Effect of muramyl dipeptide analog on Salmonella enteritidis infection in beige mice with Chediak-Higashi syndrome

Analysis of atherosclerosis susceptibility in mice with genetic defects in platelet function

To determine whether platelets contribute to the development of atherosclerosis, we compared the severity of atherosclerosis in susceptible C57BL/6 mice carrying either a normal or a variant phenotype for platelet function. Five genetically distinct mutants with increased bleeding times and abnormal dense granules were used: maroon (ru-2mr), light ear (le), ruby eye (ru), beige (bg1), and pale ear (ep). After a 14-week consumption of an atherogenic diet, three mutants had significantly less disease involvement than the control: light ear, maroon, and ruby eye. In contrast, pale ear ahd lesions similar to control animals. After 48 weeks, the two mutants with the least degree of atherosclerosis at 14 weeks, light ear and ruby eye, showed greater than 50% survival. In contrast, no animals from the beige, pale ear, or the normal C57BL/6 strains survived. To determine whether a specific biochemical component of platelet function is related to atherosclerosis, we measured serotonin found in dense granules. Serotonin showed no correlation with each mutant's atherosclerosis susceptibility. These results indicate that some particular component of platelet function affects atherosclerosis. That component is intact in pale ear, moderately affected in beige and maroon, and severely affected in light ear and ruby eye. The identity of that component remains an interesting question whose answer may provide further insight into the atherosclerotic disease process.

The adjuvant effect of a muramyl dipeptide (MDP) analog on temperature-sensitive Salmonella mutant vaccine

Adjuvant effect of a synthetic muramyl dipeptide analog, MDP-Lys (L18), MurNAc-L-Ala-D-glu[Lys(CO-(CH2)16-CH3)-OH]NH2 on a live Salmonella enteritidis vaccine, a temperature-sensitive mutant Ts-O strain that was obtained from the virulent S. enteritidis No.11 strain and could not grow at 37 degrees C, but could multiply at 25 degrees C as fast as the parent strain, was examined. Although the Ts-O organisms were avirulent and could hardly multiply in vivo when the organisms were injected into C57BL/6 mice and its mutant beige strain, which has a malfunction of phagocytic cells, injection of these mice with Ts-O endowed them with some protective immunity against infection by the virulent No.11 strain. When MDP-Lys(L18) was injected with Ts-O vaccine, the protection and the bactericidal capacity in the peritoneal cavities and spleens of these mice were augmented. MDP-Lys(L18) was still effective when it was injected at 48 h before or after the inoculation of Ts-O vaccine. Its effect was also observed against infection by the virulent S. cholerae-suis Hokkaido strain, a strain that does not share common O-antigenic determinants with the S. enteritidis No.11 or Ts-O strain. In addition, the mice that were inoculated simultaneously with Ts-O organisms and MDP-Lys(L18) were examined 10 days later for their footpad delayed type hypersensitivity reactions against Ts-O antigen. Mice inoculated with MDP-Lys(L18) and Ts-O showed augmented footpad swelling in comparison with the controls. These findings indicate that MDP-Lys(L18) is capable of augmenting the cellular immunity by live vaccine.

Drug delivery to macrophages for the therapy of cancer and infectious diseases

The mechanisms by which mononuclear phagocytes discriminate between self and nonself, recognize foreign materials, senescent, damaged, old, or effete cells, and tumor cells are unknown. However, regardless of the mechanism(s) involved, once activated by the appropriate signal(s), macrophages are able to selectively recognize and destroy neoplastic cells in vitro and in vivo. Liposomes injected intravenously, in common with other particulate or polymeric matrices, localize preferentially in organs with high mononuclear phagocyte activity and in circulating blood monocytes. This behavior allows microparticulates to serve as a convenient system for the selective delivery of encapsulated drugs to cells of the mononuclear phagocyte series in vivo. Liposomes are a particularly attractive experimental system because of their capacity to incorporate a wide variety of water-soluble and lipid-soluble drugs. At this time, however, there is no reason to assume that a liposome-based drug delivery system will offer any significant therapeutic advantage compared to other microparticulate drug delivery systems. As in commercial development of any pharmaceutical preparation, considerations of cost-of-goods, shelf life, and acceptance of the formulation and dosing regimen by both physicians and patients will be of major importance in determining success and widespread clinical use. Liposomes containing macrophage-activating agents are highly effective at augmenting macrophage-mediated tumoricidal activity in vitro eradicating tumor metastasis in vivo, as well as protecting animals from a wide variety of microbial and viral infections. Although the demands of solving the scientific and technical problems associated with liposome development are substantial, the rapid rate of progress in biology and in pharmaceutical sciences enhances the prospect of success for at least several aspects of liposome-mediated drug delivery. The next few years will be crucial in determining whether the commercial development of liposomes is feasible or whether they will join the ranks of other drug carrier designs that have failed to fulfill their initial promise.

Lysosomal elastase and cathepsin G in beige mice. Neutrophils of beige (Chediak-Higashi) mice selectively lack lysosomal elastase and cathepsin G

A profound decrease in activities of the two lysosomal serine proteinases, elastase, and cathepsin G, was found in neutrophils of four independent beige mutants. Elastase and cathepsin G activities were assayed with the specific synthetic substrates MeO-Suc-Ala-Ala-Pro-Val-MCA and Suc-Ala-Ala-Pro-Phe-pNA, respectively. The defect is intrinsic to cells of beige mice, since transplantation of bone marrow from normal to mutant mice restored normal proteinase activity, and normal mice transplanted with beige marrow produced neutrophils with a deficiency of proteinase activity. The loss of elastase and cathepsin G activity was confirmed by separation of [3H]diisopropylfluorophosphate-labeled proteins on denaturing gels, which also revealed that other serine proteinases are at normal levels in beige neutrophil extracts. The deficiency of lysosomal proteinase activity appears specific, in that four other common neutrophil lysosomal enzymes, plus the spectrum of major neutrophil proteins are not affected by the beige mutation. The deficiency of proteinase activity is likely not the primary genetic alteration of the beige mutation, since more than one proteinase is affected, and heterozygous F1 mice have normal rather than intermediate levels of both proteinases. The lowered proteinase activity may contribute to the high susceptibility of beige mice and Chediak-Higashi patients to infection.