Biomphalaria glabrata embryonic cell- Schistosoma mansoni sporocyst surface membrane interactions

Schistosoma mansoni, the causative agent of hepatosplenic schistosomiasis, is one of three major species of schistosomes affecting over 200 million people around the world. This blood fluke requires two hosts to complete its life cycle, a mammalian definite host, and a freshwater snail such as Biomphalaria glabrata, as the intermediate host. Understanding the molecular interactions between snails and their larval schistosomes is important as the snail is a potential target in the control and eradication of schistosomiasis.; The innate immune system of B. glabrata consists of humoral and cellular components, of which the circulating hemocytes are major players in response to schistosome infections. In resistant strains of B. glabrata, hemocytes recognize, migrate to, attach, and form a cellular capsule around invading S. mansoni sporocysts, culminating in the destruction of the parasite. Little is known about the molecules involved in this immune process, including the initial recognition and adhesion of snail cells to the sporocysts surface. The purpose of these studies was to better understand the molecular interactions between S. mansoni sporocysts and its snail host cells, especially those occurring during the early stages of infection. For this purpose, the hemocyte-like B. glabrata embryonic (Bge) cell line was used to test the involvement of lectin or lectin-like molecules in the attachment of host cells to the tegumental surface of primary sporocysts, and to aid in the identification and isolation of potential snail cell receptors involved in the recognition and larval attachment processes. Results of these studies have revealed the involvement of carbohydrate moieties in the interactions of Bge cells and hemocytes with primary sporocysts of S. mansoni suggesting the presence of lectin-like receptor(s) on snail cells. Negative charge in the form of sulfate or phosphate groups in addition to the presence of fucosyl residues are important characteristics of carbohydrate ligand(s) recognized by Bge cell receptors. Bge cells and snail hemocytes have cell surface receptor(s) specific for fucoidan. Finally, a membrane Hsp60 homologue was identified at the surface of Bge cells and in hemocytes that bind LacdiNAc and fucosylated LacdiNAc terminal glycans associated with the tegument of S. mansoni sporocysts.