Stimulation of complement production in mice by N alpha-(N-acetylmuramyl-L-alanyl-D-isoglutamine)-N epsilon-stearoyl-L-lysine

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.

Influence of muramyl dipeptide on renal candidiasis in genetically distinct mice

Susceptible (DBA/2) and resistant (C57BL/6) mice were inoculated intravenously with Candida albicans to evaluate the effect of a four-day prophylaxis with muramyl dipeptide (MDP) on the renal burden of organisms during the first week after infection. In sham-treated DBA/2 mice injected with 8 x 10(4) candida cells, renal CFU (LOG10 +/- SEM) on days 1, 4 and 7 after infection were found to average 5.050 +/- 0.109, 4.882 +/- 0.133 and 5.482 +/- 0.245. In sham-treated C57BL/6 mice injected with 2 x 10(5) candida cells, renal CFU on days 1, 4 and 7 reached only 3.610 +/- 0.118, 3.404 +/- 0.107 and 4.176 +/- 0.580. MDP-treated DBA/2 mice achieved significant reduction in CFU of C. albicans on day 1 (1.3 log units) and day 4 (0.6 log unit), while MDP-treated C57BL/6 mice had significant reduction in CFU of C. albicans only on day 1 (0.6 log unit) after infection. Sham-treated mice of both strains had a 28.6 to 30% increase in kidney weights on day 4 only, a transient change not seen in MDP-treated mice. Histopathological examination on days 8, 15 and 21 after infection revealed a higher incidence of renal papillary necrosis in DBA/2 mice than C57BL/6 mice (approximately 70% vs 10%). The incidence of granulomas and of chronic interstitial inflammation was much higher in MDP-treated mice. We conclude that the genetic makeup of the host influences the potential effectiveness of MDP as a biological response modifier.

Synergistic effects of romurtide and cefmenoxime against experimental Klebsiella pneumonia in mice

We investigated the synergistic effects of romurtide (MDP-Lys [L18]) and cefmenoxime (CMX) in the treatment of experimental Klebsiella pneumonia in mice. Mice were infected with 1 x 10(4) CFU of Klebsiella pneumoniae by inhalation of aerosol bacterial suspension. About 90% of untreated animals died within a week; however, the mortality rate of animals treated with CMX alone at a dose of 40 mg/kg/day was 60% at 7 days after the infection. When one or two doses of L18 were administered before or after the infection concomitantly with CMX, a remarkable improvement in the survival rate was observed. There was no significant improvement in the survival rate of animals treated with L18 alone before or after infection. Histopathological sections of the lungs of mice treated with CMX and L18 showed slower progression of infection than those of mice treated with CMX alone. Significant differences were also found in quantitative cultures of viable bacteria in the lungs 1 to 4 days after the infection. Although viable bacterial counts in the lungs of the control and CMX-treated groups showed a rapid increase 24 to 48 h after the infection, they remained lower than the initial counts (x 10(4)) in the lungs of mice treated with combination regimens. From these results, it can be concluded that L18 is a useful biological response modifier in the treatment of acute pulmonary bacterial infections.

Synergistic induction of cytotoxicity in macrophages by murine interferon-gamma and biological response modifiers derived from microorganisms

The ability of recombinant murine interferon-gamma (rMuIFN-gamma) to activate murine macrophages with or without several biological response modifiers (BRM), including synthetic muramyl dipeptide derivatives (MDPs), was investigated. Mouse peritoneal macrophages were activated by rMuIFN-gamma alone to the cytostatic state, but not the cytolytic state. Other BRM as well as bacterial lipopolysaccharide (LPS), including a lyophilized preparation of an attenuated strain of Streptococcus hemolyticus, a cell wall skeleton of bacillus Calmette-Guerin and synthetic MDPs, were highly active in generating the synergism with rMuIFN-gamma. Macrophages were endowed with the cytolytic activities by combinations of rMuIFN-gamma and MDP-Lys(L18); the combination of 100 U/ml of rMuIFN-gamma with 10 ng/ml of MDP-Lys(L18) was sufficient to induce cytolytic activities in macrophages. The synergism was observed when the macrophages primed with rMuIFN-gamma were treated with LPS or MDP-Lys(L18), but not when the sequence of treatment was reversed. The cytotoxicity of macrophages induced by rMuIFN-gamma with MDP-Lys(L18) was suppressed by priming with MDP-Lys(L18). The suppressive effect was also observed by priming with LPS in combinations of rMUIFN-gamma and LPS. The reason for the suppression of macrophage activation by priming with LPS and MDP-Lys(L18) is at present unknown.