title: Protective effect of neoglycoprotein-conjugated muramyl dipeptide against Leishmania donovani infection: the role of cytokines.
abstract: Active targeting of muramyl dipeptide (MDP) to macrophages was studied by conjugation with the neoglycoprotein, mannosyl human serum albumin (mannose-HSA) using visceral leishmaniasis as the model macrophage disease. Conjugation did not decrease the affinity of the neoglycoprotein for macrophage mannose receptor. Mannose-HSA-MDP was 50 times more efficient than free MDP in inhibiting the growth of Leishmania donovani inside peritoneal macrophages. Moreover, in a 60-day murine model of visceral leishmaniasis, 95% of the spleen parasite burden was reduced by mannose-HSA-MDP at a dose of 0.5 mg/kg/day given for 4 days. Free MDP at a similar dose had very little effect. In vitro exposure of MDP caused enhanced generation of O2- by macrophages, whereas generation of nitric oxide (NO) was not induced. The elevated antileishmanial activity of MDP-treated macrophages in culture was abrogated by O2- scavengers. In contrast, considerably enhanced amounts of NO and O2- were generated from macrophages of mannose-HSA-MDP-treated animals, and their splenocytes secreted soluble factors providing all the signals required for the induction of NO biosynthesis. The increase in NO production was paralleled by a concomitant increase in antileishmanial activity, which was reversed by NO synthesis inhibitors. Splenocyte supernatants treated with anti-IFN-gamma or anti-TNF-alpha Abs suppressed inducible NO generation by macrophages. Moreover, i.v. administration of anti-IFN-gamma and anti-TNF-alpha along with mannose-HSA-MDP greatly reduced protection against L. donovani infection. Neoglycoprotein-conjugated MDP, therefore, activated mouse macrophages in vivo to kill L. donovani, and this may depend on the physiologic generation of NO induced by IFN-gamma and TNF-alpha.
authors.affiliation: Molecular Cell Biology Laboratory, Indian Institute of Chemical Biology, Calcutta, India.
authors.forename: K
authors.initials: K
authors.lastname: Sarkar
authors.forename: P K
authors.initials: PK
authors.lastname: Das
mesh_terms: D000119:Acetylmuramyl-Alanyl-Isoglutamine / Q000008:administration & dosage*; D000276:Adjuvants, Immunologic / Q000008:administration & dosage*; D000818:Animals; D002478:Cells, Cultured; D004337:Drug Carriers; D006023:Glycoproteins / Q000008:administration & dosage*; D006801:Humans; D007111:Immunity, Cellular; D007893:Leishmania donovani; D007898:Leishmaniasis, Visceral / Q000188:drug therapy* / Q000276:immunology; D008262:Macrophage Activation / Q000187:drug effects; D008264:Macrophages / Q000187:drug effects / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C
chemical_list: D000276:Adjuvants, Immunologic; D004337:Drug Carriers; D006023:Glycoproteins; D000119:Acetylmuramyl-Alanyl-Isoglutamine