Recombinant Leishmania infantum heat shock protein 83 for the serodiagnosis of cutaneous, mucosal, and visceral leishmaniases

A Review on the use of Synthetic and Recombinant Antigens for the Immunodiagnosis of Tegumentary Leishmaniasis

Improving the diagnostic technology used to detect tegumentary leishmaniasis (TL) is essential in view of it being a widespread, often neglected tropical disease, with cases reported from the Southern United States to Northern Argentina. Recombinant proteins, recombinant multiepitope proteins, and synthetic peptides have been extensively researched and used in disease diagnosis. One of the benefits of applying these antigens is a measurable increase in sensitivity and specificity, which improves test accuracy. The present review aims to describe the use of these antigens and their diagnostic effectiveness. With that in mind, a bibliographic survey was conducted on the PudMed platform using the search terms "tegumentary leishmaniasis" AND "diagno", revealing that recombinant proteins have been described and evaluated for their value in TL diagnosis since the 1990s. However, there was a spike in the number of publications using all of the antigens between 2013 and 2022, confirming an expansion in research efforts to improve diagnosis. Moreover, all of the studies involving different antigens had promising results, including improved sensitivity and specificity. These data recognize the importance of doing research with new technologies focused on developing quick, more effective diagnostic kits as early diagnosis facilitates treatment.

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.

The increased presence of repetitive motifs in the KDDR-plus recombinant protein, a kinesin-derived antigen from Leishmania infantum, improves the diagnostic performance of serological tests for human and canine visceral leishmaniasis

Visceral leishmaniasis (VL) is caused by protozoa belonging to the Leishmania donovani complex and is considered the most serious and fatal form among the different types of leishmaniasis, if not early diagnosed and treated. Among the measures of disease control stand out the management of infected dogs and the early diagnosis and appropriate treatment of human cases. Several antigens have been characterized for use in the VL diagnosis, among them are the recombinant kinesin-derived antigens from L. infantum, as rK39 and rKDDR. The main difference between these antigens is the size of the non-repetitive kinesin region and the number of repetitions of the 39 amino acid degenerate motif (6.5 and 8.5 repeats in rK39 and rKDDR, respectively). This repetitive region has a high antigenicity score. To evaluate the effect of increasing the number of repeats on diagnostic performance, we designed the rKDDR-plus antigen, containing 15.3 repeats of the 39 amino acid degenerate motif, besides the absence of the non-repetitive portion from L. infantum kinesin. Its performance was evaluated by enzyme-linked immunosorbent assay (ELISA) and rapid immunochromatographic test (ICT), and compared with the kinesin-derived antigens (rKDDR and rK39). In ELISA with human sera, all recombinant antigens had a sensitivity of 98%, whereas the specificity for rKDDR-plus, rKDDR and rK39 was 100%, 96% and 71%, respectively. When evaluated canine sera, the ELISA sensitivity was 97% for all antigens, and the specificity for rKDDR-plus, rKDDR and rK39 was 98%, 91% and 83%, respectively. Evaluation of the ICT/rKDDR-plus, using human sera, showed greater diagnostic sensitivity (90%) and specificity (100%), when compared to the IT LEISH (79% and 98%, respectively), which is based on the rK39 antigen. These results suggest that the increased presence of repetitive motifs in the rKDDR-plus protein improves the diagnostic performance of serological tests by increasing the specificity and accuracy of the diagnosis.

Potential antigenic targets used in immunological tests for diagnosis of tegumentary leishmaniasis: A systematic review

Immunological tests may represent valuable tools for the diagnosis of human tegumentary leishmaniasis (TL) due to their simple execution, less invasive nature and potential use as a point-of-care test. Indeed, several antigenic targets have been used with the aim of improving the restricted scenario for TL-diagnosis. We performed a worldwide systematic review to identify antigenic targets that have been evaluated for the main clinical forms of TL, such as cutaneous (CL) and mucosal (ML) leishmaniasis. Included were original studies evaluating the sensitivity and specificity of immunological tests for human-TL, CL and/or ML diagnosis using purified or recombinant proteins, synthetic peptides or polyclonal or monoclonal antibodies to detect Leishmania-specific antibodies or antigens. The review methodology followed PRISMA guidelines and all selected studies were evaluated in accordance with QUADAS-2. Thirty-eight original studies from four databases fulfilled the selection criteria. A total of 79 antigens were evaluated for the detection of antibodies as a diagnostic for TL, CL and/or ML by ELISA. Furthermore, three antibodies were evaluated for the detection of antigen by immunochromatographic test (ICT) and immunohistochemistry (IHC) for CL-diagnosis. Several antigenic targets showed 100% of sensitivity and specificity, suggesting potential use for TL-diagnosis in its different clinical manifestations. However, a high number of proof-of-concept studies reinforce the need for further analysis aimed at verifying true diagnostic accuracy in clinical practice.

Laboratory Diagnosis of Cutaneous and Visceral Leishmaniasis: Current and Future Methods

Leishmaniasis is a neglected tropical disease with two main clinical forms: cutaneous and visceral leishmaniasis. Diagnosis of leishmaniasis is still a challenge, concerning the detection and correct identification of the species of the parasite, mainly in endemic areas where the absence of appropriate resources is still a problem. Most accessible methods for diagnosis, particularly in these areas, do not include the identification of each one of more than 20 species responsible for the disease. Here, we summarize the main methods used for the detection and identification of leishmaniasis that can be performed by demonstration of the parasite in biological samples from the patient through microscopic examination, by in vitro culture or animal inoculation; by molecular methods through the detection of parasite DNA; or by immunological methods through the detection of parasite antigens that may be present in urine or through the detection of specific antibodies against the parasite. Potential new methods that can be applied for laboratory diagnosis of leishmaniasis are also discussed.

A new Leishmania hypothetical protein can be used for accurate serodiagnosis of canine and human visceral leishmaniasis and as a potential prognostic marker for human disease

Distinct antigens have been evaluated with diagnostic purpose for canine and human visceral leishmaniasis (VL), and variable sensitivity and specificity values have been obtained in the assays. In the present study, a Leishmania infantum hypothetical protein called LiHyG, which was identified in an immunoproteomics study in Leishmania infantum amastigote extracts by antibodies in VL dogs sera; was cloned, expressed, purified and evaluated as a recombinant protein (rLiHyG) for the diagnosis of canine and human disease. The recombinant amastigote-specific A2 protein (rA2) and a soluble L. infantum protein extract (SLA) were used as controls. For canine VL, the sensitivity values were of 100%, 57.29% and 48.57%, when rLiHyG, rA2 and SLA were used, respectively, while the specificity values were of 100%, 81.43% and 88.57%, respectively. In addition, AUC values were of 1.00, 0.72 and 0.65, when rLiHyG, rA2 and SLA were used, respectively, while accuracy was of 100%, 72.38% and 75.24%, respectively. For human VL, the sensitivity values were of 100%, 84.00% and 88.00%, when rLiHyG, rA2 and SLA were used, respectively, while the specificity values were of 100%, 58.75% and 73.75%, respectively. In addition, AUC values were of 1.00, 0.76 and 0.83, when rLiHyG, rA2 and SLA were used, respectively, while accuracy was of 100%, 64.8% and 66.6%, respectively. The prognostic role of rLiHyG in the human VL was also evaluated, by means of post-therapeutic serological follow-up with sera samples collected before and six months after treatment. Results showed that treated patients presented significant reductions in the anti-rLiHyG IgG, IgG1, and IgG2 antibody levels, with results being similar to those found in healthy subjects. Testing the rA2 protein and SLA as antigens, lower IgG, IgG1, and IgG2 levels were also found, although they were higher after treatment than those obtained for rLiHyG. In conclusion, results suggested that rLiHyG could be considered for future studies as a diagnostic and/or prognostic marker for canine and human VL.

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.

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.

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.

Immunodiagnosis of human and canine visceral leishmaniasis using recombinant Leishmania infantum Prohibitin protein and a synthetic peptide containing its conformational B-cell epitope

In the present study, Leishmania infantum's Prohibitin was cloned and, alongside a synthetic peptide, evaluated for the serodiagnosis of visceral and tegumentary leishmaniasis (CVL and TL, respectively) in dogs and humans. For TL diagnosis, this study analyzed serum samples from cutaneous (n = 20) or mucosal (n = 39) leishmaniasis patients, and from Chagas disease (CD) patients (n = 8) and non-infected patients (n = 45). For CVL diagnosis, serum samples from asymptomatic (n = 14), symptomatic (n = 71), non-infected (n = 116), and Leish-Tec®-vaccinated (n = 79) dogs were examined, as well as T. cruzi (n = 11) and Ehrlichia canis (n = 10) infected animals. An indirect ELISA method using rProhibitin showed diagnostic sensitivity and specificity values of 91.76% and 89.91%, respectively. L. infantum SLA showed 86.11% and 48.24% of specificity and sensitivity, respectively, for CVL serodiagnosis, and 98.31% and 84.91% sensitivity and specificity, respectively for TL diagnosis. L. braziliensis SLA showed 75.47% and 83.05% of specificity and sensitivity, respectively, for TL diagnosis. The synthetic peptide showed a better result in TL than in CVL diagnosis. In conclusion, preliminary results suggest that the detection of antibodies against the rProhibitin protein and the synthetic peptide improves the serodiagnosis of TL and CVL.

Serological Evaluation of Cutaneous Leishmania tropica Infection in Northern Israel

Leishmania spp. are medically important unicellular parasites transmitted by phlebotomine sand flies. The World Health Organization recently highlighted the importance of reliable diagnostic tools for leishmaniasis. Our study of human infection was conducted in two endemic foci of Leishmania tropica in the Galilee region, northern Israel. Elevated anti-Leishmania antibodies were present in the majority (78.6%) of L. tropica-PCR positive individuals. Moreover, the enzyme-linked immunosorbent assay showed high sensitivity, specificity, and negative and positive predictive values (ranging between 73% and 79%), thus fulfilling the basic requirement for future development of a serodiagnostic and screening tool. The anti-sand fly saliva antibodies used as biomarkers of exposure reflected the composition of the local sand fly fauna as well as the abundance of individual species. High levels of antibodies against vector salivary proteins may further indicate frequent exposure to sand flies and consequently a higher probability of Leishmania transmission.

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.

Potential application of rLc36 protein for diagnosis of canine visceral leishmaniasis

Visceral leishmaniasis (VL) is fatal if left untreated. Infected dogs are important reservoirs of the disease, and thus specific identification of infected animals is very important. Several diagnostic tests have been developed for canine VL (CVL); however, these tests show varied specificity and sensitivity. The present study describes the recombinant protein rLc36, expressed by Leishmania infantum, as potential antigen for more sensitive and specific diagnosis of CVL based on an immunoenzymatic assay. The concentration of 1.0 μg/mL of rLc36 enabled differentiation of positive and negative sera and showed a sensitivity of 85% and specificity of 71% (with 95% confidence), with an accuracy of 76%.

Canine visceral leishmaniasis follow-up: a new anti-IgG serological test more sensitive than ITS-1 conventional PCR

Visceral leishmaniasis (VL) is a neglected tropical disease with dogs serving as reservoirs for one of its etiological agents, Leishmania infantum. In Brazil, VL control involves culling of seropositive dogs, among other actions. However, the most employed serological tests lack accuracy, and are not able to detect canine visceral leishmaniasis (CVL) during the early stages of infection. Early detection of CVL is highly desirable in order to shorten the contact time between the infected reservoirs and the vectors. In this study, we investigated the ability of two multiepitope proteins, PQ10 and PQ20, to detect CVL at earlier stages than currently employed methods, including ITS-1 conventional PCR. Using serum samples from naturally infected dogs, we observed that ELISA-PQ10 and ELISA-PQ20 were able to detect Leishmania infection at earlier time points as compared with kDNA PCR-RFLP in anti-IgG and anti-IgM assays. Using sera from experimentally infected dogs, we monitored seroconversion using multiepitope proteins, ELISA-crude antigen, as well as ITS-1 conventional and real-time PCR. While seroconversion was detected by ELISA-crude antigen in 16.6% of the dogs, multiepitope proteins were able to detect seroconversion in more than 80% of them. Moreover, the ability of ELISA-PQ10 and ELISA-PQ20 to detect Leishmania infection at earlier time points as compared with conventional PCR was also confirmed in experimental infection dogs' sera. Immunofluorescence to Babesia canis and Ehrlichia canis did not show cross-reactions with ELISA-PQ10/PQ20 positive samples. Results of real-time PCR and ELISA with multiepitope proteins were very similar, with concordances between 80 and 100%. Furthermore, our findings indicated that PQ10 and PQ20 immunoassays can be related to parasite load. ELISA-PQ10 and ELISA-PQ20 are more sensitive diagnostic tools for early CVL detection as compared with other methods They could potentially be used in screening tests due to easy execution and low costs facilities.

An ELISA immunoassay employing a conserved Leishmania hypothetical protein for the serodiagnosis of visceral and tegumentary leishmaniasis in dogs and humans

In the present study, a conserved Leishmania hypothetical protein, namely LiHypA, was evaluated for the serodiagnosis of visceral and tegumentary leishmaniasis in dogs and humans. This protein showed a high amino acid sequence homology between viscerotropic and cutaneotropic Leishmania species. An enzyme-linked immunosorbent assay (ELISA) was developed using the recombinant antigen (rLiHypA), in addition to the A2 protein and two parasite antigenic preparations, which were used as controls. Regarding human diagnosis, results showed that rLiHypA was more sensitive and specific than ELISA-L. braziliensis SLA in detecting both cutaneous or mucosal leishmaniasis patients, but not those from Chagas disease patients or healthy subjects. Regarding canine diagnosis, this recombinant antigen showed higher sensitivity and specificity values, as well as a perfect accuracy to identify asymptomatic and symptomatic visceral leishmaniasis (VL) in dogs, but not those from vaccinated animals or those developing babesiosis, ehrlichiosis, or Chagas disease. However, using the rA2 protein or L. braziliensis SLA as controls, significant cross-reactivity was found when these samples were used, hampering their sensitivity and specificity values for the diagnosis. In this context, LiHypA could be considered a candidate to be evaluated for the serodiagnosis of visceral and tegumentary leishmaniasis in dogs and humans.

Evaluation of a hypothetical protein for serodiagnosis and as a potential marker for post-treatment serological evaluation of tegumentary leishmaniasis patients

The serodiagnosis for tegumentary leishmaniasis (TL) presents problems related to the sensitivity and/or specificity of the tests. In the present study, an enzyme-linked immunosorbent assay (ELISA) technique was used to evaluate the performance from a Leishmania braziliensis hypothetical protein, LbHyM, in an attempt to compare its serological reactivity with a soluble Leishmania antigenic preparation (SLA) for the serodiagnosis of cutaneous (CL) and mucosal (ML) leishmaniasis. LbHyM was predicted to be a kinesin-like protein by bioinformatics tools. Serum samples were collected from both CL and ML patients, as well as from those with Chagas disease and from healthy subjects living in endemic or non-endemic areas of TL. Also, sera were collected from patients before and after the treatments, seeking to evaluate their serological follow-up in relation to the anti-protein and anti-parasite antibody levels. When an ELISA-rLbHyM assay was performed, it proved to be significantly more sensitive than ELISA-L. braziliensis SLA in detecting both CL and ML patients. Also, when using sera from Chagas disease patients, the ELISA-rLbHyM proved to be more specific than ELISA-SLA. The anti-protein and anti-parasite antibody levels were also evaluated 6 months after the treatments, and treated patients showed significantly lower levels of specific-rLbHyM antibodies, when compared to the anti-parasite antibody levels. In conclusion, the ELISA-rLbHyM assay can be considered a confirmatory serological technique for the serodiagnosis of L. braziliensis infection and can also be used in the serological follow-up of treated patients, aiming to correlate the low anti-protein antibody levels with the improvement of the healthy state of the patients.

Use of Recombinant Antigens for Sensitive Serodiagnosis of American Tegumentary Leishmaniasis Caused by Different Leishmania Species

American tegumentary leishmaniasis (ATL) (also known as cutaneous leishmaniasis [CL]) is caused by various species of protozoa of the genus Leishmania. The diagnosis is achieved on a clinical, epidemiological, and pathological basis, supported by positive parasitological exams and demonstration of leishmanin delayed-type hypersensitivity. Serological assays are not routinely used in the diagnosis because many are considered to have low sensitivity and the particular Leishmania species causing the disease can lead to variable performance. In the present study, we generated recombinant versions of two highly conserved Leishmania proteins, Leishmania (Viannia) braziliensis-derived Lb8E and Lb6H, and evaluated both in enzyme-linked immunosorbent assays (ELISA). Recombinant Lb6H (rLb6H) had better performance and reacted with 100.0% of the ATL and 89.4% of the VL samples. These reactions with rLb6H were highly specific (98.5%) when compared against those for samples from healthy control individuals. We then assessed rLb6H against sera from ATL patients infected with different species of Leishmania prevalent in Brazil [Leishmania (Leishmania) amazonensis, L. (Viannia) braziliensis, and L. (V.) guyanensis] and samples from patients with other infectious diseases. In analyses of 500 sera, ELISA using rLb6H detected all 219 ATL samples (sensitivity of 100.0%) with an overall specificity of 93.9% (considering healthy individuals and other infectious diseases patients). Only a minority of samples from Chagas disease patients possessed antibodies against rLb6H, and all of these responses were low (with a highest reactivity index of 2.2). Taken together, our data support further evaluation of rLb6H and the potential for its routine use in the serological diagnosis of ATL.

Leishmania infantum mimotopes and a phage-ELISA assay as tools for a sensitive and specific serodiagnosis of human visceral leishmaniasis

Serological methods used to diagnose visceral leishmaniasis (VL) are considered minimally invasive, but they present problems related with their sensitivity and/or specificity. In this study, a subtractive selection using the phage display technology against antibodies from healthy subjects living in endemic and non-endemic areas of disease, as well as from Chagas disease patients and those developing active VL, was developed. The aim of this study was to select bacteriophage-fused epitopes to be used in the serodiagnosis of human VL. Eight phage clones were selected after the bio-panning rounds, and their reactivity was evaluated in a phage-ELISA assay against a human serological panel. A wild-type clone and the recombinant K39-based immunochromatographic test were used as controls. In the results, it was shown that all clones showed an excellent performance to serologically identify VL patients, demonstrating the feasibility of the isolated phages for developing a specific and sensitive serodiagnosis of human VL.

Application of Recombinant Proteins for Serodiagnosis of Visceral Leishmaniasis in Humans and Dogs

Visceral leishmaniasis (VL) is a zoonotic disease caused by leishmania species. Dogs are considered to be the main reservoir of VL. A number of methods and antigen-based assays are used for the diagnosis of leishmaniasis. However, currently available methods are mainly based on direct examination of tissues for the presence of parasites, which is highly invasive. A variety of serological tests are commonly applied for VL diagnosis, including indirect fluorescence antibody test, enzyme-linked immunosorbent assay (ELISA), dot-ELISA, direct agglutination test, Western-blotting, and immunochromatographic test. However, when soluble antigens are used, serological tests are less specific due to cross-reactivity with other parasitic diseases. Several studies have attempted to replace soluble antigens with recombinant proteins to improve the sensitivity and the specificity of the immunodiagnostic tests. Major technological advances in recombinant antigens as reagents for the serological diagnosis of VL have led to high sensitivity and specificity of these serological tests. A great number of recombinant proteins have been shown to be effective for the diagnosis of leishmania infection in dogs, the major reservoir of L. infantum. Although few recombinant proteins with high efficacy provide reasonable results for the diagnosis of human and canine VL, more optimization is still needed for the appropriate antigens to provide high-throughput performance. This review aims to explore the application of different recombinant proteins for the serodiagnosis of VL in humans and dogs.

Proteins Selected in Leishmania (Viannia) braziliensis by an Immunoproteomic Approach with Potential Serodiagnosis Applications for Tegumentary Leishmaniasis

The serodiagnosis of human tegumentary leishmaniasis (TL) presents some problems, such as the low level of antileishmanial antibodies found in most of the patients, as well as the cross-reactivity in subjects infected by other trypanosomatids. In the present study, an immunoproteomic approach was performed aimed at identification of antigens in total extracts of stationary-phase promastigote and amastigote-like forms of Leishmania (Viannia) braziliensis using sera from TL patients. With the purpose of reducing the cross-reactivity of the identified proteins, spots recognized by sera from TL patients, as well as those recognized by antibodies present in sera from noninfected patients living in areas where TL is endemic and sera from Chagas disease patients, were discarded. Two Leishmania hypothetical proteins and 18 proteins with known functions were identified as antigenic. The study was extended with some of them to validate the results of the immunoscreening. The coding regions of five of the characterized antigens (enolase, tryparedoxin peroxidase, eukaryotic initiation factor 5a, β-tubulin, and one of the hypothetical proteins) were cloned in a prokaryotic expression vector, and the corresponding recombinant proteins were purified and evaluated for the serodiagnosis of TL. The antigens presented sensitivity and specificity values ranging from 95.4 to 100% and 82.5 to 100%, respectively. As a comparative antigen, a preparation of Leishmania extract showed sensitivity and specificity values of 65.1 and 57.5%, respectively. The present study has enabled the identification of proteins able to be employed for the serodiagnosis of TL.

Coadministration of the Three Antigenic Leishmania infantum Poly (A) Binding Proteins as a DNA Vaccine Induces Protection against Leishmania major Infection in BALB/c Mice

BACKGROUND

Highly conserved intracellular proteins from Leishmania have been described as antigens in natural and experimental infected mammals. The present study aimed to evaluate the antigenicity and prophylactic properties of the Leishmania infantum Poly (A) binding proteins (LiPABPs).

METHODOLOGY/PRINCIPAL FINDINGS

Three different members of the LiPABP family have been described. Recombinant tools based on these proteins were constructed: recombinant proteins and DNA vaccines. The three recombinant proteins were employed for coating ELISA plates. Sera from human and canine patients of visceral leishmaniasis and human patients of mucosal leishmaniasis recognized the three LiPABPs. In addition, the protective efficacy of a DNA vaccine based on the combination of the three Leishmania PABPs has been tested in a model of progressive murine leishmaniasis: BALB/c mice infected with Leishmania major. The induction of a Th1-like response against the LiPABP family by genetic vaccination was able to down-regulate the IL-10 predominant responses elicited by parasite LiPABPs after infection in this murine model. This modulation resulted in a partial protection against L. major infection. LiPABP vaccinated mice showed a reduction on the pathology that was accompanied by a decrease in parasite burdens, in antibody titers against Leishmania antigens and in the IL-4 and IL-10 parasite-specific mediated responses in comparison to control mice groups immunized with saline or with the non-recombinant plasmid.

CONCLUSION/SIGNIFICANCE

The results presented here demonstrate for the first time the prophylactic properties of a new family of Leishmania antigenic intracellular proteins, the LiPABPs. The redirection of the immune response elicited against the LiPABP family (from IL-10 towards IFN-γ mediated responses) by genetic vaccination was able to induce a partial protection against the development of the disease in a highly susceptible murine model of leishmaniasis.