Infections and Coinfections by Trypanosomatid Parasites in a Rural Community of Venezuela

Animal models for exploring Chagas disease pathogenesis and supporting drug discovery

SUMMARYInfections with the parasitic protozoan Trypanosoma cruzi cause Chagas disease, which results in serious cardiac and/or digestive pathology in 30%-40% of individuals. However, symptomatic disease can take decades to become apparent, and there is a broad spectrum of possible outcomes. The complex and long-term nature of this infection places a major constraint on the scope for experimental studies in humans. Accordingly, predictive animal models have been a mainstay of Chagas disease research. The resulting data have made major contributions to our understanding of parasite biology, immune responses, and disease pathogenesis and have provided a platform that informs and facilitates the global drug discovery effort. Here, we provide an overview of available animal models and illustrate how they have had a key impact across the field.

Redefining infections with trypanosomatids in Neotropical primates: Case study of the white-footed tamarin (Oedipomidas leucopus)

Trypanosomes are blood parasites capable of infecting nearly any vertebrate. Many Neotropical primates frequently host trypanosomes and are considered potential reservoirs for Trypanosoma cruzi and other human-pathogenic trypanosomatids. However, diagnostic methods originally developed for detecting these trypanosomatids in humans and domestic species must be validated to reliably diagnose infections in non-human primates. Without such validation, taxonomic biases and incorrect assignments of wildlife reservoirs can occur. The white-footed tamarin (Oedipomidas leucopus), a primate endemic to northwestern Colombia, is classified by the World Health Organization as a reservoir of T. cruzi. However, this classification is based on studies with small sample sizes, ambiguous diagnostic methods, and questionable geographic records. In this study, the 18S ribosomal RNA gene was amplified via PCR and sequenced to estimate trypanosome infection rates and identify species in natural populations of O. leucopus across a wide geographic range, as well as in (ex situ) specimens. This molecular approach was also compared with traditional microscopy diagnosis using blood smears. The molecular diagnosis revealed that over 60% of the tested specimens were infected, whereas traditional microscopy resulted in 58% false negatives compared to the molecular method. A Bayesian phylogeny of the 18S gene identified T. minasense as the sole trypanosomatid species present in O. leucopus, with no detections of T. cruzi or other trypanosomatids of concern to human or domestic animal health. This study highlights the risk of overestimating the presence of human-infecting trypanosomes, such as T. cruzi, in tamarins and other vertebrates, and underscores the importance of validating diagnostic methods to accurately assess the zoonotic potential of wild species. Accurate identification of wildlife reservoirs is essential for understanding parasite life cycles and implementing effective management and conservation strategies for primates and other potential reservoirs.

Immune signaling pathways in Rhodnius prolixus in the context of Trypanosoma rangeli infection: cellular and humoral immune responses and microbiota modulation

Introduction

Rhodnius prolixus is a hematophagous insect and one of the main vectors for Trypanosoma cruzi and Trypanosoma rangeli parasites in Latin America. Gut microbiota and insect immune responses affect T. cruzi and T. rangeli infection within triatomines. Particularly the Toll and IMD signaling pathways activations and how they orchestrate the antimicrobial peptides (AMPs) expressions in R. prolixus, especially when infected by T. rangeli.

Objectives

Examine how T. rangeli infection modulates R. prolixus cellular and humoral immunity and its impacts on insect microbiota.

Methods

R. prolixus was fed on blood containing epimastigotes of T. rangeli, and infection was quantified in insect tissues. The gene expression of dorsal, cactus, relish, PGRP, and AMPs was examined in the midgut, fat body, and salivary glands by quantitative real-time PCR. Microbiota composition was analyzed using RT-q PCR targeting specific bacterial species. Hemocyte numbers and phenoloxidase activity were quantified to assess cellular immune responses.

Results

T. rangeli infection modulated triatomine immunity in midgut and hemocoel, activating the expression of the NF-kB gene dorsal, associated with the Toll pathway; increasing expression of the gene encoding PGRP receptor, a component involved in the IMD pathway, both in the intestine and fat body; repressing the expression of the relish transcription factor, mainly in salivary glands. Among the R. prolixus AMPs studied, T. rangeli infection repressed all AMP gene expression, other than defensin C which increased mRNA levels. The PO activity was enhanced in the hemolymph of infected insects. T. rangeli infection did not induce hemocyte number alterations compared to control insects. However, an increase in hemocyte microaggregation was detected in infected insects.

Discussion

R. prolixus recognizes T. rangeli infection and triggers humoral and cellular immune responses involving Toll pathway activation, defensin C synthesis, increased phenoloxidase activity, and enhanced hemocyte aggregation. On the other hand, T. rangeli infection suppressed some IMD pathway components, suggesting that, in R. prolixus, this pathway is involved in defensins A and B gene regulation. Importantly, these immune responses altered the bacterial microbiota composition, potentially favoring T. rangeli establishment in the insect vector.

Chagas Disease: A Silent Threat for Dogs and Humans

Chagas disease (CD) is a vector-borne Neglected Zoonotic Disease (NZD) caused by a flagellate protozoan, Trypanosoma cruzi, that affects various mammalian species across America, including humans and domestic animals. However, due to an increase in population movements and new routes of transmission, T. cruzi infection is presently considered a worldwide health concern, no longer restricted to endemic countries. Dogs play a major role in the domestic cycle by acting very efficiently as reservoirs and allowing the perpetuation of parasite transmission in endemic areas. Despite the significant progress made in recent years, still there is no vaccine against human and animal disease, there are few drugs available for the treatment of human CD, and there is no standard protocol for the treatment of canine CD. In this review, we highlight human and canine Chagas Disease in its different dimensions and interconnections. Dogs, which are considered to be the most important peridomestic reservoir and sentinel for the transmission of T. cruzi infection in a community, develop CD that is clinically similar to human CD. Therefore, an integrative approach, based on the One Health concept, bringing together the advances in genomics, immunology, and epidemiology can lead to the effective development of vaccines, new treatments, and innovative control strategies to tackle CD.

Integrated Computational Approaches for Drug Design Targeting Cruzipain

Cruzipain inhibitors are required after medications to treat Chagas disease because of the need for safer, more effective treatments. Trypanosoma cruzi is the source of cruzipain, a crucial cysteine protease that has driven interest in using computational methods to create more effective inhibitors. We employed a 3D-QSAR model, using a dataset of 36 known inhibitors, and a pharmacophore model to identify potential inhibitors for cruzipain. We also built a deep learning model using the Deep purpose library, trained on 204 active compounds, and validated it with a specific test set. During a comprehensive screening of the Drug Bank database of 8533 molecules, pharmacophore and deep learning models identified 1012 and 340 drug-like molecules, respectively. These molecules were further evaluated through molecular docking, followed by induced-fit docking. Ultimately, molecular dynamics simulation was performed for the final potent inhibitors that exhibited strong binding interactions. These results present four novel cruzipain inhibitors that can inhibit the cruzipain protein of T. cruzi.

Chagas Disease and Leishmaniasis, Sympatric Zoonoses Present in Human from Rural Communities of Venezuela

PURPOSE

Trypanosoma cruzi and Leishmania spp. coexist in several endemic areas, and there are few studies of Chagas disease and leishmaniasis coinfection worldwide; for this reason, the objective of this work was to determine the Chagas disease and leishmaniasis coinfection in several rural communities co-endemic for these diseases.

METHODS

A total of 1107 human samples from six co-endemic rural communities of Cojedes state, Venezuela, were analyzed. Serum samples were evaluated by ELISA, indirect hemagglutination, and indirect immunofluorescence for Chagas disease diagnosis, and individuals were evaluated for leishmaniasis by leishmanin skin test (LST). Approximately, 30% of the individuals were also analyzed by PCR (blood clot samples) for T. cruzi and for Leishmania spp.

RESULTS

The 14.7% of the individuals were positive to Trypanosoma cruzi infection by serology, and 25.8% were positive to Leishmania spp. current or past infection by LST. Among the group with PCR results, 7.8% were positive for T. cruzi, and 9.4% for Leishmania spp. The coinfection T. cruzi/Leishmania spp. was 6.5%. The T. cruzi DTUs of the positive blood clot samples were TcI, revealed using the molecular markers: (i) intergenic region of the miniexon, (ii) D7 divergent domain of the 24Sα rDNA, (iii) size-variable domain of the 18S rDNA, and (iv) hsp60-PCR-RFLP (EcoRV). The Leishmania species identified were L. (Leishmania) mexicana and L. (Viannia) braziliensis.

CONCLUSION

A high prevalence was found for T. cruzi and Leishmania spp. single and coinfections in almost all communities studied, being these results of relevance for the implementation of control programs in co-endemic areas.

Validation of Oxford nanopore sequencing for improved New World Leishmania species identification via analysis of 70-kDA heat shock protein

BACKGROUND

Leishmaniasis is a parasitic disease caused by obligate intracellular protozoa of the genus Leishmania. This infection is characterized by a wide range of clinical manifestations, with symptoms greatly dependent on the causal parasitic species. Here we present the design and application of a new 70-kDa heat shock protein gene (hsp70)-based marker of 771 bp (HSP70-Long). We evaluated its sensitivity, specificity and diagnostic performance employing an amplicon-based MinION™ DNA sequencing assay to identify different Leishmania species in clinical samples from humans and reservoirs with cutaneous leishmaniasis (CL) and visceral leishmaniasis (VL). We also conducted a comparative analysis between our novel marker and a previously published HSP70 marker known as HSP70-Short, which spans 330 bp.

METHODS

A dataset of 27 samples from Colombia, Venezuela and the USA was assembled, of which 26 samples were collected from humans, dogs and cats affected by CL and one sample was collected from a dog with VL in the USA (but originally from Greece). DNA was extracted from each sample and underwent conventional PCR amplification utilizing two distinct HSP70 markers: HSP70-Short and HSP70-Long. The subsequent products were then sequenced using the MinION™ sequencing platform.

RESULTS

The results highlight the distinct characteristics of the newly devised HSP70-Long primer, showcasing the notable specificity of this primer, although its sensitivity is lower than that of the HSP70-Short marker. Notably, both markers demonstrated strong discriminatory capabilities, not only in distinguishing between different species within the Leishmania genus but also in identifying instances of coinfection.

CONCLUSIONS

This study underscores the outstanding specificity and effectiveness of HSP70-based MinION™ sequencing, in successfully discriminating between diverse Leishmania species and identifying coinfection events within samples sourced from leishmaniasis cases.

Parasitological and molecular characterization of Trypanosoma cruzi of triatomines and mammals from endemic areas for Chagas disease in Venezuela

It is estimated that 6-7 million people worldwide are infected with Trypanosoma cruzi, the parasite that causes Chagas disease. In Venezuela, Chagas disease remains a public health problem. In this work, T. cruzi isolates from six species of triatomines and mammals of the orders Didelphimorphia and Xenarthra, captured in rural communities of Monagas, underwent parasitological and molecular characterization. A total of 471 triatomines and 17 mammals were captured, with a natural infection rate of 41.4% and 70.6%, respectively. In the male NMRI mouse model used for parasitological characterization (prepatent period, parasitemia curve, mouse mortality, and tissular parasitism), T. cruzi isolates exhibited high lethality due to their pronounced virulence, irrespective of the parasite load in each mouse, resulting in a mortality rate of 75%. Among the vector isolates, in the mouse model, only 2 out of 6 remained alive, while the rest perished during the evaluation. Conversely, the isolates from mammals proved fatal for all the inoculated mice. All isolates were identified as belonging to DTU TcI, based on the molecular markers such as the intergenic region of the miniexon, D7 divergent domain of the 24Sα rDNA, size-variable domain of the 18S rDNA, and hsp60-PCR-RFLP-EcoRV. This study demonstrates the presence of vectors and mammalian reservoirs naturally infected with T. cruzi in communities of Monagas, the 9th largest and 9th most populous state in Venezuela. This situation represents a neglected epidemiological problem demanding urgent attention and imperative health care intervention.

Trypanosoma cruzi P21 recombinant protein modulates Toxoplasma gondii infection in different experimental models of the human maternal-fetal interface

Introduction

Toxoplasma gondii is the etiologic agent of toxoplasmosis, a disease that affects about one-third of the human population. Most infected individuals are asymptomatic, but severe cases can occur such as in congenital transmission, which can be aggravated in individuals infected with other pathogens, such as HIV-positive pregnant women. However, it is unknown whether infection by other pathogens, such as Trypanosoma cruzi, the etiologic agent of Chagas disease, as well as one of its proteins, P21, could aggravate T. gondii infection.

Methods

In this sense, we aimed to investigate the impact of T. cruzi and recombinant P21 (rP21) on T. gondii infection in BeWo cells and human placental explants.

Results

Our results showed that T. cruzi infection, as well as rP21, increases invasion and decreases intracellular proliferation of T. gondii in BeWo cells. The increase in invasion promoted by rP21 is dependent on its binding to CXCR4 and the actin cytoskeleton polymerization, while the decrease in proliferation is due to an arrest in the S/M phase in the parasite cell cycle, as well as interleukin (IL)-6 upregulation and IL-8 downmodulation. On the other hand, in human placental villi, rP21 can either increase or decrease T. gondii proliferation, whereas T. cruzi infection increases T. gondii proliferation. This increase can be explained by the induction of an anti-inflammatory environment through an increase in IL-4 and a decrease in IL-6, IL-8, macrophage migration inhibitory factor (MIF), and tumor necrosis factor (TNF)-α production.

Discussion

In conclusion, in situations of coinfection, the presence of T. cruzi may favor the congenital transmission of T. gondii, highlighting the importance of neonatal screening for both diseases, as well as the importance of studies with P21 as a future therapeutic target for the treatment of Chagas disease, since it can also favor T. gondii infection.

Molecular identification of Trypanosoma cruzi in domestic animals in municipalities of the State of Rio Grande do Norte, Brazil

Trypanosoma cruzi, the etiologic agent of American trypanosomiasis, is a vector-borne zoonotic parasite which has been little studied regarding its infection in domestic animals. In this study, we evaluated the occurrence of natural infection by T. cruzi in farm animals using molecular markers and phylogenetic analysis in blood clot samples of 60 sheep (Ovis aires), 22 goats (Capra hircus), and 14 horses (Equus caballus) in eight municipalities located in an infection risk area in the state of Rio Grande do Norte (RN), Northeast Region of Brazil. Trypanosoma spp. infection was identified by amplifying the rRNA 18S SSU gene in 48.9% of the samples. The SH022 sample showed 99.8% similarity with the Y strain of T. cruzi in phylogeny, grouped in the DTU II clade. Blood clots of sheep, goats, and horses detected T. cruzi kDNA in 28.3% (17/60), 22.7% (5/22), and 15.4% (2/14) of the samples, respectively. These animals were distributed in the three studied mesoregions throughout the state of RN. The identification of natural infection in domestic animals contributes to expand the epidemiological transmission scenario in an area where T. brasiliensis is the main vector.