Serial quantitative PCR assay for detection, species discrimination, and quantification of Leishmania spp. in human samples

Detection and Differentiation of Leishmania spp. in Clinical Specimens by Use of a SYBR Green-Based Real-Time PCR Assay

Leishmaniasis in humans is caused by Leishmania spp. in the subgenera Leishmania and Viannia Species identification often has clinical relevance. Until recently, our laboratory relied on conventional PCR amplification of the internal transcribed spacer 2 (ITS2) region (ITS2-PCR) followed by sequencing analysis of the PCR product to differentiate Leishmania spp. Here we describe a novel real-time quantitative PCR (qPCR) approach based on the SYBR green technology (LSG-qPCR), which uses genus-specific primers that target the ITS1 region and amplify DNA from at least 10 Leishmania spp., followed by analysis of the melting temperature (Tm) of the amplicons on qPCR platforms (the Mx3000P qPCR system [Stratagene-Agilent] and the 7500 real-time PCR system [ABI Life Technologies]). We initially evaluated the assay by testing reference Leishmania isolates and comparing the results with those from the conventional ITS2-PCR approach. Then we compared the results from the real-time and conventional molecular approaches for clinical specimens from 1,051 patients submitted to the reference laboratory of the Centers for Disease Control and Prevention for Leishmania diagnostic testing. Specimens from 477 patients tested positive for Leishmania spp. with the LSG-qPCR assay, specimens from 465 of these 477 patients also tested positive with the conventional ITS2-PCR approach, and specimens from 10 of these 465 patients had positive results because of retesting prompted by LSG-qPCR positivity. On the basis of the Tm values of the LSG-qPCR amplicons from reference and clinical specimens, we were able to differentiate four groups of Leishmania parasites: the Viannia subgenus in aggregate; the Leishmania (Leishmania) donovani complex in aggregate; the species L (L) tropica; and the species L (L) mexicana, L (L) amazonensis, L (L) major, and L (L) aethiopica in aggregate.

Field Validation of SYBR Green- and TaqMan-Based Real-Time PCR Using Biopsy and Swab Samples To Diagnose American Tegumentary Leishmaniasis in an Area Where Leishmania (Viannia) braziliensis Is Endemic

The precise diagnosis of American tegumentary leishmaniasis (ATL) is an essential task due to the disease's associated morbidity. A noninvasive, extremely sensitive, and highly specific exam is critical, particularly for mucosal leishmaniasis (ML), in which a low parasite quantity is expected. We aimed to compare the diagnostic accuracy of swab and biopsy sample analysis using SYBR Green- and TaqMan-based real-time PCR (qPCR) assays with that of a composite reference standard consisting of the Montenegro skin test, serology, histopathology, smears, culture, and conventional PCR. In total, 55 patients with ATL (ML, 18 patients; cutaneous leishmaniasis [CL], 37 patients) and 36 patients without ATL were studied. qPCR analysis of swabs was more accurate when using SYBR Green (87.88%; 95% confidence interval [CI], 77.86 to 93.73 patients) than when using TaqMan (78.79%; 95% CI, 67.49 to 86.92%) (P = 0.031). SYBR Green (84.72%; 95% CI, 74.68 to 91.25%) was also more accurate than TaqMan (73.61%; 95% CI, 62.42 to 82.41%) for biopsy samples (P = 0.008). All qPCR methods were 100% specific. Swabs and biopsy specimens had similar sensitivity when using the same chemistry (P = 0.125 for SYBR Green and P = 0.625 for TaqMan). Moreover, qPCR achieved better performance than most existing techniques used for the diagnosis of ATL and also detected the Leishmania parasite in a greater proportion of patients than the associated histopathology, smear, culture, and conventional PCR techniques did. Swabs therefore represent a useful diagnostic tool because they not only are noninvasive but also can achieve an accuracy similar to that of biopsy samples. The high accuracy of SYBR Green-based qPCR may also reduce the requirement for associated parasitological tests for ATL diagnosis.

First case of canine leishmaniasis on the island of St. Kitts, West Indies

Leishmaniasis caused by Leishmania infantum is an emerging/re-emerging zoonosis with dogs as the main reservoir. The first autochthonous case of canine leishmaniasis in St. Kitts was diagnosed, and had cutaneous involvement. This discovery expands the distribution of leishmaniasis to include this insular country in the West Indies and dictates further characterization of the disease in this region.

Atypical Manifestations of Cutaneous Leishmaniasis in a Region Endemic for Leishmania braziliensis: Clinical, Immunological and Parasitological Aspects

BACKGROUND

Atypical cutaneous leishmaniasis (ACL) has become progressively more frequent in Corte de Pedra, Northeast Brazil. Herein we characterize clinical presentation, antimony response, cytokine production and parasite strains prevailing in ACL.

METHODOLOGY/PRINCIPAL FINDINGS

Between 2005 and 2012, 51 ACL (cases) and 51 temporally matched cutaneous leishmaniasis (CL) subjects (controls) were enrolled and followed over time in Corte de Pedra. Clinical and therapeutic data were recorded for all subjects. Cytokine secretion by patients' peripheral blood mononuclear cells (PBMC) stimulated with soluble parasite antigen in vitro, and genotypes in a 600 base-pair locus in chromosome 28 (CHR28/425451) of the infecting L. (V.) braziliensis were compared between the two groups. ACL presented significantly more lesions in head and neck, and higher rate of antimony failure than CL. Cytosine-Adenine substitutions at CHR28/425451 positions 254 and 321 were highly associated with ACL (p<0.0001). In vitro stimulated ACL PBMCs produced lower levels of IFN-γ (p = 0.0002) and TNF (p <0.0001), and higher levels of IL-10 (p = 0.0006) and IL-17 (p = 0.0008) than CL PBMCs.

CONCLUSIONS/SIGNIFICANCE

ACL found in Northeast Brazil is caused by distinct genotypes of L. (V.) braziliensis and presents a cytokine profile that departs from that in classical CL patients. We think that differences in antigenic contents among parasites may be in part responsible for the variation in cytokine responses and possibly immunopathology between CL and ACL.

The microbiological signature of human cutaneous leishmaniasis lesions exhibits restricted bacterial diversity compared to healthy skin

Localised cutaneous leishmaniasis (LCL) is the most common form of cutaneous leishmaniasis characterised by single or multiple painless chronic ulcers, which commonly presents with secondary bacterial infection. Previous culture-based studies have found staphylococci, streptococci, and opportunistic pathogenic bacteria in LCL lesions, but there have been no comparisons to normal skin. In addition, this approach has strong bias for determining bacterial composition. The present study tested the hypothesis that bacterial communities in LCL lesions differ from those found on healthy skin (HS). Using a high throughput amplicon sequencing approach, which allows for better populational evaluation due to greater depth coverage and the Quantitative Insights Into Microbial Ecology pipeline, we compared the microbiological signature of LCL lesions with that of contralateral HS from the same individuals.Streptococcus, Staphylococcus,Fusobacterium and other strict or facultative anaerobic bacteria composed the LCL microbiome. Aerobic and facultative anaerobic bacteria found in HS, including environmental bacteria, were significantly decreased in LCL lesions (p < 0.01). This paper presents the first comprehensive microbiome identification from LCL lesions with next generation sequence methodology and shows a marked reduction of bacterial diversity in the lesions.

Fluconazole in the Treatment of Cutaneous Leishmaniasis Caused by Leishmania braziliensis: A Randomized Controlled Trial

BACKGROUND

 The treatment of cutaneous leishmaniasis (CL) caused by Leishmania braziliensis in Brazil with pentavalent antimony (Sb^v) is associated with a high rate of failure, up to 45% of cases. In addition, Sb^v can only administered parenterally and has important toxic effect. An effective, safe, and oral treatment for CL is required.

METHODS

 A randomized controlled clinical trial was conducted to compare the efficacy and safety of high-dosage oral fluconazole (6.5-8.0 mg/kg/d for 28 days) versus a standard Sb^v protocol (20 mg/kg/d for 20 days) for the treatment of CL in Bahia, Brazil.

RESULTS

 A total of 53 subjects were included in the trial; 26 were treated with Sb^v, and 27 with fluconazole. Intention-to-treat analysis showed initial cure rates (2 months after treatment) of 22.2% (6 of 27) in the fluconazole and 53.8% (14 of 26) in the Sb^v group (P = .04). Six months after treatment, the final cure rate remained the same in both groups, without any relapses. The frequencies of adverse effects in the Sb^v and fluconazole groups were similar, 34.6% versus 37% respectively. One patient treated with fluconazole discontinued treatment owing to malaise, headache, and moderate dizziness (Common Terminology Criteria for Adverse Events grade 2).

CONCLUSIONS

 Oral fluconazole at a dosage of 6.5-8 mg/kg/d for 28 days should not be considered an effective treatment for CL caused by L. braziliensisClinical Trials Registration. NCT01953744.

Progress in the Mathematical Modelling of Visceral Leishmaniasis

The leishmaniases comprise a complex of diseases characterized by clinical outcomes that range from self-limiting to chronic, and disfiguring and stigmatizing to life threatening. Diagnostic methods, treatments, and vector and reservoir control options exist, but deciding the most effective interventions requires a quantitative understanding of the population level infection and disease dynamics. The effectiveness of any set of interventions has to be determined within the context of operational conditions, including economic and political commitment. Mathematical models are the best available tools for studying quantitative systems crossing disciplinary spheres (biology, medicine, economics) within environmental and societal constraints. In 2005, the World Health Assembly and government health ministers of India, Nepal, and Bangladesh signed a Memorandum of Understanding to eliminate the life threatening form of leishmaniasis, visceral leishmaniasis (VL), on the Indian subcontinent by 2015 through a combination of early case detection, improved treatments, and vector control. The elimination target is <1 case/10,000 population at the district or subdistrict level compared to the current 20/10,000 in the regions of highest transmission. Towards this goal, this chapter focuses on mathematical models of VL, and the biology driving those models, to enable realistic predictions of the best combination of interventions. Several key issues will be discussed which have affected previous modelling of VL and the direction future modelling may take. Current understanding of the natural history of disease, immunity (and loss of immunity), and stages of infection and their durations are considered particularly for humans, and also for dogs. Asymptomatic and clinical infection are discussed in the context of their relative roles in Leishmania transmission, as well as key components of the parasite-sandfly-vector interaction and intervention strategies including diagnosis, treatment and vector control. Gaps in current biological knowledge and potential avenues to improve model structures and mathematical predictions are identified. Underpinning the marriage between biology and mathematical modelling, the content of this chapter represents the first step towards developing the next generation of models for VL.

The gp63 Gene Cluster Is Highly Polymorphic in Natural Leishmania (Viannia) braziliensis Populations, but Functional Sites Are Conserved

GP63 or leishmanolysin is the major surface protease of Leishmania spp. involved in parasite virulence and host cell interaction. As such, GP63 is a potential target of eventual vaccines against these protozoa. In the current study we evaluate the polymorphism of gp63 in Leishmania (Viannia) braziliensis isolated from two sets of American tegumentary leishmaniasis (ATL) cases from Corte de Pedra, Brazil, including 35 cases diagnosed between 1994 and 2001 and 6 cases diagnosed between 2008 and 2011. Parasites were obtained from lesions by needle aspiration and cultivation. Genomic DNA was extracted, and 405 bp fragments, including sequences encoding the putative macrophage interacting sites, were amplified from gp63 genes of all isolates. DNA amplicons were cloned into plasmid vectors and ten clones per L. (V.) braziliensis isolate were sequenced. Alignment of cloned sequences showed extensive polymorphism among gp63 genes within, and between parasite isolates. Overall, 45 different polymorphic alleles were detected in all samples, which could be segregated into two clusters. Cluster one included 25, and cluster two included 20 such genotypes. The predicted peptides showed overall conservation below 50%. In marked contrast, the conservation at segments with putative functional domains approached 90% (Fisher’s exact test p<0.0001). These findings show that gp63 is very polymorphic even among parasites from a same endemic focus, but the functional domains interacting with the mammalian host environment are conserved.

Detection of IgG Anti-Leishmania Antigen by Flow Cytometry as a Diagnostic Test for Cutaneous Leishmaniasis

Diagnosis of cutaneous leishmaniasis (CL) relies on clinical presentation, parasite isolation, histopathologic evaluation and positive Montenegro skin test. However, the low amounts of parasites in the lesion of these individuals make parasite isolation and histopatologic diagnosis unreliable, often leading to false-negative results. Also, 15% of people living in endemic areas have sub-clinical infection characterized by positive Montenegro skin test, which may contribute to misdiagnosis. Although the main Leishmania killing mechanism is through cell-mediated immune response, antibodies against Leishmania antigens are found in infected individuals. Here our goal was to develop a new serological technique using polystyrene microspheres sensitized with soluble Leishmania antigens as a tool for the detection of IgG in serum from CL patients by flow cytometry. To validate the assay we carried out a comparative test (ELISA) commonly used as a diagnostic test for parasitic diseases. To determine cross-reactivity we used serum from patients with Chagas disease, caused by a trypanosome that has several proteins with high homology to those of the Leishmania genus. We observed that the flow cytometry technique was more sensitive than the ELISA, but, less specific. Our results show that the flow cytometry serologic test can be used to confirm CL cases in L. braziliensis transmission areas, however, presence of Chagas disease has to be ruled out in these individuals.

Molecular detection of infection homogeneity and impact of miltefosine treatment in a Syrian golden hamster model of Leishmania donovani and L. infantum visceral leishmaniasis

Control of visceral leishmaniasis caused by Leishmania infantum and Leishmania donovani primarily relies on chemotherapy using an increasingly compromised repertoire of antileishmanial compounds. For evaluation of novel drugs, the Syrian golden hamster is considered as a clinically relevant laboratory model. In this study, two molecular parasite detection assays were developed targeting cathepsin-like cysteine protease B (CPB) DNA and 18S rRNA to achieve absolute amastigote quantification in the major target organs liver and spleen. Both quantitative PCR (qPCR) techniques showed excellent agreement with a strong correlation with the conventional microscopic reading of Giemsa-stained tissue smears. Using multiple single tissue pieces and all three detection methods, we confirmed homogeneity of infection in liver and spleen and the robustness of extrapolating whole organ burdens from a small single tissue piece. Comparison of pre- and post-treatment burdens in infected hamsters using the three detection methods consistently revealed a stronger parasite reduction in the spleen compared to the liver, indicating an organ-dependent clearance efficacy for miltefosine. In conclusion, this study in the hamster demonstrated high homogeneity of infection in liver and spleen and advocates the use of molecular detection methods for assessment of low (post-treatment) tissue burdens.

Development of real-time PCR assays for evaluation of immune response and parasite load in golden hamster (Mesocricetus auratus) infected by Leishmania (Viannia) braziliensis

Background

Cutaneous leishmaniasis (CL) is a neglected disease with a broad spectrum of clinical manifestations, ranging from small cutaneous nodules to severe mucosal tissue destruction. Leishmania (Viannia) braziliensis is the main species attributed to CL in the Americas. However, studies of experimental infection are limited in the murine model due to the self-resolutive pattern of the disease. Previously, our group demonstrated that the hamster model reproduces many of the clinical and histopathological features observed in humans. Herein, we standardized a RT-qPCR gene expression assay to evaluate a panel of immunological markers and a qPCR assay in order to quantify with high sensitivity and reproducibility the parasite load in skin lesions.

Methods

Hamsters were intradermally infected in the footpad with 10⁵ promastigotes of L. (V.) braziliensis and 110 days post-infection skin lesions and popliteal lymph nodes were removed for RNA and DNA extraction, both from the same tissue fragment. Gene expression of IFN-ɣ, IL-10, TGF-β TNF, IL-4, IL-6, iNOS and arginase were measured using non-infected animal tissue as a calibrator. Parasite load was quantified from DNA extracted from lesions by qPCR targeting Leishmania kDNA and normalized by hamster GAPDH, using a SYBR Green-based absolute quantification methodology.

Results

A relative quantification RT-qPCR assay was standardized for the evaluation of mRNA levels from skin and lymph node samples of golden hamsters, with PCR efficiencies ranging from 92.3 to 116.4 %. In uninfected animals, higher basal mRNA levels in lymph nodes were observed for IFN-ɣ, TGF-β, TNF and IL-4 (111.4 ± 92.2; 5.6 ± 1.2; 5.3 ± 1.7; and 60.3 ± 26.8, respectively) in comparison to skin. In golden hamsters infected with L. (V.) braziliensis, an increase in the expression of all immunological markers evaluated was observed, ranging from 2.7 ± 0.2 for TGF-β to 1018.5 ± 809.0 for iNOS in skin lesions, and 2.4 ± 1.6 for TGF-β to 600.2 ± 666.4 for iNOS in popliteal lymph nodes. Interestingly, significantly higher levels of IFN-ɣ, TNF and IL-10 mRNA were observed in skin in comparison to lymph nodes, while a lower significant level of arginase mRNA was observed in skin. In parallel, parasite loads were quantified by qPCR from the skin lesions of infected animals, ranging from 27.0 to 6647.0, with a median of 553.4 (416.7–1504.0) parasites/mg skin equivalents, whereas lesion size varied from 0.3 to 3.1 mm. Despite the tendency of larger lesions to present higher parasite load, the correlation observed was not statistically significant.

Conclusions

In this study, we describe for the first time a sensitive, reproducible and cheaper molecular assay to quantify from the same tissue fragment the gene expression of immunological markers and the parasite load in skin lesions, observing a mixed profile of immune response in the hamster model infected by L. (V.) braziliensis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1647-6) contains supplementary material, which is available to authorized users.

Immunologic Markers of Protection in Leishmania (Viannia) braziliensis Infection: A 5-Year Cohort Study

BACKGROUND

The control of Leishmania braziliensis by individuals with subclinical infection (SC) are unknown.

METHODS

A cohort of 308 household contacts (HCs) of patients with cutaneous leishmaniasis (CL) was established in 2010 in an endemic area and followed up for 5 years. Whole-blood cultures stimulated with soluble Leishmania antigen and a Leishmania skin test (LST) were performed in years 0, 2, and 4. The identification of the lymphocyte subsets secreting interferon (IFN) γ and the ability of monocytes to control Leishmania were determined.

RESULTS

During follow-up, 118 subjects (38.3%) had evidence of L. braziliensis infection. Of the HCs, CL was documented in 45 (14.6%), 101 (32.8%) had SC infection, and 162 (52.6%) did not have evidence of exposure to L. braziliensis The ratio of infection to disease was 3.2:1. IFN-γ production, mainly by natural killer cells, was associated with protection, and a positive LST result did not prevent development of disease. Moreover, monocytes from subjects with SC infection were less permissive to parasite penetration and had a greater ability to control L. braziliensis than cells from patients with CL.

CONCLUSIONS

Protection against CL was associated with IFN-γ production, negative LST results, impaired ability of Leishmania to penetrate monocytes, and increased ability to control Leishmania growth.

Detection and quantification of Leishmania infantum in naturally and experimentally infected animal samples

Leishmania infantum is one of the causative agents of visceral leishmaniasis (VL). VL is the most severe form of leishmaniasis and can be fatal if it is not properly treated. Although several PCR works are intended to detect L. infantum, in silico analysis of available primers and/or primer-probes reveals potential cross species amplification. Here, a TaqMan-based quantitative real time PCR (qPCR) assay was developed for specific detection and quantitation of L. infantum in tissue samples from experimentally or naturally infected animals, mice or dogs, respectively. For this assay, primers and probes were designed for the kinetoplast minicircle DNA of L. infantum. The qPCR assay achieved a detection limit of 0.01pg of parasite DNA, and allowed specific amplification of L. infantum in both asymptomatic and symptomatic naturally infected dogs with inter-assay variation coefficients between 0.05-0.11. There was no cross amplification with dog DNA or with L. braziliensis, L. donovani, L. major, L. tropica or Trypanosoma cruzi. In addition, our assay detected a significantly higher parasite load in symptomatic than in the asymptomatic animals (p<0.0001). We believe this approach will be a valuable tool for the specific detection of L. infantum in regions of sympatric transmission of VL-causing parasites.

Characterization of Neutrophil Function in Human Cutaneous Leishmaniasis Caused by Leishmania braziliensis

Infection with different Leishmania spp. protozoa can lead to a variety of clinical syndromes associated in many cases with inflammatory responses in the skin. Although macrophages harbor the majority of parasites throughout chronic infection, neutrophils are the first inflammatory cells to migrate to the site of infection. Whether neutrophils promote parasite clearance or exacerbate disease in murine models varies depending on the susceptible or resistant status of the host. Based on the hypothesis that neutrophils contribute to a systemic inflammatory state in humans with symptomatic L. braziliensis infection, we evaluated the phenotype of neutrophils from patients with cutaneous leishmaniasis (CL) during the course of L. braziliensis infection. After in vitro infection with L. braziliensis, CL patient neutrophils produced more reactive oxygen species (ROS) and higher levels of CXCL8 and CXCL9, chemokines associated with recruitment of neutrophils and Th1-type cells, than neutrophils from control healthy subjects (HS). Despite this, CL patient and HS neutrophils were equally capable of phagocytosis of L. braziliensis. There was no difference between the degree of activation of neutrophils from CL versus healthy subjects, assessed by CD66b and CD62L expression using flow cytometry. Of interest, these studies revealed that both parasite-infected and bystander neutrophils became activated during incubation with L. braziliensis. The enhanced ROS and chemokine production in neutrophils from CL patients reverted to baseline after treatment of disease. These data suggest that the circulating neutrophils during CL are not necessarily more microbicidal, but they have a more pro-inflammatory profile after parasite restimulation than neutrophils from healthy subjects.

Leishmania spp. are protozoan parasites that cause a spectrum of human diseases, and L. braziliensis causes chronic inflammatory skin lesions in residents of endemic regions of Latin America. Leishmania are obligate intracellular parasites in mammalian hosts, found in macrophages throughout infection. Nonetheless, other cell types including neutrophils also take up the parasite, but the role of neutrophils throughout chronic leishmaniasis remains unclear. We analyzed circulating neutrophils from patients in northeast Brazil with cutaneous leishmaniasis (CL) caused by L. braziliensis, compared to healthy controls from the same region. Our data revealed that neutrophils from both infected and healthy hosts took up comparable numbers of parasites, and parasite phagocytosis induced similar degrees of neutrophil activation. However, CL patient neutrophils produced more reactive oxidants than control neutrophils, and increased amounts of the chemokines CXCL8 and CXCL9 after parasite exposure. Interestingly, according to surface markers of PMN activation (CD62L, CD66b), we found that L. braziliensis activates both infected and uninfected “bystander” neutrophils from both patients and controls. Importantly, repeated measures showed the production of reactive oxidants and chemokine release were significantly decreased after therapeutic cure of infection. These data suggest that CL promotes a heightened inflammatory state in circulating neutrophils during active infection.

Real-time PCR using FRET technology for Old World cutaneous leishmaniasis species differentiation

Background

Recently, there has been a re-emergence of cutaneous leishmaniasis in endemic countries and an increase in imported cases in non-endemic countries by travelers, workers, expatriates, immigrants, and military force personnel. Old World cutaneous leishmaniasis is caused primarily by Leishmania major, L. tropica and L. aethiopica. Despite their low sensitivity, diagnosis traditionally includes microscopic and histopathological examinations, and in vitro cultivation. Several conventional PCR techniques have been developed for species identification, which are time-consuming and labour-intensive. Real-time PCR using SYBR green dye, although provides rapid detection, may generate false positive signals. Therefore, a rapid and easy method such as a FRET-based real-time PCR would improve not only the turn-around time of diagnosing Old World cutaneous Leishmania species but will also increase its specificity and sensitivity.

Methods

A FRET-based real-time PCR assay which amplifies the cathepsin L-like cysteine protease B gene encoding a major Leishmania antigen was developed to differentiate L. major, L. tropica, and L. aethiopica in one single step using one set of primers and probes. Assay performance was tested on cutaneous and visceral strains of Leishmania parasite cultures and isolates of other protozoan parasites as well as human biopsy specimen.

Results

The assay readily differentiates between the three Old World cutaneous leishmaniasis species based on their melting curve characteristics. A single Tm at 55.2 ± 0.5 °C for L. aethiopica strains was distinguished from a single Tm at 57.4 ± 0.2 °C for L. major strains. A double curve with melting peaks at 66.6 ± 0.1 °C and 48.1 ± 0.5 °C or 55.8 ± 0.6 °C was observed for all L. tropica strains. The assay was further tested on biopsy specimens, which showed 100 % agreement with results obtained from isoenzyme electrophoresis and Sanger sequencing.

Conclusion

Currently, there are no published data on real-time PCR using FRET technology to differentiate between Old World cutaneous Leishmania species. In summary, our assay based on specific hybridization addresses the limitations of previous PCR technology and provides a single step, reliable method of species identification and rapid diagnostic applications.

Cutaneous and mucocutaneous leishmaniasis: Differential diagnosis, diagnosis, histopathology, and management

The diagnosis of leishmaniasis can be challenging because it mimics both infectious and malignant conditions. A misdiagnosis may lead to an unfavorable outcome. Using culture, histologic, and/or polymerase chain reaction study results, a diagnosis of leishmaniasis can be established and treatment initiated. Appropriate management requires an accurate diagnosis, which often includes identification of the specific etiologic species. Different endemic areas have varying sensitivities to the same medication, even within individual species. Species identification may be of practical value, because infections with select species have a substantial risk of visceral involvement. In addition, HIV and otherwise immunocompromised patients with leishmaniasis have a propensity for diffuse cutaneous leishmaniasis. For most New World Leishmania species, parenteral antimonial drugs remain the first line of therapy, while Old World species are easily treated with physical modalities. Historically, live organism vaccination has been used and is effective in preventing leishmaniasis, but results in an inoculation scar and an incubation period that may last for years. A more effective method of vaccination would be welcome.

Real-time PCR for Leishmania species identification: Evaluation and comparison with classical techniques

BACKGROUND

Cutaneous leishmaniasis (CL) is a parasitic disease caused by various Leishmania species. Several studies have shown that real time quantitative PCR (qPCR) can be used for Leishmania spp. identification by analyzing the melting temperature (Tm). Thus, the aim of this study was to evaluate the viability of qPCR for differentiating eight closely related Leishmania species that cause the same clinical form of the disease and to compare the results with classical techniques.

METHODS

qPCR assays for standardizing the Tm using reference strains were performed. After the CL diagnosis on blood samples of domestic animals, positive samples were analyzed by their Tm and qPCR products were purified and sequenced. Ten human samples previously characterized by Multilocus Enzyme Electrophoresis (MLEE) were also analyzed by Tm. A Restriction Fragment Length Polymorphism (RFLP) assay, a reference test, was also standardized, by using the reference strains.

RESULTS

Through standardization of Tm for Leishmania spp., two Tm ranges were created for analysis: 1 (Tm = 78-79.99 °C) included Leishmania (V.) braziliensis, Leishmania (V.) panamensis, Leishmania (V.) lainsoni, Leishmania (V.) guyanensis and Leishmania (V.) shawi; and 2 (Tm = 80-82.2 °C) included Leishmania (V.) naiffi, Leishmania (L.) amazonensis and Leishmania (L.) mexicana. A total of 223 positive blood samples were analyzed, with 58 included in range 1 and 165 in range 2. L. (V.) braziliensis, L. (V.) panamensis and L. (V.) guyanensis were identified by sequencing, while L. (V.) braziliensis, L. (L.) mexicana and L. (V.) panamensis were identified by RFLP analysis. Ten human samples previously characterized by Multilocus Enzyme Electrophoresis (MLEE) were also analyzed by qPCR Tm analysis; five were classified in range 1 and five in range 2. A concordance of 80% was calculated between qPCR and the gold-standard (MLEE) with no significant difference between the methods (p = 0.6499); a similar result was observed for sequencing and qPCR (p = 0.2566). In contrast, a highly significant difference was observed for qPCR and RFLP (p < 0.001).

CONCLUSIONS

In this study, we demonstrated the potential use of qPCR as a tool for Leishmania species identification using two Tm ranges.

Leishmania major: Genetic Profiles of the Parasites Isolated from Chabahar, Southeastern Iran by PPIP-PCR

BACKGROUND

Leishmaniasis is important vector-borne parasitic disease worldwide, caused by the genus Leishmania. The objective of the current study was to identify genetic polymorphism in L. major, one of the species causing cutaneous leishmaniasis (CL), isolated from southeastern Iran, using Permissively Primed Intergenic Polymorphic-Polymerase Chain Reaction (PPIP-PCR) method.

METHODS

Overall, 340 patients with suspected CL were examined. They referred to the Central Laboratory in Chabahar, Iran during Apr 2013 to Feb 2014. Microscopic examination of Giemsa-stained slides from lesions as well as aspirates cultured in Novy- Mac Neal-Nicolle (NNN) Media was employed in order to diagnose CL in these patients. Our analyses detected 86 suspected subjects as having CL from which 35 isolates were cultured successfully. PPIP-PCR method was performed on extracted genomic DNA from selected isolates in order to determine the genetic polymorphism among L. major isolates.

RESULTS

The electrophoresis patterns demonstrated two genetic profiles including A or A1 patterns between all samples tested. Frequency of A and A1 sub-types were 33 (94.3%) and two (5.7%), respectively.

CONCLUSION

Both host and parasite factors may contribute to the clinical profile of human leishmaniasis in the endemic foci of the disease. Here we showed that genetic variations pertaining to the Leishmania parasites might determine, in part, the clinical outcomes of human leishmaniasis.

Implications of co-infection of Leptomonas in visceral leishmaniasis in India

Protozoan parasites Leishmania donovani (family: Trypanosomatidae) cause fatal visceral leishmaniasis (VL) and the infection relapses in apparently cured population as post kala-azar dermal leishmaniasis (PKDL) in the Indian subcontinent. In recent years co-infection of another Trypanosomatid parasite Leptomonas with L. donovani during VL/PKDL in this region has become prominent. The observation of clinically lesser-known insect parasite, Leptomonas in leishmaniasis is intriguing to researchers. The presence of Leishmania look alike Leptomonas in the cultures of clinical isolates of Leishmania has been worrisome to those, who prefer to work with pure Leishmania cultures for drug and vaccine development or immune response studies. The exact implications of such a co-habitation, which might lead to a delay in the diagnostics of VL and elevate mortality, need a thorough investigation. Also whether Leptomonas is involved in leishmaniasis manifestation needs to be ascertained. Thus we are currently witnessing a new paradigm of a parasitic co-infection in VL/PKDL cases in India and this review outlines various opportunities for further research in understanding such emerging co-infection.

A Potential Role for Mononuclear Phagocytes in Cutaneous Ulcer Development in Human Immunodeficiency Virus-Leishmania braziliensis Coinfection

Skin ulcer development in cutaneous leishmaniasis due to Leishmania braziliensis infection is associated with a mononuclear cell infiltrate and high levels of tumor necrosis factor (TNF). Herein, we show that despite the absence of Leishmania-driven TNF, a cutaneous leishmaniasis patient with acquired immunodeficiency syndrome developed a skin ulcer. The presence of mononuclear phagocytes and high levels of TNF, chemokine (C-C motif) ligand 2 (CCL2), and metalloproteinase-9 in tissue are identified as potential contributors to immunopathology observed in L. braziliensis-infected patients.

Correlation between presence of Leishmania RNA virus 1 and clinical characteristics of nasal mucosal leishmaniosis

Introduction

Mucosal leishmaniosis (ML) is a severe clinical form of leishmaniosis. Complex factors related to the parasite and the host are attributed to the development of mucosal lesions. Leishmania RNA virus 1 (LRV1) can disrupt immune response, and may be the main determinant of severity of the disease; it should be investigated.

Objective

To study the existence of clinical differences between patients with ML with endosymbiosis by LRV1 and. those without it.

Methods

A cross-sectional cohort study with clinical evaluation, polymerase chain reaction (PCR) detection of Leishmania, species classification, and search of LRV1 was performed. Only patients with confirmed diagnosis of ML by positive PCR and with nasal mucosa injuries were included in this analysis.

Results

Out of 37 patients, 30 (81.1%) were diagnosed with Leishmania braziliensis, five (13.5%) with Leishmania guyanensis, and two (5.4%) with mixed infection of L. braziliensis and L. guyanensis. LVR1 virus was present in 26 (70.3%) of the cases.

Conclusion

Correlation between clinical phenotype and presence of LRV1 was not observed, although the frequency of the virus is two-fold higher in mucosal lesions than that found in the literature on skin lesions in the same geographical area.

Leishmaniases diagnosis: an update on the use of immunological and molecular tools

Leishmaniases are caused by obligate intracellular protozoan parasites of the genus Leishmania. They cause a spectrum of diseases, most notably visceral (VL), cutaneous (CL), and mucosal (ML) leishmaniasis, which affect millions of people around the world, each year. Despite scientific advances, leishmaniases cases are expanding, constituting an important public health problem. Immunological and molecular diagnostic tools have been increasingly applied for the early detection of these parasitic infections, since the existence of limitations in clinical and parasitological examinations may provide false results, thus interfering in epidemiological research and diseases control. Although there is a great diversity of available immunological assays, important common deficiencies persist, which explains the current exploration of the molecular biology in research fields, especially the Polymerase Chain Reaction (PCR) and its variants, such as real-time quantitative PCR. However, in the last years, significant results have also been reached inside of immunological context (especially by Flow Cytometry), for humans and dogs, demonstrated by research works of the New and Old worlds. In spite of their potential to clarify and minimize the present global situation of the diseases, the implementation of molecular or immunological innovative reference assays for VL and CL at health services is still a challenge due to several reasons, including lack of standardization among laboratories and structural concerns. In this article we bring classical and current information about technological advances for the immunological and molecular leishmaniases diagnosis, their features, and applications.

Age modifies the immunologic response and clinical presentation of American tegumentary leishmaniasis

Leishmania (Viannia) braziliensis is the main causal agent of American tegumentary leishmaniasis (ATL) that may present as cutaneous, mucosal, or disseminated cutaneous leishmaniasis. The disease is highly prevalent in young males and there is a lack of studies of ATL in the elderly. Herein, we compared clinical manifestations, immunologic response, and response to antimony therapy between patients > 60 years of age (N = 58) and patients who were 21-30 years of age (N = 187). The study was performed in Corte de Pedra, Bahia, Brazil, a well-known area of L. braziliensis transmission. Cytokine production by cultured peripheral blood mononuclear cells stimulated with soluble Leishmania antigen was performed. Elderly subjects more frequently had a previous history of cutaneous leishmaniasis, large lesions, or mucosal leishmaniasis, and they were less likely to have lymphadenopathy. There was no difference regarding gender and response to therapy. Peripheral blood mononuclear cells from elderly subjects produced a similar amount of tumor necrosis factor than young patients but they produced less interferon-gamma and more interleukin-10 than young subjects. We concluded that elderly patients with cutaneous leishmaniasis should be searched for mucosal or disseminated leishmaniasis. The decreased interferon-gamma production and increase in interleukin-10 observed in elderly patients may contribute to parasite persistence and L. braziliensis infection dissemination.

Complementary exams in the diagnosis of American tegumentary leishmaniasis

The diagnosis of American Tegumentary Leishmaniasis is a difficult but essential task when considering the high toxicity profile of the drugs available. Since the discovery of its etiologic agent, numerous diagnostic tests have been developed. None of the tests available today can be considered as the gold standard, since they do not add enough accuracy for the disease detection. Good epidemiological and clinical knowledge of the disease are fundamental precepts of the dermatology practice and precede the rational use of existing diagnostic tests. In this article we aim, through extensive literature review, to recall fundamental concepts of any diagnostic test. Subsequently, based on this information, we will weave important comments about the characteristics of existing diagnostic tests, including immunological tests such as Montenegro's skin test, serology and detection of parasites by direct examination, culture or histopathology. Finally we will discuss the new technologies and options for the diagnosis of Cutaneous Leishmaniasis. The molecular biology technique is considered a promising tool, promoting the rapid identification of the species involved. We also aim to educate dermatologists about a disease with high morbidity and assist in its difficult recognition.

Species typing in dermal leishmaniasis

Leishmania is an infectious protozoan parasite related to African and American trypanosomes. All Leishmania species that are pathogenic to humans can cause dermal disease. When one is confronted with cutaneous leishmaniasis, identification of the causative species is relevant in both clinical and epidemiological studies, case management, and control. This review gives an overview of the currently existing and most used assays for species discrimination, with a critical appraisal of the limitations of each technique. The consensus taxonomy for the genus is outlined, including debatable species designations. Finally, a numerical literature analysis is presented that describes which methods are most used in various countries and regions in the world, and for which purposes.

Molecular epidemiology of imported cases of leishmaniasis in Australia from 2008 to 2014

Leishmaniasis is a vector borne disease caused by protozoa of the genus Leishmania. Human leishmaniasis is not endemic in Australia though imported cases are regularly encountered. This study aimed to provide an update on the molecular epidemiology of imported leishmaniasis in Australia. Of a total of 206 biopsies and bone marrow specimens submitted to St Vincent’s Hospital Sydney for leishmaniasis diagnosis by PCR, 55 were found to be positive for Leishmania DNA. All PCR products were subjected to restriction fragment length polymorphism analysis for identification of the causative species. Five Leishmania species/species complexes were identified with Leishmania tropica being the most common (30/55). Travel or prior residence in a Leishmania endemic region was the most common route of acquisition with ~47% of patients having lived in or travelled to Afghanistan. Cutaneous leishmaniasis was the most common manifestation (94%) with only 3 cases of visceral leishmaniasis and no cases of mucocutaneous leishmaniasis encountered. This report indicates that imported leishmaniasis is becoming increasingly common in Australia due to an increase in global travel and immigration. As such, Australian clinicians must be made aware of this trend and consider leishmaniasis in patients with suspicious symptoms and a history of travel in endemic areas. This study also discusses the recent identification of a unique Leishmania species found in native kangaroos and a potential vector host which could create the opportunity for the establishment of a local transmission cycle within humans.

Immune response to Leishmania antigens in an AIDS patient with mucocutaneous leishmaniasis as a manifestation of immune reconstitution inflammatory syndrome (IRIS): a case report

BACKGROUND

After the onset of HAART, some HIV-infected individuals under treatment present a exacerbated inflammation in response to a latent or a previously treated opportunistic pathogen termed immune reconstitution inflammatory syndrome (IRIS). Few reports of tegumentary leishmaniasis have been described in association with IRIS. Moreover, the immunopathogenesis of IRIS in association with Leishmania is unclear.

CASE PRESENTATION

The present study reports on a 29-year-old HIV-infected individual who developed mucocutaneous leishmaniasis associated with immune reconstitution inflammatory syndrome (IRIS) five months following highly active antiretroviral therapy (HAART). Severe lesions resulted in the partial destruction of the nasal septum, with improvement observed 15 days after treatment with Amphotericin B and corticosteroids. The immune response of this patient was evaluated before and after the lesions healed. IRIS was diagnosed in association with high levels of TNF-α and IL-6. Decreased production of IFN-γ and a low IFN-γ/IL-10 ratio were also observed in response to Leishmania antigens. After receiving anti-leishmanial treatment, the individual's specific Th1 immune response was restored.

CONCLUSION

The results suggest that the production of inflammatory cytokines by unstimulated T-lymphocytes could contribute to occurrence of leishmaniasis associated with IRIS.

Selective elimination of Leptomonas from the in vitro co-culture with Leishmania

Leishmania and Leptomonas are protozoan parasites of the family Trypanosomatidae. Leishmania donovani causes the fatal visceral leishmaniasis (VL; kala-azar) in mammals and is transmitted by sand fly vector. Certain VL-cured human populations in India and Sudan develop post kala-azar dermal leishmaniasis (PKDL) due to the same parasite. Although Leptomonas is parasitic mainly in insects, several recent reports on the clinical isolates of L. donovani from VL and PKDL patients in India confirm co-infection of Leptomonas seymouri, probably due to immune suppression in those individuals. Detection of L. seymouri in the in vitro cultures of L. donovani from clinical origin is difficult due to many similarities between L. seymouri and L. donovani. We describe here ways to detect L. seymouri and L. donovani in co-culture. In addition, based on our observation regarding the growth of L. seymouri in different culture conditions, we report here a novel procedure, which can selectively eliminate L. seymouri from the in vitro co-culture with L. donovani. This would be beneficial to researchers who prefer to deal with pure populations of Leishmania parasites for various downstream immunological and genetic studies.

Quantitative PCR in epidemiology for early detection of visceral leishmaniasis cases in India

Introduction

Studies employing serological, DTH or conventional PCR techniques suggest a vast proportion of Leishmania infected individuals living in regions endemic for Visceral Leishmaniasis (VL) remain asymptomatic. This study was designed to assess whether quantitative PCR (qPCR) can be used for detection of asymptomatic or early Leishmania donovani infection and as a predictor of progression to symptomatic disease.

Methods

The study included 1469 healthy individuals living in endemic region (EHC) including both serology-positive and -negative subjects. TaqMan based qPCR assay was done on peripheral blood of each subject using kDNA specific primers and probes.

Results

A large proportion of EHC 511/1469 (34.78%) showed qPCR positivity and 56 (3.81% of 1469 subjects) had more than 1 calculated parasite genome/ml of blood. However, the number of individuals with parasite load above 5 genomes/ml was only 20 (1.36% of 1469). There was poor agreement between serological testing and qPCR (k = 0.1303), and 42.89% and 31.83% EHC were qPCR positive in seropositive and seronegative groups, respectively. Ten subjects had developed to symptomatic VL after 12 month of their follow up examination, of which eight were initially positive according to qPCR and among these, five had high parasite load.

Discussion

Thus, qPCR can help us to detect significant early parasitaemia, thereby assisting us in recognition of potential progressors to clinical disease. This test could facilitate early intervention, decreased morbidity and mortality, and possibly interruption of disease transmission.

Anthroponotic VL caused by Leishmania donovani in the Indian subcontinent accounts for 70% of the world burden of VL. Among the estimated 100,000 cases of VL acquired annually in India, 90% occur in the state of Bihar. Leishmania infection can result in either symptomatic or asymptomatic infection. L. donovani infection can also manifest as post-kala azar dermal leishmaniasis, a chronic cutaneous form thought to provide the reservoir for anthroponotic transmission of VL in regions endemic for this parasite species. We hypothesized that, in areas endemic for L. donovani, asymptomatic infections might also play a crucial role in disease transmission. This study describes use of quantitative PCR (qPCR) to determine the infection status in individuals living in an endemic region of India. We hypothesized that parasite load estimation by qPCR of peripheral blood cells among healthy individuals living in the endemic region might reveal the true frequency of infections through direct evidence of parasitemia. We reasoned this test would detect both asymptomatic non-progressors as well as asymptomatic individuals who will progress to fully symptomatic VL. Serologic testing by ELISA or DAT showed poor agreement with molecular detection of parasite DNA by qPCR, suggesting the tests differentiate between infection and immune response. Amongst ten healthy individuals who progressed to VL, only six were serologically positive whereas eight were initially qPCR positive, among whom five had high parasite loads in their blood. Thus, deployment of qPCR technique to estimate the presence and level of parasitemia in healthy individuals from Leishmania endemic regions may contribute to early case detection, thereby reducing morbidity and mortality. Consistent with the goals of the VL control and elimination program, this early intervention approach could help interrupt disease transmission.

Identification of six New World Leishmania species through the implementation of a High-Resolution Melting (HRM) genotyping assay

Background

Leishmaniases are tropical zoonotic diseases, caused by parasites from the genus Leishmania. New World (NW) species are related to sylvatic cycles although urbanization processes have been reported in some South American Countries such as Colombia. This eco-epidemiological complexity imposes a challenge to the detection of circulating parasite species, not only related to human cases but also infecting vectors and reservoirs. Currently, no harmonized methods have been deployed to discriminate the NW Leishmania species.

Findings

Herein, we conducted a systematic and mechanistic High-Resolution Melting (HRM) assay targeted to HSP70 and ITS1. Specific primers were designed that coupled with a HRM analyses permitted to discriminate six NW Leishmania species. In order to validate the herein described algorithm, we included 35 natural isolates obtained from human cases, insect vectors and mammals. Our genotyping assay allowed the correct assignment of the six NW Leishmania species (L. mexicana, L. infantum (chagasi), L. amazonensis, L. panamensis, L. guyanensis and L. braziliensis) based on reference strains. When the algorithm was applied to a set of well-characterized strains by means of PCR-RFLP, MLEE and monoclonal antibodies (MA) we observed a tailored concordance between the HRM and PCR-RFLP/MLEE/MA (KI = 1.0). Additionally, we tested the limit of detection for the HRM method showing that this is able to detect at least 10 equivalent-parasites per mL.

Conclusions

This is a rapid and reliable method to conduct molecular epidemiology and host-parasite association studies in endemic areas.

Detection of a broad range of Leishmania species and determination of parasite load of infected mouse by real-time PCR targeting the arginine permease gene AAP3

Leishmaniasis is one of the world's most neglected infectious diseases, affecting around 12 million people and more than 350 million at risk of infection. The clinical picture varies from self-healing cutaneous lesions to severe visceral infections, but still no commercial vaccines for humans are available and the currently used drugs have unpleasant side effects. Here we report a real-time PCR assay targeting the arginine permease gene AAP3 that can be applied for all the nine different species of the Leishmania genus tested; 4 Old World species and 5 New World species, from both L. (Leishmania) and L. (Viannia) subgenera. No cross-reaction was seen with Trypanosoma cruzi, Trypanosoma brucei, human or mouse genomic DNA. The assay has a high sensitivity, with a limit of detection of 10fg DNA for L. (L.) major and L. (L.) donovani, and 100fg DNA for L. (V.) braziliensis, and can be used for both qualitative and quantitative purposes. This AAP3-Assay, run in duplex with a host specific gene-assay, was also successfully used for quantification of parasite load of footpads from L. (L.) major-infected mice. It can therefore be a valuable tool in applications like monitoring effects of drugs, the selection of vaccine candidates and in screening patients, including asymptomatic carriers.

Tr-1-like CD4+CD25-CD127-/lowFOXP3- cells are the main source of interleukin 10 in patients with cutaneous leishmaniasis due to Leishmania braziliensis

CD4(+)CD25(+)FOXP3(+) regulatory T cells have long been shown to mediate susceptibility to Leishmania infection, mainly via interleukin 10 production. In this work, we showed that the main sources of interleukin 10 in peripheral blood mononuclear cells (PBMCs) from patients with cutaneous leishmaniasis due to Leishmania braziliensis are CD4(+)CD25(-)CD127(-/low)FOXP3(-) cells. Compared with uninfected controls, patients with CL had increased frequencies of circulating interleukin 10-producing CD4(+)CD25(-)CD127(-/low) cells, which efficiently suppressed tumor necrosis factor α production by the total PBMC population. Also, in CL lesions, interleukin 10 was mainly produced by CD4(+)CD25(-) cells, and interleukin 10 messenger RNA expression was associated with interleukin 27, interleukin 21, and interferon γ expression, rather than with FOXP3 or transforming growth factor β expressions. Active production of both interleukin 27 and interleukin 21, together with production of interferon γ and interleukin 10, was also detected in the lesions. Since these cytokines are associated with the differentiation and activity of Tr-1 cells, our results suggest that this cell population may play an important role in the immunomodulation of CL. Therefore, development of treatments that interfere with this pathway may lead to faster parasite elimination.

A canine model of experimental infection with Leishmania (L.) mexicana

BACKGROUND

Cutaneous leishmaniasis is a tropical disease affecting over one million patients annually and Leishmania (L.) mexicana is one of the major etiological agents in the Americas. Here we established the first experimental infection of L. (L.) mexicana in canids.

METHODS

Beagle dogs were infected intradermally with culture-derived L. (L.) mexicana. We followed skin ulcer development, histopathological signs, parasite burden and the immune status of the infected dogs.

RESULTS

All infected dogs developed uniform oval-craterform ulcers similar to those observed in humans, associated with mixed T helper 1/T helper 2 immune responses. Parasites were detected in the healed lesions 15 weeks post-infection. Higher anti-Leishmania IgG levels correlated with larger lesions and high IgG1/IgG2 ratio was associated with some level of splenomegaly.

CONCLUSIONS

The canine model described in this work will be of use for further understanding of L. (L.) mexicana immunopathogenensis, and for drug and vaccine development.

Parasite load estimation by qPCR differentiates between asymptomatic and symptomatic infection in Indian visceral leishmaniasis

Using quantitative PCR (qPCR), we differentiated asymptomatic and symptomatic Indian Leishmania donovani infection. qPCR on blood of 40 visceral leishmaniasis, 130 endemic, and 40 non-endemic healthy controls showed 500 times less (P < .0001) parasitemia in asymptomatic compared to the symptomatic ones and threshold of 5 parasite genome/mL for the clinical disease.

Comparison between conventional and real-time PCR assays for diagnosis of visceral leishmaniasis

The diagnosis of visceral leishmaniasis (VL) is a challenging issue and several studies worldwide have evaluated the different tools to reach a diagnostic solution. The polymerase chain reaction (PCR) has proven to be effective in detecting the genome of Leishmania species in different biological samples. In this study, we compared the conventional PCR and real-time PCR using the Sybr Green system and their application in molecular diagnosis of visceral leishmaniasis in peripheral blood as a biological sample. The genus-specific conserved region of kinetoplast DNA (kDNA) was the target of amplification. We studied 30 samples from patients with suspect of visceral leishmaniasis who were treated by the Medical Clinic of Santa Casa de Belo Horizonte Hospital, Brazil. Among the samples studied, 19 had a confirmed diagnosis for VL by serology and/or by clinical findings. Among these 19 samples, 63% (n = 12) presented positive results for serology and 79% (n = 15) positive results in both PCR methodologies. This fact suggests that the PCR technique can assist in the diagnosis of visceral leishmaniasis in patients who do not have detectable antibodies by serology but can present the genome of the parasite circulating in whole blood. Also, it was possible to observe that there was conformity between the results of the techniques of cPCR and qPCR using the Sybr Green system in 100% of samples analyzed. These data suggest that both PCR techniques were equally effective for detection of the genome of the parasite in the patient's blood.

Molecular identification of Leishmania isolates obtained from patients suspected as having cutaneous leishmaniasis referred to reference laboratories from Yazd province in central Iran

Background:

Cutaneous leishmaniasis (CL) continues to be an increasing public health problem in Iran. The dominant etiologic agents of CL in the Old World are Leishmania major and Leishmania tropica. One of the important endemic foci of CL in Iran is Yazd. Recently, previous studies showed the equal prevalence of L. major and L. tropica as the agents of cutaneous leishmaniasis in this area. This prompted us to identify the genotype of L. major isolates obtained from patients with cutaneous leishmaniasis.

Materials and Methods:

After completing a clinical/epidemiologic data questionnaire for 218 patients with suspected skin lesions, scraping samples were collected, and each specimen was examined using both direct microscopy and molecular assay of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

Results:

Results showed that of the 218 samples, Leishman body was observed in 77 by direct smear and 104 by PCR assay. Molecular assay indicated 50 cases as L. major, 52 cases as L. tropica, and two cases as unknown. Molecular characterization of L. major isolates showed four patterns, named LmA1, LmA2, LmA3, and LmA4.

Conclusion:

Our study is the first report for molecular characterization of L. major from one of the important central province of Iran that could affect the control strategies in this field.

Association of pro-inflammatory cytokines and iron regulatory protein 2 (IRP2) with Leishmania burden in canine visceral leishmaniasis

Leishmania infantum infection in humans and dogs can evolve with a wide range of clinical presentations, varying from asymptomatic infections to visceral leishmaniasis. We hypothesized that the immune response elicited by L. infantum infection could modulate whether the host will remain asymptomatic or progress to disease. A total of 44 dogs naturally infected with L. infantum were studied. Leishmania burden was estimated in the blood and spleen by qPCR. The expression of IFN-γ, TNF-α, IL-10 and Iron Regulatory Protein 2 (IRP2) were determined in the spleen by quantitative PCR. Sera cytokines were evaluated by ELISA. Dogs were grouped in quartiles according parasite burden. Increased expression of IFN-γ and TNF-α was associated with reduced Leishmania burden, whereas increased IL-10 and IRP2 expressions were associated with higher Leishmania load. Increased plasma albumin and IFN-γ expression explained 22.8% of the decrease in parasite burden in the spleen. These data confirm that lower IFN-γ response and higher IL-10 correlated with increased parasite load and severity of the visceral leishmaniasis in dogs. The balance between the branches of immune response and the intracellular iron availability could determine, in part, the course of Leishmania infection.

Attenuation of Leishmania infantum chagasi metacyclic promastigotes by sterol depletion

The infectious metacyclic promastigotes of Leishmania protozoa establish infection in a mammalian host after they are deposited into the dermis by a sand fly vector. Several Leishmania virulence factors promote infection, including the glycosylphosphatidylinositol membrane-anchored major surface protease (MSP). Metacyclic Leishmania infantum chagasi promastigotes were treated with methyl-beta-cyclodextrin (MβCD), a sterol-chelating reagent, causing a 3-fold reduction in total cellular sterols as well as enhancing MSP release without affecting parasite viability in vitro. MβCD-treated promastigotes were more susceptible to complement-mediated lysis than untreated controls and reduced the parasite load 3-fold when inoculated into BALB/c mice. Paradoxically, MβCD-treated promastigotes caused a higher initial in vitro infection rate in human or murine macrophages than untreated controls, although their intracellular multiplication was hindered upon infection establishment. There was a corresponding larger amount of covalently bound C3b than iC3b on the parasite surfaces of MβCD-treated promastigotes exposed to healthy human serum in vitro, as well as loss of MSP, a protease that enhances C3b cleavage to iC3b. Mass spectrometry showed that MβCD promotes the release of proteins into the extracellular medium, including both MSP and MSP-like protein (MLP), from virulent metacyclic promastigotes. These data support the hypothesis that plasma membrane sterols are important for the virulence of Leishmania protozoa at least in part through retention of membrane virulence proteins.

Real-time PCR assay for detection and quantification of Leishmania (Viannia) organisms in skin and mucosal lesions: exploratory study of parasite load and clinical parameters

Earlier histopathology studies suggest that parasite loads may differ between cutaneous leishmaniasis (CL) and mucosal leishmaniasis (ML) lesions and between acute and chronic CL. Formal demonstration requires highly sensitive detection and accurate quantification of Leishmania in human lesional tissue. In this study, we developed a quantitative real-time PCR (qPCR) assay targeting minicircle kinetoplast DNA (kDNA) to detect and quantify Leishmania (Viannia) parasites. We evaluated a total of 156 lesion biopsy specimens from CL or ML suspected cases and compared the quantitative performance of our kDNA qPCR assay with that of a previously validated qPCR assay based on the glucose-6-phosphate dehydrogenase (G6PD) gene. We also examined the relationship between parasite load and clinical parameters. The kDNA qPCR sensitivity for Leishmania detection was 97.9%, and its specificity was 87.5%. The parasite loads quantified by kDNA qPCR and G6PD qPCR assays were highly correlated (r = 0.87; P < 0.0001), but the former showed higher sensitivity (P = 0.000). CL lesions had 10-fold-higher parasite loads than ML lesions (P = 0.009). Among CL patients, the parasite load was inversely correlated with disease duration (P = 0.004), but there was no difference in parasite load according to the parasite species, the patient's age, and number or area of lesions. Our findings confirm that CL and recent onset of disease (<3 months) are associated with a high parasite load. Our kDNA qPCR assay proved highly sensitive and accurate for the detection and quantification of Leishmania (Viannia) spp. in lesion biopsy specimens. It has potential application as a diagnostic and follow-up tool in American tegumentary leishmaniasis.

An approach for interlaboratory comparison of conventional and real-time PCR assays for diagnosis of human leishmaniasis

Protozoa of the Leishmania genus are transmitted to humans by the bite of infected sandflies, and are the causative agents of leishmaniasis which ranges from cutaneous to visceral clinical forms. The definitive diagnosis of leishmaniasis has relied traditionally on parasite demonstration, either by microscopy or culture; in the last years, diagnosis based on PCR methods has overcome some drawbacks of traditional methods, increasing sensitivity and allowing using less invasive sampling for diagnosis. However, there are not defined protocols and almost each laboratory applies its own in-house method. Although there are several studies comparing the performance of different methods within the same laboratory, those addressing interlaboratory comparison are scarce, in spite of the growing number of collaborative projects between partners from different leishmaniasis endemic and non-endemic countries. In this work we propose a protocol for interlaboratory comparison of conventional and real-time PCR methods involving four participant laboratories from four different endemic regions in four continents; the protocol includes a quality control step and reduces the variability among the samples tested by each participant. A panel of 77 samples from human origin and 9 from different parasite strains was blindly tested by the participants, aiming to assess the sensitivity of the different methods as well as their usefulness for species identification. Real-time PCR methods targeting the kDNA minicircles returned the highest sensitivity, while both PCR targeting ITS-1 and further HaeIII digestion and a combined algorithm including hsp70 PCR and restriction fragment length polymorphism analysis were the most appropriate approaches for species identification.

Microbial translocation induces an intense proinflammatory response in patients with visceral leishmaniasis and HIV type 1 coinfection

BACKGROUND

 Leishmania infection is a cofactor in the heightened cellular activation observed in patients with American visceral leishmaniasis and human immunodeficiency virus type 1 (HIV) infection, with or without progression to AIDS (AVL/HIV). Thus, the persistence of a high parasite load despite antileishmanial therapy could be responsible for the continued immune stimulation.

METHODS

 CD8(+) T cells expressing CD38, parasite load, lipopolysaccharide (LPS), soluble CD14, macrophage migration inhibitory factor (MIF), intestinal fatty acid-binding protein (IFABP), and proinflammatory cytokines (interleukin 1β, interleukin 6, interleukin 8, interleukin 17, interferon γ, and tumor necrosis factor) were measured in 17 patients with AVL/HIV, 16 with HIV, and 14 healthy subjects (HS).

RESULTS

 Lower Leishmania parasitemia was observed after antileishmanial and antiretroviral therapies. However, higher levels of CD38(+) on CD8(+) T cells were observed in both clinical phases of leishmaniasis, compared with HIV cases. AVL/HIV and HIV patients showed higher levels of LPS and IFABP than HS. Proinflammatory cytokine levels were significantly augmented in patients with active coinfection, as well as those with remission of Leishmania infection. LPS levels and Leishmania infection were positively correlated with CD38 expression on CD8(+) T cells and with IL-6 and IL-8 levels.

CONCLUSIONS

 LPS levels along with the immune consequences of Leishmania infection were associated with elevated cellular activation in coinfected patients. As a consequence, secondary chemoprophylaxis for leishmaniasis or even the use of antiinflammatory drugs or antibiotics may be considered for improving the prognosis of AVL/HIV.

SOLiD™ sequencing of genomes of clinical isolates of Leishmania donovani from India confirm leptomonas co-infection and raise some key questions

BACKGROUND

Known as 'neglected disease' because relatively little effort has been applied to finding cures, leishmaniasis kills more than 150,000 people every year and debilitates millions more. Visceral leishmaniasis (VL), also called Kala Azar (KA) or black fever in India, claims around 20,000 lives every year. Whole genome analysis presents an excellent means to identify new targets for drugs, vaccine and diagnostics development, and also provide an avenue into the biological basis of parasite virulence in the L. donovani complex prevalent in India.

METHODOLOGY/PRINCIPAL FINDINGS

In our presently described study, the next generation SOLiD™ platform was successfully utilized for the first time to carry out whole genome sequencing of L. donovani clinical isolates from India. We report the exceptional occurrence of insect trypanosomatids in clinical cases of visceral leishmaniasis (Kala Azar) patients in India. We confirm with whole genome sequencing analysis data that isolates which were sequenced from Kala Azar (visceral leishmaniasis) cases were genetically related to Leptomonas. The co-infection in splenic aspirate of these patients with a species of Leptomonas and how likely is it that the infection might be pathogenic, are key questions which need to be investigated. We discuss our results in the context of some important probable hypothesis in this article.

CONCLUSIONS/SIGNIFICANCE

Our intriguing results of unusual cases of Kala Azar found to be most similar to Leptomonas species put forth important clinical implications for the treatment of Kala Azar in India. Leptomonas have been shown to be highly susceptible to several standard leishmaniacides in vitro. There is very little divergence among these two species viz. Leishmania sp. and L. seymouri, in terms of genomic sequence and organization. A more extensive perception of the phenomenon of co-infection needs to be addressed from molecular pathogenesis and eco-epidemiological standpoint.

A FRET-based real-time PCR assay to identify the main causal agents of New World tegumentary leishmaniasis

In South America, various species of Leishmania are endemic and cause New World tegumentary leishmaniasis (NWTL). The correct identification of these species is critical for adequate clinical management and surveillance activities. We developed a real-time polymerase chain reaction (PCR) assay and evaluated its diagnostic performance using 64 archived parasite isolates and 192 prospectively identified samples collected from individuals with suspected leishmaniasis enrolled at two reference clinics in Lima, Peru. The real-time PCR assay was able to detect a single parasite and provided unambiguous melting peaks for five Leishmania species of the Viannia subgenus that are highly prevalent in South America: L. (V.) braziliensis, L. (V.) panamensis, L. (V.) guyanensis, L. (V.) peruviana and L. (V.) lainsoni. Using kinetoplastid DNA-based PCR as a gold standard, the real-time PCR had sensitivity and specificity values of 92% and 77%, respectively, which were significantly higher than those of conventional tests such as microscopy, culture and the leishmanin skin test (LST). In addition, the real-time PCR identified 147 different clinical samples at the species level, providing an overall agreement of 100% when compared to multilocus sequence typing (MLST) data performed on a subset of these samples. Furthermore, the real-time PCR was three times faster and five times less expensive when compared to PCR - MLST for species identification from clinical specimens. In summary, this new assay represents a cost-effective and reliable alternative for the identification of the main species causing NWTL in South America.

Leishmaniasis is a neglected disease with more than two million new human infections annually worldwide. Tegumentary leishmaniasis, cutaneous and mucocutaneous, is mainly caused by five Leishmania species of the Viannia complex in South America. Different species can cause disease with similar symptoms but have dissimilar prognoses and may need different therapeutic regimens. Identification of Leishmania species traditionally relies on the multilocus enzyme electrophoresis (MLEE) assay, but it can only be applied to culture-positive samples and takes at least six weeks of intense laboratory work. A reliable and rapid assay for species identification can be a valuable tool. Molecular assays are the fastest and most accurate way to identify the etiological agents causing leishmaniasis. This paper describes a novel real-time PCR assay for identification of the five main species that cause tegumentary leishmaniasis in the New World. The assay correctly identified each of these five species of Leishmania directly from clinical samples. Because of its reliability, speed and simplicity, this assay could be used for species identification in routine laboratory diagnosis of leishmaniasis in endemic regions.

Association between an emerging disseminated form of leishmaniasis and Leishmania (Viannia) braziliensis strain polymorphisms

Leishmania (Viannia) braziliensis causes three main types of American tegumentary leishmaniasis (ATL), localized cutaneous leishmaniasis (CL), mucosal leishmaniasis (ML), and disseminated leishmaniasis (DL). All forms are observed among individuals of Corte de Pedra, Brazil. We previously used random amplified markers to identify a multiclonal population among L. (V.) braziliensis isolates from ATL patients, defining parasite clades associated with different clinical syndromes. Herein we compared sequences of random amplified markers to identify genotypes of L. (V.) braziliensis recovered from lesions of CL, ML, and DL patients. Six polymorphic genomic loci were sequenced from 35 parasite isolates. Single-nucleotide polymorphisms (SNPs) and insertions-deletions (indels) at each locus allowed us to segregate the L. (V.) braziliensis population according to haplotypes. Several SNPs, indels, and haplotypes were significantly associated with an increased risk of DL. Molecular genotyping may provide markers to identify L. (V.) braziliensis strains likely to cause this emerging, hard-to-treat form of ATL.