Schistosoma mansoni and Schistosoma haematobium: Differences in development

Growth and maturation of the Puerto Rico strain of Schistosoma mansoni in mice and the Ghana strain of Schistosoma haematobium in hamsters were compared beginning 19 days after infection. In S. mansoni, optimum development was determined, with copulation first observed on Day 25, egg shell protein formation observed on Day 28, and oviposition occurring on Day 30. In infections of S. haematobium, copulation first occurred on Day 29. Egg shell proteins were first formed on Day 45, and egg production occurred on Day 60. Examination of unisexual and bisexual infections showed that maturation of the vitellaria can be more easily assessed by autofluorescence of the protein globules than by the traditional diazonium salt stains. Autofluorescence of living worms with mature vitellaria allows subsequent examination by electron microscopy, and therefore permits evaluation at a subcellular level.     

Occurrence of an agglutinin in Schistosoma mansoni

A membrane-associated component found in Schistosoma mansoni agglutinates untreated mouse and rat erythrocytes and seems to be a host-independent worm membrane receptor. Its possible role in the host-parasite adaptation mechanism is discussed.     

Histochemical lipid studies on Schistosoma mansoni adults maintained in situ and in vitro

Haseeb M. A., Eveland L. K. and Fried B. 1984. Histochemical lipid studies on Schistosoma mansoni adults maintained in situ and in vitro. International Journal for Parasitology14: 83–88. Schistosoma mansoni male and female adults were incubated at 37°C for 0.5 and 1.0 h in Earle's balanced salt solution containing 0.1% glucose and 0.5% lactalbumin hydrolysate, then examined by histochemistry and scanning electron microscopy. Histochemical analysis of cryostat sections stained with Oil Red O showed that males contain neutral lipid mainly in the parenchyma and tubercles, while females contain neutral lipid in the vitellaria. Neutral lipids are released from the tubercles of both paired and unpaired males maintained in vitro. There is evidence of in situ lipid transfer from males to blood vessel walls. Neutral lipid was not seen in females from unisexual infections. Sudan Black B staining fo total lipids is positive in tubercles, parenchyma, and vitellaria. Nile Blue Sulphate stains acidic lipids in male caecal walls. Scanning electron microscopy reveals no tegumental damage.     

Schistosoma mansoni and Fasciola hepatica: Cross-resistance in mice

Cross-resistance in Schistosoma mansoni and Fasciola hepatica infections were studied in mice. A primary infection of S. mansoni, 7 to 28 days old, did not stimulate a significant level of resistance to heterologous challenge with F. hepatica. In contrast, in older S. mansoni infections (54–65 days old) there was a significant level of resistance to a challenge with F. hepatica. The F. hepatica worm burden was reduced by 34.0 to 72.5% in separate experiments. Challenge infection with F. hepatica did not influence the number of S. mansoni in primary infections. No heterologous resistance to S. mansoni was found in mice with 7- and 23-day-old F. hepatica infections. However, primary infections with F. hepatica, 28, 32, 42, and 50 days old, conferred significant resistance to a heterologous challenge with S. mansoni. The established schistosome worm burden was reduced by 41.5 to 50.4%. In no case was the primary F. hepatica burden reciprocally influenced by challenge infection with S. mansoni.     

Antibody-dependent murine macrophage-mediated damage to Schistosoma mansoni schistosomula in vitro

Antibody-dependent cell-mediated cytotoxicity (ADCC) against schistosomula of the human parasite Schistosoma mansoni was demonstrated using antisera from mice plus peritoneal exudate cells (PEC). PEC were divided into plastic-adherent (96% macrophages, 4% lymphocytes) and nonadherent (92% lymphocytes, 8% macrophages) cell populations. Four criteria of ADCC were used, including minimal and maximal cell attachment, and death of and uptake of trypan blue by schistosomula. Using cells from normal mice and antisera from schistosome-infected mice, macrophages adhered to, damaged the tegument and underlying structures of, and killed schistosomula when observed following 18 hr incubation. In homologous systems, the results were similar when outbred CD-1 and inbred BALB/c mice were compared, except that potency of antisera from the latter mice decreased after 6–7 weeks postinfection, whereas the opposite was true for the former strain of mice. Nonadherent cells also exhibited ADCC against schistosomula, but the potency was considerably lower than that of adherent cells. These complement-independent ADCC reactions were stage-specific for the schistosomulum in that no reactions occurred with adult worms.     

Schistosoma mansoni Annexin 2: Molecular characterization and immunolocalization

We here describe the cloning and characterization of the Schistosoma mansoni Annexin 2, previously identified in the tegument by proteomic studies, and as an up-regulated gene in schistosomulum stage by microarray data. In silico analysis predicts a conserved core containing four repeat domains of Annexin (ANX) and a variable N-terminal region similar to that described for mammalian isoforms. Real-time RT-PCR and Western blot analysis determined that S. mansoni Annexin 2 is significantly up-regulated in the transition from free-living cercaria to schistosomulum and adult worm parasitic stages. Immunolocalization experiments and tegument membrane preparations confirmed Annexin 2 as a protein mainly localized in the tegument of schistosomula and adult worms. Furthermore, it binds to the tegument surface membranes in a calcium-dependent manner. These results suggest that S. mansoni Annexin 2 is closely associated to the tegument arrangement, being a potential target for immune intervention.     

Effects of UVB on interactions between Schistosoma mansoni and Biomphalaria glabrata

Ultraviolet B (UVB, 280-315 nm) radiation is detrimental to both of larvae of the digenetic trematode Schistosoma mansoni and its snail intermediate host, Biomphalaria glabrata. We explored effects of UVB on three aspects of the interaction between host and parasite: survival of infected snails, innate susceptibility and resistance of snails to infection, and acquired resistance induced by irradiated miracidia. Snails infected for 1 week showed significantly lower survival than uninfected snails following irradiation with a range of UVB intensities. In contrast to known immunomodulatory effects in vertebrates, an effect of UVB on susceptibility or resistance of snails to infection could not be conclusively demonstrated. Finally, exposure of susceptible snails to UVB-irradiated miracidia failed to induce resistance to a subsequent challenge with nonirradiated miracidia, a result similar to that reported previously with ionizing radiation.     

Transfer of Schistosoma mansoni into the mesenteric veins of hamsters

A simple and rapid procedure for the transfer of schistosomes into the mesenteric veins of hamsters is described. Recovery of worms was equally high (67%) for schistosomes grown in the hamster and for those grown in the mouse, while it was only slightly lower for rat worms (63%). Survival of recipient hamsters was 80%. The transfer procedure did not seem to affect the normal development of worms and led to a rapid recovery of rat worms with resumption of their egg-laying capacity. The potential usefulness of the method is outlined, with special emphasis on its recommended use for schistosome genetics.     

Schistosoma mansoni and Schistosoma haematobium: Emergence of schistosome cercariae from snails with darkness and illumination

Biomphalaria glabrata and Bulinus globosus were infected with Schistosoma mansoni and Schistosoma haematobium, respectively, and the effect of different illumination conditions at 25 C on cercarial output was observed for 4 days. In both species, a dark period of 10–14 hr on Day 2 of the observation period resulted in an emergence pattern on Day 3 similar to the regular pattern recorded for Day 1. Total cercarial output on Day 3 was within 30% of the control (Day 1) output. A dark period of between 0 and 8 hr resulted in suppression of cercarial emergence and in abolishment of the regular hourly emergence pattern on Day 3. A dark period of 16–20 hr resulted in an emergence pattern with two peaks, the first occurred at Hour 1, and the other at Hour 5 of the subsequent light period. Interjection of a 1-hr dark period during the light period of Day 3, following short (2–8 hr) exposure to dark on the preceding day, produced an increase in cercarial shedding of S. mansoni immediately after restitution of the light conditions. On the other hand, in S. haematobium, cercarial output was stimulated during the interposed dark period itself.     

Accumulation of lipids in Schistosoma mansoni sporocysts cultured in vitro

Neutral lipids were detected histochemically in mother and daughter sporocysts of Schistosoma mansoni cultured in vitro. These lipids progressively increased with prolonged culture. There was little phospholipid and no fatty acid, esterases, or lipases found in sporocysts by the methods employed. Mother and daughter sporocysts incorporated labeled acetate from the culture medium but no further information was obtained on the complex lipid-synthesizing capabilities of these organisms.     

Schistosoma haematobium and Schistosomiasis mansoni: Production of an estradiol-related compound detected by elisa

Estradiol is a steroid hormone secreted principally by the ovarian follicles in vertebrate animals. We have identified the production of an estradiol-related molecule in the trematodes Schistosoma haematobium and Schistosomiasis mansoni. We show in this work that this molecule related to estradiol is present in schistosome worm extracts. The detection method ELISA specific for estradiol, revealed the expression of this estradiol-related molecule in schistosome worm extracts, but not in Fasciola hepatica worm extracts. Our results demonstrate for the first time the production of an estradiol-related compound by a human parasite of the genus Schistosoma.     

Biomphalaria glabrata amoebocytes: Effect of Schistosoma mansoni infection on in vitro phagocytosis

The rate of phagocytosis by amoebocytes obtained from hemolymph of the pulmonate Biomphalaria glabrata infected with the trematode Schistosoma mansoni for 24 hr and 2, 4, and 6 weeks has been determined using the monolayer assay system. Amoebocyte preparations from snails infected for 4 and 6 weeks showed a gradual decrease in the phagocytic rates compared to those from uninfected controls. Snails harboring the parasite for 4 and 6 weeks also showed a significant increase in the number of amoebocytes in the hemolymph. No significant changes were detected in the rate of phagocytosis or number of amoebocytes in snails infected for 2 weeks or less. Alterations in the morphology and behavior of amoebocytes from infected snails were also noted.     

Effect of amphotericin B on the infection success of Schistosoma mansoni in Biomphalaria glabrata

In the present study, we examined the effect of amphotericin B on larval stages (miracidia and primary sporocyst) of the helminth Schistosoma mansoni, the causative agent of human schistosomiasis. Amphotericin B (AmB) is a polyene macrolide that disturbs the function of the cell membrane; it is widely used as prophylactic antimycotic agent in in vitro culture. We show for the first time that S. mansoni miracidia infectivity is considerably reduced after AmB treatment. Moreover we demonstrate that AmB does not affect the development, growth, viability, and behavior of miracidia and primary sporocysts. Our data indicate that AmB effects on S. mansoni sporocyst prevalence are linked to the oxidative properties of AmB. These may alter the capacity of sporocysts to respond to the oxidative stress generated by the snail immune defence system.     

The extracellular release of Schistosoma mansoni HMGB1 nuclear protein is mediated by acetylation

Schistosoma mansoni HMGB1 (SmHMGB1) was revealed to be a substrate for the parasite histone acetyltransferases SmGCN5 and SmCBP1. We found that full-length SmHMGB1, as well as its HMG-box B (but not HMG-box A) were acetylated in vitro by SmGCN5 and SmCBP1. However, SmCBP1 was able to acetylate both substrates more efficiently than SmGCN5. Interestingly, the removal of the C-terminal acidic tail of SmHMGB1 (SmHMGB1ΔC) resulted in increased acetylation of the protein. We showed by mammalian cell transfection assays that SmHMGB1 and SmHMGB1ΔC were transported from the nucleus to the cytoplasm after sodium butyrate (NaB) treatment. Importantly, after NaB treatment, SmHMGB1 was also present outside the cell. Together, our data suggest that acetylation of SmHMGB1 plays a role in cellular trafficking, culminating with its secretion to the extracellular milieu. The possible role of SmHMGB1 acetylation in the pathogenesis of schistosomiasis is discussed.     

Acquired resistance in snails. Induction of resistance to Schistosoma mansoni in Biomphalaria glabrata

Acquired resistance to Schistosoma mansoni PR-I strain has been induced in Biomphalaria glabrata 442132 strain by infecting the snails with irradiated homologous miracidia. Present and previous results support the hypothesis that acquired resistance to trematodes in snails is an enhancement of the host's natural resistance to the parasite.     

Schistosoma mansoni and S. haematobium: Calcium metabolism of the vitelline cell

The mature vitelline cell in Schistosoma mansoni and S. haematobium contains inclusions identified as calcareous corpuscles. They originate in the dilated cisternae of the granular endoplasmic reticulum and are eventually released when the vitelline cell starts to disintegrate in the fully formed egg capsule. X-ray microprobe analysis of single-fixed but conventionally prepared specimens, as well as of material quenched in liquid nitrogen slush and cryosectioned, indicated that the corpuscles contained phosphorus, calcium, and magnesium. The debris surrounding the developing embryo within the egg capsule also contained the elements phosphorus and calcium. Dosage of infected mice with Astiban produced an increase in total calcium content.