Biology subjects

Rocha, M. N.

Publications and source records attributed to Rocha, M. N..

4 recordsLinked to original sources

bioRxiv2026

The Glycoproteome of Loxosceles Venom Reveals an Expanded Landscape of Animal Toxins

Spider venoms of the genus Loxosceles constitute a complex mixture of bioactive proteins and peptides associated with the major clinical manifestations of loxoscelism. Although significant advances have been made in the proteomic characterization of these toxins, studies addressing post-translational modifications, particularly glycosylation, and their potential impact on venom properties remain scarce. Here, we investigated the occurrence and characteristics of N-glycosylation in the venoms of Loxosceles gaucho, Loxosceles intermedia, and Loxosceles laeta. Using two-dimensional electrophoresis combined with glycoprotein-specific staining and LC-MS/MS, we identified glycosylation in different proteins biologically relevant to envenomation, predominantly belonging to the phospholipase D family, with distinct profiles among the species analyzed. Bottom-up glycoproteomic analysis of crude venoms using Byonic and a customized sequence database identified 88 N-glycosylated peptide sequences, primarily associated with lyases and hydrolases. Extensive microheterogeneity was detected at individual glycosylation sites, with paucimannosidic structures predominating alongside oligomannose and hybrid/complex N-glycans. Complementary enzyme-linked lectin assays supported the presence of distinct carbohydrate epitopes, including mannose, galactose, and N-acetylgalactosamine containing structures, and revealed 2,6-sialic acid-reactive motifs in two species. These findings establish N-glycosylation as an additional layer of molecular heterogeneity in Loxosceles venoms and provide a foundation for investigating its potential contribution to toxin properties and venom diversity.

biochemistry↗

bioRxiv2022

Validation of a colorimetric LAMP to detect Loxosceles experimental envenomation

Diagnostic tests for brown spider accidents are unavailable and impact treatment decisions, increasing costs and patient risks. In this work, we used for the first time a fast, simple, and visual method based on the loop-mediated isothermal amplification assay (LAMP) to detect Loxosceles envenomation. Using the DNA from L. similis legs, we observed a high sensitivity using this test since as low as 0.32 pg of DNA could be detected. This pH-dependent colorimetric assay was 64 times more sensitive than PCR to detect spider DNA. The test was specific for Loxosceles once no cross-reaction was observed when testing DNA from different agents that cause similar dermonecrotic injuries. The test allowed the detection of Loxosceles intermedia DNA from hair, serum, and swab samples obtained from experimentally-envenomed rabbit within 72 h. The method sensitivity varied according to the sample and the collection time, reaching 100% sensitivity in serum and hair, respectively, 1 h and 24 h after the experimental envenomation. Due to its ease of execution, speed, sensitivity, and specificity, LAMP presents an excellent potential for identifying Loxosceles spp. envenomation. This can reduce the burden on the Health System and the morbidity for the patient by implementing the appropriate therapy immediately.In addition, this work opens up the perspective to other venomous animal accident identification using LAMP. Highlights* Using 28S primers it was possible to identify L. similis DNA with high sensitivity; * LAMP was 62-fold more sensitive than PCR and detected as low as 0.32 pg of DNA; * LAMP detected L. intermedia DNA from hair, serum, and exudate from experimentally-envenomed rabbits; * LAMP presents an excellent potential for identifying Loxosceles spp. envenomation.

molecular biology↗

bioRxiv2020

Reduced competence to arboviruses following the sustainable invasion of Wolbachia into native Aedes aegypti from Niteroi, Southeastern Brazil

Field release of Wolbachia-infected Aedes aegypti has emerged as a promising solution to manage the transmission of dengue, Zika and chikungunya in endemic areas across the globe. Through an efficient self-dispersing mechanism, and the ability to induce virus-blocking properties, Wolbachia offers an unmatched potential to gradually modify wild Ae. aegypti populations turning them unsuitable disease vectors. Here in this work, a proof-of-concept field trial was carried out in a small community of Niteroi, greater Rio de Janeiro. Following the release of Wolbachia-infected eggs, we reported a successful invasion and long-term establishment of the bacterium across the territory, as denoted by stable high-infection indexes (>80%). We have also demonstrated that refractoriness to dengue and Zika viruses, either thorough oral-feeding or intra-thoracic saliva challenging assays, were maintained over the adaptation to the natural environment of Southeastern Brazil. These findings further support Wolbachias ability to invade local Ae. aegypti populations and impair disease transmission, and shall pave the way for future epidemiological and economic impact assessments.

microbiology↗

bioRxiv2019

Vector competence of Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus mosquitoes for Mayaro virus

Newly emerging or re-emerging arthropod-borne viruses (arboviruses) are important causes of human morbidity and mortality nearly worldwide. Arboviruses such as Dengue (DENV), Zika (ZIKV), Chikungunya (CHIKV) and West Nile virus (WNV) underwent an extensive geographic expansion in the tropical and sub-tropical regions of the world. In the Americas the main vectors, for DENV, ZIKV and CHIKV, are mosquito species adapted to urban environments namely Aedes aegypti and Aedes albopictus, whereas the main vector for WNV is the Culex quinquefasciatus. Given the widespread distribution in the Americas and high permissiveness to arbovirus infection, theses mosquito species might pose an important role in the epidemiology of other arboviruses normally associated to sylvatic vectors. Here, we test this hypothesis by determining the vector competence of Ae. aegypti, Ae. albopictus and Cx. quinquefasciatus to Mayaro (MAYV) virus, a sylvatic arbovirus transmitted mainly by Haemagogus janthinomys that have been causing an increasing number of outbreaks in South America namely in Brazil. Using field mosquitoes from Brazil, female mosquitoes were experimentally infected and their competence for dissemination and transmission for MAYV was evaluated. We found high dissemination rate for MAYV in Ae. aegypti (57.5%) and Ae. albopictus (61.6%), whereas very low rates were obtained for Cx. quinquefasciatus (2.5%). Concordantly, we observed that Ae. aegypti and Ae. albopictus have high transmission ability (69.5% and 71.1% respectively), conversely to Cx. quinquefasciatus that is not able to transmit the MAYV. Notably, we found that very low quantities of virus present in the saliva (undetectable by RT-qPCR) were sufficient and virulent enough to guarantee transmission. Although Ae. aegypti and Ae. albopictus mosquitoes are not the main vectors for MAYV, our studies suggest that these vectors may play a significant role in the transmission of this arbovirus, since both species showed high vector competence in laboratory conditions.\n\nAuthor summaryThe present study showed that Ae. aegypti and Ae. albopictus mosquitoes have high vector competence for MAYV, in laboratory. In contrast, Cx. quinquefasciatus mosquitoes were shown to be refractory to MAYV. Regarding the viral dilution and nanoinjection, higher detection sensitivity was observed after virus nanoinjection into naive mosquitoes, indicating that only a few viral particles are required to infect mosquitoes, and these particles may not be detected by RT-qPCR before the nanoinjection procedure.

microbiology↗