Cytokine profile and nitric oxide levels in peritoneal macrophages of BALB/c mice exposed to the fucose-mannose ligand of Leishmania infantum combined with glycyrrhizin

Hasan Namdar Ahmadabad,Reza Shafiei,Gholam Reza Hatam,Reza Zolfaghari Emameh,Ashok Aspatwar

doi:10.1186/s13071-020-04243-7

Abstract

BackgroundThe fucose-mannose ligand (FML) of Leishmania infantum is a complex glycoprotein which does not elicit adequate immunogenicity in humans. In recent years, adjuvant compounds derived from plants have been used for improving the immunogenicity of vaccines. Glycyrrhizin (GL) is a natural triterpenoid saponin that has known immunomodulatory activities. In the present study, we investigated the effects of co-treatment with FML and GL on the production of cytokines and nitric oxide (NO) by macrophages, in vitro.MethodsLipopolysaccharide (LPS) stimulated murine peritoneal macrophages were treated with FML (5 μg/ml) of L. infantum and various concentrations of GL (1 μg/ml, 10 μg/ml and 20 μg/ml). After 48 h of treatment, cell culture supernatants were recovered and the levels of TNF-α, IL-10, IL-12p70 and IP-10 were measured by sandwich ELISA and NO concentration by Griess reaction.ResultsOur results indicate that the treatment of activated macrophages with FML plus GL leads to enhanced production of NO, TNF-α and IL-12p70, and reduction of IL-10 levels in comparison with FML treatment alone.ConclusionsTherefore, we concluded that GL can improve the immunostimulatory effect of FML on macrophages and leads to their polarization towards an M1-like phenotype.

Highlights

The fucose-mannose ligand (FML) of Leishmania infantum is a complex glycoprotein which does not elicit adequate immunogenicity in humans
We considered three control groups: (i) phosphate-buffered saline (PBS) group: activated macrophages were cultured in the presence of PBS alone at the same volume as the other additions (10 μl/ml); (ii) GL group: activated macrophages treated with GL (5 μg/ml); and (iii) FML group: activated macrophages treated with FML (5 μg/ml)
Results of the microwave theory and techniques (MTT) assay indicated that co-treatment of macrophages with FML (5 μg/ml) and GL (1, 10 and 20 μg/ml) had no cytotoxic effect on the activated macrophages, these concentrations were used for the nitric oxide (NO) and cytokine assay

Summary

Introduction

The fucose-mannose ligand (FML) of Leishmania infantum is a complex glycoprotein which does not elicit adequate immunogenicity in humans. The disease is caused by parasitic protozoan species of the Leishmania donovani complex. The parasites have developed resistance to existing drugs; due to this and the lack of an effective human vaccine against VL, there has been an increase in the incidence of VL [6,7,8,9]. Among the various antigens that serve as targets for VL vaccine design, fucose-mannose ligand (FML) has attracted much attention owing to its excellent immunoprotective properties against experimental VL in several animal models [13]. The FML is a glycoprotein antigen which is present both in amastigotes and in motile promastigotes of species in the L. donovani complex. Even though the FML is a potent immunogen in rabbits and dogs (e.g. Leishmune®, a vaccine for canine VL consisting of FML and saponin) [14], it does not have adequate immunogenicity in humans [9, 15]

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