Schistosoma japonicum: the pathology of experimental infection

A chromosome-level genome of the human blood fluke Schistosoma japonicum identifies the genomic basis of host-switching

The evolution and adaptation of S. japonicum, a zoonotic parasite that causes human schistosomiasis, remain unclear because of the lack of whole-genome data. We construct a chromosome-level S. japonicum genome and analyze it together with 72 samples representing six populations of the entire endemic region. We observe a Taiwan zoophilic lineage splitting from zoonotic populations ∼45,000 years ago, consistent with the divergent history of their intermediate hosts. Interestingly, we detect a severe population bottleneck in S. japonicum, largely coinciding with human history in Asia during the last glacial maximum. We identify several genomic regions underlying natural selection, including GATAD2A and Lmln, both showing remarkable differentiation among different areas. RNAi knockdown suggests association of GATAD2A with parasite development and infection in definitive hosts, while Lmln relates to the specificity of the intermediate hosts. Our study provides insights into the evolution of S. japonicum and serves as a resource for further studies.

Efficacy, metabolism and pharmacokinetics of Ro 15-5458, a forgotten schistosomicidal 9-acridanone hydrazone

BACKGROUND

Treatment of schistosomiasis, a neglected disease, relies on just one partially effective drug, praziquantel. We revisited the 9-acridanone hydrazone, Ro 15-5458, a largely forgotten antischistosomal lead compound.

METHODS

Ro 15-5458 was evaluated in juvenile and adult Schistosoma mansoni-infected mice. We studied dose-response, hepatic shift and stage specificity. The metabolic stability of Ro 15-5458 was measured in the presence of human and mouse liver microsomes, and human hepatocytes; the latter also served to identify metabolites. Pharmacokinetic parameters were measured in naive mice. The efficacy of Ro 15-5458 was also assessed in S. haematobium-infected hamsters and S. japonicum-infected mice.

RESULTS

Ro 15-5458 had single-dose ED50 values of 15 and 5.3 mg/kg in mice harbouring juvenile and adult S. mansoni infections, respectively. An ED50 value of 17 mg/kg was measured in S. haematobium-infected hamsters; however, the compound was inactive at up to 100 mg/kg in S. japonicum-infected mice. The drug-induced hepatic shift occurred between 48 and 66 h post treatment. A single oral dose of 50 mg/kg of Ro 15-5458 had high activity against all tested S. mansoni stages (1-, 7-, 14-, 21- and 49-day-old). In vitro, human hepatocytes produced N-desethyl and glucuronide metabolites; otherwise Ro 15-5458 was metabolically stable in the presence of microsomes or whole hepatocytes. The maximum plasma concentration was approximately 8.13 μg/mL 3 h after a 50 mg/kg oral dose and the half-life was approximately 4.9 h.

CONCLUSIONS

Ro 15-5458 has high activity against S. mansoni and S. haematobium, yet lacks activity against S. japonicum, which is striking. This will require further investigation, as a broad-spectrum antischistosomal drug is desirable.

Granuloma formation and tissue pathology in Schistosoma japonicum versus Schistosoma mansoni infections

Schistosomiasis is the most important helminth disease in the world from a public health perspective. S mansoni and S japonicum account for the majority of global intestinal schistosomiasis cases, and the pathogenesis is widely assumed to be fundamentally similar. However, the majority of research on schistosomiasis has been carried out on S mansoni and comparisons between the two species are rarely made. Here, we will discuss aspects of both older and recent literature where such comparisons have been made, with a particular focus on the pathological agent, the host granulomatous response to the egg. Major differences between the two species are apparent in features such as egg production patterns and cellular infiltration; however, it is also clear that even subtle differences in the cascade of various cytokines and chemokines contribute to the different levels of pathology observed between these two main species of intestinal schistosomiasis. A better understanding of such differences at species level will be vital when it comes to the development of new treatment strategies and vaccines.

Negative Association of Interleukin-33 Plasma Levels and Schistosomiasis Infection in a Site of Polyparasitism in Rural Cameroon

Background: This study aimed to investigate the association of plasma levels of IL-33, a mucosal alarmin known to elicit type-2 immunity, with infection and liver fibrosis profiles of school children from an endemic area for Schistosoma mansoni, malaria and hepatitis (B & C) in rural Cameroon.

Methods: A cross-sectional study enrolling schoolchildren from 5 public schools was conducted. Single schistosomiasis, malaria and hepatitis infections or co-infections were assessed by kato katz, microscopy, and rapid diagnostic tests, respectively. Hepatic fibrosis was assessed by ultrasound according to WHO Niamey guidelines and plasma levels of Interleukin 33 were determined by ELISA. All statistics were performed using R studio software.

Principal findings: We found a prevalence of 13.5% (37/275), 18.2% (50/275), and 8% (22/275), respectively for schistosomiasis, malaria and hepatitis (B or C) single infections. Only 7.6% (21/275) of co-infections were reported. Although Plasma IL-33 showed a minimal negative risk for schistosomiasis infection (AOR 0.99; 95% CI 0.97–1.01), S. mansoni infected participants had lower levels of plasma IL-33 (p = 0.003) which decreased significantly as eggs burdens increased (p = 0.01) with a negative Pearson coefficient of r = −0.22. Hepatic fibrosis occurred in 47.3% (130/275) of our study population independently from plasma levels of IL-33 (AOR 1.00; 95% CI 0.99–1.01).

Conclusion/Significance: Our data failed to show an association between plasma IL-33 levels and liver disease but convincingly report on a negative association between plasma IL-33 levels and schistosomiasis infection and egg burden in school children from a polyparasitic schistosomiasis endemic area.

Expression of heat shock protein 47, transforming growth factor-beta 1, and connective tissue growth factor in liver tissue of patients with Schistosoma japonicum-induced hepatic fibrosis

SUMMARY To detect the expression of pro-fibrotic molecules, such as heat shock protein 47 (Hsp47), transforming growth factor-beta 1 (TGF-β1) and connective tissue growth factor (CTGF) in liver specimens, and analyse their correlations with the progression of schistosomal hepatic fibrosis, liver biopsy was performed in 42 chronic schistosomiasis (CS) patients, 16 chronic hepatitis B (CHB) patients and five healthy individuals (HI). Immunohistochemistry (IHC) analyses displayed that the expression of Hsp47, TGF-β1 and CTGF was increased in CS and CHB patients compared with HI. Using real-time PCR, the mRNA levels of Hsp47, TGF-β1 and CTGF were higher in CS patients compared with HI. In CS patients, the mRNA levels of these genes were correlated with the stage of fibrosis, and TGF-β1 mRNA expression was associated with the grade of inflammation. Additional analyses indicated that the mRNA levels of Hsp47 and CTGF were highly correlated with liver stiffness value and spleen thickness diameter, both of which represented the severity of fibrosis. In conclusion, the three molecules are involved in the pathogenesis of hepatic fibrosis infected by Schistosoma japonicum. TGF-β1 participates not only in the inflammatory process, but also in the fibrotic process in which Hsp47 and CTGF probably play a key role.

Effect of praziquantel prolonged administration on granuloma formation around Schistosoma japonicum eggs in lung of sensitized mice

Schistosomiasis remains a major public health problem and it is an immune disease. The schistosome egg is the primary parasite factor responsible for the overt disease. The eggs release the soluble antigen, which induces intensive tissue reaction, a granulomatous reaction to the eggs. If granuloma formation could be suppressed, overt disease might not develop. Praziquantel is an effective antischistosomal drug especially for adult worms. However, whether praziquantel has a suppressing effect on granuloma formation around schistosome eggs directly remains unclear. The purpose of the present study was to investigate the effect of praziquantel, especially administered persistently, on granuloma formation around Schistosoma japonicum eggs in the lung of sensitized mice. Thirty-six mice were divided into three groups averagely. Group A was a control group. First, the mice were injected with schistosomal eggs hypodermically in abdomen, and 10 days later injected with schistosomal eggs intravenously via a tail vein. Group B was a praziquantel short administration group. In addition to the injections of schistosomal eggs as the same of Group A, the mice were administered with praziquantel in a daily dose of 300 mg/kg for 3 days, from 1 day before the intravenous injection of the eggs. Group C was a praziquantel prolonged administration group. In addition to the injections of schistosomal eggs as the same of Group A, the mice were administered with praziquantel in a daily dose of 150 mg/kg for 5 days weekly until the mice were sacrificed. Three mice of each group were sacrificed on days 7, 14, 28, and 56, respectively after the intravenous injection of the eggs, and the lung tissues were fixed with formalin and the slices were HE stained. The granulomas containing eggs in their centers were selected, and 25-30 granulomas from the animals of each group were measured at each time period. The mean areas of egg granulomas of each group were calculated, and the neutrophilic granulocytes, eosinocytes, lymphocytes, fibroblasts, and macrophages within the egg granulomas were counted. The mean numbers of them of each group were calculated. All the data of each group were analyzed and compared statistically. On day 56 after the intravenous injection of the eggs, the mean area of schistosomal egg granulomas in group B was (227.4 ± 728.0) × 10(3) μm(2), less than that of [(297.9 ± 153.3) × 10(3) μm(2)] in group A, and the suppression rate was 23.7% (P < 0.05). On days 7, 14, 28, and 56, the mean areas of schistosomal egg granulomas in group C were (575.8 ± 155.6) × 10(3) μm(2), (310.5 ± 854.0) × 10(3) μm(2), (267.7 ± 513.3) × 10(3) μm(2), and (214.9 ± 446.4) × 10(3) μm(2), respectively, significantly less than those of [(692.7 ± 232.6) × 10(3) μm(2), (439.4 ± 165.0) × 10(3) μm(2), (385.7 ± 129.3) × 10(3) μm(2), and (297.9 ± 153.3) × 10(3) μm(2)] in group A. The suppression rates were 16.9%, 29.3%, 30.6%, and 27.9%, respectively (P values <0.05). On day 56, the mean numbers of neutrophilic granulocytes were 11.4 ± 5.0 in group A and 5.2 ± 3.1 in group C, respectively, with the suppression rate of 54.4% in group C (P < 0.05). On day 56, the mean numbers of eosinocytes within the egg granulomas were 2.3 ± 2.0, 0.1 ± 0.3, and 0.3 ± 0.6 in groups A, B, and C, respectively, with the suppression rate of 95.7% in group B and 87.0% in group C (P values <0.05). On day 56, the mean numbers of macrophages within egg granulomas were 14.3 ± 6.9 in group C, compared with 18.6 ± 8.2 in group A, the suppression rate was 23.1% (P < 0.05). On day 56, the mean numbers of fibroblasts within the egg granulomas were 6.6 ± 4.4 and 5.8 ± 2.6 in groups B and C, respectively, and compared with 14.3 ± 7.8 in group A, the increasing extents decreased by 53.8% and 59.4%, respectively (P values <0.05). Therefore, the administration of praziquantel, especially the prolonged administration, can suppress the formation of schistosomal egg granulomas, including reduction in the areas of granulomas and suppression of the inflammatory cells and the hyperplasia of fibroblasts within granulomas.

Differential expression of chemokine and matrix re-modelling genes is associated with contrasting schistosome-induced hepatopathology in murine models

The pathological outcomes of schistosomiasis are largely dependent on the molecular and cellular mechanisms of the host immune response. In this study, we investigated the contribution of variations in host gene expression to the contrasting hepatic pathology observed between two inbred mouse strains following Schistosoma japonicum infection. Whole genome microarray analysis was employed in conjunction with histological and immunohistochemical analysis to define and compare the hepatic gene expression profiles and cellular composition associated with the hepatopathology observed in S. japonicum-infected BALB/c and CBA mice. We show that the transcriptional profiles differ significantly between the two mouse strains with high statistical confidence. We identified specific genes correlating with the more severe pathology associated with CBA mice, as well as genes which may confer the milder degree of pathology associated with BALB/c mice. In BALB/c mice, neutrophil genes exhibited striking increases in expression, which coincided with the significantly greater accumulation of neutrophils at granulomatous regions seen in histological sections of hepatic tissue. In contrast, up-regulated expression of the eosinophil chemokine CCL24 in CBA mice paralleled the cellular influx of eosinophils to the hepatic granulomas. Additionally, there was greater down-regulation of genes involved in metabolic processes in CBA mice, reflecting the more pronounced hepatic damage in these mice. Profibrotic genes showed similar levels of expression in both mouse strains, as did genes associated with Th1 and Th2 responses. However, imbalances in expression of matrix metalloproteinases (e.g. MMP12, MMP13) and tissue inhibitors of metalloproteinases (TIMP1) may contribute to the contrasting pathology observed in the two strains. Overall, these results provide a more complete picture of the molecular and cellular mechanisms which govern the pathological outcome of hepatic schistosomiasis. This improved understanding of the immunopathogenesis in the murine model schistosomiasis provides the basis for a better appreciation of the complexities associated with chronic human schistosomiasis.

Schistosomiasis is a significant cause of morbidity and mortality in the tropical world although its true burden has been historically underestimated. Millions of people currently endure severe pathology as a result of schistosome infections, although some individuals appear to be less susceptible to infection despite constant parasite exposure. A similar range of disease susceptibility is evident in different strains of inbred mice infected with schistosomes, thereby mirroring the clinical situation. Granuloma formation in the liver of both humans and mice is a characteristic manifestation of chronic schistosomiasis, and is largely controlled by gene signalling pathways. Certain genes expressed in particular cohorts of mice and humans may be associated with the development of severe pathology, or may confer a protective phenotype. This murine study highlights some key molecular aspects of chronic schistosomiasis which may be responsible for the development of both mild and severe pathology, and provides a bench mark for studying the mechanisms of schistosome-induced disease in humans.

Severe hepatosplenic schistosomiasis: clinicopathologic study of 102 cases undergoing splenectomy

We present the preoperative findings of 102 patients who underwent successful splenectomy for advanced schistosomiasis japonica. All patients were symptomatic for schistosomiasis and had splenomegaly greater than or equal to II according to the Hackett criteria. Before surgery, all patients underwent clinical examination including full blood count; fibrinogen and serum protein levels; liver function tests; and serology for hepatitis B, C, and D. Ultrasound examination of the liver and spleen and liver histology for evidence of pathology were also undertaken. Ninety patients had a treatment history for schistosomiasis. Fifty-six patients were seropositive for hepatitis B virus antibody, and 6 patients were seropositive for hepatitis C virus antibody. Immunohistochemical testing of the liver samples confirmed that 45 patients were positive for hepatitis B virus surface antigen, thereby indicating active infection. A total of 66.7% of patients had fibrosis stages II to III by ultrasound; and 76.5% of patients had portal vein inner diameter greater than 12 mm, indicating portal vein hypertension. A total of 83.2% of patients showed various stages of esophageal varicosis via x-ray, and 81.4% had fibrotic stages III to IV by liver biopsy. Coinfection with hepatitis B virus accelerated the development of liver fibrosis. There was moderate concordance between the fibrosis assessed by ultrasonography and histopathology, indicating that ultrasound underestimates the true pathology. Combined assessment is needed to improve the diagnosis of clinical hepatic fibrosis.

Co-ordinated gene expression in the liver and spleen during Schistosoma japonicum infection regulates cell migration

Determining the molecular events induced in the spleen during schistosome infection is an essential step in better understanding the immunopathogenesis of schistosomiasis and the mechanisms by which schistosomes modulate the host immune response. The present study defines the transcriptional and cellular events occurring in the murine spleen during the progression of Schistosoma japonicum infection. Additionally, we compared and contrasted these results with those we have previously reported for the liver. Microarray analysis combined with flow cytometry and histochemistry demonstrated that transcriptional changes occurring in the spleen were closely related to changes in cellular composition. Additionally, the presence of alternatively activated macrophages, as indicated by up-regulation of Chi3l3 and Chi3l4 and expansion of F4/80⁺ macrophages, together with enhanced expression of the immunoregulatory genes ANXA1 and CAMP suggests the spleen may be an important site for the control of S. japonicum-induced immune responses. The most striking difference between the transcriptional profiles of the infected liver and spleen was the contrasting expression of chemokines and cell adhesion molecules. Lymphocyte chemokines, including the homeostatic chemokines CXCL13, CCL19 and CCL21, were significantly down-regulated in the spleen but up-regulated in the liver. Eosinophil (CCL11, CCL24), neutrophil (CXCL1) and monocyte (CXCL14, CCL12) chemokines and the cell adhesion molecules VCAM1, NCAM1, PECAM1 were up-regulated in the liver but unchanged in the spleen. Chemokines up-regulated in both organs were expressed at significantly higher levels in the liver. Co-ordinated expression of these genes probably contributes to the development of a chemotactic signalling gradient that promotes recruitment of effector cells to the liver, thereby facilitating the development of hepatic granulomas and fibrosis. Together these data provide, for the first time, a comprehensive overview of the molecular events occurring in the spleen during schistosomiasis and will substantially further our understanding of the local and systemic mechanisms driving the immunopathogenesis of this disease.

Schistosomiasis is a significant cause of illness and death in the developing world. Inflammation and scarring in the liver and enlargement of the spleen (splenomegaly) are common features of the disease. Changes occurring in the spleen have the potential to influence the way in which the body deals with infection but the mechanisms driving these changes are not well characterised. In the present study we determined, for the first time, the gene expression profile of the mouse spleen during infection with Schistosoma japonicum and compared these results to those previously reported for the liver to determine if processes occurring in these organs co-operate to promote hepatic inflammation and granuloma formation. Our data indicated that gene expression in the spleen is related to the types of cells present and suggest that the spleen might be important in controlling schistosome-induced inflammation. Comparison of the liver and spleen showed that expression of cell signalling molecules (chemokines) was much higher in the liver, potentially promoting the recruitment of specific cell types to this organ, causing inflammation and scarring. The results from this study enhance our knowledge of the mechanisms that drive schistosome-induced splenomegaly and liver inflammation.

Renal injury due to hepatic hydatid disease

BACKGROUND

Many studies on renal hydatid disease have been reported in the literature, and the disease process appears to be well defined. However, renal injury without direct renal invasion remains poorly understood. The present study aims to define the frequency and the property of the renal involvement in hydatid disease.

METHODS

Eighty patients older than 18 years and diagnosed with liver echinococcosis were included in the study. The echinococcosis was diagnosed by the haemagglutination test and abdominal ultrasonography. Twenty-four-hour protein excretion was measured for patients who had elevated serum creatinine levels or whose urinalyses were positive for haematuria or proteinuria. Subsequently, renal biopsy was performed, and the specimens were examined by light microscopy and immunofluorescence staining.

RESULTS

Haematuria was detected in 11 patients (13.75%), and proteinuria was detected in nine patients (11.25%). Percutaneous renal biopsy was applied to nine patients who gave signed consents to undergo the test. We detected four immunoglobulin A nephritis (together with tubulointerstitial nephritis in one patient), one membranoproliferative glomerulonephritis, one immunoglobulin M nephritis together with mesangiocapillary glomerulonephritis, one membranous glomerulonephritis, one amyloidosis and one tubulointerstitial nephritis. Renal hydatid cyst was detected only in four patients (5%).

CONCLUSIONS

Hydatid disease, which affects the kidney, is not rare, and we suggest that urinalysis and, if indicated, renal biopsy should be performed for hepatic hydatid disease diagnosis.

Detection of circulating antigen in serum of mice infected with Schistosoma japonicum by immunomagnetic bead ELISA based on IgY

We developed a novel immunomagnetic bead ELISA based on IgY (egg yolk immunoglobulin) for detection of circulating antigen (CA) in sera of mice infected with Schistosoma japonicum. The assay involved the use of chicken polyclonal antibodies IgY against soluble egg antigens (SEA) of S. japonicum as a capture antibody and anti-SEA mouse monoclonal antibody NP28-5B labeled horseradish peroxidase (HRP) as a detecting antibody. Two groups of BALB/c mice infected with S. japonicum cercariae were used: lightly infected mice (infected with 10 S. japonicum cercariae) and heavily infected mice (infected with 30 S. japonicum cercariae). The CA was detectable as early as 4 and 5 weeks after infection in the sera of heavily and lightly infected mice, respectively. The CA levels rose rapidly and reached a peak in 8 weeks after infection and then remained a plateau for at least another 6 weeks in both groups. Moreover, the effect of praziquantel on the CA levels was also investigated. The heavily infected mice were treated with praziquantel and the CA levels in sera increased dramatically in the first week post-treatment and then decreased to the control level by 6 weeks after treatment. The novel assay appears to be sensitive for detection of schistosomal antigenemia and valuable to judge the efficacy of chemotherapy in murine schistosomiasis.

Immunomodulation of the hepatic egg granuloma in Schistosoma japonicum-infected pigs

Immunomodulation of perioval granulomas is a well-known phenomenon in schistosome-infected mice, but only little is known about granuloma modulation in other animal models of human schistosomiasis. In the present study, we explored immunomodulation of egg granulomas in the liver in a pig model of schistosomiasis japonica. Granuloma size was measured and T cells, B cells and IgG(+) plasma cells in granulomas were quantified in pigs at 9, 12 and 21 weeks post infection (wpi) with Schistosoma japonicum. Granulomas were largest at 9 wpi, had decreased significantly in size at 12 wpi and remained small at 21 wpi (9 vs. 12 and 21 wpi: P < 0.05). The size of granulomas containing mature and immature eggs, respectively, did not differ significantly. The density of T (CD3epsilon(+)) cells and IgG(+) plasma cells in granulomas was the same, irrespective of granuloma size and time points. B (CD79alpha(+)) cells were rare in granulomas. The results indicate that in pigs, S. japonicum egg granulomas in the liver are immunomodulated at an early stage of infection, and that not only mature but also immature eggs induce a marked granulomatous reaction in this species.

Vanin-1(-/-) mice show decreased NSAID- and Schistosoma-induced intestinal inflammation associated with higher glutathione stores

Vanin-1 is a membrane-anchored pantetheinase highly expressed in the gut and liver. It hydrolyzes pantetheine to pantothenic acid (vitamin B5) and the low-molecular-weight thiol cysteamine. The latter is believed to be a key regulating factor of several essential metabolic pathways, acting through sulfhydryl-disulfide exchange reactions between sulfhydryl groups of the enzymes and the oxidized form, cystamine. Its physiological importance remains to be elucidated, however. To explore this point, we developed Vanin-1-deficient mice that lack free cysteamine. We examined the susceptibility of deficient mice to intestinal inflammation, either acute (NSAID administration) or chronic (Schistosoma infection). We found that Vanin-1(-/-) mice better controlled inflammatory reaction and intestinal injury in both experiments. This protection was associated with increased gamma-glutamylcysteine synthetase activity and increased stores of reduced glutathione, as well as reduced inflammatory cell activation in inflamed tissues. Oral administration of cystamine reversed all aspects of the deficient phenotype. These findings suggest that one cysteamine function is to upregulate inflammation. Consequently, the pantetheinase activity of Vanin-1 molecule could be a target for a new anti-inflammatory strategy.

Neuronal nitric oxide synthase activity is increased during granulomatous inflammation in the colon and caecum of pigs infected with Schistosoma japonicum

Neuronal nitric oxide is a non-adrenergic non-cholinergic neurotransmitter in the enteric nervous system and plays a role in a variety of enteropathies including Crohn's and Chagas' diseases, ulcerative colitis, diabetes, atrophy and hypertrophy. The content of neuronal nitric oxide synthase (nNOS) in the colon and the caecum from pigs infected with Schistosoma japonicum was studied using immunohistochemical and histochemical staining for nNOS and nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-diaphorase), respectively. In the infected pigs, lightly, moderately and less severely inflamed tissues showed increased nNOS and NADPH-diaphorase activities in nerve cell bodies and nerve fibres in the enteric plexuses compared to control pigs. There was a significant increase in the nerve cell body density of nNOS immunoreactive nerve cell bodies in the inner submucous plexus, outer submucous plexus and in the myenteric plexus. More intensely stained nerve cell bodies and varicosities were observed in tissue from prenatally infected and prenatally infected, postnatally re-infected pigs compared to postnatally infected pigs. However, the latter showed the highest numerical density of nNOS immunoreactive nerve cell bodies. Marked increases were seen in the inner submucous plexus followed by myenteric plexus, inner circular muscle, outer submucous plexus and mucous plexus. However, in very severe inflamed tissues, the number and staining intensity of nerve cell bodies and nerve fibre varicosities were reduced in plexuses located in the lesions with the inner submucous and mucous plexuses being the most affected. There was no staining in the nervous tissue within the eosinophilic cell abscesses and productive granulomas. The apparent alterations in the activities of enzymes responsible for the generation of nitric oxide (NO) show possible alterations in the NO mediated non-adrenergic non-cholinergic reflexes in the enteric nervous tissue. These alterations might contribute to impaired intestinal motility and absorption, and other pathophysiological conditions seen during S. japonicum infections.

Schistosoma japonicum infection in the pig as a model for human schistosomiasis japonica

Valuable information on human schistosomiasis japonica has been provided using primates and experimental rodent hosts. However, major drawbacks such as high costs and ethical concerns for the primate models and large biological deviations for the rodent models have led to the search for more appropriate models. Recent data on the pig indicate that this natural host for Schistosoma japonicum might be a realistic alternative. As only very few research groups have investigated the S. japonicum/pig model, the present review mainly deals with the experimental methods and the major host/parasite findings obtained from the authors own research group. With emphasis on a critical evaluation of the work, the results are compared to the scarce information existing on human schistosomiasis japonica. Like in humans, S. japonicum establishes mainly in the large intestinal veins, with high faecal egg counts during the acute phase of infection, which varies greatly within and between days. Concomitant resistance is another shared feature, but studies in pigs have indicated that the phenomenon is more complex than generally thought. Clinical signs as eosinophilia and diarrhoea with mucus and blood in the acute phase of infection and hepatomegaly, increased portal diameter, periportal fibrosis and ascites in chronic infections are common findings in both humans and pigs. Low protein diet aggravates the disease in pigs by increasing the establishment rates, the faecal egg excretion and the morbidity. A 100% cure rate is achieved when treating S. japonicum infected pigs with praziquantel at 40 mg/kg, and 4 weeks post treatment pigs remain resistant to reinfection. Lastly, human congenital S. japonicum infection has been confirmed in pigs but the implications of such infections for the pathogenesis of schistosomiasis japonica remain to be investigated.

The baboon as a non-human primate model of human schistosome infection

Over the past three decades, intensive studies of murine schistosomiasis have provided important clues to the understanding of the human disease, but growing evidence suggests that these results derived from highly inbred strains of mice might not have direct applicability to the human infection. Recent data based on the baboon indicate that infection in this non-human primate might mirror the human situation. In this review, Mramba Nyindo and Idle Farah demonstrate that baboons provide an excellent non-human primate model that produces pathology and disease closely resembling that observed in humans, and address how studies in baboons can provide insights into mechanisms regulating schistosomiasis mansoni pathology and immunity. They also address, in a general way, issues related to the use of non-human primates in biomedical research.

In vivo and in vitro cellular response to Schistosoma japonicum eggs in hosts with differing susceptibilities

A comparative study of the cellular response to Schistosoma japonicum eggs was conducted in order to explore its significance, using hosts with differing susceptibilities to the parasite. In experimentally induced, synchronized hepatic granuloma formation, animal species formed each characteristic feature of the granulomas, and the magnitude of tissue reaction was significantly larger in highly susceptible hosts, such as mice and hamsters, while less susceptible hosts, such as rats and quails, formed smaller granulomas. Confluent neutrophils were seen within the tissue lesions for mice and hamsters, while rats and quails showed obviously scanty neutrophils. Guinea pigs failed to develop any granulomas. When splenic cells and bone marrow cells were used for in vitro granuloma formation, bone marrow cells showed markedly higher reactions than splenic cells from naive or sensitized animals and the reactivities of bone marrow cells from susceptible hosts, mice and hamsters, were clearly higher than those from rats, indicating similar results to those of in vivo granuloma formation. This study indicates that the in vivo and in vitro cellular response to S. japonicum eggs varies greatly according to the host's susceptibility, independent of whether the host is a naive or sensitized animal. Our results seem to support the concept that the parasites exploit the host immune system in order to complete their life-span.

Schistosoma japonicum: analysis of eggshell protein genes, their expression, and comparison with similar genes from other schistosomes

As the egg of Schistosoma japonicum plays a central role in transmission and in pathogenesis, we sought to understand the molecular biology of egg formation. In this study we characterized an eggshell protein gene of S. japonicum and compared it with similar genes from S. mansoni and S. haematobium. To initiate studies on the eggshell protein genes of S. japonicum, a cloned genomic fragment containing an entire copy of a S. haematobium eggshell protein gene was used to identify three EcoRI hybridizing fragments of 2.6, 2.0, and 1.3 kbp in S. japonicum genomic DNA and to isolate three independent genomic clones from a S. japonicum genomic library. Two genomic clones, SJ 4-1 and SJ 3-1, contain at least two copies of the gene. The DNA sequence of a 2.0-kbp EcoRI fragment of clone SJ 3-1 showed two open reading frames (ORF), one of which showed a strong homology to the chorion proteins of insects. This ORF had 207 amino acids with a calculated molecular size of 18.5 kDa. The predicted peptide was glycine (50%) and tyrosine (10%) rich like other described schistosome eggshell proteins. Primer extension and the dideoxynucleotide sequence of the mRNA defined the cap site of the RNA and positioned the putative TATA and CAAAT elements and other cis-acting elements. Northern analysis demonstrated that eggshell protein mRNA was only detected in mature female parasites. The appearance of the female-specific mRNA was dependent on pairing with the male parasite and increased with egg production (as determined by hybridization intensity). A comparison of the DNA and deduced protein sequences of eggshell protein genes from S. japonicum with those of similar genes from S. mansoni and S. haematobium indicated that the genes are highly conserved, with S. mansoni and S. haematobium genes being more similar to each other than either is to S. japonicum.

Relative distribution of Schistosoma japonicum eggs in the intestine of man: a subject of inconsistency

The relative distribution of Schistosoma japonicum eggs in the intestine of man is inconsistent in the literature. Some scientists believe that the adult S. japonicum worms reside mainly in the superior mesenteric vein and their eggs are deposited predominately in the small intestine, whereas others have shown that the adult worms have a predilection for inhabiting the branches of the inferior mesenteric vein and superior haemorrhoidal vein and their eggs are deposited in much higher density in the large intestine, especially in the rectum, sigmoid and descending colon, than in the small intestine. A review of the literature was made which includes the results from animal experiments as well as from human clinical and pathological studies. The author is in favour of the latter view that in man, S. japonicum eggs are deposited predominately in the large intestine and small intestine involvement is usually slight.

Schistosomatium douthitti: biochemical and morphological effects of an experimental infection in mice

The pathophysiological changes that occur in mice experimentally infected with Schistosomatium douthitti were studied. Male ICR mice, 6-8 weeks in age, were exposed to 100 cercariae of S. douthitti from infected snails (Lymnaea catascopium) and sacrificed weekly for a total of 13 weeks. Liver homogenates, serum samples, and histological sections of liver tissue were examined. Results showed that body weights of animals with prepatent infections were higher than those of corresponding controls. After patency, which occurred at 5 weeks, body weights were lower and liver weights were higher resulting in significantly increased liver weight/body weight ratios. Hematocrit values declined progressively in patent infections. Total cholesterol in liver was generally higher in the parasitized groups reaching significance during patency. Values rose with age in both control and parasitized groups, but sooner in the latter. Free cholesterol was increased in the liver of animals with patent infections. Total lipid content of the liver was reduced in the infected animals throughout the study. Both liver glycogen and serum glucose levels in the infected animals rose over the control values. The activity of alkaline phosphatase (E.C.3.1.3.1) was elevated in liver tissue of infected mice. Glutamic-pyruvic transaminase (E.C.2.6.1.2) activity was higher in serum but lower in the livers of animals harboring patent infections. Total bile salt concentration in parasitized animals did not differ appreciably from control values; however, gallbladders were enlarged five times in the infected animals. Histologically, liver sections from infected mice showed granulomas in various stages of formation and degeneration. Granulomas contained from 1 to 40 schistosome eggs. After 6 weeks of infection, granulomas were characterized by many neutrophils and monocytes. Few lymphocytes and eosinophils were present. As the granulomas developed, fibroblasts and connective tissue became more prominent. Glycogen deposits were observed surrounding granulomas and were increased in older infections. Adult worms contained abundant amounts of glycogen and cholesterol in their parenchymal tissues.

Schistosoma mansoni: induction of severe glomerulonephritis in female BXSB mice following chronic infection

C57BL/6 (B6) and female BXSB mice were infected with 10 cercariae of Schistosoma mansoni per head in order to examine whether chronic parasite infection induced glomerulonephritis (GN) with polyclonal B-cell activation. Six months after the infection, mice were sacrificed and various immunological and histopathological examinations were performed. The following results were obtained. (1) Severe GN was induced in parasite-infected female BXSB mice. The renal changes were similar to those of male BXSB mice which spontaneously develop lupus-like GN. No substantial renal changes were observed in infected B6 mice. (2) Massive IgG and C3 deposits were found in capillary loops and also at the mesangial area of infected BXSB mice. No significant IC deposits were found in the kidney of infected B6 mice. (3) A high level of IC was detected in sera of some parasite-infected female BXSB mice, though no significant difference in the level of IC was found between infected and control mice. (4) Numbers of spleen IgG-producing cells were significantly increased in infected B6 mice. Infected female BXSB mice with splenomegaly showed higher numbers of IgGPC than uninfected mice, but there was no difference between the groups. These results suggest that genetic backgrounds played an important role in the development of lupus-like GN following the chronic infection of parasite-causing polyclonal B-cell activation.

Hepatoma formation in ddY mice with chronic schistosomiasis japonica

Three hundred and ninety-five four-week-old SPF female ddY mice were each exposed to 5 or 6 cercariae of Schistosoma japonicum (Japanese strain) on their shaved abdomens and were maintained in a conditioned clean environment and fed on sterilized food and water. Fecal examinations at 8 to 10 weeks postinfection (PI) revealed 169 mice to be infected. More than half of them died within 30 weeks PI and 70 mice that survived to the 50th week PI were sacrificed. At autopsy, we could find no schistosome eggs in the liver or intestinal wall of 9 mice, and they were excluded. Out of 61 mice which showed S. japonicum eggs in their livers, 48 had single or multiple hepatoma, while no tumor was observed in the livers of the 60 control mice. The tumors were yellowish-white in color with distinct boundaries and the centers of the tumors were depressed in some cases. The size of the tumors varied from 1 to 20 mm in diameter. Most of the tumors retained the normal trabecular pattern, but in some cases the trabeculae were thickened, having wide vascular spaces. The tumor cells were PAS-negative and showed varieties of pleomorphism. The sizes of cells and nuclei varied greatly. These findings suggested some causal relationship between S. japonicum infection and the hepatoma formation in the host's liver. In the chronic course of schistosomiasis japonica in the endemic areas, S. japonicum infection probably plays a role in hepatoma formation of patients.

The pathology of experimental Schistosoma curassoni infections in mice and hamsters

The histopathology of experimental Schistosoma curassoni infections in white mice and hamsters was studied. In mice, hepatic lesions were severe with characteristic extensive perilobular fibrosis and large perilobular granulomas throughout the parenchyma. Only a few granulomas were detected in the lung, small intestine, and rectum of mice. In hamsters, lesions in the liver were limited. Few granulomas were found but the giant cell reaction was pronounced. Lesions in the lung and small intestine were minimal. Many subserosal and submucosal epithelioid cell granulomas were in the colon and rectum of hamsters. Parasites were not detected in the bladder of either mice or hamsters.