Diagnostic values of parasite-specific antibody detections in saliva and urine in comparison with serum in opisthorchiasis

Multi-epitope protein production and its application in the diagnosis of opisthorchiasis

BACKGROUND

Opisthorchiasis and cholangiocarcinoma (CCA) continue to be public health concerns in many Southeast Asian countries. Although the prevalence of opisthorchiasis is declining, reported cases tend to have a light-intensity infection. Therefore, early detection by using sensitive methods is necessary. Several sensitive methods have been developed to detect opisthorchiasis. The immunological detection of antigenic proteins has been proposed as a sensitive method for examining opisthorchiasis.

METHODS

The Opisthorchis viverrini antigenic proteins, including cathepsin B (OvCB), asparaginyl endopeptidase (OvAEP), and cathepsin F (OvCF), were used to construct multi-antigenic proteins. The protein sequences of OvCB, OvAEP, and OvCF, with a high probability of B cell epitopes, were selected using BepiPred 1.0 and the IEDB Analysis Resource. These protein fragments were combined to form OvCB_OvAEP_OvCF recombinant DNA, which was then used to produce a recombinant protein in Escherichia coli strain BL21(DE3). The potency of the recombinant protein as a diagnostic target for opisthorchiasis was assessed using immunoblotting and compared with that of the gold standard method, the modified formalin-ether concentration technique.

RESULTS

The recombinant OvCB_OvAEP_OvCF protein showed strong reactivity with total immunoglobulin G (IgG) antibodies against light-intensity O. viverrini infections in the endemic areas. Consequently, a high sensitivity (100%) for diagnosing opisthorchiasis was reported. However, cross-reactivity with sera from other helminth and protozoan infections (including taeniasis, strongyloidiasis, giardiasis, E. coli infection, enterobiasis, and mixed infection of Echinostome spp. and Taenia spp.) and no reactivity with sera from patients with non-parasitic infections led to a reduced specificity of 78.4%. In addition, the false negative rate (FNR), false positive rate (FPR), positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy were 0%, 21.6%, 81.4%, 100%, and 88.9%, respectively.

CONCLUSIONS

The high sensitivity of the recombinant OvCB_OvAEP_OvCF protein in detecting opisthorchiasis demonstrates its potential as an opisthorchiasis screening target. Nonetheless, research on reducing cross-reactivity should be undertaken by detecting other antibodies in other sample types, such as saliva, urine, and feces.

Epidemiology and Control of Opisthorchis viverrini Infection: Implications for Cholangiocarcinoma Prevention

It is known that Opisthorchis viverrini (OV) is the most significant risk factor for the development of cholangiocarcinoma (CCA); hence, it is also known as carcinogenic parasite. Effective control and elimination of OV infection should significantly reduce O. viverrini-related CCA. This chapter includes details of the three recently developed innovative tools, namely the Isan cohort database software, an OV-RDT for screening of O. viverrini, and an ultrasound telecommunication system. Past and current control programs, i.e., education, medication, and sanitation were discussed and stressed the need for a comprehensive control program which encompasses primary, secondary, and tertiary patient care programs for confirmation and management of suspected CCA cases. The approach of mathematical modeling for control of OV and CCA was also briefly described. Additionally, we highlighted the current progress toward control of OV and CCA in Thailand and potential for expansion into nearby countries in Southeast Asia.

Diagnostic performance of a urine-based ELISA assay for the screening of human schistosomiasis japonica: A comparative study

The current study developed and evaluated the performance of a urine-based enzyme-linked immunosorbent assay (ELISA) for the screening of Schistosoma japonicum infection in a human cohort (n = 412) recruited from endemic areas, Northern Samar, the Philippines. The diagnostic performance of the urine ELISA assay was further compared with the Kato-Katz (KK) technique, serum-based ELISA assays, point-of-care circulating cathodic antigen (POC-CCA) urine cassette test, and droplet digital (dd)PCR assays performed on feces, serum, urine, and saliva samples, which were designated as F_ddPCR, SR_ddPCR, U_ddPCR, and SL_ddPCR, respectively. When urine samples concentrated 16× were assessed, the SjSAP4 + Sj23-LHD-ELISA (U) showed sensitivity/specificity values of 47.2/93.8% for the detection of S. japonicum infection in KK-positive individuals (n = 108). The prevalence of S. japonicum infection in the total cohort determined by the urine ELISA assay was 48.8%, which was lower than that obtained with the F_ddPCR (74.5%, p < 0.001), SR_ddPCR (67.2%, p < 0.001), and SjSAP4 + Sj23-LHD-ELISA (S) (66.0%, p < 0.001), but higher than that determined by the Sj23-LHD-ELISA (S) (24.5%, p < 0.001), POC-CCA assay (12.4%, p < 0.001), and SL_ddPCR (25.5%, p < 0.001). Using the other diagnostic tests as a reference, the urine ELISA assay showed a sensitivity between 47.2 and 56.9%, a specificity between 50.7 and 55.2%, and an accuracy between 49.3 and 53.4%. The concentrated urine SjSAP4 + Sj23-LHD-ELISA developed in the current study was more sensitive than both the KK test and POC-CCA assay, and showed a comparable level of diagnostic accuracy to that of the U_ddPCR. However, its diagnostic performance was less robust than that of the F_ddPCR, SR_ddPCR, and SjSAP4 + Sj23-LHD-ELISA (S) assays. Although they are convenient and involve a highly acceptable non-invasive procedure for clinical sample collection, the insufficient sensitivity of the three urine-based assays (the urine ELISA assay, the U_ddPCR test, and the POC-CCA assay) will limit their value for the routine screening of schistosomiasis japonica in the post mass drug administration (MDA) era, where low-intensity infections are predominant in many endemic areas.

Rapid assessment of Opisthorchis viverrini IgG antibody in serum: a potential diagnostic biomarker to predict risk of cholangiocarcinoma in regions endemic for opisthorchiasis

Background:

Opisthorchiasis is caused by an infection with fish-borne liver flukes of the genus Opisthorchis. Opisthorchiasis frequently leads to chronic inflammation in the biliary tract and is classified as a group 1 biological carcinogen by the International Agency for Research on Cancer: a definitive risk for cholangiocarcinoma (CCA).

Methods:

We used the rapid immunochromatographic test (ICT) to detect anti-Opisthorchis viverrini IgG and IgG4 subclass antibodies in sera of patients with CCA. The ICT kits were developed based on soluble antigens excreted and secreted by O. viverrini adult worms.

Results:

ICT indicated sera was positive for IgG and IgG4 antibodies, respectively, in 22 (61.1%) and 15 (41.6%) participants of the 36 study participants diagnosed with CCA (P > 0.05). Our study also included groups with other cancers and with liver cirrhosis, where the IgG ICT and IgG4 ICT kits were 27.7% (13/47) and 25.5% (12/47) positive, respectively (P > 0.05). Neither total the IgG ICT nor the IgG4 ICT yielded positive results in a control group of 20 healthy participants. Moreover, the percentage positivity rate using the ICT for total IgG between the CCA group and the other cancers and liver cirrhosis group was significantly different (P < 0.05). By contrast, no significant difference between these groups was apparent in the ICT for IgG4 antibody. The CCA group was 6.53 times more likely to have positive anti–O. viverrini IgG antibody (odds ratio 6.53, P < 0.001) and 3.27 times more likely to have positive anti–O. viverrini IgG4 antibody (odds ratio 3.27, P = 0.010) than the non-CCA group.

Conclusion:

This information is of potential value for the development of a diagnostic biomarker to predict risk for O. viverrini infection-associated CCA.

Plasma checkpoint protein 1 (Chk1) as a potential diagnostic biomarker for opisthorchiasis and cholangiocarcinoma

BACKGROUND

Patients infected with a parasite often develop opisthorchiasis viverrini, which often progresses into cholangiocarcinoma (CCA) due to the asymptomatic nature of the infection. Currently, there are no effective diagnostic methods for opisthorchiasis or cholangiocarcinoma.

OBJECTIVE

The aim of this study was to identify the host-responsive protein that can be developed as a diagnostic biomarker of opisthorchiasis and cholangiocarcinoma.

METHODS

Plasma samples were collected from non-OVCCA, OV, and CCA subjects, and the proteomes were investigated by LC-MS/MS. Venn diagrams and protein network prediction by STITCH were used to identify the potential biomarkers. The level of candidate protein, the plasma checkpoint protein 1 (Chk1), was measured by indirect enzyme-linked immunosorbent assay (ELISA).

RESULTS

Chk1 was present in the center of the protein network analysis in both the OV and CCA groups. In addition, the plasma Chk1 levels were significantly increased in both groups (P< 0.05). The sensitivity of the opisthorchiasis viverrini and cholangiocarcinoma was 59.38% and 65.62%, respectively, while the specificity of both was 85.71%.

CONCLUSION

Chk1 was identified by differential plasma proteomes and was increased in O. viverrini-infected and cholangiocarcinoma-derived plasma samples. Higher levels of plasma Chk1 levels may serve as a potential diagnostic biomarker for opisthorchiasis and cholangiocarcinoma.

A fluorescence AuNPs-LISA: A new approach for Opisthorchis viverrini (Ov) antigen detection with a simple fluorescent enhancement strategy by surfactant micelle in urine samples

The colorimetric AuNPs-LISA is a new, powerful technique for the detection of Opisthorchis viverrini antigen (OvAg) in urine samples. However, the diagnostic sensitivity of the colorimetric AuNPs-LISA is powerless to screen ultralow concentrations of OvAg in urine samples in cases of early stage liver fluke infection. This work, we aimed to improve the diagnostic sensitivity of the colorimetric AuNPs-LISA by developing a new fluorescence AuNPs-LISA. O-phenylenediamine (OPD) was used as the chromogenic substrate instead of the tetramethylbenzidine (TMB) of the colorimetric AuNPs-LISA. Interestingly, the fluorescence of the OPD oxidation product by the peroxidase-like activity of labelled AuNPs can be extremely enhanced by a non-ionic surfactant, especially the Triton X-100. The proposed assay exhibited a dynamic linear detection of OvAg concentration in the range of 34.18 ng mL^-1 to 273.44 ng mL^-1 with the limit of detection at 36.97 ng mL^-1 which the detection sensitivity enhancement around 1200-fold when comparing with the colorimetric AuNPs-LISA. This model exhibits high diagnosis sensitivity, specificity and accuracy, 91.28%, 91.75%, and 91.59%, respectively, compared to the traditional ELISA. The fluorescence AuNPs-LISA showed excellent potential for the diagnosis of OvAg in urine samples from endemic areas. This will provide an effective tool for the detection, control and elimination of human opisthorchiasis.

High prevalence of opisthorchiasis in rural populations from Khammouane Province, central Lao PDR: serological screening using total IgG- and IgG4-based ELISA

BACKGROUND

Human opisthorchiasis, caused by Opisthorchis viverrini, is a public health problem in Southeast Asia and a major risk factor for cholangiocarcinoma. In Lao PDR, seroprevalence and the relationship between the number of O. viverrini eggs in infected people and specific antibody responses are still unknown. We evaluated and compared parasitological and serological screening methods in the community in an endemic area of opisthorchiasis in Lao PDR.

METHODS

Seroprevalence of O. viverrini-specific total IgG and IgG4 antibodies and their relationships with O. viverrini egg intensities were evaluated in Khammouane Province, central Lao PDR, using ELISA and a modified formalin ethyl-acetate concentration technique (FECT).

RESULTS

FECT stool examination revealed O. viverrini eggs in 70.3% (90/128) of individuals (95% CI 61.6 to 78.1%) while ELISA (based on total IgG and on IgG4 antibodies to O. viverrini) found 98.4% (95% CI 94.5 to 99.8%) and 89.8% (95% CI 83.3 to 94.5%) of sera, respectively. There was a positive and significant correlation between numbers of O. viverrini eggs per gram and levels of both IgG (R2=0.168, p<0.001) and IgG4 (R2=0.219, p<0.001) antibodies.

CONCLUSIONS

A high prevalence of human opisthorchiasis in Lao PDR was found using a new platform, serological screening in the community. This points to a need for sustainable control of this liver fluke infection.

An update on non-invasive urine diagnostics for human-infecting parasitic helminths: what more could be done and how?

Reliable diagnosis of human helminth infection(s) is essential for ongoing disease surveillance and disease elimination. Current WHO-recommended diagnostic assays are unreliable in low-endemic near-elimination settings and typically involve the invasive, onerous and potentially hazardous sampling of bodily fluids such as stool and blood, as well as tissue via biopsy. In contrast, diagnosis by use of non-invasive urine sampling is generally painless, more convenient and low risk. It negates the need for specialist staff, can usually be obtained immediately upon request and is better accepted by patients. In some instances, urine-based diagnostic assays have also been shown to provide a more reliable diagnosis of infection when compared to traditional methods that require alternative and more invasive bodily samples, particularly in low-endemicity settings. Given these relative benefits, we identify and review current research literature to evaluate whether non-invasive urine sampling is currently exploited to its full potential in the development of diagnostic tools for human helminthiases. Though further development, assessment and validation are needed before their routine use in control programmes, low-cost, rapid and reliable assays capable of detecting transrenal helminth-derived antigens and cell-free DNA show excellent promise for future use at the point-of-care in high-, medium- and even low-endemicity elimination settings.

Diagnosis of Human Trematode Infections

Digenetic trematodes form a major group of human parasites, affecting a large number of humans, especially in endemic foci. Over 100 species have been reported infecting humans, including blood, lung, liver, and intestinal parasites. Traditionally, trematode infections have been diagnosed by parasitological methods based on the detection and the identification of eggs in different clinical samples. However, this is complicated due to the morphological similarity between eggs of different trematode species and other factors such as lack of sensitivity or ectopic locations of the parasites. Moreover, the problem is currently aggravated by migratory flows, international travel, international trade of foods, and changes in alimentary habits. Although efforts have been made for the development of immunological and molecular techniques, the detection of eggs through parasitological techniques remains as the gold standard for the diagnosis of trematodiases. In this chapter, we review the current status of knowledge on diagnostic techniques used when examining feces, urine, and sputum and also analyze the most relevant characteristics used to identify eggs with a quick key for the identification of eggs.

Liver Flukes: Clonorchis and Opisthorchis

Clonorchis sinensis, Opisthorchis viverrini, and O. felineus are liver flukes of human and animal pathogens occurring across much of Europe and Asia. Nevertheless, they are often underestimated compared to other, better known neglected diseases in spite of the fact that many millions of people are infected and hundreds of millions are at risk. This is possibly because of the chronic nature of the infection and disease and that it takes several decades prior to a life-threatening pathology to develop. Several studies in the past decade have provided more information on the molecular biology of the liver flukes which clearly lead to better understanding of parasite biology, systematics, and population genetics. Clonorchiasis and opisthorchiasis are characterized by a chronic infection that induces hepatobiliary inflammation, especially periductal fibrosis, which can be detected by ultrasonography. These chronic inflammations eventually lead to cholangiocarcinoma (CCA), a usually fatal bile duct cancer that develops in some infected individuals. In Thailand alone, opisthorchiasis-associated CCA kills up to 20,000 people every year and is therefore of substantial public health importance. Its socioeconomic impacts on impoverished families and communities are considerable. To reduce hepatobiliary morbidity and CCA, the primary intervention measures focus on control and elimination of the liver fluke. Accurate diagnosis of liver fluke infections in both human and other mammalian, snail and fish intermediate hosts, are important for achieving these goals. While the short-term goal of liver fluke control can be achieved by praziquantel chemotherapy, a comprehensive health education package targeting school children is believed to be more beneficial for a long-term goal/solution. It is recommended that a transdisciplinary research or multisectoral control approach including one health and/or eco health intervention strategy should be applied to combat the liver flukes, and hence contribute to reduction of cholangiocarcinoma in endemic areas.

Liver Fluke-Associated Biliary Tract Cancer

Cholangiocarcinoma (CCA) is an aggressive cancer arising from epithelial cells of the bile duct. Most patients with CCA have an unresectable tumor at the time of diagnosis. In Western countries, the risk of CCA increases in patients with primary sclerosing cholangitis, whereas liver fluke infection appears to be the major risk factor for CCA in Asian countries. A diagnosis of liver fluke infection often relies on stool samples, including microscopic examination, polymerase chain reaction-based assays, and fluke antigen detection. Tests of serum, saliva and urine samples are also potentially diagnostic. The presence of liver fluke along with exogenous carcinogens magnifies the risk of CCA in people living in endemic areas. The “liver fluke-cholangiocarcinoma” carcinogenesis pathways consist of mechanical damage to the bile duct epithelium, immunopathologic and cellular reactions to the liver fluke’s antigens and excretory/secretory products, liver fluke-induced changes in the biliary tract microbiome and the effects of repeated treatment for liver fluke. A vaccine and novel biomarkers are needed for the primary and secondary prevention of CCA in endemic areas. Importantly, climate change exerts an effect on vector-borne parasitic diseases, and awareness of liver fluke should be enhanced in potentially migrated habitat areas.

Bethony J. Diagnostic performance of urinary IgG antibody detection: A novel approach for population screening of strongyloidiasis

The diagnosis of strongyloidiasis by coprological methods has a low sensitivity, underestimating the prevalence of Strongyloides stercoralis in endemic areas. Serodiagnostic tests for strongyloidiasis have shown robust diagnostic properties. However, these methods require a blood draw, an invasive and labor-intensive sample collection method, especially in the resource-limited settings where S. stercoralis is endemic. Our study examines a urine-based assay for strongyloidiasis and compares its diagnostic accuracy with coprological and serological methods. Receiver operating characteristic (ROC) curve analyses determined the diagnostic sensitivity (D-Sn) and specificity (D-Sp) of the urine ELISA, as well as estimates its positive predictive value and diagnostic risk. The likelihood ratios of obtaining a positive test result (LR+) or a negative test result (LR-) were calculated for each diagnostic positivity threshold. The urine ELISA assay correlated significantly with the serological ELISA assay for strongyloidiasis, with a D-Sn of 92.7% and a D-Sp of 40.7%, when compared to coprological methods. Moreover, the urine ELISA IgG test had a detection rate of 69%, which far exceeds the coprological method (28%). The likelihood of a positive diagnosis of strongyloidiasis by the urine ELISA IgG test increased significantly with increasing units of IgG detected in urine. The urine ELISA IgG assay for strongyloidiasis assay has a diagnostic accuracy comparable to serological assay, both of which are more sensitive than coprological methods. Since the collection of urine is easy and non-invasive, the urine ELISA IgG assay for strongyloidiasis could be used to screen populations at risk for strongyloidiasis in S. stercoralis endemic areas.

Recent Advances in the Diagnosis and Detection of Opisthorchis viverrini Sensu Lato in Human and Intermediate Hosts for Use in Control and Elimination Programs

Opisthorchiasis is a neglected tropical disease, caused by infection with the fish-borne trematode Opisthorchis viverrini sensu lato that afflicts more than 10million people in Southeast Asia, including Thailand, Lao PDR, Vietnam and Cambodia. The disease is characterized by a chronic infection that induces hepatobiliary inflammation, especially periductal fibrosis, which can be detected by ultrasonography. This chronic inflammation eventually leads to cholangiocarcinoma (CCA), a usually fatal bile duct cancer that develops in approximately 1% of O. viverrini-infected individuals. In Thailand alone, CCA kills up to 20,000 people every year and is therefore of substantial public health importance. Its socioeconomic impacts on impoverished families and communities are considerable. To reduce O. viverrini-associated morbidity and CCA, the primary intervention measures focus on opisthorchiasis control and elimination. Accurate diagnoses of O. viverrini infection, in both mammalian, snail and fish intermediate hosts, are important for achieving these goals. Despite extensive efforts over several decades to find sensitive and specific diagnostics for opisthorchiasis, a simple and robust diagnostic method is still required. Here we review earlier and current developments in the search for new diagnostics for opisthorchiasis, with practical applications in the research laboratory, the clinic and the field. Of the methods currently available, the urine antigen assay shows considerable potential for the diagnosis and screening of opisthorchiasis. Nevertheless, these new assays require validation, determination of their cost-effectiveness when applied for mass screening in an endemic setting in support of policy decisions for national public health programs aimed at the control and elimination of opisthorchiasis.

Current Perspectives on Opisthorchiasis Control and Cholangiocarcinoma Detection in Southeast Asia

Similar to bile duct cancer or cholangiocarcinoma (CCA) in the western world, opisthorchiasis-associated CCA in Southeast Asia is an aggressive cancer with high mortality rates. It is known to cause a significant health burden in the opisthorchiasis region in Thailand and possibly throughout mainland Southeast. To reduce this health burden, a comprehensive prevention and control program for opisthorchiasis, as well as CCA, is required. In this review, our aim is to provide a brief update of the current situation regarding the natural history of opisthorchiasis and health burden of CCA in Southeast Asia. A comprehensive approach to tackling these issues being implemented in Thailand under the “Cholangiocarcinoma Screening and Care Program” is described. This comprehensive program consists of a three stage prevention and patient care program. The primary prevention component involves opisthorchiasis screening using a new and sensitive urine assay. The secondary prevention component involves screening for CCA and periductal fibrosis, with suspected CCA patients following the protocol for confirmation and appropriate treatment. Due to the eco-epidemiology of opisthorchiasis-induced CCA, the anticipated impacts and outcomes of the program include short-, medium-, and the long-term goals for the reduction of CCA incidence. To achieve long-term sustainable impacts, concerted efforts to raise social awareness and participating action by general public, non-government organizations, and government agencies are necessary. The strategic plans developed for this program can be expanded for use in other endemic areas as well as being a model for use in other chronic diseases.

Immune complex detection in saliva samples: an innovative proposal for the diagnosis of human strongyloidiasis

Human strongyloidiasis is caused by helminth Strongyloides stercoralis. It has a worldwide distribution, often neglected and cause of severe morbidity. The parasitological diagnosis is hindered by the low and irregular amount of larvae in feces. The goal of the present study was to detect IgG and IgG immune complex using conventional serum samples and saliva as alternative samples. We collected samples from 60 individuals, namely: group I composed of 30 healthy individuals; and group II composed of 30 individuals eliminating S. stercoralis larvae in feces. We calculated the area under the curve, general index of diagnostic accuracy, Kappa index and determined the correlations between different diagnostic tests. The detection of IgG levels was performed by an immunoenzymatic assay with alkaline extract of S. venezuelensis larvae as antigen. Positivity of anti-S. stercoralis IgG in serum samples from group I was 3·3%, and from group II 93·3%. The detection of immune complex indicated that group I exhibited 3·3% and group II 56·7%. In the saliva samples, IgG detection was 26·7% for group I and 43·3% for group II. Immune complex was detected in 20% of group I, and 30% of group II. IgG immune complex in conventional serum samples and saliva as alternative samples can be considered biomarkers for the diagnosis of active strongyloidiasis.

Opisthorchiasis and cholangiocarcinoma in Southeast Asia: an unresolved problem

The prevalence of cholangiocarcinoma (CCA) in Southeast Asia is much higher than other areas of the world. Eating raw, fermented, or undercooked cyprinid fish, infected with the liver fluke, Opisthorchis viverrini sensu lato (sl), results in chronic biliary inflammation, periductal fibrosis, and increased cancer risk. There may be associated glomerulonephritis. The process of infection is difficult to disrupt because eating practices have proven extremely difficult to change, and the life cycle of the fluke cannot be broken due to high prevalence in canine and feline reservoir hosts. Fecal analysis and enzyme-linked immunosorbent assay tests can be used to diagnose opisthorchiasis. Diagnosis of CCA is complex, partly due to the lack of definitive imaging characteristics but also due to the difficulty of obtaining samples for cytology or histology. This cancer has proven to be resistant to common chemotherapy treatments and so the two avenues of treatment available are surgical resection and liver transplantation, both requiring early detection of the tumor for the best chances of success. Late presentation of symptoms reduces the chances of successful surgical intervention. While liver fluke infections can be treated with praziquantel, individuals will often become reinfected, and multiple reinfections can be more harmful than a singular, long-term infection. A key research on the detection and characterization of novel biomarkers in all parts of the carcinogenic pathway for early diagnosis is needed.

Enzyme-linked immunosorbent assay for diagnosis of Amphimerus spp. liver fluke infection in Humans

BACKGROUND

Amphimerus spp. is a liver fluke that infects humans and domestic animals. It is highly prevalent in some Ecuadorian communities. Currently, diagnosis is based on the microscopic observation of eggs in faeces, but this has variable sensitivity. More sensitive methods are needed for diagnostic testing.

OBJECTIVE

The main objective of this work was to develop an enzyme-linked immunosorbent assay (ELISA) using crude antigens from Amphimerus spp. adult worms to detect anti-Amphimerus IgG in human sera.

METHODS

Crude somatic antigens were obtained from adult Amphimerus spp. worms. Human sera from 119 patients were tested: 48 from individuals with a confirmed Amphimerus spp. infection, 78 from non-infected Ecuadorians living in the endemic region, 60 from persons living in non-endemic areas (20 Ecuadorians, 20 Europeans, and 20 Africans), and 33 who had other parasitic and non-parasitic infections.

PRINCIPAL FINDINGS

Results were analysed using the receiver-operator characteristic (ROC) curve analysis with an area under curve (AUC) value of 0.967. The accuracy of the ELISA was high. The sensitivity was 85.0% [95% confidence interval (CI): 80.3-89.7%] and the specificity was 71.0% (95% CI: 65.2-76.8%). Some cross reactivity was detected against Paragonimus mexicanus, Fasciola hepatica, Schistosomiasis, Taenia solium, Strongyloides stercoralis, Mansonella spp., and Vampirolepis nana.

MAIN CONCLUSIONS

We have developed the first ELISA technique that detects anti-Amphimerus IgG in human sera with good sensitivity, repeatability and reproducibility. However, more specific antigens are needed to further enhance performance of this assay. Regardless, this ELISA test could be useful for early diagnosis and prompt treatment of human Amphimerus spp. infections.

Advances in the Diagnosis of Human Opisthorchiasis: Development of Opisthorchis viverrini Antigen Detection in Urine

BACKGROUND

Many strategies to control opisthorchiasis have been employed in Thailand, but not in the other neighbouring countries. Specific control methods include mass drug administration (MDA) and health education to reduce raw fish consumption. These control efforts have greatly shifted the epidemiology of Opisthorchis viverrini (OV) infection over the last decade from presenting as densely concentrated "heavy" infections in single villages to widespread "light" OV infections distributed over wide geographical areas. Currently, the "gold standard" detection method for OV infection is formalin ethyl-acetate concentration technique (FECT), which has limited diagnostic sensitivity and diagnostic specificity for light OV infections, with OV eggs often confused with eggs of minute intestinal flukes (MIFs) in feces. In this study, we developed and evaluated the diagnostic performance of a monoclonal antibody-based enzyme-linked immunosorbent assay for the measurement of OV excretory-secretory (ES) antigens in urine (urine OV-ES assay) for the diagnosis of opisthorchiasis compared to the gold standard detection FECT method.

METHODOLOGY

We tested several methods for pre-treating urine samples prior to testing the diagnostic performance of the urine OV-ES assay. Using trichloroacetic acid (TCA) pre-treated urine, we compared detection and quantification of OV infection using the urine OV-ES assay versus FECT in OV-endemic areas in Northeastern Thailand. Receiver operating characteristic (ROC) curves were used to determine the diagnostic sensitivity and specificity of the urine OV-ES assay using TCA pre-treated urine, and to establish diagnostic positivity thresholds. The Positive Predictive Value as well as the likelihood of obtaining a positive test result (LR+) or a negative test result (LR-) were calculated for the established diagnostic positivity threshold. Diagnostic risks (Odds Ratios) were estimated using logistic regression.

RESULTS

When urine samples were pre-treated with TCA prior to use in the urine OV-ES assay, the analytical sensitivity was significantly improved. Using TCA pre-treatment of urine, the urine OV-ES assay had a limit of detection (LoD) of 39 ng/ml compared to the LoD of 52 ng/mL reported for coprological antigen detection methods. Similarly, the urine OV-ES assay correlated significantly with intensity of OV infection as measured by FECT. The urine OV-ES assay was also able to detect 28 individuals as positive from the 63 (44.4%) individuals previously determined to be negative using FECT. The likelihood of a positive diagnosis of OV infection by urine OV-ES assay increased significantly with the intensity of OV infection as determined by FECT. With reference to FECT, the sensitivity and specificity of the urine OV-ES assay was 81% and 70%, respectively.

CONCLUSION

The detection of OV-infection by the urine OV-ES assay showed much greater diagnostic sensitivity and diagnostic specificity than the current "gold standard" FECT method for the detection and quantification of OV infection. Due to its ease-of-use, and noninvasive sample collection (urine), the urine OV-ES assay offers the potential to revolutionize the diagnosis of liver fluke infection and provide an effective tool for control and elimination of these tumorigenic parasites.

Meta-genomic analysis of toilet waste from long distance flights; a step towards global surveillance of infectious diseases and antimicrobial resistance

Human populations worldwide are increasingly confronted with infectious diseases and antimicrobial resistance spreading faster and appearing more frequently. Knowledge regarding their occurrence and worldwide transmission is important to control outbreaks and prevent epidemics. Here, we performed shotgun sequencing of toilet waste from 18 international airplanes arriving in Copenhagen, Denmark, from nine cities in three world regions. An average of 18.6 Gb (14.8 to 25.7 Gb) of raw Illumina paired end sequence data was generated, cleaned, trimmed and mapped against reference sequence databases for bacteria and antimicrobial resistance genes. An average of 106,839 (0.06%) reads were assigned to resistance genes with genes encoding resistance to tetracycline, macrolide and beta-lactam resistance genes as the most abundant in all samples. We found significantly higher abundance and diversity of genes encoding antimicrobial resistance, including critical important resistance (e.g. blaCTX-M) carried on airplanes from South Asia compared to North America. Presence of Salmonella enterica and norovirus were also detected in higher amounts from South Asia, whereas Clostridium difficile was most abundant in samples from North America. Our study provides a first step towards a potential novel strategy for global surveillance enabling simultaneous detection of multiple human health threatening genetic elements, infectious agents and resistance genes.

Comparative evaluation of Strongyloides ratti and S. stercoralis larval antigen for diagnosis of strongyloidiasis in an endemic area of opisthorchiasis

The use of Strongyloides ratti as heterologous antigen for serodiagnosis of strongyloidiasis is preferable to Strongyloides from humans due to the ease and safety of antigen preparation. In Southeast Asia where Opisthorchis viverrini coexists with Strongyloides stercoralis, there has been no report in using S. ratti for serodiagnosis of S. stercoralis. In this study, performance of an enzyme-linked immunosorbent assay (ELISA) based on S. ratti was compared with that based on S. stercoralis for diagnosis of strongyloidiasis in areas where O. viverrini is co-endemic in Thailand. Of the 107 individuals, 50 (46.7 %) were positive for S. stercoralis by agar culture method and by ELISA; 82 (76.6 %) and 81 (75.7 %) were seropositive using S. ratti and S. stercoralis antigens, respectively. The levels of parasite-specific IgG to S. ratti and S. stercoralis antigen were significantly proportionally correlated (P < 0.001). Mixed infections with O. viverrini have little effect on diagnosis of strongyloidiasis. Of 42 subjects who were infected with other parasites, there were no cross-reaction with Angiostrongylus cantonensis, Taenia spp., hookworms, Paragonimus spp., Clonorchis sinensis, Ascaris lumbricoides except for Fasciola spp. (1 of 5), and Opisthorchis viverrini (5 of 20). In spite of cross-reactivities, the results suggest that the S. ratti antigen provides an useful option for diagnosis of strongyloidiasis in an endemic area of opisthorchiasis with high sensitivity comparable to the S. stercoralis antigen and provide a basis for effective control strategies for strongyloidiasis.

Microproteinuria during Opisthorchis viverrini infection: a biomarker for advanced renal and hepatobiliary pathologies from chronic opisthorchiasis

Approximately 680 million people are at risk of infection with Opisthorchis viverrini (OV) and Clonorchis sinensis, with an estimated 10 million infected with OV in Southeast Asia alone. While opisthorchiasis is associated with hepatobiliary pathologies, such as advanced periductal fibrosis (APF) and cholangiocarcinoma (CCA), animal models of OV infection show that immune-complex glomerulonephritis is an important renal pathology that develops simultaneously with hepatobiliary pathologies. A cardinal sign of immune-complex glomerulonephritis is the urinary excretion of immunoglobulin G (IgG) (microproteinuria). In community-based studies in OV endemic areas along the Chi River in northeastern Thailand, we observed that over half of the participants had urine IgG against a crude OV antigen extract (OV antigen). We also observed that elevated levels of urine IgG to OV antigen were not associated with the intensity of OV infection, but were likely the result of immune-complex glomerulonephritis as seen in animal models of OV infection. Moreover, we observed that urine IgG to OV antigen was excreted at concentrations 21 times higher in individuals with APF and 158 times higher in individuals with CCA than controls. We also observed that elevated urine IgG to OV antigen could identify APF+ and CCA+ individuals from non-cases. Finally, individuals with urine IgG to OV antigen had a greater risk of APF as determined by Odds Ratios (OR = 6.69; 95%CI: 2.87, 15.58) and a greater risk of CCA (OR = 71.13; 95%CI: 15.13, 334.0) than individuals with no detectable level of urine IgG to OV antigen. Herein, we show for the first time the extensive burden of renal pathology in OV endemic areas and that a urine biomarker could serve to estimate risk for both renal and hepatobiliary pathologies during OV infection, i.e., serve as a “syndromic biomarker” of the advanced pathologies from opisthorchiasis.

Approximately 680 million people risk infection with food-borne trematodes, including Opisthorchis viverrini (OV). Animal models show that significant kidney pathology results from OV infection as detected by antibodies in urine (microproteinuria). However, kidney pathology in humans infected with OV is often overlooked because it develops alongside more severe pathologies such as bile duct fibrosis and bile duct cancer. In Northeastern Thailand, the researchers observed that OV infected individuals had elevated levels of urine IgG against OV antigen that was not associated with the level of OV infection. The researchers observed that urine IgG to OV antigen was associated with bile duct fibrosis and bile duct cancer. Moreover, individuals with urine IgG to OV antigen also had elevated risk of bile duct fibrosis and bile duct cancer than individuals with no urine IgG to OV antigen. For the first time, OV infection has been shown to result in significant kidney disease in humans, which is also strongly associated with bile duct pathology. A urine-based assay that could indicate both renal and bile duct pathology from OV infection would be of profound benefit in Southeast Asia, especially in the resource-limited settings of the Mekong Basin region countries of Thailand, Laos and Cambodia.

Validation of an excretory/secretory antigen based-ELISA for the diagnosis of Opisthorchis felineus infection in humans from low trematode endemic areas

Since opisthorchiasis does not show pathognomonic signs or symptoms, physicians can have serious problems to make a differential diagnosis of this infection in non endemic areas, in particular when there is a simultaneous occurrence with other seasonal infections. Moreover, symptomatic infections due to O. felineus can last a few weeks and then the signs and symptoms disappear, but the worms survive in the bile ducts for years causing hepatobiliary diseases including hepatomegaly, cholangitis, fibrosis of the periportal system, cholecystitis, and gallstones. Consequently, an early diagnosis prevents chronicity and loss of working days. The detection of specific antibodies has been considered as a complementary tool to the fecal examination to establish the definitive diagnosis of this infection and for the follow up. Therefore the aim of this work was the development and validation of an enzyme-linked immunosorbent assay (ELISA) using excretory/secretory antigens (ESA) from O. felineus adult worms to detect anti-Opisthorchis IgG in human sera. A total of 370 human sera were tested: 144 sera from persons with a confirmed diagnosis of opisthorchiasis, 110 sera from healthy Italian people, and 116 sera from people with other parasitic or non-parasitic infections. Results were analyzed by receiver-operator characteristic (ROC) curve analysis. The accuracy of the test, calculated by the area under curve (AUC), yielded a 0.999 value, indicating the high performance of the test. The sensitivity was 100% (95% CI: 97.40% to 100%) and no false-negative sera were detected; the specificity was 99.09% (95% CI: 95.02% to 99.83%). The validated ELISA shows a good performance in terms of sensitivity, repeatability and reproducibility, and it is suitable to detect anti-Opisthorchis IgG in human sera for diagnostic purposes and for the follow up to assess the efficacy of drug treatment.