Memorias do Instituto Oswaldo Cruz最新文献

Background: Heterochromatin protein 1 (HP1) is widespread in several organisms playing a role in control of gene expression by heterochromatin formation and maintenance of silent chromatin. Schistosoma mansoni is a human parasite that is responsible for Schistosomiasis, a tropical neglected disease in the tropical and subtropical areas in the world, where the intermediate host Biomphalaria glabrata is present.

Objectives: In this study we attempted to investigate if the SmHP1 is enriched in S. mansoni chromatin in cercariae larvae stage, compared with another larvae stage sporocysts and its importance for S. mansoni life cycle progression and parasite oviposition.

Methods: We used ChIPmentation with commercial antibody ab109028 that passed in-house quality control. We also used RNA interference, mice infection and histology.

Findings: Our data show that S. mansoni HP1 enrichment is non-canonical with a peak at the transcription end sites of protein coding genes. We did not find strong differences in SmHP1 chromatin landscapes between sporocysts and cercariae. Knock- down of SmHP1 in schistosomula and in vivo experiments in mice unexpectedly increased parasite oviposition.

Main conclusions: Our results suggest that SmHP1 may influence chromatin structure in a non-canonical way in S. mansoni stages and may play a role in regulation of parasite oviposition.

Background: The malaria control strategy of the Brazilian Ministry of Health involves the classification of transmission contexts into special areas based on the distinct determinants of malaria in each location.

Objective: To search, find, organise, and map data about special areas using Brazilian databases and show their distribution among the states of the Brazilian Amazon.

Methods: A search related to the socioenvironmental determinants of malaria was conducted in Brazilian databases using the special areas of the Ministry of Health as a reference. Data were compiled by states in the Brazilian Amazon.

Findings: Indigenous areas occupy a significant portion of the Amazon territory and exhibit high incidence rates of malaria. Rural settlements also cover large areas of the Amazon, and in some states, more than 10% of malaria cases are associated with this typology. Legal and illegal mining areas, despite occupying small portions of the Amazon territory, contribute to the malaria caseload. In contrast, urban areas cover smaller regions, with low incidence rates.

Main conclusions: Despite the progress represented by the typological structure of special areas by the Ministry of Health's, our findings reveal limitations related to them because of their complexities and emphasise the need to further substratify these areas to devise control strategies more adapted to them.

Background: The importance of the mosquito Aedes aegypti as a vector of arboviruses like dengue, Zika, and chikungunya justifies the interest in investigating this species' physiology and reproductive biology. For the maintenance and expansion of Ae. aegypti populations, copulation, oogenesis, female oviposition capacity, embryo development and larval hatching are crucial processes regulated by biological clocks. Many of these parameters have currently been investigated under environmental and laboratory conditions. However, there are specific gaps regarding the effect of light on these critical reproductive aspects. In this study, the influence of light on some aspects of Ae. aegypti biology was evaluated.

Objectives: We investigated, in laboratory conditions, the effects of constant light on Ae. aegypti reproductive features: spermathecal content, embryo morphology, females' fecundity, and egg viability.

Methods: Morphological and physiological assays were performed using Ae. aegypti females and eggs obtained from forced egg laying. The reproductive aspects were analysed under constant light (LL = light/light) and light/dark cycles (LD12:12 = 12 h of light and 12 h of dark).

Findings and main conclusions: Our results proved the negative effect of constant light on egg production (decreasing the fecundity) and embryonic development (causing a drop in egg viability and perceptive damage in the embryos). The results presented here bring new information on the impacts that a source of constant light may have on the reproductive biology of Ae. aegypti.

Background: The HTLV-1 affects 5 to 10 million people worldwide. It is estimated that 5 to 10% of the infected individuals develop severe diseases, such as HTLV-Associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP) or Adult T-Cell Leukaemia/Lymphoma (ATLL). HTLV-1 transmission can occur mainly through unprotected sexual contact and from mother to child during breastfeeding. No vaccines can contain this infection, and strategies to prevent transmission become a priority. Therefore, it is important to know the main dissemination routes of each region to design the best public health strategies for controlling the spread of this virus.

Objectives: This study aimed to evaluate the prevalence of family aggregation in HTLV-1 infection among patients treated at a reference centre in Brazil.

Methods: A cross-sectional study was conducted with patients between July 2021 and August 2022. A total of 67 individuals were attended, of which 17 were classified as index cases due to a history of family aggregation, with 120 family contacts.

Findings: We found a prevalence of 36% of individuals positive for HTLV-1 and the same for HTLV-1 negative, while 28% of the family members had unknown serology. The possible transmission routes were identified, and the familial transmission histories within each family were hypothesised.

Main conclusions: These data can support specific decisions regarding the local reality, such as a better health strategy, especially in preventing new HTLV-1 cases.

Visceral Leishmaniasis in the Americas is primarily associated with Leishmania (Leishmania) infantum. This parasite is non-native and was imported during the colonisation era. The constitutive instability of the Leishmania genome allows this parasite to express flexibility in adapting to environmental fluctuations and different selective pressures, such as those the parasite faced when arrived in the New World. Therefore, genetic diversity is expected among the populations of L. infantum in the Americas, despite the bottle neck of importation route. Indeed, subpopulation of strains of L. infantum carrying a homozygous deletion in the genome was detected exclusively in the continent. These strains are more spread across Brazilian territory to the detriment of the non-deleted; the locus includes four genes, two of which encode the enzyme ecto-3'-nucleotidase/nuclease (3'NT/NU), a virulence factor in L. infantum. In this review, we highlight the sub estimated genetic complexity of L. infantum populations in Brazil, addressing the biological importance of the 3'NT/NU enzyme and the possible phenotypic impacts of its deletion, pointing out how it may configure an adaptive strategy for L. infantum. Finally, we raise the discussion of how the genome of L. infantum might be shaped in a unique way under the ecological conditions of Brazil.

Background: Rickettsia is a genus of Gram-negative bacteria that causes various diseases, including epidemic typhus, Rocky Mountain spotted fever, and Mediterranean spotted fever. Ticks transmit these diseases and commonly found in developing regions with poor sanitation. As a result, it is difficult to estimate the number of these diseases cases, making it challenging to create prevention and diagnostic mechanisms.

Objectives: Thus, this study aimed to develop an in silico multi-epitope vaccine against Rickettsia.

Methods: Eight proteins were previously identified as potential vaccine candidates through reverse vaccinology and were screened for epitopes that bind to MHC class I and II molecules. The epitopes were then analysed for antigenicity, allergenicity, and toxicity. The selected epitopes were linked with AAY and GPGPG sequences peptide and a known adjuvant, the B-chain of Escherichia coli heat-labile enterotoxin, to form a chimeric multi-epitope protein. The protein's three-dimensional structure was predicted, and molecular docking analysis was performed against the toll-like receptor 4 (TLR4). Finally, the immune response to the protein was simulated using C-ImmSim tool.

Findings: A total of 26 immunogenic epitopes, formed the multi-epitope vaccine RGME-VAC/ATS-1. The vaccine showed excellent immunogenic parameters and was predicted to do not be toxic or allergenic to the host. It also showed good potential stimulation of immune cells, with a propensity to generate memory cells and elicit IFN-γ secretion.

Main conclusions: The in silico validations suggest that our study successfully designed an innovative multi-epitope vaccine against Rickettsia, addressing the challenges posed by the elusive nature of diseases caused by this genus. We provide a promising potential for further experimental exploration and the development of targeted prevention and diagnostic strategies for these diseases.

Background: The Atlantic Forest harbours a rich mosquito assemblage, including vectors for diverse arbovirus. Mosquito species adapt to urban-forest landscape changes, acting as bridge vectors for pathogens.

Objectives: This study evaluated different collection methods for immature and adult mosquitoes combined with improving field personnel qualifications in a transition area between urbanised and sylvatic environments.

Methods: Immature and adult mosquitoes were collected from 33 collection points established in urban and peri-urban, sylvatic and transitional areas using different capture methods. During the course, 107 professionals were qualified.

Findings: Vectors (Anophelinae and Culicinae) were dominant in the urban/peri-urban environment (51.49%), followed by the transitional (26.69%) and sylvatic (21.82%) environments. Aedes (Stegomyia) albopictus (Skuse), Ae. (Ochlerotatus) scapularis (Rondani), Ae. (Stg.) aegypti (Linnaeus), Haemagogus (Conopostegus) leucocelaenus (Dyar & Shannon), undetermined Culex, Cx. (Melanoconion) pilosus (Dyar and Knab), Cx. (Carrollia) urichii (Coquillett), and Sabethes (Sabethes) albiprivus Theobald were most abundant, with Ae. albopictus collected from all ecotopes. Ovitrap provided a robust sample of the immature stages (92.8%), whereas other methods contributed 3.59% of total immatures, but greatest species richness (14 species). For adult mosquitoes, Shannon light trap resulted in greatest abundance (86.16%).

Main conclusions: The use of varied sampling techniques led to collection of a high mosquito species richness, which, combined with programs for training local professionals, should be an integral part of health surveillance for monitoring the risk of vector-borne diseases.

Background: Efflux pumps represents one of the most important mechanisms of antibiotic resistance. They allow bacteria to expel antibiotics from their cells before they reach the target site.

Objectives: The main objective of this work was to examine how cultivation temperature and its variations affect the activity of efflux pumps in Acinetobacter junii, Bacillus cereus, and Enterobacter cloacae isolated from a skin swab.

Methods: The isolation and purification of bacterial colonies were done through the streak plate method. For the identification of bacterial species, MALDI-TOF was utilised. To detect the activity of efflux pumps, agar-ethidium bromide cartwheel method was implemented.

Findings: The accumulation of ethidium bromide (EtBr) in bacterial cells was higher at 43ºC than at 30ºC, so the activity of efflux pumps was reduced at 43ºC in all isolates. A temperature of 7ºC also caused increased cumulation of EtBr in the cells, hence decreasing the activity of efflux pumps in isolated bacteria. Moreover, B. cereus was more sensitive to meropenem at 43ºC than at 36ºC.

Main conclusions: The activity of efflux pumps and antibiotic resistance can be strongly affected by changes in incubation temperature in vitro in tested human opportunistic bacterial pathogens.

Background: Toxocariasis is a neglected global zoonosis. The immunological diagnosis has setbacks that hinder further knowledge about its pathology, epidemiology, and public control measures, and lack of financial support and attention prevents innovative research. Although studies on synthetic peptides are common for several infectious pathologies, none evaluated chemically synthetic peptides for toxocariasis diagnosis.

Objective: This study aimed to identify potential synthetic peptides from C-type lectin 1 (Tc-CTL-1) from Toxocara canis.

Methods: In silico analyses were made by five B-cell peptide prediction programs, 3-D modelling, BLASTp homology analysis, and signal-peptide identification. SPOT-synthesis was used for epitope mapping and assessed by dot-blot. Sera from non-infected and T. canis, Strongyloides venezuelensis, Ascaris suum, or Schistosoma mansoni-infected animals were used to assess the peptide's immunogenicity and cross-reactivity. The selection of potential immunogenic epitopes included the most immunogenic peptides with the least cross-reactivity.

Findings: Fifty-five peptides were selected by in silico analysis. Dot-blot showed intense recognition by anti-Toxocara IgG and cross-reactivity with A. suum-infected mice. Selection criteria identified four epitopes with diagnostic potential.

Main conclusions: The findings demonstrate that synthetic peptides should be explored for innovation of toxocariasis diagnosis, and suggest the adaptation of dot-blot using the SPOT-synthesis technique as a potential immunodiagnostic platform.

Background: Bacillus Calmette-Guérin (BCG) is one of the most successful vaccines in the world and evidence suggests it can be used as a bacterial vector to deliver heterologous antigens.

Objectives: We evaluated whether BCG could be biotinylated and used as a carrier of Schistosoma mansoni antigen tetraspanin-2 (TSP-2) fused with rhizavidin, an avidin analog.

Methods: BCG was grown and biotinylated. The recombinant protein Rzv:TSP-2 was produced and purified from Escherichia coli. The biotinylation and antigen coupling was analysed by flow cytometry, enzyme-linked immunosorbent assay (ELISA) and Western blot. Vaccine immunogenicity was tested in immunised mice by the assessment of lung and splenic T cells.

Findings: BCG can be biotinylated, which in turn, can be coupled with Rzv:TSP-2. After a series of optimisations which involved molarity of the biotin, ratio of BCG:reagent and the concentration of Rzv:TSP-2 used, almost 50% of the bacteria were biotinylated and 35% coupled with antigen. Although a clear adjuvant effect of BCG was observed, evaluation of immune response in immunised mice demonstrated an overall low immunogenicity of the BCG-Rzv:TSP-2.

Main conclusion: These results demonstrated the use of BCG as a carrier of avidin-tagged antigens. Further optimisations are needed in order to strengthen the stability of tagged proteins in order to produce antigen-specific immune responses.