Memorias do Instituto Oswaldo Cruz最新文献

Background: Malaria, caused by protozoa of the genus Plasmodium and transmitted by Anopheles mosquitoes, remains a significant global health concern. In 2022, approximately 249 million malaria cases were reported worldwide, including 163,000 in Brazil. In the Atlantic Forest, An. bellator and An. cruzii are the primary vectors of malaria transmission.

Objectives: This study used a cytochrome C oxidase I (COI) gene fragment to investigate the genetic population structure of An. bellator in the Brazilian Atlantic Forest.

Methods: Mosquitoes were collected from Itaparica (BA), Camacan (BA), Ilha Grande (RJ), Antonina (PR), Ilha do Mel (PR), and Florianópolis (SC). They were morphologically identified and individually photographed. DNA was extracted, and a COI gene fragment was amplified using polymerase chain reaction (PCR), purified, and sequenced. Additionally, sequences from Trinidad, Colombia, and São Paulo State, obtained from GenBank, were included in the analysis. These sequences were used for molecular identification, genetic variation analysis within and between populations, and phylogenetic assessment.

Findings: The analysis revealed that the An. bellator population from Trinidad is genetically distinct from all analysed populations. Furthermore, the Camacan population forms a distinct group separate from the Itaparica population, with both differing from the southern Brazilian populations and that of Colombia. Additionally, the data suggest that the southern Brazilian populations may represent distinct incipient species, particularly the Ilha Grande sample. This divergence is strongly supported by fixed genetic differences, high F ST values, and genealogical analysis.

Main conclusion: The findings provide strong evidence of cryptic species within An. bellator, which appears to consist of at least three sibling groups: one from Trinidad and Tobago; An. bellator B, which includes sequences from Camacan; and An. bellator A, which contains sequences from Colombia, Itaparica, Ilha Grande, São Paulo, Florianópolis, Ilha do Mel, and Antonina. Despite its geographical proximity to Camacan (280 km), the Itaparica population clusters with southern populations ~2,000 km away, while remaining genetically distinct from them. Additionally, the study identified higher F ST values between the Ilha Grande population and other southern Brazilian samples, highlighting further genetic divergence.

Background: The effectiveness of coronavirus disease 2019 (COVID-19) vaccines is well established; however, the long-term durability of vaccine-induced immunity remains to be fully elucidated.

Objectives: This study longitudinally compared humoral and cellular immune responses in two groups: G1, who received two doses of Sinovac-CoronaVac, and G2, who received two doses of AstraZeneca-Oxford, both subsequently boosted with Pfizer.

Methods: Immune responses were assessed at five time points: P1 (prior to the second dose), P2 (90-180 days after the second dose), P3 (pre-booster, six-eight months post-second dose), P4 (90-180 days post-booster), and P5 (180-270 days post-booster). Anti-Spike severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgG levels were measured by enzyme-linked immunosorbent assay (ELISA), while IFNγ-producing cells in response to Spike peptides were quantified using enzyme-linked immune absorbent spot (ELISPOT). IgG subclasses were analysed in a subset of samples.

Results: Following the first dose, Sinovac-CoronaVac induced lower anti-Spike IgG levels than AstraZeneca-Oxford, though levels equalised after the second dose. After the Pfizer booster, anti-Spike IgG levels remained elevated for up to six months in both groups. IgG1 was predominant in both groups, with occasional expression of IgG2 and IgG4. The mean frequency of IFNγ-producing cells was lower in the Sinovac-CoronaVac group before and up to six months after the second dose, compared to AstraZeneca-Oxford. However, post-Pfizer booster, both means became comparable. Between 90-180 days post-booster, the Sinovac-CoronaVac + Pfizer group exhibited a statistically significant decline in IFNγ-producing cells relative to the AstraZeneca-Oxford + Pfizer group. By P5, over half of individuals in the Sinovac-CoronaVac + Pfizer group demonstrated no detectable cellular response.

Main conclusions: High antibody levels were maintained for up to six months following both homologous and heterologous vaccination. However, cellular immunity declined more markedly in the Sinovac-CoronaVac + Pfizer group, resulting in a higher proportion of non-responders. These findings underscore the importance of tailored booster strategies to sustain protective immunity against COVID-19.

Mandatory notification of chronic Chagas disease (CD) is vital for improving public health responses in Brazil, where millions are affected. Implemented nationally in 2020 and supported by the "e-SUS Notifica" platform in 2023, this system enables accurate disease burden assessment, early diagnosis, and treatment planning. It facilitates resource allocation and targeted interventions, addressing gaps in surveillance and care. Expanding these efforts and ensuring access to treatment is essential for Brazil's goal of eliminating CD by 2030.

Background: Insecticides play a critical role in controlling insect vectors, particularly during epidemics. Effective chemical control relies on the robust monitoring of insecticide resistance to guide evidence-based decision-making in vector control strategies.

Objectives: This study assessed the susceptibility of Aedes aegypti, the primary vector of dengue, Zika, and Chikungunya viruses, to various larvicides and adulticides deployed during Brazil's national campaigns from 2020 to 2023.

Methods: Mosquito collection was performed in 46 Brazilian municipalities using ovitraps. Eggs were transported to FIOCRUZ to establish the F1 and F2 generations. The Rockefeller strain was employed to determine the discriminating concentrations (DC) for the larvicide Natular™ 20EC (spinosad) and the adulticides Cielo™ (imidacloprid and prallethrin) and Fludora® Fusion (clothianidin and deltamethrin) using a modified World Health Organization (WHO) bottle bioassay. These DCs were then used to estimate the resistance status of Ae. aegypti populations in the tested formulations. Resistance intensity was assessed by exposing mosquitoes to five, 10, or 20 times the DC concentrations.

Findings: All Ae. aegypti populations were fully susceptible to larvicide spinosad. However, resistance to both adulticide formulations was detected based on WHO criteria (mortality rates < 90%). Intensity assays revealed high to very high resistance to combined adulticide products.

Main conclusions: Our findings indicate the full susceptibility of Ae. aegypti populations in Brazil to spinosad, but substantial resistance to adulticides used in space spraying and residual applications, likely due to pre-existing pyrethroid resistance. However, the specific contributions of each active ingredient remain unclear, owing to the evaluation of the combined formulations. The efficacy of both traditional and alternative vector control strategies must be continuously evaluated and closely monitored to ensure the real-time assessment of their performance. For chemical control, future studies should prioritise the assessment of combination products in field trials, refining laboratory assays, and sustaining insecticide resistance surveillance to optimise control efforts in Brazil.

Background: The cycle of the Orthoflavivirus nilense (West Nile virus - WNV) involves birds and mosquitoes, while humans and equids serve as terminal hosts. In 2014, the first human case in Brazil was confirmed in Piauí State.

Objectives: To investigate the presence of WNV in birds, mosquitoes, and equids in municipalities of Piauí.

Methods: Collections were carried out following recommendations from the Ministry of Health of Brazil, in 11 municipalities (all with human cases or bird mortality), where biological samples were collected from birds, mosquitoes, and equids. The Viral RNA extraction was performed using a commercial kit, following the manufacturers' recommendations; samples were subjected to reverse transcription and polymerase chain reaction, with specific primers for WNV.

Findings: 2,706 samples were collected (636 birds, belonging to 99 species; 420 equids, and 1,650 mosquitoes, grouped into 346 pools, totaling 18 species. No collected sample yielded a positive result, corroborating with other studies showing the difficulty of molecular detection of WNV in healthy animals, which may explain the non-detection, in addition to the delayed diagnosis in humans.

Main conclusions: A local investigation involving suspected cases is still recommended in animals; however, in locations with late diagnosis in humans we suggest a serological survey of asymptomatic birds and equids.

Background: The Haemagogus genus includes nine mosquito species reported in Brazil, each with distinct distribution patterns. Haemagogus leucocelaenus, a major yellow fever vector, is widely distributed throughout the country, while Haemagogus leucophoebus, a morphologically similar species, has only been identified in Acre State.

Objectives: This study evaluated the presence of Haemagogus species in southern Brazil by comparing their morphological and molecular characteristics.

Methods: Mosquitoes were collected from five municipalities in southern Santa Catarina State, Brazil. Each specimen was identified morphologically and photographed. Genomic DNA was extracted, and a Cytochrome C Oxidase Subunit I (COI) gene fragment was amplified using polymerase chain reaction (PCR). The positive amplicons were sequenced for molecular identification.

Findings: New records of Hg. leucocelaenus were found in Santa Rosa de Lima, Rio Fortuna, Braço do Norte, São Martinho, and Pedras Grandes, located at the southern edge of the Atlantic Forest. This study expands the known distribution of Hg. leucocelaenus, the only Haemagogus species identified in the area, with 91 specimens collected. Although some specimens exhibited morphological variations that might lead to misidentification as Hg. leucophoebus, molecular identification confirmed that all were Hg. leucocelaenus.

Main conclusions: This study is the first to report Hg. leucocelaenus in Santa Catarina, Brazil, and provides DNA barcoding sequences from southern Brazil. This method offers a reliable alternative for species identification, especially when combined with morphological analysis. Further molecular studies are needed to determine whether the morphological variations observed indicate intraspecific differences.

Background: Titan cells in Cryptococcus species play a critical role in fungal virulence by resisting oxidative stress, phagocytosis, and antifungal treatments. Developing reliable methods to induce titan cells is crucial for understanding the mechanisms of Cryptococcus pathogenesis.

Objectives: In this study we report an unexpected discovery of a simple in vitro induction of titan cells in Cryptococcus neoformans and Cryptococcus gattii using Neurobasal™ (NB) medium.

Methods and findings: By employing established in vitro culture methods, we demonstrate a significantly higher capacity for titan cell formation in Cryptococcus spp. Cells grown in complete NB medium exhibited larger cell bodies, increased capsule sizes, and a higher percentage of titan cells compared to those grown in minimal medium (MM). NB medium without the B27 supplement significantly impacted titan cell formation.

Main conclusions: Our findings indicate that NB medium, originally developed for neuronal cell cultures, is a useful tool for studying titan cell biology. This is particularly relevant given the association between titan cells and the central nervous system, highlighting their potential role in Cryptococcus pathogenesis.

Background: Dermatomycoses are caused by various fungi, including dermatophytes and Candida species, which are the most prevalent in isolated or associated forms. A great number of virulence factors expressed by these fungi are important for infection, and biofilm formation leads to the persistence of these infections.

Objectives: This work aimed to evaluate the dynamics of Candida albicans filamentation genes in biofilms formed by Candida albicans and Trichophyton rubrum.

Methods: The effect of the supernatants on the biofilms was assessed by XTT reduction assay, confocal microscopy, and gene expression profile analysis by real-time polymerase chain reaction (RT-PCR).

Findings: The supernatants did not reduce the metabolic activities or damage the topography of the monospecies biofilms but caused a reduction in their thickness. The filamentation of C. albicans was inhibited when both fungi were cultivated directly. The filamentation genes studied (CPH1, HWP1, and EFG1) were negatively modulated in C. albicans.

Main conclusions: Our findings suggest that the antagonistic relationship shown by T. rubrum against C. albicans may be attributed to alterations of C. albicans filamentous genes.

Background: Human enterovirus C99 (HEV-C99) is a member of the species Enterovirus C. Currently, three complete genomes of HEV-C99 were reported in Brazil, all obtained from children with gastroenteritis symptoms. Notwithstanding, no HEV-C99 complete genome associated with AFP cases in Brazil have been analysed so far.

Objectives: In light of this, molecular characterisation of an HEV-C99 isolated from a case of acute flaccid paralysis (AFP) in Brazil was carried out.

Methods: In 2005, an HEV-C99 strain was isolated from a 2-year-old female child in Santa Catarina State, Brazil, showing classic symptoms of AFP. Stool sample was inoculated into specific cell cultures. Viral RNA was extracted, and polymerase chain reaction (PCR) were performed to amplify the VP1 gene; the sequence was analysed for molecular identification. Subsequently, the complete genome was sequenced and analysed, including a phylogenetic analysis of the VP1 gene.

Findings: The isolate, denominated HEV-C99/33322/BRA/2005 presented 85.85% identity to other HEV-C99 strains also described in Brazil, subsequently. Besides, the isolate grouped together with HEV-C99 cluster C strains. To our knowledge, this was the first described HEV-C99 isolated from an AFP case in Brazil.

Main conclusions: The data generated in this study bolster the role of HEV-C99 as an etiologic agent of AFP. Furthermore, this research enhances our knowledge regarding the HEV-C99 genetic diversity.

Background: Elite controllers (ECs) are a rare subset of individuals who naturally suppress human immunodeficiency virus type 1 (HIV-1) replication in the absence of antiretroviral therapy. Specific polymorphisms in the accessory proteins Vif and Vpr have been associated with diminished viral fitness in vitro and are more frequently detected in ECs compared to other individuals infected with HIV-1.

Objective: To assess the frequency of gross genetic defects or polymorphisms that may attenuate the function of the HIV-1 accessory proteins Vif and Vpr within the proviral quasispecies of ECs.

Methods: We performed single-genome amplification (SGA) and sequence analysis of the proviral quasispecies of the accessory genes vif and vpr in samples obtained from eight ECs with over 10 years of suppressive viral control and no evidence of disease progression.

Findings: In subjects EC11, EC38 and EC52, most proviral clones encode full-length, intact vif and vpr open reading frames without known attenuating polymorphisms. Subject EC35 displayed stop codons in a substantial fraction of vif (33%) and vpr (67%) proviral clones. Subject EC36 exhibited the attenuating polymorphisms Vpr-Q3R + R77Q combined in all proviral clones. Subject EC17 showed stop codons in 20-30% of vif-vpr proviral clones, hypermutated sequences in 20% of vif proviral clones, and the attenuating polymorphism Vpr-R77Q in all proviral clones. Subject EC19 presented stop codons in 8-17% of vif-vpr proviral sequences, hypermutated sequences in 25% of vif-vpr proviral clones, and the polymorphisms Vif-R132S+Ins61(EDK) and Vpr-R77Q in all clones analysed. Finally, subject EC42 displayed stop codons in 25-38% of vif-vpr proviral sequences, hypermutated sequences in 25% of vif proviral clones, and the polymorphisms Vif-T20A+R132S and Vpr-R77Q in most (> 80%) proviral clones.

Main conclusions: Mutations associated with attenuation of HIV-1 Vif and/or Vpr functions may contribute to the long-term control of viral replication and disease progression in certain ECs.