Tissue reactions induced by Schistosoma mansoni in Biomphalaria glabrata

In Biomphalaria glabrata with a strong natural resistance, Schistosoma mansoni sporocysts are rapidly encapsulated by granulocytes and killed, mainly by the strong phagocytic activity of the cells. Irradiated Echinostoma paraensei sporocysts seem able to suppress the function of the granulocytes. Tissue reactions in snails with self-cure demonstrate: involvement of two types of cells, granulocytes and hyalinocyte-like cells; formation of amoeba-fibrous capsules; limited tendency of granulocytes to become attracted to the parasites; a slow process of parasite destruction; and a possible involvement of humoral factors. It seems that there is partial suppression of the granulocyte function in smails with self-cure.     

Recombinant human interleukin-1-mediated killing of Schistosoma mansoni primary sporocysts in Biomphalaria glabrata

Previous work has indicated that injection of recombinant-human interleukin (rhIL)-1beta in Schistosoma mansoni-infected M-line Biomphalaria glabrata resulted in a significant reduction in the number of cercariae shed. The purpose of the present work was to determine if primary sporocysts were killed following rhIL-1beta injection in susceptible snails and, if so, to determine if killing was the direct result of hemocyte activity. Counting of primary sporocysts indicated a 50% reduction in the number surviving at 3 days PE in snails from 2 susceptible strains following injection. Histological analysis indicated that killing occurred with little-to-no observable hemocyte/parasite contact, whereas short-term culture of primary sporocysts with cell-free plasma (hemolymph) from injected snails rapidly initiated killing in vitro. Because levels of a snail IL-1-like molecule (SnaIL-1) drop significantly following schistosome exposure in M-line snails, because resistant snails maintain higher SnaIL-1 levels following infection, and because rhIL-1beta upregulates hemocyte cytotoxic mechanisms, these data support the contention that SnaIL-1 plays a role in determining resistance in B. glabrata. These data also indicate that schistosome death may be separated from parasite encapsulation by hemocytes and that an as yet unidentified humoral killing mechanism/factor may exist in B. glabrata. Lastly, these data further support the hypothesis that cytokine-like molecules are important, functionally conserved immunodefense mediators in both vertebrates and invertebrates.     

Invasion of the Nile Valley in Egypt by a hybrid of Biomphalaria glabrata and Biomphalaria alexandrina, snail vectors of Schistosoma mansoni

Two years (1996-1997) of systematic survey showed that a hybrid of Biomphalaria glabrata and Biomphalaria alexandrina has invaded the irrigation and drainage systems in the Nile Delta and the Valley nor the of El-Menya. However, the infestation of water courses by and the population density of this snail were variable in various localities. The infestation rate ranged between 7.1% in El-Fayoum Governorate and 52.6% in El-Dakahliya Governorate and the snail density from 2 snails/site to 69.7 snails/site in the same governorates, respectively. Comparing the survey results of the two study years in the sampling sites indicated that the hybrid snail has relatively increased in population density than B. alexandrina. The hybrid snail of B. glabrata and B. alexandrina was found alone in some sites, but was mostly associated with B. alexandrina. The results showed also that both Biomphalaria have almost the same major physicochemical requirements. However, the hybrid snails and B. alexandrina were found differently associated with aquatic snails and plants. The hybrid snail was found naturally infected with S. mansoni thus giving indication that it is presently participating in schistosomiasis mansoni transmission in Egypt.     

The identification of markers segregating with resistance to Schistosoma mansoni infection in the snail Biomphalaria glabrata

Both snail and parasite genes determine the susceptibility of the snail Biomphalaria glabrata to infection with the trematode Schistosoma mansoni. To identify molecular markers associated with resistance to the parasite in the snail host, we performed genetic crosses between parasite-resistant and -susceptible isogenic snails. Because resistance to infection in adult snails is controlled by a single locus, DNA samples from individual F2 and F1 backcross progeny, segregating for either the resistant or susceptible phenotypes, were pooled (bulked segregant). Genotypes for both parents were determined with 205 arbitrary decamer primers by random amplified polymorphic DNA-PCR. Of the 205 primers, 144 were informative, and the relative allele frequencies between the pools for these primers were determined. Two primers, OPM-04 and OPZ-11, produced fragments in the resistant parent of one cross that were inherited in a dominant fashion in the resistant F2 and backcross-bulked segregant progeny. Subsequent typing of DNA samples of individual progeny snails showed that the 1.2-kb marker amplified by primer OPM-04 and the 1.0-kb marker produced by primer OPZ-11 segregated in the same dominant fashion with the resistant phenotype. Sequence analysis of the 1.2-kb marker showed that it corresponds to a repetitive sequence in the snail genome with no homology to existing DNA sequences in the public databases. Analysis of the 1. 0-kb marker showed that it also corresponds to a repetitive sequence in the B. glabrata genome that contains an imperfect ORF, with homology to retrovirus-related group-specific antigens (gag) polyprotein.     

Host choice by larval parasites: a study of Biomphalaria glabrata snails and Schistosoma mansoni miracidia related to host size

Within snail/trematode associations the age/size of the host at infection has consequences with regard to miracidial infection success, further intramolluscan parasite development and reproduction, and the host response, mainly in terms of growth and reproductive effort. Taking into account these differences, we were interested in determining whether miracidia could discriminate and make a choice between snails of different sizes. Using the Schistosoma mansoni/Biomphalaria glabrata system, we compared data on the snail infection rate and the mother sporocyst abundance among three size classes of snails (juvenile, subadult, and adult) exposed separately or together to the parasite larvae. When exposed individually, juvenile snails (3-5 mm) had significantly higher prevalence and abundance values than did subadult snails, followed by adult snails. In contrast, when snails of the three size classes were exposed together in heterogeneous size groups the prevalence and abundance values were always significantly higher for subadult snails of the 7- to 9-mm class than for juvenile and adult snails. A host choice experiment confirmed that significantly more miracidia were attracted by subadult snails, suggesting that the parasite has been selected for specific locating and recognition mechanisms increasing the infection rate of subadult snails when the latter have been exposed in a heterogeneous size group. Selective forces that may be responsible for such a preferential infectivity of the parasite vis-à-vis particular host age/size class are discussed in relation to host resources and host responses.     

Effect of Schistosoma mansoni infection on offsprings born from infected mothers

Offsprings C57BL/6 mice (4 weeks old) coming from either moderately infected (40 S. mansoni cercariae) or heavily infected (100 S. mansoni cerariae) mothers, were exposed to 40 S. mansoni cercariae each. Seven weeks post infection (P.I.), Offsprings were sacrificed. In both groups there was significant reduction in the worm load, both hepatic and intestinal tissue egg count. The oogram profile was not altered. Humoral immune response as regards the level of anti S. mansoni SEA Ab was elevated in both groups in comparison to their parallel controls at 2 weeks post delivery and 7 weeks P.I. The level of antibodies was significantly higher in heavily infected Offsprings than that present in offsprings coming from moderately infected mothers. Delayed footpad swelling and hepatic granuloma size were significantly reduced in both groups comparing with their corresponding controls.     

Studies on granuloma formation in Syrian hamsters experimentally infected with Schistosoma mansoni

Juvenile rats are more susceptible to the acute toxicity of the phosphorothionate insecticides parathion and chlorpyrifos than are adult rats. Developmental changes in brain acetylcholinesterase and hepatic aliesterase (carboxylesterase), cytochrome P450, and the P450-mediated metabolism of these two phosphorothionate insecticides were investigated in male Sprague-Dawley rats. Specific activities of acetylcholinesterase in cerebral cortex, but not medulla oblongata, and of liver aliesterases increased with age, indicating the presence of both more target esterases and more protective esterases, respectively, in the adult compared to the juvenile animal. Sensitivity of the brain acetylcholinesterase to inhibition by paraoxon and chlorpyrifosoxon, as measured by IC50 values, did not change significantly with age, whereas the hepatic aliesterase sensitivity to inhibition decreased with age. Progressive increases in activities of P450-mediated activation (desulfuration) (6- to 14-fold) and detoxication (dearylation) (2- to 4-fold), as well as concentrations of P450 (7-fold) and protein (2-fold), were observed between neonate and adult hepatic microsomes. Microsomal pentoxyresorufin O-dealkylase activity followed a developmental pattern similar to desulfuration and dearylation, displaying a 16-fold increase between neonates and adults. However, microsomal ethoxyresorufin O-deethylase activity increased until 21 days of age, displaying a 16-fold increase, then decreased in adulthood to a level 10-fold higher than neonates. These results indicate that target enzyme sensitivity is not responsible for age-related toxicity differences, nor is the potential for hepatic bioactivation, whereas lower levels of hepatic aliesterase-mediated protection and P450-mediated dearylation probably contribute significantly to the greater sensitivity of juveniles to phosphorothionate toxicity.     

Protection of mice against Schistosoma mansoni infection by passive transfer of sera from infected rabbits

Twelve patients with bilateral comparable gingival recessions were treated using a split mouth design, to compare the relative success of root coverage by two regenerative procedures. The areas of recession treated were Class I or II according to Miller's classification and caused either an esthetic problem and/or root sensitivity. The symmetrical defects, on the maxillary canines, 4 mm or deeper, were randomly assigned in each patient to surgical procedures with either a bioresorbable matrix barrier (test) or a non-resorbable expanded polytetrafluoroethylene membrane (control). Gingival recession, clinical attachment level, probing depth, and extension of keratinized tissue were measured at baseline and at 6 months postsurgically. Both procedures resulted in significant root coverage (P < 0.0001) and attachment gain (P < 0.0001). The gingival recession decreased from 4.75 +/- 0.22 mm to 0.83 +/- 0.24 mm and from 4.75 +/- 0.22 mm to 0.75 +/- 0.22 mm, corresponding to a mean root coverage of 82.4% and 83.2%, at the test and control sites respectively. The average clinical attachment gain was 4.33 +/- 0.44 mm at the test sites compared to 4.42 +/- 0.48 mm for the non-resorbable barrier. No significant changes were found for probing depth and keratinized tissue. Data analysis did not demonstrate any significant difference between the two procedures for any of the variables included. However, a questionnaire given to each patient revealed the single-step surgery to be the patients' choice.     

Immunological response of major histocompatibility complex class II-deficient (Abeta(o)) mice infected by the parasite Schistosoma mansoni

This study investigated changes in autonomic nervous activities due to psychological stress in Type A females. Eight Type A and eight Type B females performed a psychomotor task for 30 minutes. Power spectral analysis of heart rate variability (HRV) was used to examine the autonomic nervous activities. Results showed the low frequency (LF) component and LF/HF ratio in Type A females increased after the onset of the task. There were no significant differences in task performance between Type A and Type B females. The subjective mental workload increased gradually in Type A females during the tasks, whereas in Type B females this parameter did not change in a consistent manner. The results suggest that the sympathetic nervous system in Type A females was more stimulated by the task and Type A females felt a greater subjective mental workload than did Type B females.     

Rapid detection of a Schistosoma mansoni circulating antigen excreted in urine of infected individuals by using a monoclonal antibody

Schistosoma circulating antigens were used to indicate the infection intensity and to assess cure. An immunoglobulin G2a (IgG2a) mouse monoclonal antibody was used in a fast dot-enzyme-linked immunosorbent assay (ELISA; FDA) for rapid and simple diagnosis of schistosomiasis in the field. Seven hundred Egyptians were parasitologically examined for Schistosoma mansoni and other parasitic infections. A rectal biopsy was done as a "gold standard" for individuals showing no S. mansoni eggs in their feces. Egg counts were obtained by the Kato smear method for only 100 of 152 individuals with eggs in their feces. Specific anti-schistosome IgG antibodies were evaluated in sera by ELISA. Urine samples from the 700 individuals were tested by FDA for detection of the circulating antigen. The assay showed a sensitivity of 93% among 433 infected individuals and a specificity of 89% among 267 noninfected individuals. FDA showed the highest efficiency of antigen detection (91%) compared with the efficiency of antibody detection by ELISA (75%) and stool analysis (60%). In addition, FDA detected infected patients with 20 eggs/g of feces. Also, the sensitivity of FDA ranged from 90 to 94% among samples from patients with different clinical stages of schistosomiasis. All the assay steps can be completed within 30 min at room temperature for 96 urine samples. The monoclonal antibody identified a 74-kDa antigen in different antigenic extracts of S. mansoni and Schistosoma haematobium and in the urine of infected individuals. In addition, a 30-kDa degradation product was identified only in the urine samples. On the basis of these results, FDA should be used as a rapid tool for the sensitive and specific diagnosis of Schistosoma infection.     

A light and electron microscope study on oogenesis in the freshwater pulmonate snail Biomphalaria glabrata

In the freshwater snail Biomphalaria glabrata the formation and composition of yolk granules and the role of the follicle cells were studied by histochemical and electron microscopical techniques. The rough endoplasmic reticulum and the Golgi apparatus appeared to be involved in yolk formation, which is a continuous process throughout oogenesis. From the very beginning of yolk formation two main types of yolk granules were distinguished morphologically. However, with histochemical and enzyme cytochemical methods no differences were observed between these types. The granules acquire lysosomal enzymes after oviposition, indicating that their main function is probably digestion of perivitelline fluid, which contains nutrients for the developing embryo. Yolk formation and the activity of the follicle cells were studied in successive stages of oogenesis by quantitative electron microscopy. The data strongly suggest that the follicle cells are involved in the formation of the follicular cavity and hence in the ovulation process.     

Effect of praziquantel on the free living stages of Schistosoma mansoni

The effect of the new schistosomicide praziquantel (2-cyclohexyl-carbonyl-1,2,3,6,7,11 b-hexahydro-2H-pyrazino[2,1a]isoquinolin-4-one) on the miracidia and cercariae of Schistosoma mansoni was investigated. In vivo praziquantel inhibits hatching of miracidia for 24 h after administration of 500 mg/kg to infected mice. In vitro a concentration of 10 microgram/ml inhibits subsequent hatching in drug-free water. Free swimming miracidia are rapidly killed by 1 microgram/ml. Even 0.01 microgram/ml is still partially effective. In a solution of 0.03 microgram/ml cercariae lose their ability to swim within 10 min. This effect is reversible in drug-free water. Morphological damage to cercariae incubated in 0.1 microgram/ml is clearly evident. However, cercariae are fully infective when given subcutaneously to mice after a 3-h incubation period. Incubation in 1 microgram/ml reduces the infection rate by 80%. A 2-h incubation in 0.1 microgram/ml almost completely inhibits the percutaneous infection through the abdominal skin. The number of cercariae that develop to schistosomules is reduced by more than 90%. After a 2-h incubation in a concentration of 0.01 microgram/ml the swimming ability of cercariae is impaired in such a way that the number of cercariae penetrating in the tail immersion test and developing to schistosomules is reduced by half. Praziquantel is a more potent protective agent than the molluscicides copper sulphate, sodium pentachlorophenate and Bayluscide or cadmium and zinc ions.     

The histopathological picture of the liver of hamsters experimentally infected with Leishmania D. infantum on top of Schistosoma mansoni infection

No doubt, double and triple infection in a patient is not an uncommon phenomenon in the Old World. Consequently, the histopathological picture of the liver of Syrian golden hamsters experimentally infected with Leishmania. d. infantum on top of pre-infection with S. mansoni was studied. The results showed that the liver was markedly affected by the concomitant infection than infection with either parasite alone. The superadded Leishmania infection caused the early appearance of cell necrosis and fatty changes. The schistosomal granulomas were rounded in shape and well circumscribed. However, they were smaller in size and less in number when compared with schistosomal control. Also, there was a comparative decrease in the number of their cellular constitutions but without changing in the cell types. The schistosomal granulomas were surrounded with a rim of amastigotes laden macrophages. On the other hand, the leishmanial granulomas, were irregular in shape but comparatively increased in size and in number on the behalf of the schistosomal granulomas. Their cellular constitutions comparatively increased as well. So, it is concluded that the L.d. infantum infection on the top of S. mansoni infection suppressed the schistosomal pathological picture in the liver of hamsters.     

Modification of the lung recovery assay for schistosomula and correlations with worm burdens in mice infected with Schistosoma mansoni

The kinetics of recovery of schistosomula from the lungs of previously-unexposed CF1 mice were studied following infection with Schistosoma mansoni cercariae. Lung tissue fragments were incubated from 3 to 48 hr and the completeness of recovery of viable schistosomula was determined. The recovery of schistosomula from the lungs was shown to correlate closely with 7-week worm recoveries. With the additional incubation described, the lung recovery assay may provide a more defined indicator of protective immunity. Based on the data generated by these analyses, it is predicted that under these conditions schistosomula arrive in the lungs from 3 to 7 days after infection, and that they sojourn there for a 3-day period.     

Evidence for adsorption of heterospecific host immunoglobulin on the tegument of Schistosoma mansoni

Mice infected with Schistosoma mansoni were immunized against human type B Rh-positive (B+) RBC, bovine serum albumin, or horseradish peroxidase. Adult parasites, recovered by perfusion, extensively washed, and incubated in their respective antigens, selectively bound to their tegumental surfaces only those antigens to which their murine host had been immunized. All controls supported the specificity of those reactions leading to the conclusion that adult S. mansoni in mice have the ability to adsorb heterospecific antibody onto their tegumental surfaces. These surface immunoglobulins were lost within 10 min when complexed with theri antigens or within 2.5 hr when incubated at 37 degrees C. Parasites that had lost their tegumental immunoglobulins regained them when incubated in normal mouse or rat anti-human type B Rh-negative (B-) RBC serum. Those parasites that had their surface immunoglobulins reconstituted with rat anti-human B- serum specifically bound human B- RBC, suggesting the possible presence of Fc receptors on adult S. mansoni.     

Biodistribution study of the anaesthetic sodium phenobarbital labelled with technetium-99m in Swiss mice infected with Schistosoma mansoni Sambon, 1907

The surgical treatment of transsphenoidal cephaloceles in children is controversial. Reduction and repair via a transcranial approach are associated with high postoperative rates of morbidity, mortality, and hypothalamic dysfunction. In this study, four patients, aged 3 to 35 months at surgery, underwent successful transpalatal repair of two encephaloceles and two meningoceles. Two patients presented with nasal obstruction in infancy, one presented with unexplained meningitis, and in one patient the lesion was found incidentally during evaluation for seizures. Two children had median cleft face syndrome, another had an associated Arnold-Chiari type I malformation, and the fourth had no other cranial abnormalities. All patients underwent preoperative evaluation including magnetic resonance (MR) imaging. Auditory, ophthalmological, genetic, endocrinological, or other evaluation was undertaken as indicated. Lesions were approached through the median raphe of the hard and soft palates. All cephaloceles were easily visualized and dissected after division of the nasal palatal mucosa. The dural sac and its contents were reduced by surface coagulation after division and dissection of the overlying mucosa. Once reduced, the bone defect was obliterated in three of four patients. The dura was not opened and anomalous neural elements were not resected. At follow-up evaluation, all patients demonstrated resolution of preoperative symptoms without evidence of infection or lasting morbidity. Follow-up MR imaging showed reduction in all cases. The authors conclude that this transpalatal approach is safe and reliable for the treatment of transsphenoidal cephaloceles in young children.     

Localization by immunoelectron microscopy of Schistosoma mansoni antigens in the glomerulus of the hamster (Mesocricetus auratus) kidney

Gene therapy has the potential to provide cancer treatments based on novel mechanisms of action with potentially low toxicities. This therapy may provide more effective control of loco-regional recurrence in diseases such as non-small cell lung cancer (NSCLC), as well as systemic control of micrometastases. Despite current limitations, retroviral and adenoviral vectors can in certain circumstances provide an effective means of delivering therapeutic genes to tumour cells. Although multiple genes are involved in the process of carcinogenesis, mutations of the p53 gene are the most frequent abnormality identified in human tumours. Pre-clinical studies both in vitro and in vivo have shown that restoration of p53 function can induce apoptosis in cancer cells. Phase I clinical trials now show that p53 gene replacement therapy is feasible and safe using both retroviral and adenoviral vectors, and that it induces tumour regression in patients with advanced NSCLC and recurrent head and neck cancer. Other pre-clinical studies indicate that gene therapy may have useful synergy with cytotoxic and radiation therapy. This paper describes the different gene therapy strategies under investigation and the pre-clinical data that provides a rationale for the gene replacement approach, reviews clinical trial data and presents novel ideas for improving current vectors and gene delivery to tumours.