Biology subjects

Faria, I.

Publications and source records attributed to Faria, I..

2 recordsLinked to original sources

bioRxiv2025

Short-Report: First whole-genome evidence of dengue virus in field-caught mosquitoes from southern Brazil

Dengue virus (DENV) is a major global health threat whose expansion into temperate regions has been facilitated by climate change and vector adaptation. Despite recurrent epidemics in Brazil, genomic surveillance in mosquitoes remains limited, particularly in the South. To address this gap, we implemented a novel urban mosquito-trapping strategy optimized for low-density and peri-domestic environments in Porto Alegre, Rio Grande do Sul. Between April and July 2023, were collected 4,768 Aedes aegypti samples across 16 neighborhoods, generating 2,022 pools. Among these, 41 pools tested positive for DENV, of which 33 pools exhibited RNA integrity suitable for sequencing. Whole-genome sequencing revealed 33 DENV-positive pools, including 29 DENV-1 (Genotype V) and 4 DENV-2 (Genotype II). Two pools contained both serotypes, highlighting the risk of sequential infections in humans. Phylogenetic analyses indicated sustained local transmission alongside multiple introductions, while recurrent mutations, particularly in NS1, NS2A, and NS5, suggested ongoing viral adaptation. These findings represent the first vector-based genomic data for dengue in southern Brazil and demonstrate the utility of mosquito genomics for early outbreak detection, serotype monitoring, and preparedness in emerging transmission zones. Author SummaryDengue virus (DENV) continues to expand into new regions, driven by climate change and mosquito adaptation. In Brazil, dengue epidemics are recurrent, but genomic surveillance of mosquitoes is still scarce, particularly in the southern states. To fill this gap, we implemented an urban mosquito-trapping strategy designed for low-density and peri-domestic environments in Porto Alegre, Rio Grande do Sul. From April to July 2023, we collected 4,768 Aedes aegypti samples across 16 neighborhoods, generating 2,022 pools. Among these, 41 pools were positive for DENV, of which 33 pools exhibited RNA integrity suitable for sequencing, mainly DENV-1 (Genotype V) and DENV-2 (Genotype II), with two pools showing co-circulation of both serotypes, raising concern for sequential infections in humans. Phylogenetic analysis revealed sustained local transmission combined with multiple virus introductions, and mutations in NS1, NS2A, and NS5 suggested ongoing viral adaptation. Our findings provide the first mosquito-based genomic data for dengue in southern Brazil and highlight how mosquito genomics can strengthen early outbreak detection, serotype monitoring, and epidemic preparedness.

molecular biology↗

bioRxiv2024

Antiviral RNA interference targets viral transcripts but not genomes of RNA viruses in Drosophila melanogaster

RNA interference (RNAi) mediated by the small interfering RNA (siRNA) pathway is a major antiviral mechanism in insects. This pathway is triggered when double-stranded RNA (dsRNA) produced during virus replication is recognized by Dicer-2, leading to the formation of virus-derived siRNA duplexes. These siRNAs are loaded onto the programmable nuclease Argonaute-2 (AGO2), with one strand serving as a guide to target and cleave fully complementary sequences of viral RNAs. While siRNAs are generated from viral dsRNA, the specific viral RNA species targeted for silencing during RNA virus replication remains unclear. In this study, we characterized the primary viral RNA targets of the Drosophila siRNA pathway during infections caused by negative and positive RNA viruses, namely Vesicular stomatitis virus (VSV) and Sindbis virus (SINV). Our findings reveal that polyadenylated transcripts of VSV and SINV are the major targets of silencing by the siRNA pathway during infection, likely when they are poised for translation. Consistent with earlier findings, we confirmed that AGO2 copurifies with ribosomes, and this is not affected by virus infection. Therefore, we propose that the inhibition of the replication of RNA viruses in Drosophila results from the silencing of incoming viral transcripts, facilitated by the association of AGO2 with ribosomes. Author SummaryThe small interfering RNA (siRNA) pathway mediates major antiviral immune response in insects, functioning to cleave viral RNA. While this pathway has been extensively studied in the fruit fly Drosophila melanogaster, the specific molecular targets of inhibition by the siRNA pathway have remained unclear. In this study, we aimed to elucidate these targets. Our findings demonstrate that polyadenylated transcripts produced during viral infection are the primary targets of the Drosophila siRNA pathway, in the case of both negative and positive single-stranded RNA viruses. The silencing of these transcripts accounts for the antiviral effect of the siRNA pathway, suggesting that direct targeting of viral RNA genomes is unlikely to occur. We confirmed that Argonaute-2 (AGO2), the core component of the silencing complex, co-purifies with ribosomes and also show that this association is not affected by viral infection. This suggests that AGO2 is in permanent association with ribosomes where it can efficiently scan viral transcripts before they undergo translation by the cellular machinery, thereby preventing viral replication. These results provide valuable insights into the mechanism of gene silencing the siRNA pathway.

immunology↗