Fundação de Medicina Tropical

Plasmodium vivax is responsible for most malaria cases in Latin America and Southeast Asia and can cause severe manifestations. Prevention strategies such as vaccines, have been hampered by the complexity of the parasite's life cycle, especially in the liver stages. The P. vivax-Liver-Specific Protein 2 (Pv_LISP-2) has been described as essential for intrahepatic development, but its antigenicity has not yet been explored. Thus, in this study we evaluate the naturally acquired humoral response against two regions of Pv_LISP-2 in populations from the Brazilian Amazon exposed to P. vivax infection. Plasma samples were collected from infected individuals in Manaus (Amazonas state) and Boa Vista (Roraima state). Two structural regions of Pv_LISP-2 (Pv_L.seq1 and Pv_L.seq2) were expressed in E. coli, purified, and applied in ELISA assays to detect total IgM, IgG, and IgG subclasses antibodies. Furthermore, longitudinal follow-up was conducted for up to 180 days in part of the Manaus cohort. Pv_LISP-2 fragments were recognized by antibodies of P. vivax-infected individuals. During the acute phase, the response was characterized by high levels of IgM, followed by the induction of IgG, especially against Pv_L.seq1. The cytophilic subclasses IgG1 and IgG3 were the predominant subclasses. IgM responses correlated with parasitemia and days of symptoms but showed a negative association with hematological parameters (hemoglobin, hematocrit, and erythrocytes). This is the first study to evaluate naturally acquired antibodies against this liver-stage antigen of P. vivax, we showed that Pv_LISP-2 is naturally antigenic in individuals exposed to vivax malaria. While the functional implications of these responses remain to be fully elucidated, our findings support further investigation of Pv_LISP-2 as a potential vaccine candidate targeting the liver stage of P. vivax.

BackgroundEvidence on the accuracy and safety of the ESAT-6/CFP-10–based Diaskintest® in BCG-vaccinated populations outside Eastern Europe remains limited. In Brazil, recurrent shortages of purified protein derivative (PPD) have challenged the implementation of tuberculin skin testing, underscoring the need to evaluate alternative tools for tuberculosis infection (TBI) screening. This trial compared the diagnostic performance and safety of Diaskintest® with the tuberculin skin test (TST) using PPD Rt-23 in Brazilian adults, a predominantly BCG-vaccinated population.MethodA double-blind randomized clinical trial was conducted at eight centers in Brazil between July 2023 and September 2024. Participants were allocated to the TB group (microbiologically confirmed pulmonary TB), in whom sensitivity was estimated, and the control group (healthy, unexposed adults), in whom specificity was estimated using the QuantiFERON-TB Plus® (QFT-Plus) as the reference standard. All participants first underwent QFT-Plus testing, followed by intradermal application of Diaskintest® and TST in opposite arms, with randomized right–left allocation. Induration was measured at 48–96 h using a prespecified 5 mm cutoff. Secondary outcomes included safety, assessed through active monitoring of adverse events (AEs), included injection site reactions.ResultsA total of 337 controls and 136 TB participants were enrolled. TST showed higher sensitivity than both Diaskintest and QFT-plus (0.84 [95% CI 0.76–0.90] vs. 0.68 [95% CI 0.59–0.76], and 0.63 [95% CI 0.54–0.72], respectively). Diaskintest® demonstrated higher specificity than TST (0.93 [95% CI 0.90–0.96] vs. 0.75 [95% CI 0.70–0.80]). Injection-site reactions occurred less frequently with Diaskintest® than with TST (1.7% vs. 4.9%. RR = 0.35 [0.15–0.79]). The most common reactions were phlyctenular reactions and itching. No serious AEs were observed.ConclusionTST had greater sensitivity than Diaskintest®, whereas Diaskintest® demonstrated higher specificity and fewer local adverse reactions. In this study, specificity was estimated using QFT-Plus as a surrogate reference standard, acknowledging the absence of a true gold standard for tuberculosis infection. These complementary performance profiles highlight a trade-off between false-positive reduction and case detection, suggesting that the choice of test should consider programmatic priorities and local epidemiological context.Clinical trial registrationhttps://ensaiosclinicos.gov.br/, identifier RBR-7tn2ysw.

BackgroundSnakebite envenoming (SBE) is a neglected tropical disease with high incidence and impact in rural and remote areas of Brazil. Although the country maintains a national reporting system (SINAN) for SBE, few studies have systematically evaluated the quality of these surveillance data, which are essential for informing public health planning and antivenom distribution strategies.MethodologyThis is a descriptive study analyzing all snakebite notifications recorded in SINAN between 2007 and 2023. Data quality was evaluated across three dimensions: completeness, internal consistency, and reliability. Sociodemographic, clinical, and treatment-related variables were assessed by region using standardized classifications. Inter-database agreement for fatal outcomes was analyzed between SINAN and the Mortality Information System (SIM) using the Intraclass Correlation Coefficient (ICC).FindingsThe results showed excellent completeness for core demographic variables such as sex and age, but poor or very poor completeness for education level, occupation, race/ethnicity, and clinical manifestations. Internal inconsistencies, although infrequent, were present across all regions. The overall ICC for fatal outcomes was 0.95, with regional variation. Antivenom use was frequently inconsistent with national treatment guidelines, particularly in cases involving Crotalus, Lachesis, and Micrurus genera.Conclusions and significanceDespite the availability of a national notification system, snakebite surveillance in Brazil faces substantial limitations in data completeness and consistency, especially for clinical and treatment variables. These gaps are more pronounced in high-burden and remote regions, such as the Amazon, and may hinder equitable resource allocation and policy development. Strengthening notification practices, investing in training, and integrating clinical and epidemiological workflows are critical to improving the quality and utility of SBE data for public health action.

Children who are contacts of individuals with active pulmonary tuberculosis (PTB) are at risk of acquiring Mycobacterium tuberculosis infection (TBI). We evaluated the determinants of TBI in child and adolescent contacts. Pediatric (≤ 18 years old) close contacts of PTB patients enrolled in a multi-center Brazilian observational cohort were followed up to 6 months. Clinical evaluation, radiographic examination, and interferon gamma release assay (IGRA) were performed. Positive IGRA result at baseline or month 6 (IGRA-conversion) was considered an indicator of TBI. Multivariable mixed-effects logistic regressions were performed to identify factors associated with TBI. Among 562 close contacts enrolled, 171 (30.4%) had a positive IGRA at baseline, and 37 (9.5%) converted at month 6. Positive AFB, persistent cough and cavity on chest X-ray of TB index were independently associated with a positive IGRA result at baseline. IGRA-conversion was independently associated with older age among contacts and chest X-ray cavitations in the index cases. Contacts ≥ 15.9 years old had 3.4 (95%CI: 1.49–7.78, p = 0.004) adjusted odds ratio of IGRA-conversion than those < 15.9 years old. Among pediatric close TB contacts, the prevalence of IGRA positivity increased with age. Older children have substantially higher susceptibility to TBI upon exposure.

<bold>Introduction:</bold> Non-invasive ventilation (NIV) with bilevel positive airway pressure (BiPAP) has been shown to reduce muscle overload and improve airflow during exercise in patients with chronic cardiac and pulmonary diseases. <bold>Objective:</bold> To evaluate the hemodynamic effects and the perception of dyspnea and fatigue with BiPAP during an aerobic exercise (AE) session in individuals recovering from severe COVID-19. Methodology: This post hoc cross-sectional observational study is part of the COVIDReab clinical trial. Participants with severe COVID-19 and an mMRC symptom score of 2 or 3 were divided into two groups: AE and AE combined with BiPAP (AE + NVI). The exercise protocol included 5 minutes of warm-up, 15 minutes of treadmill aerobic exercise at 50% of the training heart rate (HR) based on the peak HR from a cardiopulmonary exercise test, and 5 minutes of active cool-down. <bold>Results:</bold> The study included 26 participants (14 in AE group and 12 in AE + NVI group). The AE + NVI group showed a more pronounced reduction in HR during active cool-down (p< 0.001), a decrease in diastolic blood pressure (DBP) during active cool-down (p=0.01), and improved SpO2 post-exercise (p=0.03). Additionally, the AE + NVI group exhibited significantly lower dyspnea values post-exercise compared to peak levels (p<0.001) and during active cool-down compared to post-exercise (p=0.01), effects not observed in the AE group. <bold>Conclusion:</bold> The use of BiPAP during AE accelerates hemodynamic and HR recovery and reduces dyspnea perception in individuals recovering from severe COVID-19, highlighting its potential as an important adjunct in physical rehabilitation for Long COVID.

Oropouche fever is a neglected tropical disease caused by the orthobunyavirus Oropouche virus (OROV). A recent OROV epidemic caused by a novel reassortant has seen infections across an expanded geographical range, with deaths of healthy adults plus vertical transmission leading to pregnancy loss. OROV research and epidemiology is hampered by a paucity of available tools for serology and molecular virology. We have purified recombinant OROV nucleoprotein and the spike region of the viral surface glycoprotein Gc. These antigens detect seroconversion following experimental infection of animals in indirect ELISA, confirming their antigenic authenticity. They stimulate the production of high neutralising antibody titres in animals, highlighting their promise as immunogens for vaccination. We developed a nanobody-based sandwich ELISA that can detect OROV antigens in human clinical serum samples with high efficiency, and we show that nanobodies directed against OROV Gc spike can potently neutralise infection by both historical OROV strains and the newly emerged reassortant. Our protein-based reagents will accelerate OROV research and highlight the utility of protein-based tools for future OROV vaccines and point-of-care diagnostic devices.

Tropical rainforests are rapidly disappearing due to human activities, particularly land-use changes, resulting in a heterogeneous mosaic of landscapes that substantially contribute to global terrestrial biodiversity loss. We investigated how changes in land-use affect species richness, composition, and functional guilds of ground-dwelling ants within various land-use systems at a local scale in the Amazonian rainforest. Our focus was to respond to the following: (i) How do local species richness and community composition reflect differences among land-use systems? (ii) Are ground-dwelling ants, especially specialists, negatively impacted by intensified land-use changes? We surveyed 55 sites representing five land-use systems: primary forest, secondary forest, forest corridor, selective logging, and Eucalyptus plantation. We registered 150 ant species, and species richness ranged from 43 to 94. Richness varies according to the land-use systems, likely influenced by differences in habitat structural complexity both vertically and horizontally. Ant species composition and guilds distribution also varied among land-use systems studied. Environments characterized by reduced structural complexity or higher disturbed levels, such as Eucalyptus plantations, tend to support lower resource availability, which may lead to decreased species richness. However, the surrounding matrix appears to play a key role in maintaining regional biodiversity, as evidenced by the absence of differences in ground-dwelling ants diversity across all land-use systems studied.

Deciphering the nanoscale architecture of mosquito wings is crucial for understanding species-specific flight adaptations and vectorial behaviors. In this study, we present a comprehensive quantitative analysis of the wing surface morphology of Anopheles darlingi and Anopheles aquasalis. By integrating high-resolution microscopy with Minkowski functionals and multifractal formalism, we reveal pronounced interspecific and dorso-ventral asymmetries in mosquito wing surfaces at both micro- and nanoscales. Atomic force microscopic topographies revealed distinct differences in dorsal versus ventral surface roughness, with An. aquasalis displaying higher elevation variance and denser nanomorphological heterogeneity. Minkowski volume and boundary descriptors showed slower decay and broader distribution for An. aquasalis, especially on its dorsal side, indicative of complex topographic relief. Multifractal spectra, derived from the box-counting method across q = -10 to +10, exhibited larger width (Δα ≈ 1.073) and stronger left-symmetry (H ≈ -0.852) in An. aquasalis, compared to narrower and more symmetric spectra in An. darlingi (Δα ≈ 1.009; H ≈ -0.532). Generalized fractal dimensions (D0 ≈ 2.00; D2 range: 1.951-1.982) and singularity spectra asymmetry (Δf up to -1.732) further differentiated species and wing sides. These multiscale descriptors demonstrate that An. aquasalis, particularly its ventral surface, harbors higher degrees of nanomorphological complexity and textural irregularity.