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Leishmania infantum is the most common cause of visceral leishmaniasis (VL) in Iran, where mainly the patients are children under the age of 5 years. Timely, less invasive, and accurate diagnosis and proper treatment of the disease are necessary. This retrospective study aimed to search for a less invasive but robust algorithm on VL diagnostic tests in children. Four hundred and fifteen patients with clinical suspicion of VL, 50 healthy children from VL endemic areas, 46 healthy individuals from non-endemic VL areas, and 47 non-VL diseases were tested using three diagnostic tests: indirect immunofluorescent antibody test (IFAT), rK39-rapid diagnostic test (rK39-RDT), and quantitative PCR (qPCR). One hundred and two suspected VL cases were positive in at least one test and were cured after receiving appropriate treatment. Of these 102 VL patients, 94 were positive in qPCR, 84 in IFAT, and 79 in rK39-RDT. None of the tests detected all the patients, but overall, qPCR is capable of detecting more VL patients than serological tests, i.e., 92.2%, compared to IFAT, 82.4%, and rK39, 77.5%. There was only a significant difference between the sensitivity of qPCR and rK39-RDT (p = 0.024). The specificity was 100% for qPCR and IFAT (≥128) and 98.6% for rK39-RDT. qPCR alone is capable of detecting most of the VL-suspected children. Serological tests like IFAT and rk39-RDT are recommended to increase the overall sensitivity of detection in patients with a negative molecular test. Combining qPCR with a serological test (IFAT or rK39-RDT) can help diagnose 98% of VL. In laboratories without molecular facilities, we recommend testing with the combination of rK39-RDT and IFAT yielding a combined sensitivity of 93.1% equivalent to that of qPCR in our study.

The direct agglutination test (DAT) for visceral leishmaniasis (VL) is the serodiagnostic test for VL that has the most robust sensitivity and specificity in the field across all endemic regions. It is based on trypsin-treated and formaldehyde-fixed whole promastigote cells from Leishmania donovani. The exact identity and nature of the epitopes on the DAT antigen that cause agglutination with VL patients’ sera are currently unknown. In this study, we performed antigen-inhibition studies which revealed that lipophosphoglycan (LPG) and the DAT antigen share epitopes. Antibody inhibition with a monoclonal antibody directed against the phosphoglycan repeat epitope of LPG showed that this is not the epitope that reacts with human sera. Oxidation of carbohydrates by sodium metaperiodate did not alter the reactivity of human sera with the DAT antigen and LPG. This indicates that carbohydrates do not play a role in the reaction of the DAT antigen with antibodies in serum from VL patients, and that they also are not involved in the reaction of LPG with the same serum. We conclude that the noncarbohydrate moiety of LPG, that is, the core–anchor fragment, and potentially other noncarbohydrate epitopes on the surface of the DAT antigen are responsible for its agglutination with antibodies from VL patients. As LPG plays a role in the DAT reaction, this could facilitate the following: 1) incorporation of LPG, preferably the synthetic version of the core–anchor fragment, into an immunochromatographic test format that is more adapted as a point-of-care test (short incubation, little training, and equipment needed) than DAT and 2) enhancing the quality control for the production of the DAT antigen.

Background Kinesin-related gene diversity among strains and species of Leishmania may impact the sensitivity and specificity of serodiagnostic tests for visceral leishmaniasis (VL). Methods In this study, we report on the recombinant expression of this novel Iranian Leishmania infantum (MCAN14/47) homologue of rK39 (Li-rK39), in L. tarentolae. The diagnostic potential of the Li-rK39 antigen was evaluated in an ELISA, using sera from 100 VL patients, 190 healthy endemic controls, 46 non-endemic healthy controls and 47 patients with other infections. Results The results showed a sensitivity of 96% and a specificity of 93.8%. A commercial rK39 immunochromatographic test (ICT) was 90% sensitive and 100% specific on the same cohort. Conclusions Here, we show that the K39 gene from an Iranian L. infantum isolate is heterozygous as compared to the sequence of the Brazilian L. infantum (former L. chagasi), whose antigen is incorporated in most rK39-based immunochromatographic tests. Therefore, Li-rK39 has the potential to be used as an alternative for VL diagnosis in Iran.

Current diagnostic tests for visceral leishmaniasis (VL) are either not adapted for use in resource-poor settings or are insufficiently accurate in Eastern Africa. Only the direct agglutination test (DAT), based on whole Leishmania promastigotes, is highly reliable in all endemic regions, but its implementation is hampered by the need for a cold chain, minimal laboratory conditions, and long incubation times. Integrating the DAT antigen(s) in an immunochromatographic rapid diagnostic test (RDT) would overcome these disadvantages. Unfortunately, the identity of the DAT antigen(s) involved in the agglutination reaction is unknown. For this study, we reviewed all publications that might shed some light on this issue. We conclude that the DAT antigen is a mixture of Leishmania-specific epitopes of protein, carbohydrate, and lipid nature. To develop an accurate RDT for VL diagnosis in Eastern Africa, we suggest to complement the classical protein antigen discovery with approaches to identify carbohydrate and lipid epitopes.

Background Hookworms cause substantial morbidity in children and women of reproductive age. The control strategy of mass drug administration is suboptimal, hence the need for a vaccine. Necator americanus aspartic protease-1 (Na-APR-1) and N americanus glutathione S-transferase-1 (Na-GST-1) are involved in the digestion and detoxification of haemoglobin in the hookworm digestive tract. In animal models, vaccination against these antigens resulted in protection from challenge infection. Both vaccine candidates were shown to be safe and well tolerated when administered separately to healthy adults. We assessed the safety and immunogenicity of co-administered Na-GST-1 and Na-APR-1 (M74) vaccines in healthy Gabonese adults.Methods This randomised, controlled, double-blind, phase 1, dose-escalation trial was done at the Centre de Recherches Medicales de Lambarene, in a region of Gabon where N americanus and other helminths are prevalent. Healthy adults aged 18-50 years and living in Lambarene or the surrounding areas were recruited to the study. Participants were enrolled consecutively into two dose cohorts (30 mu g or 100 mu g of the experimental vaccines) and randomly assigned in blocks (block size four) to receive three doses of either co-administered Na-GST-1 plus Na-APR-1 (M74; 30 mu g or 100 mu g of each), adjuvanted with Alhydrogel (aluminium hydroxide gel suspension) together with an aqueous formulation of glucopyranosyl lipid A, or hepatitis B vaccine plus saline (control group). Vaccines were administered intramuscularly on days 0, 28, and 180. The primary endpoint was safety, with immunogenicity a secondary endpoint. The intention-to-treat population was used for safety analyses, whereas for immunogenicity analyses, the per-protocol population was used (participants who received all scheduled vaccinations). Control vaccine recipients for both dose cohorts were combined for the analyses. The trial is registered with ClinicalTrials.gov, NCT02126462.Findings Between Oct 27, 2014, and Jan 31, 2015, 56 individuals were screened for eligibility, of whom 32 were enrolled and randomly assigned to one of the three study groups (12 each in the 30 mu g and 100 mu g experimental vaccine groups and eight in the control group). Both study vaccines were well tolerated in both dose groups. The most common adverse events were mild-to-moderate injection-site pain, headache, myalgia, and nausea. No severe or serious adverse events related to the vaccines were recorded. 52 unsolicited vaccine-related adverse events occurred during the study, but there was no difference in frequency between vaccine groups. IgG antibodies were induced to each of the vaccine antigens, with mean IgG levels increasing after each vaccination. Vaccination with 100 mu g of each vaccine antigen consistently induced IgG seroconversion (IgG levels above the reactivity threshold). Peak IgG responses were observed 2 weeks after the third vaccine dose for both antigens, with all participants who received the 100 mu g doses seroconverting at that timepoint. IgG levels steadily declined until the final study visit 6 months after the third vaccination, although they remained significantly higher than baseline in the 100 mu g dose group.Interpretation Vaccination with recombinant Na-GST-1 and Na-APR-1 (M74) in healthy adults living in N americanusendemic areas of Gabon was safe and induced IgG to each antigen. To our knowledge, this study is the first to report results of Na-APR-1 (M74) co-administered with Alhydrogel in participants from an N americanus-endemic area. Further clinical development of these vaccines should involve efficacy studies. Funding European Union Seventh Framework Programme. Copyright (C) 2020 Elsevier Ltd. All rights reserved.

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., Author summary 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.

Surface molecules are of major importance for host-parasite interactions. During Entamoeba histolytica infections, these interactions are predicted to be of prime importance for tissue invasion, induction of colitis and liver abscess formation. To date, however, little is known about the molecules involved in these processes, with only about 20 proteins or protein families found exposed on the E. histolytica surface. We have therefore analyzed the complete surface proteome of E. histolytica. Using cell surface biotinylation and mass spectrometry, 693 putative surface-associated proteins were identified. In silico analysis predicted that ∼26% of these proteins are membrane-associated, as they contain transmembrane domains and/or signal sequences, as well as sites of palmitoylation, myristoylation, or prenylation. An additional 25% of the identified proteins likely represent nonclassical secreted proteins. Surprisingly, no membrane-association sites could be predicted for the remaining 49% of the identified proteins. To verify surface localization, 23 proteins were randomly selected and analyzed by immunofluorescence microscopy. Of these 23 proteins, 20 (87%) showed definite surface localization. These findings indicate that a far greater number of E. histolytica proteins than previously supposed are surface-associated, a phenomenon that may be based on the high membrane turnover of E. histolytica.

Background The selection pressure imposed by the parasite has a functional consequence on the immune genes, leading to altered immune function in which regulatory T cells (Tregs) induced by parasites during infectious challenges modulate or thwart T effector cell mechanism. Methods We identified and investigated regulatory polymorphisms in the immune gene IL2 and its receptor IL2R alpha (also known as CD25) in Gabonese individuals exposed to plentiful parasitic infections. Results We identified two reported variants each for IL2 and its receptor IL2R alpha gene loci. Also identified were two novel variants, -83 /-84 CT deletions (ss410961576) for IL2 and -409C/T (ss410961577) for IL2R alpha. We further validated all identified promoter variants for their allelic gene expression using transient transfection assays. Three promoter variants of the IL2 locus revealed no significant expression of the reporter gene. The identified novel variant (ss410961577C/T) of the IL2R alpha revealed a significant higher expression of the reporter gene in comparison to the major allele (Prs12722616C/T variant of the IL2R alpha locus altered the transcription factor binding site TBP (TATA box binding protein) and C/EBP beta (CCAAT/enhancer binding protein beta) that are believed to regulate the Treg function. Conclusions The identification and validation of such regulatory polymorphisms in the immune genes may provide a basis for future studies on parasite susceptibility in a population where T cell functions are compromised.