Evolutionary and geographical history of the Leishmania donovani complex with a revision of current taxonomy

Adaptive immunity against Leishmania nucleoside hydrolase maps its c-terminal domain as the target of the CD4+ T cell-driven protective response

Nucleoside hydrolases (NHs) show homology among parasite protozoa, fungi and bacteria. They are vital protagonists in the establishment of early infection and, therefore, are excellent candidates for the pathogen recognition by adaptive immune responses. Immune protection against NHs would prevent disease at the early infection of several pathogens. We have identified the domain of the NH of L. donovani (NH36) responsible for its immunogenicity and protective efficacy against murine visceral leishmaniasis (VL). Using recombinant generated peptides covering the whole NH36 sequence and saponin we demonstrate that protection against L. chagasi is related to its C-terminal domain (amino-acids 199-314) and is mediated mainly by a CD4+ T cell driven response with a lower contribution of CD8+ T cells. Immunization with this peptide exceeds in 36.73±12.33% the protective response induced by the cognate NH36 protein. Increases in IgM, IgG2a, IgG1 and IgG2b antibodies, CD4+ T cell proportions, IFN-γ secretion, ratios of IFN-γ/IL-10 producing CD4+ and CD8+ T cells and percents of antibody binding inhibition by synthetic predicted epitopes were detected in F3 vaccinated mice. The increases in DTH and in ratios of TNFα/IL-10 CD4+ producing cells were however the strong correlates of protection which was confirmed by in vivo depletion with monoclonal antibodies, algorithm predicted CD4 and CD8 epitopes and a pronounced decrease in parasite load (90.5-88.23%; p = 0.011) that was long-lasting. No decrease in parasite load was detected after vaccination with the N-domain of NH36, in spite of the induction of IFN-γ/IL-10 expression by CD4+ T cells after challenge. Both peptides reduced the size of footpad lesions, but only the C-domain reduced the parasite load of mice challenged with L. amazonensis. The identification of the target of the immune response to NH36 represents a basis for the rationale development of a bivalent vaccine against leishmaniasis and for multivalent vaccines against NHs-dependent pathogens.

Universal PCR assays for the differential detection of all Old World Leishmania species

For the epidemiological monitoring and clinical case management of leishmaniasis, determination of the causative Leishmania species gains importance. Current assays for the Old World often suffer from drawbacks in terms of validation on a geographically representative sample set and the ability to recognize all species complexes. We want to contribute to standardized species typing for Old World leishmaniasis. We determined the ribosomal DNA internal transcribed spacer 1 sequence of 24 strains or isolates, and validated four species-specific polymerase chain reactions (PCRs) amplifying this target. They discriminate L. aethiopica, L. tropica, L. major, and the L. donovani complex, use the same cycling conditions, and include an internal amplification control. Our PCRs amplify 0.1 pg of Leishmania DNA, while being 100% specific for species identification on an extensive panel of geographically representative strains and isolates. Similar results were obtained in an endemic reference laboratory in Kenya. Species could also be identified in clinical specimens. The presented PCRs require only agarose gel detection, and have several other advantages over many existing assays. We outline potential problems, suggest concrete solutions for transferring the technique to other settings, and deliver the proof-of-principle for analyzing clinical samples.

Species discrimination and phylogenetic inference of 17 Chinese Leishmania isolates based on internal transcribed spacer 1 (ITS1) sequences

Leishmaniasis is a geographically widespread disease, caused by protozoan flagellates of the genus Leishmania. This disease still remains endemic in China, especially in the west and northwest frontier regions. To date, the phylogenetic relationships among Chinese Leishmania isolates are still unclear, and the possible taxonomic diversity remains to be established. In this study, the ITS1-5.8S fragments of ten isolates collected from different foci in China were determined. To infer the phylogenetic relationships among them, seven sequences of Chinese Leishmania isolates retrieved from GenBank were also included. Both parsimony and Bayesian analyses reveal an unexpected but strongly supported clade comprising eight newly determined isolates, which is sister to other members of subgenus Leishmania. In combination with genetic distance analysis, this provides evidence of the occurrence of an undescribed species of Leishmania. Our results also suggest that (1) the isolate IPHL/CN/77/XJ771 from Bachu County, Xinjiang Uygur Autonomous Region is not Leishmania infantum but Leishmania donovani; (2) the status referring to an isolate MRHO/CN/88/KXG-2 from a great gerbil in Karamay as Leishmania turanica, formerly based on multilocus enzyme electrophoresis, is recognized; (3) an earlier finding demonstrating the L. donovani identity of isolate MHOM/CN/80/801 from Kashi city is corroborated; (4) the three isolates from eastern Jiashi County, Xinjiang Uygur Autonomous Region, causing desert type of zoonotic visceral leishmaniasis (see Wang et al., Parasitol Int (in press), 2010), belong to L. donovani instead of L. infantum. In addition, the results of this study make an important contribution to understanding the heterogeneity and relationships of Chinese Leishmania isolates, further indicating that the isolates from China may have had a more complex evolutionary history than expected.

Heterogeneity of Leishmania infantum chagasi kinetoplast DNA in Teresina (Brazil)

Leishmania infantum chagasi is the causative agent of visceral leishmaniasis in Brazil. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of kinetoplast DNA (kDNA) minicircles was used to evaluate genetic profiles of 48 Leishmania infantum chagasi strains from dog and human parasite cultures, fresh collected dog bone marrow aspirates, and from infected sand flies. Results revealed that heterogeneity in kDNA minicircles depends mostly on the source of the samples, with cultured parasites showing a high degree of homogeneity.

An enhanced method for the identification of Leishmania spp. using real-time polymerase chain reaction and sequence analysis of the 7SL RNA gene region

The accurate identification of Leishmania spp. is important for the treatment of infected patients. Molecular methods offer an alternative to time-consuming traditional laboratory techniques for species determination. We redesigned a 7SL RNA gene-based polymerase chain reaction and sequence assay for increased species identification. DNA extracted from 17 reference strains and 10 cultured clinical isolates was examined. Sequence comparison was used successfully to identify organisms to the complex level with intercomplex similarity ranging from 77.5% to 98.4%. Many species within each complex were discriminated accurately by this method including Leishmania major, Leishmania tropica, Leishmania aethiopica, Leishmania guyanensis, and the previously indistinguishable Leishmania braziliensis and Leishmania panamensis. The Leishmania donovani complex members remain indistinguishable by this method, as are the representatives of Leishmania amazonensis/Leishmania garnhami and Leishmania mexicana/Leishmania pifanoi.

Spatial analysis of Leishmania donovani exposure in humans and domestic animals in a recent kala azar focus in Nepal

SUMMARY

Visceral leishmaniasis (VL) is a major public health problem in the Indian subcontinent where the Leishmania donovani transmission cycle is described as anthroponotic. However, the role of animals (in particular domestic animals) in the persistence and expansion of VL is still a matter of debate. We combined Direct Agglutination Test (DAT) results in humans and domestic animals with Geographic Information System technology (i.e. extraction maps and scan statistic) to evaluate the exposure to L. donovani on these 2 populations in a recent VL focus in Nepal. A Poisson regression model was used to assess the risk of infection in humans associated with, among other factors, the proportion of DAT-positive animals in the proximities of the household. The serological results showed that both humans and domestic animals were exposed to L. donovani. DAT-positive animals and humans were spatially clustered. The presence of serologically positive goats (IRR=9.71), past VL cases (IRR=2.62) and the proximity to a forest island dividing the study area (IRR=3.67) increased the risk of being DAT-positive in humans. Even if they are not a reservoir, domestic animals, and specially goats, may play a role in the distribution of L. donovani, in particular in this new VL focus.

Heat-shock protein 70 PCR-RFLP: a universal simple tool for Leishmania species discrimination in the New and Old World

Introduction. Species typing in leishmaniasis gains importance in diagnostics, epidemiology, and clinical studies. A restriction fragment length polymorphism (RFLP) assay of PCR amplicons from a partial heat-shock protein 70 gene (hsp70) had been described for the New World, allowing identification of some species. Methods. Based on an initial in silico analysis of 51 hsp70 sequences, most of which we recently determined in the frame of a phylogenetic study, species-specific restriction sites were identified. These were tested by PCR-RFLP on 139 strains from 14 species, thereby documenting both inter- and intra-species variability. Results. Our assay could identify Leishmania infantum, L. donovani, L. tropica, L. aethiopica, L. major, L. lainsoni, L. naiffi, L. braziliensis, L. peruviana, L. guyanensis, and L. panamensis by applying 2 subsequent digests. L. mexicana, L. amazonensis, and L. garnhami did not generate species-specific restriction fragment patterns. Conclusion. Currently no assay is available for global Leishmania species discrimination. We present a universal PCR-RFLP method allowing identification of most medically relevant Old and New World Leishmania species on the basis of a single PCR, obviating the need to perform separate PCRs. The technique is simple to perform and can be implemented in all settings where PCR is available.

Treatment of canine visceral leishmaniasis by the vaccine Leish-111f+MPL-SE

Immunotherapy of canine visceral leishmaniasis (CVL) may provide an alternative to both marginally effective chemotherapy and undesired euthanasia of infected dogs and could have a great impact not only on animal welfare, but also on control of human disease. Therefore, we examined the potential immunotherapeutic efficacy of the subunit vaccine Leish-111f+MPL-SE, which has undergone rigorous preclinical testing and been demonstrated safe in human clinical trials. Two separate trials were performed in Salvador, Brazil, to evaluate the vaccine for therapeutic efficacy against CVL caused by natural infection: an Open Trial and a Blinded Trial. In the Open Trial 59 dogs with clinically active CVL were sequentially allocated to four groups: group 1 received Leish-111f+MPL-SE; group 2 was treated with Glucantime; group 3 received a combination of the vaccine and Glucantime; and group 4 was given no treatment. At the 6-month assessment, the 13 non-treated dogs had either died or showed no clinical improvement. In contrast, most dogs in groups 1-3 showed initial improvement (100%, 80%, and 92%, respectively). Upon evaluation for a mean of 36 months after therapy, the following cure rates were observed: 75% for group 1 dogs (exact 95% confidence interval [CI] 43-95%), 64% for group 2 dogs (exact 95% CI 31-89%), and 50% for group 3 dogs (exact 95% CI 19-81%). Therapeutic efficacy of the Leish-111f+MPL-SE vaccine was reconfirmed in a subsequent Blinded Trial. The vaccine was effective for mild cases of CVL and was compromised in dogs with severe disease. Although further studies are required to understand mechanisms of action, the Leish-111f+MPL-SE vaccine is a promising tool to control VL in both dogs and humans.

Neglected and endemic zoonoses

Endemic zoonoses are found throughout the developing world, wherever people live in close proximity to their animals, affecting not only the health of poor people but often also their livelihoods through the health of their livestock. Unlike newly emerging zoonoses that attract the attention of the developed world, these endemic zoonoses are by comparison neglected. This is, in part, a consequence of under-reporting, resulting in underestimation of their global burden, which in turn artificially downgrades their importance in the eyes of administrators and funding agencies. The development of cheap and effective vaccines is no guarantee that these endemic diseases will be eliminated in the near future. However, simply increasing awareness about their causes and how they may be prevented-often with very simple technologies-could reduce the incidence of many endemic zoonoses. Sustainable control of zoonoses is reliant on surveillance, but, as with other public-sector animal health services, this is rarely implemented in the developing world, not least because of the lack of sufficiently cheap diagnostics. Public-private partnerships have already provided advocacy for human disease control and could be equally effective in addressing endemic zoonoses.

Phylogeny of Leishmania species based on the heat-shock protein 70 gene

The 70kDa heat-shock protein (HSP70) is conserved across prokaryotes and eukaryotes, and the protein as well as its encoding gene have been applied in phylogenetic studies of different parasites. In spite of the frequent use of New World Leishmania species identification on the basis of restriction fragment length polymorphisms (RFLP) in the hsp70 gene, it was never sequenced extensively for studying evolutionary relationships. To fill this void we determined the nucleotide sequence of an 1380bp fragment of the coding region commonly used in RFLP analysis, from 43 isolates and strains of different geographic origins. Combination with previously determined sequences amounted to a phylogenetic analysis including 52 hsp70 sequences representing 17 species commonly causing leishmaniasis both in the New and Old World. The genus Leishmania formed a monophyletic group with three distinct subgenera L. (Leishmania), L. (Viannia), and L. (Sauroleishmania). The obtained phylogeny supports the following eight species: L. (L.) donovani, L. (L.) major, L. (L.) tropica, L. (L.) mexicana, L. (V.) lainsoni, L. (V.) naiffi, L. (V.) guyanensis and L. (V.) braziliensis, in some of which subspecies can be recognized: L. (L.) donovani infantum, L. (V.) guyanensis panamensis, and L. (V.) braziliensis peruviana. The currently recognized L. (L.) aethiopica, L. (L.) garnhami, and L. (L.) amazonensis did not form monophyletic clusters. These findings are discussed in relation to results from other genes and proteins, which have to be integrated in order to build a genetically supported taxonomy for the entire genus.

Transmission, reservoir hosts and control of zoonotic visceral leishmaniasis

Zoonotic visceral leishmaniasis (ZVL) caused by Leishmania infantum is an important disease of humans and dogs. Here we review aspects of the transmission and control of ZVL. Whilst there is clear evidence that ZVL is maintained by sandfly transmission, transmission may also occur by non-sandfly routes, such as congenital and sexual transmission. Dogs are the only confirmed primary reservoir of infection. Meta-analysis of dog studies confirms that infectiousness is higher in symptomatic infection; infectiousness is also higher in European than South American studies. A high prevalence of infection has been reported from an increasing number of domestic and wild mammals; updated host ranges are provided. The crab-eating fox Cerdocyon thous, opossums Didelphis spp., domestic cat Felis cattus, black rat Rattus rattus and humans can infect sandflies, but confirmation of these hosts as primary or secondary reservoirs requires further xenodiagnosis studies at the population level. Thus the putative sylvatic reservoir(s) of ZVL remains unknown. Review of intervention studies examining the effectiveness of current control methods highlights the lack of randomized controlled trials of both dog culling and residual insecticide spraying. Topical insecticides (deltamethrin-impregnated collars and pour-ons) have been shown to provide a high level of individual protection to treated dogs, but further community-level studies are needed.

Nucleoside hydrolase DNA vaccine against canine visceral leishmaniasis

The Nucleoside Hydrolase (NH36) is the main marker of the FML complex of Leishmania donovani, antigen of the licensed Leishmune® vaccine for prophylaxis of canine visceral leishmaniasis. As a DNA vaccine in mice, it induces a TH1 immune response. We vaccinated mongrel dogs with the VR1012NH36 vaccine for prophylaxis and immunotherapy against a high dose Leishmania chagasi infection (7 x 108 infective amastigotes). The untreated controls developed more symptoms, higher parasite/lymphocyte ratio, smaller DTH reactions, lower proportions of NH36-specific CD4+ cells and sustained NH36-specific CD8+ cell counts than dogs of the prophylaxis group. In the immunotherapy treated group, enlarged DTH reactions, enhanced CD4+ and sustained CD8+ lymphocyte proportions were also detected, however, without reduction of symptoms or parasite/lymphocyte ratio, indicating that the vaccine was sufficiently potent to prevent but not to control the disease. Both treatments determined higher survival rates. Anti-FML antibodies increased in vaccinated and control dogs while anti-NH36 antibodies were only increased in vaccinees (p= 0.000). The parasite load of an untreated survivor control dog (638.05 parasites) felt outside the IC95% of that of vaccinated dogs (32.02, IC95% 9.45-64.59) suggesting that both vaccination treatments succeeded in reducing the Leishmania infective burden. Accordingly, an untreated control dog showed lower levels of IFN γ-β, IL-2, IL4 but not IL-10 β actin-relative quantification. We conclude that the VR1012-NH36 vaccine induces strong prophylactic protection and a milder immunotherapeutic effect against a high dose canine experimental infection with Leishmania chagasi.

The molecular epidemiology and phylogeography of Trypanosoma cruzi and parallel research on Leishmania: looking back and to the future

Trypanosoma cruzi is the protozoan agent of Chagas disease, and the most important parasitic disease in Latin America. Protozoa of the genus Leishmania are global agents of visceral and cutaneous leishmaniasis, fatal and disfiguring diseases. In the 1970s multilocus enzyme electrophoresis demonstrated that T. cruzi is a heterogeneous complex. Six zymodemes were described, corresponding with currently recognized lineages, TcI and TcIIa-e – now defined by multiple genetic markers. Molecular epidemiology has substantially resolved the phylogeography and ecological niches of the T. cruzi lineages. Genetic hybridization has fundamentally influenced T. cruzi evolution and epidemiology of Chagas disease. Genetic exchange of T. cruzi in vitro involves fusion of diploids and genome erosion, producing aneuploid hybrids. Transgenic fluorescent clones are new tools to elucidate molecular genetics and phenotypic variation. We speculate that pericardial sequestration plays a role in pathogenesis. Multilocus sequence typing, microsatellites and, ultimately, comparative genomics are improving understanding of T. cruzi population genetics. Similarly, in Leishmania, genetic groups have been defined, including epidemiologically important hybrids; genetic exchange can occur in the sand fly vector. We describe the profound impact of this parallel research on genetic diversity of T. cruzi and Leishmania, in the context of epidemiology, taxonomy and disease control.

Population genetics of Leishmania infantum in Israel and the Palestinian Authority through microsatellite analysis

Multilocus microsatellite typing (MLMT) was used to investigate the genetic variation among 44 Israeli and Palestinian strains of L. infantum isolated from infected dogs and human cases to determine their population structure and to compare them with strains isolated from different European countries. Most of the Israeli and Palestinian strains had their own individual MLMT profiles; a few shared the same profile. A Bayesian model-based approach and phylogenetic reconstructions based on genetic distances inferred two main populations that were significantly different from the European strains: population A, containing 16 strains from places in the West Bank and 11 strains from central Israel;and population B, containing 7 strains from northern Israel, 9 from central Israel, and one Palestinian strain from the Jenin District.Geographically distributed sub-populations were detected within population B. These results demonstrate similar disease dynamics in Israel and the Palestinian Authority. The re-emergence of VL in the case of population A is more likely owing to increased dog and human contact with sylvatic cycles of parasitic infection rather than to recent introduction from the older foci of northern Israel. The latter scenario could be true for population B found in few foci of Central Israel.

Cutaneous leishmaniasis: disease susceptibility and pharmacogenetic implications

Cutaneous leishmaniasis is a major tropical infection of public health importance caused by a number of vector-borne Leishmania protozoa species. Evidence supports a highly complex etiology. Environmental, parasite and host factors determine pathogenesis, and result in a diverse clinical spectrum of disease. Disease susceptibility, clinical course, prognosis and therapy response are highly variable, suggesting a genetic basis. Epidemiological studies have demonstrated familial aggregation, and family and association studies have identified HLA and non-HLA gene associations. Further progress in susceptibility gene identification for leishmaniasis would require genome-wide scans and candidate gene-association studies in large cohorts. Correlation between host genotype and therapy response has important pharmacogenetic implications, especially as current therapies for leishmaniasis are inadequate and progress in new drug development has been poor.

Demonstration of genetic exchange during cyclical development of Leishmania in the sand fly vector

Genetic exchange has not been shown to be a mechanism underlying the extensive diversity of Leishmania parasites. We report here evidence that the invertebrate stages of Leishmania are capable of having a sexual cycle consistent with a meiotic process like that described for African trypanosomes. Hybrid progeny were generated that bore full genomic complements from both parents, but kinetoplast DNA maxicircles from one parent. Mating occurred only in the sand fly vector, and hybrids were transmitted to the mammalian host by sand fly bite. Genetic exchange likely contributes to phenotypic diversity in natural populations, and analysis of hybrid progeny will be useful for positional cloning of the genes controlling traits such as virulence, tissue tropism, and drug resistance.

PCR and direct agglutination as Leishmania infection markers among healthy Nepalese subjects living in areas endemic for Kala-Azar

OBJECTIVE

To compare a PCR assay and direct agglutination test (DAT) for the detection of potential markers of Leishmania infection in 231 healthy subjects living in a kala-azar endemic focus of Nepal.

METHODS

The sample was composed of 184 (80%) persons without any known history of KA and not living in the same house as known kala-azar cases (HNK), 24 (10%) Healthy Household Contacts (HHC) and 23 (10%) past kala-azar cases which had been successfully treated (HPK).

RESULTS

PCR and DAT positivity scores were, respectively: HNK, 17.6% and 5.6%; HHC, 12.5% and 20.8%; HPK, 26.1% and 95.7%. The ratio PCR-positives/DAT-positives was significantly higher in HNK (ratio = 3.1) than in HHC (ratio = 0.6, P = 0.036) and in HPK (ratio = 0.2, P = 0.012). The ratio PCR-positives/DAT-positives did not significantly differ between HHC (ratio = 0.6) and HPK (ratio = 0.2, P = 0.473). The positive agreement index between PCR and DAT in HNK was 5%; in HHC, 0%; in HPK, 43%.

CONCLUSIONS

Our study highlights the specific character of PCR and DAT for the exploration of Leishmania asymptomatic infections. PCR is probably more informative for very recent infections among HNK, while DAT provides more information among HHC and HPK, a feature likely related to the power of serology to track less recent infections.

Gene expression modulation is associated with gene amplification, supernumerary chromosomes and chromosome loss in antimony-resistant Leishmania infantum

Antimonials remain the first line drug against the protozoan parasite Leishmania but their efficacy is threatened by resistance. We carried out a RNA expression profiling analysis comparing an antimony-sensitive and -resistant (Sb2000.1) strain of Leishmania infantum using whole-genome 70-mer oligonucleotide microarrays. Several genes were differentially expressed between the two strains, several of which were found to be physically linked in the genome. MRPA, an ATP-binding cassette (ABC) gene known to be involved in antimony resistance, was overexpressed in the antimony-resistant mutant along with three other tandemly linked genes on chromosome 23. This four gene locus was flanked by 1.4 kb repeated sequences from which an extrachromosomal circular amplicon was generated in the resistant cells. Interestingly, gene expression modulation of entire chromosomes occurred in the antimony-resistant mutant. Southern blots analyses and comparative genomic hybridizations revealed that this was either due to the presence of supernumerary chromosomes or to the loss of one chromosome. Leishmania parasites with haploid chromosomes were viable. Changes in copy number for some of these chromosomes were confirmed in another antimony-resistant strain. Selection of a partial revertant line correlated antimomy resistance levels and the copy number of aneuploid chromosomes, suggesting a putative link between aneuploidy and drug resistance in Leishmania.

Identification of Old World Leishmania spp. by specific polymerase chain reaction amplification of cysteine proteinase B genes and rapid dipstick detection

We used the cysteine proteinase B (cpb) gene family of the trypanosomatid genus Leishmania as a target to develop rapid, specific, and easy-to-use polymerase chain reaction (PCR) tests to discriminate Leishmania infantum, Leishmania donovani, Leishmania tropica, Leishmania aethiopica, and Leishmania major. Identification of all 5 Old World species and validation of intraspecies variability are features lacking in other species-specific PCRs. Amplicon analysis was done on agarose gels and was further simplified by using an oligochromatography dipstick to detect L. infantum and L. donovani products. Because the analytical sensitivity is lower than that of certain other species- and genus-specific PCRs, our assays are especially valuable for use on cultured isolates or directly on cryostabilates. As such, they can be implemented by research and health centers having access to culturing, DNA isolation, and PCR.

RNA editing and mitochondrial activity in promastigotes and amastigotes of Leishmania donovani

Kinetoplast maxicircle DNA sequence organisation was investigated in Leishmania donovani, strain 1S LdBob. Gene arrangement in the coding (conserved) region of the maxicircle is collinear with that of most trypanosomatids, with individual genes showing 80-90% nucleotide identity to Leishmania tarentolae, strain UC. The notable exception was an integration of a full-size minicircle sequence in the ND1 gene coding region found in L. donovani. Editing patterns of the mitochondrial mRNAs investigated also followed L. tarentolae UC patterns, including productive editing of the components of respiratory complexes III-V, and ribosomal protein S12 (RPS12), as well as the lack of productive editing in five out of six pan-edited cryptogenes (ND3, ND8, ND9, G3, G4) found in these species. Several guide RNAs for the editing events were localised in minicircles and maxicircles in the locations that are conserved between the species. Mitochondrial activity, including rates of oxygen consumption, the presence and the levels of respiratory complexes and their individual subunits and the steady-state levels of several mitochondrial-encoded mRNAs were essentially the same in axenically grown amastigotes and in promastigotes of L. donovani. However, some modulation of mitochondrial activity between these developmental stages was suggested by the finding of an amastigote-specific component in complex IV, a down-regulation of mitochondrial RNA-binding proteins (MRP) and MRP-associated protein (MRP-AP) in amastigotes, and by variations in the levels of RPS12, ND3, ND9, G3 and G4 pre-edited transcripts.

Cutaneous leishmaniasis with lymphadenopathy due to Leishmania donovani

We describe a case of cutaneous leishmaniasis with lymphadenopathy due to Leishmania donovani, which was successfully treated with oral miltefosine. Given the increased prevalence of travelling, patients presenting with lymph-node enlargement should have leishmaniasis included in the differential diagnosis even in the absence of typical ulceration.

Distinct antigen recognition pattern during zoonotic visceral leishmaniasis in humans and dogs

Leishmania infantum is a causative agent of endemic zoonotic visceral leishmaniasis (VL) in regions of South America and the Mediterranean. Dogs are the major reservoirs for L. infantum in these regions, and control of disease in dogs could have a significant impact on human disease. Although dogs share many symptoms of VL with humans as a result of L. infantum infection, they also show some unique clinical manifestations, which are often a combination of visceral and cutaneous leishmaniasis, suggesting different mechanisms of disease development in dogs and humans. Here, we compare antibody responses of dogs and humans with VL to various defined leishmanial antigens. Parasite lysate and K39, the two most commonly used antigens for serodiagnosis of VL, detected the highest levels of antibodies in both humans and dogs with VL, whereas the recognition patterns of these antigens were distinct between the hosts. Among other defined antigens tested, LmSTI1 and CPB detected higher levels of antibodies in dogs and humans, respectively. These results indicate there is a difference between humans and dogs in antigen recognition patterns during VL. We infer that different strategies may need to be used in development of vaccines and diagnostics for humans and for dogs. In addition, we show a correlation between antibody titers to several antigens and severity of clinical symptoms during canine VL.

FML vaccine against canine visceral leishmaniasis: from second-generation to synthetic vaccine

The Leishmania donovani glycoprotein fraction, known as FML, successfully underwent preclinical and clinical (Phase I-III) vaccine trials against canine visceral leishmaniasis (92-95% of protection and 76-80% of vaccine efficacy) when formulated with a QS21 saponin-containing adjuvant. It became the licensed Leishmune vaccine for canine prophylaxis in Brazil. The immune response raised by the vaccine is long lasting, immunotherapeutic and reduces dog infectivity blocking the transmission of the disease, as revealed by an in vivo assay. The preliminary epidemiological control data of vaccinated areas in Brazil indicate that, in spite of the still low vaccine coverage, there was a significant decrease in the incidence of the human and canine disease. A 36-kDa glycoprotein, in the FML complex, is the human marker of the disease, which was protective in mice as native recombinant protein or DNA vaccine. The DNA vaccine is now being tested against the canine disease. This review resumes the development of the second-generation FML-saponin-Leishmune vaccine, its adjuvant and of the NH36 DNA vaccine, toward the identification of its major epitopes that might be included in a possible future synthetic vaccine.

Leishmania sand fly interaction: progress and challenges

Complex interactions occurs between Leishmania parasites and their sand fly vectors. Promastigotes of Leishmania live exclusively within the gut, possess flagella and are motile, and kinesins, kinases and G proteins have been described that play a role in regulating flagellar assembly. Movement within the gut is not random: promastigotes can detect gradients of solutes via chemotaxis and osmotaxis. Further they use their flagella to attach to the fly midgut using surface glyconconjugates, a key step in establishment of the infection. Differentiation of mammal-infective stages is characterised by significant biochemical and cellular remodelling. Further, the parasites can manipulate the behaviour of the vector to maximise their transmission, and flies may even deliver altruistic apoptotic forms to aid transmission of infective stages.

Differentiation and gene flow among European populations of Leishmania infantum MON-1

BACKGROUND

Leishmania infantum is the causative agent of visceral and cutaneous leishmaniasis in the Mediterranean region, South America, and China. MON-1 L. infantum is the predominating zymodeme in all endemic regions, both in humans and dogs, the reservoir host. In order to answer important epidemiological questions it is essential to discriminate strains of MON-1.

METHODOLOGY/PRINCIPAL FINDINGS

We have used a set of 14 microsatellite markers to analyse 141 strains of L. infantum mainly from Spain, Portugal, and Greece of which 107 strains were typed by MLEE as MON-1. The highly variable microsatellites have the potential to discriminate MON-1 strains from other L. infantum zymodemes and even within MON-1 strains. Model- and distance-based analysis detected a considerable amount of structure within European L. infantum. Two major monophyletic groups-MON-1 and non-MON-1-could be distinguished, with non-MON-1 being more polymorphic. Strains of MON-98, 77, and 108 were always part of the MON-1 group. Among MON-1, three geographically determined and genetically differentiated populations could be identified: (1) Greece; (2) Spain islands-Majorca/Ibiza; (3) mainland Portugal/Spain. All four populations showed a predominantly clonal structure; however, there are indications of occasional recombination events and gene flow even between MON-1 and non-MON-1. Sand fly vectors seem to play an important role in sustaining genetic diversity. No correlation was observed between Leishmania genotypes, host specificity, and clinical manifestation. In the case of relapse/re-infection, only re-infections by a strain with a different MLMT profile can be unequivocally identified, since not all strains have individual MLMT profiles.

CONCLUSION

In the present study for the first time several key epidemiological questions could be addressed for the MON-1 zymodeme, because of the high discriminatory power of microsatellite markers, thus creating a basis for further epidemiological investigations.

Molecular diagnosis of Old World cutaneous leishmaniasis and species identification by use of a reverse line blot hybridization assay

Reverse line blot hybridization assays (RLB) have been used for the rapid diagnosis and genotyping of many pathogens. The leishmaniases are caused by a large number of species, and rapid, accurate parasite characterization is important in deciding on appropriate therapy. Fourteen oligonucleotide probes, 2 genus specific and 12 species specific (2 specific for Leishmania major, 3 for L. tropica, 1 for L. infantum, 3 for L. donovani, and 3 for L. aethiopica), were prepared by using DNA sequences in the internal transcribed spacer 1 (ITS1) region of the rRNA genes. Probe specificity was evaluated by amplifying DNA from 21 reference strains using biotinylated ITS1 PCR primers and the RLB. The genus-specific probes, PP and PP3', recognized all Leishmania species examined, while the species-specific probes were able to distinguish between all the Old World Leishmania species. Titrations using purified parasite DNA showed that the RLB is 10- to 100-fold more sensitive than ITS1 PCR and can detect <0.1 pg DNA. The RLB was compared to kinetoplast DNA (kDNA) and ITS1 PCR by using 67 samples from suspected cutaneous leishmaniasis (CL) patients in Israel and the West Bank. The RLB accurately identified 58/59 confirmed positive samples as CL, a result similar to that found by kDNA PCR (59/59) and better than that by ITS1 PCR (50/59). The positive predictive value and negative predictive value of the RLB were 95.1% and 83.3%, respectively. L. major or L. tropica was identified by the RLB in 55 of the confirmed positive cases, a level of accuracy better than that of ITS1 PCR with restriction fragment length polymorphism (42/59). Thus, RLB can be used to diagnose and characterize Old World CL.

Leishmania: origin, evolution and future since the Precambrian

This brief review discusses the history of leishmaniasis, considering its origin from the Paleoartic, Neoartic or Neotropic. We reassess some of the theories of the likely origin of this protozoan since the beginning of life on Earth, passing through the Mesozoic and continuing to the appearance of humans. The relationship between this parasite or its ancestors, possible vectors and hosts with regard to ecological modifications is discussed. Recent molecular techniques have helped to elucidate some of the evolutionary questions regarding Leishmania, but have also brought doubts about the origin and evolution of this human parasite. PCR has been used for studies in the new discipline of paleoparasitology, helping to elucidate some of the remaining evolutionary questions. Understanding of this global condition is fundamental in determining the best approach to use against the parasite, specifically for the development of an efficient vaccine.

A Leishmania minicircle DNA footprint assay for sensitive detection and rapid speciation of clinical isolates

BACKGROUND

Diversity in clinical outcome, due to different species of Leishmania, and its presence in asymptomatic blood donors in endemic areas warrant development of methods that are sensitive and can rapidly identify infecting species.

STUDY DESIGN AND METHODS

The kinetoplast minicircle DNA is known to have heterogeneity in sequence and is present in many thousands of copies in Leishmania. Fluorescence-based polymerase chain reaction (PCR) was used to amplify minicircle DNA from six Leishmania species from different geographic locations. The sequences were then used to construct a phylogenetic tree. Speciation of 46 blinded parasite clinical isolates from various geographic regions was validated using the assay.

RESULTS

Analysis displayed a distinct cluster for each species or strain. Forty-three of 46 isolates were correctly assigned to the same species identified by isoenzyme electrophoresis. The three untyped isolates were all either new species or samples from a unique geographic region. The minicircles of the three isolates formed new clusters in the tree analysis. Using minicircle DNA as PCR target, the sensitivity of the parasite detection in the spiked blood samples was five parasites per mL.

CONCLUSION

Increased sensitivity and speciation without the need for parasite culture will be useful for diagnosis and treatment in clinical settings.

Leishmania manipulates sandfly feeding to enhance its transmission

Malaria parasites manipulate mosquitoes to ensure transmission between mammalian hosts; painstaking experiments have now demonstrated that another medically important protozoan, Leishmania, enhances its transmission through the adaptive manipulation of one of its sandfly vectors, Lutzomyia longipalpis. Experimental Leishmania infections specifically increased sandfly biting persistence and feeding on multiple hosts, but only if the parasites produced infective forms and a gel plug of filamentous proteophosphoglycan in the anterior midgut of the sandfly. This fundamental research is relevant to vaccine development.

The large subunit of Leishmania topoisomerase I functions as the 'molecular steer' in type IB topoisomerase

Kinetoplastid topoisomerase IB is an unusual bisubunit enzyme where reconstitution of the large (LdTOPIL or L) and small (LdTOPIS or S) subunits shows functional activity. It is yet to be deciphered whether one subunit or both navigate the heterodimer to its cellular DNA targets. Tethering a specific DNA-binding protein to topoisomerase I alters its site specificity. The chimeric constructs UMSBP-LdTOPIL/S or U-L/S (fusion of UMSBP to the N-terminus of L and reconstituted with S) and LdTOPIL/UMSBP-LdTOPIS or L/U-S (fusion of UMSBP to the N-terminus of S and reconstituted with L) exhibit relaxation activity. Only U-L/S shows altered site specificity and enhanced DNA-binding affinity for the universal minicircle sequence (UMS) containing substrate. This proves that L alone serves as the 'molecular steer' for this heterodimer. Reconstituted U-L/S also induces cleavage close to UMS and causes minicircle linearization. The differential properties of the reconstituted chimeras U-L/S and L/U-S reveal the structural and functional asymmetry between the heterodimer. Therefore this study helps in a better understanding of the mechanistic details underlying topoisomerization by this bi-subunit enzyme.

Comparative genomics: from genotype to disease phenotype in the leishmaniases

Recent progress in sequencing the genomes of several Leishmania species, causative agents of cutaneous, mucocutaneous and visceral leishmaniasis, is revealing unusual features of potential relevance to parasite virulence and pathogenesis in the host. While the genomes of Leishmania major, Leishmania braziliensis and Leishmania infantum are highly similar in content and organisation, species-specific genes and mechanisms distinguish one from another. In particular, the presence of retrotransposons and the components of a putative RNA interference machinery in L. braziliensis suggest the potential for both greater diversity and more tractable experimentation in this Leishmania Viannia species.