INTRODUCTION: Visceral leishmaniasis (VL), a neglected tropical disease that causes substantial morbidity and mortality, is a serious health problem in Ethiopia. Infections are caused by Leishmania (L.) donovani parasites. Most individuals remain asymptomatic, but some develop VL, which is generally fatal if not treated. We identified the area of Metema-Humera in Northwest Ethiopia as a setting in which we could follow migrant workers when they arrived in an endemic area. The demographic characteristics of this population and factors associated with their risk of asymptomatic infection are poorly characterised. METHODS: We divided our cohort into individuals who visited this area for the first time (first comers, FC) and those who had already been in this area (repeat comers, RC). We followed them from the beginning (Time 1, T1) to the end of the agricultural season (Time 2, T2), performing tests for sand fly bite exposure (anti-sand fly saliva antibody ELISA) and serology for Leishmania infection (rK39 rapid diagnostic test and the direct agglutination test) at each time point and collecting information on risk factors for infection. RESULTS: Our results show that most migrant workers come from non-endemic areas, are male, young (median age of 20 years) and are farmers or students. At T1, >80% of them had been already exposed to sand fly bites, as shown by the presence of anti-saliva antibodies. However, due to seasonality of sand flies there was no difference in exposure between FC and RC, or between T1 and T2. The serology data showed that at T1, but not at T2, a significantly higher proportion of RC were asymptomatic. Furthermore, 28.6% of FC became asymptomatic between T1 and T2. Over the duration of this study, one FC and one RC developed VL. In multivariable logistic regression of asymptomatic infection at T1, only age and the number of visits to Metema/Humera were significantly associated with asymptomatic infection. CONCLUSION: A better understanding of the dynamics of parasite transmission and the risk factors associated with the development of asymptomatic infections and potentially VL will be essential for the development of new strategies to prevent leishmaniasis.

• Klíčová slova
• Leishmania, PCR, asymptomatic, direct agglutination test, rK39, risk factors, visceral leishmaniasis,
• Publikační typ
• časopisecké články MeSH

Trypanosomatid pathogens are transmitted by blood-feeding insects, causing devastating human infections. These parasites show important phenotypic shifts that often impact parasite pathogenicity, tissue tropism, or drug susceptibility. The evolutionary mechanisms that allow for the selection of such adaptive phenotypes remain only poorly investigated. Here, we use Leishmania donovani as a trypanosomatid model pathogen to assess parasite evolutionary adaptation during experimental sand fly infection. Comparing the genome of the parasites before and after sand fly infection revealed a strong population bottleneck effect as judged by allele frequency analysis. Apart from random genetic drift caused by the bottleneck effect, our analyses revealed haplotype and allelic changes during sand fly infection that seem under natural selection given their convergence between independent biological replicates. Our analyses further uncovered signature mutations of oxidative DNA damage in the parasite genomes after sand fly infection, suggesting that Leishmania suffers from oxidative stress inside the insect digestive tract. Our results propose a model of Leishmania genomic adaptation during sand fly infection, with oxidative DNA damage and DNA repair processes likely driving haplotype and allelic selection. The experimental and computational framework presented here provides a useful blueprint to assess evolutionary adaptation of other eukaryotic pathogens inside their insect vectors, such as Plasmodium spp, Trypanosoma brucei, and Trypanosoma cruzi.

• Klíčová slova
• Leishmania, allelic selection, sand fly infection,
• MeSH
• Leishmania donovani * MeSH
• lidé MeSH
• mutace MeSH
• oprava DNA genetika   MeSH
• oxidační stres genetika   MeSH
• Psychodidae * MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The protozoan parasite Leishmania donovani causes fatal human visceral leishmaniasis in absence of treatment. Genome instability has been recognized as a driver in Leishmania fitness gain in response to environmental change or chemotherapy. How genome instability generates beneficial phenotypes despite potential deleterious gene dosage effects is unknown. Here we address this important open question applying experimental evolution and integrative systems approaches on parasites adapting to in vitro culture. Phenotypic analyses of parasites from early and late stages of culture adaptation revealed an important fitness tradeoff, with selection for accelerated growth in promastigote culture (fitness gain) impairing infectivity (fitness costs). Comparative genomics, transcriptomics and proteomics analyses revealed a complex regulatory network associated with parasite fitness gain, with genome instability causing highly reproducible, gene dosage-independent and -dependent changes. Reduction of flagellar transcripts and increase in coding and non-coding RNAs implicated in ribosomal biogenesis and protein translation were not correlated to dosage changes of the corresponding genes, revealing a gene dosage-independent, post-transcriptional mechanism of regulation. In contrast, abundance of gene products implicated in post-transcriptional regulation itself correlated to corresponding gene dosage changes. Thus, RNA abundance during parasite adaptation is controled by direct and indirect gene dosage changes. We correlated differential expression of small nucleolar RNAs (snoRNAs) with changes in rRNA modification, providing first evidence that Leishmania fitness gain in culture may be controlled by post-transcriptional and epitranscriptomic regulation. Our findings propose a novel model for Leishmania fitness gain in culture, where differential regulation of mRNA stability and the generation of modified ribosomes may potentially filter deleterious from beneficial gene dosage effects and provide proteomic robustness to genetically heterogenous, adapting parasite populations. This model challenges the current, genome-centric approach to Leishmania epidemiology and identifies the Leishmania transcriptome and non-coding small RNome as potential novel sources for the discovery of biomarkers that may be associated with parasite phenotypic adaptation in clinical settings.

• MeSH
• Leishmania donovani * genetika   MeSH
• leishmanióza viscerální * parazitologie   MeSH
• lidé MeSH
• nestabilita genomu MeSH
• proteomika MeSH
• regulace genové exprese MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

BACKGROUND: Ethiopia is affected by human leishmaniasis caused by several Leishmania species and transmitted by a variety of sand fly vectors of the genus Phlebotomus. The sand fly fauna in Ethiopia is highly diverse and some species are closely related and similar in morphology, resulting in difficulties with species identification that requires deployment of molecular techniques. DNA barcoding entails high costs, requires time and lacks reference sequences for many Ethiopian species. Yet, proper species identification is pivotal for epidemiological surveillance as species differ in their actual involvement in transmission cycles. Recently, protein profiling using MALDI-TOF mass spectrometry has been introduced as a promising technique for sand fly identification. METHODS: In our study, we used an integrative taxonomic approach to identify most of the important sand fly vectors of leishmaniasis in Ethiopia, applying three complementary methods: morphological assessment, sequencing analysis of two genetic markers, and MALDI-TOF MS protein profiling. RESULTS: Although morphological assessment resulted in some inconclusive identifications, both DNA- and protein-based techniques performed well, providing a similar hierarchical clustering pattern for the analyzed species. Both methods generated species-specific sequences or protein patterns for all species except for Phlebotomus pedifer and P. longipes, the two presumed vectors of Leishmania aethiopica, suggesting that they may represent a single species, P. longipes Parrot & Martin. All three approaches also revealed that the collected specimens of Adlerius sp. differ from P. (Adlerius) arabicus, the only species of Adlerius currently reported in Ethiopia, and molecular comparisons indicate that it may represent a yet undescribed new species. CONCLUSIONS: Our study uses three complementary taxonomical methods for species identification of taxonomically challenging and yet medically import Ethiopian sand flies. The generated MALDI-TOF MS protein profiles resulted in unambiguous identifications, hence showing suitability of this technique for sand fly species identification. Furthermore, our results contribute to the still inadequate knowledge of the sand fly fauna of Ethiopia, a country severely burdened with human leishmaniasis.

• Klíčová slova
• DNA barcoding, Ethiopia, MALDI-TOF mass spectrometry, Morphology, Phlebotomus, Protein profiling, Sand flies,
• MeSH
• druhová specificita MeSH
• fylogeneze MeSH
• hmyz - vektory klasifikace   MeSH
• leishmanióza MeSH
• Psychodidae klasifikace   MeSH
• spektrometrie hmotnostní - ionizace laserem za účasti matrice metody   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Etiopie epidemiologie   MeSH

The clinical manifestation of leishmaniases depends on parasite species, host genetic background, and immune response. Manifestations of human leishmaniases are highly variable, ranging from self-healing skin lesions to fatal visceral disease. The scope of standard model hosts is insufficient to mimic well the wide disease spectrum, which compels the introduction of new model animals for leishmaniasis research. In this article, we study the susceptibility of three Asian rodent species (Cricetulus griseus, Lagurus lagurus, and Phodopus sungorus) to Leishmania major and L. donovani. The external manifestation of the disease, distribution, as well as load of parasites and infectiousness to natural sand fly vectors, were compared with standard models, BALB/c mice and Mesocricetus auratus. No significant differences were found in disease outcomes in animals inoculated with sand fly- or culture-derived parasites. All Asian rodent species were highly susceptible to L. major. Phodopus sungorus showed the non-healing phenotype with the progressive growth of ulcerative lesions and massive parasite loads. Lagurus lagurus and C. griseus represented the healing phenotype, the latter with high infectiousness to vectors, mimicking best the character of natural reservoir hosts. Both, L. lagurus and C. griseus were also highly susceptible to L. donovani, having wider parasite distribution and higher parasite loads and infectiousness than standard model animals.

• Klíčová slova
• Cricetulus griseus, Lagurus lagurus, Phlebotomus, Phodopus sungorus, cutaneous leishmaniasis, infectiousness, model animals, sand fly, visceral leishmaniasis, xenodiagnosis,
• Publikační typ
• časopisecké články MeSH

Parasites of the genus Leishmania (Kinetoplastida: Trypanosomatidae) cause widespread and devastating human diseases. Visceral leishmaniasis due to Leishmania donovani is endemic in Ethiopia where it has also been responsible for major epidemics. The presence of hybrid genotypes has been widely reported in surveys of natural populations, genetic variation reported in a number of Leishmania species, and the extant capacity for genetic exchange demonstrated in laboratory experiments. However, patterns of recombination and the evolutionary history of admixture that produced these hybrid populations remain unclear. Here, we use whole-genome sequence data to investigate Ethiopian L. donovani isolates previously characterized as hybrids by microsatellite and multi-locus sequencing. To date there is only one previous study on a natural population of Leishmania hybrids based on whole-genome sequences. We propose that these hybrids originate from recombination between two different lineages of Ethiopian L. donovani occurring in the same region. Patterns of inheritance are more complex than previously reported with multiple, apparently independent, origins from similar parents that include backcrossing with parental types. Analysis indicates that hybrids are representative of at least three different histories. Furthermore, isolates were highly polysomic at the level of chromosomes with differences between parasites recovered from a recrudescent infection from a previously treated individual. The results demonstrate that recombination is a significant feature of natural populations and contributes to the growing body of data that shows how recombination, and gene flow, shape natural populations of Leishmania.

• MeSH
• chiméra * MeSH
• genotyp MeSH
• Leishmania donovani genetika   MeSH
• leishmanióza viscerální parazitologie   MeSH
• lidé MeSH
• rekombinace genetická MeSH
• sekvenování celého genomu MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Etiopie MeSH

BACKGROUND: Hosts repeatedly bitten by sand flies develop antibodies against sand fly saliva and screening of these immunoglobulins can be employed to estimate the risk of Leishmania transmission, to indicate the feeding preferences of sand flies, or to evaluate the effectiveness of vector control campaigns. Previously, antibodies to sand fly saliva were detected using whole salivary gland homogenate (SGH) or recombinant proteins, both of which also have their disadvantages. This is the first study on sand flies where short peptides designed based on salivary antigens were successfully utilized for antibody screening. METHODOLOGY/PRINCIPAL FINDINGS: Specific IgG was studied in hosts naturally exposed to Phlebotomus orientalis, the main vector of Leishmania donovani in East Africa. Four peptides were designed by the commercial program EpiQuest-B, based on the sequences of the two most promising salivary antigens, yellow-related protein and ParSP25-like protein. Short amino acid peptides were synthesised and modified for ELISA experiments. Specific anti-P. orientalis IgG was detected in sera of dogs, goats, and sheep from Ethiopia. The peptide OR24 P2 was shown to be suitable for antibody screening; it correlated positively with SGH and its specificity and sensitivity were comparable or even better than that of previously published recombinant proteins. CONCLUSIONS/SIGNIFICANCE: OR24 P2, the peptide based on salivary antigen of P. orientalis, was shown to be a valuable tool for antibody screening of domestic animals naturally exposed to P. orientalis. We suggest the application of this promising methodology using species-specific short peptides to other sand fly-host combinations.

• MeSH
• ELISA metody   MeSH
• imunoglobulin G krev   MeSH
• kozy MeSH
• ovce MeSH
• peptidy imunologie   MeSH
• Phlebotomus imunologie   MeSH
• plošný screening metody   MeSH
• protilátky krev   MeSH
• psi MeSH
• senzitivita a specificita MeSH
• slinné proteiny a peptidy imunologie   MeSH
• zvířata MeSH
• Check Tag
• psi MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• hodnotící studie MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Etiopie MeSH
• Názvy látek
• imunoglobulin G MeSH
• peptidy MeSH
• protilátky MeSH
• slinné proteiny a peptidy MeSH

BACKGROUND: Phlebotomus orientalis is a vector of Leishmania donovani, the causative agent of life threatening visceral leishmaniasis spread in Eastern Africa. During blood-feeding, sand fly females salivate into the skin of the host. Sand fly saliva contains a large variety of proteins, some of which elicit specific antibody responses in the bitten hosts. To evaluate the exposure to sand fly bites in human populations from disease endemic areas, we tested the antibody reactions of volunteers' sera against recombinant P. orientalis salivary antigens. METHODOLOGY/PRINCIPAL FINDINGS: Recombinant proteins derived from sequence data on P. orientalis secreted salivary proteins, were produced using either bacterial (five proteins) or mammalian (four proteins) expression systems and tested as antigens applicable for detection of anti-P. orientalis IgG in human sera. Using these recombinant proteins, human sera from Sudan and Ethiopia, countries endemic for visceral leishmaniasis, were screened by ELISA and immunoblotting to identify the potential markers of exposure to P. orientalis bites. Two recombinant proteins; mAG5 and mYEL1, were identified as the most promising antigens showing high correlation coefficients as well as good specificity in comparison to the whole sand fly salivary gland homogenate. Combination of both proteins led to a further increase of correlation coefficients as well as both positive and negative predictive values of P. orientalis exposure. CONCLUSIONS/SIGNIFICANCE: This is the first report of screening human sera for anti-P. orientalis antibodies using recombinant salivary proteins. The recombinant salivary proteins mYEL1 and mAG5 proved to be valid antigens for screening human sera from both Sudan and Ethiopia for exposure to P. orientalis bites. The utilization of equal amounts of these two proteins significantly increased the capability to detect anti-P. orientalis antibody responses.

• MeSH
• ELISA MeSH
• hmyzí proteiny genetika   imunologie   MeSH
• imunoglobulin G imunologie   MeSH
• kousnutí a bodnutí hmyzem imunologie   parazitologie   MeSH
• lidé MeSH
• Phlebotomus genetika   imunologie   fyziologie   MeSH
• rekombinantní proteiny genetika   imunologie   MeSH
• slinné proteiny a peptidy genetika   imunologie   MeSH
• sliny imunologie   MeSH
• tvorba protilátek MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• východní Afrika MeSH
• Názvy látek
• hmyzí proteiny MeSH
• imunoglobulin G MeSH
• rekombinantní proteiny MeSH
• slinné proteiny a peptidy MeSH

BACKGROUND: Leishmania development in sand flies is confined to the alimentary tract and is closely connected with blood meal digestion. Previously, it has been published that activities of sand fly midgut proteases are harmful to Leishmania, especially to amastigote-promastigote transition forms. However, our experiments with various Leishmania-sand fly pairs gave quite opposite results. METHODS: We evaluated the effect of semi-digested midgut content on different life stages of Leishmania donovani and Leishmania major in vitro. Various morphological forms of parasites, including macrophage-derived amastigotes and transition forms, were incubated 2 h with midguts dissected at various intervals (6-72 h) post-blood meal or with commercially available proteinase, and their viability was determined using flow cytometry. In parallel, using amastigote-initiated experimental infections, we compared development of L. donovani in sand flies that are either susceptible (Phlebotomus argentipes and P. orientalis) or refractory (P. papatasi and Sergentomyia schwetzi) to this parasite. RESULTS: In vitro, sand fly midgut homogenates affected L. major and L. donovani in a similar way; in all sand fly species, the most significant mortality effect was observed by the end of the blood meal digestion process. Surprisingly, the most susceptible Leishmania stages were promastigotes, while mortality of transforming parasites and amastigotes was significantly lower. Parasites were also susceptible to killing by rabbit blood in combination with proteinase, but resistant to proteinase itself. In vivo, L. donovani developed late-stage infections in both natural vectors; in P. argentipes the development was much faster than in P. orientalis. On the other hand, in refractory species P. papatasi and S. schwetzi, promastigotes survived activity of digestive enzymes but were lost during defecation. CONCLUSIONS: We demonstrated that Leishmania transition forms are more resistant to the killing effect of semi-digested blood meal than 24 h-old promastigotes. Data suggest that Leishmania mortality is not caused directly by sand fly proteases, we assume that this mortality results from toxic products of blood meal digestion. Survival of L. donovani promastigotes in refractory sand flies until blood meal defecation, together with similar mortality of Leishmania parasites incubated in vitro with midgut homogenates of susceptible as well as refractory species, contradict the previously raised hypotheses about the role of midgut proteases in sand fly vector competence to Leishmania.

• Klíčová slova
• Blood meal digestion, Leishmania donovani, Leishmania major, Phlebotomus, Proteases, Sand fly, Sergentomyia,
• MeSH
• gastrointestinální trakt enzymologie   parazitologie   MeSH
• králíci MeSH
• krev metabolismus   MeSH
• Leishmania donovani fyziologie   MeSH
• Leishmania major fyziologie   MeSH
• Phlebotomus parazitologie   MeSH
• proteasy metabolismus   MeSH
• viabilita buněk MeSH
• zvířata MeSH
• Check Tag
• králíci MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• proteasy MeSH

Leishmania parasites alternate in their life cycle between promastigote stages that develop in the gut of phlebotomine sand flies and amastigotes residing inside phagocytic cells of vertebrate hosts. For experimental infections of sand flies, promastigotes are frequently used as this way of infection is technically easier although ingestion of promastigotes by sand flies is unnatural. Here we aimed to answer a critical question, to what extent do promastigote-initiated experimental infections differ from those initiated with intracellular amastigotes. We performed side-by-side comparison of Leishmania development in Phlebotomus argentipes females infected alternatively with promastigotes from log-phase cultures or amastigotes grown ex vivo in macrophages. Early stage infections showed substantial differences in parasite load and representation of morphological forms. The differences disappeared along the maturation of infections; both groups developed heavy late-stage infections with colonization of the stomodeal valve, uniform representation of infective metacyclics and equal efficiency of transmission. The results showed that studies focusing on early phase of Leishmania development in sand flies should be initiated with intracellular amastigotes. However, the use of promastigote stages for sand fly infections does not alter significantly the final outcome of Leishmania donovani development in P. argentipes and their transmissibility to the vertebrate host.

• Klíčová slova
• Leishmania donovani, Phlebotomus, amastigotes, promastigotes, transmission,
• MeSH
• hmyz - vektory parazitologie   MeSH
• interakce hostitele a parazita MeSH
• Leishmania donovani růst a vývoj   MeSH
• leishmanióza viscerální parazitologie   přenos   MeSH
• myši inbrední BALB C MeSH
• myši MeSH
• Phlebotomus parazitologie   MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH