BALB/c mice with several conjugates of MDP and MDP-Lys to ovalbumin before immunization with ovalbumin (OA) were tested on the anti-OA IgE responses. Pretreatment with MDP-Lys-OA, but not with MDP-OA, induced an inhibition of the anti-OA primary and secondary responses, as measured by passive cutaneous anaphylaxis (PCA) and also by mast cell degranulation. The inhibition by pretreatment with MDP-Lys-OA was obtained whether it was administered in Freund's incomplete adjuvant (FIA) or in saline. This IgE suppression was accompanied by an enhancement of IgG2a and IgG2b anti-OA antibodies, with no change in the specific IgG1 levels. Loss of antigenicity of OA, detected by the lack of degranulation of peritoneal mast cells sensitized by IgE anti-OA, was observed in the MDP-Lys-OA but not in the MDP-OA conjugates. This loss of antigenicity appears to correlate with the ability of the conjugate to induce suppression of the specific IgE response.
Acetylmuramyl-Alanyl-Isoglutamine↗