Characterisation of the Native Lipid Moiety of Echinococcus granulosus Antigen B

Abstract

Antigen B (EgAgB) is the most abundant and immunogenic antigen produced by the larval stage (metacestode) of Echinococcus granulosus. It is a lipoprotein, the structure and function of which have not been completely elucidated. EgAgB apolipoprotein components have been well characterised; they share homology with a group of hydrophobic ligand binding proteins (HLBPs) present exclusively in cestode organisms, and consist of different isoforms of 8-kDa proteins encoded by a polymorphic multigene family comprising five subfamilies (EgAgB1 to EgAgB5). In vitro studies have shown that EgAgB apolipoproteins are capable of binding fatty acids. However, the identity of the native lipid components of EgAgB remains unknown. The present work was aimed at characterising the lipid ligands bound to EgAgB in vivo. EgAgB was purified to homogeneity from hydatid cyst fluid and its lipid fraction was extracted using chloroform∶methanol mixtures. This fraction constituted approximately 40–50% of EgAgB total mass. High-performance thin layer chromatography revealed that the native lipid moiety of EgAgB consists of a variety of neutral (mainly triacylglycerides, sterols and sterol esters) and polar (mainly phosphatidylcholine) lipids. Gas-liquid chromatography analysis showed that 16∶0, 18∶0 and 18∶1(n-9) are the most abundant fatty acids in EgAgB. Furthermore, size exclusion chromatography coupled to light scattering demonstrated that EgAgB comprises a population of particles heterogeneous in size, with an average molecular mass of 229 kDa. Our results provide the first direct evidence of the nature of the hydrophobic ligands bound to EgAgB in vivo and indicate that the structure and composition of EgAgB lipoprotein particles are more complex than previously thought, resembling high density plasma lipoproteins. Results are discussed considering what is known on lipid metabolism in cestodes, and taken into account the Echinococcus spp. genomic information regarding both lipid metabolism and the EgAgB gene family.

In Vitro and In Vivo Effects of Tamoxifen against Larval Stage Echinococcus granulosus

“…Tapeworms, like flukes, lack the ability to synthesize cholesterol de novo, and until now there has been no conclusive research on the biosynthesis of estrogens, progesterone, and androgens in cestodes (17). Metabolic and transcriptomic studies have demonstrated that sterol synthesis in E. granulosus is interrupted at the level of farnesyl or nerol-idol pyrophosphate, that the cholesterol derives from the host, and that for signaling actions, the host sterols may be modified by the parasite (38). But it is highly likely that if Echinococcus spp.…”

Characterisation of Antigen B Protein Species Present in the Hydatid Cyst Fluid of Echinococcus canadensis G7 Genotype

“…2-DGE and MS analysis was performed as described previously [38] but using 150 μg (protein) of the AgB-enriched fraction (QS f ) for the electrofocusing step in order to detect poorly represented subunits. Briefly, the first dimension was performed with commercially available IPG-strips (7 cm, linear 3–10, GE Healthcare).…”

“…AgB total lipids were analysed using Ld f (between 0.25 and 0.5 mg of protein) following the methodology that we have already described [38]. Qualitative analysis of lipid classes was performed by HPTLC using double development for neutral and polar lipids as described previously [38], but lipid bands were visualised under iodine vapour.…”

“…Qualitative analysis of lipid classes was performed by HPTLC using double development for neutral and polar lipids as described previously [38], but lipid bands were visualised under iodine vapour. Identification of lipid classes was performed by comparison with primary and secondary standards run on the same HPTLC plate.…”

Total Lipids Estimation and Fatty Acids Analysis of Bothriocephalus Acheilognathi, a Parasitic Tapeworm of the Common Carp Cyprinus Carpio (L., 1758) From Tigris River-Mosul City

“…For the same reason, using fatty materials as energy sources is expensive for tapeworms (Obal et al,2012).…”