Antigenuria in visceral leishmaniasis: detection and partial characterisation of a carbohydrate antigen

A review of non-invasive samples and tools in kala-azar diagnosis and test of cure

The recurrence of visceral leishmaniasis (VL), also called kala-azar (KA), in endemic regions of tropical countries like India, is primarily attributed to asymptomatic VL, post-kala azar dermal leishmaniasis (PKDL), and human immunodeficiency virus (HIV) co-infection. To effectively manage VL cases and elimination targets, an early and rapid diagnosis as well as accurate field surveillance is highly essential. The traditional sampling methods like bone marrow (BM), spleen, and lymph node (LN) tissue aspirations are invasive, painful, tedious, and prone to nosocomial infections, require skilled persons and hospital facilities, and are not feasible in rural areas. Therefore, there is an urgent requirement for the adoption of a patient-friendly, non-invasive, non-hospitalized sampling procedure that ensures an effective VL diagnosis. This review aims to meticulously evaluate the most recent scientific research that focuses on the precision, feasibility, and applicability of non-invasive sampling (NIS) and techniques for the diagnosis and test of cure of VL, particularly in resource-limited settings. Apart from that, the non-invasive techniques (NIT) that have shown promising results while monitoring VL treatment response and relapse are also reviewed. The limitations associated with NIT and possible improvements in this regard are discussed as well to improve the diagnosis and management of VL.

Urine is a viral antigen reservoir in hepatitis E virus infection

BACKGROUND AND AIMS

HEV ORF2 antigen (Ag) in serum has become a tool for diagnosing current HEV infection. Particularly, urinary shedding of HEV Ag has been gaining increasing interest. We aim to uncover the origin, antigenicity, diagnostic performance, and diagnostic significance of Ag in urine in HEV infection.

APPROACH AND RESULTS

Clinical serum and urine samples from patients with acute and chronic HEV infection were analyzed for their Ag levels. Ag in urine was analyzed by biochemical and proteomic approaches. The origin of urinary Ag and Ag kinetics during HEV infection was investigated in mouse and rabbit models, respectively. We found that both the Ag level and diagnostic sensitivity in urine were higher than in serum. Antigenic protein in urine was an E2s-like dimer spanning amino acids 453-606. pORF2 entered urine from serum in mice i.v. injected with pORF2. Ag in urine originated from the secreted form of pORF2 (ORF2^S ) that abundantly existed in hepatitis E patients' serum. HEV Ag was specifically taken up by renal cells and was disposed into urine, during which the level of Ag was concentrated >10-fold, resulting in the higher diagnosing sensitivity of urine Ag than serum Ag. Moreover, Ag in urine appeared 6 days earlier, lasted longer than viremia and antigenemia, and showed good concordance with fecal RNA in a rabbit model.

CONCLUSIONS

Our findings demonstrated the origin and diagnostic value of urine Ag and provided insights into the disposal of exogenous protein of pathogens by the host kidney.

Nanodiagnostics in leishmaniasis: A new frontiers for early elimination

Visceral leishmaniasis (VL) is still a major public health concern in developing countries having the highest outbreak and mortality potential. While the treatment of VL has greatly improved in recent times, the current diagnostic tools are limited for use in the post-elimination setting. Although conventional serological methods of detection are rapid, they can only differentiate between active disease in strict combination with clinical criteria, and thus are not sufficient enough to diagnose relapse patients. Therefore, there is a dire need for a portable, authentic, and reliable assay that does not require large space, specialized instrument facilities, or highly trained laboratory personnel and can be carried out in primary health care settings. Advances in the nanodiagnostic approaches have led to the expansion of new frontiers in the concerned area. The nanosized particles are blessed with an ability to interact one-on-one with the biomolecules because of their unique optical and physicochemical properties and high surface area to volume ratio. Biomolecular detection systems based on nanoparticles (NPs) are cost-effective, rapid, nongel, non-PCR, and nonculture based that provide fast, one-step, and reliable results with acceptable sensitivity and specificity. In this review, we discuss different NPs that are being used for the identification of molecular markers and other biomarkers, such as toxins and antigens associated with leishmaniasis. The most promising diagnostic approaches have been included in the article, and the ability of biomolecular recognition, advantages, and disadvantages have been discussed in detail to showcase the enormous potential of nanodiagnostics in human and veterinary medicine. This article is categorized under: Diagnostic Tools > Diagnostic Nanodevices Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Diagnostic Tools > Biosensing.

Urine-Based Antigen (Protein) Detection Test for the Diagnosis of Visceral Leishmaniasis

This review describes and appraises a novel protein-based antigen detection test for visceral leishmaniasis (VL). The test detects in patient’s urine six proteins from Leishmania infantum (chagasi) and Leishmania donovani, the etiological agents of VL. The gold standard test for VL is microscopic observation of the parasites in aspirates from spleen, liver, or bone marrow (and lymph node for dogs). Culture of the parasites or detection of their DNA in these aspirates are also commonly used. Serological tests are available but they cannot distinguish patients with active VL from either healthy subjects exposed to the parasites or from subjects who had a successful VL treatment. An antigen detection test based on the agglutination of anti-leishmania carbohydrates antibody coated latex beads has been described. However, the results obtained with this carbohydrate-based test have been conflicting. Using mass spectrometry, we discovered six L. infantum/L. donovani proteins excreted in the urine of VL patients and used them as markers for the development of a robust mAb-based antigen (protein) detection test. The test is assembled in a multiplexed format to simultaneously detect all six markers. Its initial clinical validation showed a sensitivity of 93% and specificity of 100% for VL diagnosis.

Isolation and characterisation of Leishmania donovani protein antigens from urine of visceral leishmaniasis patients

Diagnosis of visceral leishmaniasis (VL) relies on invasive and risky aspirate procedures, and confirmation of cure after treatment is unreliable. Detection of Leishmania donovani antigens in urine has the potential to provide both a non-invasive diagnostic and a test of cure. We searched for L. donovani antigens in urine of VL patients from India and Sudan to contribute to the development of urine antigen capture immunoassays. VL urine samples were incubated with immobilised anti-L. donovani polyclonal antibodies and captured material was eluted. Sudanese eluted material and concentrated VL urine were analysed by western blot. Immunocaptured and immunoreactive material from Indian and Sudanese urine was submitted to mass spectrometry for protein identification. We identified six L. donovani proteins from VL urine. Named proteins were 40S ribosomal protein S9, kinases, and others were hypothetical. Thirty-three epitope regions were predicted with high specificity in the 6 proteins. Of these, 20 were highly specific to Leishmania spp. and are highly suitable for raising antibodies for the subsequent development of an antigen capture assay. We present all the identified proteins and analysed epitope regions in full so that they may contribute to the development of non-invasive immunoassays for this deadly disease.

Urine-based antigen detection assay for diagnosis of visceral leishmaniasis using monoclonal antibodies specific for six protein biomarkers of Leishmania infantum / Leishmania donovani

The development of an accurate protein-based antigen detection assay for diagnosis of active visceral leishmaniasis (VL) would represent a major clinical advance. VL is a serious and fatal disease caused by the parasites Leishmania infantum and Leishmania donovani. The gold standard confirmatory diagnostic test for VL is the demonstration of parasites or their DNA from aspirates from spleen, lymph node, and bone marrow or from blood buffy coats. Here we describe the production and use of monoclonal antibodies (mAbs) for the development of a sensitive and specific antigen detection capture ELISA for VL diagnosis. This test simultaneously detects six leishmania protein biomarkers that we have previously described (Li-isd1, Li-txn1, Li-ntf2, Ld-mao1, Ld-ppi1 and Ld-mad1). The initial clinical validation of this new mAb-based multiplexed capture ELISA showed a sensitivity of ≥93%. The test was negative with 35 urine samples from healthy control subjects as well as with 30 patients with confirmed non-VL tropical diseases (cutaneous leishmaniasis, n = 6; Chagas disease, n = 6; schistosomiasis, n = 6; and tuberculosis, n = 12). These results strongly support the possible utility of this mAb-based multiplexed capture ELISA as a promising diagnostic test for active VL as well as for monitoring the treatment efficacy of this disease. The test is ready for upscaling and validation for clinical use.

Visceral leishmaniasis (VL) or kala-azar is a systemic parasitic disease that is endemic in 75 countries with more than 500 million people at risk of infection. VL is caused primarily by the parasites known as Leishmania infantum and Leishmania donovani. It is estimated that VL affects 50,000–90,000 people each year, with 90% of the cases occurring in India, Kenya, Somalia, Sudan, South Sudan and Brazil. VL is a fatal disease if not treated. Laboratory diagnosis of this disease can be performed using several different approaches. However, there is still a need for a simple, non-expensive, sensitive and specific test that can be used not only for the accurate diagnosis of this serious disease but also to monitor the efficacy of its treatment. Here we describe a new test that can circumvent most of the drawbacks of existing approaches. This new test detects six leishmanial proteins or biomarkers that are eliminated in the urine of patients with VL. The test is a conventional ELISA assembled with monoclonal antibodies (mAbs) specific for each of the six different biomarkers and it is performed in urine samples of suspected patients. An initial clinical validation demonstrated that the test has a sensitivity of ≥93% and specificity of 100%. This new and accurate mAb-based multiplexed assay could be a useful resource to diagnose most clinical forms and/or the severity of the disease e.g., active VL, asymptomatic VL, post kala-azar dermal leishmaniasis, VL/HIV co-infection, etc.

Noninvasive Biological Samples to Detect and Diagnose Infections due to Trypanosomatidae Parasites: A Systematic Review and Meta-Analysis

Unicellular eukaryotes of the Trypanosomatidae family include human and animal pathogens that belong to the Trypanosoma and Leishmania genera. Diagnosis of the diseases they cause requires the sampling of body fluids (e.g., blood, lymph, peritoneal fluid, cerebrospinal fluid) or organ biopsies (e.g., bone marrow, spleen), which are mostly obtained through invasive methods. Body fluids or appendages can be alternatives to these invasive biopsies but appropriateness remains poorly studied. To further address this question, we perform a systematic review on clues evidencing the presence of parasites, genetic material, antibodies, and antigens in body secretions, appendages, or the organs or proximal tissues that produce these materials. Paper selection was based on searches in PubMed, Web of Science, WorldWideScience, SciELO, Embase, and Google. The information of each selected article (n = 333) was classified into different sections and data were extracted from 77 papers. The presence of Trypanosomatidae parasites has been tracked in most of organs or proximal tissues that produce body secretions or appendages, in naturally or experimentally infected hosts. The meta-analysis highlights the paucity of studies on human African trypanosomiasis and an absence on animal trypanosomiasis. Among the collected data high heterogeneity in terms of the I2 statistic (100%) is recorded. A high positivity is recorded for antibody and genetic material detection in urine of patients and dogs suffering leishmaniasis, and of antigens for leishmaniasis and Chagas disease. Data on conjunctival swabs can be analyzed with molecular methods solely for dogs suffering canine visceral leishmaniasis. Saliva and hair/bristles showed a pretty good positivity that support their potential to be used for leishmaniasis diagnosis. In conclusion, our study pinpoints significant gaps that need to be filled in order to properly address the interest of body secretion and hair or bristles for the diagnosis of infections caused by Leishmania and by other Trypanosomatidae parasites.

Antigen Detection in Urine for Noninvasive Diagnosis and Treatment Monitoring of Visceral Leishmaniasis in Human Immunodeficiency Virus Coinfected Patients: An Exploratory Analysis from Ethiopia

Diagnosis of visceral leishmaniasis (VL) and assessment of treatment response in human immunodeficiency virus (HIV)–coinfected patients still relies on invasive tissue aspiration. This hampers scale-up and decentralization of care in resource-limited settings. Noninvasive diagnostics are urgently needed. KATEX is a frequently used latex agglutination test for Leishmania antigen in urine that has never been evaluated in HIV-coinfected individuals from Leishmania donovani–endemic areas. This was an exploratory sub-study embedded within the screening phase of a trial in highly endemic northwestern Ethiopia. All patients were HIV-positive and aspirate-confirmed VL cases. We assessed diagnostic accuracy of KATEX for VL diagnosis and as test of cure at end of treatment, using tissue aspirate parasite load as reference methods. We also described the evolution of weekly antigen levels during treatment. Most of the 87 included patients were male (84, 97%), young (median age 31 years), and had poor immune status (median cluster of differentiation type 4 count 56 cells/μL). KATEX had moderate sensitivity (84%) for VL diagnosis. KATEX had moderate sensitivity (82%) and a moderate negative predictive value (87%) but only low specificity (49%) and a low positive predictive value (40%) for the assessment of treatment outcomes. Weekly antigen levels showed characteristic patterns during treatment of patients with different initial parasite loads and treatment outcomes. Antigen detection in urine using KATEX can contribute to improved VL diagnosis in HIV-coinfected patients but has limited use for monitoring of treatment response. Better noninvasive diagnostics are needed to reduce reliance on invasive methods and thus to expand and improve clinical care for VL in resource-limited settings.

Development of a Multiplexed Assay for Detection of Leishmania donovani and Leishmania infantum Protein Biomarkers in Urine Samples of Patients with Visceral Leishmaniasis

Visceral leishmaniasis (VL) is a serious and fatal disease caused by the parasites Leishmania infantum and Leishmania donovani The gold standard diagnostic test for VL is the demonstration of parasites or their DNA in spleen, lymph node, or bone marrow aspirates. Serological tests exist but cannot distinguish active VL from either prior exposure to the parasites or previously treated VL disease. Using mass spectroscopy, we have previously identified three L. infantum protein biomarkers (Li-isd1, Li-txn1, and Li-ntf2) in the urine of VL patients and developed a sensitive and specific urine-based antigen detection assay for the diagnosis of VL that occurs in Brazil (where VL is caused by L. infantum). However, unpublished observations from our laboratory at DetectoGen showed that these biomarkers were detected in only 55% to 60% of VL patients from India and Kenya, where the disease is caused by L. donovani Here, we report the discovery and characterization of two new biomarkers of L. donovani (Ld-mao1 and Ld-ppi1) present in the urine of VL patients from these two countries. Capture enzyme-linked immunosorbent assays using specific rabbit IgG and chicken IgY were developed, and the assays had sensitivities of 44.4% and 28.8% for the detection of Ld-mao1 and Ld-ppi1, respectively. In contrast, a multiplexed assay designed to simultaneously detect all five leishmanial biomarkers markedly increased the assay sensitivity to 82.2%. These results validate the utility of leishmanial protein biomarkers found in the urine of VL patients as powerful tools for the development of an accurate diagnostic test for this disease.

Use of VHH antibodies for the development of antigen detection test for visceral leishmaniasis

We have recently developed a sensitive and specific urine‐based antigen detection ELISA for the diagnosis of visceral leishmaniasis (VL). This assay used rabbit IgG and chicken IgY polyclonal antibodies specific for the Leishmania infantum proteins iron superoxide dismutase 1 (Li‐isd1), tryparedoxin1 (Li‐txn1) and nuclear transport factor 2 (Li‐ntf2). However, polyclonal antibodies have limitations for upscaling and continuous supply. To circumvent these hurdles, we began to develop immortalized monoclonal antibodies. We opted for recombinant camelid VHHs because the technology for their production is well established and they do not have Fc, hence providing less ELISA background noise. We report here an assay development using VHHs specific for Li‐isd1 and Li‐ntf2. This new assay was specific and had analytical sensitivity of 15‐45 pg/mL of urine. The clinical sensitivity was comparable to that obtained with the ELISA assembled with conventional rabbit and chicken antibodies to detect these two antigens. Therefore, similar to our former studies with conventional antibodies, the future inclusion of VHH specific for Li‐txn1 and/or other antigens should further increase the sensitivity of the assay. These results confirm that immortalized VHHs can replace conventional antibodies for the development of an accurate and reproducible antigen detection diagnostic test for VL.

Immunodetection and molecular determination of visceral and cutaneous Leishmania infection using patients' urine

The diagnosis of leishmaniasis relies mainly on the use of invasive processes, to collect the biological material for detecting Leishmania parasites. Body fluids, which can be collected by non-invasive process, would greatly facilitate the leishmaniasis diagnosis. In the present study, we investigated the potency of urine immunoblotting to diagnose cutaneous and visceral leishmaniasis and we compared with routine molecular methods. A total of 80 samples, including 40 sera and their 40 corresponding urine samples were collected from 37 suspected patients with cutaneous and visceral leishmaniasis, and 3 healthy individuals (as control), in Ilam and Ardabil provinces of Iran. All sera and urine samples were analyzed, using immunoblotting. The confirmation of leishmaniasis infection was performed, using conventional and quantitative PCRs as well as by sequencing the amplicons. Among 37 suspected patients, 23 patients presented cutaneous lesions (CL) and 14 exhibited clinical symptoms reminiscent of visceral leishmaniasis (L. infantum). Among cutaneous patients, 15 were positive for zoonotic cutaneous leishmaniasis (L. major), and eight for anthroponotic cutaneous leishmaniasis (L. tropica). Molecular quantification of Leishmania parasites was performed on sera, urines and cutaneous biopsies of CL and VL patients, demonstrating that parasite load is lower in urines, compared to sera or biopsy. DNA can be detected in 20 out of 23 (86.9%) CL urine samples and in 13 out of 14 (92.8%) VL urine samples. Immunodetection analysis demonstrates that 22 out of 23 (95.6%) sera from CL patients and all patients suspected with VL are positive. For urine samples, 18 out of 23 (78.2%) urine of CL patients and 13 out of 14 (92.8%) urine of VL patients were positive, using Western blot. Therefore, immunodetection and molecular analysis using urine samples can be used as a diagnostic tool for surveying cutaneous and visceral leishmaniasis.

Is urine a reliable clinical sample for the diagnosis of human visceral leishmaniasis? A systematic review and meta-analysis

Visualization of amastigotes in lymph nodes, bone marrow, and other tissues samples remains the gold standard method for the diagnosis of visceral leishmaniasis (VL) in humans. This gold standard diagnostic method uses a technically challenging microscopy procedure that is often not accessible in many places in the world where VL is endemic. Here, we report the current systematic review and meta-analysis to evaluate whether urine is a reliable clinical sample for diagnosis of human VL. Data were extracted from ten available databases during the period from 2002 to 2017. Overall, 29 articles fulfilled the inclusion criteria and were used for data extraction in this systematic review. Most studies (72.4%) using urine specimens were reported from five countries: India 6 (20.7%), Iran 5 (17.2%), Bangladesh 4 (13.8%), Japan 3 (10.3%) and Spain 3 (10.3%), respectively. The most common diagnostic tests performed on urine were Katex (62.1%), ELISA (24.1%), and the rK39 (17.2%) assays. In meta-analysis the sensitivity and specificity of the three most commonly used diagnostic assays were rK39 (97%; CI: 91-99; 98%;76-100), ELISA (91%; 82-95; 99%; CI: 94-100), and Katex (83%; 73-90; 98%; 98-100), suggesting that the rK39 assay provided the highest sensitivity and the ELISA assay provided the highest specificity for diagnosis of VL from urine samples. Our findings suggest that urine is a valuable clinical sample for the diagnosis of human VL, particularly in areas where the gold standard test for VL is not available.

Discovery of a unique Mycobacterium tuberculosis protein through proteomic analysis of urine from patients with active tuberculosis

Identification of pathogen-specific biomarkers present in patients' serum or urine samples can be a useful diagnostic approach. In efforts to discover Mycobacterium tuberculosis (Mtb) biomarkers we identified by mass spectroscopy a unique 21-mer Mtb peptide sequence (VVLGLTVPGGVELLPGVALPR) present in the urines of TB patients from Zimbabwe. This peptide has 100% sequence homology with the protein TBCG_03312 from the C strain of Mtb (a clinical isolate identified in New York, NY, USA) and 95% sequence homology with Mtb oxidoreductase (MRGA423_21210) from the clinical isolate MTB423 (identified in Kerala, India). Alignment of the genes coding for these proteins show an insertion point mutation relative to Rv3368c of the reference H37Rv strain, which generated a unique C-terminus with no sequence homology with any other described protein. Phylogenetic analysis utilizing public sequence data shows that the insertion mutation is apparently a rare event. However, sera from TB patients from distinct geographical areas of the world (Peru, Vietnam, and South Africa) contain antibodies that recognize a purified recombinant C-terminus of the protein, thus suggesting a wider distribution of isolates that produce this protein.

Immunodiagnosis of Human Fascioliasis: An Update of Concepts and Performances of the Serological Assays

Human Fascioliasis (HF) is a foodborne neglected parasitic disease caused by Fasciola hepatica and Fasciola gigantica. New epidemiological data suggest that the endemic areas of the disease are expanding and HF is being reported from areas where it was previously not observed. Diagnosis of HF is challenging. Performances of parasitological approaches, based on the detection of parasite's egg in the stool, are not satisfactory. Currently serological methods for the diagnosis of HF are mainly based on detection of anti-Fasciola antibodies in serum. Although, there have been some improvement in the development of immunological diagnostic tests for the diagnosis of HF, yet these tests suffer from insufficiency in sensitivity or/and specificity. Detection of antigens, rather than antibodies, seems to be a suitable approach in the diagnosis of HF. Antigen can be detected in sera or stool of the fascioliasis patients. Circulating antigen in serum disappears within a short time and most of the circulating antigens are in immune complex forms which are not freely available to be detected. Therefore, antigenemia might not be an appropriate method for the diagnosis of HF. Detection of antigen in stool (coproantigens) seems to be a suitable alternative method for the diagnosis of HF. Recent data provided convincing evidence that detection of coproantigen improved and simplified the diagnosis of HF. The present review highlights the new achievements in designing and improvement of diagnostic approaches for the immunodiagnosis of HF. Moreover, current status of the available immunodiagnostic techniques for the diagnosis of HF, their strengths and weaknesses has been discussed.

Diagnosis of Mediterranean visceral leishmaniasis by detection of Leishmania-related antigen in urine and oral fluid samples

Implementation of simple diagnostic tests using non-invasive collection of biological specimens is of great importance in the diagnosis of pediatric visceral leishmaniasis caused by Leishmania infantum. Latex agglutination kit (KAtex^®) is widely used in the diagnosis mainly in L. donovani endemic areas. However its utilization in L. infantum endemic regions remains limited and its use on noninvasive biological specimen apart urine was not reported. In this study, KAtex^® kit was used to detect Leishmania-related antigen in urine and oral fluid of 35 L. infantum visceral leishmaniasis cases and 62 controls including non-infectious disease and infectious disease controls (34 and 28 respectively). Sensitivity and specificity of urine based KAtex^® were 51.4% and 98.3% respectively, whereas, sensitivity and specificity of oral-fluid based KAtex^® were 80% and 88.3% respectively. Although, sensitivity of oral-fluid KAtex^® was high, its specificity varied significantly according to the presence or the absence of an infectious disease (71.4% versus 97%, p=0.01).

Production of Monoclonal Antibody Against Excretory-Secretory Antigen of Fasciola hepatica and Evaluation of Its Efficacy in the Diagnosis of Fascioliasis

Parasitological methods are not helpful for the diagnosis of fascioliasis in acute and invasive periods of the disease. Detection of coproantigens seems to be a suitable alternative approach in the diagnosis of fascioliasis. The present study aimed to develop a reliable antigen detection system, using monoclonal antibodies raised against excretory-secretory (ES) antigen of Fasciola hepatica, for the diagnosis of fascioliasis. Fasciola adult worms were collected from the bile ducts of infected animals. Species of the fluke was determined by polymerase chain reaction-restriction fragment length polymorphism (RFLP-PCR). ES antigen of F. hepatica was prepared. For production of monoclonal antibodies, mice were immunized with ES antigens of F. hepatica. Spleen cells from the immunized mice were fused with NS-1 myeloma cells, using polyethylene glycol. Hybridoma cells secreting specific antibody were expanded and cloned by limiting dilution. Moreover, polyclonal antibody was produced against F. hepatica ES antigen in rabbits. A capture enzyme-linked immunosorbent assay (ELISA) system, using produced monoclonal antibody, was designed and stool samples of infected animals along with control samples were tested by the system. The capture ELISA detected the coproantigen in 27 of 30 (90%) parasitologically confirmed fascioliasis cases, while 4 of 39 (10.25%) samples infected with other parasitic infections showed a positive reaction in this system. No positive reactivity was found with healthy control samples. Accordingly, sensitivity of 90% and specificity of 94.2% were obtained for the capture ELISA system. The results were compared with those obtained with commercial BIO-X ELISA, and a very good (kappa = 0.9) agreement was found between the commercial kit and the developed capture ELISA. Findings of this study showed that the produced monoclonal antibody has appropriate performance for the detection of Fasciola coproantigen in stool samples and can be appropriately used for the diagnosis of fascioliasis.

Novel Antigen Detection Assay to Monitor Therapeutic Efficacy of Visceral Leishmaniasis

Visceral leishmaniasis (VL) diagnosis is routinely performed by invasive liver, spleen, bone marrow, or lymph node biopsies, followed by microscopic identification of the parasites. Conventional serological tests cannot distinguish active disease from asymptomatic VL or from cured infection. Here, we report the initial validation of an enzyme-linked immunosorbent assay (ELISA) assembled to detect the Leishmania infantum/donovani antigens iron superoxide dismutase 1 (Li-isd1), tryparedoxin 1 (Li-trx1), and nuclear transport factor 2 (Li-ntf2) as a tool to monitor therapeutic efficacy of VL. The assembled ELISA detected the antigens in the urine samples from seven VL patients before initiation of therapy. Importantly, the antigens were no longer detected in all patients after completion of the treatment. These preliminary observations point to a promising tool to follow treatment efficacy of VL.

Visceral Leishmaniasis in Southwestern Iran: A Retrospective Clinico-Hematological Analysis of 380 Consecutive Hospitalized Cases (1999-2014)

Visceral Leishmaniasis (VL) is an endemic parasitic disease and remains as a major health concern in southwestern Iran. The current study describes clinico-hematological, epidemiological and therapeutic features of VL cases, admitted to university-affiliated hospitals, during 1999–2014 in Fars province, southwestern Iran. A total of 380 VL cases were recorded during a 16 years period, giving an average annual admission of 23.75 cases/year in which 217 (57.1%) were male and 163 (42.9%) were female. Mean age of the patients was 3.7 years. The majority of the cases (91.5%) were ≤ 5 years old. Bone-marrow aspiration detected Leishmania amastigotes only in 26.6% of cases. Fever (98.1%), abdominal protrusion (65.1%) and hepatosplenomegaly (63.7%) were the most common clinical presentations of the patients. Pancytopenia was noted in 43.1, anemia in 87.3 and thrombocytopenia in 64% of cases. Increase in the level of AST (aspartate aminotransferase), ALT (alanine aminotransferase), alkaline phosphatase, LDH (lactate dehydrogenase) and CRP (C-Reactive Proteins) were seen in 84.9, 53.6, 44.4, 72.5 and 83.1% of cases, respectively. Mortality was noted in 5.3% of cases. Deranged haemato-biochemical parameters including total and direct bilirubin, PLT (platelet) and pancytopenia were significantly contributed to mortality from VL. Moreover, clinical features such as severe splenomegaly as well as bacterial infections were meaningfully contributed to death from VL. The majority of patients (74.9%) were treated with meglumine antimoniate. Amphotericin B was administrated in 59 of cases, 11 of them were initially treated with meglumine antimoniate with a shift to amphotericin B, because of treatment failure. Findings of the current study demonstrated that VL is present in southwest of Iran with a fairly continual rate during the last 16 years period. Deranged haemato-biochemical parameters along with severe splenomegaly contributed to mortality from VL.

Development and comparative evaluation of two antigen detection tests for Visceral Leishmaniasis

Background

Visceral leishmaniasis (VL) can be fatal without timely diagnosis and treatment. Treatment efficacies vary due to drug resistance, drug toxicity and co-morbidities. It is important to monitor treatment responsiveness to confirm cure and curtail relapse. Currently, microscopy of spleen, bone marrow or lymph node biopsies is the only definitive method to evaluate cure. A less invasive test for treatment success is a high priority for VL management.

Methods

In this study, we describe the development of a capture ELISA based on detecting Leishmania donovani antigens in urine samples and comparison with the Leishmania Antigen ELISA, also developed for the same purpose. Both were developed as prototype kits and tested on patient urine samples from Sudan, Ethiopia, Bangladesh and Brazil, along with appropriate control samples from endemic and non-endemic regions. Sensitivity and specificity were assessed based on accurate detection of patients compared to control samples. One- Way ANOVA was used to assess the discrimination capacity of the tests and Cohen’s kappa was used to assess their correlation.

Results

The Leishmania Antigen Detect™ ELISA demonstrated >90 % sensitivity on VL patient samples from Sudan, Bangladesh and Ethiopia and 88 % on samples from Brazil. The Leishmania Antigen ELISA was comparable in performance except for lower sensitivity on Sudanese samples. Both were highly specific. To confirm utility in monitoring treatment, urine samples were collected from VL patients at days 0, 30 and 180 post- treatment. For the Leishmania Antigen Detect™ ELISA, positivity was high at day 0 at 95 %, falling to 21 % at day 30. At day 180, all samples were negative, corresponding well with clinical cure. A similar trend was also seen for the Leishmania Antigen ELISA albeit; with lower positivity of 91 % at Day 0 and more patients, remaining positive at Days 30 and 180.

Discussion

The Leishmania Antigen Detect™ and the Leishmania Antigen ELISAs are standardized, user- friendly, quantitative and direct tests to detect Leishmania during acute VL as well as to monitor parasite clearance during treatment. They are a clear improvement over existing options.

Conclusion

The ELISAs provide a non-invasive method to detect parasite antigens during acute infection and monitor its clearance upon cure, filling an unmet need in VL management. Further refinement of the tests with more samples from endemic regions will define their utility in monitoring treatment.

Development of an Immunochromatographic Test for Diagnosis of Visceral Leishmaniasis Based on Detection of a Circulating Antigen

Background

Visceral leishmaniasis (VL) is a life-threatening disease caused by protozoan parasites of the Leishmania donovani complex. Early case detection followed by adequate treatment is essential to the control of VL. However, the available diagnostic tests are either invasive and require considerable expertise (parasitological demonstration of the parasite in tissue smears) or unable to distinguish between past and active infection (serological methods). Therefore, we aimed to develop a lateral flow assay in the form of an immunochromatographic test (ICT) device based on the detection of a circulating Leishmania antigen using monoclonal antibodies (mAbs).

Methodology/Principal Findings

mAbs were produced by fusion of murine myeloma cells with splenocytes isolated from a mouse immunized with L. donovani soluble crude antigen. Out of 12 cloned hybridoma cell lines, two secreted mAbs recognizing the same leishmanial protein. These mAbs were used to produce an ICT as a sandwich assay for the detection of circulating antigen in serum and blood samples. The ICT was evaluated with 213 serum samples from VL patients living in VL endemic areas in China, and with 156 serum samples from patients with other diseases as well as 78 serum samples from healthy donors. Sensitivity, specificity and diagnostic efficiency of the new ICT was 95.8%, 98.7% and 97.3%, respectively. Compared with a commercially available antibody detecting ICT, our antigen-based ICT performed slightly better.

Conclusion/Significance

The newly developed ICT is an easy to use and more accurate diagnostic tool which fulfils the performance and operational characteristics required for VL case detection under field and laboratory conditions. As our ICT detects a circulating antigen, it will also be useful in monitoring treatment success and diagnosing VL in immunocompromised patients.

Visceral leishmaniasis is a neglected disease caused by different species of protozoan parasites of the genus Leishmania. The disease is endemic in 61 countries, and in many of them it poses a serious public health issue. As visceral leishmaniasis is fatal if left untreated, early diagnosis is essential for treatment and control of the disease. Current available diagnostic tests are either difficult to carry out under field conditions or insufficiently accurate. In this study we developed a new diagnostic test which detects a circulation parasite-derived antigen in serum or blood samples of patients with visceral leishmaniasis. We found that our test performed better than most other tests based on the detection of parasite-specific antibodies. In addition, as our test is a device for the detection of an acute infection, it will be useful to validate treatment and in the diagnosis of the disease in patients with deficient antibody production (as in AIDS patients).

Systematic review of biomarkers to monitor therapeutic response in leishmaniasis

Recently, there has been a renewed interest in the development of new drugs for the treatment of leishmaniasis. This has spurred the need for pharmacodynamic markers to monitor and compare therapies specifically for visceral leishmaniasis, in which the primary recrudescence of parasites is a particularly long-term event that remains difficult to predict. We performed a systematic review of studies evaluating biomarkers in human patients with visceral, cutaneous, and post-kala-azar dermal leishmaniasis, which yielded a total of 170 studies in which 53 potential pharmacodynamic biomarkers were identified. In conclusion, the large majority of these biomarkers constituted universal indirect markers of activation and subsequent waning of cellular immunity and therefore lacked specificity. Macrophage-related markers demonstrate favorable sensitivity and times to normalcy, but more evidence is required to establish a link between these markers and clinical outcome. Most promising are the markers directly related to the parasite burden, but future effort should be focused on optimization of molecular or antigenic targets to increase the sensitivity of these markers. In general, future research should focus on the longitudinal evaluation of the pharmacodynamic biomarkers during treatment, with an emphasis on the correlation of studied biomarkers and clinical parameters.

Use of a novel chagas urine nanoparticle test (chunap) for diagnosis of congenital chagas disease

Background

Detection of congenital T. cruzi transmission is considered one of the pillars of control programs of Chagas disease. Congenital transmission accounts for 25% of new infections with an estimated 15,000 infected infants per year. Current programs to detect congenital Chagas disease in Latin America utilize microscopy early in life and serology after 6 months. These programs suffer from low sensitivity by microscopy and high loss to follow-up later in infancy. We developed a Chagas urine nanoparticle test (Chunap) to concentrate, preserve and detect T. cruzi antigens in urine for early, non-invasive diagnosis of congenital Chagas disease.

Methodology/Principal Findings

This is a proof-of-concept study of Chunap for the early diagnosis of congenital Chagas disease. Poly N-isopropylacrylamide nano-particles functionalized with trypan blue were synthesized by precipitation polymerization and characterized with photon correlation spectroscopy. We evaluated the ability of the nanoparticles to capture, concentrate and preserve T. cruzi antigens. Urine samples from congenitally infected and uninfected infants were then concentrated using these nanoparticles. The antigens were eluted and detected by Western Blot using a monoclonal antibody against T. cruzi lipophosphoglycan. The nanoparticles concentrate T. cruzi antigens by 100 fold (western blot detection limit decreased from 50 ng/ml to 0.5 ng/ml). The sensitivity of Chunap in a single specimen at one month of age was 91.3% (21/23, 95% CI: 71.92%–98.68%), comparable to PCR in two specimens at 0 and 1 month (91.3%) and significantly higher than microscopy in two specimens (34.8%, 95% CI: 16.42%–57.26%). Chunap specificity was 96.5% (71/74 endemic, 12/12 non-endemic specimens). Particle-sequestered T. cruzi antigens were protected from trypsin digestion.

Conclusion/Significance

Chunap has the potential to be developed into a simple and sensitive test for the early diagnosis of congenital Chagas disease.

Congenital Chagas disease is one of the main pillars for the control of Chagas disease because 25% of new infections occur by this route. Conventional diagnosis of congenital Chagas disease is based on microscopy at birth and serology at 9 months. However microscopy misses many infections and many at-risk infants fail to complete serology at six to nine months. We have developed a Chagas urine nanoparticle test (Chunap) for concentration and detection of T. cruzi antigens. Chunap was evaluated in urine samples of 1-month old children. At this age children have the highest levels of parasitemia and therefore also excrete the highest levels of antigen. Parents prefer a urine test to having their baby's blood drawn. Chunap diagnosed congenital infection in a single urine sample as well as PCR in two blood samples. This study also shows that hydrogel/trypan blue particles used in our test efficiently capture, concentrate and protect urinary T. cruzi antigens from enzymatic degradation. Chunap allows for the early diagnosis of congenital Chagas disease, and with appropriate adaptation, may allow early point-of-care intervention.

Significantly lower anti-Leishmania IgG responses in Sudanese versus Indian visceral leishmaniasis

BACKGROUND

Visceral leishmaniasis (VL), a widely distributed systemic disease caused by infection with the Leishmania donovani complex (L. donovani and L. infantum), is almost always fatal if symptomatic and untreated. A rapid point-of-care diagnostic test for anti-Leishmania antibodies, the rK39-immunochromatographic test (rK39-ICT), has high sensitivity and specificity in South Asia but is less sensitive in East Africa. One of the underlying reasons may be continent-specific molecular diversity in the rK39 antigen within the L. donovani complex. However, a second reason may be differences in specific IgG anti-Leishmania levels in patients from different geographical regions, either due to variable antigenicity or immunological response.

METHODOLOGY/PRINCIPAL FINDINGS

We determined IgG titres of Indian and Sudanese VL patients against whole cell lysates of Indian and Sudanese L. donovani strains. Indian VL patients had significantly higher IgG titres against both L. donovani strains compared to Sudanese VL patients (p<0.0001). Mean reciprocal log10 50% end-point titres (1/log10t50) were i) 3.80 and 3.88 for Indian plasma and ii) 2.13 and 2.09 for Sudanese plasma against Indian and Sudanese antigen respectively (p<0.0001). Overall, the Indian VL patients therefore showed a 46.8-61.7 -fold higher mean ELISA titre than the Sudanese VL patients. The higher IgG titres occurred in children (<16 years old) and adults of either sex from India (mean 1/log10t50: 3.60-4.15) versus Sudan (mean 1/log10t50: 1.88-2.54). The greatest difference in IgG responses was between male Indian and Sudanese VL patients of ≥ 16 years old (mean 1/log10t50: 4.15 versus 1.99 = 144-fold (p<0.0001).

CONCLUSIONS/SIGNIFICANCE

Anti-Leishmania IgG responses among VL patients in Sudan were significantly lower than in India; this may be due to chronic malnutrition with Zn(2+) deficiency, or variable antigenicity and capacity to generate IgG responses to Leishmania antigens. Such differential anti-Leishmania IgG levels may contribute to lower sensitivity of the rK39-ICT in East Africa.

[Leishmania epidemiology, diagnosis, chemotherapy and vaccination approaches in the international network of Pasteur Institutes]

Protozoan parasites of the genus Leishmania generate severe human diseases termed leishmaniases. Due to their frequency and the severity of certain clinical forms, these diseases represent a major public health problem and limit the economic growth in various developing countries. The presence of Pasteur Institutes in countries with endemic leishmaniasis has provided important incentives to develop a strong public health agenda in the Pasteur scientific community with respect to this important disease. A concerted effort is now coordinated through the recently created LeishRIIP platform (www.leishriip.org), which aims to identify synergies and complementary expertise between the eleven members of the international network of Pasteur Institutes working on various aspects of the disease including epidemiology, diagnosis, chemotherapy and vaccination.

Optimization of single-tube nested PCR for the diagnosis of visceral leishmaniasis

Conventional nested PCR is a very sensitive and specific method for the diagnosis of visceral leishmaniasis. However, this type of PCR is notorious for contamination problems related to the processing of the product between the first and the second PCR steps. In order to have a PCR method that is just as efficient but without the risk of contamination, we attempted the optimization of a single-tube nested PCR (STNPCR) method. During the first and the second PCR steps, we used the small subunit of ribosomal RNA (ssu rRNA) and the ribosomal internal transcribed spacer (ITS) as targets, respectively. The performances of STNPCR and nested PCR in detecting the DNA of Leishmania chagasi were compared. In the case of STNPCR, the inner primers were immobilized on the interior of the tube cap by means of adsorption microtubes and then were solubilized before the second reaction. This procedure eliminated the need to open the microtube, which could have led to false-positive results through cross-contamination. The detection limit for the purified L. chagasi DNA was 1 fg by using nested PCR and 10 fg by using STNPCR. We also tested the specificity of the system against other parasites, and observed that Trypanosoma cruzi DNA was amplified with a detection limit of up to 1 pg. This study not only presents a promising tool for the diagnosis of visceral leishmaniasis, but also provides a new tool for the diagnosis of Chagas disease, either in mono-infection by T. cruzi or in co-infection with Leishmania spp.

Identification of Leishmania infantum chagasi proteins in urine of patients with visceral leishmaniasis: a promising antigen discovery approach of vaccine candidates

Visceral leishmaniasis (VL) is a serious lethal parasitic disease caused by Leishmania donovani in Asia and by Leishmania infantum chagasi in southern Europe and South America. VL is endemic in 47 countries with an annual incidence estimated to be 500,000 cases. This high incidence is due in part to the lack of an efficacious vaccine. Here, we introduce an innovative approach to directly identify parasite vaccine candidate antigens that are abundantly produced in vivo in humans with VL. We combined RP-HPLC and mass spectrometry and categorized three L. infantum chagasi proteins, presumably produced in spleen, liver and bone marrow lesions and excreted in the patients' urine. Specifically, these proteins were the following: Li-isd1 (XP_001467866.1), Li-txn1 (XP_001466642.1) and Li-ntf2 (XP_001463738.1). Initial vaccine validation studies were performed with the rLi-ntf2 protein produced in Escherichia coli mixed with the adjuvant BpMPLA-SE. This formulation stimulated potent Th1 response in BALB/c mice. Compared to control animals, mice immunized with Li-ntf2+ BpMPLA-SE had a marked parasite burden reduction in spleens at 40 days post-challenge with virulent L. infantum chagasi. These results strongly support the proposed antigen discovery strategy of vaccine candidates to VL and opens novel possibilities for vaccine development to other serious infectious diseases.

ELISA and western blotting for the detection of Hsp70 and Hsp83 antigens of Leishmania donovani

Visceral leishmaniasis (VL) is endemic in the tropical, sub-tropical regions of Asia, Africa, the Mediterranean, Southern Europe and South and Central America. Approximately 500,000 new cases are reported annually. Classically the diagnosis of VL is confirmed by the demonstration of the parasite in aspirates of spleen, bone marrow or liver which can yield false negative results, also these methods are invasive. In this study, we aimed to evaluate the serodiagnostic potential of two heat shock proteins (Hsps) i.e. Hsp70 and Hsp83 in combination by ELISA and western blotting in mouse model. Parasite proteins were separated by SDS-PAGE and transferred to PVDF membranes which were further incubated with serum samples of infected mice for visualizing different bands. Both the bands i.e. Hsp70 and Hsp83 were simultaneously visualized in all infected groups on different post infection days. The presence of both the antigens was also detected by sandwich ELISA. The results suggest that the simultaneous occurrence of both the antigens Hsp70 and Hsp83 may be useful in serodiagnostic assay of VL as it may reduce the need for traumatic bone marrow sampling and risky spleen aspiration.

Detection and diagnostic applicability of human urinary kininogen in kala-azar patients

The present study was aimed to detect urinary proteins excreted in kala-azar patients. Urinary proteins were isolated by ammonium sulfate precipitation and purified by Amicon ultra using 3 kDa cutoff membrane device. The proteins were resolved on 12% sodium dodecyl sulfate polyacrylamide gel electrophoresis and blots were developed with the patients sera. The excretion of urinary proteins was differential in kala-azar patients. A total eight proteins of molecular weights 25, 28, 46, 54, 57, 60, 72, and 95 kDa were detected in the urine of visceral leishmaniasis (VL) patients. On blot, the 57 kDa protein was found to be host origin and characterized as human kininogen. All other proteins were leishmanial origin. Out of 50 urine samples analyzed, the kininogen was detected in 45 urine samples. Following treatment, this protein was not detectable in the urine samples of any patient. The appearance of kininogen in urine of VL patients offers a novel possibility for the development of diagnostic tool and a test of cure.

Identification and diagnostic utility of Leishmania infantum proteins found in urine samples from patients with visceral leishmaniasis

Despite the clear need to control visceral leishmaniasis (VL), the existing diagnostic tests have serious shortcomings. Here, we introduce an innovative approach to directly identify Leishmania infantum antigens produced in vivo in humans with VL. We combined reverse-phase high-performance liquid chromatography (RP-HPLC) with mass spectrometry and categorized three distinct L. infantum proteins presumably produced in bone marrow/spleen/liver and excreted in the urine of patients with VL. The genes coding for these proteins (L. infantum iron superoxide dismutase, NCBI accession number XP_001467866.1; L. infantum tryparedoxin, NCBI accession number XP_001466642.1; and L. infantum nuclear transport factor 2, NCBI accession number XP_001463738.1) were cloned, and the recombinant molecules were produced in Escherichia coli. Antibodies to these proteins were produced in rabbits and chickens and were used to develop a capture enzyme-linked immunosorbent assay (ELISA) designed to detect these L. infantum antigens in the urine of VL patients. Specificity of the antibodies was confirmed by a Western blot analysis using both recombinant proteins and whole parasite extract. Importantly, a urinary antigen detection assay assembled with pairs of antibodies specific for each of these antigens identified 17 of 19 patients with VL. These results indicate that an improved antigen detection assay based on L. infantum proteins present in the urine of patients with VL may represent an important new strategy for the development of a specific and accurate diagnostic test that has the potential to both distinguish active VL from asymptomatic infection and serve as an important tool to monitor therapy efficacy.

Urine antigen detection by latex agglutination test for diagnosis and assessment of initial cure of visceral leishmaniasis

This prospective study evaluated the usefulness of the kala-azar latex agglutination test (KAtex) for the diagnosis and laboratory assessment of initial cure of visceral leishmaniasis (VL) (or kala-azar) patients following 30 days of sodium antimony gluconate treatment at Rajshahi Medical College Hospital (Bangladesh). KAtex detects a low molecular weight, heat-stable, carbohydrate antigen in the urine of VL patients. KAtex was performed using freshly voided urine samples obtained from 36 parasitologically confirmed cases of VL before and after treatment as well as from 40 healthy controls (20 each from kala-azar-endemic and non-endemic zones). KAtex was found to be positive in 27 (75%) of the 36 patients at diagnosis and was negative in all the controls. The diagnostic sensitivity and specificity of KAtex were 75% (95% CI 57-87%) and 100% (95% CI 89-100%), respectively. Following treatment, all 36 VL cases were negative for Leishman-Donovan bodies by splenic smear microscopy and 34 (94.4%) were negative by KAtex. This limited study suggests that KAtex is a satisfactorily sensitive, highly specific, rapid and completely non-invasive urine-based antigen detection test for the diagnosis of VL. Currently, this is the only non-invasive laboratory tool useful for the assessment of initial cure in VL patients.

Manifestations of paediatric Leishmania infantum infections in Malta

Leishmania infantum is endemic in the Maltese archipelago, a group of islands in the Mediterranean which are visited frequently by tourists from Northern European countries. The burden of leishmaniasis is highest in children who may present with cutaneous or visceral manifestations. We describe systematically the manifestations, diagnosis and management of leishmaniasis in children <14 years of age, who had a histopathological diagnosis of leishmaniasis in Malta, from 2004 to 2008. Eleven children were diagnosed with leishmaniasis; 8 children (15–44 months of age) had visceral disease and three (aged 9–13 years) suffered cutaneous infections. Prolonged high grade fever, pallor, hepatosplenomegaly, and pancytopenia were common presenting features of visceralisation. Diagnosis was based on the visualisation of amastigotes from bone marrow aspirates. Pentavalent antimonials were associated with treatment failure in two children, whilst liposomal amphotericin B was curative in all. Children with cutaneous leishmaniasis had dry crusted ulcero-nodular lesions on exposed areas which responded to intra-lesional instillation of sodium stibogluconate or to cryotherapy. Leishmaniasis should be included in the differential diagnosis of fever and hepatosplenomegaly or chronic cutaneous lesions in children who travel to Malta.

Evaluation of rK-39 strip test using urine for diagnosis of visceral leishmaniasis in an endemic area in Bangladesh

Diagnosis of visceral leishmaniasis (VL) by demonstration of parasites in tissue smears obtained from bone marrow, spleen or lymph nodes is risky, painful, and difficult. The rK-39 strip test is widely used for the diagnosis of VL using blood/serum samples in endemic countries. The aim of the study was to evaluate the rK-39 strip test using urine sample as a non-invasive means for the diagnosis of VL. The rk-39 strip test was performed using urine from 100 suspected VL cases along with 25 disease control (malarial febrile cases) and 50 healthy control (from endemic and non-endemic areas). All the VL suspected cases were positive with the rK-39 strip test using serum. The sensitivity and specificity of the rK-39 strip test using urine samples was 95% and 93.3%, respectively, compared to serum based rK-39 test. The findings suggest that the urine based rK-39 test could be a practical and efficient tool for the diagnosis of VL patients in rural areas, particularly where resources are limited.

Diagnosis of visceral leishmaniasis

Leishmaniasis is a vector-borne disease with up to 350 million people at risk of infection worldwide. Among its different clinical manifestations, visceral is the most severe form. Since clinical features of visceral leishmaniasis (VL) mimic several other common diseases, accurate diagnosis is crucial as the treatment is associated with significant toxicity. Invasive and risky techniques involving demonstration of the parasites in stained preparations from splenic and bone marrow aspirate is still the gold standard for VL diagnosis. Serological tests using rK39 in ELISA or rapid immunochromatographic format, Direct Agglutination Test (DAT), immunoblotting have issues related to a significant proportion of asymptomatic individuals being positive with these tests and their inability to diagnose relapses as these remain positive for several months to years after cure. PCR is the most common molecular technique successfully used for diagnosis and differentiation of species. Through this review we focus extensively on the comparative utilities of the various diagnostic tools currently available for VL, describing in depth their advantages and disadvantages, addressing the recent advances attained in the field. A simple, rapid, non invasive, accurate and cost effective marker of active VL, which can be used in field conditions, is necessary to improve diagnosis of VL.

Epitope mapping of a common 57 kDa antigen of Leishmania species by monoclonal antibodies

BALB/c mice were immunized with freeze-thawed promastigote of Leishmania infantum. Five monoclonal antibodies (mAb) were selected, four IgM (designated as P1A9, P2G8, P5E3 and P6B3) and one IgG1 (P3D2). ELISA and Western blot analysis suggested that all monoclonal antibodies are specific to a band of 57 kDa antigen of L. infantum as well as other three Leishmania species (L. tropica, L. major and L. donovani). ELISA additivity tests revealed four epitopes on 57 kDa antigen as defined by four IgM monoclonal antibodies. Three distinct epitopes were recognized by P1A9, P2G8, and P6B3 antibodies and one epitope recognized by P5E3 antibody that shared with P2G8, and P6B3 epitopes. The 57 kDa protein was purified with affinity column and was shown to possess proteolytic activity. It seems that 57 kDa protein is the major surface Leishmania antigen (gp63) that has been used as subunit vaccine with appropriate adjuvant and induced protection against L. major infection in BALB/c mice.

Improvement of the newly developed latex agglutination test (Katex) for diagnosis of visceral lieshmaniasis

INTRODUCTION

Different methods are available for diagnosis of visceral leishmaniasis (VL), among them the urine-based antigen detection assay, latex agglutination test (Katex), is a recently developed one. The main drawback of the test is false-positive reactivity in some of healthy individuals. The false positivity of the test can be removed by boiling the urine sample for 5 min before testing. In this study an attempt was made to improve Katex by removing unpleasant boiling process, which also decreases field applicability of the test.

METHODS

False-positive and true-positive urine samples were collected from VL patients and healthy individuals. Both samples were then treated by reagents including, sodium dodecyl sulfate, trichloroacetic acid, dithiothreitol (DTT), sulphosalicylic acid and also heating at 56 degrees C.

RESULTS

Findings of this study showed that DTT pretreatment significantly reduced the rate of false-positive reactivity of Katex where 73% of false-positive urine samples changed to negative after DTT treatment. However, the DTT treatment reduced the rate of true positivity by 14%.

CONCLUSION

These data indicate that DTT can be used to eliminate nonspecific reactivity in the Katex. This will improve the performance of Katex and make it a more convenient and field applicable test.

Diagnostic tests for kala-azar: a multi-centre study of the freeze-dried DAT, rK39 strip test and KAtex in East Africa and the Indian subcontinent

Three diagnostic tests for visceral leishmaniasis (VL), the freeze-dried direct agglutination test (FD-DAT), the rK39 dipstick and a urine latex antigen test (KAtex), were evaluated for use in primary care in East Africa and the Indian subcontinent. Clinical suspects were prospectively recruited and tissue, blood and urine samples were taken. Direct microscopic examination of tissue smear, and FD-DAT, rK39 and KAtex were performed. Sensitivity and specificity with 95% credible intervals were estimated using Bayesian latent class analysis. On the Indian subcontinent both the FD-DAT and the rK39 strip test exceeded the 95% sensitivity and 90% specificity target, but not so in East Africa. Sensitivity of the FD-DAT was high in Ethiopia and Kenya but lower in Sudan, while its specificity was below 90% in Kenya. Sensitivity of the rK39 was below 80% in the three countries, and its specificity was only 70% in Ethiopia. KAtex showed moderate to very low sensitivity in all countries. FD-DAT and rK39 can be recommended for clinical practice on the Indian subcontinent. In East Africa, their clinical use should be carefully monitored. More work is needed to improve existing formats, and to develop better VL diagnostics.

Chemotherapy in the treatment and control of leishmaniasis

Drugs remain the most important tool for the treatment and control of both visceral and cutaneous leishmaniasis. Although there have been several advances in the past decade, with the introduction of new therapies by liposomal amphotericin, oral miltefosine and paromomycin (PM), these are not ideal drugs, and improved shorter duration, less toxic and cheaper therapies are required. Treatments for complex forms of leishmaniasis and HIV co-infections are inadequate. In addition, full deployment of drugs in treatment and control requires defined strategies, which can also prevent or delay the development of drug resistance.

Use of noninvasive markers to detect Leishmania infection in asymptomatic human immunodeficiency virus-infected patients

Visceral leishmaniasis (VL) caused by Leishmania infantum is a common disease in human immunodeficiency virus (HIV)-infected people in the Mediterranean basin. However, most such cases are asymptomatic, and little information about the prevalence of these infections in HIV-infected individuals is available. The aim of this study was to assess the prevalence of subclinical infection and the relationship between several Leishmania infection markers by noninvasive methods in asymptomatic HIV-infected patients from Southern Spain. Ninety-two HIV-infected patients, who were consecutively attended at the participant hospitals in 2004, were invited to participate in this study. These patients were asymptomatic and without any history of cutaneous or visceral leishmaniasis. Leishmania kinetoplast DNA (kDNA) was amplified from peripheral blood samples from 28 (30.4%) of these HIV-infected subjects. Sera from three (3.5%) patients tested positive for Leishmania by an enzyme-linked immunoassay. Two patients (2.4%) showed a specific 16-kDa band by Western blotting. In contrast, none of the patients showed a positive agglutination of urine. The leishmanin skin test was positive for four (4.3%) patients. None of the patients with a PCR-positive result showed a positive reaction by enzyme-linked immunoassay or by specific bands in Western blotting or had a positive leishmanin skin test. In conclusion, L. infantum kDNA was detected in a large proportion of asymptomatic HIV-infected patients, although a demonstrable cellular or humoral immune response to this parasite was not shown. Conversely, Leishmania antigen in urine was not detected in these patients.

Refinement of techniques for the propagation of Leishmania donovani in hamsters

Improved animal models are urgently required for drug and vaccine development against visceral leishmaniasis. Here we report refinements to the hamster model of infection that reduce the severity of the disease as well as the number of animals required to maintain infection while improving parasite yields. A comparison between infection via the intracardiac and intraperitoneal routes showed that the less commonly used intraperitoneal route is the simpler and preferred method. The KAtex latex agglutination test for visceral leishmaniasis accurately detected Leishmania donovani antigen in hamster urine as early as 6 weeks post-inoculation. With modification, this assay could be an important tool in the evaluation of experimental drugs and vaccines.

Evaluation of a latex agglutination test (KAtex) for detection of Leishmania antigen in urine of patients with HIV-Leishmania coinfection: value in diagnosis and post-treatment follow-up

The usefulness of antigen detection in urine as an alternative tool for diagnosis of leishmaniasis and post-treatment follow-up in patients with Leishmania-HIV coinfection was evaluated with a latex agglutination test (KAtex; Kalon Biological, UK). Forty-nine HIV-infected patients with visceral leishmaniasis were included in the study. Antigen detection in urine (ADU) was positive in 42 of 49 (sensitivity, 85.7%) samples obtained during a primary episode. After treatment, a follow-up study in 23 patients was performed by simultaneous ADU and culture of peripheral blood mononuclear cells in 148 determinations. The two methods gave concordant results in 94 cases, 38 of which were positive and 56 negative. In five cases, ADU was negative and culture of peripheral blood mononuclear cells was positive: two of these cases corresponded to clinical relapses. In 49 cases, culture of peripheral blood mononuclear cells was negative and ADU was positive. In the absence of clinical symptoms, the detection of parasite antigens in 71 of 130 (54.6%) urine samples was not associated with clinical disease. The Kaplan-Meier estimates of the probability of relapse at 6, 12, 18, and 24 months were 16% (95%CI, 15-17%), 20% (95%CI, 18-22%), 31% (95%CI, 27-35%), and 71% (95%CI, 52-89%), respectively, in patients with a positive ADU result. In contrast, when ADU was negative, the probability of relapse was 5% at 6 months (95%CI, 2-8%) (only 2 of 11 patients who relapsed had a negative test). ADU by KAtex is appropriate for primary diagnosis of visceral leishmaniasis, for monitoring the efficacy of treatment, and for detection of subclinical infection.

Evaluation of a urinary antigen-based latex agglutination test in the diagnosis of kala-azar in eastern Nepal

BACKGROUND

We evaluated the diagnostic accuracy as well as the reproducibility of the urine latex agglutination test 'KAtex' in the diagnosis of kala-azar in patients recruited at a tertiary care centre in Dharan, Nepal, between November 2000 and January 2002.

METHODS

All patients presenting with fever of 2 weeks or more and splenomegaly were consecutively enrolled. Bone marrow and--if negative--spleen aspirates were examined for Leishmania donovani. Serum and urine samples were taken in duplicate for the Direct Agglutination Test (DAT) and KAtex. The reference laboratory determined sensitivity and specificity of KAtex. Reproducibility between both laboratories was assessed.

RESULTS

KAtex was performed on urine from 155 parasitologically confirmed kala-azar and 77 non-kala-azar cases (parasitology and DAT-negative). KAtex showed a sensitivity of 47.7% (74/155, 95% CI: 39.7-55.9) and a specificity of 98.7% (76/77, 95% CI: 93.0-100.0). Reproducibility of KAtex showed a kappa of 0.684 (P < 0.001, n = 232).

CONCLUSION

KAtex evaluation showed high specificity, low sensitivity and moderate reproducibility. A urine test for kala-azar could become a real breakthrough in kala-azar management if its reproducibility and sensitivity could be further improved.

Detection of antileishmanial IgG antibodies and Leishmania-specific antigens in sera from Yemeni patients with visceral leishmaniasis

As part of an attempt to develop an effective method for the serodiagnosis of visceral leishmaniasis (VL), the sera from 43 Yemeni cases of the disease were screened both for antileishmanial IgG antibodies and for Leishmania-specific antigens. Indirect ELISA and capture ELISA were used to test each serum for the antibodies and antigens, respectively. Sera from patients with diseases other than leishmaniasis (29 for the antibody-detection assays and 42 for the antigen-detection) and from apparently healthy volunteers were also tested. For each type of assay, the threshold for seropositivity was set three standard deviations above the mean absorbance value for the sera from the healthy volunteers. Thirty-seven of the 43 VL sera were found positive for Leishmania-specific IgG antibodies and 37 were found positive for Leishmania-specific antigens. The sensitivities of the antibody- and antigen-detection assays were both therefore 86%. The overall specificity of the antibody-detection ELISA (67%) was, however, slightly higher than that of the capture-ELISA (64%).