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Introdução: A esquistossomose é uma doença parasitária negligenciada, crônica e gradualmente debilitante, que mata 200 mil pessoas anualmente, segundo a Organização Mundial de Saúde. As estratégias atuais de controle da esquistossomose são ineficazes e há, portanto, necessidade de desenvolvimento de uma vacina contra a doença. Objetivo: Apresentar as principais pesquisas sobre o desenvolvimento de vacinas contra a esquistossomose. Metodologia: Revisão narrativa de literatura realizada em outubro de 2020, com a seleção de artigos a partir de 2012 nas bases de dados Pubmed e Scielo, utilizando os descritores “schistosomiasis” e “vaccine”. Foi consultada, também, a plataforma Clinical Trials. Foram incluídos artigos sobre vacinas contra Schistosoma mansoni e excluídos artigos referentes exclusivamente a outras espécies e outras formas de tratamento ou prevenção. Resultados: Foram selecionados 26 artigos, os quais apontam que há apenas duas vacinas em testes clínicos, a Sm14 e a Sm-TSP2. A Sm14 (Brasil), com fase II concluída, apresentou 50-68% de proteção contra a esquistossomose. A Sm-TSP2 (EUA), ainda em fase I, apresentou proteção de 65-69%. Além destas, alguns candidatos vacinais ainda estão na fase pré-clínica, como a Sm-p80 (EUA), a SmCB (Canadá), a SmCyp (Brasil) e vacinas quiméricas (Irã) que combinam antígenos através da imunoinformática. Há também propostas de fabricação de vacinas que usam nanotecnologia e nanobastões de ouro na produção de adjuvantes. Discussão: Ainda há muitos desafios para o desenvolvimento dessas vacinas, como a dificuldade de isolar os genes do parasita, a diferença de resposta imune entre os testes em animais e humanos, o movimento antivacina e o desinteresse de grandes indústrias farmacêuticas. Conclusão: Há duas pesquisas em fase de ensaios clínicos atualmente, a Sm14 e a Sm-TSP2, além de várias outras em fase pré-clínica. Apesar de mais estudos serem necessários, essa estratégia de imunização poderia ser responsável pelo controle da doença no futuro, problemática evidenciada nesse trabalho.

Background The palmitate analogue 2-bromopalmitate (2-BP) is a non-selective membrane tethered cysteine alkylator of many membrane-associated enzymes that in the last years emerged as a general inhibitor of protein S-palmitoylation. Palmitoylation is a post-translational protein modification that adds palmitic acid to a cysteine residue through a thioester linkage, promoting membrane localization, protein stability, regulation of enzymatic activity, and the epigenetic regulation of gene expression. Little is known on such important process in the pathogenic protozoan Trypanosoma cruzi, the etiological agent of Chagas disease. Results The effect of 2-BP was analyzed on different developmental forms of Trypanosoma cruzi. The IC50/48 h value for culture epimastigotes was estimated as 130 μM. The IC50/24 h value for metacyclic trypomastigotes was 216 nM, while for intracellular amastigotes it was 242 μM and for cell derived trypomasigotes was 262 μM (IC50/24 h). Our data showed that 2-BP altered T. cruzi: 1) morphology, as assessed by bright field, scanning and transmission electron microscopy; 2) mitochondrial membrane potential, as shown by flow cytometry after incubation with rhodamine-123; 3) endocytosis, as seen after incubation with transferrin or albumin and analysis by flow cytometry/fluorescence microscopy; 4) in vitro metacyclogenesis; and 5) infectivity, as shown by host cell infection assays. On the other hand, lipid stress by incubation with palmitate did not alter epimastigote growth, metacyclic trypomastigotes viability or trypomastigote infectivity. Conclusion Our results indicate that 2-BP inhibits key cellular processes of T. cruzi that may be regulated by palmitoylation of vital proteins and suggest a metacyclic trypomastigote unique target dependency during the parasite development. Electronic supplementary material The online version of this article (10.1186/s12860-018-0170-3) contains supplementary material, which is available to authorized users.

Leishmanicidal and trypanocidal activity of seventeen lipophilic diamines was evaluated in vitro against Leishmania braziliensis, L. chagasi, and Trypanosoma cruzi. Twelve compounds presented anti-Leishmania and six showed anti-T. cruzi amastigote activity. Compound 14 (N-tetradecyl-1,4-butanediamine) was the most active against both L. braziliensis (IC50 = 2.6 μm) and L. chagasi (IC50 = 3.0 μm) which showed a selectivity index (SI) >100. N-decyl-1,6-hexanediamine (compound 9) presented an IC50 = 1.6 μm and SI >187 and was over six times more potent than the reference drug benznidazole against T. cruzi. Treatment of infected or uninfected macrophages with compounds 9 and 14 did not induce significant TNFα and NO production. Four compounds (15, 16, 22, and 23) inhibited 78.9%, 77.7%, 83.7%, and 70.1% of rTRLb activity, respectively, and compound 23 inhibited 73.3% of rTRTc activity at 100 μm. A concentration-dependent effect on mitochondrial membrane depolarization was observed in T. cruzi epimastigotes treated with compound 9, suggesting this mechanism may be involved in the trypanocidal effect. On the contrary, in L. braziliensis promastigotes treated with compound 14, no mitochondrial depolarization was observed. Our results demonstrate that N-decyl-1,6-hexanediamine and N-tetradecyl-1,4-butanediamine are promising molecules for the development of novel leading compounds against T. cruzi and Leishmania spp., particularly given a possible alternative mechanism of action.

Protein palmitoylation is a post-translational modification that contributes to determining protein localization and function. Palmitoylation has been described in trypanosomatid protozoa, but no zDHHC palmitoyl transferase has been identified in Trypanosoma cruzi, the etiological agent of Chagas disease in Latin America. In this study we identify and show the subcellular localization of TcHIP (Tc00.1047053508199.50), a putative T. cruzi zDHHC palmitoyl transferase. Analysis of the deduced protein sequence indicates that it contains ankyrin repeats (Ank and Ank2) and the zDHHC conserved domain, typical of zDHHC palmitoyl transferases. A TcHIP polyclonal antiserum obtained from mice immunized with the purified recombinant protein was used to study the presence and subcellular localization of the native enzyme. In western blots this antiserum recognized a protein of about 95 kDa, consistent with the predicted molecular mass of TcHIP (95.4 kDa), in whole extracts of T. cruzi epimastigotes, metacyclic trypomastigotes and intracellular amastigotes. Immunolocalization by confocal microscopy showed TcHIP labeling at the Golgi complex, co-localizing with the T. cruzi Golgi marker TcRab7-GFP. Transfectant T. cruzi epimastigotes containing a construct encoding TcHIP fused to proteins A and C (TcHIP/AC) were obtained. In western blotting experiments, the TcHIP polyclonal antiserum recognized both native and TcHIP/AC proteins in extracts of the transfectants. Confocal microscopy showed co-localization of native TcHIP with TcHIP/AC. These findings demonstrate the presence of a putative zDHHC palmitoyl transferase (TcHIP) containing ankyrin and zDHHC domains in different developmental forms of T. cruzi, and its association with the Golgi complex.

We report the synthesis of a series of diaminated terpenoids containing, as side-chain of the diamine core, the "head-to-tail" prenyl derivatives, with amino amino spacers of variable length. In vitro biological activity of these compounds was evaluated against Mycobacterium tuberculosis and Leishmania amazonensis, and the structure-activity relationships are discussed. Different biological results were observed depending on the terpenic side-chain length. The best results were obtained for trans,trans-farnesol derivatives. Moreover, these results demonstrated that the stereochemistry of the double bond could play an important role in determining antitubercular and antileishmanial activities of these compounds.

Here we describe the visualization by confocal microscopy of ingested gold (15 nm)-labeled transferrin in epimastigote forms of the protozoan Trypanosoma cruzi. Intracellular gold labeling was evident at two sites, which represent the bottom of the cytopharynx and the reservosomes. The gold tracer was best observed by confocal microscopy by using the 633 nm excitation wavelength. Intracellular gold clusters larger than 60 nm could be visualized by either gold reflection (light scattering) or photoluminescence modes. The gold reflection mode, the gold photoluminescence mode and the anti-transferrin immunofluorescence image of gold-labeled transferrin showed co-localization, thus demonstrating that the gold visualization modes did not represent artifacts or mislocalization of the biomarker. Visualization of protein-gold nanoparticle complexes by confocal microscopy thus emerges as a promising imaging tool to explore the endocytic pathway in trypanosomes and other cell types, as well as to perform immunolocalization studies using gold-labeled secondary antibodies.

The present paper reports the synthesis and antiprotozoal activity of N-quinolin-8-yl-arylsulfonamides and their copper and zinc complexes. Sulfonamides 2-5 were synthesized by reacting 8-aminoquinoline with several commercial arylsulfonyl chlorides. The corresponding complexes 6-13 were obtained using copper (II) acetate or zinc chloride in methanol. In vitro activity was carried out against promastigote forms of Leishmania braziliensis and L. chagasi, and epimastigote forms of Trypanosoma cruzi. Selected compounds were tested against axenic amastigote forms of L. braziliensis. The new 2,5-dichlorobenzenesulfonamide ligand was found to be inactive under the selected bioassays, however its copper complex 8 was active with the highest selective indexes (SI) against L. braziliensis promastigote and amastigote forms, with IC50 values of 2.59 and 0.35 μM, respectively. Difluorinated copper 10 and zinc 11 complexes were most active against L. braziliensis, with IC50 of 1.11 μM and 1.25 μM, respectively. However, the SI values were about 12 for both compounds. In general, the complexation of sulfonamides increases the antiprotozoal activity, as well as the cytotoxicity on Vero cells. These results confirm the antiprotozoal potential of sulfonamides and metal-based sulfonamides.

Background Clathrin-mediated vesicular trafficking, the mechanism by which proteins and lipids are transported between membrane-bound organelles, accounts for a large proportion of import from the plasma membrane (endocytosis) and transport from the trans-Golgi network towards the endosomal system. Clathrin-mediated events are still poorly understood in the protozoan Trypanosoma cruzi, the causative agent of Chagas disease in Latin America. In this study, clathrin heavy (TcCHC) and light (TcCLC) chain gene expression and protein localization were investigated in different developmental forms of T. cruzi (epimastigotes, trypomastigotes and amastigotes), using both polyclonal and monoclonal antibodies raised against T. cruzi recombinant proteins. Results Analysis by confocal microscopy revealed an accumulation of TcCHC and TcCLC at the cell anterior, where the flagellar pocket and Golgi complex are located. TcCLC partially colocalized with the Golgi marker TcRAB7-GFP and with ingested albumin, but did not colocalize with transferrin, a protein mostly ingested via uncoated vesicles at the cytostome/cytopharynx complex. Conclusion Clathrin heavy and light chains are expressed in T. cruzi. Both proteins typically localize anterior to the kinetoplast, at the flagellar pocket and Golgi complex region. Our data also indicate that in T. cruzi epimastigotes clathrin-mediated endocytosis of albumin occurs at the flagellar pocket, while clathrin-independent endocytosis of transferrin occurs at the cytostome/cytopharynx complex.

Background. Chagas disease is caused by the protozoan parasite Trypanosoma cruzi, which exhibits a high genetic variability. TcI, TcII, or mixed TcI/TcII strains may be found during acute human infection while mainly TcII parasites are present at the chronic stage of disease. In a previously studied Chagas disease outbreak, we identified mixed TcI/TcII strains in the vector Triatoma tibiamaculata and only TcII strains in infected humans, indicating that T. cruzi populations may be selected within the human host. Methods. Utilizing molecular typing and cell biology techniques, we investigated the interaction of TcI, TcII, and mixed TcI/TcII strains with macrophages, an important cell population implicated in controlling protozoan infection. Results. TcII but not TcI strains were selected by both human and murine macrophages in vitro and by peritoneal cavity cells in vivo. Biological analysis revealed that, compared with TcI, TcII strains display higher infective and multiplicative ability as well as lower doubling time inside macrophages. However, TcI and TcII strains present similar susceptibility to interferon-c‐activated macrophages in vitro. Conclusions. Taken together, our results reveal the existence of an intracellular selection process in macrophages that favors TcII, but not TcI, when infection occurs with vector-derived mixed TcI/TcII strains.

A study of the natural infection of phlebotomine sand flies by Leishmania (Viannia) was conducted in a focus of cutaneous leishmaniasis in Picarras, on the northeastern coast of the Brazilian state of Santa Catarina. In total, 562 female Nyssomyia neivai were collected by miniature light traps near houses, separated in 61 pools and examined by PCR and Southern blot hybridization. Eight pools, four of them from the same light trap/night, were positive. This is the first finding of natural infection by Le. braziliensis of adequately identified Ny. neivai in Brazil. In this preliminary observation we observed the abundance and predominance of Ny. neivai among the captured phlebotomine species (98.5%), indicating that Ny. neivai may be the dominant vector of Leishmania in the subgenus Viannia in this area.

Intracellular multiplication of Trypanosoma rangeli was evaluated in vitro using experimental infection of Vero cells, murine macrophages, and promonocytes with T. rangeli Choachi, Macias, and SC-58 clone B1 strains. Our results revealed a low infectivity of all T. rangeli strains to these cell lines. Macrophages showed the highest infection rate; however, intracellular forms were no longer observed 48 h post infection Despite the observation of intracellular parasites up to 144 h post infection, the infection rates of Vero cells and J774G.8 promonocytes with these parasite strains were always below 5%. Pre-incubation of parasites with normal mouse serum increased the initial infectivity but not the time course of the infection. Under our experimental conditions, we did not observe any evidence of intracellular multiplication of T. rangeli within these cell lines.

The susceptibility of four Rhodnius species to different Trypanosoma rangeli strains was evaluated using both intracoelomic inoculation and oral infection. Rhodnius prolixus, Rhodnius domesticus, Rhodnius neglectus and Rhodnius nasutus were infected with Trypanosoma rangeli Macias (Venezuela), Choachi (Colombia) and SC-58 (Brazil) strains, revealing distinct haemolymph and salivary glands infection rates. The obtained infection rates were revealed to be dependent on the method of infection and the triatomine species. Our results suggest the existence of a high adaptation between the strain and the local vector.

Ten chalcones were synthesized and tested as potential leishmanicidal and trypanocidal agents. All tested compounds caused concentration-dependent inhibition of the in vitro growth ofLeishmania braziliensisandTrypanosoma cruziwith no significant toxic effect towards host macrophages. Our results show that the positions of the substituents seem to be critical for their antiprotozoal activities.