Screening diagnostic candidates for schistosomiasis from tegument proteins of adult Schistosoma japonicum using an immunoproteomic approach

Advancing vaccine development against Opisthorchis viverrini: A synergistic integration of omics technologies and advanced computational tools

The liver fluke O. viverrini (Opisthorchis viverrini), a neglected tropical disease (NTD), endemic to the Great Mekong Subregion (GMS), mainly afflicts the northeastern region of Thailand. It is a leading cause of cholangiocarcinoma (CCA) in humans. Presently, the treatment modalities for opisthorchiasis incorporate the use of the antihelminthic drug praziquantel, the rapid occurrence of reinfection, and the looming threat of drug resistance highlight the urgent need for vaccine development. Recent advances in "omics" technologies have proven to be a powerful tool for such studies. Utilizing candidate proteins identified through proteomics and refined via immunoproteomics, reverse vaccinology (RV) offers promising prospects for designing vaccines targeting essential antibody responses to eliminate parasite. Machine learning-based computational tools can predict epitopes of candidate protein/antigens exhibiting high binding affinities for B cells, MHC classes I and II, indicating strong potential for triggering both humoral and cell-mediated immune responses. Subsequently, these vaccine designs can undergo population-specific testing and docking/dynamics studies to assess efficacy and synergistic immunogenicity. Hence, refining proteomics data through immunoinformatics and employing computational tools to generate antigen-specific targets for trials offers a targeted and efficient approach to vaccine development that applies to all domains of parasite infections. In this review, we delve into the strategic antigen selection process using omics modalities for the O. viverrini parasite and propose an innovative framework for vaccine design. We harness omics technologies to revolutionize vaccine development, promising accelerated discoveries and streamlined preclinical and clinical evaluations.

Salmonella typhimurium targeting with monoclonal antibodies prevents infection in mice

Salmonella is a prevalent foodborne and waterborne pathogens threating global public health and food safety. Given the diversity of Salmonella serotypes and the emergence of antibiotic-resistant strains, there is an urgent need for the development of broadly protective therapies. This study aims to prepare monoclonal antibodies (Mabs) with broad reactivity against multi-serotype Salmonella strains, potentially offering cross-protection. We prepared two Mabs F1D4 and B7D4 against protein FliK and BcsZ, two potential vaccine candidates against multi-serotype Salmonella. The two Mabs belonging to IgG1 isotype exhibited high titers of 1:256,000 and 1:512,000 respectively, as well as broad cross-reactivity against 28 different serotypes of Salmonella strains with percentages of 89.29% and 92.86%, correspondingly. Neutralizing effects of the two Mabs on Salmonella growth, adhesion, invasion and motility was evaluated in vitro using bacteriostatic and bactericidal activity with and without complement and bacterial invasion inhibition assay. Additionally, cytotoxicity assays, animal toxicity analyses, and pharmacokinetic evaluations demonstrated the safety and sustained effectiveness of both Mabs. Furthermore, F1D4 or B7D4-therapy in mice challenged with S. Typhimurium LT2 exhibited milder organs damage and lower Salmonella colonization, as well as the higher relative survival of 86.67% and 93.33% respectively. This study produced two broadly reactive and potential cross protective Mabs F1D4 and B7D4, which offered new possibilities for immunotherapy of salmonellosis.

Schistosoma japonicum Tyrosine Hydroxylase is promising targets for immunodiagnosis and immunoprotection of Schistosomiasis japonica

Identification of promising schistosome antigen targets is crucial for the development of anti-schistosomal strategies. Schistosomes rely on their neuromuscular systems to coordinate important locomotory behaviors. Tyrosine hydroxylase (TH) is critical in the initial rate-limiting step in biosynthesis of catecholamine, the important neuroactive agents, which promote the lengthening of the worm through muscular relaxation and are therefore of great importance to the movement of the organism both within and between its hosts. THs from both Schistosoma mansoni and Schistosoma japonicum and their enzyme activities have been discovered; however, the role of these proteins during infection have not been explored. Herein, a recombinant protein of the nonconserved fragment of S. japonicum TH (SjTH) was produced and the corresponding polyclonal antibody was generated. The expression and antigenicity of SjTH were detected by qRT-PCR, western blotting, immunofluorescence assays, and ELISA. Mice immunized with the recombinant SjTH were challenged with cercariae to evaluate the immunoprotective value of this protein. Our results showed SjTH not only distributed in the head associated with the central nervous system, but also expressed along the tegument and the intestinal intima, which are involved in the movement, coupling and digestion of the parasites and associated with the peripheral nervous system. This protein can effectively stimulate humoral immune responses in mammalian hosts and has high potential as a biomarker for schistosomiasis immunodiagnosis. Furthermore, immunization with recombinant SjTH showed to reduce the worm and egg burden of challenged mice, and to contribute to the systemic balance of the Th1/Th2 responses. Taken together, these results suggest that SjTH is an important pathogenic molecule in S. japonicum and may be a possible target for anti-schistosomal approaches.

Advances in Diagnosis of Schistosomiasis: Focus on Challenges and Future Approaches

Schistosomiasis is the second most devastating parasite prevalent in the tropical region of the world, posing significant public health impacts in endemic areas. Presently, several disease mitigation measures have shown a decline in transmission of the infection rate in risk localities using mass drug administration (MDA) of school-based or community-wide treatments. Despite all the endeavors made, the decline in transmission of infection rate has not been attained in the entire medicated segment of the population. Perhaps the current challenges of control of the disease appear to be strongly associated with a lack of appropriate diagnostic tools. It's well known that the current diagnosis of schistosomiasis greatly relies on conventional methods. On the other hand, minor symptoms of schistosomiasis and low sensitivity and specificity of diagnostic methods are still unresolved diagnostic challenges to clinicians. Numerous scholars have reviewed various diagnostic methods of schistosomiasis and attempted to identify their strengths and weaknesses, currently on function. As a result of the known limitations of the existing diagnostic tools, the need to develop new and feasible diagnostic methods and diagnostic markers is unquestionable for more precise detection of the infection. Hence, advances in diagnostic methods have been considered part of the solution for the control and eventual elimination strategy of the disease in endemic areas. As of today, easy, cheap, and accurate diagnostics for schistosomiasis are difficult to get, and this limits the concerted efforts towards full control of schistosomiasis. While looking for new diagnostic methods and markers, it is important to simultaneously work on improving the existing diagnostic methods for better results. This review tries to give new insights to the status of the existing diagnostic methods of schistosomiasis from conventional to modern via summarizing the strengths and limitations of the methods. It also tries to recommend new, sensitive and feasible diagnostic methods for future approaches.

Cloning, Expression and Evaluation of Thioredoxin Peroxidase-1 Antigen for the Serological Diagnosis of Schistosoma mekongi Human Infection

Schistosoma mekongi, a blood fluke that causes Asian zoonotic schistosomiasis, is distributed in communities along the Mekong River in Cambodia and Lao People's Democratic Republic. Decades of employing numerous control measures including mass drug administration using praziquantel have resulted in a decline in the prevalence of schistosomiasis mekongi. This, however, led to a decrease in sensitivity of Kato-Katz stool microscopy considered as the gold standard in diagnosis. In order to develop a serological assay with high sensitivity and specificity which can replace Kato-Katz, recombinant S. mekongi thioredoxin peroxidase-1 protein (rSmekTPx-1) was expressed and produced. Diagnostic performance of the rSmekTPx-1 antigen through ELISA for detecting human schistosomiasis was compared with that of recombinant protein of S. japonicum TPx-1 (rSjTPx-1) using serum samples collected from endemic foci in Cambodia. The sensitivity and specificity of rSmekTPx-1 in ELISA were 89.3% and 93.3%, respectively, while those of rSjTPx-1 were 71.4% and 66.7%, respectively. In addition, a higher Kappa value of 0.82 calculated between rSmekTPx-1 antigen ELISA and Kato-Katz confirmed better agreement than between rSjTPx-1 antigen ELISA and Kato-Katz (Kappa value 0.38). These results suggest that ELISA with rSmekTPx-1 antigen can be a potential diagnostic method for detecting active human S. mekongi infection.

Discovery of Schistosoma mekongi circulating proteins and antigens in infected mouse sera

Schistosomiasis is a neglected tropical disease caused by an infection of the parasitic flatworms schistosomes. Schistosoma mekongi is a restricted Schistosoma species found near the Mekong River, mainly in southern Laos and northern Cambodia. Because there is no vaccine or effective early diagnosis available for S. mekongi, additional biomarkers are required. In this study, serum biomarkers associated with S. mekongi-infected mice were identified at 14-, 28-, 42-, and 56-days post-infection. Circulating proteins and antigens of S. mekongi in mouse sera were analyzed using mass spectrometry-based proteomics. Serine protease inhibitors and macrophage erythroblast attacher were down-regulated in mouse sera at all infection timepoints. In addition, 54 circulating proteins and 55 antigens of S. mekongi were identified. Notable circulating proteins included kyphoscoliosis peptidase and putative tuberin, and antigens were detected at all four infection timepoints, particularly in the early stages (12 days). The putative tuberin sequence of S. mekongi was highly similar to homologs found in other members of the genus Schistosoma and less similar to human and murine sequences. Our study provided the identity of promising diagnostic biomarkers that could be applicable in early schistosomiasis diagnosis and vaccine development.

Proteomics Investigations of Potential Protein Biomarkers in Sera of Rabbits Infected With Schistosoma japonicum

Schistosomiasis is a chronic parasitic disease that continues to be a pressing public health problem in many developing countries. The primary pathological damage from the disease is granuloma and fibrosis caused by egg aggregation, and early treatment can effectively prevent the occurrence of liver fibrosis. Therefore, it is very important to identify biomarkers that can be used for early diagnosis of Schistosoma japonicum infection. In this study, a label-free proteomics method was performed to observe the alteration of proteins before infection, 1 and 6 weeks after infection, and 5 and 7 weeks after treatment. A total of 10 proteins derived from S. japonicum and 242 host-derived proteins were identified and quantified as significantly changed. Temporal analysis was carried out to further analyze potential biomarkers with coherent changes during infection and treatment. The results revealed biological process changes in serum proteins compared to infection and treatment groups, which implicated receptor-mediated endocytosis, inflammatory response, and acute-phase response such as mannan-binding lectin serine peptidase 1, immunoglobulin, and collagen. These findings offer guidance for the in-depth analysis of potential biomarkers of schistosomiasis, host protein, and early diagnosis of S. japonicum and its pathogenesis. Data are available via ProteomeXchange with identifier PXD029635.

Reviews and advances in diagnostic research on Schistosoma japonicum

Schistosomiasis is an acute and chronic parasitic disease caused by blood flukes (trematode worms) of the genus Schistosoma. Schistosoma japonicum (S. japonicum) infection has decreased significantly in prevalence and intensity of infection in China. However, this disease still remains a serious public health problem in some endemic areas of the Philippines and Indonesia. Thus, more accurate and sensitive methods are much needed for further control of this disease. Here, we review the research progress in techniques for the diagnosis of S. japonicum infection.

The IL-33/ST2 pathway is not essential to Th2 stimulation but is key for modulation and survival during chronic infection with Schistosoma mansoni in mice

Morbidity during chronic schistosomiasis has been associated with the induction and modulation of type-2 granulomatous inflammatory response induced by antigens secreted by the eggs, which become trapped in capillary venules of the host tissues, especially in the liver and intestines. IL-33, an alarmin released after cell damage, binds to its ST2 (suppressor of tumorigenicity 2) receptor, expressed in an variety of immune cells, including ILC2 and macrophages, and stimulates the early production of IL-5 and IL-13, which leads to eosinophil infiltration and activation of a Th2 response. However, the role of IL-33/ST2 activation on Schistosoma-induced granuloma formation and modulation is mostly unknown. In the current work, we comparatively evaluated the immune response and granuloma formation in wild-type BALB/c (WT) and BALB/c mice genetically deficient in the IL-33 receptor (ST2^-/-) experimentally infected with Schistosoma mansoni. Mice were infected with 25 or 50 S. mansoni cercariae and followed for up to 14 weeks to assess mortality. Mice from each experimental group were comparatively evaluated for parasite burden, liver immune response, and granuloma appearance during acute and chronic schistosomiasis. Our data showed that the number of circulating worms and eggs retained in the liver and eliminated in the feces was similar in WT and ST2^-/- infected mice, but infected ST2^-/- mice presented an enhanced rate of mortality. Interestingly, the production of type-2 cytokines by soluble egg antigens (SEA)-stimulated spleen cells, the serum concentrations of IL-5 and Immunoglobulin (Ig)-E, and the level of parasite-reactive IgG1 were similar in infected mice of both experimental groups. The concentrations of IL-4, IL-5, IL-13, and IFN-γ in liver homogenate of infected mice also did not differ between the strains at acute schistosomiasis, but there was a significant increase in IL-17 levels in ST2^-/- infected mice at this phase. On the other hand, IL-4, IL-13, IL-10, IL-17, and IFN-γ concentrations were reduced and the ratios of IL-4/IFN-γ and IL-17/IFN-γ were higher in liver homogenate of chronically infected ST2^-/- mice, suggesting unbalanced Th2 and Th17 responses. Moreover, liver granulomas of ST2^-/- mice were larger and disorganized, showing an intense cellular infiltrate, rich in eosinophils and neutrophils. Our results suggest that the absence of the IL-33/ST2 pathway is not essential for the Schistosoma-induced Th2 response, but is necessary to prevent host mortality by modulating granuloma-mediated pathology.

Proteomic Analysis of Schistosoma mansoni Tegumental Proteins

The tegument (outer surface) of Schistosoma mansoni and other trematodes is in intimate contact with the host and plays an important role in host-parasite interactions. It is a complex structure that contains hundreds of proteins implicated in a variety of functions, although, so far, only a few proteins have been well characterized. Indeed, a few of these proteins have been shown to be effective vaccine and diagnostic candidates against S. mansoni and other schistosomes, and so the proteomic characterization of tegumental molecules could open new avenues for the development of novel control and surveillance strategies to combat schistosomiasis. Here, we describe the step by step isolation of tegumental proteins from the different tegument compartments using a biotinylation approach, as well as the materials and reagents needed.

Recent advances in Schistosoma mekongi ecology, transcriptomics and proteomics of relevance to snail control

Mekong schistosomiasis caused by Schistosoma mekongi is a public health problem that occurs along the border between southern Laos and northern Cambodia. Given its restricted distribution and low prevalence, eventual eradication via an effective control program can be expected to be successful. To achieve this goal detailed knowledge of its basic biology, molecular biology, biochemistry, and pathology is urgently required. In this regard, recent studies on transcriptome analysis of adult male and female S. mekongi worms, and proteome analysis of developmental stages have been reported and are discussed here. The biology, habitat, and distribution of the snail intermediate host Neotricula aperta, which are factors in disease transmission, are discussed in this review. These have initiated renewed interest in S. mekongi research and contributed promising data that will be utilized in the generation of effective control and prevention strategies.

An ELISA based on soluble egg antigens for the serodiagnosis of animal schistosomiasis turkestanica

Background

The existing diagnostic techniques for detecting schistosomiasis turkestanica, such as aetiological assays, identify infection by parasitic worms via the incubation of miracidia from faeces or observing eggs under microscopy. However, they are limited in the diagnosis of low-grade and prepatent infections, which lead to a high misdetection rates. Therefore, a new method for parasite diagnosis with increased sensitivity is urgently needed.

Methods

Goats in Nimu County (Tibet, China) infected with Schistosoma turkestanicum in an epidemic area were selected according positivity for the infection by faecal examination. Adult worms were collected, eggs were extracted by the sodium hydroxide (NaOH) erosion method, and soluble worm antigen preparation (SWAP) and soluble egg antigen (SEA) were isolated. The best coating concentration of the antigens and the best degree of dilution for serum were determined by square array experiments, and the optimal blocking solution and serum diluents were selected. The specificity, sensitivity and crossover of the ELISA method were determined using 48 samples of goat sera positive for S. turkestanicum, 100 samples of goat sera negative for S. turkestanicum, and 54 samples of buffalo sera positive for S. japonicum. Serological assays were established with samples from goats naturally grazed in a rural area of Nimu County, Tibet Province, by using the indirect ELISA method for the diagnosis of schistosomiasis, and faeces were collected for miracidia hatching. The sensitivity of the two detection methods was compared.

Results

Eggs of S. turkestanicum were distributed in the host duodenum and small intestine. Eggs in the host intestinal wall were extracted by the NaOH erosion method, which provided intact eggs with reduced impurities. The testing results obtained by isolating SEA were more stable than those obtained by using SWAP and less affected by the coating concentration and serum dilution. Additionally, the value of positive serum/negative (P/N) serum for SEA was much higher than that for SWAP. The optimal coating concentration of SEA was 0.5 μg/ml, and the optimal serum dilution was 1:100. The specificity and sensitivity of the indirect ELISA based on SEA (S. turkestanicum) were both 100%, and no cross-reactivity was found with schistosomiasis japonica. An epidemiological survey of goats in naturally infected areas showed that the prevalence rate of schistosomiasis turkestanica was 93%, and the infection rate increased with the ages of the goats.

Conclusion

We aimed to develop a sensitive method to utilize in the mass field screening of livestock. As a diagnostic antigen, SEA (S. turkestanicum) was more suitable for serological testing than SWAP (S. turkestanicum). The indirect ELISA using SEA (S. turkestanicum) exhibited good sensitivity, specificity and no cross-reactivity with schistosomiasis japonica. The degree of infectivity and prevalence of S. turkestanicum infection in endemic areas are serious and should be a focus of concern among local departments.

Serological proteomic screening and evaluation of a recombinant egg antigen for the diagnosis of low-intensity Schistosoma mansoni infections in endemic area in Brazil

Background

Despite decades of use of control programs, schistosomiasis remains a global public health problem. To further reduce prevalence and intensity of infection, or to achieve the goal of elimination in low-endemic areas, there needs to be better diagnostic tools to detect low-intensity infections in low-endemic areas in Brazil. The rationale for development of new diagnostic tools is that the current standard test Kato-Katz (KK) is not sensitive enough to detect low-intensity infections in low-endemic areas. In order to develop new diagnostic tools, we employed a proteomics approach to identify biomarkers associated with schistosome-specific immune responses in hopes of developing sensitive and specific new methods for immunodiagnosis.

Methods and findings

Immunoproteomic analyses were performed on egg extracts of Schistosoma mansoni using pooled sera from infected or non-infected individuals from a low-endemic area of Brazil. Cross reactivity with other soil-transmitted helminths (STH) was determined using pooled sera from individuals uniquely infected with different helminths. Using this approach, we identified 23 targets recognized by schistosome acute and chronic sera samples. To identify immunoreactive targets that were likely glycan epitopes, we compared these targets to the immunoreactivity of spots treated with sodium metaperiodate oxidation of egg extract. This treatment yielded 12/23 spots maintaining immunoreactivity, suggesting that they were protein epitopes. From these 12 spots, 11 spots cross-reacted with sera from individuals infected with other STH and 10 spots cross-reacted with the negative control group. Spot number 5 was exclusively immunoreactive with sera from S. mansoni-infected groups in native and deglycosylated conditions and corresponds to Major Egg Antigen (MEA). We expressed MEA as a recombinant protein and showed a similar recognition pattern to that of the native protein via western blot. IgG-ELISA gave a sensitivity of 87.10% and specificity of 89.09% represented by area under the ROC curve of 0.95. IgG-ELISA performed better than the conventional KK (2 slides), identifying 56/64 cases harboring 1–10 eggs per gram of feces that were undiagnosed by KK parasitological technique.

Conclusions

The serological proteome approach was able to identify a new diagnostic candidate. The recombinant egg antigen provided good performance in IgG-ELISA to detect individuals with extreme low-intensity infections (1 egg per gram of feces). Therefore, the IgG-ELISA using this newly identified recombinant MEA can be a useful tool combined with other techniques in low-endemic areas to determine the true prevalence of schistosome infection that is underestimated by the KK method. Further, to overcome the complexity of ELISA in the field, a second generation of antibody-based rapid diagnostic tests (RDT) can be developed.

Schistosomiasis remains a serious global public health problem. Detecting parasite eggs in patient stool samples using the KK method is the standard diagnostic recommended by the World Health Organization (WHO) for infection by S. mansoni. As a result of intensive control strategies, many previously high-endemic areas are now considered low-endemic areas and the KK method does not function well in low-endemic areas and therefore cannot be considered the gold standard. Thus, a new emphasis on strategies to accurately diagnose low-intensity infections was outlined in a plan from the WHO focusing on elimination of disease as a public health problem. Successful diagnoses and treatment of infected individuals may result in eradication of low-burden transmitters and consequently contribute to interruption of disease transmission. In this regard, immunological techniques have proven to be more sensitive and promising for identifying low-intensity infections where KK may be negative. The identification of antigens is the initial step for developing new immunodiagnostic assays. In this study, we used sets of pooled human sera samples from controls with acute and chronic infections to identify new target antigens via proteomic screening. Using these approaches, we initially identified 12 different egg proteins in S. mansoni-infected individuals (acute and chronic phase). A single antigen, identified as MEA, was shown to be highly specific as this antigen was not recognized by sera from negative patients or patients infected with other STH. The recombinant MEA protein functioned in an ELISA as a highly sensitive and specific antigen to detect patient IgG-antibodies. Recombinant MEA performed significantly better to detect low-intensity infections (1 egg per gram of feces) than the KK method using 2 slides. Therefore, we were able to use a proteomic screening approach to identify a potential new candidate antigen for development of far more sensitive diagnostic assays. Further diagnostic assays employing the MEA could be useful tools on their own or in combination with other methods for diagnosis of schistosome infection in populations living in extreme low-intensity endemic areas of Brazil.

A perspective for improving the sensitivity of detection: The application of multi-epitope recombinant antigen in serological analysis of buffalo schistosomiasis

The sensitivity and specificity are two crucial aspects of addressing the efficacy of diagnostic antigens. Achilles' heel of low sensitivity rate exists in current diagnostic recombinant antigens for schistosomiasis detection. This study focused on the diagnosis of water buffalo schistosomiasis japonica and a perspective of improving recombinant antigens' sensitivity was assessed using archived 220 water buffalo sera (114 positive sera, 92 negative sera and 14 Paramphistomum-infected sera) and the method of enzyme-linked immunosorbent assay (ELISA). The subjects included two trivalent recombinant proteins, one bivalent antigen and two single-molecular antigens. The crude antigen SEA (soluble egg antigen) was employed as reference antigen. The highest sensitivity rate in the five recombinant antigens assigned to the trivalent multi-epitope antigen PA4 (95.61%, 109/114), no significant difference with SEA (100%, 114/114, p = .836), and showing remarkable differences with the two single-molecular antigens (p < 0.01). In term of specificity, two trivalent multi-epitope antigens PA4 (97.83%, 90/92), PA5 (100%, 92/92) and the bivalent antigen PA3 (98.91%, 91/92) had few differences with one monovalent antigens PA1 (97.83%, 90/92, p = .304/0.103/0.640), significant differences with another monovalent antigens PA2 (92.39%, 85/92, p < 0.01) and SEA (82.61%, 76/92, p < 0.01). Additional, all the recombinant antigens had low cross-reactivity (7.14%, 1/14, 0% for PA5) with serum samples of paramphistomiasis, contrast with that of SEA (50%, 7/14, p < 0.01). The results indicated that multi-epitope antigens have the possibility to improve diagnostic sensitivity and the trivalent multi-epitope antigen PA4 possesses greater likelihood to be a diagnostic antigen for water buffalo schistosomiasis.

Identification and characterization of the zinc finger protein SjZF in Schistosoma japonicum

Schistosomiasis represents one of the most prevalent parasitic infections affecting over 249 million people worldwide. The pathological damage is mainly caused by the eggs laid by female schistosomes. Zinc finger proteins (ZFPs) usually play critical roles in many biological functions. In this study, we cloned, identified and characterized the zinc finger protein SjZF of Schistosoma japonicum. SjZF ortholog proteins were also identified in S. mansoni, S. haematobium, Opisthorchis viverrini and O. sinensis. Fluorescence localization showed that SjZF was particularly expressed in the worm gut of both genders and the vitelline glands of females. In vitro RNAi assay indicated that decreased expression of SjZF could affect the survival rate of adult worms. The immune protection assay indicated that rSjZF did partially protect mice with 54.8% reduction in the worm burden and 34.1% reduction in the liver eggs. Taken in concert, our preliminary results suggest that SjZF may be a potential vaccine candidate for schistosomiasis and may further provide evidence for a possible role of SjZF in the development of schistosomes.

A Parallel Comparison of Antigen Candidates for Development of an Optimized Serological Diagnosis of Schistosomiasis Japonica in the Philippines

Schistosoma japonicum is stubbornly persistent in China and the Philippines. Fast and accurate diagnostic tools are required to monitor effective control measures against schistosomiasis japonica. Promising antigen candidates for the serological diagnosis of schistosomiasis japonica have generally been identified from the Chinese strain of S. japonicum. However, the Chinese (SjC) and Philippine (SjP) strains of S. japonicum express a number of clear phenotypic differences, including aspects of host immune responses. This feature thereby emphasized the requirement to determine whether antigens identified as having diagnostic value for SjC infection are also suitable for the diagnosis of SjP infection. In the current study, 10 antigens were selected for comparison of diagnostic performance of the SjP infection using ELISA. On testing of sera from 180 subjects in the Philippines, SjSAP4 exhibited the best diagnostic performance with 94.03% sensitivity and 98.33% specificity using an optimized serum dilution. In another large scale testing with 412 serum samples, a combination (SjSAP4 + Sj23-LHD (large hydrophilic domain)) provided the best diagnostic outcome with 87.04% sensitivity and 96.67% specificity. This combination could be used in future for serological diagnosis of schistosomiasis in the Philippines, thereby representing an important component for monitoring integrated control measures.

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Sj23-LHD was the most promising antigen candidate for early diagnosis of schistosomiasis japonica in a murine model.

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SjSAP4 + Sj23-LHD had the highest diagnostic value when probed with sera from a human cohort with low infection intensity.

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We have developed a novel diagnostic tool that can aid in the integrated control of schistosomiasis in the Philippines.

Schistosomiasis japonica remains a major public health concern in China and the Philippines. Development of accurate and affordable diagnostic tools is a necessity for the control and elimination of schistosomiasis. The differences in the mammalian host immunological responses to Chinese (SjC) and Philippine (SjP) strains of S. japonicum necessitated validation of proven SjC serological markers for application in the diagnosis of SjP infections. Ten antigens were selected for comparison, in ELISA, for their potential of the diagnosis of SjP infection. The results provide the basis for developing an affordable and easy-to-operate tool for the diagnosis of schistosomiasis in the Philippines.

IgM and IgG responses in Schistosoma mansoni-infected mice using egg and worm antigens: Does response vary with parasitic burden and phase of infection?

Schistosomiasis is a chronic parasitic disease caused by trematodes of the genus Schistosoma, endemic in tropical and subtropical regions. The hepatic pathology of this parasitic disease could develop complications, such as fibrosis and cirrhosis, which can be fatal. The Venezuelan endemic area is considered as one of low transmission, which complicates the detection of infected individuals and signals the importance of improving the sensitivity of immunodiagnostic methods. Using ELISA, an evaluation was conducted of IgM and IgG responses to soluble antigens of eggs and female worms (SEA and SFWA) and excretion-secretion products of eggs and female worms (ESPE and ESPAW) in infected Balb/c mice with different parasitic burden and infection times. A high positivity rate by IgM detection was observed for all antigen preparations in 7-week infections (100% by SEA, SFWA, ESPE, and ESPWA in high parasitic burden) as well as a reduction of this immunoglobulin in chronic infection. Positivity rate for IgG detection was higher in 20-week infections (100% by ESPE in low burden, 100% by SEA and ESPE in medium burden, and 100% by ESPE and ESPAW in high burden conditions). The potential use of combined or unique antigenic preparations associated with IgM or IgG for detection of active infection, regardless the parasitic burden, was demonstrated. Differences between immunoglobulin responses show its application for phase-specific diagnosis.

A candidate recombinant antigen for diagnosis of schistosomiasis japonica in domestic animals

Domestic animals infected with Schistosoma japonicum are a major source of infection and play an important role in transmission to humans. A key strategy for the elimination of schistosomiasis is to control the sources of infection. In the present study, we identified a candidate diagnostic antigen-encoding gene, SjMRP1, the putative multidrug resistance protein 1 gene, by screening a cDNA phage display library from 44-day-old S. japonicum worms using IgGs from goat, cattle, and buffalo infected with S. japonicum. We cloned and expressed the fragment of SjMRP1 and subsequently evaluated the diagnostic potential of the recombinant protein rSjMRP1. In the enzyme-linked immunosorbent assay of rSjMRP1 (rSjMRP1-ELISA), the sensitivity in goat, cattle, and buffalo was 95.6% (86/90), 100% (22/22), and 90% (81/90), respectively, and the specificity was 100% (30/30) in goat and cattle and 96.67% (29/30) in buffalo. These results were not significantly different from soluble egg antigen (SEA)-ELISA results. Notably, rSjMRP1-ELISA has no cross reaction with Haemonchus contortus, a most common nematode seen in goat and bovine in China, in 13 infected goats, and with Orientobilhazia turkestanica, which is genetically under Schistosoma, in 36 infected goats; whereas SEA-ELISA showed false positive rate of 15.38% and 83.33% in the two respective animal groups. The results obtained here suggest that rSjMRP1 may be used for diagnosis of S. japonicum infection of domestic animals.

A novel ex vivo immunoproteomic approach characterising Fasciola hepatica tegumental antigens identified using immune antibody from resistant sheep

A more thorough understanding of the immunological interactions between Fasciola spp. and their hosts is required if we are to develop new immunotherapies to control fasciolosis. Deeper knowledge of the antigens that are the target of the acquired immune responses of definitive hosts against both Fasciola hepatica and Fasciola gigantica will potentially identify candidate vaccine antigens. Indonesian Thin Tail sheep express a high level of acquired immunity to infection by F. gigantica within 4weeks of infection and antibodies in Indonesian Thin Tail sera can promote antibody-dependent cell-mediated cytotoxicity against the surface tegument of juvenile F. gigantica in vitro. Given the high protein sequence similarity between F. hepatica and F. gigantica, we hypothesised that antibody from F. gigantica-infected sheep could be used to identify the orthologous proteins in the tegument of F. hepatica. Purified IgG from the sera of F. gigantica-infected Indonesian Thin Tail sheep collected pre-infection and 4weeks p.i. were incubated with live adult F. hepatica ex vivo and the immunosloughate (immunoprecipitate) formed was isolated and analysed via liquid chromatography-electrospray ionisation-tandem mass spectrometry to identify proteins involved in the immune response. A total of 38 proteins were identified at a significantly higher abundance in the immunosloughate using week 4 IgG, including eight predicted membrane proteins, 20 secreted proteins, nine proteins predicted to be associated with either the lysosomes, the cytoplasm or the cytoskeleton and one protein with an unknown cellular localization. Three of the membrane proteins are transporters including a multidrug resistance protein, an amino acid permease and a glucose transporter. Interestingly, a total of 21 of the 38 proteins matched with proteins recently reported to be associated with the proposed small exosome-like extracellular vesicles of adult F. hepatica, suggesting that the Indonesian Thin Tail week 4 IgG is either recognising individual proteins released from extracellular vesicles or is immunoprecipitating intact exosome-like extracellular vesicles. Five extracellular vesicle membrane proteins were identified including two proteins predicted to be associated with vesicle transport/ exocytosis (VPS4, vacuolar protein sorting-associated protein 4b and the Niemann-Pick C1 protein). RNAseq analysis of the developmental transcription of the 38 immunosloughate proteins showed that the sequences are expressed over a wide abundance range with 21/38 transcripts expressed at a relatively high level from metacercariae to the adult life cycle stage. A notable feature of the immunosloughates was the absence of cytosolic proteins which have been reported to be secreted markers for damage to adult flukes incubated in vitro, suggesting that the proteins observed are not inadvertent contaminants leaking from damaged flukes ex vivo. The identification of tegument protein antigens shared between F. gigantica and F. hepatica is beneficial in terms of the possible development of a dual purpose vaccine effective against both fluke species.

Evaluation of recombinant multi-epitope proteins for diagnosis of goat schistosomiasis by enzyme-linked immunosorbent assay

Background

Schistosomiasis is a huge threat to human and animal health. Apart from bovines, goats play an important role in the transmission of schistosomiasis in some endemic areas of China. An accessible, quality-assured goat schistosomiasis diagnostic technique is needed. Recently, our laboratory identified two recombinant diagnostic antigens, SjPGM and SjRAD23 via an immuno-proteomic method. The application of these two recombinant antigens to develop a higher sensitivity and specificity technique for the sheep schistosomiasis diagnosis is urgently needed.

Methods

Epitopes of SjPGM and SjRAD23 were predicted and three polypeptides, two from SjRAD23 and one from SjPGM, were selected. Recombinant plasmids containing two to three DNA sequences encoding predicted polypeptides or large hydrophilic region of Sj23 (LHD-Sj23) were constructed and expressed. Eight recombinant schistosome antigens including four multi-epitope proteins and four recombinant single-molecule antigens as well as SEA, were assessed by ELISA in 91 sera from schistosome-infected goats, 44 sera from non-infected goats, 37 sera from Orientobilharzia-infected goats, and 12 from Haemonchus contortus-infected goats.

Results

ELISA tests showed that three multi-epitope proteins had higher sensitivity than the four single-molecule antigens (rSjRAD23, rSjPGM, rBSjRAD23-1, rBSj23) and the multi-epitope protein rBSjPGM-BSjRAD23-1-BSj23 had the highest sensitivity (97.8 %, 89/91) and maintained good specificity (100 %, 44/44) as well as low cross-reactivity with haemonchosis (8.33 %, 3/12) and orientobilharziasis (13.51 %, 5/37) in the diagnosis of goat schistosomiasis. In contrast, when SEA was applied as a diagnosis antigen, it had 100 % (91/91) sensitivity, 75 % (33/44) specificity, 25 and 83.78 % cross-reactivity with haemonchosis (3/12) and orientobilharziasis (31/37), respectively.

Conclusions

The application of recombinant multi-epitope proteins may increase the sensitivity of diagnosis technique and retain high specificity of single-molecule antigens for schistosomiasis, and the recombinant antigen rBSjPGM-BSjRAD23-1-BSj23 has the potential to be used as a diagnosis antigen for goat schistosomiasis.

iTRAQ-based comparative proteomic analysis of excretory-secretory proteins of schistosomula and adult worms of Schistosoma japonicum

Schistosomiasis remains a serious public health problem with 200 million people infected and 779 million people at risk worldwide. The schistosomulum and adult worm are two stages of the complex lifecycle of Schistosoma japonicum and excretory/secretory proteins (ESPs) play a major role in host-parasite interactions. In this study, iTRAQ-coupled LC-MS/MS was used to investigate the proteome of ESPs obtained from schistosomula and adult worms of S. japonicum, and 298 differential ESPs were identified. Bioinformatics analysis of differential ESPs in the two developmental stages showed that 161 ESPs upregulated in schistosomula were associated with stress responses, carbohydrate metabolism and protein degradation, whereas ESPs upregulated in adult worms were mainly related to immunoregulation and purine metabolism. Recombinant heat shock protein 70 (HSP70) and thioredoxin peroxidase (TPx), two differential proteins identified in this study, were expressed. Further studies showed that rSjHSP70 and rSjTPx stimulated macrophages expressing high levels of the anti-inflammatory factors TGF-β, IL-10 and Arg-1, and suppressed the expression of the pro-inflammatory cytokines TNF-α, IL-1β, IL-6 and iNOS in LPS-induced macrophages. This study provides new insights into the survival and development of schistosomes in the final host and helps identify vaccine candidates or new diagnostic reagents for schistosomiasis.

New Anti-Schistosoma Approaches in The People's Republic of China: Development of Diagnostics, Vaccines and Other New Techniques Belonging to the 'Omics' Group

A new national schistosomiasis elimination programme will be implemented for the period 2016-20. To support this approach, we have performed a systematic review to assess anti-schistosome approaches in The People's Republic of China and defined research priorities for the coming years. A systematic search was conducted for articles published from January 2000 to March 2015 in international journals. Totally 410 references were published in English between 2000 and 2015 related to schistosomiasis after unrelated references and reviews or comments were further excluded. A set of research priorities has been identified for the near future that would improve the progress toward schistosomiasis elimination in The People's Republic of China. In particular, there is a lack of sensitive and specific tests for the detection of schistosomiasis cases with low parasite burdens, as well as an effective vaccine against schistosomiasis, and there is a need for surveillance tools that can evaluate the epidemic status for guiding the elimination strategy. Hence, we think that schistosomiasis control and elimination will be improved in The People's Republic of China through development of new tools.