The schistosome in the mammalian host: understanding the mechanisms of adaptation

Abstract

In this review, we envisage the host environment, not as a hostile one, since the schistosome thrives there, but as one in which the relationship between the two organisms consists of constant communication, through signalling mechanisms involving sense organs, surface glycocalyx, surface membrane and internal organs of the parasite, with host fluids and cells. The surface and secretions of the schistosome egg have very different properties from those of other parasite stages, but adapted for the dispersal of the eggs and for the preservation of host liver function. We draw from studies of mammalian cells and other organisms to indicate how further work might be carried out on the signalling function of the surface glycocalyx, the raft structure of the surface and existence of pores in the surface membrane, the repair of the surface membrane, the role of the membrane structure in ion channel function (including recent work on the actin cytoskeleton and calcium channels) and the possible role of P-glycoproteins in the adaptation of the parasite to its environment. We are speculative in some areas, such as the suggestions that variability in surface properties of schistosomes may relate to the existence of membrane rafts and that parasite communities may exhibit quorum sensing. This speculative approach is adopted with the hope that future work on the whole organisms and their interactions will be encouraged.

Immunostimulatory property of a synthetic peptide belonging to the soluble ATP diphosphohydro-lase isoform (SmATPDase 2) and immunolocalisation of this protein in the Schistosoma mansoni egg

“…IgG2a, a Th1 cytokine-derived isotype, has been described as being protec tive against schistosomula and adult worms, possibly through antibody-dependent cell cytotoxic mechanisms, whereas IgG1, a Th2 cytokinederived isotype, has been associated with the immunomodulation of the granulomatous inflammation in schistosomiasis (Mountford et al 1994, Coelho et al 1996, James et al 1998, Zouain et al 2000, Carvalho-Queiroz et al 2004, Kusel et al 2007. The epitopes within soluble ATP diphosphohydrolase from the S. mansoni egg described here, as well as within SmATPDase 2 from the cercariae, schistosomula and adult worm (Levano-Garcia et al 2007), could be related to the success of the parasitism through disease immunomodulation during the course of the parasitic infection.…”

“…Identification and characterisation of epitopes within an antigenic protein may help select components for the development of a defined vaccine against schistosomiasis or for diagnostic purposes (Kusel et al 2007. In this study, a peptide (SmB2LJ) that belongs to a conserved domain from S. mansoni SmATPDase 2, shared with potato apyrase, was synthesised and its immunostimulatory capability was analysed.…”

Structure–function analysis of apical membrane‐associated molecules of the tegument of schistosome parasites of humans: prospects for identification of novel targets for parasite control

“…The tegument is a highly polarized syncytium and possesses functional analogy with transporting epithelia, including the gut lining or the syncytiotrophoblasts of the human placenta. The tegument plays significant roles in nutrient uptake, immune evasion and modulation, excretion, osmoregulation, sensory reception, and signal transduction (Jones et al, 2004;Kusel et al, 2007;Castro-Borges et al, 2011). Given the importance of the schistosome tegument in nutrition and immune evasion, proteins of this surface layer are recognized as prime candidates to target for vaccine and therapeutic drug development (Loukas et al, 2007).…”

Detection of IgG1 and IgG4 subtypes reactive against potato apyrase in schistosomiasis patients

“…Analyses of antibody responses to specific antigens demonstrated high IgG2 and IgG4 antibody levels associated with the slow development of immunity to S. mansoni re-infection AT. In contrast, individuals who were resistant to S. mansoni infection and re-infection and living in schistosomiasis endemic areas, produced high levels of IgG1 and IgG3 antibodies and the results were correlated with parasite elimination (Corrêa-Oliveira et al 2000, Mutapi 2001, Kusel et al 2007. These variations in humoral responses between different individuals could be explained by age, sex, nutrition, parasite load and/or host genetic factors (Mutapi 2001).…”

“…Recently, the gene of another S. mansoni ATP diphosphohydrolase isoform was reported and its soluble protein form was demonstrated to be secreted from the adult worm tegument (Levano-Garcia et al 2007. Egg-derived antigens have also been intensively investigated (Kusel et al 2007) and both membrane-associated and soluble ATP diphosphohydrolase isoforms have been identified in S. mansoni eggs (Faria-Pinto et al 2004).…”