Immunolocalization of the fatty acid-binding protein Sj-FABPc within adult Schistosoma japonicum

This paper describes the first localization study of the 14.7 kDa fatty acid-binding protein in Schistosoma japonicum (SjFABPc) using transmission electron microscopy. A polyclonal antibody raised against recombinant Sj-FABPc was used in combination with a colloidal gold marker to determine the distribution of the protein within adult parasites. Sj-FABPc was localized within lipid droplets below the subtegumental region of the male parasite. Additionally, Sj-FABPc was present in the vitelline droplets of the vitelline glands of female parasites. There were no detectable levels of Sj-FABPc on the surface or within the tegument of male or female parasites. Possible functions of Sj-FABPc within S. japonicum and the relevance of these immunolocalization findings in light of the recent reports that the homologue Sm-FABPc is an important anti-S. mansoni vaccine target molecule are also discussed.

Schistosoma japonicum: immunolocalization of paramyosin during development

This paper describes the localization of paramyosin immunoreactivity in Schistosoma japonicum and represents the first comparative immunolocalization study among schistosome adult, cercariae and lung schistosomula by electron microscopy. A polyclonal antibody was utilized to immunolabel paramyosin or paramyosin-like proteins. Paramyosin was localized within the muscle layer of all 3 developmental stages. Furthermore, paramyosin was localized within granules of the post-acetabular glands of cercariae, and within the tegument matrix and surface of lung schistosomules. Adults and cercariae did not display any detectable paramyosin on the surface or within the tegument. The possible functions of paramyosin within S. japonicum and the relevance of these findings in relation to the reported protective properties of paramyosin as an anti-schistosome vaccine target molecule are discussed.

Tegument changes of Schistosoma japonicum and Schistosoma mansoni in mice treated with artemether

AIM

To study the effect of artemether (Art) on the tegument of schistosomes.

METHODS

Mice infected with S japonicum cercariae for 7 and 35 d, or with S mansoni cercariae for 49 d were treated intragastrically with Art 200-300 mg.kg-1.d-1 for 2 d. Schistosomes were collected in groups of 2 mice at various intervals after medication for scanning electron microscopic observation.

RESULTS

The tegumental changes induced by Art appeared to be similar in S japonicum and S mansoni: swelling and fusion of tegumental surfaces, vesicle formation and collapse of discoid-like sensory structures. In S japonicum the emergence of tegumental alterations was earlier in 7-d-old schistosomulae than that in 35-d-old adult worms.

CONCLUSION

Art injured the teguments of S japonicum and S mansoni.

Scanning electron microscope observation on tegumental damage of 21-d-old Schistosoma japonicum induced by praziquantel

AIM

To study the effect of praziquantel (Pra) on the tegument of 21-d-old schistosomula, mice infected with Schistosoma japonicum cercariae for 21 d were treated ig with Pra at a single dose.

METHOD

Groups of mice were killed at different intervals within 48 h, and the worms were collected by perfusion for scanning electron microscopic observation.

RESULTS

When the dose used was 300 mg.kg(-1), the worms showed mild or moderate swelling, fusion or even erosion and collapsed of the tegumental ridges, which was characterized by swelling of the discoid sensory structures. At higher dose of 500 mg.kg(-1), similar alterations in the worm surface were seen, but more extensive and serious. When Pra 500 mg.kg(-1) was given daily for 3 d, severe swelling, erosion and peeling of the tegument accompanied by the attachment of the host leukocytes on the damaged surface were seen.

CONCLUSION

Pra exhibited a direct killing effect on 21-d-old schistosomula.

Interaction of schistosome eggs with vascular endothelium

The interaction of schistosome eggs with venular endothelium was studied using primary cultures of human umbilical vein endothelial cells. Freshly oviposited and embryonated eggs of Schistosoma mansoni, Schistosoma japonicum, and Schistosoma haematobium were used. The cultures were evaluated by light, scanning, and transmission electron microscopy. Endothelial cell monolayers were found to retain eggs by actively migrating over those that came to lie on top of them. The monolayers then reestablished confluency and their lumenal polarity. Eggs deposited directly by adult worms elicited a more rapid and complete response than embryonated eggs isolated from the liver tissues of infected rodents or latex beads. Cell migration was shown to be more complete in the presence of sera than in serum-free media. It is concluded from these observations that eggs can be passively transferred to the perivenular space by the nonspecific response of endothelial cells.

Electron microscopic observations of tegumental damage in adult Schistosoma japonicum after in vivo treatment with levo-praziquantel

The in vivo effects of a single dose of levo-praziquantel, 75 mg/kg in PEG 400, on the tegumental surface of adult S. japonicum were compared with the effects of a single dose (150 mg/kg) of the mixed isomer preparation, using scanning and transmission electron microscope. Worms were recovered from mice at 10 min, 30 min, 1 hr, 4 hr, 12 hr, 24 hr and 48 hr after treatment. After 10 min exposure to either compound, the tegumental folds and sensory organelles were swollen and the tegument vacuolated. After 12-24 hr, the surface was eroded and exfoliated with exposure of intrategumental and/or subtegumental tissues and attachment of leukocytes to the denuded areas. Vehicle controls were normal throughout the time period examined. These studies demonstrate that the levo isomer of praziquantel causes acute structural damage to the tegument similar to that seen with the mixed isomer preparation.

Ultrastructural observations on cercaria of Schistosoma japonicum

The present paper describes the ultrastructure of the surface topography, head organ, tegument, musculature, glandular system, primary alimentary tract and flame cells of the Chinese mainland strain of Schistosoma japonicum cercaria, as visualized with both scanning and transmission electron microscopes. The results not only illustrate the morphological features of the cercarial surface and its internal structure reflecting an adaptation to the aqueous habitat but also reveal the correlation between the morphological structure and physiological function.

Demonstration of the target molecule of a protective IgE antibody in secretory glands of Schistosoma japonicum larvae

We have demonstrated that a mouse monoclonal IgE antibody, SJ18 epsilon.1, recognizes a 97 kDa surface molecule (Sj97) of Schistosoma japonicum larvae and that the antibody induces partial but significant protection against the skin to lung-stage of S. japonicum infection. The antibody stimulates eosinophil- and macrophage-mediated killing of schistosomula in vitro. In the present study, we isolated the putative full-length cDNA of Sj97 by screening a lambda gt11 cDNA library from S. japonicum adult worms with SJ18 epsilon.1. The predicted amino acid sequence of the cDNA showed highly significant homology to that of S. mansoni paramyosin, a potential vaccine candidate for schistosomiasis. The deletion mutants of S. japonicum paramyosin were expressed in Escherichia coli and the translation product of 443 amino acid residues of paramyosin was found to be recognized by the antibody. Moreover, we observed by immunoelectron microscopy the presence of paramyosin in the post-acetabular gland as well as in the tegument and muscle layers of the larvae. These results suggest that paramyosin is a secretory protein which may be incorporated into the tegument during the development of schistosomula, thus becoming a target for protective immunity during the migratory phase of the parasite.

Schistosoma japonicum: immunoinhibitory studies on hemoglobin digestion using heterologous antiserum to bovine cathepsin D

Antibody against purified bovine cathepsin D was raised in rabbits, and the polyclonal antiserum was tested to determine its ability to inhibit the hemoglobinolytic activity of the crude enzyme preparation (CEP) from adult Schistosoma japonicum and its effect upon in vitro cultured Schistosoma mansoni schistosomules. The 100,000 g supernatant fraction (CEP) from lyophilized adult worms was preincubated with antiserum and subsequently incubated with hemoglobin. Hemoglobinolytic activity was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoretic procedures. Five hours of incubation failed to diminish hemoglobin concentration in experimentals, whereas controls treated with preimmune serum displayed hemoglobin degradation. Pepstatin inhibited hemoglobin degradation. Western blot analysis of the CEP revealed a broad band of activity at approximately 45 kDa. Schistosomules incubated in vitro either in the antiserum or pepstatin and subsequently exposed to host erythrocytes showed a marked inhibition of digestive activities. Although structural changes were not evident in the gastrodermis, some perturbation of the tegument was observed. Schistosomules fed host erythrocytes and postincubated in the antiserum displayed increased tegumental perturbation and extensive alteration of the gastrodermis, including dilation of cisternae and membrane disruption. Schistosomules exposed to preimmune serum were normal in all respects.

Penetration of Schistosoma japonicum cercaria into host skin

The anterior part of Schistosoma japonicum cercaria is a specialized head organ which can slightly stretch out and retract. There are three different types of large unicellular glands in cercarial body, consisting of one head gland, 2 pairs of pre- and 3 pairs of postacetabular glands. These glands differ in position, gross feature, histochemistry and functions. Both polysaccharase and protease activities are demonstrated in the secretions from these glands. Mode of cercarial penetration is described in detail and the penetration is effected by a combination of lytic secretions and mechanical movements. The schematic representation of the process of cercarial penetration is presented. The dynamic distributions of schistosomula in skin at different time intervals after skin penetration in various mammalian hosts are shown. Some newly transformed schistosomula die while penetrating into the skin of 7 mammalian species and the mortality rate varies with the host species, and that can also be affected by the age of cercariae following emergence from the snail. Some physiological aspects between cercariae and newly transformed schistosomula are compared. In contrast to cercariae, schistosomula are saline-adapted and water-intolerant. They were modified histochemically and antigenically.

Ultrastructural observations on damage to schistosomula of Schistosoma japonicum by mouse neutrophils in vitro

Ultrastructure of schistosomula of Schistosoma japonicum was studied in relation to the effect of mouse neutrophils in vitro. In the presence of antibody and complement, damage to the schistosomular tegument covered with many neutrophils began to appear within 1 h incubation. Exfoliation of the granular cytoplasm of the tegument, disorganization of the muscle layers and vacuolation in the inner tissues were seen in a part of neutrophil-attached parasites by 2 h incubation. However, the majority of schistosomula with fewer cells retained their integrity till 16 h. The cytochemical examination of schistosomula incubated with mouse neutrophils for 1 and 2 h demonstrated clearly the localization of the peroxidase activity on the surfaces of the cells and the parasites.

Schistosoma japonicum and S. mansoni: ultrastructural damage in the tegument and reproductive organs after treatment with levo- and dextro-praziquantel

Ultrastructural observations were made of changes in the tegument and reproductive organs of Schistosoma japonicum and S. mansoni from ICR mice after treatment with praziquantel (PZQ), levo-PZQ, and dextro-PZQ at a single oral dose of 500 mg/kg body weight. No marked difference in types and extent of lesions of the tegument of S. japonicum was found between the compounds regardless of the time of worm recovery after treatment. This was equally true of S. mansoni. Degeneration of the testis, ovary, and vitelline gland of S. japonicum was more prominent in worms administered PZQ and levo-PZQ than in those receiving dextro-PZQ. In S. mansoni, extensive regression of the reproductive organs was observed in male and female worms treated with PZQ and dextro-PZQ, while no serious damage was seen in worms treated with levo-PZQ.

Scanning electron microscopic study of the tegumental surface of the hybrid schistosome between Schistosoma mekongi and S. japonicum-like (Malaysian)

Hybridization experiments between the two non-sibling species of schistosomes, Schistosoma mekongi in man and S. japonicum-like (Malaysian) in rodents, were carried out. Two laboratory-bred snail species, Tricula aperta (beta race), the snail host of S. mekongi and Robertsiella kaporensis, the snail host of S. japonicum-like (Malaysian), were used for the production of cercariae. Cross mating between S. mekongi and S. japonicum-like (Malaysian) were achieved in the laboratory by the usual procedure of exposing snails to single miracidia of each species, then exposing mice to cercariae emanating from two snails only, each infected with a different species. Hybrid eggs and miracidia were used to infect snails of both species. The resultant F1 cercariae were used to infect mice. It was shown in this study that the attempt to cross these two species of schistosomes could be achieved in the laboratory, but the results provided very low yield of hybrid worms and eggs. F1 hybrid adult worms from S. mekongi male and S. japonicum-like (Malaysian) female were obtained and examined for the microtopography of the tegument by scanning electron microscopy. The tegumental surface of the hybrid male schistosome resembled the male parent, S. mekongi, with a few characters which resembled the male, S. japonicum-like (Malaysian). The surface tegument of the hybrid male worm was characterized by the presence of highly-branched and perforated ridges interspersed with a large number of papillae all over the body surface with the heaviest concentration on the middle portion of the body. There were four types of papillae present; the pleomorphic papillae; the cratered papillae, with or without cilia; the hemispherical sensory papillae with cilia; and the fungiform papillae. Spines were absent on the body surface except in the oral and ventral suckers and in the gynecophoral canal. The tegument lining the gynecophoral canal was characterized by the presence of low ridges with scattered papillae with small number of short spines in the posterior portion of the canal. In contrast to the male, the female hybrid worm had numerous spines all over the body surface with the most concentration in the posterior region. Among the spines were low perforated ridges. Two types of papillae were present in the female hybrid; the cratered papillae, with or without cilia, and the hemispherical papillae.

Degenerative changes in the reproductive organs of female schistosomes during maintenance in vitro

Degenerative alteration of the reproductive organs of female schistosomes in correlation with the change in egg-laying rate of schistosome pairs in vitro was studied by electron microscopy. The production of normal eggs by adult S. japonicum pairs decreased after 4 days in vitro followed by an increase of abnormal egg laying up to day 8. In S. mansoni, the yield of both normal and abnormal eggs decreased gradually from the start of maintenance in vitro in spite of a much higher pairing rate than in S. japonicum. The vitelline gland of 14-day in vitro-maintained S. japonicum stained with Fast red B, while that of S. mansoni did not. The ovary of both species exhibited regressive features after 14 days of maintenance in vitro. Ultrastructural examination showed that the vitelline cells and oocytes of S. japonicum and S. mansoni had already lost their structural integrity after 2 days in vitro and continued to exhibit signs of structural degeneration throughout the 14-day in vitro maintenance period. The regressive changes in reproductive potential of female S. mansoni maintained in vitro for 4 days could be reversed by surgically implanting the parasites into mouse mesenteric veins.

Schistosoma japonicum: ultrastructural localization of a hemoglobinase using mercury labeled pepstatin

Mercury labeled pepstatin was used to demonstrate the site of a pepstatin sensitive hemoglobinase in paraformaldehyde fixed adult Schistosoma japonicum. Pepstatin was covalently attached to glutathione using dicyclohexylcarbodiimide followed by addition to methyl mercury chloride. Deposition of mercury was observed in lipid-like globules and autophagic vacuoles in the gastrodermis. Control studies were negative in all instances. These results complement previous cytochemical studies on the distribution of other acid hydrolases in the gastrodermis of schistosomes. It is hypothesized that this pepstatin sensitive enzyme probably belongs to the carboxyl class of proteinases.