Upregulation of surface proteins in Leishmania donovani isolated from patients of post kala-azar dermal leishmaniasis

The circulating plasma microRNA signature in human visceral leishmaniasis

Visceral leishmaniasis (VL) is a vector-borne disease caused by the obligate intracellular protozoan Leishmania donovani in India. VL can be complicated by post-kala-azar dermal leishmaniasis (PKDL), a macular or nodular rash that develops in 10%-20% of patients after treatment of VL in India. Patients with PKDL are infectious to sand flies, promoting further transmission of the parasite. MicroRNAs (miRNAs) are 18-25 nt, non-coding RNAs that simultaneously regulate the expression of several or many target transcripts. This study was based on the hypothesis that the host response to L. donovani is modified by distinct sets of miRNAs in VL or PKDL and that these might differ from healthy controls. We investigated this hypothesis using a NanoString panel to profile the miRNAs expressed in the plasma of patients with VL or PKDL diagnosed at a hospital in Bihar, India. We compared these to plasma microRNAs of healthy control individuals from the same endemic villages. miRNAs hsa-miR-223-3p, hsa-miR-191-5p, hsa-miR-23a-3p, and hsa-1285-5p were significantly higher in the plasma samples from patients with VL compared to either PKDL or endemic controls. Prediction programs highlighted potential mRNA targeted by these miRNAs, among which we verified the down-modulation of several transcripts belonging to the NFκB and NLRP3 inflammasome pathways in circulating leukocytes of VL patients. By contrast, miRNA patterns in subjects with PKDL were similar to control subjects, possibly suggesting that the pathogenic immune response during PKDL is primarily localized in the skin.IMPORTANCEInfection of humans with the protozoan Leishmania donovani can be asymptomatic or it can cause fatal visceral leishmaniasis (VL), sometimes followed by the cutaneous complication PKDL. Parasites are spread through sand fly bites in endemic regions, and parasites in post-kala-azar dermal leishmaniasis (PKDL) skin lesions are a source of prolonged parasite transmission to sand flies, compromising disease eradication efforts. Since microRNAs can simultaneously modify the expression of multiple genes, we examined microRNAs in the blood that might be partial determinants of pathogenic responses leading to VL or PKDL. Our studies revealed several miRNAs expressed that are elevated in the plasma of patients with VL, which suppress some of the inflammatory responses that promote parasite killing. However, miRNA profiles were very similar between PKDL patients and controls, raising the possibility that major factors that lead to prolonged retention of parasites in the skin during PKDL are not systemic but are localized in the skin.

Leishmania species: A narrative review on surface proteins with structural aspects involved in host-pathogen interaction

In tropical and subtropical regions of the world, leishmaniasis is endemic and causes a range of clinical symptoms in people, from severe tegumentary forms (such as cutaneous, mucocutaneous, and diffuse leishmaniasis) to lethal visceral forms. The protozoan parasite of the genus Leishmania causes leishmaniasis, which is still a significant public health issue, according to the World Health Organization 2022. The public's worry about the neglected tropical disease is growing as new foci of the illness arise, which are exacerbated by alterations in behavior, changes in the environment, and an enlarged range of sand fly vectors. Leishmania research has advanced significantly during the past three decades in a few different avenues. Despite several studies on Leishmania, many issues, such as illness control, parasite resistance, parasite clearance, etc., remain unresolved. The key virulence variables that play a role in the pathogenicity-host-pathogen relationship of the parasite are comprehensively discussed in this paper. The important Leishmania virulence factors, such as Kinetoplastid Membrane Protein-11 (KMP-11), Leishmanolysin (GP63), Proteophosphoglycan (PPG), Lipophosphoglycan (LPG), Glycosylinositol Phospholipids (GIPL), and others, have an impact on the pathophysiology of the disease and enable the parasite to spread the infection. Leishmania infection may arise from virulence factors; they are treatable with medications or vaccinations more promptly and might greatly shorten the duration of treatment. Additionally, our research sought to present a modeled structure of a few putative virulence factors that might aid in the development of new chemotherapeutic approaches for the treatment of leishmaniasis. The predicted virulence protein's structure is utilized to design novel drugs, therapeutic targets, and immunizations for considerable advantage from a higher understanding of the host immune response.

Tissue tropism: Is it an intrinsic characteristic of Leishmania species?

The genus Leishmania comprises a wide range of species, some of which are pathogenic to humans and each of which has a different tissue preference, resulting in one of the three clinical forms of human leishmaniasis: visceral, cutaneous, or mucocutaneous. Although, all pathogenic species are deposited intradermally in the mammalian host upon an infectious sand fly bite, only the viscerotropic strains can leave the skin and reach the internal organs. We assume that Leishmania tissue tropism is not only the result of Leishmania genetic determinism but is also governed by the interaction of the parasite with different vectorial and human host elements. To shed light on these elements and key steps determining the course of the infection, we describe throughout this review the disease's progression from the early stages of infection taking place in the skin to the late stages succeeding in the parasite's visceral dissemination. Hence, we address the question of Leishmania tropism, through providing relevant hypotheses and answers gathered from the literature.

An In-depth Proteomic Map of Leishmania donovani Isolate from Post Kala-azar Dermal Leishmaniasis (PKDL) Patient

BACKGROUND

The trypanosomatid protozoan parasite Leishmania donovani is the etiological agent of visceral leishmaniasis (VL) or kala-azar. The patients that have undergone treatment may still harbor the parasite and in a small fraction of the patients the disease re-erupts in the form of post kala-azar dermal leishmaniasis (PKDL). PKDL is a pathological condition found to be intermediate between VL and complete cure of VL. The PKDL disease progression is determined by the host immune response to L. donovani. The majority of the proteomic studies on L. donovani till date have been undertaken on parasites either isolated from kala-azar patients or on established laboratory strains of L. donovani. However, no proteomic information is available on the cutaneous localized isolates of L. donovani from PKDL patients.

METHODS

The promastigote stage of L. donovani isolate from PKDL patient was cultured and harvested. The cell lysates were trypsin digested, followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The LC-MS/MS raw data were analyzed on Proteome Discoverer. Further bioinformatics analysis was carried out.

RESULTS

In the present, we have used high-resolution mass spectrometry to map the global proteome of a L. donovani isolate from PKDL patient. This in-depth study resulted in the identification of 5537 unique proteins from PKDL isolate of L. donovani which covered 64% of its proteome.

OUTCOME

This study also identified proteins previously shown to be upregulated in PKDL L. donovani. This is the most in-depth proteome of Leishmania donovani parasite till date.

Precision Medicine in Control of Visceral Leishmaniasis Caused by L. donovani

Precision medicine and precision global health in visceral leishmaniasis (VL) have not yet been described and could take into account how all known determinants improve diagnostics and treatment for the individual patient. Precision public health would lead to the right intervention in each VL endemic population for control, based on relevant population-based data, vector exposures, reservoirs, socio-economic factors and other determinants. In anthroponotic VL caused by L. donovani, precision may currently be targeted to the regional level in nosogeographic entities that are defined by the interplay of the circulating parasite, the reservoir and the sand fly vector. From this 5 major priorities arise: diagnosis, treatment, PKDL, asymptomatic infection and transmission. These 5 priorities share the immune responses of infection with L. donovani as an important final common pathway, for which innovative new genomic and non-genomic tools in various disciplines have become available that provide new insights in clinical management and in control. From this, further precision may be defined for groups (e.g. children, women, pregnancy, HIV-VL co-infection), and eventually targeted to the individual level.

Proteomic Analysis of the Promastigote Secretome of Seven Leishmania Species

Leishmaniasis is one of the most impactful parasitic diseases worldwide, endangering the lives of 1 billion people every year. There are 20 different species of Leishmania able to infect humans, causing cutaneous (CL), visceral (VL), and/or mucocutaneous leishmaniasis (MCL). Leishmania parasites are known to secrete a plethora of proteins to establish infection and modulate the host's immune system. In this study, we analyzed using tandem mass spectrometry the total protein content of the secretomes produced by promastigote forms from seven Leishmania species grown in serum-free in vitro cultures. The core secretome shared by all seven Leishmania species corresponds to up to one-third of total secreted proteins, suggesting conserved mechanisms of adaptation to the vertebrate host. The relative abundance confirms the importance of known virulence factors and some proteins uniquely present in CL- or VL-causing species and may provide further insight regarding their pathogenesis. Bioinformatic analysis showed that most proteins were secreted via unconventional mechanisms, with an important role for vesicle-based secretion for all species. Gene Ontology annotation and enrichment analyses showed a high level of functional conservation among species. This study contributes to the current knowledge on the biological significance of differently secreted proteins and provides new information on the correlation of Leishmania secretome to clinical outcomes and species-specific pathogenesis.

The Diverse Calpain Family in Trypanosomatidae: Functional Proteins Devoid of Proteolytic Activity?

Calpains are calcium-dependent cysteine peptidases that were originally described in mammals and, thereafter, their homologues were identified in almost all known living organisms. The deregulated activity of these peptidases is associated with several pathologies and, consequently, huge efforts have been made to identify selective inhibitors. Trypanosomatids, responsible for life-threatening human diseases, possess a large and diverse family of calpain sequences in their genomes. Considering that the current therapy to treat trypanosomatid diseases is limited to a handful of drugs that suffer from unacceptable toxicity, tough administration routes, like parenteral, and increasing treatment failures, a repurposed approach with calpain inhibitors could be a shortcut to successful chemotherapy. However, there is a general lack of knowledge about calpain functions in these parasites and, currently, the proteolytic activity of these proteins is still an open question. Here, we highlight the current research and perspectives on trypanosomatid calpains, overview calpain description in these organisms, and explore the potential of targeting the calpain system as a therapeutic strategy. This review gathers the current knowledge about this fascinating family of peptidases as well as insights into the puzzle: are we unable to measure calpain activity in trypanosomatids, or are the functions of these proteins devoid of proteolytic activity in these parasites?

Epidemiology of Post-Kala-azar Dermal Leishmaniasis

Post-kala-azar dermal leishmaniasis (PKDL) is a cutaneous sequel of visceral leishmaniasis (VL) or kala-azar and has become an entity of epidemiological significance by virtue of its ability to maintain the disease in circulation during inter-epidemic periods. PKDL has been identified as one of the epidemiological marker of “kala-azar elimination programme.” Data obtained in 2018 showed PKDL distribution primarily concentrated in 6 countries, which includes India, Sudan, south Sudan, Bangladesh, Ethiopia, and Nepal in decreasing order of case-burden. In India, PKDL cases are mainly found in 54 districts, of which 33 are in Bihar, 11 in West Bengal, 4 in Jharkhand, and 6 in Uttar Pradesh. In West Bengal the districts reporting cases of PKDL cases include Darjeeling, Uttar Dinajpur, Dakshin Dinajpur, Malda, and Murshidabad. The vulnerability on the young age is documented in various studies. The studies also highlights a male predominance of the disease but recent active surveillance suggested that macular form of PKDL shows female-predominance. It is recommended that along with passive case detection, active survey helps in early identification of cases, thus reducing disease transmission in the community. The Accelerated plan for Kala-azar elimination in 2017 introduced by Government of India with the goal to eliminate Kala-azar as a public health problem, targets to reduceing annual incidence <1/10,000. Leishmania donovani is the established causative agent, but others like L. tropica or L. infantum may occasionally lead to the disease, especially with HIV-co-infection. Dermal tropism of the parasite has been attributed to overexpression of parasite surface receptors (like gp 63, gp46). Various host factors are also identified to contribute to the development of the disease, including high pretreatment IL 10 and parasite level, inadequate dose and duration of treatment, malnutrition, immuno-suppression, decreased interferon-gamma receptor 1 gene, etc. PKDL is mostly concentrated in the plains below an altitude of 600 mts which is attributed to the environment conducive for the vector sand fly (Phlebotumus). Risk factors are also linked to the habitat of the sand fly. Keeping these things in mind “Integrated vector control” is adopted under National vector borne disease control programme as one of the strategies to bring down the disease burden.

Conundrums in leishmaniasis

Parasites of the genus Leishmania cause the disease leishmaniasis. As the sandfly vector transfers the promastigotes into the skin of the human host, the infection is either cured or exacerbated. In the process, there emerge several unsolved paradoxes of leishmaniasis. Chronologically, as the infections starts in skin, the role of the salivary proteins in supporting the infection or the host response to these proteins influencing the induction of immunological memory becomes a conundrum. As the parasite invokes inflammation, the infiltrating neutrophils may act as "Trojan Horse" to transfer parasites to macrophages that, along with dendritic cells, carry the parasite to lymphoid organs to start visceralization. As the visceralized infection becomes chronic, the acutely enhanced monocytopoiesis takes a downturn while neutropenia and thrombocytopenia ensue with concomitant rise in splenic colony-forming-units. These responses are accompanied by splenic and hepatic granulomas, polyclonal activation of B cells and deviation of T cell responses. The granuloma formation is both a containment process and a form of immunopathogenesis. The heterogeneity in neutrophils and macrophages contribute to both cure and progression of the disease. The differentiation of T-helper subsets presents another paradox of visceral leishmaniasis, as the counteractive T cell subsets influence the curing or non-curing outcome. Once the parasites are killed by chemotherapy, in some patients the cured visceral disease recurs as a cutaneous manifestation post-kala azar dermal leishmaniasis (PKDL). As no experimental model exists, the natural history of PKDL remains almost a black box at the end of the visceral disease.

Post kala-azar dermal leishmaniasis: A threat to elimination program

Leishmaniasis remains a public health concern around the world that primarily affects poor folks of the developing world spanning across 98 countries with mortality of 0.2 million to 0.4 million annually. Post kala-azar dermal leishmaniasis (PKDL) is the late skin manifestation of visceral leishmaniasis (VL). It has been reported that about 2.5% to 20% of patients recovered from VL develop PKDL having stilted macular or nodular lesions with parasites. In the Indian subcontinent (ISC), it manifests a few months after recovery from VL, though in Africa it can occur simultaneously with VL or a little later. New cases of PKDL are also observed without prior VL in the ISC. These individuals with PKDL represent an important but largely neglected reservoir of infection that perpetuates anthroponotic Leishmania donovani transmission in the ISC and can jeopardize the VL elimination program as these cases can infect the sand flies and spread the endemic. Therefore, it becomes imperative to eradicate PKDL as a part of the VL elimination program. With the limited treatment options besides little knowledge on PKDL, this review stands out in focusing on different aspects that should be dealt for sustained VL elimination.

Report of the Fifth Post-Kala-Azar Dermal Leishmaniasis Consortium Meeting, Colombo, Sri Lanka, 14-16 May 2018

The 5th Post-Kala-Azar Dermal Leishmaniasis (PKDL) Consortium meeting brought together PKDL experts from all endemic areas to review and discuss existing and new data on PKDL. This report summarizes the presentations and discussions and provides the overall conclusions and recommendations.

Leishmania infantum amastin protein incorporated in distinct adjuvant systems induces protection against visceral leishmaniasis

The control measures against visceral leishmaniasis (VL) include a precise diagnosis of disease, the treatment of human cases, and reservoir and vector controls. However, these are insufficient to avoid the spread of the disease in specific countries worldwide. As a consequence, prophylactic vaccination could be interesting, although no effective candidate against human disease is available. In the present study, the Leishmania infantum amastin protein was evaluated regarding its immunogenicity and protective efficacy against experimental VL. BALB/c mice immunized with subcutaneous injections of the recombinant protein with or without liposome/saponin (Lip/Sap) as an adjuvant. After immunization, half of the animals per group were euthanized and immunological evaluations were performed, while the others were challenged with L. infantum promastigotes. Forty-five days after infection, the animals were euthanized and parasitological and immunological evaluations were performed. Results showed the development of a Th1-type immune response in rAmastin-Lip and rAmastin-Sap/vaccinated mice, before and after infection, which was based on the production of protein and parasite-specific IFN-γ, IL-12, GM-CSF, and nitrite, as well as the IgG2a isotype antibody. CD4⁺ T cells were mainly responsible for IFN-γ production in vaccinated mice, which also presented significant reductions in parasitism in their liver, spleen, draining lymph nodes, and bone marrow. In addition, PBMC cultures of treated VL patients and healthy subjects stimulated with rAmastin showed lymphoproliferation and higher IFN-γ production. In conclusion, the present study shows the first case of an L. infantum amastin protein associated with distinct delivery systems inducing protection against L. infantum infection and demonstrates an immunogenic effect of this protein in human cells.

Calpains of Leishmania braziliensis: genome analysis, differential expression, and functional analysis

BACKGROUND

Calpains are proteins belonging to the multi-gene family of calcium-dependent cysteine peptidases that undergo tight on/off regulation, and uncontrolled proteolysis of calpains is associated with severe human pathologies. Calpain orthologues are expanded and diversified in the trypanosomatids genome.

OBJECTIVES

Here, we characterised calpains in Leishmania braziliensis, the main causative agent of cutaneous leishmaniasis in Brazil.

METHODS/FINDINGS

In total, 34 predicted calpain-like genes were identified. After domain structure evaluation, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) during in vitro metacyclogenesis revealed (i) five genes with enhanced expression in the procyclic stage, (ii) one augmented gene in the metacyclic stage, and (iii) one procyclic-exclusive transcript. Western blot analysis revealed that an antibody against a consensus-conserved peptide reacted with multiple calpain-like proteins, which is consistent with the multi-gene family characteristic. Flow cytometry and immunocytochemistry analyses revealed the presence of calpain-like molecules mainly in the cytoplasm, to a lesser extent in the plasma membrane, and negligible levels in the nucleus, which are all consistent with calpain localisation. Eventually, the calpain inhibitor MDL28170 was used for functional studies revealing (i) a leishmaniostatic effect, (ii) a reduction in the association index in mouse macrophages, (iii) ultra-structural alterations conceivable with autophagy, and (iv) an enhanced expression of the virulence factor GP63.

CONCLUSION

This report adds novel insights into the domain structure, expression, and localisation of L. braziliensis calpain-like molecules.

Ribosome Profiling Reveals HSP90 Inhibitor Effects on Stage-Specific Protein Synthesis in Leishmania donovani

Leishmania parasites cause severe illness in humans and animals. They exist in two developmental stages, insect form and mammalian form, which differ in shape and gene expression. By mapping and quantifying RNA fragments protected by protein synthesis complexes, we determined the rates of protein synthesis for >90% of all Leishmania proteins in response to the inhibition of a key regulatory protein, the 90-kDa heat shock protein. We find that Leishmania depends on a regulation of protein synthesis for controlling its gene expression and that heat shock protein 90 inhibition can trigger the developmental program from insect form to mammalian form of the pathogen.

The 90-kDa heat shock protein (HSP90) of eukaryotes is a highly abundant and essential chaperone required for the maturation of regulatory and signal proteins. In the protozoan parasite Leishmania donovani, causative agent of the fatal visceral leishmaniasis, HSP90 activity is essential for cell proliferation and survival. Even more importantly, its inhibition causes life cycle progression from the insect stage to the pathogenic, mammalian stage. To unravel the molecular impact of HSP90 activity on the parasites’ gene expression, we performed a ribosome profiling analysis of L. donovani, comparing genome-wide protein synthesis patterns in the presence and absence of the HSP90-specific inhibitor radicicol and an ectopically expressed radicicol-resistant HSP90 variant. We find that ribosome-protected RNA faithfully maps open reading frames and represents 97% of the annotated protein-coding genes of L. donovani. Protein synthesis was found to correlate poorly with RNA steady-state levels, indicating a regulated translation as primary mechanism for HSP90-dependent gene expression. The results confirm inhibitory effects of HSP90 on the synthesis of Leishmania proteins that are associated with the pathogenic, intracellular stage of the parasite. Those include heat shock proteins, redox enzymes, virulence-enhancing surface proteins, proteolytic pathways, and a complete set of histones. Conversely, HSP90 promotes fatty acid synthesis enzymes. Complementing radicicol treatment with the radicicol-resistant HSP90rr variant revealed important off-target radicicol effects that control a large number of the above-listed proteins. Leishmania lacks gene-specific transcription regulation and relies on regulated translation instead. Our ribosome footprinting analysis demonstrates a controlling function of HSP90 in stage-specific protein synthesis but also significant, HSP90-independent effects of the inhibitor radicicol.

IMPORTANCELeishmania parasites cause severe illness in humans and animals. They exist in two developmental stages, insect form and mammalian form, which differ in shape and gene expression. By mapping and quantifying RNA fragments protected by protein synthesis complexes, we determined the rates of protein synthesis for >90% of all Leishmania proteins in response to the inhibition of a key regulatory protein, the 90-kDa heat shock protein. We find that Leishmania depends on a regulation of protein synthesis for controlling its gene expression and that heat shock protein 90 inhibition can trigger the developmental program from insect form to mammalian form of the pathogen.

The contribution of DNA microarray technology to gene expression profiling in Leishmania spp.: A retrospective view

The first completed genome project of any living organism, excluding viruses, was of the gammaproteobacteria Haemophilus influenzae in 1995. Until the last decade, genome sequencing was very tedious because genome survey sequences (GSS) and/or expressed sequence tags (ESTs) belonging to plasmid, cosmid, and artificial chromosome genome libraries had to be sequenced and assembled in silico. No genome is completely assembled because gaps and unassembled contigs are always remaining. However, most represent an organism's whole genome from a practical point of view. The first genome sequencing projects of trypanosomatid parasites Leishmania major, Trypanosoma cruzi, and T. brucei were completed in 2005 following those strategies. The functional genomics era developed on the basis of microarray technology and has been continuously evolving. In the case of the genus Leishmania, substantial information about differentiation in the digenetic life cycle of the parasite has been obtained. More recently, next generation sequencing has revolutionized genome sequencing and functional genomics, leading to more sensitive and accurate results by using much fewer resources. Though this new technology is more advantageous, it does not invalidate microarray results. In fact, promising vaccine candidates and drug targets have been found by means of microarray-based screening and preliminary proof-of-concept tests.

Genomic comparison of Trypanosoma conorhini and Trypanosoma rangeli to Trypanosoma cruzi strains of high and low virulence

Background

Trypanosoma conorhini and Trypanosoma rangeli, like Trypanosoma cruzi, are kinetoplastid protist parasites of mammals displaying divergent hosts, geographic ranges and lifestyles. Largely nonpathogenic T. rangeli and T. conorhini represent clades that are phylogenetically closely related to the T. cruzi and T. cruzi-like taxa and provide insights into the evolution of pathogenicity in those parasites. T. rangeli, like T. cruzi is endemic in many Latin American countries, whereas T. conorhini is tropicopolitan. T. rangeli and T. conorhini are exclusively extracellular, while T. cruzi has an intracellular stage in the mammalian host.

Results

Here we provide the first comprehensive sequence analysis of T. rangeli AM80 and T. conorhini 025E, and provide a comparison of their genomes to those of T. cruzi G and T. cruzi CL, respectively members of T. cruzi lineages TcI and TcVI. We report de novo assembled genome sequences of the low-virulent T. cruzi G, T. rangeli AM80, and T. conorhini 025E ranging from ~ 21–25 Mbp, with ~ 10,000 to 13,000 genes, and for the highly virulent and hybrid T. cruzi CL we present a ~ 65 Mbp in-house assembled haplotyped genome with ~ 12,500 genes per haplotype. Single copy orthologs of the two T. cruzi strains exhibited ~ 97% amino acid identity, and ~ 78% identity to proteins of T. rangeli or T. conorhini. Proteins of the latter two organisms exhibited ~ 84% identity. T. cruzi CL exhibited the highest heterozygosity. T. rangeli and T. conorhini displayed greater metabolic capabilities for utilization of complex carbohydrates, and contained fewer retrotransposons and multigene family copies, i.e. trans-sialidases, mucins, DGF-1, and MASP, compared to T. cruzi.

Conclusions

Our analyses of the T. rangeli and T. conorhini genomes closely reflected their phylogenetic proximity to the T. cruzi clade, and were largely consistent with their divergent life cycles. Our results provide a greater context for understanding the life cycles, host range expansion, immunity evasion, and pathogenesis of these trypanosomatids.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5112-0) contains supplementary material, which is available to authorized users.

Analysis of genetic polymorphisms and tropism in East African Leishmania donovani by Amplified Fragment Length Polymorphism and kDNA minicircle sequencing

Visceral leishmaniasis (VL), the most severe form of leishmaniasis, is caused by Leishmania donovani. In addition to fatal VL, these parasites also cause skin diseases in immune-competent and -suppressed people, post-kala azar dermal leishmaniasis (PKDL) and HIV/VL co-infections, respectively. Genetic polymorphism in 36 Ethiopian and Sudanese L. donovani strains from VL, PKDL and HIV/VL patients was examined using Amplified Fragment Length Polymorphism (AFLP), kDNA minicircle sequencing and Southern blotting. Strains were isolated from different patient tissues: in VL from lymph node, spleen or bone marrow; and in HIV/VL from skin, spleen or bone marrow. When VL and PKDL strains from the same region in Sudan were examined by Southern blotting using a DNA probe to the L. donovani 28S rRNA gene only minor differences were observed. kDNA sequence analysis distributed the strains in no particular order among four clusters (A - D), while AFLP analysis grouped the strains according to geographical origin into two major clades, Southern Ethiopia (SE) and Sudan/Northern Ethiopia (SD/NE). Strains in the latter clade were further divided into subpopulations by zymodeme, geography and year of isolation, but not by clinical symptoms. However, skin isolates showed significantly (p < 0.0001) fewer polymorphic AFLP fragments (average 10 strains = 348.6 ± 8.1) than VL strains (average 26 strains = 383.5 ± 3.8).

Why calpain inhibitors are interesting leading compounds to search for new therapeutic options to treat leishmaniasis?

Leishmaniasis is a neglected disease, which needs improvements in drug development, mainly due to the toxicity, parasite resistance and low compliance of patients to treatment. Therefore, the development of new chemotherapeutic compounds is an urgent need. This opinion article will briefly highlight the feasible use of calpain inhibitors as leading compounds to search for new therapeutic options to treat leishmaniasis. The milestone of this approach is to take advantage on the myriad of inhibitors developed against calpains, some of which are in advanced clinical trials. The deregulated activity of these enzymes is associated with several pathologies, such as strokes, diabetes and Parkinson's disease, to name a few. In Leishmania, calpain upregulation has been associated to drug resistance and virulence. Whereas the difficulties in developing new drugs for neglected diseases are more economical than biotechnological, repurposing approach with compounds already approved for clinical use by the regulatory agencies can be an interesting shortcut to a successful chemotherapeutic treatment for leishmaniasis.

Chronic Arsenic Exposure and Risk of Post Kala-azar Dermal Leishmaniasis Development in India: A Retrospective Cohort Study

Background

Visceral leishmaniasis (VL), with the squeal of Post-kala-azar dermal leishmaniasis (PKDL), is a global threat for health. Studies have shown sodium stibogluconate (SSG) resistance in VL patients with chronic arsenic exposure. Here, we assessed the association between arsenic exposure and risk of developing PKDL in treated VL patients.

Methods

In this retrospective study, PKDL patients (n = 139), earlier treated with SSG or any other drug during VL, were selected from the study cohort. Trained physicians, unaware of arsenic exposure, interviewed them and collected relevant data in a questionnaire format. All probable water sources were identified around the patient’s house and water was collected for evaluation of arsenic concentration. A GIS-based village-level digital database of PKDL cases and arsenic concentration in groundwater was developed and individual point location of PKDL cases were overlaid on an integrated GIS map. We used multivariate logistic regression analysis to assess odds ratios (ORs) for association between arsenic exposure and PKDL development.

Results

Out of the 429 water samples tested, 403 had arsenic content of over 10 μg/L, with highest level of 432 μg/L among the seven study villages. Multivariate adjusted ORs for risk of PKDL development in comparison of arsenic concentrations of 10.1–200 μg/L and 200.1–432.0 μg/L were 1.85 (1.13–3.03) and 2.31 (1.39–3.8) respectively. Interestingly, similar results were found for daily dose of arsenic and total arsenic concentration in urine sample of the individual. The multivariate-adjusted OR for comparison of high baseline arsenic exposure to low baseline arsenic exposure of the individuals in the study cohort was 1.66 (95% CI 1.02–2.7; p = 0.04).

Conclusion

Our findings indicate the need to consider environmental factors, like long time arsenic exposure, as an additional influence on treated VL patients towards risk of PKDL development in Bihar.

Post-kala-azar dermal leishmaniasis (PKDL) is a sequela of visceral leishmaniasis (VL) that appears after patients have apparently been cured of visceral leishmaniasis; even been reported in patients without a history of VL. Previous clinical and epidemiological data ascertains the main risk factor associated with the development of PKDL is previous treatment for VL with antimonials (SSG); however, PKDL also occurs after treatment with other drugs like paromomycin, miltefosine etc. Here, in light of the risk of arsenic-associated dermal manifestations, we hypothesized that the long term exposure to groundwater arsenic acts as an additional risk factor for development of PKDL in patients treated for VL with SSG or other drugs. Using a cohort, we retrospectively assessed the risk of arsenic in development of PKDL in treated VL patients. Our findings support a significant association and prompts parasites might persist successfully in individuals over-exposed to arsenic and may exhibit features of dermatotropism leading to development of PKDL after treatment for VL. Further research is needed to dissect the mechanistic role of arsenic on VL, as well as PKDL development.

Advances in Development of New Treatment for Leishmaniasis

Leishmaniasis is a neglected infectious disease caused by several different species of protozoan parasites of the genus Leishmania. Current strategies to control this disease are mainly based on chemotherapy. Despite being available for the last 70 years, leishmanial chemotherapy has lack of efficiency, since its route of administration is difficult and it can cause serious side effects, which results in the emergence of resistant cases. The medical-scientific community is facing difficulties to overcome these problems with new suitable and efficient drugs, as well as the identification of new drug targets. The availability of the complete genome sequence of Leishmania has given the scientific community the possibility of large-scale analysis, which may lead to better understanding of parasite biology and consequent identification of novel drug targets. In this review we focus on how high-throughput analysis is helping us and other groups to identify novel targets for chemotherapeutic interventions. We further discuss recent data produced by our group regarding the use of the high-throughput techniques and how this helped us to identify and assess the potential of new identified targets.

The immunological, environmental, and phylogenetic perpetrators of metastatic leishmaniasis

Cutaneous leishmaniases have persisted for centuries as chronically disfiguring parasitic infections affecting millions of people across the subtropics. Symptoms range from the more prevalent single, self-healing cutaneous lesion to a persistent, metastatic disease, where ulcerations and granulomatous nodules can affect multiple secondary sites of the skin and delicate facial mucosa, even sometimes diffusing throughout the cutaneous system as a papular rash. The basis for such diverse pathologies is multifactorial, ranging from parasite phylogeny to host immunocompetence and various environmental factors. Although complex, these pathologies often prey on weaknesses in the innate immune system and its pattern recognition receptors. This review explores the observed and potential associations among the multifactorial perpetrators of infectious metastasis and components of the innate immune system.

Post kala-azar dermal leishmaniasis: an unresolved mystery

•

Sodium antimony gluconate contributes towards the pathogenesis of PKDL.

•

UV light plays a pivotal role in the development of PKDL.

•

Development of PKDL can be viewed as a reinfection or activation of latent Leishmania parasites.

•

PKDL can be resolved by mounting an effective tissue-specific memory T cell response.

•

Host genetic factors play a contributory role.

Post kala-azar dermal leishmaniasis (PKDL), a cutaneous sequela of visceral leishmaniasis (VL), develops in some patients alongside but more commonly after apparent cure from VL. In view of the pivotal role of PKDL patients in the transmission of VL, here we review clinical, epidemiological, parasitological, and immunological perspectives of this disease, focusing on five hypotheses to explain the development of PKDL: (i) the role of antimonial drugs; (ii) UV-induced skin damage; (iii) reinfection; (iv) organ specific failure of memory T cell responses; and (v) genetic susceptibility of the host. This review will enable researchers and clinicians to explore the unresolved mystery of PKDL and provide a framework for future application of ‘omic’ approaches for the control and eventual elimination of VL.

The genome sequence of Leishmania (Leishmania) amazonensis: functional annotation and extended analysis of gene models

We present the sequencing and annotation of the Leishmania (Leishmania) amazonensis genome, an etiological agent of human cutaneous leishmaniasis in the Amazon region of Brazil. L. (L.) amazonensis shares features with Leishmania (L.) mexicana but also exhibits unique characteristics regarding geographical distribution and clinical manifestations of cutaneous lesions (e.g. borderline disseminated cutaneous leishmaniasis). Predicted genes were scored for orthologous gene families and conserved domains in comparison with other human pathogenic Leishmania spp. Carboxypeptidase, aminotransferase, and 3′-nucleotidase genes and ATPase, thioredoxin, and chaperone-related domains were represented more abundantly in L. (L.) amazonensis and L. (L.) mexicana species. Phylogenetic analysis revealed that these two species share groups of amastin surface proteins unique to the genus that could be related to specific features of disease outcomes and host cell interactions. Additionally, we describe a hypothetical hybrid interactome of potentially secreted L. (L.) amazonensis proteins and host proteins under the assumption that parasite factors mimic their mammalian counterparts. The model predicts an interaction between an L. (L.) amazonensis heat-shock protein and mammalian Toll-like receptor 9, which is implicated in important immune responses such as cytokine and nitric oxide production. The analysis presented here represents valuable information for future studies of leishmaniasis pathogenicity and treatment.

Calpains: potential targets for alternative chemotherapeutic intervention against human pathogenic trypanosomatids

The treatment for both leishmaniasis and trypanosomiasis, which are severe human infections caused by trypanosomatids belonging to Leishmania and Trypanosoma genera, respectively, is extremely limited because of concerns of toxicity and efficacy with the available anti-protozoan drugs, as well as the emergence of drug resistance. Consequently, the urgency for the discovery of new trypanosomatid targets and novel bioactive compounds is particularly necessary. In this context, the investigation of changes in parasite gene expression between drug resistant/sensitive strains and in the up-regulation of virulence-related genes in infective forms has brought to the fore the involvement of calpain-like proteins in several crucial pathophysiological processes performed by trypanosomatids. These studies were encouraged by the publication of the complete genome sequences of three human pathogenic trypanosomatids, Trypanosoma brucei, Trypanosoma cruzi and Leishmania major, which allowed in silico analyses that in turn directed the identification of numerous genes with interesting chemotherapeutic characteristics, including a large family of calpain-related proteins, in which to date 23 genes were assigned as calpains in T. brucei, 40 in T. cruzi and 33 in L. braziliensis. In the present review, we intend to add to these biochemical/biological reports the investigations performed upon the inhibitory capability of calpain inhibitors against human pathogenic trypanosomatids.

Trypanosoma cruzi: role of δ-amastin on extracellular amastigote cell invasion and differentiation

Trypanosoma cruzi is a protozoan parasite that comprises different phylogenetic groups and is the causative agent of Chagas’ disease. Different T. cruzi strains present differences in infectivity in in vitro and in vivo experimental models, which are likely related to the expression of different virulence factors. Amastin is a surface glycoprotein abundantly expressed on the intracellular mammalian amastigote form of the parasite. In this study, we showed that a highly infective strain (G strain) of extracellular amastigote (EA) invasive forms expressed reduced RNA levels of amastin compared to a less infective strain (CL). The treatment of HeLa cells with recombinant δ-amastin reduced infectivity of EA forms. However, the ectopic expression of δ-amastin accelerated amastigote differentiation into trypomastigotes. Corroborating the virulence behavior in association with amastin expression, the EAs overexpressing amastin were precociously and robustly observed in the liver of susceptible mouse strains (A/JUnib), whereas parasitemia was never detected in in vivo assays. This is the first report on the regulatory role of amastin in the course of both in vitro and in vivo T. cruzi infection.

Genome-wide SNP and microsatellite variation illuminate population-level epidemiology in the Leishmania donovani species complex

The species of the Leishmania donovani species complex cause visceral leishmaniasis, a debilitating infectious disease transmitted by sandflies. Understanding molecular changes associated with population structure in these parasites can help unravel their epidemiology and spread in humans. In this study, we used a panel of standard microsatellite loci and genome-wide SNPs to investigate population-level diversity in L. donovani strains recently isolated from a small geographic area spanning India, Bihar and Nepal, and compared their variation to that found in diverse strains of the L. donovani complex isolates from Europe, Africa and Asia. Microsatellites and SNPs could clearly resolve the phylogenetic relationships of the strains between continents, and microsatellite phylogenies indicated that certain older Indian strains were closely related to African strains. In the context of the anti-malaria spraying campaigns in the 1960s, this was consistent with a pattern of episodic population size contractions and clonal expansions in these parasites that was supported by population history simulations. In sharp contrast to the low resolution provided by microsatellites, SNPs retained a much more fine-scale resolution of population-level variability to the extent that they identified four different lineages from the same region one of which was more closely related to African and European strains than to Indian or Nepalese ones. Joining results of in vitro testing the antimonial drug sensitivity with the phylogenetic signals from the SNP data highlighted protein-level mutations revealing a distinct drug-resistant group of Nepalese and Indian L. donovani. This study demonstrates the power of genomic data for exploring parasite population structure. Furthermore, markers defining different genetic groups have been discovered that could potentially be applied to investigate drug resistance in clinical Leishmania strains.

Post-kala-azar dermal leishmaniasis: recent developments

A substantial number of patients who recover from kala-azar will develop dermatosis [commonly known as post-kala-azar dermal leishmaniasis (PKDL)]. It usually occurs in the Indian subcontinent and East Africa. As many as 10-20% of Indian cases and 50-60% of Sudanese cases develop PKDL after successful treatment of visceral leishmaniasis. Most cases occur after infection with Leishmania donovani and less commonly after Leishmania infantum. However, the PKDL is extremely rare in patients infected with Leishmania chagasi. Though exact pathology is not yet fully known, here we review various evidence, which suggest that the pathogenesis is largely immunologically mediated. Our group has been of the opinion that PKDL disease manifestation is a result of in-vivo generation of quasi-species either as in-vivo hybridization of various circulating and latent populations of the causative species within the host cells or due to external reinfection. We, and other scientists, have recently demonstrated that strains of Leishmania that cause visceral diseases differ genetically from those that cause PKDL. We feel that this review will incite interest in several parasitologists and molecular biologists in the pathogenesis of this important manifestation of the infection, often blamed as the source of outbreaks of leishmaniasis.

The potential of metabolomics for Leishmania research in the post-genomics era

The post-genomics era has provided researchers with access to a new generation of tools for the global characterization and understanding of pathogen diversity. This review provides a critical summary of published Leishmania post-genomic research efforts to date, and discusses the potential impact of the addition of metabolomics to the post-genomic toolbox. Metabolomics aims at understanding biology by comprehensive metabolite profiling. We present an overview of the design and interpretation of metabolomics experiments in the context of Leishmania research. Sample preparation, measurement techniques, and bioinformatics analysis of the generated complex datasets are discussed in detail. To illustrate the concepts and the expected results of metabolomics analyses, we also present an overview of comparative metabolic profiles of drug-sensitive and drug-resistant Leishmania donovani clinical isolates.

Comparative expression profiling of Leishmania: modulation in gene expression between species and in different host genetic backgrounds

BACKGROUND

Genome sequencing of Leishmania species that give rise to a range of disease phenotypes in the host has revealed highly conserved gene content and synteny across the genus. Only a small number of genes are differentially distributed between the three species sequenced to date, L. major, L. infantum and L. braziliensis. It is not yet known how many of these genes are expressed in the disease-promoting intracellular amastigotes of these species or whether genes conserved between the species are differentially expressed in the host.

METHODS/PRINCIPAL FINDINGS

We have used customised oligonucleotide microarrays to confirm that all of the differentially distributed genes identified by genome comparisons are expressed in intracellular amastigotes, with only a few of these subject to regulation at the RNA level. In the first large-scale study of gene expression in L. braziliensis, we show that only approximately 9% of the genes analysed are regulated in their RNA expression during the L. braziliensis life cycle, a figure consistent with that observed in other Leishmania species. Comparing amastigote gene expression profiles between species confirms the proposal that Leishmania transcriptomes undergo little regulation but also identifies conserved genes that are regulated differently between species in the host. We have also investigated whether host immune competence influences parasite gene expression, by comparing RNA expression profiles in L. major amastigotes derived from either wild-type (BALB/c) or immunologically compromised (Rag2(-/-) gamma(c) (-/-)) mice. While parasite dissemination from the site of infection is enhanced in the Rag2(-/-) gamma(c) (-/-) genetic background, parasite RNA expression profiles are unperturbed.

CONCLUSION/SIGNIFICANCE

These findings support the hypothesis that Leishmania amastigotes are pre-adapted for intracellular survival and undergo little dynamic modulation of gene expression at the RNA level. Species-specific parasite factors contributing to virulence and pathogenicity in the host may be limited to the products of a small number of differentially distributed genes or the differential regulation of conserved genes, either of which are subject to translational and/or post-translational controls.

Searching for virulence factors in the non-pathogenic parasite to humans Leishmania tarentolae

Leishmania protozoa are obligate intracellular parasites that reside in the phagolysosome of host macrophages and cause a large spectrum of pathologies to humans known as leishmaniases. The outcome of the disease is highly dependent on the parasite species and on its ascribed virulence factors and the immune status of the host. Characterization of the genome composition of non-pathogenic species could ultimately open new horizons in Leishmania developmental biology and also the disease monitoring. Here, we provide evidence that the lizard non-pathogenic to humans Leishmania tarentolae species expresses an Amastin-like gene, cysteine protease B (CPB), lipophosphoglycan LPG3 and the leishmanolysin GP63, genes well-known for their potential role in the parasite virulence. These genes were expressed at levels comparable to those in L. major and L. infantum both at the level of mRNA and protein. Alignment of the L. tarentolae proteins with their counterparts in the pathogenic species demonstrated that the degree of similarity varied from 59% and 60% for Amastin, 89% for LPG3 and 71% and 68% for CPB, in L. major and L. infantum, respectively. Interestingly, the A2 gene, expressed specifically by the L. donovani complex which promotes visceralization, was absent in L. tarentolae. These findings suggest that the lack of pathogenicity in L. tarentolae is not associated with known virulence genes such as LPG3, CPB, GP63 and Amastin, and that other factors either unique to L. tarentolae or missing from this species may be responsible for the non-pathogenic potential of this lizard parasite.

Evidence for involvement of TNFR1 and TIMPs in pathogenesis of post-kala-azar dermal leishmaniasis

Semi-quantitative RT-PCR was exploited to analyse the intralesional cytokine gene expression in 14 post-kala-azar dermal leishmaniasis (PKDL) and 10 kala-azar (KA) patients. The data provided evidence for both inflammatory and non-inflammatory responses, as reflected by elevated tumour necrosis factor (TNF)-alpha and interleukin (IL)-10 in PKDL lesions compared with normal skin tissue (n = 6). The ratio of TNF-alpha : IL-10 message was 2.66 in PKDL cases, substantially higher than in KA (1.18). Investigation of TNF-alpha receptors (TNFR1 and TNFR2) revealed a significant down-regulation of TNFR1 transcript in both PKDL and KA compared with control. In the presence of elevated levels of TNF-alpha transcript, interference with type 1 effector activity in PKDL may be due to minimal expression of the TNFR1 gene. Investigation of matrix metalloproteinases, known to be induced by TNF-alpha, and the tissue inhibitors of matrix metalloproteinases (TIMPs), provided evidence for the roles of TIMP-1 and TIMP-3 in the pathogenesis of PKDL.

Arrested growth of Trypanosoma cruzi by the calpain inhibitor MDL28170 and detection of calpain homologues in epimastigote forms

In this paper, we aimed to explore the effects of the calpain inhibitor III (MDL28170) and to detect calpain-like molecules (CALPs) in epimastigote forms of Trypanosoma cruzi isolate Dm28c. MDL28170 at 70 μM promoted a powerful reduction in the growth rate after 48 h. The IC50 value was calculated to be 31·7 μM. This inhibitor promoted an increase in the cellular volume, but not cell lysis, resulting in a trypanostatic effect. T. cruzi CALPs presented a strong cross-reactivity with anti-Drosophila melanogaster calpain and anti-cytoskeleton-associated protein from Trypanosoma brucei antibodies, and labelling was found mainly intracellularly. Furthermore, an 80 kDa reactive protein was detected by Western blotting assays. No significant cross-reactivity was found with anti-human brain calpain antibody. The expression of CALPs was decreased in cells kept for long periods in axenic cultures in comparison to a strain recently isolated from mice, as well as in MDL28170-treated cells, the latter being paralleled by an increased expression of cruzipain. Different levels of CALPs expression were also detected in distinct phylogenetic lineages, like Y strain (lineage TCI), Dm28c (TCII) and INPA6147 strain (Z3 zymodeme). These results may contribute for the investigation of the functions of CALPs in trypanosomatids.

Kinetoplastid genomics: the thin end of the wedge

The completion of the genome sequencing projects for major pathogens Trypanosoma brucei, Trypanosoma cruzi and Leishmania major has enabled numerous studies that would have been difficult or impossible to perform otherwise. New technologies in sequencing and protein analyses promise further rapid expansion in our capabilities. The keys to successful use of these new tools are recognizing the power and limitations of studies performed thus far, grasping the unrealized potential of new and developing technologies, and creating access to a multidisciplinary set of skills that will facilitate research, particularly in the bioinformatic analysis of the reams of data that will be forthcoming. In this Discussion, we will provide an overview of kinetoplastid genomics studies with emphasis on studies advanced through genomic data, and a preview of what may come in the near future.

Recent developments leading toward a paradigm switch in the diagnostic and therapeutic approach to human leishmaniasis

PURPOSE OF REVIEW

To identify recent papers showing how human and parasite genetics influence leishmaniasis, and how understanding of the immunopathology may be utilized in immunotherapy for these diseases.

RECENT FINDINGS

Progress has been made in recent years showing the complexity within populations of Leishmania spp. and indicating that different strains lead to diverse clinical pictures and responses to treatment. Thus detection of parasite genetic tags for the precise identification of infecting strains, and for predictive diagnosis of clinical and therapeutic fates seems now possible. Host genetic loci involved in disease outcome have been detected, which may also be explored for better case management. These developments in diagnosis will demand expanding the therapeutic arsenal to take their expected effect. This is starting to be fulfilled by immunotherapies successfully employed to treat cases refractory to standard first line drugs, as the result of a more profound comprehension of the immunopathology of the leishmaniases.

SUMMARY

The knowledge mounting has already helped explain why different patients present different forms of leishmaniasis and respond differently to treatment, and may be on the verge of catalyzing a major change in the already over a century old paradigm of diagnosing and managing these patients.

Leishmania and the leishmaniases: a parasite genetic update and advances in taxonomy, epidemiology and pathogenicity in humans

Leishmaniases remain a major public health problem today despite the vast amount of research conducted on Leishmania pathogens. The biological model is genetically and ecologically complex. This paper explores the advances in Leishmania genetics and reviews population structure, taxonomy, epidemiology and pathogenicity. Current knowledge of Leishmania genetics is placed in the context of natural populations. Various studies have described a clonal structure for Leishmania but recombination, pseudo-recombination and other genetic processes have also been reported. The impact of these different models on epidemiology and the medical aspects of leishmaniases is considered from an evolutionary point of view. The role of these parasites in the expression of pathogenicity in humans is also explored. It is important to ascertain whether genetic variability of the parasites is related to the different clinical expressions of leishmaniasis. The review aims to put current knowledge of Leishmania and the leishmaniases in perspective and to underline priority questions which 'leishmaniacs' must answer in various domains: epidemiology, population genetics, taxonomy and pathogenicity. It concludes by presenting a number of feasible ways of responding to these questions.

Genetic fingerprinting and identification of differentially expressed genes in isolates of Leishmania donovani from Indian patients of post-kala-azar dermal leishmaniasis

Post-kala-azar dermal leishmaniasis (PKDL) is an unusual dermatosis that develops as a sequel in 5-15% of cured cases of kala-azar (KA) after months or years of treatment in India. Molecular differences are reported to exist between the KA and PKDL isolates which may underlie the diversity in clinical manifestations of the disease. Here, arbitrary primed-PCR (AP-PCR) has been used for genetic fingerprinting of parasite isolates from dermal lesions of PKDL patients (n=14) and compared with bone-marrow derived parasites from KA patients (n=3). All isolates showed an identical AP-PCR pattern with 4 arbitrary primers. Further, AP-PCR was exploited to identify the stage regulated genes of the parasite. Six polymorphic fragments were identified in PKDL in comparison with KA isolates, and were subjected to Northern blot analysis. Five polymorphic fragments represented transcribed sequences; 4 out of 5 drew differential expression in pro- and amastigote stages, although the expression was comparable between PKDL and KA isolates. The study led to the identification of genes, which exhibit stage-regulated expression in Leishmania donovani derived from PKDL or KA patients, including a putative phosphodiesterase, DEAD box RNA helicase, iron superoxide dismutase b (fesodb) and a hypothetical protein. Demonstration of transcripts of DEAD box RNA helicase in PKDL and KA diseased tissues implicates its role in disease pathogenesis.

Proteome analysis of Leishmania (Viannia) braziliensis by two-dimensional gel electrophoresis and mass spectrometry

Leishmania (Viannia) braziliensis, a protozoan parasite widespread in the New World, is responsible for the infection of different mammal orders, including humans. This species is considered to be a major etiological agent of American cutaneous leishmaniasis. A proteomic study was carried out to identify proteins expressed by L. (V.) braziliensis. One hundred and one spots representing 75 protein entries were identified by MALDI-TOF-TOF. Isoelectric point values estimated by gel electrophoresis matched closely with predicted values, although some discrepancies existed suggesting that post-translational protein modifications may be common in L. braziliensis. Moreover, 20 hypothetical proteins were experimentally identified. Identified proteins were classified into 15 groups according to biological process. Among the proteins identified, approximately 40% have not been previously reported in a proteomic map of Leishmania. In addition, a number of potential virulence factors and drug targets were identified in this protein map, including some proteins associated with the metastatic phenotype. This study describes the first compilation of a proteomic reference map for L. braziliensis (pI 4-7, M(r) 10-130 kDa) and provides a very useful tool for comparative studies of strains isolated from patients presenting different clinical manifestations of leishmaniasis as well as a potential tool to identify markers for clinical diagnosis, therapeutics, and prognosis.

Short communication: Post-kala-azar dermal leishmaniasis - an appraisal

This short descriptive paper assesses diagnostics, clinical characteristics and therapy of both Indian and African post-kala-azar dermal leishmaniasis.

Transcriptome analysis during the process ofin vitrodifferentiation ofLeishmania donovaniusing genomic microarrays

Leishmania donovanicauses visceral disease (kala-azar), a major health problem throughout the tropics with 500 000 new cases every year.Leishmaniadifferentiates from the promastigote to the amastigote form to establish infection in a mammalian host. To understand the process of differentiation, we assessed the global variation in gene expression in promastigotes, an intermediate stage of differentiation (PA24) and axenic amastigotes in culture using anL. donovanigenomic microarray with 4224 clones printed in triplicate. During an intermediate stage of differentiation 24 h after shifting the promastigotes into amastigotes (PA24), there were 41 (∼1%) clones with expression ⩾2·0-fold higher than promastigotes, whereas in terminally differentiated amastigotes there were 130 (∼3%) such clones. Of particular interest were certain genes that exhibited a transient increase or decrease in expression at the PA24 stage. Kinases showed a transient increase, and surface molecules, PSA and amino acid permease, were prominent clones among those showing a brief decrease at the PA24 stage. The microarray results have been validated using Northern blots or RT-PCR. In summary, our results provide important clues about the genes involved in the differentiation process ofL. donovanithat may contribute to virulence.

Amastin peptide-binding antibodies as biomarkers of active human visceral leishmaniasis

Amastin surface proteins belong to a large family of developmentally regulated proteins comprising up to 45 members that have recently been discovered in the genus Leishmania and are highly similar to the amastin proteins in Trypanosoma cruzi. All members of the amastin gene family contain a highly conserved 11-amino-acid (aa) signature at the N terminus, which is unique to the amastin proteins and to the Trypanosomatidae family. Recent studies have demonstrated that this region is highly protective in a mouse model. The goal of the present study was to evaluate the potential of the 50-aa N-terminal domain of amastin proteins harboring the conserved 11-aa amastin signature peptide as a relevant immune biomarker of cutaneous leishmaniasis (CL) and visceral leishmaniasis (VL). We report here the amastin-binding total immunoglobulins (IgG) and/or IgG subclasses in the sera of patients at different stages of CL (n=90) and VL (n=41). In CL cases, there is no significant difference in seroreactivities between active, recovered, and nonhealed cases. However, the amastin peptide-reactive antibodies were present at high titers in 19 of 20 sera collected from patients with active VL compared to sera from patients recovered from VL and asymptomatic cases of VL. These data suggest that the amastin signature peptide could represent a relevant biomarker for the serodiagnosis of VL and, most importantly, that it could permit differentiation among the different stages of the disease.