Human African trypanosomiasis: the current situation in endemic regions and the risks for non-endemic regions from imported cases

Morphologic and morphometric bilateral analysis and sexual dimorphism in sciatic nerves of adult cadaveric specimens in Uganda

BACKGROUND

The Sciatic nerve (SN) exhibits distinct sex and side-related differences, which have significant implications for clinical practice. The study investigated the sex and side-related morphologic and morphometric variations of the nerve using cadavers.

METHODS

This is a cross-sectional cadaveric study involving 62 Ugandan cadavers. Continuous variables were reported using descriptive statistics and discrete variables were reported as percentages. Ordinary two-way ANOVA was used to compare the dimensions and proportion of the patterns of the SN.

RESULTS

The study identified six categories of exit patterns of the SN, type A ("Below and undivided") occurred in a majority of cases (62.9%). A penta-furcate branching pattern dominated the whole population. Bifurcate termination pattern was found in most SNs (90.3% and 87.1% for right and left limbs respectively) while the rest have the trifurcate termination pattern, with no side or sex-related variations. The average dimensions of SN were within normal ranges, and showed no side-related differences but with a sex difference (significantly higher in males than females), mean length of the SN in centimetres (length A: Males, right limbs = 30.58 ± 9.00; left limbs = 31.30 ± 6.20; Females, right = 26.07 ± 6.58; left = 26.30 ± 5.56). The difference in the length "A" for the males left limb and females right limb was statistically significant with a p-value of 0.0195.

CONCLUSIONS

Most of the examined SNs showed normal anatomical characteristics with rare cases of sex-related dimorphism in the termination level and morphometry (length and diameter) of the nerve. The observed sexual dimorphisms in sciatic nerves are of clinical and surgical interest; hence, suggesting the need for further investigations in different populations, especially using advanced techniques such as ultrasonography anatomic techniques.

Identification of constrained peptidomimetics carrying a Michael acceptor warhead as antitrypanosomal agents

In this structure-activity relationship (SAR) study, we report the development of rhodesain-targeting peptidomimetics with antitrypanosomal activity. The new compounds (SPR65-SPR80) feature the 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic) moiety as conformationally constrained Phe analog. Various substituents were inserted at the P1 and P3 positions, and the methyl vinyl ketone moiety was introduced as warhead. The incorporation of Tic resulted in reduced affinity against rhodesain compared to the parent compounds containing Phe (2a-m), suggesting that its rigidity negatively affects target binding. Nevertheless, promising EC50 values ranging from 0.42 to 1.35 μM were observed in cell-based assays, probably due to better pharmacokinetic properties and/or interactions with additional protozoal targets. CC50 values > 100 μM were observed. Therefore, while Tic is less tolerated by rhodesain, its incorporation in peptidomimetic Michael acceptors led to antitrypanosomal effects that were comparable or slightly better than those of the parent compounds and no cytotoxicity up to 100 μM. These findings could be taken into consideration in future SAR studies aimed at the development of antitrypanosomal agents.

Rhodesain inhibitors on the edge of reversibility-irreversibility

A comparative study of Michael acceptor and keto-Michael acceptor inhibitors of the cysteine protease rhodesain has been performed. Five new inhibitors have been prepared bearing the peptide structure of the known cysteine protease inhibitor K11777 and differing on the warhead. For the preparation of the Michael acceptor warhead, a Horner-Wadsworth-Emmons reaction was used. In the synthetic routes of the keto-Michael acceptor warheads, keto-enoate and keto-vinyl sulfone, a metathesis reaction and a radical sulfonylation were the key steps, respectively. Interestingly, keto-Michael acceptors inhibited rhodesain through a dual mode of action, showing reversibility at low inhibitor concentrations and irreversibility at high inhibitor concentrations.

Drugs for Vector-Borne Protozoal Diseases in a One Health Scenario. A European Perspective

Vector-borne protozoal diseases (VBPD) represent an enormous health and economic burden, particularly in low- and middle-income countries. Their control requires integrated approaches that consider not only therapeutic interventions for affected human and animal populations but also preventive tools. Environmental contamination can lead to therapeutic ineffectiveness. Effective intervention must consider in-depth knowledge of the environmental factors that regulate the exposure, transmission and pathogenicity of VBPD within a One Health approach. In recent decades, the incidence and prevalence of VBPD have been substantially reduced in many regions of the world, although there are still hot spots and emerging epidemiological cycles. Except for a partially protective vaccine against malaria, vaccination is not available for any other human VBPD, and therefore epidemiological control and chemotherapy are the main control tools. Current therapeutics have several drawbacks, including reduced efficacy, toxicity and high price of safer formulations. In addition, the industrial pipeline is limited, and no therapeutic breakthroughs are expected. Integrated control of VBPD requires multitarget control systems adapted to the disease and region. In this scenario, harmonized surveillance systems, accurate reporting and increased public and private investment will ensure more rational use of the few available and new drugs.

The comprehensive epidemiological status of human African trypanosomiasis in Nigeria: meta-analysis and systematic review of the full story (1962-2022)

Human African trypanosomiasis (HAT) in Nigeria is caused primarily by Trypanosoma brucei gambiense (gHAT), which has historically been a major human and animal health problem. This study aims to examine the status of gHAT in Nigeria over the past 60 years. The World Health Organization (WHO) set two targets to eliminate HAT as a public health concern by 2020 and terminate its global transmission by 2030. The former target has been achieved, but accurate monitoring and surveillance are important for maintaining this success and delivering the second target. Although recent cases in Nigeria are rare, accurately estimating the national seroprevalence and actual prevalence of gHATs remains challenging. To address this, a meta-analysis reviewed studies on gHATs in Nigeria from databases such as Embase, Global Health, Ovid Medline, Web of Science, and Google Scholar. Ten studies were included, ranging between 1962 and 2016, covering 52 clusters and 5,671,877 individuals, even though databases were scrutinized up to 2022. The seroprevalence ranged from 1.75 to 17.07%, with an overall estimate of 5.01% (95% CI 1.72-9.93). The actual gHAT prevalence detected by parasitological or PCR methods was 0.001 (95% CI 0.000-0.002), indicating a prevalence of 0.1%. Notably, the seroprevalence was greater in southern Nigeria than in northern Nigeria. These findings suggest that the disease might be spreading unnoticed due to the increased movement of people from endemic areas. This study highlights the paucity of studies in Nigeria over the last 60 years and emphasizes the need for further research, systematic surveillance, and proper reporting methods throughout the country.

Clinical and epidemiological features of imported loiasis in Beijing: a report from patients returned from Africa

BACKGROUND

Loiasis is one of the significant filarial diseases for people living in West and Central Africa with wide endemic area but is not seen in China. As economy booms and international traveling increase, China faces more and more imported parasitic diseases that are not endemic locally. Loiasis is one of the parasitic diseases that enter China by travelers infected in Africa. The better understanding of the clinical and laboratory features of loa loa infection will facilitate the diagnosis and treatment of loiasis in China.

METHODS

The study targeted travelers who were infected with L. loa in endemic Africa regions and returned to Beijing between 2014 and 2023. Epidemiological, clinical, and biological data as well as treatment of these patients were collected.

RESULTS

Total 21 cases were identified as L. loa infection based on their typical clinical manifestations and parasite finding. All cases had a history of travel to Africa for more than 6 months, most of them are the construction workers dispatched to West Africa with outdoor activities. Calabar swelling (n = 19; 90.5%) and pruritus (n = 11; 52.4%) were among the most common clinical symptoms followed by muscle pain (n = 7; 33.3%) and skin rash (n = 2; 9.5%). The adult worms were observed in the eyelid or subconjunctiva (n = 2; 9.5%) and subcutaneous tissues (n = 2; 9.5%). Although all patients presented with a high eosinophil count (> 0.52 × 109/L), only two cases displayed microfilariae in fresh venous blood and positive for filarial antigen. A cut section of adult worm was observed through biopsy on a skin nodule surrounded by lymphocytes, plasma cells and eosinophils. All subjects were positive in PCR targeting L. loa ITS-1. The constructed phylogenetic tree based on the amplified ITS-1 sequences identified their genetical relation to the L. Loa from Africa. All patients treated with albendazole and diethylcarbamazine were recovered without relapse.

CONCLUSION

This study provides useful information and guideline for physicians and researchers in non-endemic countries to diagnose and treat loiasis and L. loa infections acquired from endemic regions.

Tractable Quinolone Hydrazides Exhibiting Sub-Micromolar and Broad Spectrum Antitrypanosomal Activities

Nagana and Human African Trypanosomiasis (HAT), caused by (sub)species of Trypanosoma, are diseases that impede human and animal health, and economic growth in Africa. The few drugs available have drawbacks including suboptimal efficacy, adverse effects, drug resistance, and difficult routes of administration. New drugs are needed. A series of 20 novel quinolone compounds with affordable synthetic routes was made and evaluated in vitro against Trypanosoma brucei and HEK293 cells. Of the 20 compounds, 12 had sub-micromolar potencies against the parasite (EC50 values=0.051-0.57 μM), and most were non-toxic to HEK293 cells (CC50 values>5 μM). Two of the most potent compounds presented sub-micromolar activities against other trypanosome (sub)species (T. cruzi and T. b. rhodesiense). Although aqueous solubility is poor, both compounds possess good logD values (2-3), and either robust or poor microsomal stability profiles. These varying attributes will be addressed in future reports.

Q586B2 is a crucial virulence factor during the early stages of Trypanosoma brucei infection that is conserved amongst trypanosomatids

Human African trypanosomiasis or sleeping sickness, caused by the protozoan parasite Trypanosoma brucei, is characterized by the manipulation of the host's immune response to ensure parasite invasion and persistence. Uncovering key molecules that support parasite establishment is a prerequisite to interfere with this process. We identified Q586B2 as a T. brucei protein that induces IL-10 in myeloid cells, which promotes parasite infection invasiveness. Q586B2 is expressed during all T. brucei life stages and is conserved in all Trypanosomatidae. Deleting the Q586B2-encoding Tb927.6.4140 gene in T. brucei results in a decreased peak parasitemia and prolonged survival, without affecting parasite fitness in vitro, yet promoting short stumpy differentiation in vivo. Accordingly, neutralization of Q586B2 with newly generated nanobodies could hamper myeloid-derived IL-10 production and reduce parasitemia. In addition, immunization with Q586B2 delays mortality upon a challenge with various trypanosomes, including Trypanosoma cruzi. Collectively, we uncovered a conserved protein playing an important regulatory role in Trypanosomatid infection establishment.

Polyamine Metabolism for Drug Intervention in Trypanosomatids

Neglected tropical diseases transmitted by trypanosomatids include three major human scourges that globally affect the world's poorest people: African trypanosomiasis or sleeping sickness, American trypanosomiasis or Chagas disease and different types of leishmaniasis. Different metabolic pathways have been targeted to find antitrypanosomatid drugs, including polyamine metabolism. Since their discovery, the naturally occurring polyamines, putrescine, spermidine and spermine, have been considered important metabolites involved in cell growth. With a complex metabolism involving biosynthesis, catabolism and interconversion, the synthesis of putrescine and spermidine was targeted by thousands of compounds in an effort to produce cell growth blockade in tumor and infectious processes with limited success. However, the discovery of eflornithine (DFMO) as a curative drug against sleeping sickness encouraged researchers to develop new molecules against these diseases. Polyamine synthesis inhibitors have also provided insight into the peculiarities of this pathway between the host and the parasite, and also among different trypanosomatid species, thus allowing the search for new specific chemical entities aimed to treat these diseases and leading to the investigation of target-based scaffolds. The main molecular targets include the enzymes involved in polyamine biosynthesis (ornithine decarboxylase, S-adenosylmethionine decarboxylase and spermidine synthase), enzymes participating in their uptake from the environment, and the enzymes involved in the redox balance of the parasite. In this review, we summarize the research behind polyamine-based treatments, the current trends, and the main challenges in this field.

Targeting Cysteine Proteases and their Inhibitors to Combat Trypanosomiasis

BACKGROUND

Trypanosomiasis, caused by protozoan parasites of the Trypanosoma genus, remains a significant health burden in several regions of the world. Cysteine proteases play a crucial role in the pathogenesis of Trypanosoma parasites and have emerged as potential therapeutic targets for the development of novel antiparasitic drugs.

INTRODUCTION

This review article aims to provide a comprehensive overview of the role of cysteine proteases in trypanosomiasis and their potential as therapeutic targets. We discuss the biological significance of cysteine proteases in Trypanosoma parasites and their involvement in essential processes, such as host immune evasion, cell invasion, and nutrient acquisition.

METHODS

A comprehensive literature search was conducted to identify relevant studies and research articles on the role of cysteine proteases and their inhibitors in trypanosomiasis. The selected studies were critically analyzed to extract key findings and provide a comprehensive overview of the topic.

RESULTS

Cysteine proteases, such as cruzipain, TbCatB and TbCatL, have been identified as promising therapeutic targets due to their essential roles in Trypanosoma pathogenesis. Several small molecule inhibitors and peptidomimetics have been developed to target these proteases and have shown promising activity in preclinical studies.

CONCLUSION

Targeting cysteine proteases and their inhibitors holds great potential for the development of novel antiparasitic drugs against trypanosomiasis. The identification of potent and selective cysteine protease inhibitors could significantly contribute to the combat against trypanosomiasis and improve the prospects for the treatment of this neglected tropical disease.

Human African Trypanosomiasis (Sleeping Sickness)-Epidemiology, Clinical Manifestations, Diagnosis, Treatment, and Prevention

Purpose of Review

Human African Trypanosomiasis (HAT), also known as sleeping sickness, is a vector-borne parasitic neglected tropical disease (NTD) endemic in sub-Saharan Africa. This review aims to enhance our understanding of HAT and provide valuable insights to combat this significant public health issue by synthesizing the latest research and evidence.

Recent Findings

HAT has reached a historical < 1000 cases in 2018. In patients without neurologic symptoms and signs, the likelihood of a severe meningoencephalitic stage is deemed low, obviating the need for a lumbar puncture to guide treatment decisions using fexinidazole.

Summary

Both forms of the disease, gambiense HAT (gHAT) and rhodesiense HAT (rHAT), have specific epidemiology, risk factors, diagnosis, and treatment. Disease management still requires a high index of suspicion, infectious disease expertise, and specialized medical care. Essential stakeholders in health policy are critical to accomplishing the elimination goals of the NTD roadmap for 2021-2030.

Design, synthesis and biological evaluation of antiparasitic dinitroaniline-ether phospholipid hybrids

A series of nine novel ether phospholipid-dinitroaniline hybrids were synthesized in an effort to deliver more potent antiparasitic agents with improved safety profile compared to miltefosine. The compounds were evaluated for their in vitro antiparasitic activity against L. infantum, L.donovani, L. amazonensis, L. major and L. tropica promastigotes, L. infantum and L. donovani intracellular amastigotes, Trypanosoma brucei brucei and against different developmental stages of Trypanosoma cruzi. The nature of the oligomethylene spacer between the dinitroaniline moiety and the phosphate group, the length of the side chain substituent on the dinitroaniline and the choline or homocholine head group were found to affect both the activity and toxicity of the hybrids. The early ADMET profile of the derivatives did not reveal major liabilities. Hybrid 3, bearing an 11-carbon oligomethylene spacer, a butyl side chain and a choline head group, was the most potent analogue of the series. It exhibited a broad spectrum antiparasitic profile against the promastigotes of New and Old World Leishmania spp., against intracellular amastigotes of two L. infantum strains and L. donovani, against T. brucei and against T. cruzi Y strain epimastigotes, intracellular amastigotes and trypomastigotes. The early toxicity studies revealed that hybrid 3 showed a safe toxicological profile while its cytotoxicity concentration (CC50) against THP-1 macrophages being >100 μM. Computational analysis of binding sites and docking indicated that the interaction of hybrid 3 with trypanosomatid α-tubulin may contribute to its mechanism of action. Furthermore, compound 3 was found to interfere with the cell cycle in T. cruzi epimastigotes, while ultrastructural studies using SEM and TEM in T. cruzi showed that compound 3 affects cellular processes that result in changes in the Golgi complex, the mitochondria and the parasite's plasma membrane. The snapshot pharmacokinetic studies showed low levels of 3 after 24 h following oral administration of 100 mg/Kg, while, its homocholine congener compound 9 presented a better pharmacokinetic profile.

Novel Lipophilic Hydroxamates Based on Spirocarbocyclic Hydantoin Scaffolds with Potent Antiviral and Trypanocidal Activity

Flaviviridae infections, such as those caused by hepatitis C (HCV) and dengue viruses (DENVs), represent global health risks. Infected people are in danger of developing chronic liver failure or hemorrhagic fever, both of which can be fatal if not treated. The tropical parasites Trypanosoma brucei and Trypanosoma cruzi cause enormous socioeconomic burdens in Sub-Saharan Africa and Latin America. Anti-HCV chemotherapy has severe adverse effects and is expensive, whereas dengue has no clinically authorized treatment. Antiparasitic medicines are often toxic and difficult to administer, and treatment failures are widely reported. There is an urgent need for new chemotherapies. Based on our previous research, we have undertaken structural modification of lead compound V with the goal of producing derivatives with both antiviral and trypanocidal activity. The novel spirocarbocyclic-substituted hydantoin analogs were designed, synthesized, and tested for antiviral activity against three HCV genotypes (1b, 3a, 4a), DENV, yellow fever virus (YFV), and two trypanosome species (T. brucei, T. cruzi). The optimization was successful and led to compounds with significant antiviral and trypanocidal activity and exceptional selectivity. Several modifications were made to further investigate the structure-activity relationships (SARs) and confirm the critical role of lipophilicity and conformational degrees of freedom.

Influence of amino acid size at the P3 position of N-Cbz-tripeptide Michael acceptors targeting falcipain-2 and rhodesain for the treatment of malaria and human african trypanosomiasis

In recent decades, several structure-activity relationship (SAR) studies provided potent inhibitors of the cysteine proteases falcipain-2 (FP-2) and rhodesain (RD) from Plasmodium falciparum and Trypanosoma brucei rhodesiense, respectively. Whilst the roles of the warhead and residues targeting the P1 and P2 pockets of the proteases were extensively investigated, the roles of the amino acids occupying the S3 pocket were not widely assessed. Herein we report the synthesis and biological evaluation of a set of novel Michael acceptors bearing amino acids of increasing size at the P3 site (1a-g/2a-g, SPR20-SPR33) against FP-2, RD, P. falciparum, and T. brucei. Overall, the Michael acceptors bearing small amino acids at the P3 site exhibited the most potent inhibitory properties towards FP-2. In contrast, analogues with bulky residues at the P3 position were very potent rhodesain inhibitors. In cell based assays, single-digit micromolar EC₅₀ values against the two protozoa were observed. These findings can be a starting point for the development of peptide-based FP-2 and RD inhibitors.

Antimicrobial Peptides (AMPs): Potential Therapeutic Strategy against Trypanosomiases?

Trypanosomiases are a group of tropical diseases that have devastating health and socio-economic effects worldwide. In humans, these diseases are caused by the pathogenic kinetoplastids Trypanosoma brucei, causing African trypanosomiasis or sleeping sickness, and Trypanosoma cruzi, causing American trypanosomiasis or Chagas disease. Currently, these diseases lack effective treatment. This is attributed to the high toxicity and limited trypanocidal activity of registered drugs, as well as resistance development and difficulties in their administration. All this has prompted the search for new compounds that can serve as the basis for the development of treatment of these diseases. Antimicrobial peptides (AMPs) are small peptides synthesized by both prokaryotes and (unicellular and multicellular) eukaryotes, where they fulfill functions related to competition strategy with other organisms and immune defense. These AMPs can bind and induce perturbation in cell membranes, leading to permeation of molecules, alteration of morphology, disruption of cellular homeostasis, and activation of cell death. These peptides have activity against various pathogenic microorganisms, including parasitic protists. Therefore, they are being considered for new therapeutic strategies to treat some parasitic diseases. In this review, we analyze AMPs as therapeutic alternatives for the treatment of trypanosomiases, emphasizing their possible application as possible candidates for the development of future natural anti-trypanosome drugs.

Modular nanotheranostic agents for protistan parasitic diseases: Magic bullets with tracers

Protistan parasitic infections contribute significantly to morbidity and mortality, causing more than 2 billion human infections annually. However, current treatments are often limited; due to ineffective drugs and drug resistance, thus better options are urgently required. In the present context, theranostics agents are those that offer simultaneous detection, diagnosis and even treatment of protistan parasitic diseases. "Nanotheranostics" is the term used to describe such agents, that are around 100 nm or less in size. Anti-parasitic activity of nanoparticles (NPs) has been reported, and many have useful intrinsic imaging properties, but it is perhaps their multifunctional nature that offers the greatest potential. NPs may be used as adapters onto which various subunits with different functions may be attached. These subunits may facilitate targeting parasites, coupled with toxins to eradicate parasites, and probe subunits for detection of particles and/or parasites. The modular nature of nano-platforms promises a "mix and match" approach for the construction of tailored agents by using combinations of these subunits against different protistan parasites. Even though many of the subunits have shown promise alone, these have not yet been put together convincingly enough to form working theranostics against protistan parasites. Although the clinical application of nanotheranostics to protistan parasitic infections in humans requires more research, we conclude that they offer not just a realisation of Paul Ehrlich's long imagined "magic bullet" concept, but potentially are magic bullets combined with tracer bullets.

Mode of action of p-quinone derivatives with trypanocidal activity studied by experimental and in silico models

Quinones are attractive pharmacological scaffolds for developing new agents for the treatment of different transmissible and non-transmissible human diseases due to their capacity to alter the cell redox homeostasis. The bioactivity and potential mode of action of 19 p-quinone derivatives fused to different aromatic rings (carbo or heterocycles) and harboring distinct substituents were investigated in infective Trypanosoma brucei brucei. All the compounds, except for a furanequinone (EC₅₀₌38 μM), proved to be similarly or even more potent (EC₅₀ = 0.5-5.5 μM) than the clinical drug nifurtimox (EC₅₀ = 5.3 μM). Three furanequinones and one thiazolequinone displayed a higher selectivity than nifurtimox. Two of these selective hits resulted potent inhibitors of T. cruzi proliferation (EC₅₀₌0.8-1.1 μM) but proved inactive against Leishmania infantum amastigotes. Most of the p-quinones induced a rapid and marked intracellular oxidation in T. b. brucei. DFT calculations on the oxidized quinone (Q), semiquinone (Q^•-) and hydroquinone (QH₂) suggest that all quinones have negative ΔG for the formation of Q^•-. Qualitative and quantitative structure-activity relationship analyses in two or three dimensions of different electronic and biophysical descriptors of quinones and their corresponding bioactivities (killing potency and oxidative capacity) were performed. Charge distribution over the quinone ring carbons of Q and Q^.- and the frontier orbitals energies of SUMO (Q^.-) and LUMO (Q) correlate with their oxidative and trypanocidal activity. QSAR analysis also highlighted that both bromine substitution in the p-quinone ring and a bulky phenyl group attached to the furane and thiazole rings (which generates a negative charge due to the π electron system polarized by the nearby heteroatoms) are favorable for activity. By combining experimental and in silico procedures, this study disclosed important information about p-quinones that may help to rationally tune their electronic properties and biological activities.

Kaempferol: Antimicrobial Properties, Sources, Clinical, and Traditional Applications

Flavonoids are a category of plant-derived compounds which exhibit a large number of health-related effects. One of the most well-known and studied flavonoids is kaempferol, which can be found in a wide variety of herbs and plant families. Apart from their anticarcinogenic and anti-inflammatory effects, kaempferol and its associated compounds also exhibit antibacterial, antifungal, and antiprotozoal activities. The development of drugs and treatment schemes based on these compounds is becoming increasingly important in the face of emerging resistance of numerous pathogens as well as complex molecular interactions between various drug therapies. In addition, many of the kaempferol-containing plants are used in traditional systems all over the world for centuries to treat numerous conditions. Due to its variety of sources and associated compounds, some molecular mechanisms of kaempferol antimicrobial activity are well known while others are still under analysis. This paper thoroughly documents the vegetal and food sources of kaempferol as well as the most recent and significant studies regarding its antimicrobial applications.

Human African trypanosomiasis cases diagnosed in non-endemic countries (2011-2020)

BACKGROUND

Sleeping sickness, or human African trypanosomiasis (HAT), is transmitted by tsetse flies in endemic foci in sub-Saharan Africa. Because of international travel and population movements, cases are also occasionally diagnosed in non-endemic countries.

METHODOLOGY/PRINCIPAL FINDINGS

Antitrypanosomal medicines to treat the disease are available gratis through the World Health Organization (WHO) thanks to a public-private partnership, and exclusive distribution of the majority of them enables WHO to gather information on all exported cases. Data collected by WHO are complemented by case reports and scientific publications. During 2011-2020, 49 cases of HAT were diagnosed in 16 non-endemic countries across five continents: 35 cases were caused by Trypanosoma brucei rhodesiense, mainly in tourists visiting wildlife areas in eastern and southern Africa, and 14 cases were due to T. b. gambiense, mainly in African migrants originating from or visiting endemic areas in western and central Africa.

CONCLUSIONS/SIGNIFICANCE

HAT diagnosis in non-endemic countries is rare and can be challenging, but alertness and surveillance must be maintained to contribute to WHO's elimination goals. Early detection is particularly important as it considerably improves the prognosis.

Development of Urea-Bond-Containing Michael Acceptors as Antitrypanosomal Agents Targeting Rhodesain

Human African Trypanosomiasis (HAT) is a neglected tropical disease widespread in sub-Saharan Africa. Rhodesain, a cysteine protease of Trypanosoma brucei rhodesiense, has been identified as a valid target for the development of anti-HAT agents. Herein, we report a series of urea-bond-containing Michael acceptors, which were demonstrated to be potent rhodesain inhibitors with K_i values ranging from 0.15 to 2.51 nM, and five of them showed comparable k_2nd values to that of K11777, a potent antitrypanosomal agent. Moreover, most of the urea derivatives exhibited single-digit micromolar activity against the protozoa, and the presence of substituents at the P3 position appears to be essential for the antitrypanosomal effect. Replacement of Phe with Leu at the P2 site kept unchanged the inhibitory properties. Compound 7 (SPR7) showed the best compromise in terms of rhodesain inhibition, selectivity, and antiparasitic activity, thus representing a new lead compound for future SAR studies.

Discovery of novel natural products as rhodesain inhibitors for human African trypanosomiasis using in silico techniques

Human African Trypanosomiasis (HAT) or sleeping sickness is caused by the Trypanosoma brucei rhodesiense, a subspecies of the Trypanosomatide family. The parasite is associated with high morbidity and mortality rate in both animals and humans, claimed to be more fatal than other vector-transmitted diseases such as malaria. The majority of existing medications are highly toxic, not effective in the late chronic phase of the disease, and require maximum dosages to fully eradicate the parasite. In this study, we used computational methods to find out natural products that inhibit the Rhodesain, a parasitic enzyme that plays an important role in the parasite's pathogenicity, multiplication, and ability to pass through the host's blood-brain barrier. A library of 270540 natural products from ZINC databases was processed by using e-pharmacophore hypnosis and screening procedures, molecular docking, ADMET processes, and MM-GBSA calculations. This led to the identification of 3 compounds (ZINC000096269390, ZINC000035485292, and ZINC000035485242) which were then subjected to molecular dynamics. The findings of this study showed excellent binding affinity and stability toward the Rhodesain and suggest they may be a hopeful treatment for HAT in the future if further clinical trials were performed.Communicated by Ramaswamy H. Sarma.

Development of Reduced Peptide Bond Pseudopeptide Michael Acceptors for the Treatment of Human African Trypanosomiasis

Human African Trypanosomiasis (HAT) is an endemic protozoan disease widespread in the sub-Saharan region that is caused by T. b. gambiense and T. b. rhodesiense. The development of molecules targeting rhodesain, the main cysteine protease of T. b. rhodesiense, has led to a panel of inhibitors endowed with micro/sub-micromolar activity towards the protozoa. However, whilst impressive binding affinity against rhodesain has been observed, the limited selectivity towards the target still remains a hard challenge for the development of antitrypanosomal agents. In this paper, we report the synthesis, biological evaluation, as well as docking studies of a series of reduced peptide bond pseudopeptide Michael acceptors (SPR10-SPR19) as potential anti-HAT agents. The new molecules show Ki values in the low-micro/sub-micromolar range against rhodesain, coupled with k2nd values between 1314 and 6950 M-1 min-1. With a few exceptions, an appreciable selectivity over human cathepsin L was observed. In in vitro assays against T. b. brucei cultures, SPR16 and SPR18 exhibited single-digit micromolar activity against the protozoa, comparable to those reported for very potent rhodesain inhibitors, while no significant cytotoxicity up to 70 µM towards mammalian cells was observed. The discrepancy between rhodesain inhibition and the antitrypanosomal effect could suggest additional mechanisms of action. The biological characterization of peptide inhibitor SPR34 highlights the essential role played by the reduced bond for the antitrypanosomal effect. Overall, this series of molecules could represent the starting point for further investigations of reduced peptide bond-containing analogs as potential anti-HAT agents.

Atypical human trypanosomosis: Potentially emerging disease with lack of understanding

Trypanosomes are the hemoflagellate kinetoplastid protozoan parasites affecting a wide range of vertebrate hosts having insufficient host specificity. Climatic change, deforestation, globalization, trade agreements, close association and genetic selection in links with environmental, vector, reservoir and potential susceptible hosts' parameters have led to emergence of atypical human trypanosomosis (a-HT). Poor recording of such neglected tropical disease, low awareness in health professions and farming community has approached a serious intimidation for mankind. Reports of animal Trypanosoma species are now gradually increasing in humans, and lack of any compiled literature has diluted the issue. In the present review, global reports of livestock and rodent trypanosomes reported from human beings are assembled and discrepancies with the available literature are discussed along with morphological features of Trypanosoma species. We have described 21 human cases from the published information. Majority of cases 10 (47%) are due to T. lewisi, followed by 5 (24%) cases of T. evansi, 4 (19%) cases of T. brucei and 1 (5%) case each of T. vivax and T. congolense. Indian subcontinent witnessed 13 cases of a-HT, of which 9 cases are reported from India, which includes 7 cases of T. lewisi and 2 cases of T. evansi. Apart from, a-HT case reports, epidemiological investigation and treatment aspects are also discussed. An attempt has been made to provide an overview of the current situation of atypical human trypanosomosis caused by salivarian animal Trypanosoma globally. The probable role of Trypanosoma lytic factors (TLF) present in normal human serum (NHS) in providing innate immunity against salivarian animal Trypanosoma species and the existing paradox in medical science after the finding on intact functional apolipoprotein L1 (ApoL1) in Vietnam T. evansi Type A case is also discussed to provide an update on all aspects of a-HT. Insufficient data and poor reporting in Asian and African countries are the major hurdle resulting in under-reporting of a-HT, which is a potential emerging threat. Therefore, concerted efforts must be directed to address attentiveness, preparedness and regular surveillance in suspected areas with training of field technicians, medical health professionals and veterinarians. Enhancing a one health approach is specifically important in case of trypanosomosis.

Plasma Neuron-Specific Enolase is not a reliable biomarker for staging Trypanosoma brucei rhodesiense sleeping sickness patients

Objective

Currently, the only available staging criterion for T. b. rhodesiense requires a lumber puncture to collect and later examine cerebrospinal fluid (CSF). This study examined the potential of plasma Neuron-Specific Enolase (NSE) in discriminating between early and late-stage patients.

Results

When median NSE levels were compared between early and late-stage patients, results showed a significant (P < 0.02) upregulation among late-stage patients (599.8 ng/mL). No significant differences (P > 0.9) in NSE levels were observed between early-stage patients (300 ng/mL) and controls (454 ng/mL). We used Receiver Operator Characteristic (ROC) curves to explore the likelihood of using plasma NSE as a potential stage biomarker in discriminating between early and late-stage HAT patients. Our results showed that NSE demonstrated an area under the curve (AUC) of 0.702 (95% CI 0.583–0.830). A high staging accuracy for NSE was obtained by using a cutoff of > 346.5 ng/mL with a sensitivity of 68.6% (95% CI 55–79.7%) and a specificity of 93.3% (95% CI 70.2–99.7%). Although our results demonstrate that plasma NSE is upregulated in T. b. rhodesiense sleeping sickness patients, its value in discriminating between late and early-stage patients is limited. However, future studies could consider improving its specificity by combining it with other identified plasma biomarkers.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-022-05981-w.

A review on the diagnosis of animal trypanosomoses

This review focuses on the most reliable and up-to-date methods for diagnosing trypanosomoses, a group of diseases of wild and domestic mammals, caused by trypanosomes, parasitic zooflagellate protozoans mainly transmitted by insects. In Africa, the Americas and Asia, these diseases, which in some cases affect humans, result in significant illness in animals and cause major economic losses in livestock. A number of pathogens are described in this review, including several Salivarian trypanosomes, such as Trypanosoma brucei sspp. (among which are the agents of sleeping sickness, the human African trypanosomiasis [HAT]), Trypanosoma congolense and Trypanosoma vivax (causing “Nagana” or animal African trypanosomosis [AAT]), Trypanosoma evansi (“Surra”) and Trypanosoma equiperdum (“Dourine”), and Trypanosoma cruzi, a Stercorarian trypanosome, etiological agent of the American trypanosomiasis (Chagas disease). Diagnostic methods for detecting zoonotic trypanosomes causing Chagas disease and HAT in animals, as well as a diagnostic method for detecting animal trypanosomes in humans (the so-called “atypical human infections by animal trypanosomes” [a-HT]), including T. evansi and Trypanosoma lewisi (a rat parasite), are also reviewed. Our goal is to present an integrated view of the various diagnostic methods and techniques, including those for: (i) parasite detection; (ii) DNA detection; and (iii) antibody detection. The discussion covers various other factors that need to be considered, such as the sensitivity and specificity of the various diagnostic methods, critical cross-reactions that may be expected among Trypanosomatidae, additional complementary information, such as clinical observations and epizootiological context, scale of study and logistic and cost constraints. The suitability of examining multiple specimens and samples using several techniques is discussed, as well as risks to technicians, in the context of specific geographical regions and settings. This overview also addresses the challenge of diagnosing mixed infections with different Trypanosoma species and/or kinetoplastid parasites. Improving and strengthening procedures for diagnosing animal trypanosomoses throughout the world will result in a better control of infections and will significantly impact on “One Health,” by advancing and preserving animal, human and environmental health.

The Occurrence of Malignancy in Trypanosoma brucei brucei by Rapid Passage in Mice

Pleomorphic Trypanosoma brucei are best known for their tightly controlled cell growth and developmental program, which ensures their transmissibility and host fitness between the mammalian host and insect vector. However, after long-term adaptation in the laboratory or by natural evolution, monomorphic parasites can be derived. The origin of these monomorphic forms is currently unclear. Here, we produced a series of monomorphic trypanosome stocks by artificially syringe-passage in mice, creating snapshots of the transition from pleomorphism to monomorphism. We then compared these artificial monomorphic trypanosomes, alongside several naturally monomorphic T. evansi and T. equiperdum strains, with the pleomorphic T. brucei. In addition to failing to generate stumpy forms in animal bloodstream, we found that monomorphic trypanosomes from laboratory and nature exhibited distinct differentiation patterns, which are reflected by their distinct differentiation potential and transcriptional changes. Lab-adapted monomorphic trypanosomes could still be induced to differentiate, and showed only minor transcriptional differences to that of the pleomorphic slender forms but some accumulated differences were observed as the passages progress. All naturally monomorphic strains completely fail to differentiate, corresponding to their impaired differentiation regulation. We propose that the natural phenomenon of trypanosomal monomorphism is actually a malignant manifestation of protozoal cells. From a disease epidemiological and evolutionary perspective, our results provide evidence for a new way of thinking about the origin of these naturally monomorphic strains, the malignant evolution of trypanosomes may raise some concerns. Additionally, these monomorphic trypanosomes may reflect the quantitative and qualitative changes in the malignant evolution of T. brucei, suggesting that single-celled protozoa may also provide the most primitive model of cellular malignancy, which could be a primitive and inherent biological phenomenon of eukaryotic organisms from protozoans to mammals.

Discovery, Development, Inventions and Patent Review of Fexinidazole: The First All-Oral Therapy for Human African Trypanosomiasis

Human African trypanosomiasis (HAT or 'sleeping sickness') is a neglected tropical disease. If untreated, it is always fatal and leads to death. A few treatments are available for HAT, but most of them require a skilled professional, which increases the financial burden on the patient. Recently, fexinidazole (FEX) has been approved by the European Medicine Agency (EMA) and the United States Food and Drug Administration (USFDA) as the first all-oral therapy for the treatment of stage-1 (hemolymphatic) as well as stage-2 (meningoencephalitic) of HAT. Before the FEX approval, there were separate treatments for stage-1 and stage-2 of HAT. This study reviews the discovery, development timeline, inventions, and patent literature of FEX. It was first approved by EMA and USFDA in 2018 and 2021, respectively. FEX was also added to the World Health Organization's list of essential drugs in 2019. The patent literature search revealed many types of patents/patent applications (compound, salt, process, method of treatment, drug combinations, and compositions) related to FEX, which have been summarized in this article. The authors foresee a great scope to develop more inventions based on FEX (novel salts, polymorphs, drug conjugates, cyclodextrin complex, etc.) for the treatment of many protozoal diseases (Leishmaniasis and Chagas disease), inflammatory diseases, and other microbial infections. New combinations of FEX with other treatments of HAT may also provide fruitful results. This review might be useful to the scientists working on the HAT and other neglected diseases to develop novel inventions and innovations of therapeutic relevance.

Autochthonous Trypanosoma spp. in European Mammals: A Brief Journey amongst the Neglected Trypanosomes

The genus Trypanosoma includes flagellated protozoa belonging to the family Trypanosomatidae (Euglenozoa, Kinetoplastida) that can infect humans and several animal species. The most studied species are those causing severe human pathology, such as Chagas disease in South and Central America, and the human African trypanosomiasis (HAT), or infections highly affecting animal health, such as nagana in Africa and surra with a wider geographical distribution. The presence of these Trypanosoma species in Europe has been thus far linked only to travel/immigration history of the human patients or introduction of infected animals. On the contrary, little is known about the epidemiological status of trypanosomes endemically infecting mammals in Europe, such as Trypanosomatheileri in ruminants and Trypanosomalewisi in rodents and other sporadically reported species. This brief review provides an updated collection of scientific data on the presence of autochthonous Trypanosoma spp. in mammals on the European territory, in order to support epidemiological and diagnostic studies on Trypanosomatid parasites.

Funding for Chagas Disease: A 10-Year (2009-2018) Survey

Chagas disease was discovered in 1909 by the Brazilian scientist Carlos Chagas. After more than 110 years, many outcomes have been achieved in all research fields; however, Chagas disease remains a serious public health problem, mainly in Latin America, being one of the most neglected tropical diseases in the world. As a neglected disease, it receives very little financial support. Nevertheless, how much is actually spent? With this question in mind, the goal of the present work was to summarize all funding employed by multiple institutions in the Chagas disease field in a 10-year survey. From 2009 to 2018, Chagas disease received only USD 236.31 million, representing 0.67% of the total applied for all neglected diseases in this period. Mostly, the investments are concentrated in basic research (47%) and drug development (42.5%), with the public sector responsible for 74% of all funding, followed by the industry (19%) and philanthropy (7%). Relevantly, NIH (USA) alone accounted for more than half of the total investment. Taking into account that Chagas disease has a great socio-economic impact, it is clear that more investments are needed, especially from endemic countries. Furthermore, coordinated strategies to make better use of resources and incentives for the pharmaceutical industry must be adopted.