Ultrastructural study of the in vitro interaction between Biomphalaria glabrata hemocytes and Schistosoma mansoni miracidia

Abstract

Biomphalaria glabrata and Schistosoma mansoni relationship was studied by light microscopy (LM) and freezefracture replica technique (FFR). We observed very thin cytoplasmic extensions of hemocytes in the LMMorphological and ultrastructural methods previously employed for the characterization of vertebrate immune systems (macrophages, lymphocytes, and polymorphonuclears) under normal conditions and parasitic infections were used for identifying mollusc hemocytes (Sminia & Barendsen 1980, Ottaviani & Franchini 1988, Abdul-Salam & Michelson 1980, Barracco et al. 1993. It has been lately suggested that some bacteria toxins are able to induce the re-arranging of Rho superfamily proteins and cytoskeleton alterations (stress fibers) in epithelial cells (Brest et al. 2003). These findings indicate a new perspective for studying the mechanisms mediating the B. glabrata hemocyte and S. mansoni larval interaction.The aim of this investigation was to study ultrastructural aspects of the interaction between B. glabrata hemocyte and S. mansoni occurring at the cellular membrane level. For this purpose, a useful methodology for the ultrastructural characterization of membrane systems, the freeze-fracture replica technique (FFR) was used. MATERIALS AND METHODSMiracidia -S. mansoni eggs were purified from the liver and gut sections of hamsters (Mesocricetus auratus) 7 weeks after infection. Briefly, dissected organs were enzymatically digested (0.25% trypsin and 0.05% collagenase in 0.15 M PBS, pH 7.2) then eggs were purified by shifting through metallic meshes, decreasing in size from 420 to 44 µm. Eggs were collected and hatched under sterile conditions, and the resulting miracidia were sedimented at 4 o C as described by Césari and Alarcón de Noya (1987). All the animals used in this study were sacrificed in accordance to Venezuelan laws for animal care.Cytoadherence -Hemocytes were obtained from B. glabrata between 7 and 10 mm diameter. Molluscs were externally rinsed with 25% isopropylic alcohol and then

Differences in the number of hemocytes in the snail host Biomphalaria tenagophila, resistant and susceptible to Schistosoma mansoni infection

“…Therefore, the suggestion that the hemocytes may also carry out tissue-repair activities can be taken as an alternative explanation for the observation of a similar reduction in hemocytes in the two strains during the first 2 h after infection. These results may be considered consistent, since Araque et al (2003) observed that a similar migration occurs in resistant and susceptible mollusk strains, especially at the beginning of the interaction with the parasite.…”

Morphology and kinetics of susceptible and resistant Biomphalaria alexandrina hemocytes during the first week of exposure to Schistosoma mansoni miracidia

“…This finding was in agreement with de Melo et al [32] , who stated that the response at the 1 st DPO was more potent than the response during earlier stages of host-parasite interaction. According to Araque et al [33] , the early migration of hemocytes to the internal tissues happens regardless of snail-parasite compatibility status. After this stage, the process of parasite infection differs between susceptible and resistant snails, where, resistant snails recognize the parasites as non-self, thus forming a strong connection between snails' hemocytes and the parasite, leading to persistence of the hemocytes in resistant snails' tissues for a longer time than in case of susceptible snails [28] .…”