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Reservosomes are large round vesicles located at the posterior end of epimastigote forms of the protozoan Trypanosoma cruzi, the etiological agent of Chagas disease. They are the specific end organelles of the endocytosis pathway of T. cruzi, and they play key roles in nutrient uptake and cell differentiation. These lysosome-like organelles accumulate ingested macromolecules and contain large amounts of a major cysteine proteinase (cruzipain or GP57/51 protein). Aim of this study was to produce a monoclonal antibody (mAb) against a recombinant T. cruzi cruzipain (TcCruzipain) that specifically labels the reservosomes. BALB/c mice were immunized with purified recombinant TcCruzipain to obtain the mAb. After fusion of isolated splenocytes withmyeloma cells and screening, amAb was obtained by limiting dilution and characterized by capture ELISA. We report here the production of a kappapositive monoclonal IgG antibody (mAb CZP-315.D9) that recognizes recombinant TcCruzipain. This mAb binds preferentially to a protein with a molecular weight of about 50 kDa on western blots and specifically labels reservosomes by immunofluorescence and transmission electron microscopy. The monoclonal CZP-315.D9 constitutes a potentially powerful marker for use in studies on the function of reservosomes of T. cruzi. [ABSTRACT FROM AUTHOR]

Different methods for three-dimensional visualization of biological structures have been developed and extensively applied by different research groups. In the field of electron microscopy, a new technique that has emerged is the use of a focused ion beam and scanning electron microscopy for 3D reconstruction at nanoscale resolution. The higher extent of volume that can be reconstructed with this instrument represent one of the main benefits of this technique, which can provide statistically relevant 3D morphometrical data. As the life cycle of Plasmodium species is a process that involves several structurally complex developmental stages that are responsible for a series of modifications in the erythrocyte surface and cytoplasm, a high number of features within the parasites and the host cells has to be sampled for the correct interpretation of their 3D organization. Here, we used FIB-SEM to visualize the 3D architecture of multiple erythrocytes infected with Plasmodium chabaudi and analyzed their morphometrical parameters in a 3D space. We analyzed and quantified alterations on the host cells, such as the variety of shapes and sizes of their membrane profiles and parasite internal structures such as a polymorphic organization of hemoglobin-filled tubules. The results show the complex 3D organization of Plasmodium and infected erythrocyte, and demonstrate the contribution of FIB-SEM for the obtainment of statistical data for an accurate interpretation of complex biological structures. [ABSTRACT FROM AUTHOR]

Giardia intestinalis is a flagellated unicellular protozoan that colonizes the small intestine, causing the diarrheal disease called giardiasis. The production of extracellular vesicles (EVs) by G. intestinalis and the role of these EVs in the parasite's interaction with the host have been described. According to biogenesis, EVs are grouped mainly into large (microvesicles—derived from the plasma membrane) and small (exosomes—derived from multivesicular bodies). Populations of EVs are heterogeneous, and improved methods to separate and study them are needed to understand their roles in cell physiology and pathologies. This work aimed to enrich the large extracellular vesicles (LEVs) of G. intestinalis in order to better understand the roles of these vesicles in the interaction of the parasite with the host. To achieve the enrichment of the LEVs, we have modified our previously described method and compared it by protein dosage and using Nano tracking analysis. Giardia intestinalis vesiculation was induced by incubation in a TYI-S-33 medium without serum, to which 1 mM of CaCl2 was added at 37 °C for 1 h. Then, the supernatant was centrifuged at 15,000× g for 1 h (15 K 1 h pellet), 15,000× g for 4 h (15 K 4 h pellet) and 100,000× g for 1.5 h (100 K 1h30 pellet). The pellet (containing EVs) was resuspended in 1× PBS and stored at 4 °C for later analysis. The EVs were quantified based on their protein concentrations using the Pierce BCA assay, and by nanoparticle tracking analysis (NTA), which reports the concentration and size distribution of the particles. The NTA showed that direct ultracentrifugation at 100,000× g for 1.5 h and centrifugation at 15,000× g for 4 h concentrated more EVs compared to centrifugation at 15,000× g for 1 h. Additionally, it revealed that centrifugation at 15,000× g 4 h was able to concentrate at the same particle concentration levels as a direct ultracentrifugation at 100,000× g for 1.5 h. As for the enrichment of LEVs, the NTA has shown a higher concentration of LEVs in direct ultracentrifugation at 100,000× g for 1.5 h, and in centrifugation at 15,000× g for 4 h, compared to centrifugation at 15,000× g for 1 h. Our results have shown that the most used method at 15,000× g for 1 h is not enough to obtain a representative population of large EVs, and we suggest that LEVs released by G. intestinalis can be better enriched by direct ultracentrifugation at 100,000× g for 1.5 h, or by centrifugation at 15,000× g for 4 h. [ABSTRACT FROM AUTHOR]

Antimicrobial resistance is a public health burden with worldwide impacts and was recently identified as one of the major causes of death in 2019. Fosfomycin is an antibiotic commonly used to treat urinary tract infections, and resistance to it in Enterobacteriaceae is mainly due to the metalloenzyme FosA3 encoded by the fosA3 gene. In this work, we adapted a CRISPR-Cas9 system named pRE-FOSA3 to restore the sensitivity of a fosA3+  Escherichia coli strain. The fosA3+  E. coli strain was generated by transforming synthetic fosA3 into a nonpathogenic E. coli TOP10. To mediate the fosA3 disruption, two guide RNAs (gRNAs) were selected that used conserved regions within the fosA3 sequence of more than 700 fosA3+  E. coli isolates, and the resensitization plasmid pRE-FOSA3 was assembled by cloning the gRNA into pCas9. gRNA_195 exhibited 100% efficiency in resensitizing the bacteria to fosfomycin. Additionally, the edited strain lost the ampicillin resistance encoded in the same plasmid containing the synthetic fosA3 gene, despite not being the CRISPR-Cas9 target, indicating plasmid clearance. The in vitro analysis presented here points to a path that can be explored to assist the development of effective alternative methods of treatment against fosA3+ bacteria. [ABSTRACT FROM AUTHOR]

Background: Leishmania infantum is the most important etiological agent of visceral leishmaniasis in the Americas and Mediterranean region, and the dog is the main host. Miltefosine was authorized to treat canine leishmaniasis (CanL) in Brazil in 2017, but there is a persistent fear of the emergence of parasites resistant not only to this drug but, through cross-resistance mechanisms, also to meglumine antimoniate and amphotericin B. Additionally, the literature shows that acquisition of resistance is followed by increased parasite fitness, with higher rates of proliferation, infectivity and metacyclogenesis, which are drivers of parasite virulence. In this context, the aim of this study was to analyze the impact of treating a dog with miltefosine and allopurinol on the generation of parasites resistant to miltefosine, amphotericin B and meglumine antimoniate. Methods: In vitro susceptibility tests were conducted against miltefosine, amphotericin B and meglumine antimoniate with T0 (parasites isolated from a dog before treatment with miltefosine plus allopurinol), T1 (after 1 course of treatment) and T2 (after 2 courses of treatment) isolates. The rates of cell proliferation, infectivity and metacyclogenesis of the isolates were also evaluated. Results: The results indicate a gradual increase in parasite resistance to miltefosine and amphotericin B with increasing the number of treatment courses. An increasing trend in the metacyclogenesis rate of the parasites was also observed as drug resistance increased. Conclusion: The data indicates an increased L. infantum resistance to miltefosine and amphotericin B after the treatment of a dog with miltefosine plus allopurinol. Further studies with a larger number of L. infantum strains isolated from dogs with varied immune response profiles and undergoing different treatment regimes, are advocated. [ABSTRACT FROM AUTHOR]

Butanolides have shown a variety of biological effects including anti-inflammatory, antibacterial, and antiprotozoal effects against certain strains of Trypanosoma cruzi. Considering the lack of an effective drug to treat T. cruzi infections and the prominent results obtained in literature with this class of lactones, we investigated the anti-T. cruzi activity of five butanolides isolated from two species of Lauraceae, Aiouea trinervis and Mezilaurus crassiramea. Initially, the activity of these compounds was evaluated on epimastigote forms of the parasite, after a treatment period of 4 h, followed by testing on amastigotes, trypomastigotes, and mammalian cells. Next, the synergistic effect of active butanolides against amastigotes was evaluated. Further, metacyclogenesis inhibition and infectivity assays were performed for the most active compound, followed by ultrastructural analysis of the treated amastigotes and trypomastigotes. Among the five butanolides studied, majoranolide and isoobtusilactone A were active against all forms of the parasite, with good selectivity indexes in Vero cells. Both butanolides were more active than the control drug against trypomastigote and epimastigote forms and also had a synergic effect on amastigotes. The most active compound, isoobtusilactone A, which showed activity against all tested strains inhibited metacyclogenesis and infection of new host cells. In addition, ultrastructural analysis revealed that this butanolide caused extensive damage to the mitochondria of both amastigotes and trypomastigotes, resulting in severe morphological changes in the infective forms of the parasite. Altogether, our results highlight the potential of butanolides against the etiologic agent of Chagas disease and the relevance of isoobtusilactone A as a strong anti-T. cruzi drug, affecting different events of the life cycle and all evolutionary forms of parasite after a short period of exposure. [ABSTRACT FROM AUTHOR]

Background: Despite decades of use of control programs, schistosomiasis remains a global public health problem. To further reduce prevalence and intensity of infection, or to achieve the goal of elimination in low-endemic areas, there needs to be better diagnostic tools to detect low-intensity infections in low-endemic areas in Brazil. The rationale for development of new diagnostic tools is that the current standard test Kato-Katz (KK) is not sensitive enough to detect low-intensity infections in low-endemic areas. In order to develop new diagnostic tools, we employed a proteomics approach to identify biomarkers associated with schistosome-specific immune responses in hopes of developing sensitive and specific new methods for immunodiagnosis. Methods and findings: Immunoproteomic analyses were performed on egg extracts of Schistosoma mansoni using pooled sera from infected or non-infected individuals from a low-endemic area of Brazil. Cross reactivity with other soil-transmitted helminths (STH) was determined using pooled sera from individuals uniquely infected with different helminths. Using this approach, we identified 23 targets recognized by schistosome acute and chronic sera samples. To identify immunoreactive targets that were likely glycan epitopes, we compared these targets to the immunoreactivity of spots treated with sodium metaperiodate oxidation of egg extract. This treatment yielded 12/23 spots maintaining immunoreactivity, suggesting that they were protein epitopes. From these 12 spots, 11 spots cross-reacted with sera from individuals infected with other STH and 10 spots cross-reacted with the negative control group. Spot number 5 was exclusively immunoreactive with sera from S. mansoni-infected groups in native and deglycosylated conditions and corresponds to Major Egg Antigen (MEA). We expressed MEA as a recombinant protein and showed a similar recognition pattern to that of the native protein via western blot. IgG-ELISA gave a sensitivity of 87.10% and specificity of 89.09% represented by area under the ROC curve of 0.95. IgG-ELISA performed better than the conventional KK (2 slides), identifying 56/64 cases harboring 1–10 eggs per gram of feces that were undiagnosed by KK parasitological technique. Conclusions: The serological proteome approach was able to identify a new diagnostic candidate. The recombinant egg antigen provided good performance in IgG-ELISA to detect individuals with extreme low-intensity infections (1 egg per gram of feces). Therefore, the IgG-ELISA using this newly identified recombinant MEA can be a useful tool combined with other techniques in low-endemic areas to determine the true prevalence of schistosome infection that is underestimated by the KK method. Further, to overcome the complexity of ELISA in the field, a second generation of antibody-based rapid diagnostic tests (RDT) can be developed. [ABSTRACT FROM AUTHOR]