Serological diagnosis and prognostic of tegumentary and visceral leishmaniasis using a conserved Leishmania hypothetical protein

Accuracy of serological tests in diagnosing mucosal leishmaniasis

In this serum panel-based study, we evaluated the accuracy of serological tests originally developed for visceral leishmaniasis (VL), for diagnosis of mucosal leishmaniasis (ML). A total of five tests were evaluated, four of which are registered at the National Agency of Sanitary Surveillance (Agência Nacional de Vigilância Sanitária-ANVISA) (RIDASCREEN® Leishmania Ab from R-Biopharm AG., Leishmania ELISA IgG + IgM from Vircell S.L., IFI Leishmaniose Humana-BioManguinhos, and IT-LEISH® from Bio-Rad Laboratories, Inc.), and the other a direct agglutination test (DAT-LPC) prototype kit developed at Fiocruz. The panel was composed of 40 serum samples from patients with confirmed ML and 20 from patients with mucosal involvement and negative parasitological/molecular tests for leishmaniasis and confirmation of another etiology. All cases were treated from 2009 to 2016 in a referral center for leishmaniasis in Belo Horizonte, Minas Gerais, Brazil (Instituto René Rachou, Fiocruz). Diagnostic accuracy, based on the cut-off point for VL diagnosis, was 86.2% with RIDASCREEN® Leishmania Ab, 73.3% with Leishmania ELISA IgG + IgM, and 66.7% with IFI Leishmaniose Humana, while IT-LEISH® and DAT-LPC had the lowest accuracy (38.3%), despite high specificity (100% and 95%, respectively). New cut-off points defined with sera from ML patients improved accuracy from 86.2 to 89% (p = 0.64) and 73.3 to 88% (p = 0.04) for RIDASCREEN® Leishmania Ab and Leishmania ELISA IgG + IgM, respectively. Moreover, these tests presented greater sensitivity and immunoreactivity in patients with moderate/severe clinical ML forms. The data of this study suggest that ELISA assays can contribute to laboratory diagnosis, especially for patients with moderate or severe mucosal involvement.

Laboratory diagnostics for human Leishmania infections: a polymerase chain reaction-focussed review of detection and identification methods

Leishmania infections span a range of clinical syndromes and impact humans from many geographic foci, but primarily the world's poorest regions. Transmitted by the bite of a female sand fly, Leishmania infections are increasing with human movement (due to international travel and war) as well as with shifts in vector habitat (due to climate change). Accurate diagnosis of the 20 or so species of Leishmania that infect humans can lead to the successful treatment of infections and, importantly, their prevention through modelling and intervention programs. A multitude of laboratory techniques for the detection of Leishmania have been developed over the past few decades, and although many have drawbacks, several of them show promise, particularly molecular methods like polymerase chain reaction. This review provides an overview of the methods available to diagnostic laboratories, from traditional techniques to the now-preferred molecular techniques, with an emphasis on polymerase chain reaction-based detection and typing methods.

Evaluation from a B-cell epitope-based chimeric protein for the serodiagnosis of tegumentary and visceral leishmaniasis

The diagnosis of leishmaniasis presents problems due to the variable sensitivity and/or specificity of tests. In addition, high levels of anti-parasite antibodies can remain after treatment, making it difficult to conduct a prognostic follow-up of patients. In this context, it is necessary to identify new candidates to be examined for the sensitive and specific diagnosis of the disease. In the present study, four Leishmania proteins, previously shown as antigenic for tegumentary leishmaniasis (TL), were evaluated, and their linear specific B-cell epitopes were predicted and used to generate a new gene codifying chimeric protein called ChimB, which was cloned, and the recombinant version was expressed, purified, and evaluated in ELISA (Enzyme-Linked Immunosorbent Assay) to diagnose TL and visceral leishmaniasis (VL). A total of 220 human serum samples were used, and, when ChimB was used, results showed sensitivity, specificity, and positive and negative predictive values of 100% for the diagnosis of both diseases; however, when using peptides, the sensitivity values reached from 28.0% to 57.3% and specificity varied from 16.3% to 83.7%. A soluble Leishmania extract (SLA) showed sensitivity and specificity values of 30.7% and 45.9%, respectively. The area under the curve (AUC) value for ChimB was 1.0, while for synthetic peptides, this value reached between 0.502 and 0.635, whereas for SLA, the value was of 0.589. Serological assays using sera samples collected before and after treatment showed significant reductions in the anti-ChimB antibody levels after therapy, suggesting a prognostic role of this recombinant antigen. In conclusion, preliminary data suggest the use from ChimB as a potential candidate for the diagnosis and prognosis of leishmaniasis.

Sensitive and specific serodiagnosis of tegumentary leishmaniasis using a new chimeric protein based on specific B-cell epitopes of Leishmania antigenic proteins

Serological tests used for the diagnosis of tegumentary leishmaniasis (TL) presents problems, mainly related to their variable sensitivity and/or specificity, which can be caused by low levels of antileishmanial antibodies or by presence of cross-reactive diseases, respectively. In this context, the search for new antigenic candidates presenting higher sensitivity and specificity is urgently required. In the present study, the amino acid sequences of the LiHyT, LiHyD, LiHyV, and LiHyP proteins, which were previously showed to be antigenic in the visceral leishmaniasis (VL), were evaluated and eight B-cell epitopes were predicted and used for construction of gene codifying a chimeric protein called ChimLeish. The protein was expressed, purified and evaluated as a recombinant antigen in ELISA (Enzyme-Linked Immunosorbent Assay) for the diagnosis of TL. The own B cell epitopes used to construct the chimera were synthetized and also evaluated as antigens, as well as a soluble Leishmania braziliensis antigenic extract (SLA). Results showed that ChimLeish presented 100% sensitivity and specificity to diagnose TL, while synthetic peptides showed sensitivity varying from 9.1% to 90.9%, while specificity reached from 98.3% to 99.1%. SLA showed sensitivity and specificity of 18.2% and 98.3%, respectively. A preliminary prognostic evaluation showed that anti-ChimLeish IgG antibodies declined in significant levels, when serological reactivity was compared before and six months after treatment, suggesting also a possible prognostic role of this antigen for TL.

ChimLeish, a new recombinant chimeric protein evaluated as a diagnostic and prognostic marker for visceral leishmaniasis and human immunodeficiency virus coinfection

Visceral leishmaniasis (VL) is a neglected tropical disease of global importance caused by parasites of the genus Leishmania, and coinfection with human immunodeficiency virus (HIV) is common in countries where both diseases are endemic. In particular, widely used immunological tests for VL diagnosis have impaired sensitivity (Se) and specificity (Sp) in VL/HIV coinfected patients and there is also cross-reactivity with other endemic diseases, e.g., Chagas disease, malaria, and tuberculosis. To develop new antigens to improve the diagnosis of VL and VL/HIV coinfection, we predicted eight specific B-cell epitopes of four Leishmania infantum antigens and constructed a recombinant polypeptide chimera antigen called ChimLeish. A serological panel of 195 serum samples was used to compare the diagnostic capabilities of ChimLeish alongside the individual synthetic peptides. ChimLeish reacted with sera from all VL and VL/HIV coinfected patients [Se = 100%; Sp = 100%; area under the curve (AUC) = 1.0]. Peptides showed lower reactivities (Se = 76.8 to 99.2%; Sp = 67.1 to 95.7%; AUC between 0.87 and 0.98) as did a L. infantum antigenic preparation used as an antigen control (Se = 56.8%; Sp = 69.5%: AUC = 0.45). Notably, ChimLeish demonstrated a significant reduction (p < 0.05) of anti-ChimLeish antibodies after treatment and cure of a small number of patients. Although only a limited serological panel was tested, preliminary data suggest that ChimLeish should be evaluated in larger sample studies for the diagnosis of VL and VL/HIV coinfection.

Potential of recombinant LiHyQ, a novel Leishmania infantum protein, for the diagnosis of canine visceral leishmaniasis and as a diagnostic and prognostic marker for human leishmaniasis and human immunodeficiency virus co-infection: A preliminary study

Laboratory diagnosis of leishmaniasis shows variable efficacy in detecting infected mammalian hosts and there is a need to identify suitable antigens to improve the accuracy of diagnostic tests. In the present study, a L. infantum hypothetical protein called LiHyQ was evaluated for the diagnosis of tegumentary (TL) and visceral (VL) leishmaniasis using canine and human samples. A collection of dog sera (n=155) were tested and contained samples from asymptomatic (n=20) and symptomatic (n=25) VL animals, from healthy dogs living in endemic (n=25) or non-endemic (n=25) areas of disease, from Leish-Tec® vaccinated dogs (n=20) or from dogs infected with Ehrlichia canis (n=15), Babesia canis (n=10) and Trypanosoma cruzi (n=15). Sensitivity (Se), Specificity (Sp), Positive Predictive Value (PPV) and Negative Predictive Value (NPV) of 100% were observed for rLiHyQ with these samples, whereas the Se, Sp, PPV and NPV values with L. infantum Soluble Leishmania Antigen (SLA) preparation were 60.0%, 99.0%, 96.0% and 86.0%, respectively. A collection of human sera (n=305) were tested and contained samples from TL (n=50) and VL (n=40) patients, from VL/HIV co-infected patients (n=35), from patients infected with HIV alone (n=30), Chagas Disease (n=30), malaria (n=10), tuberculosis (n=10), paracoccidioidomycosis (n=15), leprosy (n=30) or aspergillosis (n=15); and from healthy subjects (n=40). Se, Sp, PPV and NPV values of 100% were observed for rLiHyQ with these samples, whereas the Se, Sp, PPV and NPV values with SLA were 58.0%, 76.0%, 50.0% and 82.0%, respectively. The antibody reactivity against the protein was compared with commercial kits, and the kappa index varied from 0.95 to 1.00 for rLiHyQ, and of 0.55 to 0.82 for the kits. In addition, the serological follow-up of treated patients showed a significant reduction in rLiHyQ-specific IgG antibody levels. All canine and human samples were tested at the same time using the same reagents, in order to reduce experimental variation and interference in data interpretation. In conclusion, our preliminary data suggest a diagnostic and prognostic role for rLiHyQ against leishmaniasis.

Serodiagnosis of canine leishmaniasis using a novel recombinant chimeric protein constructed with distinct B-cell epitopes from antigenic Leishmania infantum proteins

Visceral leishmaniasis (VL) is an important public health problem in the world, and control measures are insufficient to avoid the spread of this neglected disease. Dogs are important domestic reservoirs of Leishmania parasites in countries where VL is a zoonosis, representing a major source of infection between sand fly vectors and humans. In this context, a precise diagnosis of canine leishmaniasis (CanL) could help to reduce the number of human cases. Distinct approaches for the diagnosis of CanL have used recombinant proteins in serological assays. However, variable results of the antigens have been found, mainly to diagnosis asymptomatic cases. The present study used bioinformatics to select specific B-cell epitopes of four Leishmania infantum proteins, which had previously been proven to be antigenic in VL, aiming to produce a novel chimeric protein and to evaluate it for the diagnosis of CanL. Seven B-cell epitopes were identified and used to construct the chimera, which was analyzed in a recombinant format through an ELISA assay against a canine serological panel. A soluble Leishmania antigenic extract (SLA) was used as an antigen control. Results showed 100 % sensitivity and specificity for chimera, while when using SLA the values were 26.0 % and 96.4 %, respectively. The performance of chimera was compared with a commercial kit using asymptomatic and symptomatic dog sera, and the data showed that no false-negative result was found when the recombinant protein was used. However, when using the commercial kit, 40.0 % and 16.0 % of the false-negative results were found, respectively. In conclusion, the recombinant chimera showed an antigenic potential to be evaluated in new studies against a larger serological panel for the diagnosis of CanL.

Molecular Tracking of the Leishmania Parasite

With the Visceral Leishmaniasis/Kala-azar Elimination Program in South Asia in its consolidation phase, the focus is mainly on case detection, vector control, and identifying potential sources of infection. Accordingly, emphasis is presently on curbing transmission, which is potentially achievable by identification and elimination of potential reservoirs. The strongest contenders for being the disease reservoir are cases of Post Kala-azar Dermal Leishmaniasis (PKDL) which occurs in a minor proportion of individuals apparently cured of Visceral Leishmaniasis (VL). The demonstration of parasites in tissue aspirates despite being a risky and invasive process is the gold standard for diagnosis of VL, but is now being replaced by serological tests e.g., rK39 strip test and direct agglutination test. However, these antibody based tests are limited in their ability to diagnose relapses, detect cases of PKDL, and monitor effectiveness of treatment. Accordingly, detection of antigen or nucleic acids by polymerase chain reaction has been successfully applied for monitoring of parasite kinetics. This review article provides updated information on recent developments regarding the available antibody or antigen/nucleic acid based biomarkers for longitudinal monitoring of patients with VL or PKDL and emphasizes the need for availability of studies pertaining to quantification of treatment response or relapse.

Recent advances and new strategies in Leishmaniasis diagnosis

Leishmaniasis is a set of complex and multifaceted syndromes, with different clinical manifestations, caused by different species of the genus Leishmania spp. that can be characterized by at least four syndromes: visceral leishmaniasis (VL, also known as kala-azar), post-kala-azar dermal leishmaniasis (PKDL), cutaneous leishmaniasis (CL), and mucocutaneous leishmaniasis (MCL). Among the most serious clinical forms, VL stands out, which causes the death of around 59,000 people annually. Fast and accurate diagnosis in VL is essential to reduce the disease's morbidity and mortality. There are a large number of diagnostic tests for leishmaniasis, however they do cross-react with other protozoa and their sensitivity changes according to the clinical form of the disease. Thus, it is essential and necessary to provide a diagnosis that is sufficiently sensitive to detect asymptomatic infected individuals and specific to discriminate individuals with other infectious and parasitic diseases, thus enabling more accurate diagnostic tools than those currently used. In this context, the aim of this review is to summarize the conventional diagnostic tools and point out the new advances and strategies on visceral and cutaneous leishmaniasis diagnosis.

Biotechnological applications from a Leishmania amastigote-specific hypothetical protein in the canine and human visceral leishmaniasis

The treatment against visceral leishmaniasis (VL) presents problems, mainly related to the toxicity and/or high cost of the drugs. In this context, a rapid and precise diagnosis of the disease should be performed, mainly to treat patients as soon as possible, aiming to reduce the treatment time and the toxicity of the therapeutics. In the present study, the diagnostic role of an amastigote-specific Leishmania protein was evaluated in the canine and human VL. Results showed that the recombinant protein (called rLiHyJ) and one specific B cell epitope (called PeptJ) predicted from protein sequence presented high sensitivity and specificity values to diagnose canine and human disease, showing also a low reactivity against cross-reactive samples. The rA2 protein and a parasite antigenic extract showed variable sensitivity and/or specificity values in the ELISA experiments. A prognostic evaluation of protein and peptide in the human VL indicated that specific IgG antibodies significantly decreased after treatment, when compared to be values obtained before therapy. The in vitro immunogenicity using rLiHyJ in peripheral blood mononuclear cell (PBMC) cultures collected of such patients and healthy subjects suggested that the protein induced lymphoproliferation and high IFN-γ production in the stimulated cells. In conclusion, although preliminary, results suggest that rLiHyJ and PeptJ could present distinct biotechnological applications in the canine and human VL.

A Leishmania infantum hypothetical protein evaluated as a recombinant protein and specific B-cell epitope for the serodiagnosis and prognosis of visceral leishmaniasis

The serodiagnosis of visceral leishmaniasis (VL) presents problems related to the sensitivity and/or specificity of the tests. In this context, more refined antigens should be identified and applied for the improvement of disease diagnosis. In the present study, DNA with an encoding of a Leishmania infantum hypothetical protein, LiHyC, was cloned, and the recombinant protein was expressed, purified, and evaluated for the serodiagnosis of canine and human VL. In addition, a specific B-cell epitope present in the LiHyC sequence was predicted; the peptide was both synthetized and evaluated in the ELISA experiments. For comparison, commercial diagnostic kits were used against positive (VL hosts) and negative (healthy hosts) samples. Results showed that the recombinant protein (rLiHyC) and synthetic peptide (PeptC) were highly sensitive and specific to diagnose canine and human VL, with 100% sensitivity and specificity, while no false-positive or false-negative result was detected. When the DPP® CVL kit was used to identify canine samples, 44 and 52 of the 60 L. infantum-infected animals, without or with clinical signals of disease, respectively, were identified, while eight and four samples were considered as false-negatives, respectively. For human VL, an IT LEISH® kit was used, and 33 of the 40 VL patients were identified, while seven samples were considered to be false-negatives. Post-therapeutic serological follow-up testing sera samples from treated and untreated VL patients showed a significant drop in the anti-PeptC and anti-rLiHyC antibody levels, thus suggesting the feasibility to use the recombinant protein and/or synthetic peptide in future studies as diagnostic and/or prognostic markers for VL.

Place of Serology in the Diagnosis of Zoonotic Leishmaniases With a Focus on Visceral Leishmaniasis Due to Leishmania infantum

Leishmaniases are a group of parasitic diseases transmitted through the bite of female phlebotomine sandflies. Depending on the Leishmania species, the reservoirs can be humans (anthroponosis) or different animals (zoonosis). Zoonotic leishmaniasis present several clinical forms in function of the species involved: visceral leishmaniasis (VL), cutaneous leishmaniasis (CL), and muco-cutaneous leishmaniasis (MCL). The biological diagnosis is of utmost importance because the clinical features are not specific. In addition to parasitological and molecular biology (polymerase chain reaction, PCR) assays, serology is routinely used for the diagnosis of leishmaniasis. Indeed, although PCR is more sensitive than serological assays, its implementation is limited to referral laboratories and research centers. Therefore, serology is still a key element for their diagnosis. Here, we discuss the different serological assays available for the diagnosis of zoonotic leishmaniasis. We will review the enzyme-linked immunosorbent assay, immunofluorescence antibody test, immunochromatography test (ICT), direct agglutination test, and western blot as well as the different diagnostic strategies in function of the clinical form (VL, CL, and MCL). We will also discuss the place of serology for detecting asymptomatic carriers and for the follow-up of VL. Depending on the laboratory, different assays can be used, from ICT, which is appropriate for field testing, to a combination of serological tests to improve the sensitivity.

Evaluation of Leishmania infantum pyridoxal kinase protein for the diagnosis of human and canine visceral leishmaniasis

Visceral leishmaniasis (VL) is a highly neglected disease that is present in several countries worldwide. Present-day treatments against this disease are unsuitable, mainly due to the toxicity and/or high cost of drugs. In addition, the development of vaccines is still insufficient. In this scenario, a prompt VL diagnosis was deemed necessary, although sensitivity and/or specificity values of the tests have been. In this context, new antigenic candidates should be identified to be employed in a more precise diagnosis of canine and human VL. In this light, the present study evaluated the diagnostic efficacy of the Leishmania infantum pyridoxal kinase (PK) protein, applied in its recombinant version (rPK). In addition, one specific B-cell epitope derived of the PK sequence was predicted, synthetized, and evaluated as diagnostic marker. Results in ELISA tests showed that the antigens were highly sensitive to VL identification in dogs and human sera, presenting a low reactivity with VL-related disease samples. The recombinant A2 (rA2) protein and L. infantum antigenic preparation (SLA), used as controls, also proved to be highly sensitive in detecting symptomatic cases, although a low sensitivity was found when asymptomatic sera were analyzed. High cross-reactivity was also found when these antigens were evaluated against VL-related disease samples. The post-therapeutic serological follow-up showed that anti-rPK and anti-peptide IgG antibody levels decreased in significant levels after treatment. By contrast, the presence of high levels of the anti-rA2 and anti-SLA antibodies was still detected after therapy. In conclusion, rPK and its specific B-cell epitope should be considered for future studies as a diagnostic marker for canine and human VL.

American tegumentary leishmaniasis diagnosis using L. (V.) braziliensis fixed promastigotes: a comparative performance of serological tests and spontaneous cure identification

BACKGROUND

The present study aimed to demonstrate the applicability of a flow cytometry-based serology approach to identify spontaneous cure by the detection of immunoglobulin G, and also, the diagnosis and cure criterion by the IgG1 isotype in American Tegumentary Leishmaniasis - ATL caused by L. (V.) braziliensis. Also, a comparison between flow cytometry with the serological conventional technique was performed.

METHODS

Forty five individuals were included in study. They were assessed in two moments: First, 8 subjects spontaneously cured of ATL, 8 healthy individuals and 15 patients who had a positive diagnosis for ATL were selected before treatment to identify spontaneous cure by immunoglobulin G detection. Secondly, 14 patients who were positive for ATL were selected and had their blood collected before and 1, 2 and 5 years after treatment, respectively, for the diagnostic tests (ELISA and flow cytometry) and cure criterion evaluation using the IgG1 isotype.

RESULTS

The analysis of the mean percentage of positive fluorescent parasites (PPFP) along with the titration curves of IgG anti-fixed promastigotes of L.(V.)braziliensis, confirmed the applicability of this method for monitoring spontaneous cure in ATL with outstanding co-positivity (100%) and co-negativity (100%) performance indexes. Regarding the results of the comparison between flow cytometry and ELISA it was seen that there was a better accuracy of the first one in relation to the other. When IgG1 applicability was evaluated, it was observed that before treatment, 36.8% of the patients were negative; in patients 1 year post-treatment, 82.3%; 2 years post-treatment, 27.2% and in patients 5 years post-treatment, 87.5%. The overall analysis of the results suggests that flow cytometry can be applied to ATL detection, and that the use of IgG1 isotype has possibilities to contribute as a more specific diagnostic method.

CONCLUSIONS

Therefore, this area has great perspectives use for the diagnosis and cure criterion, and also it can be scaled up with the possibility to characterize the different clinical stages of the disease. Together, these findings demonstrate the applicability of a flow cytometry-based serology approach and opens up new avenues of research with this technique, such as the understanding the humoral response in ATL patients.

Recombinant Leishmania eukaryotic elongation factor-1 beta protein: A potential diagnostic antigen to detect tegumentary and visceral leishmaniasis in dogs and humans

The laboratorial diagnosis of leishmaniasis is based on parasitological methods, which are invasive, present high cost, require laboratorial infrastructure and/or trained professionals; as well as by immunological methods, which usually present variable sensitivity and/or specificity, such as when they are applied to identify asymptomatic cases and/or mammalian hosts presenting low levels of antileishmanial antibodies. As consequence, new studies aiming to identify more refined antigens to diagnose visceral (VL) and tegumentary (TL) leishmaniasis are urgently necessary. In the present work, the Leishmania eukaryotic elongation factor-1 beta (EF1b) protein, which was identified in L. infantum protein extracts by antibodies in VL patients' sera, was cloned and its recombinant version (rEF1b) was expressed, purified and tested as a diagnostic marker for VL and TL. The post-therapeutic serological follow-up was also evaluated in treated and untreated VL and TL patients, when anti-rEF1b antibody levels were measured before and after treatment. Results showed that rEF1b was highly sensitive and specific to diagnose symptomatic and asymptomatic canine VL, as well as human TL and VL. In addition, low cross-reactivity was observed when sera from healthy subjects or leishmaniasis-related diseases patients were tested. The serological follow-up showed also that rEF1b-specific antibodies declined significantly after treatment, suggesting that this protein could be also evaluated as a prognostic marker for human leishmaniasis.

Diagnostic accuracy of Enzyme-Linked Immunosorbent Assays to detect anti-Leishmania antibodies in patients with American Tegumentary Leishmaniasis: a systematic review

American Tegumentary leishmaniasis (ATL) is an infectious disease caused by several species of Leishmania . Even though the direct detection of parasites has low sensitivity, it is still the gold standard for the laboratory diagnosis of ATL. Recent studies have shown promising results of Enzyme-Linked Immunosorbent Assays ( ELISAs) using recombinant antigens. The aim of this study is to compare the accuracy of ELISAs using novel antigens with the standard ELISA based on soluble antigens of Leishmania (SLA) to diagnose ATL. Studies that analyzed patients with ATL and studies that evaluated the diagnostic accuracy of ELISAs using novel antigens and SLA were included. The Fourteen studies from PubMed, Regional Portal of the Virtual Health Library (BVS), Brazilian Society of Dermatology, Virtual Health Library (IBECS), Literature in the Health Sciences in Latin America and the Caribbean (LILACS), Medical Literature Analysis and Retrieval System Online (Medline), Elsevier Embase, Cochrane Library, The National Institute for Health and Care Excellence (NICE), and Cumulative Index to Nursing and Allied Health Literature (CINAHL) were included. The novel ELISA antigens showed a high sensitivity (93.8%-100%) and specificity (82.5-100%), a better diagnostic performance than SLA-based ELISAs (1-97.4% and 57.5-100%, respectively). Only 10 studies analyzed cross-reactions in serum samples from patients with Chagas disease, and only two studies reported a percentage of cross-reactivity. In this systematic review, the novel ELISA antigens showed better sensitivity and specificity with respect to SLA-based ELISAs. However, a meta-analysis should be performed to confirm this finding.

Systematic review on antigens for serodiagnosis of visceral leishmaniasis, with a focus on East Africa

Background

Accurate and accessible diagnosis is key for the control of visceral leishmaniasis (VL). Yet, current diagnostic tests for VL have severe limitations: they are invasive or not suitable as point of care (POC) test or their performance is suboptimal in East Africa. We analysed the antigens in the VL serodiagnostics development pipeline to identify shortcomings and to propose strategies in the development of an alternative POC test for VL in East Africa.

Objectives

The objective of this study was to identify and to analyse all antigens for VL serodiagnosis that have been published before 2018 in order to identify candidates and gaps in the pipeline for a new POC test in East Africa.

Methods

A systematic literature search was performed on PubMed for original research articles on Leishmania-specific antigens for antibody detection of VL in humans. From each article, the following information was extracted: the antigen name, test format and characteristics, its reported sensitivity and specificity and study cohort specifications.

Results

One hundred and seven articles containing information about 96 tests based on 89 different antigens were included in this study. Eighty six of these tests, comprising 80 antigens, were evaluated in phase I and II studies only. Only 20 antigens, all of which are native, contain a carbohydrate and/or lipid moiety. Twenty-four antigens, of which 7 are non-native, are composed of antigen mixtures. Nineteen tests, comprising 18 antigens, have been evaluated on East African specimens, of which only 2 (rK28 based immunochromatographic test and intact promastigote based indirect fluorescent antibody technique) consistently showed sensitivities above 94 and specificities above 97% in a phase III study and one in a phase II study (dot blot with SLA). Only rK28 is a non-native mixture of antigens which we consider suitable for further evaluation and implementation.

Conclusions

The development pipeline for an alternative serodiagnostic test for VL is almost empty. Most antigens are not sufficiently evaluated. Non-protein antigens and antigen mixtures are being neglected. We propose to expand the evaluation of existing antigen candidates and to investigate the diagnostic potential of defined non-native carbohydrate and lipid antigens for VL serodiagnosis in East Africa.

Visceral leishmaniasis is a potentially fatal disease that affects more than 20 000 people every year. Its diagnosis is difficult since the clinical symptoms are not specific and the existing diagnostic tests are not useful in limited resource countries or they a not accurate enough in East Africa. In this review we performed a systematic search of the published literature to analyse the potential candidate antigens in the pipeline for a new antibody detection test in East Africa. We found 96 tests based on 89 antigens. Eighty six of these tests were evaluated in a study design that is insufficient (phase I and II) to make conclusions on their performance in clinical practice. We found that the candidate antigens either lacked carbohydrate or lipid structures or are based on single antigens as opposed to mixtures or are extracted from the causative parasite itself, making them expensive and prone to variations. Considering that the most widely used diagnostic test does not detect all cases of visceral leishmaniasis in East Africa, we analysed how many of the candidate antigens were tested on East African specimens: We found that only 2 tests (rK28 based immunochromatographic test and the intact promastigote based indirect fluorescent antibody technique) that were tested in a phase III study and only one (dot blot with SLA) that was tested in a phase II study performed well according to our criteria. Due to the antigen characteristics we consider only the rK28 based test as suitable for further evaluation and implementation.

Diagnostic markers selected by immunoproteomics and phage display applied for the serodiagnosis of canine leishmaniosis

Canine leishmaniosis (CanL) is one of the most important parasitic diseases found in several countries worldwide. Dogs are considered important domestic reservoirs of the parasites, being relevant in the maintenance of transmission cycle of the disease between sandflies and humans. However, the prevalence of asymptomatic infection is considerably higher than that of apparent clinical illness in the infected animals; thus making promptly necessary to diagnose the infection in these animals, which could help to allow to the adoption of more efficient control measures against disease. Parasitological tests, which are considered as gold standard to demonstrate the infection and diagnose the disease, present problems related with their sensitivity. Also, the sample´s collect is considered invasive. As consequence, serological tests could be applied as an additional tool to detect the asymptomatic and symptomatic CanL. For this purpose, distinct recombinant antigens have been studied; however, problems in their sensitivity and/or specificity have been still registered. The present review focus in advances in the identification of new diagnostic targets applied for the CanL diagnose, represented here by recombinant single, combined or chimeric proteins, as well as by peptides that mimic epitopes (mimotopes); which were selected by means of immunoproteomics and phage display.

Improving the reference standard for the diagnosis of canine visceral leishmaniasis: a challenge for current and future tests

BACKGROUND

Studies aimed at validating canine visceral leishmaniasis diagnostic tests present heterogeneous results regarding test accuracy, partly due to divergences in reference standards used and different infection evolution periods in animals.

OBJECTIVE

This study aimed to evaluate the accuracy of the rapid test-dual path platform (TR-DPP) (Biomanguinhos®), EIE-Leishmaniose-Visceral-Canina-Biomanguinhos (EIE-LVC) (Biomanguinhos®), enzyme-linked immunosorbent assay (ELISA) rK39 (in-house), and the direct agglutination test (DAT-Canis) against a reference standard comprising parasitological and molecular techniques.

METHODS

A phase II/III validation study was carried out in sample sera from 123 predominantly asymptomatic dogs living in an area endemic for visceral leishmaniasis.

FINDINGS

Sixty-nine (56.1%) animals were considered infected according to the reference standard. For each test, the sensitivity and specificity, respectively, were as follows: TR-DPP, 21.74% [confidence interval (CI)95% 13.64% to 32.82%] and 92.59% (CI95% 82.45% to 97.08%); EIE-LVC, 11.59% (CI95% 5.9% to 21.25%) and 90.74% (CI95% 80.09% to 95.98%); ELISA rK39, 37.68% (CI95% 27.18% to 49.48%) and 83.33% (CI95% 71.26% to 90.98%); and DAT-Canis, 18.84% (CI95% 11.35% to 29.61%) and 96.30% (CI95% 87.46% to 98.98%).

CONCLUSION

We concluded that improving the sensitivity of serum testing for diagnosing asymptomatic dogs must constitute a priority in the process of developing new diagnostic tests to be used in the visceral leishmaniasis control program in Brazil.

New antigens for the serological diagnosis of human visceral leishmaniasis identified by immunogenomic screening

Visceral leishmaniasis (VL) still represents a serious public health problem in Brazil due to the inefficiency of the control measures currently employed, that included early diagnosis and treatment of human cases, vector control, euthanasia of infected dogs and, recently approved in Brazil, treatment with Milteforam drug. Effective clinical management depend largely on early and unequivocal diagnosis, however, cross-reactivity have also been described in serological tests, especially when it refers to individuals from areas where Chagas' disease is also present. Thus, to discover new antigens to improve the current serological tests for VL diagnosis is urgently needed. Here, we performed an immunogenomic screen strategy to identify conserved linear B-cell epitopes in the predicted L. infantum proteome using the following criteria: i) proteins expressed in the stages found in the vertebrate host, amastigote stage, and secreted/excreted, to guarantee greater exposure to the immune system; ii) divergent from proteins present in other infectious disease pathogens with incidence in endemic areas for VL, as T. cruzi; iii) highly antigenic to humans with different genetic backgrounds, independently of the clinical stage of the disease; iv) stable and adaptable to quality-control tests to guarantee reproducibility; v) using statistical analysis to determine a suitable sample size to evaluate accuracy of diagnostic tests established by receiver operating characteristic strategy. We selected six predicted linear B-cell epitopes from three proteins of L. infantum parasite. The results demonstrated that a mixture of peptides (Mix IV: peptides 3+6) were able to identify VL cases and simultaneously able to discriminate infections caused by T. cruzi parasite with high accuracy (100.00%) and perfect agreement (Kappa index = 1.000) with direct methods performed by laboratories in Brazil. The results also demonstrated that peptide-6, Mix III (peptides 2+6) and I (peptides 2+3+6) are potential antigens able to used in VL diagnosis, represented by high accuracy (Ac = 99.52%, 99.52% and 98.56%, respectively). This study represents an interesting strategy for discovery new antigens applied to serologic diagnosis which will contribute to the improvement of the diagnosis of VL and, consequently, may help in the prevention, control and treatment of the disease in endemic areas of Brazil.

Diagnostic application of recombinant Leishmania proteins and evaluation of their in vitro immunogenicity after stimulation of immune cells collected from tegumentary leishmaniasis patients and healthy individuals

The present study evaluated the cytokine profile in PBMC supernatants and the humoral response in mucosal leishmaniasis (ML) patients and in healthy subjects living in an endemic area. Four proteins, which had previously proven to be antigenic in the human disease, were tested: LiHyM, enolase, eukaryotic initiation factor 5a, and Beta-tubulin. Results showed that all of the proteins stimulated human cells with higher IFN-γ and lower IL-4 and IL-10 levels. The analysis of antibody isotypes correlated with cell response, since the IgG2 production was higher than IgG1 in both groups. By contrast, a Th2 response was found when an antigenic Leishmania extract was used. Serological analyses revealed high sensitivity and specificity values for the serodiagnosis of the disease, when compared to the data obtained using the antigenic preparation. In conclusion, this study presents new candidates to be evaluated as biomarkers in tegumentary leishmaniasis.