Diagnostic value of non-invasive bio-markers for stage-specific diagnosis of hepatic fibrosis in patients with advanced schistosomiasis japonica

Hepatic fibrosis caused by schistosome infection can be fatal. Its management depends on the degree of fibrosis present. To assess the diagnostic value of bio-markers in patients with advanced schistosomiasis japonica at different stages of disease progression, 84 advanced schistosomiasis japonica patients and nine controls were recruited in The People's Republic of China. Fibrosis was histologically assessed in wedge liver biopsies using the Chinese criteria for fibrosis (F) Stages. Seven selected hepatic fibrosis bio-markers were assessed and compared between the groups. The method of area under receiver operating characteristic curves (AUROCs) was used as a measurement of diagnostic efficacy. Our results showed that routine laboratory test results were normal for the controls but were significantly elevated or decreased in patients with fibrosis. While serum hyaluronic acid (HA) and matrix metalloproteinase (TIMP)-1 levels were shown to be elevated in patient groups compared with controls, the levels of platelet derived growth factor (PDGF)-BB were markedly lower. To distinguish F≥2 from no fibrosis or mild fibrosis, HA gave a high AUROC of 0.938 (95% confidence interval (CI), 0.886-0.990). Combining the aspartate aminotransferase (AST) to platelet ratio index (APRI) and HA/100 showed an AUROC of 0.958 (95% CI, 0.914-1.000). APRI in combination with TIMP-1/100 provided an AUROC of 0.873 (95% CI, 0.805-0.942) for the diagnosis of fibrosis stages greater than 2. We conclude that AST and APRI levels were reliable and sensitive markers for differentiating significant hepatic fibrosis in patients with advanced schistosomiasis japonica. HA and TIMP-1 show potential as additional markers for the diagnosis of fibrosis and cirrhosis in advanced schistosomiasis patients.     

Human bancroftian filariasis: immunological markers of morbidity and infection

Induction of host cytokines plays a critical role in infection as well as disease in human filariasis. Measurements of such molecules in plasma could be used as windows of markers both for understanding the pathogenesis of the disease and for identifying markers of morbidity. Eight inflammatory and non-inflammatory host molecules in circulation were quantified in 207 subjects in filariasis endemic area of Orissa, India. IL-6, IL-8, IL-10, TNF-alpha, TNFR-I, TNFR-II, LBP and sICAM-1 were quantified by immunoassays and were analyzed by multivariate exploratory data analysis methods followed by multivariate analysis of variance. Raised levels of IL-6 and IL-8 emerged as markers of acute as well as chronic disease, while increased TNF-alpha was a feature found only in acute filariasis. Decreased sICAM-1 was a feature found only in asymptomatic subjects with filarial infection. There was a dichotomy in plasma levels of two TNF receptors between infected subjects and patients with filarial disease. Since plasma levels of these cytokines are often determined by host genetics, studies on cytokine genetic polymorphisms could offer new insights into the relationship between infection and disease in human lymphatic filariasis.     

CD16 Expression on Monocytes in Healthy Individuals but Not Schistosome-Infected Patients Is Positively Associated with Levels of Parasite-Specific IgG and IgG1

Human IgG1 antibody responses are associated with protection against Schistosoma haematobium infection and are now a target for schistosome vaccine development. This study aimed to investigate the relationship between total IgG and the IgG subclasses and the monocyte IgG receptor, known as FcγRIIIa or CD16, in schistosome exposed people. Systemic levels of schistosome-specific anti-adult worm total IgG and IgG subclass titres were measured by ELISA in 100 individuals from an S. haematobium endemic area in Zimbabwe and, using parametric statistical methods and regression analysis, related to the levels of CD16 expression on individuals'' circulating monocytes, determined via flow cytometry. Monocyte CD16 expression rose with parasite-specific total IgG and IgG1 in healthy participants, but not in schistosome infected patients. Similar to parasite-specific IgG and IgG1, CD16 expression in healthy individuals is associated with protection against schistosome infection. This relationship indicates a mechanistic link between the innate and adaptive immune responses to helminth infection in protection against infection. Further understanding the elements of a protective immune response in schistosomiasis may aid in efforts to develop a protective vaccine against this disease.     

Anti-malaria humoral responses in children exposed to Plasmodium falciparum and Schistosoma haematobium

Antibody responses directed against the Plasmodium falciparum antigens, total extract, anti-merozoite surface protein-3 (MSP3b) and glutamate-rich protein (Glurp-R0) were studied in 42 children exposed to both Schistosoma haematobium and P. falciparum infections. The association between levels of the anti-malaria IgG subclasses and IgM with host age, sex, schistosome infection intensity and schistosome specific antibodies was studied before chemotherapeutic treatment of schistosome infections. This showed a significant negative association between schistosome infection intensity and levels of IgG1, IgG3, and IgG4 directed against malaria total extract antigen, and a positive association between levels of anti-schistosome soluble egg antigen IgG2, IgG3, and IgG4 and levels of the same subclasses directed against malaria total extract antigens. The effect of treating schistosome infections with praziquantel on malaria specific responses was also studied. This treatment resulted in increases in significant IgG4 levels against MSP3b and IgM against Glurp R0. Treatment also resulted in a significant decrease in IgG4 levels against Glurp R0. Host age, sex or pre-treatment infection intensity was not associated with the magnitude of change in the two IgG4 responses while males showed a significantly higher increase in levels of IgM. The results suggest cross reactivity between schistosome and malaria antigens in this population.     

Chronic Schistosoma japonicum Infection Reduces Immune Response to Vaccine against Hepatitis B in Mice

Background

Hepatitis B and schistosomiasis are most prevalent in Africa and Asia, and co-infections of both are frequent in these areas. The immunomodulation reported to be induced by schistosome infections might restrict immune control of hepatitis B virus (HBV) leading to more severe viral infection. Vaccination is the most effective measure to control and prevent HBV infection, but there is evidence for a reduced immune response to the vaccine in patients with chronic schistosomiasis japonica.

Methodology/Principal Findings

In this paper, we demonstrate in a mouse model that a chronic Schistosoma japonicum infection can inhibit the immune response to hepatitis B vaccine (HBV vaccine) and lead to lower production of anti-HBs antibodies, interferon-γ (IFN-γ) and interleukin-2 (IL-2). After deworming with Praziquantel (PZQ), the level of anti-HBs antibodies gradually increased and the Th2-biased profile slowly tapered. At 16 weeks after deworming, the levels of anti-HBs antibodies and Th1/Th2 cytokines returned to the normal levels.

Conclusions/Significance

The results suggest that the preexisting Th2-dominated immune profile in the host infected with the parasite may down–regulate levels of anti-HBs antibodies and Th1 cytokines. To improve the efficacy of HBV vaccination in schistosome infected humans it may be valuable to treat them with praziquantel (PZQ) some time prior to HBV vaccination.     

Detection of IgG binding to Schistosoma mansoni recombinant protein RP26 is a sensitive and specific method for acute schistosomiasis diagnosis

We recently described the first recombinant Schistosoma mansoni protein RP26, which was capable of acute infection diagnosis. The aim of the present work was to further characterize the RP26 diagnostic properties in immunoblot and enzyme-linked immunosorbent (ELISA) assays. Testing sera from uninfected donors and sera from patients with acute or chronic Schistosoma infection by Western blot immunoassay revealed 100% specificity and 100% sensitivity for acute infection identification. Sera from uninfected, acute, and chronic schistosomiasis were also probed for IgG, IgG4, IgA, and IgM reactivity to RP26 plus soluble egg antigens (SEA) in ELISA. The mean IgG reactivity to RP26 by sera from acute schistosomiasis patients was significantly higher than the chronic ones. The IgG4, IgA, and IgM reactivities to RP26 were low and similar in both infected groups. The mean IgA and IgM reactivities to SEA were significantly higher in the group of acute compared to chronic group, whereas mean IgG4 reactivity was higher in chronic group. To estimate the specificity of Schistosoma infection diagnosis sera from patients infected with other different parasites were tested to detect IgG reactivity to RP26 and IgA and IgM reactivity to SEA. For IgA against SEA detection, 72% of sera were positive and 48% of sera were positive for IgM detection. Based on these results we can suggest that detection of sera IgG binding to RP26 is a sensitive and specific method for acute schistosomiasis diagnosis. Therefore, RP26 is a candidate for immunodiagnostic kit development.     

Tolerization of mice to Schistosoma mansoni egg antigens causes elevated type 1 and diminished type 2 cytokine responses and increased mortality in acute infection

The granuloma that surrounds the Schistosoma mansoni egg is the cause of pathology in murine schistosomiasis, and its formation is driven by egg Ag-stimulated type 1 and type 2 cytokines. To determine the role of egg-driven immune responses during schistosome infection we rendered CBA/Ca mice unresponsive to schistosome eggs by combined cyclophosphamide treatment and thymectomy. In the early acute stages of schistosome infection, egg-tolerized mice suffered high mortalities. Granuloma size and deposition of collagen in the liver were significantly reduced in egg-tolerized mice. Similarly, limited granuloma responses were detected in the intestines of these mice, and this was associated with a >90% reduction in egg excretion. Histologically, egg-tolerized mice had exacerbated hepatocyte damage, with extensive microvesicular steatosis. Elevated plasma transaminase levels confirmed the damage to hepatocytes. Infected egg-tolerized mice had impaired proliferation responses to egg Ag but intact responses to worm Ag. Tolerized mice had diminished Ab responses to egg Ag and had a type 1 cytokine isotype pattern to worm Ag, with elevated IgG2a and diminished IgG1 and IgE. Egg-tolerized mice failed to down-regulate type 1 cytokines that are normally elicited during early schistosome infection. Hepatic granuloma cells from egg-tolerized mice were also type 1 cytokine dominated, with elevated frequencies of Tc1/Th1 and reduced Tc2/Th2 cells. This study demonstrates that mice tolerized to schistosome eggs have elevated type 1 cytokine responses with diminished type 2 responses and reduced anti-egg Ab during schistosome infection, and these effects are detrimental to the host.     

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.     

Imaging diagnosis of schistosomiasis japonica--the use in Japan and application for field study in the present endemic area

For detecting lesions-related schistosomiasis japonica, X-rays, scintillation scanning, ultrasonography (US), computed tomography (CT), magnetic resonance (MR) and endoscopic examinations with biopsies have been used in Japan. Liver fibrosis and calcified changes are detected by US and CT. Most of the lesions that are detected by endoscopic examinations are due to deposited ova of Schistosoma japonicum. Portal hypertension is detected by US, CT and gastroscopic examination. Because schistosome infection decreased rapidly in Japan, most of the studies on imaging diagnosis were performed on chronic lesions or sequelae of schistosomiasis. Most of the techniques were used on admitted patients in well-equipped hospitals. US was introduced in the 1970s as a safe, rapid, non-invasive and inexpensive technique and has been used for diagnosis in hospitals and screening in the fields. As a typical US image of the liver, septal formation by high echogenic bands like mosaic was described, and this network pattern was reported in the other endemic countries; China and Philippines. As an appropriate technique, US has been broadly used in developing countries. Not only for diagnosis in a hospital, but also for monitoring changes of morbidity, US is used in the community level. Network pattern related to the severity of S. japonicum infection, has not been described in S. mansoni or S. haematobium infection. Appearance of network pattern depends on pathological changes such as periportal fibrosis, postnecrotic fibrosis and calcified ova. For advanced studies on morbidity of schistosomiasis japonica, further research on pathological basis of network pattern and standardization of US diagnosis are necessary.     

抗SEA鸡卵黄抗体用于血吸虫循环抗原检测的初步研究

目的:探讨抗可溶性虫卵抗原(SEA)鸡卵黄抗体(Immunoglobulin Y,IgY)用于血吸虫循环抗原检测的可行性。方法:以纯化的鸡抗SEA卵黄抗体为捕捉抗体,以酶标抗SEA单克隆抗体NP28-5B进行双抗体夹心酶联免疫吸附试验法(S-ELISA)检测急、慢性血吸虫病病人和健康人血清,并与常规检测抗体的酶联免疫吸附试验(SEA-ELISA)法做比较。结果:S-ELISA法测得SEA浓度(y)与A450值(x)呈明显的正相关(r=0.9481,y=459.22x-108.14)。S-ELISA法检测急性血吸虫病人循环抗原的阳性率为100%,慢性血吸虫病人循环抗原的阳性率为84.40%,健康人的特异性为96%。两种方法对血吸虫病的检出率差异无统计学意义(P>0.05)。结论:S-ELISA可用于血吸虫病的免疫诊断。     

Schistosome infection promotes osteoclast-mediated bone loss

Infection with schistosome results in immunological changes that might influence the skeletal system by inducing immunological states affecting bone metabolism. We investigated the relationships between chronic schistosome infection and bone metabolism by using a mouse model of chronic schistosomiasis, affecting millions of humans worldwide. Results showed that schistosome infection resulted in aberrant osteoclast-mediated bone loss, which was accompanied with an increased level of receptor activator of nuclear factor-κB (NF-κB) Ligand (RANKL) and decreased level of osteoprotegerin (OPG). The blockade of RANKL by the anti-RANKL antibody could prevent bone loss in the context of schistosome infection. Meanwhile, both B cells and CD4⁺ T cells, particularly follicular helper T (Tfh) cell subset, were the important cellular sources of RANKL during schistosome infection. These results highlight the risk of bone loss in schistosome-infected patients and the potential benefit of coupling bone therapy with anti-schistosome treatment.     

Disappearance of specific antibodies in patients with chronic schistosomiasis japonica by treatment with praziquantel

We tested effects of praziquantel, an antischistosomal compound, on clinical and immunological parameters of chronic schistosomiasis japonica. Two Japanese patients, who had high antibody titers to Schistosoma japonicum antigens but no fecal schistosome eggs or no or mild symptoms complained, were treated with praziquantel. Within two years after treatment, anti-schistosome antibodies in sera from the patients became negative in enzyme-linked immunosorbent assay. There was no significant alteration in cellular immunity to the parasite. Although S. japonicum infection is believed to have been eradicated in Japan, our present results seem to suggest the possibility that a few Japanese individuals, who have high anti-schistosome antibody, still harbor live parasites.     

Schistosome vaccine testing: lessons from the baboon model

The high level of protection elicited in rodents and primates by the radiation-attenuated schistosome vaccine gives hope that a human vaccine relying on equivalent mechanisms is feasible. In humans, a vaccine would be undoubtedly administered to previously or currently infected individuals. We have therefore used the olive baboon to investigate whether vaccine-induced immunity is compromised by a schistosome infection. We showed that neither a preceding infection, terminated by chemotherapy, nor an ongoing chronic infection affected the level of protection. Whilst IgM responses to vaccination or infection were short-lived, IgG responses rose with each successive exposure to the vaccine. Such a rise was obscured by responses to egg deposition in already-infected animals. In human trials it would be necessary to use indirect estimates of infection intensity to determine vaccine efficacy. Using worm burden as the definitive criterion, we demonstrated that the surrogate measures, fecal eggs, and circulating antigens, consistently overestimated protection. Regression analysis of the surrogate parameters on worm burden revealed that the principal reason for overestimation was the threshold sensitivity of the assays. If we extrapolate our findings to human schistosomiasis mansoni, it is clear that more sensitive indirect measures of infection intensity are required for future vaccine trials.     

HLA class II antigens positively and negatively associated with hepatosplenic schistosomiasis in a Chinese population

To identify possible associations between host genetic factors and the onset of liver fibrosis following Schistosoma japonicum infection, the major histocompatibility class II alleles of 84 individuals living on an island (Jishan) endemic for schistosomiasis japonica in the Poyang Lake Region of Southern China were determined. Forty patients exhibiting advanced schistosomiasis, characterised by extensive liver fibrosis, and 44 age and sex-matched control subjects were assessed for the class II haplotypes HLA-DRB1 and HLA-DQB1. Two HLA-DRB1 alleles, HLA-DRB1*0901 (P=0.012) and *1302 (P=0.039), and two HLA-DQB1 alleles, HLA-DQB1*0303 (P=0.012) and *0609 (P=0.037), were found to be significantly associated with susceptibility to fibrosis. These associated DRB1 and DQB1 alleles are in very strong linkage disequilibrium, with DRB1*0901-DQB1*0303 and DRB1*1302-DQB1*0609 found as common haplotypes in this population. In contrast, the alleles HLA-DRB1*1501 (P=0.025) and HLA-DQB1*0601 (P=0.022) were found to be associated with resistance to hepatosplenic disease. Moreover, the alleles DQB1*0303 and DRB1*0901 did not increase susceptibility in the presence of DQB1*0601, indicating that DQB1*0601 is dominant over DQB1*0303 and DRB1*0901. The study has thus identified both positive and negative associations between HLA class II alleles and the risk of individuals developing moderate to severe liver fibrosis following schistosome infection.     

Soluble interleukin-2 receptor (sCD25) and interleukin-10 plasma concentrations are associated with severity of primary respiratory syncytial virus (RSV) infection

The role of the immune response in the severity of RSV infection was examined by determining plasma concentrations of interferon-gamma (IFN-gamma), interleukin-10 (IL-10), interleukin-2 receptor (sCD25) and soluble tumor necrosis factor receptor II (sTNFR-II) in 196, previously healthy infants, during acute and convalescence phases of primary RSV infection. The results were analyzed separately for days 1-4 (early) and days 5-7 (late) of symptoms before sample collection and according to disease severity (105 hypoxic, 91 non-hypoxic). Significant associations between plasma levels and severity were found in early samples only. IL-10 and sCD25 concentrations were higher (p=0.01, each) in hypoxic compared with non-hypoxic infants, whereas no differences were observed in IFN-gamma and sTNFR-II levels between the groups. Early sCD25 levels correlated positively with IL-10 concentrations (p= 0.0003; r= 0,401). Amongst the hypoxic infants, the number of days of oxygen supplementation correlated positively with early IL-10 levels (p=0.009; r=0.495) and negatively with the IFN-gamma/IL-10 ratio (p=0.007; r=0.495). IFN-gamma levels were significantly higher in the acute phase than during convalescence for hypoxic and non-hypoxic infants, while IL-10 levels were significantly higher in the acute phase only in hypoxic infants for days 1-4 (early; p=0.0007). sCD25 concentrations were elevated only in hypoxic infants at days 1-4 of the acute phase (p=0.002), whereas sTNFR-II levels did not vary between acute and convalescence phases, independent of severity and time point of sampling. We found no association between plasma levels during the convalescence phase and the severity of the RSV infection.     

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.     

日本血吸虫性病兔肝纤维化的酶组织化学研究

目的观察日本血吸虫感染家兔导致肝脏发生纤维化后的肝组织酶学改变.方法将23只成年健康大耳白兔分为正常对照组(N)8只,模型组(M)15只,M组采用腹贴法(日本血吸虫尾蚴180条/只,持续15min)感染血吸虫,六周后服用吡喹酮行杀虫治疗.于实验的第13周将全部动物麻醉后剖腹取肝组织.肝组织行HE染色和电镜观察;酶组织化学方法检测单胺氧化酶(MAO)、一氧化氮合酶(NOS)、琥珀酰脱氢酶(SDH)、乳酸脱氢酶(LDH)在器官的表达活性.结果在血吸虫感染家兔的第13周可观察到肝组织明显纤维化;模型组中MAO、NOS、LDH活性明显高于正常对照组,而SDH活性则明显降低.结论慢性血吸虫感染引起的肝纤维化导致肝细胞缺血缺氧,影响NOS、SDH、LDH活性,加重肝细胞损伤.     

Prevalence of schistosome infections within molluscan populations: observed patterns and theoretical predictions

The paper draws together a large and scattered body of empirical evidence concerning the prevalence of snail infection with schistosome parasites in field situations, the duration of the latent period of infection in snails (and its dependence on temperature), and the mortality rates of infected and uninfected snails in field and laboratory conditions. A review and synthesis of quantitative data on the population biology of schistosome infections within the molluscan host is attempted and observed patterns of infection are compared with predictions of a schistosomiasis model developed by May (1977) which incorporates differential snail mortality (between infected and uninfected snails) and latent periods of infection. It is suggested that the low levels of prevalence within snail populations in endemic areas of schistosomiasis are closely associated with high rates of infected snail mortality and the duration of the latent period of infection within the mollusc. In certain instances, the expected life-span of an infected snail may be less than the duration of the latent period of infection. Such patterns generate very low levels of parasite prevalence. A new age prevalence model for schistosome infections within snail populations is developed and its predictions compared with observed patterns. The implications of this study of observed and predicted patterns of snail infection within molluscan populations are discussed in relation to the overall transmission dynamics of schistosomiasis.     

Serological differentiation of acute and chronic schistosomiasis using Schistosoma mansoni recombinant protein RP26

We obtained a recombinant protein encoded by Schistosoma mansoni gene which was able to differentiate acute from chronic schistosomiasis when applied as antigen in enzyme-linked immunosorbent assay (ELISA). A cDNA clone encoding a 26 kDa recombinant protein (RP26) was selected by screening of an adult worm S. mansoni λZAP expression library with rabbit sera produced against PIII, an adult worm protein fraction already known to possess protective and immunomodulating effects. The clone cDNA presented 99% identity with S. mansoni Sm22.3 gene. We assayed IgG reactivity of sera from 18 patients with acute, 25 patients with chronic S. mansoni infection and 20 uninfected donors with RP26 in ELISA. Our results showed that 89% of sera were positive in acute schistosomiasis group, and only 26% in chronic group, without false-positive reactions in uninfected group. In mice the immune response to RP26 increased up to week 9 after infection and then diminished. We proposed that production of antibodies binding to RP26 stopped at the chronic stage of disease. The testing of sera from eight other parasitic infections with RP26 revealed no positive reactions in majority of sera. However, we observed low positive reaction in sera from 20% of leishmaniasis patients. Our results indicate that a recombinant protein RP26 can be used as immunodiagnostic reagent for detection of acute phase of schistosomiasis mansoni.