Biology subjects

Reis-Cunha, J. L.

Publications and source records attributed to Reis-Cunha, J. L..

11 recordsLinked to original sources

bioRxiv2026

Human settlement drives population divergence of Leishmania guyanensis at the sylvatic-anthropogenic interface

The Amazon is the largest tropical rainforest in the world, and is an important interface between natural rainforest and anthropogenic environments. In the central Amazon region, Leishmania guyanensis is a common agent of cutaneous leishmaniasis (CL), a disfiguring vector-borne disease that circulates between wild mammalian reservoirs and sandfly vectors in sylvatic cycles. People become infected when they interact or disturb this cycle. At present, little is known about the adaptation of Leishmania parasites at the interface between sylvatic and anthropogenic environments. Here, to characterize CL in a transition zone, we conducted a population genomic analysis of 77 Leishmania isolates from human patients living in Manauss outskirts or in highways adjacent to the Brazilian Amazon rainforest. We discovered two L. guyanensis populations; an ancestral sylvatic population occurring in densely forested areas far from the city and a derived population, occurring in areas with lower forest cover closer to the city (the city-proximal population). The genomic divergence between these populations indicates that their separation occurred relatively recently, consistent with human-driven development of a new transmission cycle for CL in the Manaus region. The lack of recent gene flow between these populations indicates that the newer city-proximal population has established a transmission cycle that operates independently from ancestral sylvatic transmission. This provides a striking example of the adaptation of disease transmission to an environment that has been altered by human activity. Significance StatementEmerging infectious diseases often arise at the interface between natural and human-modified environments. One of these important interfaces is the Amazon, the largest rainforest in the world. We analyzed the population genomics of Leishmania guyanensis, the agent of cutaneous leishmaniasis in the Amazon, typically transmitted in sylvatic cycles. Our findings reveal a recent emergence of a L. guyanensis population associated with anthropogenic environment alterations, which is genetically distinct from the ancestral sylvatic lineage. This newly adapted population highlights how landscape change and urban expansion may drive the evolution and emergence of protozoan vector-borne pathogens at the rainforest-urban interface.

evolutionary biology↗

bioRxiv2024

The global dispersal of visceral leishmaniasis occurred within human history

The Leishmania donovani species complex (LdSC) causes visceral leishmaniasis (VL), is present in Africa, Europe, the Middle East, Asia and the Americas, and causes 20-40,000 fatalities per year. Previous analyses concluded that dispersal of this species complex occurred 1-10 million years ago. Using updated methods and data, we show that a ten-thousand year old East African population dispersed globally only within the last 2,000 years, consistent with human migration, war and colonisation as driving factors.

evolutionary biology↗

bioRxiv2024

Estimating the rate of sexual reproduction and the inbreeding rate in Leishmania

Many eukaryotic species undergo sexual reproduction facultatively, either in response to stress or in particular environments. For the remainder of their life cycle they reproduce by mitosis. This facultative sex may be rare, which alters features of their evolutionary dynamics. Both the frequency of sex and the degree of inbreeding have been challenging to estimate from genome-scale polymorphism data. Here, we describe a method to estimate both these parameters based on the Moran model of heterozygous sites. We apply this method to population genomic data from Leishmania parasitic protozoans from the Leishmania donovani species complex, showing that these parasites undergo sexual reproduction approximately once per 10,000 generations and that populations vary considerably in the extent of their inbreeding.

genetics↗

bioRxiv2023

Aneuploidies are an ancestral feature of trypanosomatids, and an ancient chromosome duplication is maintained in extant species

BackgroundAneuploidy is widely observed in both unicellular and multicellular eukaryotes, usually associated with adaptation to stress conditions. Chromosomal duplication stability is a tradeoff between the fitness cost of having unbalanced gene copies and the potential fitness gained from increased dosage of specific advantageous genes. Trypanosomatids, a family of protozoans which include species that cause neglected tropical diseases, are a relevant group to study aneuploidies, as their life cycle has several stressors that would benefit from the rapid adaptation provided by aneuploidies. ResultsBy evaluating the data from 866 isolates covering 7 Trypanosomatids genera, we have observed that aneuploidies are present in the majority of clades, and have a reduced occurrence in a specific monophyletic clade that has undergone large genomic reorganisation and chromosomal fusions. We have also identified an ancient chromosomal duplication that was maintained across these parasites speciations, which has increased sequence diversity, unusual gene structure and expression regulation. ConclusionAneuploidies are an important and ancestral feature in Trypanosomatids. Chromosomal duplication/loss is a constant event in these protozoans, common in Leishmania and Leptomonas and repressed in T. brucei and closely related protozoans. The number of chromosomes with extra copies in a given isolate is usually low, and only one chromosomal duplication was kept for long enough to greatly impact its nucleotide diversity. The thigh control of gene expression in this chromosome suggests that these parasites have adapted to mitigate the fitness cost of having this ancient chromosomal duplication.

genomics↗

bioRxiv2022

Phylogeny-aware linear B-cell epitope predictor detects candidate targets for specific immune responses to Monkeypox virus

Monkeypox is a disease caused by the Monkeypox virus (MPXV), a double-stranded DNA virus from genus Orthopoxvirus under family Poxviridae, that has recently emerged as a global health threat after decades of local outbreaks in Central and Western Africa. Effective epidemiological control against this disease requires the development of cheaper, faster diagnostic tools to monitor its spread, including antigen and serological testing. There is, however, little available information about MPXV epitopes, particularly those that would be effective in discriminating between MPXV infections and those by other virus from the same family. We used the available data from the Immune Epitope Database (IEDB) to generate and validate a predictive model optimised for detecting linear B-cell epitopes (LBCEs) from Orthopoxvirus, based on a phylogeny-aware data selection strategy. By coupling this predictive approach with conservation and similarity analyses, we identified nine specific peptides from MPXV that are likely to represent distinctive LBCEs for the diagnostic of Monkeypox infections, including the independent detection of a known epitope experimentally characterised as a potential specific diagnostic target for MPXV. The results obtained indicate ability of the proposed pipeline to uncover promising targets for the development of cheaper, more specific diagnostic tests for this emerging viral disease. A full reproducibility package (including code, data, and outputs) is available at https://doi.org/10.5281/zenodo.7838331.

bioinformatics↗

bioRxiv2022

Strong effects of parasite genotype on drug susceptibility in the Indian subcontinent

Intracellular parasites of the Leishmania donovani species complex cause visceral leishmaniasis (VL). For parasitic diseases, VL has a mortality rate second only to malaria, and is associated with poverty-stricken areas of the world: primarily Brazil, East Africa and the Indian subcontinent (ISC). Miltefosine (MIL) and the antimonal sodium stibogluconate (SSG) are drugs used in the treatment of leishmaniasis. However, treatment efficacy is variable, and the numbers of reports of parasite resistance to both drugs have risen since their introductions, particularly in the ISC. To assess the level of parasite genotype contribution to drug resistance, we utilised the sequencing and associated drug susceptibility data from Imamura et al. (2016) to estimate heritability and GWAS using LDAK. We obtained strong heritability results, with mainly SNP/indel variations associated with SSG and copy number variants associated with MIL resistance, respectively. However, GWAS results were inconclusive, suggesting that, although the parasite genotype directly influences drug resistance, the effect might be multifactorial.

evolutionary biology↗

bioRxiv2022

Parasite genotype is a major predictor of mortality from visceral leishmaniasis

Abstract/SummaryO_ST_ABSBackgroundC_ST_ABSVisceral leishmaniasis (VL) is a potentially fatal disease mainly caused by Leishmania infantum in South America and L. donovani in Asia and Africa. Disease outcomes have been associated with patient genotype, nutrition, age, sex, comorbidities, and co-infections. In this study, we examine the effects of parasite genetic variation on VL disease severity in Brazil. MethodsWe collected and sequenced the genomes of 109 L. infantum isolates from patients in northeast Brazil and retrieved matching patient clinical data from medical records, including mortality, sex, HIV co-infection and laboratory data (creatinine, haemoglobin, leukocyte and platelet counts). We identified genetic differences between parasite isolates, including single nucleotide polymorphisms (SNPs), small insertions/deletions (indels), and variations in genic, intergenic, and chromosome copy numbers (copy number variants, CNVs). To describe associations between the parasite genotypes and clinical outcomes, we applied quantitative genetics methods of heritability and genome-wide association studies (GWAS), treating clinical outcomes as traits that may be influenced by parasite genotype. FindingsMultiple aspects of the genetic analysis indicate that parasite genotype affects clinical outcomes. We estimate that parasite genotype explains 83% chance of mortality (narrow sense heritability, h2 = 0{middle dot}83{+/-}0{middle dot}17), and has a significant relationship with patient sex (h2 = 0{middle dot}60{+/-}0{middle dot}27). Impacts of parasite genotype on other clinical traits are lower (h2 [≤]0{middle dot}34). GWAS analysis identified multiple parasite genetic loci that were significantly associated with clinical outcomes; 17 CNVs that were significantly associated with mortality, two with creatinine and one with bacterial co-infection, jaundice and HIV co-infection; and two SNPs/indels and six CNVs that associate with age, jaundice, HIV and bacterial co-infections, creatinine, and/or bleeding sites. InterpretationParasite genotype is an important factor in VL disease severity in Brazil. Our analysis indicates that specific genetic differences between parasites act as virulence factors, enhancing risks of severe disease and mortality. More detailed understanding of these virulence factors could be exploited for novel therapies. Author SummaryMultiple factors contribute to the risk of mortality from visceral leishmaniasis (VL), including, patient genotype, comorbidities, and nutrition. Many of these factors will be influenced by socio-economic biases 1. Our work suggests that the virulence of the infecting parasite is an important risk factor for mortality. We pinpoint some specific genomic markers that are associated with mortality, which can lead to a greater understanding of the molecular mechanisms that cause severe VL disease, to genetic markers for virulent parasites and to the development of drug and vaccine therapies.

evolutionary biology↗

bioRxiv2021

Multi-objective prioritisation of candidate epitopes for diagnostic test development

BackgroundThe development of peptide-based diagnostic tests requires the identification of epitopes that are at the same time highly immunogenic and, ideally, unique to the pathogen of interest, to minimise the chances of cross-reactivity. Existing computational pipelines for the prediction of linear B-cell epitopes tend to focus exclusively on the first objective, leaving considerations of cross-reactivity to later stages of test development. ResultsWe present a multi-objective approach to the prioritisation of candidate epitopes for experimental validation, in the context of diagnostic test development. The dual objectives of uniqueness (measured as dissimilarity from known epitope sequences from other pathogens) and predicted immunogenicity (measured as the probability score returned by the prediction model) are considered simultaneously. Validation was performed using data from three distinct pathogens (namely the nematode Onchocerca volvulus, the Epstein-Barr Virus and the Hepatitis C Virus), with predictions derived using an organism-specific prediction approach. The multi-objective rankings returned sets of non-dominated solutions as potential targets for the development of diagnostic tests with lower probability of false positives due to cross-reactivity. ConclusionsThe application of the proposed approach to three test pathogens led to the identification of 20 new potential epitopes, with both high probability and a high degree of exclusivity to the target organisms. The results indicate the potential of the proposed approach to provide enhanced filtering and ranking of potential candidates, highlighting potential cross-reactivities and including this information into the test development process right from the target identification and prioritisation step.

bioinformatics↗

bioRxiv2018

Detection of multiple circulating Leishmania species in Lutzomyia longipalpis in the city of Governador Valadares, southeastern Brazil

BackgroundLeishmaniasis encompasses a group of diverse clinical diseases caused by protozoan parasites of the Leishmania genus. This disease is a major public health problem in the New World affecting people exposed in endemic regions. The city of Governador Valadares (Minas Gerais/Brazil) is a re-emerging area for visceral leishmaniasis, with 191 human cases reported from 2008 to 2017 and a lethality rate of 14.7%. The transmission of the parasite occurs intensely in this region with up to 22% of domestic dogs with positive serology for the visceral form. Lu. longipalpis is one of the most abundant sand fly species in this area. Despite this scenario, so far there is no information regarding the circulating Leishmania species in the insect vector Lutzomyia longipalpis in this focus.\n\nMethodology/Principal FindingsWe collected 616 female Lutzomyia longipalpis sand flies between January and September 2015 in the Vila Parque Ibituruna neighborhood (Governador Valadares/MG), which is located on a transitional area between the sylvatic and urban environments with residences built near a preserved area. After DNA extraction of individual sand flies, the natural Leishmania infections in Lu. longipalpis were detected by end-point PCR, using primers derived from kDNA sequences, specific for L. (Leishmania) or L. (Viannia) subgenus. The sensitivity of these PCR reactions was 0.1 pg of DNA for each Leishmania subgenus and the total infection rate of 16.2% (100 positive specimens). Species-specific PCR detected the presence of multiple Leishmania species in infected Lu. longipalpis specimens in Governador Valadares, including L. amazonensis (n=3), L. infantum (n=28), L. (Viannia) spp. (n=20), coinfections with L. infantum and L. (Viannia) spp. (n=5), and L. (Leishmania) spp (n=44).\n\nConclusionsOur results demonstrate that multiple Leishmania species circulate in Lu. longipalpis in Governador Valadares and reveal a potential increasing risk of transmission of the different circulating parasite species. This information is a key factor for planning surveillance and effective control strategies against leishmaniasis in this endemic focus.\n\nAuthor summaryLeishmaniasis is a neglected tropical disease transmitted to mammals by the bite of sand flies infected with parasites of the Leishmania genus. This disease affects millions of people in various regions of the world, including Brazil. The municipality of Governador Valadares (Minas Gerais/Brazil) is a re-emergent focus of intense transmission of leishmaniasis, with a high number of human cases and a high prevalence of infected domestic dogs. To develop better leishmaniasis control strategies for the region, we performed a surveillance study of Lu. longipalpis, the main vector of visceral leishmaniasis in Brazil, and identified circulating species of Leishmania in this insect vector. We estimate that the natural infection rate of Lu. longipalpis for these parasites was of 16.2% in the study area. We also detected the presence of multiple circulating Leishmania species (L. amazonensis, L. infantum and Viannia subgenus) in Lu. longipalpis in Governador Valadares city, including 5 sand flies coinfected with L. infantum and L. (Viannia). Thus, our results reinforce the need for a rigid and systematic control of the sand flies monitoring in this area, due to the potential risk of transmission of different species of the Leishmania parasites.

epidemiology↗

bioRxiv2018

Repeat-driven generation of antigenic diversity in a major human pathogen, Trypanosoma cruzi

Trypanosoma cruzi, a zoonotic kinetoplastid protozoan with a complex genome, is the causative agent of American trypanosomiasis (Chagas disease). The parasite uses a highly diverse repertoire of surface molecules, with roles in cell invasion, immune evasion and pathogenesis. Thus far, the genomic regions containing these genes have been impossible to resolve and it has been impossible to study the structure and function of the several thousand repetitive genes encoding the surface molecules of the parasite. We here present an improved genome assembly of a T. cruzi clade I (TcI) strain using high coverage PacBio single molecule sequencing, together with Illumina sequencing of 34 T. cruzi TcI isolates and clones from different geographic locations, sample sources and clinical outcomes. Resolution of the surface molecule gene structure reveals an unusual duality in the organisation of the parasite genome, a core genomic region syntenous with related protozoa flanked by unique and highly plastic subtelomeric regions encoding surface antigens. The presence of abundant interspersed retrotransposons in the subtelomeres suggests that these elements are involved in a recombination mechanism for the generation of antigenic variation and evasion of the host immune response. The comparative genomic analysis of the cohort of TcI strains revealed multiple cases of such recombination events involving surface molecule genes and has provided new insights into T. cruzi population structure.

genomics↗

bioRxiv2017

ProphET, Prophage Estimation Tool: a standalone prophage sequence prediction tool with self-updating reference database

Prophages are a significant force in prokaryote evolution. The remaining sequences of a bacteriophage integration event are known for altering gene expression, enabling creative destruction of the bacterial genome and to induce pathogenicity by harboring and transposing virulence and antibiotic resistance factors. In the light of the dreadful expansion of antibiotic resistance bacteriophages have gathered renewed interest from the scientific community and public health decision makers as a promising long forgotten alternative to control bacterial infections. Cataloging the repertoire of prophages and their integration sites is an important initial step in the understanding of bacteriophages either as tool or as a threat. In this work, we present ProphET (Prophage Estimation Tool), a standalone application without the limitations of their web based counterparts and which identifies prophages in bacterial genomes with higher precision than similar applications.

bioinformatics↗