Peroxiredoxins from Trypanosoma cruzi: virulence factors and drug targets for treatment of Chagas disease?

Cytosolic and mitochondrial Trypanosoma cruzi tryparedoxin peroxidases belong to the family of 2-Cys peroxiredoxins. These enzymes play an essential role as antioxidants by their peroxidase and peroxynitrite reductase activities. TXNPx are key components of the trypanosomatid peroxide detoxification pathways. The aim of this work was to determine the role of TXNPx as virulence factors in the parasite, and whether these enzymes are good candidates for drug design. We observed that peroxiredoxins are not highly abundant proteins expressed at similar levels throughout the T. cruzi life cycle. In order to study the role of c-TXNPx and m-TXNPx in invasion and infectivity, parasites overexpressing TXNPx were produced, and infection experiments were carried out using phagocytic and non-phagocytic cells. Parasites overexpressing peroxiredoxins showed a significant increase in infectivity with respect to the control ones. The results presented in this work point out that the T. cruzi peroxiredoxins are important in survival, replication and differentiation of T. cruzi and could constitute virulence factors. Moreover, their expression in the infective forms of the life cycle and their low intracellular concentration make them good candidates to become targets for drug design.     

Pre-Columbian Chagas disease in Brazil: Trypanosoma cruzi I in the archaeological remains of a human in Peruaçu Valley, Minas Gerais, Brazil

We evaluated the presence and distribution of Trypanosoma cruzi DNA in a mummy presenting with megacolon that was dated as approximately 560 +/- 40 years old. The mummy was from the Perua?u Valley in the state of Minas Gerais, Brazil. All samples were positive for T. cruzi minicircle DNA, demonstrating the presence and broad dissemination of the parasite in this body. From one sample, a mini-exon gene fragment was recovered and characterized by sequencing and was found to belong to the T. cruzi I genotype. This finding suggests that T. cruzi I infected humans during the pre-Columbian times and that, in addition to T. cruzi infection, Chagas disease in Brazil most likely preceded European colonization.     

Trypanosoma cruzi infection of human induced pluripotent stem cell-derived cardiomyocytes: an in vitro model for drug screening for Chagas disease

Chagas disease, caused by Trypanosoma cruzi, is an important global public health problem which, despite partial efficacy of benznidazole (Bz) in acute phase, urgently needs an effective treatment. Cardiotoxicity is a major safety concern for conduction of more accurate preclinical drug screening platforms. Human induced pluripotent stem cells derived cardiomyocytes (hiPSC-CM) are a reliable model to study genetic and infectious cardiac alterations and may improve drug development. Herein, we introduce hiPSC-CM as a suitable model to study T. cruzi heart infection and to predict the safety and efficacy of anti-T. cruzi drugs.     

Models of human genetic disease: how biased are the standard formulae?

Standard theory provides a simple prediction for the frequency of a recessive lethal allele conferring heterozygous protection against an infectious disease (the best-known example being sickle cell protection against malaria). This relationship allows historic disease mortality rates to be estimated. There are, however, hidden biases in this approach. Reproductively active human females in archaic societies normally produce children at intervals of around 4 years. If death of the fetus or young infant (less than around 3 years of age) occurs, then the mother re-enters oestrus and produces another child. This 'reproductive compensation' reduces selection against the agent causing early mortality (the recessive allele or infective agent) and biases our estimates of historic mortality rates. The magnitude of these biases is investigated. Re-conception also constitutes a demographic selective pressure acting alongside natural selection: lethal genetic diseases (or tightly linked loci) will be selected to become ever more virulent, killing at ever decreasing ages, to allow the mother to re-enter oestrus and re-conceive a (hopefully unaffected) sibling; this effect also invalidates statistical tests using the number of alleles to distinguish overdominance from drift as explanations for high allele frequency. The same bias affects calculations of mutation/selection balance: for any given mutation rate, syndromes which kill early in life will reach much higher frequencies than those killing at later ages. An intriguing consequence is that lethal recessive disorders in humans will increase in frequency by up to 45% as a consequence of the recent demographic transition to planned family size.     

From bench to bed: the potential of stem cells for the treatment of Parkinson’s disease

Parkinson’s disease (PD) is the most common movement disorder. The neuropathology is characterized by the loss of dopamine neurons in the substantia nigra pars compacta. Transplants of fetal/embryonic midbrain tissue have exhibited some beneficial clinical effects in open-label trials. Neural grafting has, however, not become a standard treatment for several reasons. First, the supply of donor cells is limited, and therefore, surgery is accompanied by difficult logistics. Second, the extent of beneficial effects has varied in a partly unpredictable manner. Third, some patients have exhibited graft-related side effects in the form of involuntary movements. Fourth, in two major double-blind placebo-controlled trials, there was no effect of the transplants on the primary endpoints. Nevertheless, neural transplantation continues to receive a great deal of interest, and now, attention is shifting to the idea of using stem cells as starting donor material. In the context of stem cell therapy for PD, stem cells can be divided into three categories: neural stem cells, embryonic stem cells, and other tissue-specific types of stem cells, e.g., bone marrow stem cells. Each type of stem cell is associated with advantages and disadvantages. In this article, we review recent advances of stem cell research of direct relevance to clinical application in PD and highlight the pros and cons of the different sources of cells. We draw special attention to some key problems that face the translation of stem cell technology into the clinical arena.     

Targeting the polyamine biosynthetic enzymes: a promising approach to therapy of African sleeping sickness, Chagas’ disease, and leishmaniasis

Summary. Trypanosomatids depend on spermidine for growth and survival. Consequently, enzymes involved in spermidine synthesis and utilization, i.e. arginase, ornithine decarboxylase (ODC), S-adenosylmethionine decarboxylase (AdoMetDC), spermidine synthase, trypanothione synthetase (TryS), and trypanothione reductase (TryR), are promising targets for drug development. The ODC inhibitor α-difluoromethylornithine (DFMO) is about to become a first-line drug against human late-stage gambiense sleeping sickness. Another ODC inhibitor, 3-aminooxy-1-aminopropane (APA), is considerably more effective than DFMO against Leishmania promastigotes and amastigotes multiplying in macrophages. AdoMetDC inhibitors can cure animals infected with isolates from patients with rhodesiense sleeping sickness and leishmaniasis, but have not been tested on humans. The antiparasitic effects of inhibitors of polyamine and trypanothione formation, reviewed here, emphasize the relevance of these enzymes as drug targets. By taking advantage of the differences in enzyme structure between parasite and host, it should be possible to design new drugs that can selectively kill the parasites.     

Chagas disease: from bush to huts and houses. Is it the case of the Brazilian Amazon?

Two of the major problems facing the Amazon - human migration from the other areas and uncontrolled deforestation - constitute the greatest risk for the establishment of endemic Chagas disease in this part of Brazil. At least 18 species of triatomines had been found in the Brazilian Amazon, 10 of them infected with Trypanosoma cruzi, associated with numerous wild reservoirs. With wide-range deforestation, wild animals will perforce be driven into other areas, with tendency for triatomines to become adapted to alternative food sources in peri and intradomicilies. Serological surveys and cross-sectional studies for Chagas disease, carried out in rural areas of the Rio Negro, in the Brazilian Amazon, showed a high level of seropositivity for T. cruzi antibodies. A strong correlation of seroreactivity with the contact of gatherers of pia?ava fibers with wild triatomines could be evidenced.     

Epidemiology of Chagas disease in Jaguaruana, Ceará, Brazil. I. Presence of triatomines and index of Trypanosoma cruzi infection in four localities of a rural area

In order to assay the triatomine infestation and domiciliation in the rural area of Jaguaruana district, state of Ceará, Brazil, we studied, from November 2000 to April 2002, 4 localities comprising 158 domiciles as a whole, with an average of 4 inhabitants/house, who are dwelling in there for more than 7 years. Most houses have tile-covered roofs and the walls built with plaster-covered bricks (57%), followed by bricks without plaster (33%), and mud walls (7.5%). A total of 3082 triatomines were captured from different locations, according to the following capture plan: (a). intradomiciles: 238 Triatoma brasiliensis, 6 T. pseudomaculata, 9 Rhodnius nasutus, and 2 Panstrongylus lutzi; (b). peridomiciles (annexes): 2069 T. brasiliensis, 223 T. pseudomaculata, 121 R. nasutus, and 1 P. lutzi; (c). wild, in carnauba palms (Copernicia prunifera): 413 R. nasutus. From the captured triatomines, 1773 (57.5%) were examined. The natural index of Trypanosoma cruzi infection ranged from 10.8% to 30.2% (average of 17%), depending on the species and the location from where the triatomines were captured.     

The cytotoxic T-lymphocyte response to HTLV-I: the main determinant of disease?

There is a powerful, chronically activated cytotoxic T-lymphocyte (CTL) response to the Tax protein of human T-cell leukaemia virus type I (HTLV-I) in most people infected with the virus. The CTL select variant sequences of Tax which escape immune recognition and interfere with recognition of the wild-type protein. This positive selection process is more efficient in healthy HTLV-I carriers than in patients with tropical spastic paraparesis, an inflammatory neurological disease associated with HTLV-I. The mean virus load is more than 10-fold greater in patients with this neurological disease than in healthy carriers of HTLV-I. We conclude that anti-Tax CTL play an important part in limiting the rate of replication of HTLV-I. We suggest that the outcome of infection with HTLV-I is primarily determined by the CTL response of the individual: low CTL responders to HTLV-I develop a high virus load, resulting in widespread chronic activation of T cells. The activated T cells then invade the tissues and cause bystander tissue damage, probably by releasing cytokines and other soluble substances. An efficient CTL response to HTLV-I limits the equilibrium virus load, and so reduces the chance of developing inflammatory disease.     

From stem cells to red blood cells:how far away from the clinical application?

The generation of red blood cells(RBCs)from stem cells provides a solution for deficiencies in blood transfusion.Currently,primary hematopoietic stem cells,embryonic stem cells and induced pluripotent stem cells have shown the potential to produce fully mature RBCs.Here,we discuss the advantages,induction protocols,progress and possible clinical applications of stem cells in RBC production.     

Sex and gonadal hormones in mouse models of Alzheimer’s disease: what is relevant to the human condition?

Biologic sex and gonadal hormones matter in human aging and diseases of aging such as Alzheimer’s – and the importance of studying their influences relates directly to human health. The goal of this article is to review the literature to date on sex and hormones in mouse models of Alzheimer’s disease (AD) with an exclusive focus on interpreting the relevance of findings to the human condition. To this end, we highlight advances in AD and in sex and hormone biology, discuss what these advances mean for merging the two fields, review the current mouse model literature, raise major unresolved questions, and offer a research framework that incorporates human reproductive aging for future studies aimed at translational discoveries in this important area. Unraveling human relevant pathways in sex and hormone-based biology may ultimately pave the way to novel and urgently needed treatments for AD and other neurodegenerative diseases.     

The scales of the zebrafish: host–microbiota interactions from proteins to populations

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Getting to the guts of the matter: The status and potential of ‘omics’ research of parasitic protists of the human gastrointestinal system

Parasitic protists are a major cause of diarrhoeal illnesses in humans globally. Collectively, enteric pathogens exceed all other forms of infectious disease, in terms of their estimated global prevalence and socioeconomic impact. They have a disproportionately high impact on children in impoverished communities, leading to acute (diarrhoea, vomiting, dehydration and death) and chronic disease (malabsorption, malnutrition, physical and cognitive stunting and predisposition to chronic, non-communicable disease) consequences. However, historically, investment in research and disease control measures has been disproportionately poor, leading to their current classification as neglected pathogens. A sound understanding of their biology is essential in underpinning detection, treatment and control efforts. One major tool in rapidly improving our knowledge of these parasites is the use of biological systems, including ‘omic’ technologies. In recent years, these tools have shown significant success when applied to enteric protists. This review summarises much of this knowledge and highlights the significant remaining knowledge gaps. A major focus of the present review was to provide a perspective on a way forward to address these gaps using advanced biotechnologies.     

The kidney form of Trypanosoma musculi: A distinct stage in the life cycle?

Trypanosoma musculi is a parasite specific to mice, which resides in the blood and lacks intracellular stages. After immune clearance of the flagellates from the general circulation, mice are resistant to reinfection. Yet, long after parasites are no longer detected in the peripheral blood, they persist in the vasa recta of the kidneys and it has been proposed that this is an immunologically privileged site for T. musculi. This relationship provides a useful model for studies of latent or chronic infections in immune hosts. Here, Fernando Monroy and Donald Dusanic consider the immune responses of mice to T. musculi and compare characteristics of the parasites from the vasa recta (kidney forms, KFs) of mice with latent infections to trypanosomes from the peripheral blood (bloodstream forms, BSFs) of animals during active infections. They consider how KFs evade immune destruction and suggest that these sequestered parasites represent a distinct stage in the life cycle.     

Metal–drug synergy: new ruthenium(II) complexes of ketoconazole are highly active against Leishmania major and Trypanosoma cruzi and nontoxic to human or murine normal cells

In our ongoing search for new metal-based chemotherapeutic agents against leishmaniasis and Chagas disease, six new ruthenium–ketoconazole (KTZ) complexes have been synthesized and characterized, including two octahedral coordination complexes—cis,fac-[Ru^IICl₂(DMSO)₃(KTZ)] (1) and cis-[Ru^IICl₂(bipy)(DMSO)(KTZ)] (2) (where DMSO is dimethyl sulfoxide and bipy is 2,2′-bipyridine)—and four organometallic compounds—[Ru^II(η⁶-p-cymene)Cl₂(KTZ)] (3), [Ru^II(η⁶-p-cymene)(en)(KTZ)][BF₄]₂ (4), [Ru^II(η⁶-p-cymene)(bipy)(KTZ)][BF₄]₂ (5), and [Ru^II(η⁶-p-cymene)(acac)(KTZ)][BF₄] (6) (where en is ethylenediamine and acac is acetylacetonate); the crystal structure of 3 is described. The central hypothesis of our work is that combining a bioactive compound such as KTZ and a metal in a single molecule results in a synergy that can translate into improved activity and/or selectivity against parasites. In agreement with this hypothesis, complexation of KTZ with Ru^II in compounds 3–5 produces a marked enhancement of the activity toward promastigotes and intracellular amastigotes of Leishmania major, when compared with uncomplexed KTZ, or with similar ruthenium compounds not containing KTZ. Importantly, the selective toxicity of compounds 3–5 toward the leishmania parasites, in relation to human fibroblasts and osteoblasts or murine macrophages, is also superior to the selective toxicities of the individual constituents of the drug. When tested against Trypanosoma cruzi epimastigotes, some of the organometallic complexes displayed activity and selectivity comparable to those of free KTZ. A dual-target mechanism is suggested to account for the antiparasitic properties of these complexes.     

Distribution and infection of triatomines (Hemiptera: Reduviidae) by Trypanosoma cruzi in the state of Michoacán, Mexico

An entomological study of triatomine species was carried out to assess their prevalence in 10 localities of the state of Michoacán, Mexico. Entomological indices were calculated to estimate the risk for vector-borne transmission of Trypanosoma cruzi to the human population in this area. Four triatomine species (Triatoma barberi, Triatoma dimidiata, Meccus pallidipennis and Meccus longipennis) were collected from the study area. This is the first report of M. longipennis and T. dimidiata in Michoacán. M. pallidipennis was significantly (p < 0.05) more abundant than any of the other species collected in the study area. Infection indices were greater than 50% for each of the four collected triatomine species. Significantly more triatomines were collected from intradomiciliary areas than from peridomiciliary or sylvatic areas. Infestation, crowding and density indices were low, whereas colonisation indices were high in five localities. The current vectorial conditions in the study area require continuous entomological and serological surveillance to diminish the risk of T. cruzi transmission to human populations.