Angiogenesis and parasitic helminth-associated neovascularization.

Successful metazoan parasitism, among many other factors, requires a supply of nutrients and the removal of waste products. There is a prerequisite for a parasite-defined vasculature. The angiogenic mechanism(s) involved presumably depend on the characteristics of the tissue- and vascular system-dwelling, parasitic helminths. Simplistically, 2 possibilities or a combination of both have been considered in this review. The multifactorial induction of parasitic helminth-associated neovascularization could arise through, either a host-, a parasite- or a host-/parasite-dependent, angiogenic switch. Most studies appear to support the first and third hypotheses, but evidence exists for the intrahepatic cestode Echinococcus multilocularis, the free-living nematode Caenorhabditis elegans and the intravascular trematode Schistosoma mansoni for the second inference. In contrast, the nematode anti-coagulant protein NAPc2 from adult Ancylostoma caninum is also an anti-angiogenic factor.

Characterisation and partial purification of Schistosoma mansoni egg-derived pro-angiogenic factor.

Pathogenesis of Schistosoma mansoni infection is due to the accumulation of eggs in the liver and intestine of the host followed by granuloma formation and fibrosis at the site of egg embolism. Nevertheless, total hepatic blood flow and hepatic function appear to be maintained by neovascularisation of the periportal fibrotic tissue. Here we demonstrate that intact live eggs, excretory/secretory products of eggs and the extracts of homogenised eggs stimulate the proliferation and migration of endothelial cells. Formation of endothelial capillary-like outgrowths, as well as, the activation of p42/p44 mitogen-activated protein kinase signal transduction pathway was stimulated by egg extracts, whereas other stages of the schistosome life-cycle did not exhibit such activity. We have characterised and partially purified the pro-angiogenic factor. The active pro-angiogenic component was fast-acting, heat-stable, protease-resistant, weakly heparin-binding and a non-lipid. It could be extracted with acidified ethanol or a hot acetic acid solution and could be partially purified by reverse-phase HPLC. The S. mansoni egg-derived pro-angiogenic factor, described here, may directly contribute to vascular remodelling in the liver and illustrates how helminth parasites may modulate angiogenesis.

The parasitic trematode Fasciola hepatica exhibits mammalian-type glycolipids as well as Gal(beta1-6)Gal-terminating glycolipids that account for cestode serological cross-reactivity.

Neutral glycosphingolipids from sheep-derived Fasciola hepatica liver flukes were isolated and characterized both structurally and serologically. After HPLC fractionation, glycolipids were analyzed by linkage analysis, enzymatic cleavage, and MALDI-TOF as well as electrospray ionization mass spectrometry. Obtained results revealed the presence of two types of neutral glycolipids. The first group represented mammalian-type species comprising globo- and isoglobotriaosylceramides (Gal(alpha1-4)Gal(beta1-4)Glc(1-1)ceramide and Gal(alpha1-3)Gal(beta1-4)Glc(1-1)ceramide, respectively) as well as Forssman antigen (GalNAc(alpha1-3)GalNAc(beta1-3/4)Gal(alpha1-4/3)Gal(beta1-4)Glc(1-1)ceramide). Applying Helix pomatia agglutinin, recognizing terminal alpha-linked GalNAc, to cryosections of adult flukes, the latter glycolipid could be localized to the F. hepatica gut. As Forssman antigen from the parasite and sheep host led to identical MALDI-TOF MS profiles, this glycolipid might be acquired from the definitive host. As a second group, highly antigenic glycolipids were structurally characterized as Gal(beta1-6)Gal(beta1-4)Glc(1-1)ceramide, Gal(beta1-6)Gal(alpha1-3/4)Gal(beta1-4)Glc(1-1)ceramide and Gal(beta1-6)Gal(beta1-6)Gal(alpha1-3/4)Gal(beta1-4)Glc(1-1)ceramide, the latter two structures of which exhibited both isoglobo- or globo-series core structures. Terminal Gal(beta1-6)Gal1-motifs have previously been shown to represent antigenic epitopes of neogala-series glycosphingolipids from tape worms. Using human Echinococcus granulosus infection sera, Gal(beta1-6)Gal-terminating glycolipids could be allocated to the gut in adult liver fluke cryosections. Corresponding neogala-reactive antibodies in F. hepatica infection serum were detected by their binding to E. granulosus and Taenia crassiceps neogala-glycosphingolipids. These antibodies might contribute to the known serological cross-reactivity between F. hepatica and parasitic cestode infections.

A novel GlcNAcalpha1-HPO3-6Gal(1-1)ceramide antigen and alkylated inositol-phosphoglycerolipids expressed by the liver fluke Fasciola hepatica.

The acidic (glyco)lipids of the parasitic liver fluke Fasciola hepatica exhibited two different phosphate-containing species, designated AL-I and AL-II, which were analyzed by MALDI-TOF MS, ESI MS, NMR, methylation analysis, and combined GC-MS in conjunction with HF treatment. AL-I was structurally determined as 1-O-hexadecyl-sn-glycerol-3-phosphoinositol, an ether bond variant of lysophosphatidylinositol. The structure of AL-II was shown to be GlcNAcalpha1-HPO3-6Gal(1-1)ceramide. Ceramide analysis revealed as major components 2-hydroxyoctadecanoic acid [18:0(2-OH)] together with C18- and C20-phytosphingosines. AL-II was apparently highly antigenic and strongly recognized by both animal- and human-F. hepatica infection sera. Furthermore, inhibition ELISAs revealed that the unusual antigenic determinant GlcNAcalpha1-HPO3- phosphate might have a potential in the serodiagnosis of F. hepatica infections.

Fuc(alpha1-->3)GalNAc-: the major antigenic motif of Schistosoma mansoni glycolipids implicated in infection sera and keyhole-limpet haemocyanin cross-reactivity.

The aim of the present study was the characterization of the dominant epitope present on Schistosoma mansoni glycolipids, which causes cross-reactivity of S. mansoni and S. haematobium infection sera with keyhole-limpet haemocyanin (KLH). To this end, the monoclonal antibody M2D3H was chosen for its similar behaviour in high-performance TLC immunostaining and inhibition-ELISA to infection sera. Individual, structurally defined oligosaccharides derived from S. mansoni egg glycolipids were tested for their binding to this monoclonal antibody by immunoaffinity chromatography. A terminal fucose residue linked in the (alpha1-->3) position to N-acetylgalactosamine was found to be the common structural determinant of the four oligosaccharides binding to M2D3H. The Fuc(alpha1-->3)GalNAc-motif also appeared to be the basis for the cross-reactivity with KLH, a phenomenon used in the serodiagnosis of S. mansoni, S. haematobium and S. japonicum infections.

Characterization of glycosphingolipids from Schistosoma mansoni eggs carrying Fuc(alpha1-3)GalNAc-, GalNAc(beta1-4)[Fuc(alpha1-3)]GlcNAc- and Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc- (Lewis X) terminal structures.

The carbohydrate moieties of glycosphingolipids from eggs of the human parasite, Schistosoma mansoni, were enzymatically released, labelled with 2-aminopyridine (PA), fractionated and analysed by linkage analysis, partial hydrolysis, enzymatic cleavage, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and nano-electrospray ionization mass spectrometry. Apart from large, highly fucosylated structures with five to seven HexNAc residues, we found short, oligofucosylated species containing three to four HexNAc residues. Their structures have been determined as Fuc(alpha1-3)GalNAc(beta1-4)[ +/- Fuc (alpha1-3)]GlcNAc(beta1-3)GalNAc(beta1-4)Glc-PA, GalNAc(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-3)GlcNAc(beta1-3)GalNAc(beta1-4) Glc-PA, Fuc(alpha1-3)GalNAc(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-4) GlcNAc(beta1-3)GalNAc(beta1-4)Glc-PA, and Fuc(alpha1-3) GalNAc(beta1-4)[ +/- Fuc(alpha1-2) +/- Fuc(alpha1-2)Fuc(alpha1-3)]Glc NAc(beta1-3)GlcNAc(beta1-3)GalNAc(beta1-4)Glc-PA. The last structure exhibits a trifucosyl sidechain previously identified on the cercarial glycocalyx. These structures stress the importance of 3-fucosylated GalNAc as a terminal epitope in schistosome glycoconjugates. To what degree these glycans contribute to the pronounced antigenicity of S. mansoni egg glycolipids remains to be determined. In addition, we have identified the compounds GlcNAc(beta1-3)GalNAc(beta1-4)Glc-PA, Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-3) GalNAc (beta1-4)Glc-PA, the latter of which is a Lewis X-pentasaccharide identical to that present on cercarial glycolipids, as well as Gal(beta1-3)GalNAc(1-4)Gal(1-4)Glc-PA, which corresponds to asialogangliotetraosylceramide and is most probably derived from the mammalian host.

Immunomodulatory properties of Ascaris suum glycosphingolipids - phosphorylcholine and non-phosphorylcholine-dependent effects.

Immunomodulatory properties of phosphorylcholine (PC)-containing glycosphingolipids from Ascaris suum were investigated utilizing immune cells from BALB/c mice. Proliferation of splenic B cells induced either via F(ab')2 fragments of anti-murine Ig (anti-Ig) or LPS was significantly reduced when the glycosphingolipids were present in the culture medium. However whereas the LPS-mediated effect was dependent on the PC moiety of the glycosphingolipids, the result generated when using anti-Ig was not. Analysis of cell cycle status and mitochondrial potential indicated that the combination of the glycosphingolipids and anti-Ig reduced B cell proliferation, at least in part, by inducing apoptosis. Consistent with the observed suppression of B cell activation/cell cycle progression, investigation of the effect of glycosphingolipid pre-exposure on mitogenic B cell signal transduction pathways activated by anti-Ig, revealed a PC-independent inhibitory effect on dual (thr/tyr) phosphorylation and activation of ErkMAPKinase. The glycosphingolipids were also investigated for their inhibitory effect on LPS/IFN-gamma induced Th1/pro-inflammatory cytokine production by peritoneal macrophages. It was found that IL-12 p40 production was inhibited and in an apparently PC-dependent manner. Overall these data indicate that PC-containing glycosphingolipids of A. suum appear to have at least two immunomodulatory constituents - PC and an as yet unknown component.