Circulating miRNAs: Potential Novel Biomarkers for Hepatopathology Progression and Diagnosis of Schistosomiasis Japonica in Two Murine Models

Background

Schistosomiasis remains a major public health issue, with an estimated 230 million people infected worldwide. Novel tools for early diagnosis and surveillance of schistosomiasis are currently needed. Elevated levels of circulating microRNAs (miRNAs) are commonly associated with the initiation and progression of human disease pathology. Hence, serum miRNAs are emerging as promising biomarkers for the diagnosis of a variety of human diseases. This study investigated circulating host miRNAs commonly associated with liver diseases and schistosome parasite-derived miRNAs during the progression of hepatic schistosomiasis japonica in two murine models.

Methodology/Principal Findings

Two mouse strains (C57BL/6 and BALB/c) were infected with a low dosage of Schistosoma japonicum cercariae. The dynamic patterns of hepatopathology, the serum levels of liver injury-related enzymes and the serum circulating miRNAs (both host and parasite-derived) levels were then assessed in the progression of schistosomiasis japonica. For the first time, an inverse correlation between the severity of hepatocyte necrosis and the level of liver fibrosis was revealed during S. japonicum infection in BALB/c, but not in C57BL/6 mice. The inconsistent levels of the host circulating miRNAs, miR-122, miR-21 and miR-34a in serum were confirmed in the two murine models during infection, which limits their potential value as individual diagnostic biomarkers for schistosomiasis. However, their serum levels in combination may serve as a novel biomarker to mirror the hepatic immune responses induced in the mammalian host during schistosome infection and the degree of hepatopathology. Further, two circulating parasite-specific miRNAs, sja-miR-277 and sja-miR-3479-3p, were shown to have potential as diagnostic markers for schistosomiasis japonica.

Conclusions/Significance

We provide the first evidence for the potential of utilizing circulating host miRNAs to indicate different immune responses and the severity of hepatopathology outcomes induced in two murine strains infected with S. japonicum. This study also establishes a basis for the early and cell-free diagnosis of schistosomiasis by targeting circulating schistosome parasite-derived miRNAs.     

DNA Detection of Schistosoma japonicum: Diagnostic Validity of a LAMP Assay for Low-Intensity Infection and Effects of Chemotherapy in Humans

Background

Schistosomiasis has decreased significantly in prevalence and intensity of infection in China, thus more accurate and sensitive methods are desperately needed for the further control of schistosomiasis. The present work aimed to assess the utility of the loop-mediated isothermal amplification (LAMP) for detection of light intensity infection or false-negative patients and patients post-treatment, targeting the highly repetitive retrotransposon SjR2 of Schistosoma japonicum.

Methodology/ Principal Findings

LAMP was first assessed in rabbits with low intensity infection (EPG<10). Then 110 patient sera from Hunan Province, China, and 47 sera after treatment by praziquantel were used to evaluate the diagnostic validity of LAMP. Meanwhile, 42 sera from healthy individuals in a non-endemic area, and 60 sera from "healthy” residents who were identified as being negative for feces examination and immuno-methods in an endemic area were also examined. The results showed that LAMP could detect S. japonicum DNA in sera from rabbits at 3^rd day post-infection. Following administration of praziquantel, the S. japonicum DNA in rabbit sera became negative at 10 weeks post-treatment. Of 110 sera from patients, LAMP showed 95.5% sensitivity, and even for 41 patients with less than 10 EPG, the sensitivity of LAMP still reached to 95.1%. For 47 patients after treatment, the negative conversion rate of S. japonicum DNA in patient sera increased from 23.4%, 61.7% to 83.0% at 3 months, 6 months and 9 months post-treatment, respectively. No false-positive result was obtained for 42 human sera from non-endemic area, while for the 60 “healthy” individuals from endemic area, 10 (16.7%) individuals were positive by LAMP, which suggested that these individuals might be false-negative patients.

Conclusions/ Significance

The present study demonstrated that the LAMP assay is sensitive, specific, and affordable, which would help reduce schistosomiasis transmission through targeted treatment of individuals, particularly for those with negative stool examinations who may yet remain infected. The LAMP assay may provide a potential tool to support schistosomiasis control and elimination strategies.     

Characterization of VAMP2 in Schistosoma japonicum and the Evaluation of Protective Efficacy Induced by Recombinant SjVAMP2 in Mice

Background

The outer-tegument membrane covering the schistosome is believed to maintain via the fusion of membranous vesicles. Fusion of biological membranes is a fundamental process in all eukaryotic cells driven by formation of trans-SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) complexes through pairing of vesicle associated v-SNAREs (VAMP) with complementary t-SNAREs on target membranes. The purpose of this study was to characterize Schistosoma japonicum vesicle-associated membrane protein 2 (SjVAMP2) and to investigate its potential as a candidate vaccine against schistosomiasis.

Methodology/Principal Findings

The sequence of SjVAMP2 was analyzed, cloned, expressed and characterized. SjVAMP2 is a member of the synaptobrevin superfamily harboring the v-SNARE coiled-coil homology domain. RT–PCR analysis revealed that significantly higher SjVAMP2 levels were observed in 14-, 28- and 42-day-old worms, and SjVAMP2 expression was much higher in 42-day-old female worms than in those male worms. Additionally, the expression of SjVAMP2 was associated with membrane recovery in PZQ-treated worms. Immunostaining assay showed that SjVAMP2 was mainly distributed in the sub-tegument of the worms. Western blotting revealed that rSjVAMP2 showed strong immunogenicity. Purified rSjVAMP2 emulsified with ISA206 adjuvant induced 41.5% and 27.3% reductions in worm burden, and 36.8% and 23.3% reductions in hepatic eggs in two independent trials. Besides, significantly higher rSjVAMP2-specific IgG, IgG1, IgG2a levels were detected in rSjVAMP2-vaccinated mice.

Conclusion

Our study indicated that SjVAMP2 is a potential vaccine candidate against S. japonicum and provided the basis for further investigations into the biological function of SjVAMP2.     

Real-time PCR Demonstrates High Prevalence of Schistosoma japonicum in the Philippines: Implications for Surveillance and Control

Background

The Philippines has a population of approximately 103 million people, of which 6.7 million live in schistosomiasis-endemic areas with 1.8 million people being at risk of infection with Schistosoma japonicum. Although the country-wide prevalence of schistosomiasis japonica in the Philippines is relatively low, the prevalence of schistosomiasis can be high, approaching 65% in some endemic areas. Of the currently available microscopy-based diagnostic techniques for detecting schistosome infections in the Philippines and elsewhere, most exhibit varying diagnostic performances, with the Kato-Katz (KK) method having particularly poor sensitivity for detecting low intensity infections. This suggests that the actual prevalence of schistosomiasis japonica may be much higher than previous reports have indicated.

Methodology/Principal Findings

Six barangay (villages) were selected to determine the prevalence of S. japonicum in humans in the municipality of Palapag, Northern Samar. Fecal samples were collected from 560 humans and examined by the KK method and a validated real-time PCR (qPCR) assay. A high S. japonicum prevalence (90.2%) was revealed using qPCR whereas the KK method indicated a lower prevalence (22.9%). The geometric mean eggs per gram (GMEPG) determined by the qPCR was 36.5 and 11.5 by the KK. These results, particularly those obtained by the qPCR, indicate that the prevalence of schistosomiasis in this region of the Philippines is much higher than historically reported.

Conclusions/Significance

Despite being more expensive, qPCR can complement the KK procedure, particularly for surveillance and monitoring of areas where extensive schistosomiasis control has led to low prevalence and intensity infections and where schistosomiasis elimination is on the horizon, as for example in southern China.     

Utilization of ELISA Using Thioredoxin Peroxidase-1 and Tandem Repeat Proteins for Diagnosis of Schistosoma japonicum Infection among Water Buffaloes

Background

The presence of animal reservoirs in Schistosoma japonicum infection has been a major obstacle in the control of schistosomiasis. Previous studies have proven that the inclusion of control measures on animal reservoir hosts for schistosomiasis contributed to the decrease of human cases. Animal surveillance should therefore be included to strengthen and improve the capabilities of current serological tests.

Methodology/Principal Findings

Thioredoxin peroxidase-1 (SjTPx-1) and four tandem repeat proteins (Sj1TR, Sj2TR, Sj4TR, Sj7TR) were initially evaluated against human sera. The previous test showed high sensitivity and specificity for antibody detection against SjTPx-1 and Sj7TR. In this study, the immunodiagnostic potential of these recombinant proteins was evaluated using enzyme-linked immunoassay on 50 water buffalo serum samples collected in Cagayan, the Philippines as compared with the soluble egg antigen (SEA). For specificity, 3 goat serum samples positive with Fasciola hepatica were used and among the antigens used, only SEA showed cross-reaction. Stool PCR targeting the S. japonicum 82 bp mitochondrial NAD 1 gene was done to confirm the true positives and served as the standard test. Twenty three samples were positive for stool PCR. SjTPx-1 and Sj1TR gave the highest sensitivity among the recombinant proteins tested for water buffalo samples with 82.61% and 78.26% respectively which were higher than that of SEA (69.57%).

Conclusions/Significance

These results prove that SjTPx-1 works both for humans and water buffaloes making it a good candidate antigen for zoonotic diagnosis. Sj1TR showed good results for water buffaloes and therefore can also be used as a possible candidate for detecting animal schistosome infection.     

Sensitive and specific target sequences selected from retrotransposons of Schistosoma japonicum for the diagnosis of schistosomiasis

Background

Schistosomiasis japonica is a serious debilitating and sometimes fatal disease. Accurate diagnostic tests play a key role in patient management and control of the disease. However, currently available diagnostic methods are not ideal, and the detection of the parasite DNA in blood samples has turned out to be one of the most promising tools for the diagnosis of schistosomiasis. In our previous investigations, a 230-bp sequence from the highly repetitive retrotransposon SjR2 was identified and it showed high sensitivity and specificity for detecting Schistosoma japonicum DNA in the sera of rabbit model and patients. Recently, 29 retrotransposons were found in S. japonicum genome by our group. The present study highlighted the key factors for selecting a new perspective sensitive target DNA sequence for the diagnosis of schistosomiasis, which can serve as example for other parasitic pathogens.

Methodology/Principal Findings

In this study, we demonstrated that the key factors based on the bioinformatic analysis for selecting target sequence are the higher genome proportion, repetitive complete copies and partial copies, and active ESTs than the others in the chromosome genome. New primers based on 25 novel retrotransposons and SjR2 were designed and their sensitivity and specificity for detecting S. japonicum DNA were compared. The results showed that a new 303-bp sequence from non-long terminal repeat (LTR) retrotransposon (SjCHGCS19) had high sensitivity and specificity. The 303-bp target sequence was amplified from the sera of rabbit model at 3 d post-infection by nested-PCR and it became negative at 17 weeks post-treatment. Furthermore, the percentage sensitivity of the nested-PCR was 97.67% in 43 serum samples of S. japonicum-infected patients.

Conclusions/Significance

Our findings highlighted the key factors based on the bioinformatic analysis for selecting target sequence from S. japonicum genome, which provide basis for establishing powerful molecular diagnostic techniques that can be used for monitoring early infection and therapy efficacy to support schistosomiasis control programs.     

Spatial Analysis of Schistosomiasis in Hubei Province,China: A GIS-Based Analysis of Schistosomiasis from 2009 to 2013

Background

Schistosomiasis remains a major public health problem in China. The major endemic areas are located in the lake and marshland regions of southern China, particularly in areas along the middle and low reach of the Yangtze River. Spatial analytical techniques are often used in epidemiology to identify spatial clusters in disease regions. This study assesses the spatial distribution of schistosomiasis and explores high-risk regions in Hubei Province, China to provide guidance on schistosomiasis control in marshland regions.

Methods

In this study, spatial autocorrelation methodologies, including global Moran’s I and local Getis–Ord statistics, were utilized to describe and map spatial clusters and areas where human Schistosoma japonicum infection is prevalent at the county level in Hubei province. In addition, linear logistic regression model was used to determine the characteristics of spatial autocorrelation with time.

Results

The infection rates of S. japonicum decreased from 2009 to 2013. The global autocorrelation analysis results on the infection rate of S. japonicum for five years showed statistical significance (Moran’s I > 0, P < 0.01), which suggested that spatial clusters were present in the distribution of S. japonicum infection from 2009 to 2013. Local autocorrelation analysis results showed that the number of highly aggregated areas ranged from eight to eleven within the five-year analysis period. The highly aggregated areas were mainly distributed in eight counties.

Conclusions

The spatial distribution of human S. japonicum infections did not exhibit a temporal change at the county level in Hubei Province. The risk factors that influence human S. japonicum transmission may not have changed after achieving the national criterion of infection control. The findings indicated that spatial–temporal surveillance of S. japonicum transmission plays a significant role on schistosomiasis control. Timely and integrated prevention should be continued, especially in the Yangtze River Basin of Jianghan Plain area.     

Comparative Phylogenetic Studies on Schistosoma japonicum and Its Snail Intermediate Host Oncomelania hupensis: Origins,Dispersal and Coevolution

Background

Schistosoma japonicum causes major public health problems in China and the Philippines; this parasite, which is transmitted by freshwater snails of the species Oncomelania hupensis, causes the disease intestinal schistosomiasis in humans and cattle. Researchers working on Schistosoma in Africa have described the relationship between the parasites and their snail intermediate hosts as coevolved or even as an evolutionary arms race. In the present study this hypothesis of coevolution is evaluated for S. japonicum and O. hupensis. The origins and radiation of the snails and the parasite across China, and the taxonomic validity of the sub-species of O. hupensis, are also assessed.

Methodology/Principal Findings

The findings provide no evidence for coevolution between S. japonicum and O. hupensis, and the phylogeographical analysis suggests a heterochronous radiation of the parasites and snails in response to different palaeogeographical and climatic triggers. The results are consistent with a hypothesis of East to West colonisation of China by Oncomelania with a re-invasion of Japan by O. hupensis from China. The Taiwan population of S. japonicum appears to be recently established in comparison with mainland Chinese populations.

Conclusions/Significance

The snail and parasite populations of the western mountain region of China (Yunnan and Sichuan) appear to have been isolated from Southeast Asian populations since the Pleistocene; this has implications for road and rail links being constructed in the region, which will breach biogeographical barriers between China and Southeast Asia. The results also have implications for the spread of S. japonicum. In the absence of coevolution, the parasite may more readily colonise new snail populations to which it is not locally adapted, or even new intermediate host species; this can facilitate its dispersal into new areas. Additional work is required to assess further the risk of spread of S. japonicum.     

Epidemiology of Schistosomiasis and Usefulness of Indirect Diagnostic Tests in School-Age Children in Cubal,Central Angola

Introduction

Schistosomiasis remains a public health major problem and little is known in many areas, mainly in Sub-Saharan Africa

Objectives

To assess the burden and risk factors of schistosomiasis and intestinal parasitic helminthes in the children of Cubal, Angola, and to compare different diagnostic approaches for urinary schistosomiasis under field conditions.

Methods

A cross-sectional study was conducted. Urine and faeces samples of school children were microscopically studied. A random sample of children was obtained from an alphabetically arranged list of children, taking one of two children. Urine dipstick, colorimetric test and macrohaematuria were considered as indirect diagnostic methods and compared to direct urine examination. Possible risk factors for the infection were sex, age, distance to the river and previous treatment with praziquantel; the assessment was performed using Chi-square test.

Results

A total of 785 (61.18%) children showed S. haematobium eggs in urine; children living within 500 meters from the river had a higher odds for infection: Odds ratio 1.97 (1.45–2.7 CI 95%); urine dipstick showed sensitivity of 96% and specificity of 61.3%, with a positive predictive value; colorimetric test showed sensitivity of 52.5%, specificity of 74.6% and a positive predictive value of 77%. Proteinuria was present in 653 (51.1%) children, being more frequent in children with S. haematobium in urine (75.2%); 32 of 191 stool samples (16%) showed the presence of other intestinal parasites and 8 (4%) for S. haematobium.

Conclusions

Prevalence of urinary schistosomiasis in our study area is much higher than the national average, considering it as a high-risk community. Proximity to a source of water was a risk factor for the infection. Indirect tests, as urine dipstick and colorimetric test, were useful tools for diagnosis, due to ease of use and low cost. Proteinuria was a common finding, probably showing an early structural damage due to schistosomiasis in this group of children.     

Heat Shock Protein 60 in Eggs Specifically Induces Tregs and Reduces Liver Immunopathology in Mice with Schistosomiasis Japonica

Background

Parasitic helminths need to suppress the host immune system to establish chronic infections. Paradoxically, immunosuppression induced by the worm also benefits the host by limiting excessive inflammation and tissue damage, which remains the major cause leading to serious morbidity and mortality. Regulatory T cells (Tregs) are key immune regulators of this mutualism. The successive rise in Tregs during schistosome infection plays a critical role in immunoregulation. We and others previously showed that Schistosoma japonicum (S. japonicum) egg antigens (SEA) induce Tregs both in vitro and in vivo. In addition, we identified that SjHSP60 derived from SEA significantly induces Tregs in vivo and in vitro. However, the contribution of SjHSP60 in SEA to Treg induction and the related mechanisms of the Treg induction have not yet been identified.

Methodology/Principal Findings

In this study, we showed that S. japonicum stress protein HSP60 (SjHSP60) was constitutively and extensively expressed in eggs of S. japonicum. SjHSP60 specially induced Tregs in vivo and in vitro without inducing other CD4⁺ T sub-populations including Th1, Th2 and Th17 cells. Furthermore, we showed that the SjHSP60-depleted SEA almost lost the ability in vitro and displayed a significant impaired ability to induce Tregs in vivo. Finally, our study illustrated that the mechanisms of SjHSP60-mediated induction of Tregs are through both conversion of CD4⁺CD25^- T cells into CD4⁺CD25⁺Foxp3⁺ Tregs and expansion of preexisting CD4⁺CD25⁺Foxp3⁺ Tregs in a TLR4-dependent manner.

Conclusions/Significance

Collectively, our findings identify SjHSP60 as a major parasitic contributor of Treg induction in S. japonicum egg antigens, which not only contributes to the better understanding of the mechanism of immunoregulation during helminth infection, but also suggests its potential as a therapeutic target for control of immunopathology, allergic and autoimmune diseases.     

PAMAM-Lys,a Novel Vaccine Delivery Vector,Enhances the Protective Effects of the SjC23 DNA Vaccine against Schistosoma japonicum Infection

Background

Schistosomiasis japonica remains a major public-health concern in China. Praziquantel-based chemotherapy effectively reduces both infections and intensity; however, it can not prevent re-infection. Furthermore, there is an increasing concern about praziquantel resistance following long-term repeated use of the drug in endemic areas. Therefore, development of a schistosomiasis vaccine, as a strategy to prevent and control schistosomiasis japonica, has been given high priority. The present study was conducted to develop PAMAM dendrimers as a novel vaccine delivery vector for a schistosomiasis japonica DNA vaccine and evaluate its ability to enhance protective effects against Schistosoma japonicum infection.

Methodology/Principal Findings

Lysine was used to modify 4.0G PAMAM, and the modified product PAMAM-Lys was synthesized. PAMAM-Lys showed both high transfection and low cytotocity for gene delivery in vitro. DNA vaccines combined with PAMAM-Lys produced higher level of protection compare with naked DNA vaccines against S. japonicum infection in a mouse model. Futhermore,antibodies from mice immunized with PAMAM-Lys combined DNA vaccines were significantly higher than those of mice immunized with the naked DNA vaccines. The PAMAM-Lys vector elicited a predominantly IgG2a antibody response and a tremendously increase in the production of IL-2 and IFN-γ.

Conclusion/Significance

Lysine-modified PAMAM-Lys is an excellent vector. PAMAM-Lys may enhance the immunoreactivity of DNA vaccine and increase the protective effect of the SjC23 DNA vaccine against S. japonicum infection.     

Shifts in the Spatiotemporal Dynamics of Schistosomiasis: A Case Study in Anhui Province,China

Background

The Chinese national surveillance system showed that the risk of Schistosoma japonicum infection fluctuated temporally. This dynamical change might indicate periodicity of the disease, and its understanding could significantly improve targeted interventions to reduce the burden of schistosomiasis. The goal of this study was to investigate how the schistosomiasis risk varied temporally and spatially in recent years.

Methodology/Principal Findings

Parasitological data were obtained through repeated cross-sectional surveys that were carried out during 1997-2010 in Anhui Province, East China. A multivariate autoregressive model, combined with principal oscillation pattern (POP) analysis, was used to evaluate the spatio-temporal variation of schistosomiasis risk. Results showed that the temporal changes of schistosomiasis risk in the study area could be decomposed into two sustained damped oscillatory modes with estimated period of approximately 2.5 years. The POPs associated with these oscillatory components showed that the pattern near the Yangtze River varied markedly and that the disease risk appeared to evolve in a Southwest/Northeast orientation. The POP coefficients showed decreasing tendency until 2001, then increasing during 2002-2005 and decaying afterwards.

Conclusion

The POP analysis characterized the variations of schistosomiasis risk over space and time and demonstrated that the disease mainly varied temporally along the Yangtze River. The schistosomiasis risk declined periodically with a temporal fluctuation. Whether it resulted from previous national control strategies on schistosomiasis needs further investigations.     

A piezoelectric immunosensor using hybrid self-assembled monolayers for detection of Schistosoma japonicum

Background

The parasite Schistosoma japonicum causes schistosomiasis disease, which threatens human life and hampers economic and social development in some Asian countries. An important lesson learned from efforts to reduce the occurrence of schistosomiasis is that the diagnostic approach must be altered as further progress is made towards the control and ultimate elimination of the disease.

Methodology/Principal Findings

Using mixed self-assembled monolayer membrane (mixed SAM) technology, a mixture of mercaptopropionic acid (MPA) and mercaptoethanol (ME) was self-assembled on the surface of quartz crystals by gold-sulphur-bonds. Soluble egg antigens (SEA) of S. japonicum were then cross-linked to the quartz crystal using a special coupling agent. As compared with the traditional single self-assembled monolayer immobilization method, S. japonicum antigen (SjAg) immobilization using mixed self-assembled monolayers exhibits much greater immunoreactivity. Under optimal experimental conditions, the detection range is 1∶1500 to 1∶60 (infected rabbit serum dilution ratios). We measured several infected rabbit serum samples with varying S. japonicum antibody (SjAb) concentrations using both immunosensor and ELISA techniques and then produced a correlation analysis. The correlation coefficients reached 0.973.

Conclusions/Significance

We have developed a new, simple, sensitive, and reusable piezoelectric immunosensor that directly detects SjAb in the serum. This method may represent an alternative to the current diagnostic methods for S. japonicum infection in the clinical laboratory or for analysis outside the laboratory.     

Distribution of Peripheral Memory T Follicular Helper Cells in Patients with Schistosomiasis Japonica

Background

Schistosomiasis is a helminthic disease that affects more than 200 million people. An effective vaccine would be a major step towards eliminating the disease. Studies suggest that T follicular helper (Tfh) cells provide help to B cells to generate the long-term humoral immunity, which would be a crucial component of successful vaccines. Thus, understanding the biological characteristics of Tfh cells in patients with schistosomiasis, which has never been explored, is essential for vaccine design.

Methodology/Principal Findings

In this study, we investigated the biological characteristics of peripheral memory Tfh cells in schistosomiasis patients by flow cytometry. Our data showed that the frequencies of total and activated peripheral memory Tfh cells in patients were significantly increased during Schistosoma japonicum infection. Moreover, Tfh2 cells, which were reported to be a specific subpopulation to facilitate the generation of protective antibodies, were increased more greatly than other subpopulations of total peripheral memory Tfh cells in patients with schistosomiasis japonica. More importantly, our result showed significant correlations of the percentage of Tfh2 cells with both the frequency of plasma cells and the level of IgG antibody. In addition, our results showed that the percentage of T follicular regulatory (Tfr) cells was also increased in patients with schistosomiasis.

Conclusions/Significance

Our report is the first characterization of peripheral memory Tfh cells in schistosomasis patients, which not only provides potential targets to improve immune response to vaccination, but also is important for the development of vaccination strategies to control schistosomiasis.     

Thioredoxin glutathione reductase as a novel drug target: evidence from Schistosoma japonicum

Background

Schistosomiasis remains a major public health concern affecting billions of people around the world. Currently, praziquantel is the only drug of choice for treatment of human schistosomiasis. The emergence of drug resistance to praziquantel in schistosomes makes the development of novel drugs an urgent task. Thioredoxin glutathione reductase (TGR) enzymes in Schistosoma mansoni and some other platyhelminths have been identified as alternative targets. The present study was designed to confirm the existense and the potential value of TGR as a target for development of novel antischistosomal agents in Schistosoma japonicum, a platyhelminth endemic in Asia.

Methods and Findings

After cloning the S. japonicum TGR (SjTGR) gene, the recombinant SjTGR selenoprotein was purified and characterized in enzymatic assays as a multifunctional enzyme with thioredoxin reductase (TrxR), glutathione reductase (GR) and glutaredoxin (Grx) activities. Immunological and bioinformatic analyses confirmed that instead of having separate TrxR and GR proteins in mammalian, S. japonicum only encodes TGR, which performs the functions of both enzymes and plays a critical role in maintaining the redox balance in this parasite. These results were in good agreement with previous findings in Schistosoma mansoni and some other platyhelminths. Auranofin, a known inhibitor against TGR, caused fatal toxicity in S. japonicum adult worms in vitro and reduced worm and egg burdens in S. japonicum infected mice.

Conclusions

Collectively, our study confirms that a multifunctional enzyme SjTGR selenoprotein, instead of separate TrxR and GR enzymes, exists in S. japonicum. Furthermore, TGR may be a potential target for development of novel agents against schistosomes. This assumption is strengthened by our demonstration that the SjTGR is an essential enzyme for maintaining the thiol-disulfide redox homeostasis of S. japonicum.     

Five-year longitudinal assessment of the downstream impact on schistosomiasis transmission following closure of the Three Gorges Dam

Background

Schistosoma japonicum is a major public health concern in the Peoples'' Republic of China (PRC), with about 800,000 people infected and another 50 million living in areas at risk of infection. Based on ecological, environmental, population genetic and molecular factors, schistosomiasis transmission in PRC can be categorised into four discrete ecosystems or transmission modes. It is predicted that, long-term, the Three Gorges Dam (TGD) will impact upon the transmission of schistosomiasis in the PRC, with varying degree across the four transmission modes.

Methodology/Principal Findings

We undertook longitudinal surveillance from 2002 to 2006 in sentinel villages of the three transmission modes below the TGD across four provinces (Hunan, Jiangxi, Hubei and Anhui) to determine whether there was any immediate impact of the TGD on schistosomiasis transmission. Eight sentinel villages were selected to represent both province and transmission mode. The primary end point measured was human incidence. Here we present the results of this five-year longitudinal cohort study. Results showed that the incidence of human S. japonicum infection declined considerably within individual villages and overall mode over the course of the study. This is also reflected in the yearly odds ratios (adjusted) for infection risk that showed significant (P<0.01) downward trends in all modes over the follow-up period.

Conclusions/Significance

The decrease in human S. japonicum incidence observed across all transmission modes in this study can probably be attributed to the annual human and bovine PZQ chemotherapy. If an increase in schistosome transmission had occurred as a result of the TGD, it would be of negligible size compared to the treatment induced decline seen here. It appears therefore that there has been virtually no immediate impact of the TGD on schistosomiasis transmission downstream of the dam.     

Evaluation of mammalian and intermediate host surveillance methods for detecting schistosomiasis reemergence in southwest China

Background

Schistosomiasis has reemerged in China, threatening schistosomiasis elimination efforts. Surveillance methods that can identify locations where schistosomiasis has reemerged are needed to prevent the further spread of infections.

Methods and Principal Findings

We tested humans, cows, water buffalo and the intermediate host snail, Oncomelania hupensis, for Schistosoma japonicum infection, assessed snail densities and extracted regional surveillance records in areas where schistosomiasis reemerged in Sichuan province. We then evaluated the ability of surveillance methods to identify villages where human infections were present. Human infections were detected in 35 of the 53 villages surveyed (infection prevalence: 0 to 43%), including 17 of 28 villages with no prior evidence of reemergence. Bovine infections were detected in 23 villages (infection prevalence: 0 to 65%) and snail infections in one village. Two common surveillance methods, acute schistosomiasis case reports and surveys for S. japonicum-infected snails, grossly underestimated the number of villages where human infections were present (sensitivity 1% and 3%, respectively). Screening bovines for S. japonicum and surveys for the presence of O. hupensis had modest sensitivity (59% and 69% respectively) and specificity (67% and 44%, respectively). Older adults and bovine owners were at elevated risk of infection. Testing only these high-risk human populations yielded sensitivities of 77% and 71%, respectively.

Conclusions

Human and bovine schistosomiasis were widespread in regions where schistosomiasis had reemerged but acute schistosomiasis and S. japonicum-infected snails were rare and, therefore, poor surveillance targets. Until more efficient, sensitive surveillance strategies are developed, direct, targeted parasitological testing of high-risk human populations should be considered to monitor for schistosomiasis reemergence.     

The Potential for a Blood Test for Scabies

Background

Scabies afflicts millions of people worldwide, but it is very difficult to diagnose by the usual skin scrape test, and a presumptive diagnosis is often made based on clinical signs such as rash and intense itch. A sensitive and specific blood test to detect scabies would allow a physician to quickly make a correct diagnosis.

Objective

Our objective was to profile the mite-specific antibodies present in the sera of patients with ordinary scabies.

Methods

Sera of 91 patients were screened for Ig, IgD, IgE, IgG and IgM antibodies to S. scabiei, as well as to the house dust mites Dermatophagoides farinae, D. pteronyssinus and Euroglyphus maynei.

Results

45%, 27% and 2.2% of the patients had measurable amounts of mixed Ig, IgG and IgE that recognized scabies mite antigens. However, 73.6% of the scabies patients had serum IgM that recognized scabies proteins, and all except two of them also had IgM that recognized all of the three species of dust mites. No patient had serum antibody exclusively reactive to scabies mite antigens.

Conclusions

Co-sensitization or cross-reactivity between antigens from scabies and house dust mites confounds developing a blood test for scabies.